Form 486BPOS CALAMOS CONVERTIBLE OPPO

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As filed with the Securities and Exchange Commission on February 21, 2020

1933 Act File No. 333-229042

1940 Act File No. 811-21080

U.S. SECURITIES AND EXCHANGE
COMMISSION

Washington, D.C. 20549

Form N-2

(Check appropriate box or boxes)

REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933

Pre-Effective Amendment No.

Post-Effective Amendment No.     2

and

REGISTRATION STATEMENT UNDER THE INVESTMENT COMPANY ACT OF 1940

CALAMOS CONVERTIBLE OPPORTUNITIES

AND INCOME FUND

2020 Calamos
Court

Naperville, Illinois 60563

(630) 245-7200

Agent for
Service

John P. Calamos, Sr.

President

Calamos Convertible Opportunities and Income Fund

2020 Calamos Court

Naperville, Illinois 60563

Copies of
Communications to:

Paulita A. Pike

Ropes & Gray LLP

191 North Wacker Drive,

32nd Floor

Chicago, Illinois 60606

Jeremy Smith

Ropes & Gray LLP

1211 Avenue of the Americas

New York, New York 10036

Approximate Date of Proposed Public Offering: From time to time after the effective date of the Registration
Statement.

If any of the securities being registered on this form will be offered on a delayed or continuous basis in reliance on Rule 415 under the Securities Act
of 1933, other than securities offered in connection with a dividend reinvestment plan, check the following box. ☑

It is proposed that
this filing will become effective (check appropriate box)

when declared effective pursuant to section 8(c)

on February 28, 2020 pursuant to Rule 486(b) as applied by no-action relief granted to Registrant
on February 14, 2011

Base Prospectus

$100,000,000

Calamos Convertible Opportunities and Income

Fund

Common Shares

Preferred Shares

Debt Securities

Calamos Convertible Opportunities and Income Fund (the “Fund,” “we,” “us,” or “our”) is a diversified, closed-end management investment company that
commenced investment operations in June 2002. Our investment objective is to provide total return through a combination of capital appreciation and current income.

We may offer, on an immediate, continuous or delayed basis, up to $100,000,000 aggregate initial offering price of our common shares (no par value per share), preferred shares (no par value per share) or
debt securities, which we refer to in this prospectus collectively as our securities, in one or more offerings. We may offer our common shares, preferred shares and debt securities separately or together, in amounts, at prices and on terms set forth
in a prospectus supplement to this prospectus. You should read this prospectus and the related prospectus supplement carefully before you decide to invest in any of our securities.

We may offer our securities directly to one or more purchasers, through agents that we or they designate from time to time, or to or
through underwriters or dealers. The prospectus supplement relating to the particular offering will identify any agents or underwriters involved in the sale of our securities, and will set forth any applicable purchase price, fee, commission or
discount arrangement between us and such agents or underwriters or among the underwriters and the basis upon which such amount may be calculated. For more information about the manner in which we may offer our securities, see “Plan of
Distribution.” Our securities may not be sold through agents, underwriters or dealers without delivery or deemed delivery of a prospectus supplement and a prospectus.

Our common shares are listed on the Nasdaq Global Select Market under the symbol “CHI.” As of January 31, 2020, the last reported sale price for our common shares was $11.13 per share. As
of January 31, 2020, the last reported net asset value for our common shares was $11.30 per share.

Investing in our
securities involves certain risks, including the risks associated with the Fund’s use of leverage. You could lose some or all of your investment. See “Risk Factors” beginning on page 40 of this
prospectus. Shares of closed-end investment companies frequently trade at a discount to their net asset value and this may increase the risk of loss to purchasers of our securities. You should consider carefully these risks together with
all of the other information contained in this prospectus and any prospectus supplement before making a decision to purchase our securities.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or determined if this prospectus is truthful or complete. Any
representation to the contrary is a criminal offense.

Beginning on January 1, 2021, as permitted by
regulations adopted by the Securities and Exchange Commission, paper copies of the Fund’s shareholder reports will no longer be sent by mail, unless you specifically request paper copies of the reports from the Fund or from your financial
intermediary. Instead, the reports will be made available on a website, and you will be notified by mail each time a report is posted and provided with a website link to access the report.

If you already elected to receive shareholder reports electronically, you will not be affected by this change and you need not take any
action. You may elect to receive shareholder reports and other communications from the Fund electronically by calling 800.582.6959. If you own these shares through a financial intermediary, you may contact your financial intermediary.

You may elect to receive all future reports in paper free of charge. You can inform the
Fund that you wish to continue receiving paper copies of your shareholder reports by calling 800.582.6959. If you own these shares through a financial intermediary, you may contact your financial intermediary or follow instructions included with
this disclosure to elect to continue to receive paper copies of your shareholder reports. Your election to receive reports in paper will apply to all funds held with the fund complex or your financial intermediary.

Prospectus dated February 28, 2020

This prospectus, together with any accompanying prospectus supplement, sets forth concisely the information that you should know before investing. You should read the prospectus and prospectus supplement,
which contain important information, before deciding whether to invest in our securities. You should retain the prospectus and prospectus supplement for future reference. A statement of additional information, dated the same date as this prospectus,
as supplemented from time to time, containing additional information, has been filed with the Securities and Exchange Commission (“SEC” or the “Commission”) and is incorporated by reference in its entirety into this prospectus.
You may request a free copy of the statement of additional information, the table of contents of which is on page 85 of this prospectus, request a free copy of our annual and semi-annual reports, request other information or make shareholder
inquiries, by calling toll-free 800.582.6959 or by writing to the Fund at 2020 Calamos Court, Naperville, Illinois 60563. The Fund’s annual and semi-annual reports also are available on our website, free of charge, at www.calamos.com,
which also provides a link to the Commission’s website, as described below, where the Fund’s statement of additional information can be obtained. Information included on our website does not form part of this prospectus. You can review
documents we have filed on the Commission’s website (http://www.sec.gov) for free. You may also e-mail requests for these documents to publicinfo@sec.gov.

Our securities do not represent a deposit or obligation of, and are not guaranteed or endorsed by, any bank or other insured depository institution and are not federally insured by the Federal Deposit
Insurance Corporation, the Federal Reserve Board or any other government agency.

TABLE OF CONTENTS

You should rely only on the information contained or incorporated by reference in this
prospectus and any related prospectus supplement in making your investment decisions. We have not authorized any other person to provide you with different or inconsistent information. If anyone provides you with different or inconsistent
information, you should not rely on it. This prospectus and any prospectus supplement do not constitute an offer to sell or solicitation of an offer to buy any securities in any jurisdiction where the offer or sale is not permitted. The information
appearing in this prospectus and in any prospectus supplement is accurate only as of the dates on their covers. Our business, financial condition and prospects may have changed since such dates. We will advise you of any material changes to the
extent required by applicable law.

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CAUTIONARY NOTICE REGARDING FORWARD-LOOKING STATEMENTS

This prospectus, any accompanying prospectus supplement and the statement of additional information contain “forward-looking
statements.” Forward-looking statements can be identified by the words “may,” “will,” “intend,” “expect,” “estimate,” “continue,” “plan,” “anticipate,” and similar
terms and the negative of such terms. Such forward-looking statements may be contained in this prospectus as well as in any accompanying prospectus supplement. By their nature, all forward-looking statements involve risks and uncertainties, and
actual results could differ materially from those contemplated by the forward-looking statements. Several factors that could materially affect our actual results are the performance of the portfolio of securities we hold, the price at which our
shares will trade in the public markets and other factors discussed in our periodic filings with the Commission. Currently known risk factors that could cause actual results to differ materially from our expectations include, but are not limited to,
the factors described in the “Risk Factors” section of this prospectus. We urge you to review carefully that section for a more detailed discussion of the risks of an investment in our securities.

Although we believe that the expectations expressed in our forward-looking statements are reasonable, actual results could differ
materially from those projected or assumed in our forward-looking statements. Our future financial condition and results of operations, as well as any forward-looking statements, are subject to change and are subject to inherent risks and
uncertainties, such as those disclosed in the “Risk Factors” section of this prospectus. All forward-looking statements contained or incorporated by reference in this prospectus or any accompanying prospectus supplement are made as of the
date of this prospectus or such accompanying prospectus supplement, as the case may be. Except for our ongoing obligations under the federal securities laws, we do not intend, and we undertake no obligation, to update any forward-looking statement.
The forward-looking statements contained in this prospectus, any accompanying prospectus supplement and the statement of additional information are excluded from the safe harbor protection provided by Section 27A of the Securities Act of 1933,
as amended (the “1933 Act”).

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PROSPECTUS SUMMARY

The following summary contains basic information about us and our securities. It is not complete and may not contain all of the
information you may want to consider before investing in the Fund. You should review the more detailed information contained in this prospectus and in any related prospectus supplement and in the statement of additional information, especially the
information set forth under the heading “Risk Factors” beginning on page 40 of this prospectus.

The Fund

The Fund is a diversified, closed-end management investment company. We commenced operations in June 2002
following our initial public offering. As of January 31, 2020, we had $1.19 billion of total managed assets, including $100 million of outstanding mandatory redeemable preferred shares (“MRP Shares” or “MRPS”) and
$31 million of outstanding borrowings under a liquidity agreement, plus additional structural leverage that amounted to approximately $254 million. Structural leverage refers to borrowings under the liquidity agreement in respect of which
the Fund’s interest payments are reduced or eliminated by the Fund’s securities lending activities. See “Leverage.” Our fiscal year ends on October 31. Our investment objective is to provide total return through a
combination of capital appreciation and current income.

Investment Adviser

Calamos Advisors LLC (the “Adviser” or “Calamos”) serves as our investment adviser. Calamos is responsible on a
day-to-day basis for investment of the Fund’s portfolio in accordance with its investment objective and policies. Calamos makes all investment decisions for the Fund and places purchase and sale orders for the Fund’s portfolio securities.
As of January 31, 2020, Calamos managed approximately $26.6 billion in assets of individuals and institutions. Calamos is a wholly-owned subsidiary of Calamos Investments LLC (“CILLC“). Calamos Asset Management, Inc. is the sole
manager of CILLC.

The Fund pays Calamos an annual management fee, payable monthly in arrears, for its investment management
services equal to 0.80% of the Fund’s average weekly managed assets. “Managed assets” means the total assets of the Fund (including any assets attributable to any leverage that may be outstanding) minus the sum of accrued liabilities
(other than debt representing financial leverage). “Net assets” does not include any assets attributable to any leverage that may be outstanding, or other debt representing financial leverage. See “Management of the Fund.”

The principal business address of the Adviser is 2020 Calamos Court, Naperville, Illinois 60563.

The Offering

We may
offer, from time to time, in one or more offerings or series, together or separately, up to $100,000,000 of our common shares, preferred shares or debt securities, which we refer to, collectively, as the “securities.” We may sell our
securities through underwriters or dealers, “at the market” to or through a market maker into an existing trading market or otherwise directly to one or more purchasers or through agents or through a combination of methods of sale. The
identities of such underwriters, dealers, market makers or agents, as the case may be, will be described in one or more supplements to this prospectus. The securities may be offered at prices and on terms to be described in one or more supplements
to this prospectus. In the event we offer common shares, the offering price per share of our common shares exclusive of any underwriting commissions or discounts will not be less than the net asset value per share of our common shares at the time we
make the offering except as permitted by applicable law. To the extent that the Fund issues common shares and current shareholders do not participate, those current shareholders may experience a dilution of their voting rights as new shares are
issued to the public. Depending on the facts, any issuance of new common shares may also have the effect of reducing any premium to per share net asset value at which the shares might trade and the market price at which the shares might trade.

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Currently, the Fund does not intend to offer any preferred shares or debt
securities (collectively, “senior securities”), but reserves the right to do so in the future.

We may offer our
securities directly to one or more purchasers, through agents that we or they designate from time to time, or to or through underwriters or dealers. The prospectus supplement relating to the relevant offering will identify any agents or underwriters
involved in the sale of our securities, and will set forth any applicable purchase price, fee, commission or discount arrangement between us and such agents or underwriters or among underwriters and the basis upon which such amount may be
calculated. See “Plan of Distribution.” Our securities may not be sold through agents, underwriters or dealers without delivery or deemed delivery of a prospectus and prospectus supplement describing the method and terms of the applicable
offering of our securities.

Use of Proceeds

Unless otherwise specified in a prospectus supplement, we currently intend to use the net proceeds from the sale of our securities primarily to invest in accordance with our investment objective and
policies within approximately three months of receipt of such proceeds. We may also use proceeds from the sale of our securities to retire all or a portion of any short-term debt we incur in pursuit of our investment objective and policies and
for working capital purposes, including the payment of interest and operating expenses, although there is currently no intent to issue securities primarily for these purposes.

Dividends and Distributions on Common Shares

The Fund intends to
distribute to common shareholders all or a portion of its net investment income monthly and net realized capital gains, if any, at least annually. On November 4, 2008, the Commission granted Calamos, on behalf of itself and certain closed-end
funds that it manages, including the Fund, or may manage in the future, an order granting an exemption from Section 19(b) of, and Rule 19b-1 under, the Investment Company Act of 1940, as amended (the “1940 Act”), to conditionally
permit the Fund to make periodic distributions of long-term capital gains with respect to the Fund’s outstanding common shares as frequently as twelve times each year, so long as it complies with the conditions of the order and maintains in
effect a distribution policy with respect to its common shares calling for periodic distributions of an amount equal to a fixed amount per share, a fixed percentage of market price per share or a fixed percentage of the Fund’s net asset value
per share (a “Managed Distribution Policy”). See “Dividends and Distributions on Common Shares; Automatic Dividend Reinvestment Plan — Dividends and Distributions on Common Shares” for a discussion of the requirements under
the order permitting the Managed Distribution Policy.

As of January 1, 2019-2020, the Fund adopted such Managed Distribution
Policy. Pursuant to such policy, the Fund currently intends to make monthly distributions to common shareholders stated in terms of a fixed cent per common share distribution rate that would be composed of, in addition to net investment income,
supplemental amounts generally representing realized capital gains or, possibly, returns of capital representing either unrealized capital gains or a return of original investment. Such distributions, including such supplemental amounts, are
sometimes referred to as “managed distributions.”

The Fund will seek to establish a distribution rate that roughly
corresponds to the Adviser’s projections of the total return that could reasonably be expected to be generated by the Fund over an extended period of time, although the distribution rate will not be solely dependent on the amount of income
earned or capital gains realized by the Fund. Calamos, in making such projections, may consider long-term historical returns and a variety of other factors. If, for any monthly distribution, net investment income and net realized capital gains were
less than the amount of the distribution, the difference would be distributed from the Fund’s assets. In addition, in order to make such distributions, the Fund might have to sell a portion of its investment portfolio at a time when independent
investment judgment might not dictate such action. The Fund’s final distribution for each calendar year will include any remaining net investment income undistributed during the year and may include any remaining net realized capital gains
undistributed during the year. The Fund’s actual financial performance

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will likely vary significantly from quarter to quarter and from year to year, and there
may be extended periods of up to several years when the distribution rate will exceed the Fund’s actual total returns. The Fund’s projected or actual distribution rate is not a prediction of what the Fund’s actual total returns will
be over any specific future period. See “Certain Federal Income Tax Matters — Federal Income Taxation of Common and Preferred Shareholders” and “Dividends and Distributions on Common Shares; Automatic Dividend Reinvestment Plan
— Dividends and Distributions on Common Shares” below for a discussion of the short- and long-term implications associated with Fund distributions.

As portfolio and market conditions change, the rate of distributions on the common shares and the Fund’s distribution policy could change. To the extent that the total return of the Fund exceeds the
distribution rate for an extended period, the Fund may be in a position to increase the distribution rate or distribute supplemental amounts to shareholders. Conversely, if the total return of the Fund is less than the distribution rate for an
extended period of time, the Fund will effectively be drawing upon its net assets to meet payments prescribed by its distribution policy. The rate may be modified by the Fund’s Board of Trustees from time to time without prior notice to the
Fund’s shareholders.

Net realized short-term capital gains distributed to shareholders will be taxed as ordinary
income for federal income tax purposes and net realized long-term capital gain (if any) will be taxed for federal income tax purposes at long-term capital gain rates. To the extent the Fund distributes an amount in excess of the Fund’s current
and accumulated earnings and profits, such excess, if any, will be treated by a shareholder for federal income tax purposes as a tax-free return of capital to the extent of the shareholder’s adjusted tax basis in their shares and thereafter as
a gain from the sale or exchange of such shares. Any such distributions made by the Fund will reduce the shareholder’s adjusted tax basis in their shares to the extent that the distribution constitutes a return of capital on a tax basis during
any calendar year and, thus, could potentially subject the shareholder to capital gains taxation in connection with a later sale of Fund shares, even if those shares are sold at a price that is lower than the shareholder’s original investment
price. To the extent that the Fund’s distributions exceed the Fund’s current and accumulated earnings and profits, the distribution payout rate will exceed the yield generated from the Fund’s investments. There is no guarantee that
the Fund will realize capital gain in any given year. Distributions are subject to re-characterization for federal income tax purposes after the end of the fiscal year. See “Certain Federal Income Tax Matters.”

Pursuant to the Fund’s Automatic Dividend Reinvestment Plan, unless a shareholder is ineligible or elects otherwise, all dividends
and capital gain distributions on common shares are automatically reinvested in additional common shares of the Fund. However, an investor can choose to receive dividends and distributions in cash. Since investors can participate in the automatic
dividend reinvestment plan only if their broker or nominee participates in our plan, you should contact your broker or nominee to confirm that you are eligible to participate in the plan. See “Dividends and Distributions on Common Shares;
Automatic Dividend Reinvestment Plan — Automatic Dividend Reinvestment Plan.”

Investment Policies

Primary Investments.    Under normal circumstances, the Fund invests at least 80% of its managed assets in a
diversified portfolio of convertible securities and non-convertible income securities. The portion of the Fund’s assets invested in convertible securities and non-convertible income securities will vary from time to time
consistent with the Fund’s investment objective, changes in equity prices and changes in interest rates and other economic and market factors, although, under normal circumstances, the Fund will invest at least 35% of its managed assets in
convertible securities. The Fund invests in securities with a broad range of maturities. The average term to maturity of the Fund’s securities typically will range from five to ten years. See “Investment Objective and Principal Investment
Strategies — Principal Investment Strategies.”

Convertible
Securities.    The Fund is not limited in the percentage of its assets invested in convertible securities, and investment in convertible securities forms an important part of the Fund’s principal investment strategies.

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Under normal circumstances, the Fund will invest at least 35% of its managed assets
in convertible securities. A convertible security is a debt security, debenture, note or preferred stock that may be converted into an equity security (typically common stock of the same issuer) at a predetermined price (the “conversion
price”). Depending upon the relationship of the conversion price to the market value of the underlying security, a convertible security may trade more like an equity security than a debt instrument. The Fund may invest in convertible securities
of any rating. See “Investment Objective and Principal Investment Strategies — Principal Investment Strategies — Convertible Securities.”

Synthetic Convertible Instruments.    The Fund may invest in “synthetic” convertible instruments. A synthetic convertible instrument is a financial instrument (or two
or more securities held in tandem) that is designed to simulate the economic characteristics of another instrument (i.e., a convertible security) through the combined economic features of a collection of other securities or assets. Calamos may
create a synthetic convertible instrument by combining separate securities that possess the two principal characteristics of a true convertible security, i.e., a fixed-income security (“fixed-income component”, which may be a convertible
or non-convertible security) and the right to acquire an equity security (“convertible component”). The fixed-income component is achieved by investing in fixed-income securities such as bonds, preferred stocks and money market
instruments. The convertible component is achieved by investing in warrants or options to buy common stock at a certain exercise price, or options on a stock index.

The Fund may also invest in synthetic convertible instruments created by third parties, typically investment banks. Synthetic convertible instruments created by such parties may be designed to simulate
the characteristics of traditional convertible securities or may be designed to alter or emphasize a particular feature. Traditional convertible securities typically offer the opportunity for stable cash flows with the ability to participate in
capital appreciation of the underlying common stock. Traditional convertible securities are exercisable at the option of the holder. Synthetic convertible instruments may alter these characteristics by offering enhanced yields in exchange for
reduced capital appreciation, additional risk of loss, or any combination of these features. Synthetic convertible instruments may include structured notes, equity-linked notes, mandatory convertibles and combinations of securities and instruments,
such as a debt instrument combined with a forward contract. The Fund’s holdings of synthetic convertible instruments are considered convertible securities for purposes of the Fund’s policy to invest at least 35% of its managed assets
in convertible securities and 80% of its managed assets in a diversified portfolio of convertible securities and non-convertible income securities. See “Investment Objective and Principal Investment Strategies — Principal
Investment Strategies — Synthetic Convertible Instruments.”

Non-Convertible Income
Securities.    The Fund will also invest in non-convertible income securities. The Fund’s investments in non-convertible income securities may have fixed or variable principal payments and all types
of interest rate and dividend payment and reset terms, including fixed rate, adjustable rate, zero coupon, contingent, deferred, payment in kind and auction rate features. See “Investment Objective and Principal Investment
Strategies — Principal Investment Strategies — Non-Convertible Income Securities.”

High Yield Securities.    A substantial portion of the Fund’s assets may be invested in below investment grade (high yield) securities for either current income or capital
appreciation or both. These securities are rated Ba or lower by Moody’s Investors Service, Inc. (“Moody’s”) or BB or lower by Standard & Poor’s Financial Services, LLC, a subsidiary of The McGraw-Hill Companies,
Inc. (“Standard & Poor’s”) or are unrated securities of comparable quality as determined by Calamos, the Fund’s investment adviser. The Fund may invest in high yield securities of any rating. The Fund may, but currently
does not intend to, invest up to 5% of its managed assets in distressed securities that are in default or the issuers of which are in bankruptcy. Non-convertible debt securities rated below investment grade are commonly referred to as “junk
bonds” and are considered speculative with respect to the issuer’s capacity to pay interest and repay principal. Below investment-grade securities involve greater risk of loss, are subject to greater price volatility and are less liquid,
especially during periods of economic uncertainty or change, than higher rated securities. See “Investment Objective and Principal Investment Strategies — Principal Investment Strategies — High Yield Securities.”

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Foreign Securities.    Although the Fund primarily invests
in securities of U.S. issuers, the Fund may invest up to 25% of its net assets in securities of foreign issuers in developed and emerging markets, including debt and equity securities of corporate issuers and debt securities of government issuers. A
foreign issuer is a foreign government or a company organized under the laws of a foreign country. See “Investment Objective and Principal Investment Strategies — Principal Investment Strategies — Foreign Securities.”

Options Writing.    The Fund may seek to generate income from option premiums by
writing (selling) options. The Fund may write (sell) call options (i) on a portion of the equity securities (including equity securities obtainable by the Fund through the exercise of its rights with respect to convertible securities it owns)
in the Fund’s portfolio and (ii) on broad-based securities indices (such as the Standard and Poor’s
500® Index (“S&P 500”) or the MSCI EAFE® Index (“MSCI EAFE”), which is an index of international equity stocks) or certain ETFs (exchange-traded funds) that trade like common stocks but seek
to replicate such market indices.

In addition, to seek to offset some of the risk of a potential decline in value of certain
long positions, the Fund may also purchase put options on individual securities, broad-based securities indices (such as the S&P 500 or the MSCI EAFE), or certain ETFs that trade like common stocks but seek to replicate such market indices.
See “Investment Objective and Principal Investment Strategies — Options Writing.”

Rule 144A
Securities.    The Fund may invest without limit in certain securities (“Rule 144A Securities”), such as convertible and debt securities, that are typically purchased in transactions exempt from the registration
requirements of the 1933 Act pursuant to Rule 144A under that Act. Rule 144A Securities may only be sold to qualified institutional buyers, such as the Fund. Any resale of these securities must generally be effected through a sale that is registered
under the 1933 Act or otherwise exempted or excepted from such registration requirements. Under the supervision and oversight of the Fund’s Board of Trustees, Calamos will determine whether Rule 144A Securities are liquid. Typically, the Fund
purchases Rule 144A Securities only if Calamos has determined them to be liquid. If any Rule 144A Security held by the Fund should become illiquid, the value of the security may be reduced and a sale of the security may be more difficult. See
“Investment Objective and Principal Investment Strategies — Principal Investment Strategies — Rule 144A Securities.”

Loans.    The Fund may invest in loan participations and other direct claims against a borrower. The corporate loans in which the Fund may invest primarily consist of direct
obligations of a borrower and may include debtor in possession financings pursuant to Chapter 11 of the U.S. Bankruptcy Code, obligations of a borrower issued in connection with a restructuring pursuant to Chapter 11 of the U.S. Bankruptcy Code,
leveraged buy-out loans, leveraged recapitalization loans, receivables purchase facilities, and privately placed notes. The Fund may invest in a corporate loan at origination as a co-lender or by acquiring in the secondary market participations in,
assignments of or novations of a corporate loan. By purchasing a participation, the Fund acquires some or all of the interest of a bank or other lending institution in a loan to a corporate or government borrower. The participations typically will
result in the Fund having a contractual relationship only with the lender not the borrower. The Fund will have the right to receive payments of principal, interest and any fees to which it is entitled only from the lender selling the participation
and only upon receipt by the lender of the payments from the borrower. Many such loans are secured, although some may be unsecured. Such loans may be in default at the time of purchase. Loans that are fully secured offer the Fund more protection
than an unsecured loan in the event of non-payment of scheduled interest or principal. However, there is no assurance that the liquidation of collateral from a secured loan would satisfy the corporate borrower’s obligation, or that the
collateral can be liquidated. Direct debt instruments may involve a risk of loss in case of default or insolvency of the borrower and may offer less legal protection to the Fund in the event of fraud or misrepresentation. In addition, loan
participations involve a risk of insolvency of the lending bank or other financial intermediary. The markets in such loans are not regulated by federal securities laws or the Commission.

Other Securities.    The Fund may invest in other securities of various types to the extent consistent with its
investment objective. Normally, the Fund invests substantially all of its assets to meet its investment objective. For temporary defensive purposes, the Fund may depart from its principal investment strategies and invest part or all of its assets in
securities with remaining maturities of less than one year or cash equivalents; or it may hold

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cash. During such periods, the Fund may not be able to achieve its investment objective. There are no restrictions as to the ratings of debt securities acquired by the Fund or the portion of the
Fund’s assets that may be invested in debt securities in a particular ratings category. For more information on the types of derivatives that the Fund invests in, see “Investment Objective and Principal Investment Strategies —
Principal Investment Strategies” in this prospectus and “Investment Objective and Policies” in the statement of additional information.

Use of Leverage by the Fund

The Fund currently uses, and may in the
future use, financial leverage. The Fund has obtained financial leverage (i) under an Amended and Restated Liquidity Agreement (the “SSB Agreement”) with State Street Bank and Trust Company (“SSB” or “State
Street”) that allows the Fund to borrow up to $430 million and (ii) through the issuance of three series of MRP Shares with an aggregate liquidation preference of $100 million, as described in greater detail below. The SSB Agreement
provides for securities lending and securities repurchase transactions that may offset some of the interest rate payments that would otherwise be due in respect of the borrowings under the SSB Agreement. The Fund’s outstanding MRP Shares
include 1,330,000 Series A MRP Shares, with an aggregate liquidation preference of $33,250,000 and a mandatory redemption date of September 6, 2022; 1,330,000 Series B MRP Shares, with an aggregate liquidation preference of $33,250,000 and a
mandatory redemption date of September 6, 2024; and 1,340,000 Series C MRP Shares, with an aggregate liquidation preference of $33,500,000 and a mandatory redemption date of September 6, 2027. The Series A, Series B and Series C MRP Shares
are to pay monthly cash dividends initially at rates of 3.70%, 4.00% and 4.24%, respectively, subject to adjustment under certain circumstances. Additional details regarding the SSB Agreement and the MRP Shares are included under
“Leverage.”

As of January 31, 2020, the Fund had utilized $285 million of the $430 million available
under the SSB Agreement ($31 million in borrowings outstanding, and $254 million in structural leverage consisting of collateral received from SSB in connection with securities on loan), representing 24.0% of managed assets as of that
date, and had $100 million of MRP Shares outstanding, representing 8.4% of managed assets. Combined, the borrowings under the SSB Agreement and the outstanding MRP Shares represented 32.5% of managed assets.

The Fund may make further use of financial leverage through the issuance of additional preferred shares or may borrow money or issue
additional debt securities to the extent permitted under the 1940 Act or under the SSB Agreement. As a non-fundamental policy, the Fund may not issue preferred shares or borrow money and/or issue debt securities with an aggregate liquidation
preference and aggregate principal amount exceeding 38% of the Fund’s managed assets measured at the time of borrowing or issuance of the new securities. However, the Board of Trustees reserves the right to issue preferred shares or debt
securities or borrow to the extent permitted by the 1940 Act. See “Leverage.” The holders of preferred shares or debt, if any, on the one hand, and the holders of the common shares, on the other, may have interests that conflict with each
other in certain situations. See “Description of Securities — Preferred Shares” and “Certain Provisions of the Agreement and Declaration of Trust and By-Laws, Including Antitakeover Provisions.”

Because Calamos’ investment management fee is a percentage of the Fund’s managed assets, Calamos’ fee will be higher if the
Fund is leveraged and Calamos will have an incentive to be more aggressive and leverage the Fund. Consequently, the Fund and Calamos may have differing interests in determining whether to leverage the Fund’s assets. Any additional use of
leverage by the Fund effected through new, additional or increased credit facilities or the issuance of preferred shares would require approval by the Board of Trustees of the Fund. In considering whether to approve the use of additional leverage
through those means, the Board would be presented with all relevant information necessary to make a determination whether or not additional leverage would be in the best interests of the Fund, including information regarding any potential conflicts
of interest. For further information about the Fund’s financial leverage, see “Use of Leverage by the Fund.”

For further information about the effects of the Fund’s financial leverage and an illustration of the hypothetical effect on the
return to a holder of the Fund’s common shares of the leverage obtained by borrowing

6

under the Fund’s financing package, see “Effects of Leverage.” For further information about leveraging, see “Risk Factors — Fund Risks — Leverage Risk.”

Interest Rate Transactions

In order to seek to reduce the interest rate risk inherent in the Fund’s underlying investments and capital structure, the Fund, if Calamos deems market conditions favorable, may enter
into over-the-counter interest rate swap, cap or floor transactions to attempt to protect itself from increasing dividend or interest expenses on its leverage. The use of interest rate swaps and caps is a highly specialized activity that
involves investment techniques and risks different from those associated with ordinary portfolio security transactions.

In an interest rate swap, the Fund would agree to pay to the other party to the interest rate swap (which is known as the
“counterparty”) a fixed rate payment in exchange for the counterparty agreeing to pay to the Fund a payment at a variable rate that is expected to approximate the rate on any variable rate payment obligation on the Fund’s leverage.
The payment obligations would be based on the notional amount of the swap.

In an interest rate cap, the Fund would pay a
premium to the counterparty to the interest rate cap and, to the extent that a specified variable rate index exceeds a predetermined fixed rate, would receive from the counterparty payments of the difference based on the notional amount of such cap.
There can be no assurance that the Fund will use interest rate transactions or that, if used, their use will be beneficial to the Fund. Depending on the state of interest rates in general, the Fund’s use of interest rate swap or cap
transactions could enhance or harm the overall performance of the common shares. See “Interest Rate Transactions.”

Conflicts of
Interest

Conflicts of interest may arise from the fact that Calamos and its affiliates carry on substantial investment
activities for other clients, in which the Fund does not have an interest. Calamos or its affiliates may have financial incentives to favor certain of such accounts over the Fund. Any of their proprietary accounts or other customer accounts may
compete with the Fund for specific trades. Calamos or its affiliates may give advice and recommend securities to, or buy or sell securities for, other accounts and customers, which advice or securities recommended may differ from advice given to, or
securities recommended or bought or sold for, the Fund, even though their investment objectives may be the same as, or similar to, the Fund’s investment objective.

Situations may occur when the Fund could be disadvantaged because of the investment activities conducted by Calamos and its affiliates for their other accounts. Such situations may be based on, among
other things, the following: (1) legal or internal restrictions on the combined size of positions that may be taken for the Fund or the other accounts, thereby limiting the size of the Fund’s position; (2) the difficulty of
liquidating an investment for the Fund or the other accounts where the market cannot absorb the sale of the combined position; or (3) limits on co-investing in negotiated transactions under the 1940 Act. See “Investment Objective and
Principal Investment Strategies — Conflicts of Interest.”

Fund Risks

The principal risks are presented in alphabetical order to facilitate finding particular risks and comparing them with other funds. Each
risk summarized below is considered a “principal risk” of investing in the Fund, regardless of the order in which it appears.

Antitakeover Provisions.    The Fund’s Agreement and Declaration of Trust and By-Laws include provisions that could limit the ability of other entities or persons to
acquire control of the Fund or to change the composition of its Board of Trustees. Such provisions could limit the ability of shareholders to sell their shares at a premium over prevailing market prices by discouraging a third party from seeking to
obtain control of the Fund. These provisions include staggered terms of office for the Trustees, advance notice requirements for shareholder proposals, and super-majority voting requirements for certain transactions with affiliates, converting the
Fund to

7

an open-end investment company or a merger, asset sale or similar transaction. Holders of preferred shares have voting rights in addition to and separate from the voting rights of common
shareholders with respect to certain of these matters. Holders of any preferred shares, voting separately as a single class, have the right to elect at least two Trustees at all times. See “Description of Securities — Preferred
Shares” and “Certain Provisions of the Agreement and Declaration of Trust and By-Laws, Including Antitakeover Provisions.” The holders of preferred shares or debt, if any, on the one hand, and the holders of the common shares, on the
other, may have interests that conflict with each other in certain situations, including conflicts that relate to the fees and expenses of the Fund. For more information on potential conflicts of interest between holders of common shares and holders
of preferred shares, see “Fund Risks — Leverage Risk.” See also “Risk Factors — Fund Risks — Antitakeover Provisions.”

Convertible Securities Risk.    The value of a convertible security is influenced by both the yield of non-convertible securities of comparable issuers and by the
value of the underlying common stock. The value of a convertible security viewed without regard to its conversion feature (i.e., strictly on the basis of its yield) is sometimes referred to as its “investment value.” A convertible
security’s investment value tends to decline as prevailing interest rate levels increase. Conversely, a convertible security’s investment value tends to increase as prevailing interest rate levels decline.

However, a convertible security’s market value tends to reflect the market price of the common stock of the issuing company when that
stock price is greater than the convertible security’s “conversion price.” The conversion price is defined as the predetermined price at which the convertible security could be exchanged for the associated stock. As the market price
of the underlying common stock declines, the price of the convertible security tends to be influenced more by the yield of the convertible security and changes in interest rates. Thus, the convertible security may not decline in price to the same
extent as the underlying common stock. In the event of a liquidation of the issuing company, holders of convertible securities would be paid before the company’s common stockholders. See “Risk
Factors — Fund Risks — Convertible Securities Risk.”

Counterparty and Settlement
Risk.     Trading options, futures contracts, swaps and other derivative financial instruments entails credit risk with respect to the counterparties. Such instruments when traded over the counter do not include the same
protections as may apply to trading derivatives on organized exchanges. Substantial losses may arise from the insolvency, bankruptcy or default of a counterparty and risk of settlement default of parties with whom it trades securities. This risk may
be heightened during volatile market conditions. Settlement mechanisms in emerging markets are generally less developed and reliable than those in more developed countries, thus increasing the risks. In the past, broker-dealers and other financial
institutions have experienced extreme financial difficulty, sometimes resulting in bankruptcy of the institution. Although Calamos monitors the creditworthiness of the Fund’s counterparties, there can be no assurance that the Fund’s
counterparties will not experience similar difficulties, possibly resulting in losses to the Fund. If a counterparty becomes bankrupt, or otherwise fails to perform its obligations under a derivative contract due to financial difficulties, the Fund
may experience significant delays in obtaining any recovery under the derivative contract in a bankruptcy or other reorganization proceeding. The Fund may obtain only a limited recovery or may obtain no recovery in such circumstances. Material
exposure to a single or small group of counterparties increases the Fund’s counterparty risk. See “Risk Factors — Fund Risks — Counterparty and Settlement Risk.”

Credit Risk.    An issuer of a fixed income security could be downgraded or default. If the Fund holds
securities that have been downgraded, or that default on payment, the Fund’s performance could be negatively affected.

Cybersecurity Risk.    Investment companies, such as the Fund, and their service providers are exposed to
operational and information security risks resulting from cyberattacks, which may result in financial losses to a fund and its shareholders. Cyber-attacks include, among other behaviors, stealing or corrupting data maintained online or digitally,
denial of service attacks on websites, “ransomware” that renders systems inoperable until ransom is paid, the unauthorized release of confidential information, or various other forms of cybersecurity

8

breaches. Cyber-attacks affecting the Fund or the Adviser, custodian, transfer agent, distributor, administrator, intermediaries, trading counterparties, and other third-party service providers
may adversely impact the Fund or the companies in which the Fund invests, causing the Fund’s investments to lose value or to prevent a shareholder redemption or purchase from clearing in a timely manner.

Debt Securities Risk.    The Fund may invest in debt securities, including corporate bonds and high yield
securities. In addition to the risks described elsewhere in this prospectus (such as high yield securities risk and interest rate risk), debt securities are subject to certain additional risks, including issuer risk and reinvestment risk. Issuer
risk is the risk that the value of debt securities may decline for a number of reasons which directly relate to the issuer, such as management performance, leverage and reduced demand for the issuer’s goods and services. Reinvestment risk is
the risk that income from the Fund’s portfolio will decline if the Fund invests the proceeds from matured, traded or called bonds at market interest rates that are below the Fund portfolio’s current earnings rate. A decline in income could
affect the market price of the Fund’s common shares or the overall return of the Fund.

Default
Risk.    Default risk refers to the risk that a company that issues a convertible or debt security will be unable to fulfill its obligations to repay principal and interest. The lower a debt security is rated, the greater its
default risk. The Fund may incur cost and delays in enforcing its rights against the defaulting issuer. See “Risk Factors — Fund Risks — Default Risk.”

Derivatives Risk.    Generally, derivatives are financial contracts whose value depends on, or is derived from, the value of an underlying asset, reference rate or index, and
may relate to individual debt or equity instruments, interest rates, currencies or currency exchange rates, commodities, related indices and other assets. The Fund may utilize a variety of derivative instruments including, but not limited to,
interest rate swaps, convertible securities, synthetic convertible instruments, options on individual securities, index options, long calls, covered calls, long puts, cash-secured short puts and protective puts for hedging, risk management and
investment purposes. The Fund’s use of derivative instruments involves investment risks and transaction costs to which the Fund would not be subject absent the use of these instruments and, accordingly, may result in losses greater than if they
had not been used. The use of derivative instruments may have risks including, among others, leverage risk, volatility risk, duration mismatch risk, correlation risk, liquidity risk, interest rate risk, credit risk, management risk and counterparty
risk. Derivatives also involve the risk of mispricing or improper valuation and the risk that changes in the value of a derivative may not correlate perfectly with an underlying asset, interest rate or index. Suitable derivative transactions may not
be available in all circumstances and there can be no assurance that the Fund will engage in these transactions to reduce exposure to other risks when that would be beneficial. Furthermore, the skills needed to employ derivatives strategies are
different from those needed to select portfolio securities and, in connection with such strategies, the Fund makes predictions with respect to market conditions, liquidity, currency movements, market values, interest rates and other applicable
factors, which may be inaccurate. Thus, the use of derivative investments may require the Fund to sell or purchase portfolio securities at inopportune times or for prices below or above the current market values, may limit the amount of appreciation
the Fund can realize on an investment or may cause the Fund to hold a security that it might otherwise want to sell. Tax rules governing the Fund’s transactions in derivative instruments may also affect whether gains and losses recognized by
the Fund are treated as ordinary or capital, accelerate the recognition of income or gains to the Fund, defer losses to the Fund, and cause adjustments in the holding periods of the Fund’s securities, thereby affecting, among other things,
whether capital gains and losses are treated as short-term or long-term. These rules could therefore affect the amount, timing and/or character of distributions to shareholders. In addition, there may be situations in which the Fund elects not to
use derivative investments that result in losses greater than if they had been used.

Amounts paid by the Fund as premiums and
cash or other assets held in margin accounts with respect to the Fund’s derivative instruments would not be available to the Fund for other investment purposes, which may result in lost opportunities for gain.

9

Derivative instruments can be illiquid, may disproportionately increase losses and
may have a potentially large impact on Fund performance. See “Risk Factors — Fund Risks — Derivatives Risk” for a more complete discussion of the risks associated with derivatives transactions.

Emerging Markets Risk.    Emerging market countries may have relatively unstable governments and economies
based on only a few industries, which may cause greater instability. The value of emerging market securities will likely be particularly sensitive to changes in the economies of such countries. These countries are also more likely to experience
higher levels of inflation, deflation or currency devaluations, which could adversely affect the value of the Fund’s investments and hurt those countries’ economies and securities markets. See “Risk Factors — Fund Risks —
Emerging Markets Risk.”

Foreign Securities Risk.    Investments in non-U.S. issuers may
involve unique risks compared to investing in securities of U.S. issuers. These risks are more pronounced to the extent that the Fund invests a significant portion of its non-U.S investments in one region or in the securities of emerging market
issuers. See also “— Emerging Markets Risk” below. These risks may include:

less information may be available about non-U.S. issuers or markets due to less rigorous disclosure or accounting standards or regulatory practices in
foreign jurisdictions;

many non-U.S. markets are smaller, less liquid and more volatile. In a changing market, Calamos may not be able to sell the Fund’s portfolio
securities at times, in amounts and at prices it considers reasonable;

an adverse effect of currency exchange rate changes or controls on the value of the Fund’s investments;

the economies of non-U.S. countries may grow at slower rates than expected or may experience a downturn or recession;

economic, political and social developments may adversely affect the securities markets in foreign jurisdictions, including expropriation and
nationalization;

the difficulty in obtaining or enforcing a court judgment in non-U.S. countries;

restrictions on foreign investments in non-U.S. jurisdictions;

difficulties in effecting the repatriation of capital invested in non-U.S. countries;

withholding and other non-U.S. taxes may decrease the Fund’s return; and

dividend income the Fund receives from foreign securities may not be eligible for the special tax treatment applicable to qualified dividend income.

Based upon the Fund’s test for determining whether an issuer is a “foreign issuer” as
described above, it is possible that an issuer of securities in which the Fund invests could be organized under the laws of a foreign country, yet still conduct a substantial portion of its business in the U.S. or have substantial assets in the U.S.
In this case, such a “foreign issuer” may be subject to the market conditions in the U.S. to a greater extent than it may be subject to the market conditions in the country of its organization. See “Risk Factors — Fund Risks
— Foreign Securities Risk.” See also “— Non-U.S. Government Obligation Risk.”

High Yield
Securities Risk.    The Fund may invest in high yield securities of any rating. Investment in high yield securities involves substantial risk of loss. Below investment grade non-convertible debt securities or
comparable unrated securities are commonly referred to as “junk bonds” and are considered predominantly speculative with respect to the issuer’s ability to pay interest and principal and are susceptible to default or decline in market
value due to adverse economic and business developments. The market values for high yield securities tend to be very volatile, and these securities are less liquid than investment grade debt securities. For these reasons, your investment in the Fund
is subject to the following specific risks:

increased price sensitivity to changing interest rates and to a deteriorating economic environment;

greater risk of loss due to default or declining credit quality;

10

adverse company specific events are more likely to render the issuer unable to make interest and/or principal payments; and

if a negative perception of the high yield market develops, the price and liquidity of high yield securities may be depressed. This negative perception
could last for a significant period of time.

Adverse changes in economic conditions are more likely to lead
to a weakened capacity of a high yield issuer to make principal payments and interest payments than an investment grade issuer. The principal amount of high yield securities outstanding has proliferated in the past decade as an increasing number of
issuers have used high yield securities for corporate financing. An economic downturn could severely affect the ability of highly leveraged issuers to service their debt obligations or to repay their obligations upon maturity.

The secondary market for high yield securities may not be as liquid as the secondary market for more highly rated securities, a factor
which may have an adverse effect on the Fund’s ability to dispose of a particular security. There are fewer dealers in the market for high yield securities than for investment grade obligations. The prices quoted by different dealers may vary
significantly and the spread between the bid and asked price is generally much larger than for higher quality instruments. See “Risk Factors — Fund Risks — High Yield Securities Risk.”

Interest Rate Risk.    In addition to the risks discussed above, debt securities, including high yield
securities, are subject to certain risks, including:

if interest rates go up, the value of debt securities in the Fund’s portfolio generally will decline;

during periods of declining interest rates, the issuer of a security may exercise its option to prepay principal earlier than scheduled, forcing the
Fund to reinvest in lower yielding securities. This is known as call or prepayment risk. Debt securities frequently have call features that allow the issuer to repurchase the security prior to its stated maturity. An issuer may redeem an obligation
if the issuer can refinance the debt at a lower cost due to declining interest rates or an improvement in the credit standing of the issuer;

during periods of rising interest rates, the average life of certain types of securities may be extended because of slower than expected principal
payments. This may lock in a below market interest rate, increase the estimated period until the security is paid in full, and reduce the value of the security. This is known as extension risk;

rising interest rates could result in an increase in the cost of the Fund’s leverage and could adversely affect the ability of the Fund to meet
asset coverage requirements with respect to leverage;

variable rate securities generally are less sensitive to interest rate changes but may decline in value if their interest rates do not rise as much, or
as quickly, as interest rates in general. When the Fund holds variable rate securities, a decrease in market interest rates will adversely affect the income received from such securities and the net asset value (“NAV”) of the Fund’s
shares; and

the risks associated with rising interest rates may be particularly acute in the current market environment because market interest rates are currently
near historically low levels. Thus, the Fund currently faces a heightened level of interest rate risk, especially since the Federal Reserve Board has ended its quantitative easing program and has begun, and may continue, to raise interest rates. To
the extent the Federal Reserve Board continues to raise interest rates, there is a risk that interest rates across the financial system may rise. Increases in volatility and interest rates in the fixed-income market may expose the Fund to heightened
interest rate risk.

Many financial instruments use or may use a floating rate based on LIBOR, which is the
offered rate for short-term Eurodollar deposits between major international banks. On July 27, 2019-2020, the head of the United Kingdom’s Financial Conduct Authority announced a desire to phase out the use of LIBOR by the end of 2021.

11

There remains uncertainty regarding the future utilization of LIBOR and the nature of any replacement rate. As such, the potential effect of a transition away from LIBOR on the Fund or the
financial instruments in which the Fund invests cannot yet be determined. See “Risk Factors — Fund Risks — Interest Rate Risk.”

Leverage Risk.    The Fund has issued indebtedness and preferred shares and may borrow money or issue debt securities as permitted by the 1940 Act. As of January 31, 2020,
the Fund has leverage in the form of borrowings under the SSB Agreement and outstanding MRP Shares. Leverage is the potential for the Fund to participate in gains and losses on an amount that exceeds the Fund’s investment. The borrowing of
money or issuance of debt securities and preferred shares represents the leveraging of the Fund’s common shares. As a non-fundamental policy, the Fund may not issue preferred shares or borrow money and/or issue debt securities with an aggregate
liquidation preference and aggregate principal amount exceeding 38% of the Fund’s managed assets as measured at the time of borrowing or issuance of the new securities. However, the Board of Trustees reserves the right to issue preferred shares
or debt securities or borrow to the extent permitted by the 1940 Act and the Fund’s policies. See “Leverage.”

Leverage creates risks which may adversely affect the return for the holders of common shares, including:

the likelihood of greater volatility in the net asset value and market price of the Fund’s common shares;

fluctuations in the dividend rates on any preferred shares borne by the Fund or in interest rates on borrowings and short-term debt;

increased operating costs, which are effectively borne by common shareholders, may reduce the Fund’s total return; and

the potential for a decline in the value of an investment acquired with borrowed funds, while the Fund’s obligations under such borrowing or
preferred shares remain fixed.

In addition, the rights of lenders and the holders of preferred shares and
debt securities issued by the Fund will be senior to the rights of the holders of common shares with respect to the payment of dividends or to the payment of assets upon liquidation. Holders of preferred shares have voting rights in addition to and
separate from the voting rights of common shareholders. See “Description of Securities — Preferred Shares” and “Certain Provisions of the Agreement and Declaration of Trust and By-Laws, Including Antitakeover Provisions.”
The holders of preferred shares or debt, if any, on the one hand, and the holders of the common shares, on the other, may have interests that conflict in certain situations.

Leverage is a speculative technique that could adversely affect the returns to common shareholders. Leverage can cause the Fund to lose money and can magnify the effect of any losses. To the extent the
income or capital appreciation derived from securities purchased with funds received from leverage exceeds the cost of leverage, the Fund’s return will be greater than if leverage had not been used. Conversely, if the income or capital
appreciation from the securities purchased with such funds is not sufficient to cover the cost of leverage or if the Fund incurs capital losses, the return of the Fund will be less than if leverage had not been used, and therefore the amount
available for distribution to common shareholders as dividends and other distributions will be reduced or potentially eliminated.

The Fund will pay, and common shareholders will effectively bear, any costs and expenses relating to any borrowings and to the issuance and ongoing maintenance of preferred shares or debt securities. Such
costs and expenses include the higher management fee resulting from the use of any such leverage, offering and/or issuance costs, and interest and/or dividend expense and ongoing maintenance. These conditions may, directly or indirectly, result in
higher leverage costs to common shareholders.

Certain types of borrowings may result in the Fund being subject to covenants in
credit agreements, including those relating to asset coverage, borrowing base and portfolio composition requirements and additional covenants that may affect the Fund’s ability to pay dividends and distributions on common shares in certain
instances. The Fund may also be required to pledge its assets to the lenders in connection with certain types of

12

borrowings. The Fund may be subject to certain restrictions on investments imposed by guidelines of and covenants with rating agencies which may issue ratings for the preferred shares or
short-term debt instruments issued by the Fund. These guidelines and covenants may impose asset coverage or portfolio composition requirements that are more stringent than those imposed by the 1940 Act. The Board reserves the right to change the
amount and type of leverage that the Fund uses, and reserves the right to implement changes to the Fund’s borrowings that it believes are in the long-term interests of the Fund and its shareholders, even if such changes impose a higher interest
rate or other costs or impacts over the intermediate, or short-term time period. There is no guarantee that the Fund will maintain leverage at the current rate, and the Board reserves the right to raise, decrease, or eliminate the Fund’s
leverage exposure. See “Prospectus Summary — Use of Leverage by the Fund.”

Liquidity
Risk.    The Fund may invest without limit in securities that, at the time of investment, are illiquid (i.e., any investment that the Fund reasonably expects cannot be sold or disposed of in current market conditions in seven
calendar days or less without the sale or disposition significantly changing the market value of the investment). Illiquid securities may be difficult to dispose of at a fair price at the times when the Fund believes it is desirable to do so.
Investment of the Fund’s assets in illiquid securities may restrict the Fund’s ability to take advantage of market opportunities. The market price of illiquid securities generally is more volatile than that of more liquid securities, which
may adversely affect the price that the Fund pays for or recovers upon the sale of illiquid securities. Illiquid securities are also more difficult to value and may be fair valued by the Board, in which case Calamos’ judgment may play a greater
role in the valuation process. The risks associated with illiquid securities may be particularly acute in situations in which the Fund’s operations require cash and could result in the Fund borrowing to meet its short-term needs or incurring
losses on the sale of illiquid securities. Under adverse market or economic conditions, the secondary market for securities could contract further, independent of any specific adverse changes in the condition of a particular issuer, and these
instruments may become illiquid. As a result, the Fund could find it more difficult to sell these securities or may be able to sell the securities only at prices lower than if such securities were widely traded. Prices realized upon the sale of such
lower rated or unrated securities, under these circumstances, may be less than the prices used in calculating the Fund’s net asset value. See “Risk Factors — Fund Risks — Liquidity Risk.”

Management Risk.    Calamos’ judgment about the attractiveness, relative value or potential appreciation
of a particular sector, security or investment strategy may prove to be incorrect. See “Risk Factors — Fund Risks — Management Risk.”

Market Disruption Risk.    Certain events have a disruptive effect on the securities markets, such as terrorist attacks, war and other geopolitical events, earthquakes, storms
and other disasters. The Fund cannot predict the effects of similar events in the future on the U.S. economy or any foreign economy. See “Risk Factors — Fund Risks — Market Disruption Risk.”

Non-Convertible Income Securities Risk.    The Fund will also invest in non-convertible income
securities. The Fund’s investments in non-convertible income securities may have fixed or variable principal payments and all types of interest rate and dividend payment and reset terms, including fixed rate, adjustable rate, zero
coupon, contingent, deferred, payment in kind and auction rate features. Recent events in the fixed-income market may expose the Fund to heightened interest rate risk and volatility. See “Risk
Factors — Fund Risks — Non-Convertible Income Securities Risk.”

Non-U.S. Government
Obligation Risk.    An investment in debt obligations of non-U.S. governments and their political subdivisions involves special risks that are not present in corporate debt obligations. The non-U.S. issuer of the sovereign
debt or the non-U.S. governmental authorities that control the repayment of the debt may be unable or unwilling to repay principal or interest when due, and the Fund may have limited recourse in the event of a default. During periods of economic
uncertainty, the market prices of sovereign debt may be more volatile than prices of debt obligations of U.S. issuers. See “Risk Factors — Fund Risks — Non-U.S. Government Obligation Risk.”

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Recent Market Events.    In the past decade, financial
markets throughout the world have experienced increased volatility, depressed valuations, decreased liquidity and heightened uncertainty and turmoil. This turmoil resulted in unusual and extreme volatility in the equity and debt markets, in the
prices of individual securities and in the world economy. Events that have contributed to these market conditions include, but are not limited to, major cybersecurity events, geopolitical events (including wars and terror attacks), measures to
address budget deficits, downgrading of sovereign debt, declines in oil and commodity prices, dramatic changes in currency exchange rates, and public sentiment. In addition, many governments and quasi-governmental entities throughout the world have
responded to the turmoil with a variety of significant fiscal and monetary policy changes, including, but not limited to, direct capital infusions into companies, new monetary programs and dramatically lower interest rates.

While the extreme volatility and disruption that U.S. and global markets experienced for an extended period of time beginning in 2007 and
2008 has generally subsided, uncertainty and periods of volatility remain, and risks to a robust resumption of growth persist. Federal Reserve policy, including with respect to certain interest rates and the decision to begin tapering its
quantitative easing policy, may adversely affect the value, volatility and liquidity of dividend and interest paying securities. Market volatility, rising interest rates and/or a return to unfavorable economic conditions may lower the Fund’s
performance or impair the Fund’s ability to achieve its investment objective.

In June 2019-2020, the United Kingdom
approved a referendum to leave the European Union (“EU”) (“Brexit”). On March 29, 2019-2020, the United Kingdom formally notified the European Council of its intention to leave the EU and commenced the formal process of
withdrawing from the EU. The withdrawal agreement entered into between the United Kingdom and the EU entered into force on January 31, 2020, at which time the United Kingdom ceased to be a member of the EU. Following the withdrawal, there will
be an eleven-month transition period, ending December 31, 2020, during which the United Kingdom will negotiate its future relationship with the EU. Brexit has resulted in volatility in European and global markets and could have negative
long-term impacts on financial markets in the United Kingdom and throughout Europe. There is considerable uncertainty about the potential consequences for Brexit, how it will be conducted, how negotiations of trade agreements will proceed, and how
the financial markets will react, and as this process unfolds, markets may be further disrupted. Given the size and importance of the United Kingdom’s economy, uncertainty about its legal, political, and economic relationship with the remaining
member states of the EU may continue to be a source of instability. Moreover, other countries may seek to withdraw from the European Union and/or abandon the euro, the common currency of the EU.

A number of countries in Europe have suffered terror attacks, and additional attacks may occur in the future. Ukraine has experienced
ongoing military conflict; this conflict may expand and military attacks could occur elsewhere in Europe. Europe has also been struggling with mass migration from the Middle East and Africa. The ultimate effects of these events and other
socio-political or geographical issues are not known but could profoundly affect global economies and markets.

As a result of
political and military actions undertaken by Russia, the U.S. and the EU have instituted sanctions against certain Russian officials and companies. These sanctions and any additional sanctions or other intergovernmental actions that may be
undertaken against Russia in the future may result in the devaluation of Russian currency, a downgrade in the country’s credit rating, and a decline in the value and liquidity of Russian securities. Such actions could result in a freeze of
Russian securities, impairing the ability of a fund to buy, sell, receive, or deliver those securities. Retaliatory action by the Russian government could involve the seizure of US and/or European residents’ assets, and any such actions are
likely to impair the value and liquidity of such assets. Any or all of these potential results could have an adverse/recessionary effect on Russia’s economy. All of these factors could have a negative effect on the performance of funds that
have significant exposure to Russia.

In addition, policy and legislative changes in the United States and in other
countries are changing many aspects of financial regulation. The impact of these changes on the markets, and the practical implications for market participants, may not be fully known for some time. Widespread disease and virus epidemics could

14

likewise be highly disruptive, adversely affecting individual companies, sectors, industries, markets, currencies, interest and inflation rates, credit ratings, investor sentiment, and other
factors affecting the value of the Fund’s investments. See “Risk Factors — Fund Risks — Recent Market Events.”

REIT Risk.    Investing in real estate investment trusts (“REITs”) involves certain unique risks in addition to those risks associated with investing in the real
estate industry in general. An equity REIT may be affected by changes in the value of the underlying properties owned by the REIT. A mortgage REIT may be affected by changes in interest rates and the ability of the issuers of its portfolio mortgages
to repay their obligations. REITs are dependent upon the skills of their managers and are not diversified.

REITs are generally
dependent upon maintaining cash flows to repay borrowings and to make distributions to shareholders and are subject to the risk of default by lessees or borrowers. REITs whose underlying assets are concentrated in properties used by a particular
industry, such as health care, are also subject to risks associated with such industry. REITs (especially mortgage REITs) are also subject to interest rate risks. When interest rates decline, the value of a REIT’s investment in fixed rate
obligations can be expected to rise. Conversely, when interest rates rise, the value of a REIT’s investment in fixed rate obligations can be expected to decline. If the REIT invests in adjustable rate mortgage loans the interest rates on which
are reset periodically, yields on a REIT’s investments in such loans will gradually align themselves to reflect changes in market interest rates. This causes the value of such investments to fluctuate less dramatically in response to interest
rate fluctuations than would investments in fixed rate obligations. REITs may have limited financial resources, may utilize significant amounts of leverage, may trade less frequently and in a limited volume and may be subject to more abrupt or
erratic price movements than larger company securities.

Historically, REITs have been more volatile in price than the larger
capitalization stocks included in Standard & Poor’s 500 Stock Index. See “Risk Factors — Fund Risks — REIT Risk.”

Risks Associated with Options.    There are several risks associated with transactions in options. For example, there are significant differences between the securities markets
and options markets that could result in an imperfect correlation among these markets, causing a given transaction not to achieve its objectives. A decision as to whether, when and how to use options involves the exercise of skill and judgment, and
even a well-conceived transaction may be unsuccessful to some degree because of market behavior or unexpected events. The Fund’s ability to utilize options successfully will depend on Calamos’ ability to predict pertinent market movements,
which cannot be assured.

The Fund may sell options on individual securities and securities indices. All call options sold by
the Fund must be “covered.” Even though the Fund will receive the option premium to help protect it against loss, a call option sold by the Fund exposes the Fund during the term of the option to possible loss of opportunity to realize
appreciation in the market price of the underlying security or instrument and may require the Fund to hold a security or instrument that it might otherwise have sold. In addition, a loss on a call option sold may be greater than the premium
received. The Fund may purchase and sell put options on individual securities and securities indices. In selling put options, there is a risk that the Fund may be required to buy the underlying security at a disadvantageous price above the market
price. The Fund may purchase and sell put options on individual securities and securities indices. In selling put options, there is a risk that the Fund may be required to buy the underlying security at a disadvantageous price above the market
price. See “Risk Factors — Fund Risks — Risks Associated with Options.”

Rule 144A Securities
Risk.    The Fund may invest in securities that are issued and sold through transactions under Rule 144A of the Securities Act of 1933. Under the supervision and oversight of the Board, Calamos will determine whether Rule
144A Securities are illiquid. If qualified institutional buyers are unwilling to purchase these Rule 144A Securities, the percentage of the Fund’s assets invested in illiquid securities would increase. Typically, the Fund purchases Rule 144A
Securities only if the Fund’s adviser has determined them to be liquid. If any Rule 144A Security held by the Fund should become illiquid, the value of the security may be reduced and a sale of the security may be more difficult.

15

Synthetic Convertible Instruments Risk.    The value of
a synthetic convertible instrument may respond differently to market fluctuations than a convertible instrument because a synthetic convertible instrument is composed of two or more separate securities, each with its own market value. In addition,
if the value of the underlying common stock or the level of the index involved in the convertible component falls below the exercise price of the warrant or option, the warrant or option may lose all value. See “Risk
Factors — Fund Risks — Synthetic Convertible Instruments Risk.”

Tax
Risk.    The Fund may invest in certain securities, such as certain convertible securities and high yield securities, for which the federal income tax treatment may not be clear or may be subject to re-characterization by the
Internal Revenue Service (“IRS”). It could be more difficult for the Fund to comply with the federal income tax requirements applicable to regulated investment companies if the tax characterization of the Fund’s investments is not
clear or if the tax treatment of the income from such investments was successfully challenged by the IRS. In addition, the tax treatment of the Fund may be affected by future interpretations of the Internal Revenue Code of 1986, as amended (the
“Code”), and changes in the tax laws and regulations, all of which may apply with retroactive effect. See “Risk Factors — Fund Risks — Tax Risk” and “Certain Federal Income Tax Matters.”

Additional Risks to Common Shareholders

Additional risks of investing in common shares include the following:

Diminished Voting Power and Excess Cash Risk.    The voting power of current shareholders will be diluted to the extent that such shareholders do not purchase shares in any
future common share offerings or do not purchase sufficient shares to maintain their percentage interest. In addition, if we are unable to invest the proceeds of such offering as intended, our per share distribution may decrease (or may consist of
return of capital) and we may not participate in market advances to the same extent as if such proceeds were fully invested as planned.

Interest Rate Transactions Risk.    The Fund may enter into an interest rate swap, cap or floor transaction to attempt to protect itself from increasing dividend or interest
expenses on its leverage resulting from increasing short-term interest rates and to hedge its portfolio securities. A decline in interest rates may result in a decline in the value of the swap or cap, which may result in a decline in the net asset
value of the Fund. See “Risk Factors — Interest Rate Transactions Risk.”

Market Discount
Risk.    The Fund’s common shares have traded both at a premium and at a discount relative to net asset value. Common shares of closed-end investment companies frequently trade at prices lower than their net asset value.
Depending on the premium of the Fund’s common shares, the Fund’s net asset value may be reduced immediately following an offering of the Fund’s common shares by the offering expenses paid by the Fund. See “Use of Proceeds.”

In addition to net asset value, the market price of the Fund’s common shares may be affected by such factors as the
Fund’s use of leverage, dividend stability, portfolio credit quality, liquidity, market supply and demand of the common shares and the Fund’s dividends paid (which are, in turn, affected by expenses), call protection for portfolio
securities and interest rate movements. See “Leverage,” “Risk Factors” and “Description of Securities.” The Fund’s common shares are designed primarily for long-term investors, and you should not purchase common
shares if you intend to sell them shortly after purchase.

Whether shareholders will realize a gain or loss upon the sale of
the Fund’s common shares depends upon whether the market value of the shares at the time of sale is above or below the price the shareholder paid, taking into account transaction costs for the shares, and is not directly dependent upon the
Fund’s net asset value. Because the market value of the Fund’s common shares will be determined by factors such as the relative demand for and supply of the shares in the market, general market conditions and other factors beyond the
control of the Fund, the Fund cannot predict whether its common shares will trade at, below or above the Fund’s net asset value, or below or above the public offering price for the common shares.

16

Market Impact Risk.    The sale of our common shares (or
the perception that such sales may occur) may have an adverse effect on prices in the secondary market for our common shares. An increase in the number of common shares available may put downward pressure on the market price for our common shares.
These sales also might make it more difficult for us to sell additional equity securities in the future at a time and price we deem appropriate.

Reduction of Leverage Risk.    We have previously taken, and may in the future take, action to reduce the amount of leverage employed by the Fund. Reduction of the leverage
employed by the Fund, including by redemption of preferred shares, will in turn reduce the amount of assets available for investment in portfolio securities. This reduction in leverage may negatively impact our financial performance, including our
ability to sustain current levels of distributions on common shares.

See “Risk Factors — Additional Risks to
Common Shareholders” for a more detailed discussion of these risks.

Additional Risks to Senior Security Holders

Additional risks of investing in senior securities include the following:

Generally, an investment in preferred shares (including exchange-listed preferred shares) or debt securities (collectively, “senior
securities”) is subject to the following risks:

Decline in Net Asset Value Risk.    A
material decline in our NAV may impair our ability to maintain required levels of asset coverage for outstanding borrowings or any debt securities or preferred shares.

Early Redemption Risk.    The Fund may voluntarily redeem preferred shares or may be forced to redeem preferred shares to meet regulatory requirements and the asset coverage
requirements of the preferred shares. Such redemptions may be at a time that is unfavorable to holders of the preferred shares.

Inflation Risk.    Inflation is the reduction in the purchasing power of money resulting from an increase in
the price of goods and services. Inflation risk is the risk that the inflation adjusted or “real” value of an investment in preferred stock or debt securities or the income from that investment will be worth less in the future. As
inflation occurs, the real value of the preferred stock or debt securities and the dividend payable to holders of preferred stock or interest payable to holders of debt securities declines.

Interest Rate Risk.    Rising market interest rates could impact negatively the value of our investment
portfolio, reducing the amount of assets serving as asset coverage for the senior securities. Rising market interest rates could also reduce the value of the Fund’s senior securities.

Market Discount Risk.    The market price of exchange-listed preferred shares that the Fund may issue may also
be affected by such factors as the Fund’s use of leverage, dividend stability, portfolio credit quality, liquidity, and the Fund’s dividends paid (which are, in turn, affected by expenses), call protection for portfolio securities and
interest rate movements.

Ratings and Asset Coverage Risk.    To the extent that senior
securities are rated, a rating does not eliminate or necessarily mitigate the risks of investing in our senior securities, and a rating may not fully or accurately reflect all of the credit and market risks associated with that senior security. A
rating agency could downgrade the rating of our shares of preferred stock or debt securities, which may make such securities less liquid in the secondary market, though potentially with higher resulting interest rates. If a rating agency downgrades
the rating assigned to a senior security, we may alter our portfolio or redeem the senior security. We may voluntarily redeem senior securities under certain circumstances.

Secondary Market Risk.    The market value of exchange-listed preferred shares that the Fund may issue will be determined by factors such as the relative demand for and supply
of the preferred shares in the market, general market conditions and other factors beyond the control of the Fund. It may be difficult to predict the trading

17

patterns of preferred shares, including the effective costs of trading. There is a risk that the market for preferred shares may be thinly traded and relatively illiquid compared to the market
for other types of securities.

Senior Leverage Risk.    Preferred shares will be junior in
liquidation and with respect to distribution rights to debt securities and any other borrowings. Senior securities representing indebtedness may constitute a substantial lien and burden on preferred shares by reason of their prior claim against our
income and against our net assets in liquidation. We may not be permitted to declare dividends or other distributions with respect to any series of preferred shares unless at such time we meet applicable asset coverage requirements and the payment
of principal or interest is not in default with respect to any borrowings.

See “Risk Factors — Additional Risks
to Senior Security Holders” for a more detailed discussion of these risks.

18

SUMMARY OF FUND EXPENSES

The following table and example contain information about the costs and expenses that common shareholders will bear directly or
indirectly. In accordance with Commission requirements, the table below shows our expenses, including interest payments on borrowed funds, and preferred stock dividend payments, as a percentage of our average net assets as of January 31, 2020,
and not as a percentage of gross assets or managed assets.

By showing expenses as a percentage of average net assets, expenses
are not expressed as a percentage of all of the assets we invest. The table and example are based on our capital structure as of January 31, 2020. As of January 31, 2020, the Fund had $31 million in borrowings outstanding,
$100 million in outstanding preferred shares and additional structural leverage of $254 million, collectively representing 32.5% of managed assets.

Shareholder Transaction Expenses

Sales Load (as a percentage of offering price)


(1)

Offering Expenses Borne by the Fund (as a percentage of offering price)


(1)

Dividend Reinvestment Plan Fees (per sales transaction fee)(2)

$
15.00

Annual Expenses

Percentage of Average NetAssets Attributable toCommon Shareholders

Management Fee(3)

1.13
%

Interest Payments on Borrowed Funds(4)

0.80
%

Preferred Stock Dividend Payments(5)

0.51
%

Other Expenses(6)

0.09
%

Acquired Fund Fees and Expenses(7)

0.01
%

Total Annual Expenses

2.54
%

Example:

The following example illustrates the expenses that common shareholders would pay on a $1,000 investment in common shares, assuming (1) total annual expenses of 2.54% of net assets attributable to
common shareholders; (2) a 5% annual return; and (3) all distributions are reinvested at net asset value:

1 Year
 
  
3 Years
 
  
5 Years
 
  
10 Years

Total Expenses Paid by Common Shareholders(8)

$
26
 
  
$
79
 
  
$
135
 
  
$
287

The example should not be considered a representation of future expenses. Actual expenses may be
greater or less than those assumed. Moreover, our actual rate of return may be greater or less than the hypothetical 5% return shown in the example.

(1)

If the securities to which this prospectus relates are sold to or through underwriters, the prospectus supplement will set forth any
applicable sales load and the estimated offering expenses borne by us.

(2)

Shareholders will pay a $15.00 transaction fee plus a $0.02 per share brokerage charge if they direct the Plan Agent (as defined below) to
sell common shares held in a Plan account. In addition, each participant will pay a pro rata share of brokerage commissions incurred with respect to the Plan Agent’s open-market purchases in connection with the reinvestment of dividends or
distributions. If a participant elects to have the Plan Agent sell part or all of his or her common shares and remit the proceeds, such participant will be charged his or her pro rata share of brokerage commissions on the shares sold. See
“Dividends and Distributions on Common Shares; Automatic Dividend Reinvestment Plan.”

(3)

The Fund pays Calamos an annual management fee, payable monthly in arrears, for its investment management services in an amount equal to 0.80%
of the Fund’s average weekly managed assets. In accordance with the requirements of the Commission, the table above shows the Fund’s management fee as a percentage of average net assets attributable to common shareholders. By showing the
management fee as a percentage of net assets, the management fee is not expressed as a percentage of all of the assets the Fund

19

intends to invest. For purposes of the table, the management fee has been converted to 1.13% of the Fund’s average weekly net assets as of January 31, 2020 by dividing the total dollar
amount of the management fee by the Fund’s average weekly net assets (managed assets less outstanding leverage).

(4)

Reflects interest expense paid on $39.4 million in average borrowings under the SSB Agreement, plus $238.9 million in additional
average structural leverage related to certain securities lending programs, as described under “Leverage.”

(5)

Reflects estimated dividend expense on $100 million aggregate liquidation preference of mandatory redeemable preferred shares
outstanding. See “Leverage.”

(6)

“Other Expenses” are based on estimated amounts for the Fund’s current fiscal year.

(7)

“Acquired Fund Fees and Expenses” are the indirect costs of investing in other investment companies such as money market funds and
ETFs.

(8)

The example does not include sales load or estimated offering costs, which would cause the expenses shown in the example to increase. In
connection with an offering of common shares, the applicable prospectus supplement will set forth an example including sales load and estimated offering costs.

The purpose of the table and the example above is to help investors understand the fees and expenses that they, as common shareholders,
would bear directly or indirectly. For additional information with respect to our expenses, see “Management of the Fund.”

20

FINANCIAL HIGHLIGHTS

The information in the following table shows selected data for a common share outstanding throughout each period listed below. The
information in this table for the year ended October 31, 2019 and each of the prior years then ended is derived from our financial statements audited by Deloitte & Touche LLP, whose report on such financial statements is contained in
the Fund’s annual report dated October 31, 2019 and is included in the statement of additional information, both of which are available from the Fund. See “Available Information” in this prospectus.

Selected data for a share outstanding throughout each year was as follows:

2019
 
 
2019-2020
 
 
2019-2020
 
 
2019-2020
 
 
2015
 
 
2014
 
 
2013
 
 
2012
 
 
2011
 
 
2010

PER SHARE OPERATING PERFORMANCE

Net asset value, beginning of year

$
10.46
 
 
$
11.35
 
 
$
10.73
 
 
$
11.68
 
 
$
13.45
 
 
$
13.20
 
 
$
12.45
 
 
$
12.31
 
 
$
12.84
 
 
$
11.83

Income from investment operations:

Net investment income (loss)*

0.50
 
 
 
0.57
 
 
 
0.57
 
 
 
0.60
 
 
 
0.62
 
 
 
0.72
 
 
 
0.75
 
 
 
0.81
 
 
 
0.83
 
 
 
0.91

Net realized and unrealized gain (loss)

0.64
 
 
 
(0.33

 
 
1.19
 
 
 
(0.41

 
 
(1.25

 
 
0.67
 
 
 
1.14
 
 
 
0.47
 
 
 
(0.23

 
 
1.22

Total from investment operations

1.14
 
 
 
0.24
 
 
 
1.76
 
 
 
0.19
 
 
 
(0.63

 
 
1.39
 
 
 
1.89
 
 
 
1.28
 
 
 
0.60
 
 
 
2.13

Less distributions to common shareholders from:

Net investment income

(0.48

 
 
(1.13

 
 
(0.67

 
 
(0.59

 
 
(0.81

 
 
(0.95

 
 
(1.14

 
 
(1.14

 
 
(0.84

 
 
(1.00
)

Net realized gains

(0.31

 
 

 
 
 
(0.08

 
 

 
 
 
(0.02

 
 
(0.19

 
 

 
 
 

 
 
 

 
 
 

Return of capital

(0.17

 
 

 
 
 
(0.39

 
 
(0.55

 
 
(0.31

 
 

 
 
 

 
 
 

 
 
 
(0.30

 
 
(0.14
)

Total distributions

(0.96

 
 
(1.13

 
 
(1.14

 
 
(1.14

 
 
(1.14

 
 
(1.14

 
 
(1.14

 
 
(1.14

 
 
(1.14

 
 
(1.14
)

Net asset value, end of year

$
10.64
 
 
$
10.46
 
 
$
11.35
 
 
$
10.73
 
 
$
11.68
 
 
$
13.45
 
 
$
13.20
 
 
$
12.45
 
 
$
12.31
 
 
$
12.84

Market value, end of year

$
10.67
 
 
$
9.91
 
 
$
11.59
 
 
$
9.89
 
 
$
10.41
 
 
$
13.69
 
 
$
13.09
 
 
$
12.51
 
 
$
12.09
 
 
$
13.09

TOTAL RETURN APPLICABLE TO COMMON SHAREHOLDERS

Total investment return based on:(b)

Net asset value

11.75

 
 
1.81

 
 
17.48

 
 
3.19

 
 
(4.69
)% 
 
 
10.90

 
 
16.08

 
 
11.05

 
 
4.92

 
 
19.12
%

Market value

18.29

 
 
(5.54
)% 
 
 
30.15

 
 
6.72

 
 
(16.54
)% 
 
 
13.83

 
 
14.56

 
 
13.62

 
 
1.08

 
 
26.02
%

RATIOS TO AVERAGE NET ASSETS APPLICABLE TO COMMON SHAREHOLDERS

Net expenses(c)(d)

2.88

 
 
2.52

 
 
1.88

 
 
1.74

 
 
1.84

 
 
1.47

 
 
1.49

 
 
1.57

 
 
1.55

 
 
1.71
%

Net investment income (loss)(d)

4.77

 
 
5.11

 
 
5.17

 
 
5.61

 
 
4.90

 
 
5.38

 
 
5.92

 
 
6.60

 
 
6.56

 
 
7.48
%

SUPPLEMENTAL DATA

Net assets applicable to common shareholders, end of year (000)

$
754,310
 
 
$
741,306
 
 
$
797,968
 
 
$
750,773
 
 
$
817,491
 
 
$
931,703
 
 
$
891,350
 
 
$
840,737
 
 
$
827,339
 
 
$
801,354

Portfolio turnover rate

51

 
 
58

 
 
90

 
 
34

 
 
36

 
 
40

 
 
62

 
 
56

 
 
44

 
 
37
%

Average commission rate paid

$
0.0188
 
 
$
0.0270
 
 
$
0.0282
 
 
$
0.0220
 
 
$
0.0303
 
 
$
0.0294
 
 
$
0.0295
 
 
$
0.0230
 
 
$
0.0222
 
 
$

Capital charge resulting from issuance of common and preferred shares and related offering costs

$

 
 
$

 
 
$

 
 
$

 
 
$

 
 
$

(a) 
 
$

(a) 
 
$

(a) 
 
$

(a) 
 
$

(a)

Premiums from shares sold in at the market offerings

$

 
 
$

(a) 
 
$

(a) 
 
$

 
 
$

(a) 
 
$

(a) 
 
$

 
 
$

(a) 
 
$
0.01
 
 
$
0.02

Mandatory Redeemable Preferred Shares, at redemption value ($25 per share liquidation preference) (000’s
omitted)

$
100,000
 
 
$
100,000
 
 
$
100,000
 
 
$

 
 
$

 
 
$

 
 
$

 
 
$

 
 
$

 
 
$

Notes Payable (000’s omitted)

$
277,400
 
 
$
288,000
 
 
$
275,000
 
 
$
306,000
 
 
$
353,000
 
 
$
360,000
 
 
$
350,000
 
 
$
285,000
 
 
$
285,000
 
 
$
193,000

Asset coverage per $1,000 of loan
outstanding(e)

$
4,080
 
 
$
3,921
 
 
$
4,265
 
 
$
3,454
 
 
$
3,316
 
 
$
3,588
 
 
$
3,547
 
 
$
3,950
 
 
$
3,903
 
 
$
5,152

Asset coverage per $25 liquidation value per share of Mandatory Redeemable Preferred Shares(f)

$
283
 
 
$
282
 
 
$
293
 
 
$

 
 
$

 
 
$

 
 
$

 
 
$

 
 
$

 
 
$

*

Net investment income calculated based on average shares method.

21

(a)

Amount equated to less than $0.005 per common share.

(b)

Total investment return is calculated assuming a purchase of common stock on the opening of the first day and a sale on the closing of the
last day of the period reported. Dividends and distributions are assumed, for purposes of this calculation, to be reinvested at prices obtained under the Fund’s dividend reinvestment plan. Total return is not annualized for periods less than
one year. Brokerage commissions are not reflected. NAV per share is determined by dividing the value of the Fund’s portfolio securities, cash and other assets, less all liabilities, by the total number of common shares outstanding. The common
share market price is the price the market is willing to pay for shares of the Fund at a given time. Common share market price is influenced by a range of factors, including supply and demand and market conditions.

(c)

Ratio of net expenses, excluding interest expense on Notes Payable and interest expense and amortization of offering costs on Mandatory
Redeemable Preferred Shares, to average net assets was 1.29%, 1.28%, 1.24%, 1.24%, 1.50%, 1.18%, 1.17%, 1.17%, 1.19%, and 1.19%, respectively.

(d)

Does not reflect the effect of dividend payments to Auction Rate Preferred Shareholders.

(e)

Calculated by subtracting the Fund’s total liabilities (not including Notes payable and Mandatory Redeemable Preferred Shares) from the
Fund’s total assets and dividing this by the amount of notes payable outstanding, and by multiplying the result by 1,000.

(f)

Calculated by subtracting the Fund’s total liabilities (not including Notes payable and Mandatory Redeemable Preferred Shares) from the
Fund’s total assets and dividing this by the amount of Mandatory Redeemable Preferred Shares outstanding, and by multiplying the result by 25.

The following table sets forth information regarding the Fund’s outstanding bank loans and MRP Shares as of the end of each of the Fund’s last ten fiscal years, as applicable. The information in
the table shown below comes from the Fund’s financial statements for the fiscal year ended October 31, 2019, and each of the prior nine years then ended, all of which have been audited by Deloitte & Touche LLP, the Fund’s
independent registered public accounting firm.

Fiscal Year Ended

Total AmountOutstanding
 
  
AssetCoverage
 
 
LiquidatingPreference perPreferred Share(c)
 
  
AverageMarketValue perPreferred Share
 
 
Type ofSeniorSecurity

October 31, 2019

$
277,400,000
 
  
 
4,080
(a)  
 
 

 
  
 

 
 
 
Loan

October 31, 2019

$
100,000,000
 
  
 
283
(b)  
 
 
25
 
  
 
25
(d)  
 
 
MRPS

October 31, 2019-2020

$
288,000,000
 
  
 
3,921
(a)  
 
 

 
  
 

 
 
 
Loan

October 31, 2019-2020

$
100,000,000
 
  
 
282
(b)  
 
 
25
 
  
 
25
(d)  
 
 
MRPS

October 31, 2019-2020

$
275,000,000
 
  
 
4,265
(a)  
 
 

 
  
 

 
 
 
Loan

October 31, 2019-2020

$
100,000,000
 
  
 
293
(b)  
 
 
25
 
  
 
25
(d)  
 
 
MRPS

October 31, 2019-2020

$
306,000,000
 
  
 
3,454
(a)  
 
 

 
  
 

 
 
 
Loan

October 31, 2015

$
353,000,000
 
  
 
3,316
(a)  
 
 

 
  
 

 
 
 
Loan

October 31, 2014

$
360,000,000
 
  
 
3,588
(a)  
 
 

 
  
 

 
 
 
Loan

October 31, 2013

$
350,000,000
 
  
 
3,547
(a)  
 
 

 
  
 

 
 
 
Loan

October 31, 2012

$
285,000,000
 
  
 
3,950
(a)  
 
 

 
  
 

 
 
 
Loan

October 31, 2011

$
285,000,000
 
  
 
3,903
(a)  
 
 

 
  
 

 
 
 
Loan

October 31, 2010

$
193,000,000
 
  
 
5,152
(a)  
 
 

 
  
 

 
 
 
Loan

(a)

Calculated by subtracting the Fund’s total liabilities (not including notes payable and MRPS) from the Fund’s total assets and
dividing this by the amount of notes payable outstanding, and by multiplying the result by 1,000.

(b)

Calculated by subtracting the Fund’s total liabilities (not including MRPS) from the Fund’s total assets and dividing this by the
number of MRPS outstanding, and by multiplying the result by 25.

(c)

“Liquidating Preference per Preferred Share” means the amount to which a holder of preferred shares would be entitled upon the
liquidation of the Fund in preference to common shareholders, expressed as a dollar amount per preferred share.

(d)

The MRPS are not listed on any exchange or automated quotation system. The MRPS are considered debt of the issuer; and the liquidation
preference approximates fair value.

22

MARKET AND NET ASSET VALUE INFORMATION

Our common shares are listed on the Nasdaq Global Select Market (“Nasdaq”) under the symbol “CHI.” Our common shares
commenced trading on the New York Stock Exchange (“NYSE”) in June 2002. On July 2, 2012, the common shares ceased trading on the NYSE and commenced trading on Nasdaq.

Our common shares have traded both at a premium and a discount to NAV. We cannot predict whether our shares will trade in the future at a
premium or discount to NAV. The provisions of the 1940 Act generally require that the public offering price of common shares (less any underwriting commissions and discounts) must equal or exceed the NAV per share of a company’s common stock
(calculated within 48 hours of pricing). Our issuance of common shares may have an adverse effect on prices in the secondary market for our common shares by increasing the number of common shares available, which may put downward pressure on the
market price for our common shares. Shares of common stock of closed-end investment companies frequently trade at a discount from NAV. See “Risk Factors — Additional Risks to Common Shareholders — Market
Discount Risk.”

The following table sets forth for each of the periods indicated the high and low closing market
prices for our common shares on Nasdaq, the NAV per share and the premium or discount to NAV per share at which our common shares were trading. NAV is shown for the last business day of each quarter. See “Net Asset Value” for information
as to the determination of our NAV.

Market Price(1)
 
  
Net AssetValue(2)
 
  
Premium/(Discount)to Net AssetValue(3)

Quarter Ended

High
 
  
Low
 
  
High
 
 
Low

January 31, 2019-2020

$
11.66
 
  
$
11.00
 
  
$
11.38
 
  
 
3.09

 
 
(1.79
)%

April 30, 2019-2020

$
11.40
 
  
$
10.43
 
  
$
10.93
 
  
 
1.60

 
 
(2.80
)%

July 31, 2019-2020

$
12.17
 
  
$
11.31
 
  
$
11.10
 
  
 
8.95

 
 
2.17
%

October 31, 2019-2020

$
12.89
 
  
$
9.85
 
  
$
10.46
 
  
 
13.97

 
 
(4.92
)%

January 31, 2019

$
10.49
 
  
$
8.30
 
  
$
10.45
 
  
 
(2.15
)% 
 
 
(12.54
)%

April 30, 2019

$
10.67
 
  
$
10.00
 
  
$
10.90
 
  
 
(2.11
)% 
 
 
(5.39
)%

July 31, 2019

$
10.83
 
  
$
9.84
 
  
$
10.95
 
  
 
(1.99
)% 
 
 
(4.19
)%

October 31, 2019

$
10.72
 
  
$
10.23
 
  
$
10.64
 
  
 
(1.65
)% 
 
 
(2.57
)%

January 31, 2020

$
11.33
 
  
$
10.65
 
  
$
11.30
 
  
 
(1.48
)% 
 
 
(0.84
)%

Source: Bloomberg Financial and Fund Accounting Records.

(1)

Based on high and low closing market price per share during the respective quarter and does not reflect commissions.

(2)

Based on the NAV calculated on the close of business on the last business day of each calendar quarter.

(3)

Premium and discount information is shown for the days when the Fund experienced its high and low closing market prices, respectively, per
share during the respective quarter.

The last reported sale price, NAV per common share and percentage
discount to NAV per common share on January 31, 2020 were $11.13, $11.30 and (1.50)%, respectively. As of January 31, 2020, we had 70,923,815 common shares outstanding and managed assets of $1.19 billion.

USE OF PROCEEDS

Subject to the remainder of this section, and unless otherwise specified in a prospectus supplement, we currently intend to invest the net proceeds of any sales of our securities pursuant to this
prospectus in accordance with our investment objective and policies as described under “Investment Objective and Principal Investment Strategies” within approximately three months of receipt of such proceeds. Such investments may be
delayed if suitable investments are unavailable at the time or for other reasons. Pending such investment, we anticipate that we will invest the proceeds in securities issued by the U.S. government or its agencies or instrumentalities or in high
quality, short-term or long-term debt obligations. We may also use proceeds from the sale of our securities

23

to retire all or a portion of any short-term debt we incur in pursuit of our investment objective and policies and for working capital purposes, including the payment of interest and operating
expenses, although there is currently no intent to issue securities primarily for these purposes. A delay in the anticipated use of proceeds could lower returns, reduce our distribution to common shareholders and reduce the amount of cash available
to make dividend and interest payments on preferred shares and debt securities, respectively.

THE FUND

Calamos Convertible Opportunities and Income Fund is a diversified, closed-end management investment company which commenced investment operations in June 2002. The Fund was organized as a
statutory trust under the laws of the State of Delaware on April 17, 2002, and has registered under the 1940 Act. On June 28, 2002, the Fund issued an aggregate of 40,000,000 common shares, no par value, in an initial public offering and
commenced its operations. On July 12, 2002 and August 13, 2002, the Fund issued an additional 3,000,000 and 225,000 common shares, respectively, in connection with exercises by the underwriters of their over-allotment option. The net
proceeds of the initial public offering and subsequent exercises of the over-allotment option were approximately $619,298,400 after the payment of offering expenses. As of January 31, 2019, the Fund had issued an additional 19,077,463 common
shares in connection with a continuous, at-the-market offering that commenced in June 2008 and ceased in December 2019-2020 (the “Previous ATM Offering”). The net proceeds of the Previous ATM Offering were $228,615,606. As of
January 31, 2020, the Fund had not issued additional common shares in connection with a continuous, at-the-market offering that commenced on March 8, 2019.

As of January 31, 2020, the Fund had $31 million in borrowings outstanding under the SSB Agreement, plus MRP Shares outstanding with an aggregate liquidation preference of $100 million,
plus additional structural leverage that amounted to approximately $254 million, collectively representing 32.5% of managed assets. Structural leverage refers to borrowings under the SSB Agreement in respect of which the Fund’s interest
payments are reduced or eliminated by the Fund’s securities lending activities. See “Leverage.” The Fund’s common shares are listed on Nasdaq under the symbol “CHI.” The Fund’s principal office is located at 2020
Calamos Court, Naperville, Illinois 60563, and its telephone number is 1-800-582-6959.

The following table provides
information about our outstanding securities as of January 31, 2020:

Title of Class

AmountAuthorized(shares)
 
  
AmountHeld by theFund or forits Account
 
  
AmountOutstanding(shares)

Common Shares

Unlimited
 
  
 

 
  
 
70,923,815

MRPS-Series A

1,330,000
 
  
 

 
  
 
1,330,000

MRPS-Series B

1,330,000
 
  
 

 
  
 
1,330,000

MRPS-Series C

1,340,000
 
  
 

 
  
 
1,340,000

INVESTMENT OBJECTIVE AND PRINCIPAL INVESTMENT STRATEGIES

Investment Objective

The
Fund’s investment objective is to provide total return through a combination of capital appreciation and current income. The Fund’s investment objective may be changed by the Board of Trustees without a shareholder vote, although the Fund
will give shareholders at least 60 days’ written notice of any change to the Fund’s investment objective. The Fund makes no assurance that it will realize its objective. An investment in the Fund may be speculative in that it involves a
high degree of risk and should not constitute a complete investment program. See “Risk Factors.”

Principal Investment Strategies

Under normal circumstances, the Fund invests at least 80% of its managed assets in a diversified portfolio of
convertible securities and non-convertible income securities. This is a non-fundamental policy and may be

24

changed by the Board of Trustees of the Fund provided that shareholders are provided with at least 60 days’ prior written notice of any change as required by the rules under the 1940
Act. The portion of the Fund’s assets invested in convertible securities and non-convertible income securities will vary from time to time consistent with the Fund’s investment objective, changes in equity prices and changes in
interest rates and other economic and market factors, although, under normal circumstances, the Fund will invest at least 35% of its managed assets in convertible securities. The Fund invests in securities with a broad range of maturities. The
average term to maturity of the Fund’s securities typically will range from five to ten years.

Convertible
Securities.    The Fund is not limited in the percentage of its assets invested in convertible securities, and investment in convertible securities forms an important part of the Fund’s principal investment strategies.
Under normal circumstances, the Fund will invest at least 35% of its managed assets in convertible securities. A convertible security is a debt security, debenture, note or preferred stock that may be converted into an equity security (typically
common stock of the same issuer) at a predetermined price (the “conversion price”). Depending upon the relationship of the conversion price to the market value of the underlying security, a convertible security may trade more like an
equity security than a debt instrument. The Fund may invest in convertible securities of any rating.

Calamos typically
applies a four-step approach when buying and selling convertible securities for the Fund, which includes:

1.  Evaluating the default risk of the convertible security using traditional credit analysis;

2.  Analyzing the convertible’s underlying common stock to determine its capital appreciation potential;

3.  Assessing the risk/return potential of the convertible security; and

4.  Evaluating the convertible security’s impact on the overall composition of the Fund and its diversification strategy.

In analyzing the appreciation potential of the underlying common stock and the default risk of the convertible security,
Calamos generally considers the issuer’s:

financial soundness;

ability to make interest and dividend payments;

earnings and cash-flow forecast; and

quality of management.

Synthetic Convertible Instruments.    The Fund may invest in “synthetic” convertible instruments. A synthetic convertible instrument is a financial instrument (or two
or more securities held in tandem) that is designed to simulate the economic characteristics of another instrument (i.e., a convertible security) through the combined economic features of a collection of other securities or assets. Calamos may
create a synthetic convertible instrument by combining separate securities that possess the two principal characteristics of a true convertible security, i.e., a fixed-income security (“fixed-income component”, which may be a convertible
or non-convertible security) and the right to acquire an equity security (“convertible component”). The fixed-income component is achieved by investing in fixed-income securities such as bonds, preferred stocks and money
market instruments. The convertible component is achieved by investing in warrants or options to buy common stock at a certain exercise price, or options on a stock index.

The Fund may also invest in synthetic convertible instruments created by third parties, typically investment banks. Synthetic convertible instruments created by such parties may be designed to simulate
the characteristics of traditional convertible securities or may be designed to alter or emphasize a particular feature. Traditional convertible securities typically offer the opportunity for stable cash flows with the ability to participate in
capital appreciation of the underlying common stock. Traditional convertible securities are exercisable at the option of the holder. Synthetic convertible instruments may alter these characteristics by offering enhanced yields in exchange for
reduced capital appreciation, additional risk of loss, or any combination of these features. Synthetic

25

convertible instruments may include structured notes, equity-linked notes, mandatory convertibles and combinations of securities and instruments, such as a debt instrument combined with a forward
contract.

Some examples of these securities include the following:

Preferred equity redeemable cumulative stock (“PERCS”) are shares that automatically convert into one ordinary
share upon maturity. They are usually issued at the prevailing share price, convertible into one ordinary share, with an enhanced dividend yield. PERCS pay a higher dividend than common shares, but the equity appreciation is capped. Above a certain
share price, the conversion ratio will fall as the stock rises, capping the appreciation at that level. Below this level, the conversion ratio remains one-for-one, giving the same downside exposure as the ordinary shares, excluding the income
difference.

Dividend enhanced convertible stock (“DECS”) are either preference shares or
subordinated bonds. These, like PERCS, mandatorily convert into ordinary shares at maturity, if not already converted. DECS give no significant loss protection and involve a risk of loss comparable to investing directly in equity securities, with
lower relative direct bond characteristics and interest rate exposure. As with PERCS, some of the appreciation potential is capped and in return, the investor receives an enhanced potential yield. Unlike PERCS, however, the investor’s
appreciation potential is not capped. Instead, the investor limits its ability to participate in appreciation within a range of prices.

Preferred Redeemable Increased Dividend Equity Security (“PRIDES”) are synthetic securities consisting of a forward contract to purchase the issuer’s underlying security and an interest
bearing deposit. Interest payments are made at regular intervals, and conversion into the underlying security is mandatory at maturity. Similar to convertible securities, PRIDES allow investors the potential to earn stable cash flows while still
participating in the appreciation of an underlying stock.

The Fund may also purchase convertible structured notes. Convertible
structured notes are fixed income debentures linked to equity. Convertible structured notes have the attributes of a convertible security; however, the investment bank that issued the convertible note assumes the credit risk associated with the
investment, rather than the issuer of the underlying common stock into which the note is convertible. Different companies may issue the fixed-income and convertible components, which may be purchased separately and at different times. The Fund
remains subject to the credit risk of the issuing investment bank.

Non-Convertible Income
Securities.    The Fund will also invest in non-convertible income securities. The Fund’s investments in non-convertible income securities may have fixed or variable principal payments and all types
of interest rate and dividend payment and reset terms, including fixed rate, adjustable rate, zero coupon, contingent, deferred, payment in kind and auction rate features.

High Yield Securities.    A substantial portion of the Fund’s assets may be invested in below investment grade (high yield) securities for either current income or capital
appreciation or both. These securities are rated Ba or lower by Moody’s or BB or lower by Standard & Poor’s or are unrated securities of comparable quality as determined by Calamos, the Fund’s investment adviser. The Fund may
invest in high yield securities of any rating. The Fund may, but currently does not intend to, invest up to 5% of its managed assets in distressed securities that are in default or the issuers of which are in
bankruptcy. Non-convertible debt securities rated below investment grade are commonly referred to as “junk bonds” and are considered speculative with respect to the issuer’s capacity to pay interest and repay principal.
Below investment-grade securities involve greater risk of loss, are subject to greater price volatility and are less liquid, especially during periods of economic uncertainty or change, than higher rated securities.

Foreign Securities.    Although the Fund primarily invests in securities of U.S. issuers, the Fund may invest
up to 25% of its net assets in securities of foreign issuers in developed and emerging markets, including debt and equity securities of corporate issuers and debt securities of government issuers. A foreign issuer is a foreign government or a
company organized under the laws of a foreign country. In analyzing the foreign issuers in which the Fund may invest, Calamos will generally consider a number of factors that may characterize the issuer’s economic ties to a particular foreign
country or region. Such factors may include any or all of the following: the characteristics of the economy in the principal country or countries in which the issuer sells it

26

goods and/or services; the stability of the currency in the issuer’s country of organization; the laws with respect to international trade and property rights in the issuer’s country of
organization; and the tax, accounting and regulatory requirements of the issuer’s country of organization.

Options
Writing.    The Fund may seek to generate income from option premiums by writing (selling) options. The Fund may write (sell) call options (i) on a portion of the equity securities (including equity securities obtainable
by the Fund through the exercise of its rights with respect to convertible securities it owns) in the Fund’s portfolio and (ii) on broad-based securities indices (such as the S&P 500 or MSCI EAFE) or certain ETFs (exchange traded
funds) that trade like common stocks but seek to replicate such market indices.

In addition, to seek to offset some of the
risk of a potential decline in value of certain long positions, the Fund may also purchase put options on individual securities, broad-based securities indices (such as the S&P 500 or MSCI EAFE), or certain ETFs that trade like common
stocks but seek to replicate market indices. See “—Options in General” below.

Options in
General.    The Fund may purchase and sell options on stocks, indices, rates, credit spreads or currencies. A call option, upon payment of a premium, gives the purchaser of the option the right to buy, and the seller the
obligation to sell, the underlying security, index or other instrument at the exercise price. A put option gives the purchaser of the option, upon payment of a premium, the right to sell, and the seller the obligation to buy, the underlying
security, index, or other instrument at the exercise price.

Certain options, known as “American style” options, may
be exercised at any time during the term of the option. Other options, known as “European style” options, may be exercised only on the expiration date of the option. The Fund expects that substantially all of the options written by the
Fund will be American style options.

The Fund is authorized to purchase and sell exchange listed options and over-the-counter
options (“OTC options”). Exchange listed options are issued by a regulated intermediary such as the Options Clearing Corporation (“OCC”), which guarantees the performance of the obligations of the parties to such options. In
addition, the Fund may purchase instruments structured by broker-dealers or investment banks that package or possess economic characteristics of options. The discussion below uses the OCC as an example, but is also applicable to other financial
intermediaries.

With certain exceptions, OCC issued and exchange listed options generally settle by physical delivery of the
underlying security or currency, although in the future cash settlement may become available. Index options are cash settled for the net amount, if any, by which the option is “in-the-money” (i.e., where the value of the underlying
instrument exceeds, in the case of a call option, or is less than, in the case of a put option, the exercise price of the option) at the time the option is exercised. Frequently, rather than taking or making delivery of the underlying instrument
through the process of exercising the option, listed options are closed by entering into offsetting purchase or sale transactions that do not result in ownership of the new option.

OTC options are purchased from or sold to securities dealers, financial institutions or other parties (“Counterparties”) through
direct bilateral agreement with the Counterparty. In contrast to exchange listed options, which generally have standardized terms and performance mechanics, all the terms of an OTC option, including such terms as method of settlement, term, exercise
price, premium, guarantees and security, are set by negotiation of the parties. The Fund may sell OTC options (other than OTC currency options) that are subject to a buy-back provision permitting the Fund to require the Counterparty to sell the
option back to the Fund at a formula price within seven days. The Fund expects generally to enter into OTC options that have cash settlement provisions, although it is not required to do so. The staff of the Commission currently takes the position
that OTC options purchased by a fund, and portfolio securities “covering” the amount of a fund’s obligation pursuant to an OTC option sold by it (or the amount of assets equal to the formula price for the repurchase of the option, if
any, less the amount by which the option is in-the-money) are illiquid. OTC options purchased by the Fund and any portfolio securities used to cover obligations pursuant to such options are not considered illiquid by Calamos for the purposes of the
Fund’s limitation on investments in illiquid securities.

The Fund will write call options and put options only if they
are “covered.” For example, a call option written by the Fund will require the Fund to hold the securities subject to the call (or securities convertible into

27

those securities without additional consideration) or to segregate cash or liquid assets sufficient to purchase and deliver the securities if the call is exercised. A call option sold by the Fund
on an index will require the Fund to own portfolio securities that correlate with the index or to segregate cash or liquid assets equal to the excess of the index value over the exercise price on a current basis. A put option written by the Fund
requires the Fund to segregate cash or liquid assets equal to the exercise price.

The principal factors affecting the market
value of a put or a call option include supply and demand, interest rates, the current market price of the underlying security or index in relation to the exercise price of the option, the volatility of the underlying security or index, and the time
remaining until the expiration date.

Rule 144A Securities.    The Fund may invest without limit
in certain securities, such as convertible and debt securities, that are typically purchased in transactions exempt from the registration requirements of the 1933 Act pursuant to Rule 144A under that Act. Rule 144A Securities may only be sold to
qualified institutional buyers, such as the Fund. Any resale of these securities must generally be effected through a sale that is registered under the 1933 Act or otherwise exempted or excepted from such registration requirements. Under the
supervision and oversight of the Fund’s Board of Trustees, Calamos will determine whether Rule 144A Securities are liquid. Typically, the Fund purchases Rule 144A Securities only if Calamos has determined them to be liquid. If any Rule 144A
Security held by the Fund should become illiquid, the value of the security may be reduced and a sale of the security may be more difficult.

Loans.    The Fund may invest in loan participations and other direct claims against a borrower. The corporate loans in which the Fund may invest primarily consist of direct
obligations of a borrower and may include debtor in possession financings pursuant to Chapter 11 of the U.S. Bankruptcy Code, obligations of a borrower issued in connection with a restructuring pursuant to Chapter 11 of the U.S. Bankruptcy Code,
leveraged buy-out loans, leveraged recapitalization loans, receivables purchase facilities, and privately placed notes. The Fund may invest in a corporate loan at origination as a co-lender or by acquiring in the secondary market participations in,
assignments of or novations of a corporate loan. By purchasing a participation, the Fund acquires some or all of the interest of a bank or other lending institution in a loan to a corporate or government borrower. The participations typically will
result in the Fund having a contractual relationship only with the lender not the borrower. The Fund will have the right to receive payments of principal, interest and any fees to which it is entitled only from the lender selling the participation
and only upon receipt by the lender of the payments from the borrower. Many such loans are secured, although some may be unsecured. Such loans may be in default at the time of purchase. Loans that are fully secured offer the Fund more protection
than an unsecured loan in the event of non-payment of scheduled interest or principal. However, there is no assurance that the liquidation of collateral from a secured loan would satisfy the corporate borrower’s obligation, or that the
collateral can be liquidated. Direct debt instruments may involve a risk of loss in case of default or insolvency of the borrower and may offer less legal protection to the Fund in the event of fraud or misrepresentation. In addition, loan
participations involve a risk of insolvency of the lending bank or other financial intermediary. The markets in such loans are not regulated by federal securities laws or the Commission.

Preferred Shares.    The Fund may invest in preferred stock. The preferred stock in which the Fund typically
will invest will be convertible securities. Preferred shares are equity securities, but they have many characteristics of fixed income securities, such as a fixed dividend payment rate and/or a liquidity preference over the issuer’s common
shares. However, because preferred stocks are equity securities, they may be more susceptible to risks traditionally associated with equity investments than the Fund’s fixed income securities.

REITs.    The Fund may invest in securities of REITs, including debt securities they may issue. REITs primarily
invest in income-producing real estate or real estate related loans or interests. REITs are generally classified as equity REITs, mortgage REITs or a combination of equity and mortgage REITs. Equity REITs invest the majority of their assets directly
in real property and derive income primarily from the collection of rents. Equity REITs can also realize capital gains by selling properties that have appreciated in value. Mortgage REITs invest the majority of their assets in real estate mortgages
and derive income from the collection of interest payments. REITs are not taxed on income distributed to shareholders provided they comply with the applicable requirements of the Code. The Fund will indirectly bear its proportionate share of any
management

28

and other expenses paid by REITs in which it invests in addition to the expenses paid by the Fund. Debt securities issued by REITs are, for the most part, general and unsecured obligations and
are subject to risks associated with REITs.

U.S. Government Securities.    U.S. government
securities in which the Fund invests include debt obligations of varying maturities issued by the U.S. Treasury or issued or guaranteed by an agency or instrumentality of the U.S. government, including the Federal Housing Administration, Federal
Financing Bank, Farmers Home Administration, Export-Import Bank of the United States, Small Business Administration, Government National Mortgage Association (“GNMA”), General Services Administration, Central Bank for Cooperatives, Federal
Farm Credit Banks, Federal Home Loan Banks, Federal Home Loan Mortgage Corporation (“FHLMC”), Federal National Mortgage Association (“FNMA”), Maritime Administration, Tennessee Valley Authority, District of Columbia Armory Board,
Student Loan Marketing Association, Resolution Fund Corporation and various institutions that previously were or currently are part of the Farm Credit System (which has been undergoing reorganization since 1987). Some U.S. government securities,
such as U.S. Treasury bills, Treasury notes and Treasury bonds, which differ only in their interest rates, maturities and times of issuance, are supported by the full faith and credit of the United States. Others are supported only by: (i) the
right of the issuer to borrow from the U.S. Treasury, such as securities of the Federal Home Loan Banks; (ii) the discretionary authority of the U.S. government to purchase the agency’s obligations, such as securities of the FNMA; or
(iii) only the credit of the issuer. No assurance can be given that the U.S. government will provide financial support in the future to U.S. government agencies, authorities or instrumentalities that are not supported by the full faith and
credit of the United States. Securities guaranteed as to principal and interest by the U.S. government, its agencies, authorities or instrumentalities include: (i) securities for which the payment of principal and interest is backed by an
irrevocable letter of credit issued by the U.S. government or any of its agencies, authorities or instrumentalities; and (ii) participations in loans made to non-U.S. governments or other entities that are so guaranteed. The secondary market
for certain of these participations is limited and, therefore, may be regarded as illiquid.

Zero Coupon
Securities.    The securities in which the Fund invests may include zero coupon securities, which are debt obligations that are issued or purchased at a significant discount from face value. The discount may approximate the
total amount of interest the security will accrue and compound over the period until maturity or the particular interest payment date at a rate of interest reflecting the market rate of the security at the time of issuance. Zero coupon securities do
not require the periodic payment of interest. These investments benefit the issuer by mitigating its need for cash to meet debt service, but generally require a higher rate of return to attract investors who are willing to defer receipt of cash.
These investments involve greater interest rate risk and may experience greater volatility in market value than U.S. government securities that make regular payments of interest. The Fund accrues income on these investments for tax and accounting
purposes, which is distributable to shareholders and which, because no cash is received at the time of accrual, may require the liquidation of other portfolio securities to satisfy the Fund’s distribution obligations or to reduce or eliminate
tax at the Fund level, in which case the Fund will forgo the purchase of additional income producing assets with these funds. Zero coupon U.S. government securities include STRIPS and CUBES, which are issued by the U.S. Treasury as component parts
of U.S. Treasury bonds and represent scheduled interest and principal payments on the bonds.

Equity
Securities.    Consistent with its objective, the Fund may invest in equity securities, including common and preferred stocks, warrants, rights and depository receipts. Equity securities, such as common stock, generally
represent an ownership interest in a company. Therefore, the Fund participates in the financial success or failure of any company in which it has an equity interest. Although equity securities have historically generated higher average returns than
fixed income securities, equity securities have also experienced significantly more volatility in those returns. An adverse event, such as an unfavorable earnings report, may depress the value of a particular equity security held by the Fund. Also,
the price of equity securities, particularly common stocks, are sensitive to general changes in economic conditions and movements in the stock market. A drop in the stock market may depress the price of equity securities held by the Fund. See also
“— Preferred Shares” below.

29

Other Investment Companies.    The Fund may invest in the
securities of other investment companies to the extent that such investments are consistent with the Fund’s investment objective and policies and are permissible under the 1940 Act. Under the 1940 Act, the Fund may not acquire the securities of
other domestic or non-U.S. investment companies if, as a result, (1) more than 10% of the Fund’s total assets would be invested in securities of other investment companies, (2) such purchase would result in more than 3% of the total
outstanding voting securities of any one investment company being held by the Fund, (3) more than 5% of the Fund’s total assets would be invested in any one investment company, or (4) such purchase would result in more than 10% of the
total outstanding voting securities of a registered closed-end investment company being held by the Fund. These limitations do not apply to, among other things, the purchase of shares of money market funds, of certain related funds or of funds with
exemptive relief, or of any investment company in connection with a merger, consolidation, reorganization or acquisition of substantially all the assets of another investment company, or to purchases of investment companies made in accordance with
SEC exemptive relief or rule.

The Fund, as a holder of the securities of other investment companies, will bear its pro
rata portion of the other investment companies’ expenses, including advisory fees. These expenses are in addition to the direct expenses of the Fund’s own operations. In addition, the Fund’s performance may be magnified positively or
negatively by virtue of its investment in other investment companies.

Temporary and Defensive
Investments.    Under unusual market or economic conditions or for temporary defensive purposes, the Fund may invest in a manner that is inconsistent with its principal investment strategies described herein. In those
situations, the Fund may invest up to 100% of its managed assets in securities issued or guaranteed by the U.S. government or its instrumentalities or agencies, certificates of deposit, bankers’ acceptances and other bank obligations,
commercial paper rated in the highest category by a nationally recognized statistical rating organization (“NRSRO”) or other fixed income securities deemed by Calamos to be consistent with a defensive posture, or may hold cash. The yield
on such securities may be lower than the yield on lower rated fixed income securities. During such periods, the Fund may not be able to achieve its investment objective.

Repurchase Agreements.    The Fund may enter into repurchase agreements with broker-dealers, member banks of the Federal Reserve System and other financial institutions.
Repurchase agreements are arrangements under which the Fund purchases securities and the seller agrees to repurchase the securities within a specific time and at a specific price. The repurchase price is generally higher than the Fund’s
purchase price, with the difference being income to the Fund. The counterparty’s obligations under the repurchase agreement are typically collateralized with U.S. Treasury and/or agency obligations with a market value of not less than 100% of
the obligations, valued daily. Collateral is typically held by the Fund’s custodian in a segregated, safekeeping account for the benefit of the Fund. Repurchase agreements afford the Fund an opportunity to earn income on temporarily available
cash. In the event of commencement of bankruptcy or insolvency proceedings with respect to the issuer of the repurchase agreement before repurchase of the security under a repurchase agreement, the Fund may encounter losses and delay and incur costs
before being able to sell the security. Such a delay may involve loss of interest or a decline in price of the security. If the court characterizes the transaction as a loan and the Fund has not perfected a security interest in the security, the
Fund may be required to return the security to the seller’s estate and be treated as an unsecured creditor of the seller. As an unsecured creditor, the Fund would be at risk of losing some or all of the principal and interest involved in the
transaction.

Lending of Portfolio Securities.    The Fund has authorized SSB as securities lending
agent to lend securities to registered broker-dealers or other institutional investors deemed by Calamos to be of good standing under agreements which require that the loans be secured continuously by collateral received in cash under the SSB
Agreement. Cash collateral held by SSB on behalf of the Fund may be credited against the amounts borrowed under the SSB Agreement, such that the Fund will effectively bear lower interest expense with respect to those borrowed amounts. Any amounts
credited against borrowings under the SSB Agreement would count against the Fund’s leverage limitations, unless otherwise covered in accordance with SEC Release IC-10666. Under the terms of the SSB Agreement, SSB will return the value of the
collateral to the borrower at the termination of the selected securities loan(s), which will eliminate the credit against the borrowings under the SSB Agreement and will increase the balance on which the Fund will pay interest. Under the terms of
the SSB Agreement, the Fund

30

will make a variable “net income” payment related to any collateral credited against the borrowings under the SSB Agreement which will be paid to the securities borrower, less any
payments due to the Fund or SSB under the terms of the SSB Agreement. The Fund does not use affiliated agents in managing its lending program. The Fund continues to be entitled to receive the equivalent of the interest or dividends paid by the
issuer on the securities loaned as well as the benefit of an increase and the detriment of any decrease in the market value of the securities loaned and would also receive compensation based on investment of the collateral, but bears the risk of
loss on any collateral so invested. The Fund would not, however, have the right to vote any securities having voting rights during the existence of the loan, but could seek to call the loan in anticipation of an important vote to be taken among
holders of the securities or of the giving or withholding of consent on a material matter affecting the investment.

As
with other extensions of credit, there are risks of delay in recovery or even loss of rights in the collateral should the borrower of the securities fail financially. The Fund remains liable for the return of the pledged collateral or cash of an
equivalent value. At no time would the value of the securities loaned exceed 33 1/3% of the value of the Fund’s managed assets. See “Description of Securities” for more information on lending of portfolio securities.

Portfolio Turnover.    Although the Fund does not purchase securities with a view to rapid turnover, there are
no limitations on the length of time that portfolio securities must be held. Portfolio turnover can occur for a number of reasons, including calls for redemption, general conditions in the securities markets, more favorable investment opportunities
in other securities, or other factors relating to the desirability of holding or changing a portfolio investment. The portfolio turnover rates may vary greatly from year to year. A high rate of portfolio turnover in the Fund would result in
increased transaction expense, which must be borne by the Fund. High portfolio turnover may also result in the realization of capital gains or losses and, to the extent net short-term capital gains are realized, any distributions resulting from such
gains will be considered ordinary income for federal income tax purposes.

Fundamental Investment
Restrictions.    As more fully described in the Fund’s statement of additional information, under the Fund’s fundamental investment restrictions, the Fund may not: (1) issue senior securities, except as
permitted by the 1940 Act and the rules and interpretive positions of the Commission thereunder; (2) borrow money, except as permitted by the 1940 Act and the rules and interpretive positions of the Commission thereunder; (3) invest in
real estate, except that the Fund may invest in securities of issuers that invest in real estate or interests therein, securities that are secured by real estate or interests therein, securities of real estate investment funds and mortgage-backed
securities; (4) make loans, except by the purchase of debt obligations, by entering into repurchase agreements or through the lending of portfolio securities and as otherwise permitted by the 1940 Act and the rules and interpretive positions of
the Commission thereunder; (5) invest in physical commodities or contracts relating to physical commodities; (6) act as an underwriter, except as it may be deemed to be an underwriter in a sale of securities held in its portfolio;
(7) make any investment inconsistent with the Fund’s classification as a diversified investment company under the 1940 Act and the rules and interpretive positions of the Commission thereunder; and (8) concentrate its investments in
securities of companies in any particular industry as defined in the 1940 Act and the rules and interpretive positions of the Commission thereunder. This description of the Fund’s fundamental investment restrictions is a summary only and to the
extent it differs from the discussion of fundamental investment restrictions contained in the Fund’s statement of additional information, the description in the statement of additional information controls.

These restrictions may not be changed without the approval of the holders of a majority of the Fund’s outstanding voting securities.
All other investment policies of the Fund are considered non-fundamental and may be changed by the Board of Trustees without prior approval of the Fund’s outstanding voting shares, although the Fund will give shareholders at least 60 days’
notice of any changes to the Fund’s investment objective. See “Investment Restrictions” on page S-23 of the Fund’s statement of additional information.

31

Conflicts of Interest

Conflicts of interest may arise from the fact that Calamos and its affiliates carry on substantial investment activities for other clients, in which the Fund does not have an interest, some of which may
have investment strategies similar to those of the Fund. Calamos or its affiliates may have financial incentives to favor certain of these accounts over the Fund. Any of their proprietary accounts or other customer accounts may compete with the Fund
for specific trades. Calamos or its affiliates may give advice and recommend securities to, or buy or sell securities for, other accounts and customers, which advice or securities recommended may differ from advice given to, or securities
recommended or bought or sold for, the Fund, even though their investment objectives may be the same as, or similar to, the Fund’s investment objective. When two or more clients advised by Calamos or its affiliates seek to purchase or sell the
same publicly traded securities, the securities actually purchased or sold will be allocated among the clients on a good faith equitable basis by Calamos in its discretion and in accordance with the clients’ various investment objectives and
Calamos’ procedures. In some cases, this system may adversely affect the price or size of the position the Fund may obtain or sell. In other cases, the Fund’s ability to participate in volume transactions may produce better execution for
the Fund.

Calamos will evaluate a variety of factors in determining whether a particular investment opportunity or strategy is
appropriate and feasible for a particular entity or account at a particular time, including, but not limited to, the following: (1) the nature of the investment opportunity taken in the context of the other investments available at the time;
(2) the liquidity of the investment relative to the needs of the particular entity or account; (3) the availability of the opportunity (i.e., size of obtainable position); (4) the transaction costs involved; and (5) the
investment or regulatory limitations applicable to the particular entity or account. Because these considerations may differ when applied to the Fund and relevant accounts under management in the context of any particular investment opportunity, the
Fund’s investment activities, on the one hand, and other managed accounts, on the other hand, may differ considerably from time to time. In addition, the Fund’s fees and expenses will differ from those of the other managed accounts.
Accordingly, investors should be aware that the Fund’s future performance and future performance of other accounts of Calamos may vary.

Situations may occur when the Fund could be disadvantaged because of the investment activities conducted by Calamos and its affiliates for their other accounts. Such situations may be based on, among
other things, the following: (1) legal or internal restrictions on the combined size of positions that may be taken for the Fund or the other accounts, thereby limiting the size of the Fund’s position; (2) the difficulty of
liquidating an investment for the Fund or the other accounts where the market cannot absorb the sale of the combined position; or (3) limits on co-investing in negotiated transactions under the 1940 Act.

Calamos and its principals, officers, employees, and affiliates may buy and sell securities or other investments for their own accounts
and may have actual or potential conflicts of interest with respect to investments made on the Fund’s behalf. As a result of differing trading and investment strategies or constraints, positions may be taken by principals, officers, employees,
and affiliates of Calamos that are the same as, different from, or made at a different time than positions taken for the Fund.

Calamos’ investment management fee is a percentage of the Fund’s managed assets, and Calamos’ investment management fee will be higher if the Fund sells additional common shares or employs
leverage. Accordingly, Calamos will benefit from the sale of additional common shares, preferred shares, or debt securities and may have an incentive to be more aggressive with respect to the use of leverage by the Fund.

LEVERAGE

The Fund may issue preferred shares or debt securities or borrow to increase its assets available for investment. As of January 31, 2020, the Fund had $31 million in borrowings outstanding under
the SSB Agreement, MRP Shares outstanding with an aggregate liquidation preference of $100 million and used approximately $254 million of collateral obtained through securities lending arrangements as an offset against borrowings under the
SSB Agreement, for a total of $385 million of leverage representing 32.5% of managed assets as of that date. The SSB Agreement provides for additional credit availability for the Fund, such that it

32

may borrow up to $430 million. Additional information regarding the Fund’s preferred shares is included below under “Mandatory Redeemable Preferred Shares.”

As a non-fundamental policy, the Fund may not issue preferred shares, borrow money and/or issue debt securities with an aggregate
liquidation preference and aggregate principal amount exceeding 38% of the Fund’s managed assets measured at the time of borrowing or issuance of the new securities. However, the Board of Trustees reserves the right to issue preferred shares or
debt securities or borrow to the extent permitted by the 1940 Act or under any order issued by the SEC.

The holders of
preferred shares will be entitled to receive a preferential liquidating distribution, which is expected to equal the original purchase price per preferred share plus accumulated and unpaid dividends, whether or not declared, before any distribution
of assets is made to holders of common shares. The 1940 Act requires that the holders of any preferred shares, voting separately as a single class, have the right to elect at least two Trustees at all times. The remaining Trustees will be elected by
holders of common shares and preferred shares, voting together as a single class. The holders of any preferred shares have the right to elect a majority of the Trustees at any time two years’ accumulated dividends on any preferred shares are
unpaid.

The Fund also may borrow money as a temporary measure for extraordinary or emergency purposes, including the payment
of dividends and the settlement of securities transactions, which otherwise might require untimely dispositions of the Fund’s holdings. When the Fund leverages its assets, the fees paid to Calamos for investment management services will be
higher than if the Fund did not leverage because Calamos’ fees are calculated based on the Fund’s managed assets, which include the proceeds of the issuance of preferred shares or debt securities or any outstanding borrowings.
Consequently, the Fund and Calamos may have differing interests in determining whether to leverage the Fund’s assets. The Fund’s Board of Trustees monitors any such potential conflicts of interest on an ongoing basis.

The Fund’s use of leverage is premised upon the expectation that the Fund’s leverage costs will be lower than the return the
Fund achieves on its investments with the leverage proceeds. Such difference in return may result from the Fund’s higher credit rating or the short-term nature of its borrowing compared to the lower credit quality, long-term nature of its
investments. Because Calamos seeks to invest the Fund’s managed assets (including the assets obtained from leverage) in a portfolio of potentially higher yielding investments or portfolio investments with the potential for capital appreciation,
the holders of common shares will be the beneficiaries of any incremental return but will bear the risk of loss on investments made with the leverage proceeds. Should the differential between the Fund’s return on its investments made with the
proceeds of leverage and the cost of the leverage narrow, the incremental return “pick up” will be reduced or the Fund may incur losses. If long-term interest rates rise without a corresponding increase in the yield on the Fund’s
portfolio investments or the Fund otherwise incurs losses on its investments, the Fund’s net asset value attributable to its common shares will reflect the decline in the value of portfolio holdings resulting therefrom.

Leverage creates risks which may adversely affect the return for the holders of common shares, including:

the likelihood of greater volatility in the net asset value and market price of common shares;

fluctuations in the dividend rates on any preferred shares borne by the Fund or in interest rates on borrowings and short-term debt;

increased operating costs, which are effectively borne by common shareholders, may reduce the Fund’s total return; and

the potential for a decline in the value of an investment acquired with borrowed funds, while the Fund’s obligations under such borrowing remains
fixed.

Leverage is a speculative technique that could adversely affect the returns to common shareholders.
Leverage can cause the Fund to lose money and can magnify the effect of any losses. To the extent the income or capital appreciation derived from securities purchased with funds received from leverage exceeds the cost of leverage, the Fund’s
return will be greater than if leverage had not been used. Conversely, if the income or capital appreciation from the securities purchased with such funds is not sufficient to cover the cost of leverage

33

or if the Fund incurs capital losses, the return of the Fund will be less than if leverage had not been used, and therefore the amount available for distribution to common shareholders as
dividends and other distributions will be reduced or potentially eliminated (or, in the case of distributions, will consist of return of capital).

Calamos may determine to maintain the Fund’s leveraged position if it expects that the long-term benefits to the Fund’s common shareholders of maintaining the leveraged position will outweigh
the current reduced return. Capital raised through the issuance of preferred shares or debt securities or borrowing will be subject to dividend payments or interest costs that may or may not exceed the income and appreciation on the assets
purchased. The issuance of preferred shares or debt or borrowing money may involve offering expenses and other costs and may limit the Fund’s freedom to pay dividends on common shares or to engage in other activities. See “Dividends and
Distributions on Common Shares; Automatic Dividend Reinvestment Plan — Dividends and Distributions on Common Shares.” The Fund also may be required to maintain minimum average balances in connection with borrowings or to pay a commitment
or other fee to maintain a line of credit; either of these requirements would increase the cost of borrowing over the stated interest rate. The Fund will pay (and common shareholders will bear) any costs and expenses relating to any borrowings by
the Fund, including the financial leverage described above, as well as any additional leverage incurred as a result of this offering and to the issuance and ongoing maintenance of preferred shares or debt securities (for example, the higher
management fee resulting from the use of any such leverage, and interest and/or dividend expense and ongoing maintenance). Net asset value will be reduced immediately following any additional offering of preferred shares or debt securities by the
costs of that offering paid by the Fund.

The Board reserves the right to change the amount and type of leverage that the Fund
uses, and reserves the right to implement changes to the Fund’s borrowings that it believes are in the long-term interests of the Fund and its shareholders, even if such changes impose a higher interest rate or other costs or impacts over the
intermediate, or short-term time period. There is no guarantee that the Fund will maintain leverage at the current rate, and the Board reserves the right to raise, decrease, or eliminate the Fund’s leverage exposure.

Under the 1940 Act, the Fund is not permitted to issue preferred shares unless immediately after such issuance the Fund has an asset
coverage of at least 200% of the liquidation value of the aggregate amount of outstanding preferred shares (i.e., such liquidation value may not exceed 50% of the value of the Fund’s total assets). Under the 1940 Act, the Fund may only issue
one class of senior securities representing equity. So long as preferred shares are outstanding, additional senior equity securities must rank on a parity with the preferred shares. In addition, the Fund is not permitted to declare any cash dividend
or other distribution on its common shares unless, at the time of such declaration, the net asset value of the Fund’s portfolio (determined after deducting the amount of such dividend or distribution) is at least 200% of such liquidation value.
Under the 1940 Act, the Fund is not permitted to incur indebtedness unless immediately after such borrowing the Fund has an asset coverage of at least 300% of the aggregate outstanding principal balance of indebtedness (i.e., such indebtedness may
not exceed 33 1/3% of the value of the Fund’s total assets). Under the 1940 Act, the Fund may only issue one class of senior securities representing indebtedness other than promissory notes or other evidences of indebtedness not intended to be
publicly distributed. Additionally, under the 1940 Act, the Fund generally may not declare any dividend or other distribution upon any class of its shares, or purchase any such shares, unless the aggregate indebtedness of the Fund has, at the time
of the declaration of any such dividend or distribution or at the time of any such purchase, an asset coverage of at least 300% after deducting the amount of such dividend, distribution, or purchase price, as the case may be, except that dividends
may be declared upon any preferred shares if such indebtedness has an asset coverage of at least 200% at the time of declaration thereof after deducting the amount of the dividend. This limitation does not apply to certain privately placed debt. In
general, the Fund may declare dividends on preferred shares as long as there is asset coverage of 200% after deducting the amount of the dividend. The holders of preferred shares or debt, if any, on the one hand, and the holders of the common
shares, on the other, may have interests that conflict with each other in certain situations. See “Description of Securities — Preferred Shares” and “Certain Provisions of the Agreement and Declaration of Trust and By-Laws,
Including Antitakeover Provisions.”

The Fund may be subject to certain restrictions on investments imposed by guidelines
of and covenants with one or more rating agencies, which may issue ratings for any debt securities or preferred shares issued by the

34

Fund in the future. These guidelines and covenants may impose asset coverage and portfolio composition requirements that are more stringent than those imposed by the 1940 Act. Certain types of
borrowings may result in the Fund being subject to covenants in credit agreements, including those relating to asset coverage, borrowing base and portfolio composition requirements and additional covenants that may affect the Fund’s ability to
pay dividends and distributions on common shares in certain instances. The Fund also may be required to pledge its assets to the lenders in connection with certain types of borrowings. Certain types of borrowing may involve the rehypothecation of
the Fund’s securities. Calamos does not anticipate that these covenants or restrictions would adversely affect its ability to manage the Fund’s portfolio in accordance with the Fund’s investment objective and policies. Due to these
covenants or restrictions, the Fund may be forced to liquidate investments at times and at prices that are not favorable to the Fund, or the Fund may be forced to forgo investments that Calamos otherwise views as favorable.

The extent to which the Fund employs leverage will depend on many factors, the most important of which are investment outlook, market
conditions and interest rates. Successful use of a leveraging strategy depends on Calamos’ ability to predict correctly interest rates and market movements. There is no assurance that a leveraging strategy will be successful during any period
in which it is employed.

Mandatory Redeemable Preferred Shares

On September 6, 2019-2020, the Fund completed a private placement of 1,330,000 Series A MRP Shares, 1,330,000 Series B MRP Shares and
1,340,000 Series C MRP Shares. Each MRP Share has a liquidation preference of $25.00, resulting in an aggregate liquidation preference of $100 million for all MRP Shares.

The holders of MRP Shares for the Fund (“MRP Shareholders”) are entitled to receive monthly cash dividends, payable on the first business day (a “Dividend Payment Date”) of each month
following issuance.

Subject to adjustment as described below under “MRP Shares Dividends,” the dividend rate per
annum (the “Applicable Rate”) for each series of MRP Share is as follows:

MRP Shares

Applicable Rate

Series A MRP Shares

3.70
%

Series B MRP Shares

4.00
%

Series C MRP Shares

4.24
%

The MRP Shares have a term redemption date of September 6, 2022 for the Series A MRP Shares,
September 6, 2024 for the Series B MRP Shares and September 6, 2027 for the Series C MRP Shares.

The MRP Shares have
been assigned a rating of “AA” by Fitch Ratings, Inc. (“Fitch”). If the ratings of the MRP Shares are downgraded, the Fund’s dividend expense may increase, as described below.

Liquidation Preference.    In the event of any voluntary or involuntary liquidation, dissolution or winding up
of the Fund, the MRP Shareholders will be entitled to receive a preferential liquidating distribution equal to $25.00 per MRP Share plus accrued and unpaid dividends, after satisfaction of claims of creditors of the Fund, but before any distribution
of assets is made to common shareholders.

MRP Shares Dividends.    If, on the first day of the
monthly dividend period immediately preceding a Dividend Payment Date (each such period a “Dividend Period”), a series of MRP Shares is rated no less than “A” by Fitch (and no less than the equivalent of such rating by some other
NRSRO, if any, other than Fitch, providing a rating for the MRP Shares pursuant to the request of the Fund), then the dividend rate for such period (the “Dividend Rate”) will be equal to the Applicable Rate for such series. If, on the
first day of a Dividend Period, the credit rating assigned on any date to a series of MRP Shares by Fitch (or some other NRSRO then rating any series of the outstanding MRP Share pursuant to the request of the Fund) is lower than a rating of
“A” by Fitch (or lower than the equivalent of such rating by such other rating agency), the Dividend Rate applicable to such

35

series of outstanding MRP Shares for such Dividend Period shall be the Applicable Rate plus the enhanced dividend amount (which shall not be cumulative) set opposite the lowest of such ratings in
the table below:

Fitch

Rating

Enhanced DividendAmount

“A-”

0.5
%

“BBB+” to “BBB-”

2.0
%

“BB+” or below

4.0
%

A 4.0% premium in addition to the Applicable Rate may apply when the Fund fails to maintain a current
credit rating, and a 5.0% premium may apply when the Fund fails to make timely payments with regard to the MRP Shares (subject to cure periods in each case).

Limitation on Common Share Distributions.    So long as any MRP Shares are outstanding, the Fund will not declare, pay or set apart for payment any dividend or other
distribution (other than non-cash distributions) with respect to Fund shares ranking junior to or on parity with the MRP Shares, unless (1) the Fund has satisfied the MRP Shares Overcollateralization Test (as defined below) on at least one
“valuation date” in the preceding 65 calendar days, (2) immediately after such transaction the Fund would satisfy the MRP Shares Asset Coverage Test (as defined below), (3) full cumulative dividends on the MRP Shares due on or
prior to the date of the transaction have been declared and paid to the MRP Shareholders and (4) the Fund has redeemed the full number of MRP Shares required to be redeemed by any provision for mandatory redemption or deposited sufficient
monies with the Fund’s paying agent for that purpose, subject to certain grace periods and exceptions.

MRP Shares
Asset Coverage Test: Asset coverage with respect to all outstanding senior securities and preferred shares, including the MRP Shares, determined in accordance with Section 18(h) of the 1940 Act, on the basis of values calculated as of a
time within 48 hours (not including Sundays or holidays) next preceding the time of determination, must be greater than or equal to 225%.

MRP Shares Overcollateralization Test: So long as Fitch or any other NRSRO is then rating any class of the outstanding MRP Shares pursuant to the request of the Fund, satisfaction of only those
overcollateralization ratios applicable to closed-end fund issuers with the same rating(s) as the Fund’s MRP Shares’ then-current rating(s) issued by Fitch or such other NRSRO by application of the applicable rating agency guidelines.

The terms of the MRP Shares and rights and preferences of the MRP Shareholders are set forth in the Statement of Preferences
of Series A Mandatory Redeemable Preferred Shares, Series B Mandatory Redeemable Preferred Shares and Series C Mandatory Redeemable Preferred Shares of the Fund (the “Statement of Preferences”).

Redemption.    The terms of the MRP Shares provide that: (i) the Fund may redeem the MRP Shares at its
option at the liquidation preference plus accrued and unpaid dividends and plus a make-whole premium, subject to notice and other requirements; (ii) the Fund is required to redeem the MRP Shares upon failure to satisfy the MRP Shares Asset
Coverage Test (tested monthly) or MRP Shares Overcollateralization Test (tested weekly), subject to cure periods; and (iii) the Fund is required to redeem the MRP Shares on the term redemption date of September 6, 2022 for the Series A MRP
Shares, September 6, 2024 for the Series B MRP Shares and September 6, 2027 for the Series C MRP Shares.

Voting
Rights.    Except as otherwise required in the prospectus, the governing documents of the Fund, or as otherwise required by applicable law, the Fund’s preferred shareholders, including the MRP Shareholders, have one vote
per share and vote together with the Fund’s common shareholders as a single class. The 1940 Act grants the holders of preferred stock the right to elect at least two Trustees at all times (the “Preferred Share Trustees”) and the
remaining Trustees will be elected by the holders of common stock and preferred stock voting as a single class. Except during any time when the Fund has failed to make a dividend or redemption payment in respect of MRP Shares outstanding, the MRP
Shareholders have agreed to vote in accordance with the recommendation of the Board of Trustees on any matter submitted to them for their vote or to the vote of shareholders of the Fund generally.

36

With respect to the MRP Shares, William R. Rybak and Virginia G. Breen were designated
by the Board of Trustees as the Preferred Share Trustees of the Fund. As of January 1, 2020, there were five other Trustees of the Fund, Ms. Stuckey and Messrs. Calamos, Neal, Toub and Wennlund. See “Management of the Fund” in the
Fund’s statement of additional information. The Fund’s preferred shareholders, including the MRP Shareholders, are entitled to elect a majority of the Trustees of the Fund during any period when (i) at least two years’
accumulated dividends on the preferred stock are due and unpaid or (ii) the preferred shares are otherwise entitled under the 1940 Act to elect a majority of the Trustees of the Fund. The MRP Shareholders have certain additional customary
voting rights pursuant to the MRP Shares governing documents and the 1940 Act.

The summary information regarding the MRP
Shares contained herein is qualified in its entirety by reference to the Statement of Preferences and other documents related to the terms and conditions and the offering of the MRP Shares.

Effects of Leverage

The SSB Agreement provides for credit availability
for the Fund, such that it may borrow up to $430 million. As of January 31, 2020, the Fund had utilized $285 million of the $430 million available under the SSB Agreement ($31 million in borrowings outstanding, and
$254 million in structural leverage consisting of collateral received from SSB in connection with securities on loan). Interest on the SSB Agreement is charged on the drawn amount at the rate of Overnight LIBOR plus 0.80%, payable monthly in
arrears. Interest on overdue amounts or interest on the drawn amount paid during an event of default will be charged at Overnight LIBOR plus 2.8%. These rates represent floating rates of interest that may change over time. The SSB Agreement has a
commitment fee of 0.1% of any undrawn amount. As of January 31, 2020, the interest rate charged under the SSB Agreement was 2.37%. “Net income” payments related to cash collateral in connection with securities lending were 1.18% of
the borrowed amount on an annualized basis as of that date, although this amount can vary based on changes in underlying interest rates.

The Fund’s MRP Shareholders are entitled to receive monthly cash dividends, at a currently effective dividend rate per annum for each series of MRP Share as follows (subject to adjustment as
described above in “Mandatory Redeemable Preferred Shares”): 3.70% for Series A MRP Shares, 4.00% for Series B MRP Shares and 4.24% for Series C MRP Shares.

To cover the interest expense on the borrowings under the SSB Agreement (including “net income” payments made with respect to borrowings offset by collateral for securities on loan) and the
dividend payments associated with the MRP Shares, based on rates in effect on January 31, 2020, the Fund’s portfolio would need to experience an annual return of 0.94% (before giving effect to expenses associated with senior securities).

Leverage is a speculative technique that could adversely affect the returns to common shareholders. Leverage can cause
the Fund to lose money and can magnify the effect of any losses. To the extent the income or capital appreciation derived from securities purchased with funds received from leverage exceeds the cost of leverage, the Fund’s return will be
greater than if leverage had not been used. Conversely, if the income or capital appreciation from the securities purchased with such funds is not sufficient to cover the cost of leverage or if the Fund incurs capital losses, the return of the Fund
will be less than if leverage had not been used, and therefore the amount available for distribution to common shareholders as dividends and other distributions will be reduced or potentially eliminated.

The Fund will pay, and common shareholders will effectively bear, any costs and expenses relating to any borrowings and to the issuance
and ongoing maintenance of preferred shares, including the MRP Shares, or debt securities. Such costs and expenses include the higher management fee resulting from the use of any such leverage, offering and/or issuance costs, and interest and/or
dividend expense and ongoing maintenance.

Certain types of borrowings may result in the Fund being subject to covenants in
credit agreements, including those relating to asset coverage, borrowing base and portfolio composition requirements and additional covenants that may affect the Fund’s ability to pay dividends and distributions on common shares in certain
instances. The Fund may also be required to pledge its assets to the lenders in connection with certain types of

37

borrowings. The Fund may be subject to certain restrictions on investments imposed by guidelines of and covenants with rating agencies for the preferred shares or short-term debt instruments
issued by the Fund. These guidelines and covenants may impose asset coverage or portfolio composition requirements that are more stringent than those imposed by the 1940 Act.

Because Calamos’ investment management fee is a percentage of the Fund’s managed assets, Calamos’ fee will be higher if the Fund is leveraged and Calamos will have an incentive to be more
aggressive and leverage the Fund. Consequently, the Fund and Calamos may have differing interests in determining whether to leverage the Fund’s assets. Any additional use of leverage by the Fund effected through new, additional or increased
credit facilities or the issuance of preferred shares would require approval by the Board of Trustees of the Fund.

The
following table illustrates the hypothetical effect on the return to a holder of the Fund’s common shares of the leverage obtained by us (and utilized on January 31, 2020). The purpose of this table is to assist you in understanding the
effects of leverage. As the table shows, leverage generally increases the return to common shareholders when portfolio return is positive and greater than the cost of leverage and decreases the return when the portfolio return is negative or less
than the cost of leverage. The figures appearing in the table are hypothetical and actual returns may be greater or less than those appearing in the table.

Assumed Portfolio Return (Net of Expenses)

(10.00
)% 
 
 
(5.00
)% 
 
 
0.00

 
 
5.00

 
 
10.00
%

Corresponding Common Share Return(1)

(16.19
)% 
 
 
(8.79
)% 
 
 
(1.39
)% 
 
 
6.01

 
 
13.41
%

(1)

Includes interest expense on the borrowings under the SSB Agreement, accrued at interest rates in effect on January 31, 2020 of 2.37%,
and dividend expense on the MRP Shares.

For further information about leveraging, see “Risk
Factors — Fund Risks — Leverage Risk.”

INTEREST RATE TRANSACTIONS

In order to reduce the interest rate risk inherent in the Fund’s underlying investments and capital structure, the Fund, if
Calamos deems market conditions favorable, may enter into over-the-counter interest rate swap, cap or floor transactions to attempt to protect itself from increasing dividend or interest expenses on its leverage and to hedge portfolio securities
from interest rate changes. Fixed-for-floating interest rate swaps involve the Fund’s agreement with the swap counterparty to pay a fixed rate payment in exchange for the counterparty agreeing to pay the Fund a payment at a variable rate that
is expected to approximate the rate of any variable rate payment obligation on the Fund’s leverage. The payment obligations would be based on the notional amount of the swap.

The Fund may use an interest rate cap, which would require it to pay a premium to the counterparty and would entitle it, to the extent
that a specified variable rate index exceeds a predetermined fixed rate, to receive from the counterparty payment of the excess amount based on a stated notional amount. There can be no assurance that the Fund will use interest rate transactions or
that, if used, their use will be beneficial to the Fund.

The Fund will usually enter into swaps or caps on a net basis; that
is, the two payment streams will be netted out in a cash settlement on the payment date or dates specified in the instrument, with the Fund receiving or paying, as the case may be, only the net amount of the two payments. The Fund intends to
segregate with its custodian cash or liquid securities having a value at least equal to the Fund’s net payment obligations under any swap transaction, marked-to-market daily.

The use of interest rate swaps and caps is a highly specialized activity that involves investment techniques and risks different from
those associated with ordinary portfolio security transactions. Depending on the state of interest rates in general, the Fund’s use of interest rate swaps or caps could enhance or harm the overall performance of the Fund’s common shares.
To the extent that there is a decline in interest rates for maturities equal to the remaining maturity on the Fund’s fixed rate payment obligation under the interest rate swap or equal to the remaining term of the interest rate cap, the value
of the swap or cap (which initially has a value of zero) could decline, and could result in a decline in the net asset value of the common shares. If, on the other hand, such rates were to increase, the value of the swap or cap could increase, and
thereby increase the net asset value

38

of the common shares. As interest rate swaps or caps approach their maturity, their positive or negative value due to interest rate changes will approach zero.

In addition, if the short-term interest rates effectively received by the Fund during the term of an interest rate swap are lower than the
Fund’s fixed rate of payment on the swap, the swap will increase the Fund’s operating expenses and reduce common share net earnings. For example, if the Fund were to enter into one or more interest rate swaps in a notional amount
equal to 75% of its outstanding margin loan under which the Fund would receive a short-term swap rate of 1.57% and pay a fixed swap rate of 1.54% over the term of the swap, the swap would effectively increase Fund expenses and reduce Fund common
share net earnings by less than 0.01% as a percentage of net assets attributable to common shareholders and less than 0.01% as a percentage of managed assets.

If, on the other hand, the short-term interest rates effectively received by the Fund are higher than the Fund’s fixed rate of payment on the interest rate swap, the swap would enhance common share
net earnings. The example above is purely for illustrative purposes and is not predictive of the actual percentage of the Fund’s leverage that will be hedged by a swap, the actual fixed rates that the Fund will pay under the swap (which will
depend on market interest rates for the applicable maturities at the time the Fund enters into swaps) or the actual short-term rates that the Fund will receive on any swaps (which fluctuate frequently during the term of the swap, and may change
significantly from initial levels), or the actual impact such swaps will have on the Fund’s expenses and common share net earnings. In either case, the swap would have the effect of reducing fluctuations in the Fund’s cost of leverage due
to changes in short term interest rates during the term of the swap.

Buying interest rate caps could enhance the
performance of the Fund’s common shares by limiting certain leverage expenses. Buying interest rate caps could also increase the operating expenses of the Fund and decrease the net earnings of the common shares in the event that interest rates
decline or stay the same or the premium paid by the Fund to the counterparty exceeds the additional amount the Fund would have been required to pay on its preferred shares due to increases in short-term interest rates during the term of the cap had
it not entered into the cap agreement. The Fund has no current intention of selling an interest rate swap or cap. The Fund will monitor any interest rate swaps or caps with a view to ensuring that it remains in compliance with the federal income tax
requirements for qualification as a regulated investment company.

Interest rate swaps and caps do not involve the delivery
of securities or other underlying assets or principal. Accordingly, the risk of loss with respect to interest rate swaps and caps is limited to the net amount of interest payments that the Fund is contractually obligated to make or, if applicable,
any premium paid by the Fund. If the counterparty defaults, the Fund would not be able to use the anticipated net receipts under the swap or cap to offset the dividend or interest payments on the Fund’s leverage or offset certain losses in its
portfolio. Depending on whether the Fund would be entitled to receive net payments from the counterparty on the swap or cap, which in turn would depend on the general state of short-term interest rates at that point in time, such a default could
negatively impact the performance of the common shares.

The Fund will not enter into an interest rate swap or cap
transaction with any counterparty that Calamos believes does not have the financial resources to honor its obligation under the interest rate swap or cap transaction. Further, Calamos will continually monitor the financial stability of a
counterparty to an interest rate swap or cap transaction in an effort to proactively protect the Fund’s investments.

In
addition, at the time the interest rate swap or cap transaction reaches its scheduled termination date, there is a risk that the Fund will not be able to obtain a replacement transaction or that the terms of the replacement will not be as favorable
as on the expiring transaction. If this occurs, it could have a negative impact on the performance of the Fund’s common shares.

When preferred shares are outstanding, the Fund may choose or be required to redeem some or all preferred shares or prepay any borrowings. This redemption or prepayment would likely result in the Fund
seeking to terminate early all or a portion of any swap or cap transaction. Such early termination of a swap could result in a termination payment by or to the Fund. An early termination of a cap could result in a termination payment to the Fund.

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RISK FACTORS

Investing in any of our securities involves risk, including the risk that you may receive little or no return on your investment or
even that you may lose part or all of your investment. Therefore, before investing in any of our securities you should consider carefully the following risks, as well as any risk factors included in the applicable prospectus supplement.

Fund Risks

The principal risks are presented in alphabetical order to facilitate finding particular risks and comparing them with other funds. Each risk summarized below is considered a “principal risk” of
investing in the Fund, regardless of the order in which it appears.

General.    The Fund is a
diversified, closed-end management investment company designed primarily as a long-term investment and not as a trading tool. The Fund invests primarily in a diversified portfolio of convertible securities
and non-convertible income securities. An investment in the Fund’s common shares may be speculative and it involves a high degree of risk. The Fund is not a complete investment program. Due to the uncertainty in all investments, there
can be no assurance that the Fund will achieve its investment objective.

Antitakeover
Provisions.    The Fund’s Agreement and Declaration of Trust and By-Laws include provisions that could limit the ability of other entities or persons to acquire control of the Fund or to change the composition of its
Board of Trustees. Such provisions could limit the ability of shareholders to sell their shares at a premium over prevailing market prices by discouraging a third party from seeking to obtain control of the Fund. These provisions include staggered
terms of office for the Trustees, advance notice requirements for shareholder proposals, and super-majority voting requirements for certain transactions with affiliates, converting the Fund to an open-end investment company or a merger, asset sale
or similar transaction. Holders of preferred shares have voting rights in addition to and separate from the voting rights of common shareholders with respect to certain of these matters. Holders of any preferred shares, voting separately as a single
class, have the right to elect at least two Trustees at all times. See “Description of Securities — Preferred Shares” and “Certain Provisions of the Agreement and Declaration of Trust and By-Laws, Including Antitakeover
Provisions.” The holders of preferred shares or debt, if any, on the one hand, and the holders of the common shares, on the other, may have interests that conflict with each other in certain situations, including conflicts that relate to the
fees and expenses of the Fund. For more information on potential conflicts of interest between holders of common shares and holders of preferred shares, see “Leverage Risk” above.

Convertible Securities Risk.    The value of a convertible security is influenced by both the yield of
non-convertible securities of comparable issuers and by the value of the underlying common stock. The value of a convertible security viewed without regard to its conversion feature (i.e., strictly on the basis of its yield) is sometimes referred to
as its “investment value.” A convertible security’s investment value tends to decline as prevailing interest rate levels increase. Conversely, a convertible security’s investment value tends to increase as prevailing interest
rate levels decline.

However, a convertible security’s market value tends to reflect the market price of the common
stock of the issuing company when that stock price is greater than the convertible security’s “conversion price.” The conversion price is defined as the predetermined price at which the convertible security could be exchanged for the
associated stock. As the market price of the underlying common stock declines, the price of the convertible security tends to be influenced more by the yield of the convertible security and changes in interest rates. Thus, the convertible security
may not decline in price to the same extent as the underlying common stock. In the event of a liquidation of the issuing company, holders of convertible securities would be paid before the company’s common stockholders.

Counterparty and Settlement Risk.    Trading options, futures contracts, swaps and other derivative financial
instruments entails credit risk with respect to the counterparties. Such instruments when traded over the counter do not include the same protections as may apply to trading derivatives on organized exchanges. Substantial losses may arise from the
insolvency, bankruptcy or default of a counterparty and risk of settlement default of

40

parties with whom it trades securities. This risk may be heightened during volatile market conditions. Settlement mechanisms in emerging markets are generally less developed and reliable than
those in more developed countries thus increasing the risks.

In the past, broker-dealers and other financial institutions have
experienced extreme financial difficulty, sometimes resulting in bankruptcy of the institution. Although Calamos monitors the creditworthiness of the Fund’s counterparties, there can be no assurance that the Fund’s counterparties will not
experience similar difficulties, possibly resulting in losses to the Fund. If a counterparty becomes bankrupt, or otherwise fails to perform its obligations under a derivative contract due to financial difficulties, the Fund may experience
significant delays in obtaining any recovery under the derivative contract in a bankruptcy or other reorganization proceeding. The Fund may obtain only a limited recovery or may obtain no recovery in such circumstances. Material exposure to a single
or small group of counterparties increases the Fund’s counterparty risk.

Credit Risk.    An
issuer of a fixed income security could be downgraded or default. If the Fund holds securities that have been downgraded, or that default on payment, the Fund’s performance could be negatively affected.

Cybersecurity Risk.    Investment companies, such as the Fund, and their service providers are exposed to
operational and information security risks resulting from cyberattacks, which may result in financial losses to a fund and its shareholders. Cyber-attacks include, among other behaviors, stealing or corrupting data maintained online or digitally,
denial of service attacks on websites, “ransomware” that renders systems inoperable until ransom is paid, the unauthorized release of confidential information, or various other forms of cybersecurity breaches. Cyber-attacks affecting the
Fund or the Adviser, custodian, transfer agent, distributor, administrator, intermediaries, trading counterparties, and other third-party service providers may adversely impact the Fund or the companies in which the Fund invests, causing the
Fund’s investments to lose value or to prevent a shareholder redemption or purchase from clearing in a timely manner.

Debt Securities Risk.    The Fund may invest in debt securities, including corporate bonds and high yield
securities. In addition to the risks described elsewhere in this prospectus (such as high yield securities risk and interest rate risk), debt securities are subject to certain additional risks, including issuer risk and reinvestment risk. Issuer
risk is the risk that the value of debt securities may decline for a number of reasons which directly relate to the issuer, such as management performance, leverage and reduced demand for the issuer’s goods and services. Reinvestment risk is
the risk that income from the Fund’s portfolio will decline if the Fund invests the proceeds from matured, traded or called bonds at market interest rates that are below the Fund portfolio’s current earnings rate. A decline in income could
affect the market price of the Fund’s common shares or the overall return of the Fund.

Default
Risk.    Default risk refers to the risk that a company that issues a convertible or debt security will be unable to fulfill its obligations to repay principal and interest. The lower a debt security is rated, the greater its
default risk. As a result, the Fund may incur cost and delays in enforcing its rights against the defaulting issuer.

Derivatives Risk.    Generally, derivatives are financial contracts whose value depends on, or is derived from,
the value of an underlying asset, reference rate or index, and may relate to individual debt or equity instruments, interest rates, currencies or currency exchange rates, commodities, related indices and other assets. The Fund may utilize a variety
of derivative instruments including, but not limited to, interest rate swaps, convertible securities, synthetic convertible instruments, options on individual securities, index options, long calls, covered calls, long puts, cash-secured short puts
and protective puts for hedging, risk management and investment purposes. The Fund’s use of derivative instruments involves investment risks and transaction costs to which the Fund would not be subject absent the use of these instruments and,
accordingly, may result in losses greater than if they had not been used. The use of derivative instruments may have risks including, among others, liquidity risk, interest rate risk, volatility risk, credit risk, management risk and counterparty
risk. The use of derivatives may also have the following risks:

Correlation Risk. Imperfect correlation between the
value of derivative instruments and the underlying assets of the Fund creates the possibility that the loss on such instruments may be greater than the gain in the value of the underlying assets in the Fund’s portfolio.

41

Duration Mismatch Risk. The duration of a derivative instrument may be
significantly different than the duration of the related liability or asset.

Volatility Risk. Risk may arise in
connection with the use of derivative instruments from volatility of interest rates and the prices of reference instruments.

Leverage Risk. The derivative investments in which the Fund may invest will give rise to forms of financial leverage, which
may magnify the risk of owning such instruments. Derivatives generally involve leverage in the sense that the investment exposure created by the derivatives may be significantly greater than the Fund’s initial investment in the derivative.
Accordingly, if the Fund enters into a derivative transaction, it could lose substantially more than the principal amount invested.

Additionally, as a closed-end investment company registered with the SEC, the Fund is subject to the federal securities laws, including the 1940 Act, the rules thereunder, and various SEC and SEC staff
interpretive positions. In accordance with these laws, rules and positions, the Fund may “set aside” liquid assets (often referred to as “asset segregation”), or engage in other SEC or staff-approved measures, to
“cover” open positions with respect to certain portfolio management techniques, such as engaging in reverse repurchase agreements, dollar rolls, entering into credit default swaps or futures contracts, or purchasing securities on a
when-issued or delayed delivery basis, that may be considered senior securities under the 1940 Act. The Fund intends to cover its derivative positions by maintaining an amount of cash or liquid securities in a segregated account equal to the face
value of those positions and by offsetting derivative positions against one another or against other assets to manage the effective market exposure resulting from derivatives in its portfolio. To the extent that the Fund does not segregate liquid
assets or otherwise cover its obligations under such transactions, such transactions will be treated as senior securities representing indebtedness for purposes of the requirement under the 1940 Act that the Fund may not enter into any such
transactions if the Fund’s borrowings would thereby exceed 33 1/3% of its managed assets, less all liabilities and indebtedness of the Fund not represented by senior securities. However, these transactions, even if covered, may represent a form
of economic leverage and will create risks. In addition, these segregation and coverage requirements could result in the Fund maintaining securities positions that it would otherwise liquidate, segregating assets at a time when it might be
disadvantageous to do so or otherwise restricting portfolio management. Such segregation and cover requirements will not limit or offset losses on related positions.

Regulatory Risk. The enforceability of agreements underlying hedging transactions may depend on compliance with applicable statutory and other regulatory requirements and, depending on the identity
of the counterparty, applicable international requirements. New or amended regulations may be imposed by the CFTC, the SEC, the Federal Reserve or other financial regulators, other governmental regulatory authorities or self-regulatory organizations
that supervise the financial markets that could adversely affect the Fund. In particular, these agencies are empowered to promulgate a variety of new rules pursuant to recently enacted financial reform legislation in the United States. The Fund also
may be adversely affected by changes in the enforcement or interpretation of existing statues and rules by these governmental regulatory authorities or self-regulatory organizations.

In addition, the securities and futures markets are subject to comprehensive statutes, regulations and margin requirements. For instance,
the Dodd–Frank Wall Street Reform and Consumer Protection Act (“Dodd-Frank Act”) could have an adverse effect on the Fund’s ability to use derivative instruments. The Dodd-Frank Act is designed to impose stringent regulation on
the over-the-counter derivatives market in an attempt to increase transparency and accountability and provides for, among other things, new clearing, execution, margin, reporting, recordkeeping, business conduct, disclosure, position limit, minimum
net capital and registration requirements. Although the CFTC has released final rules relating to clearing, execution, reporting, risk management, compliance, position limit, anti-fraud, consumer protection, portfolio reconciliation, documentation,
recordkeeping, business conduct, margin requirements and registration requirements under the Dodd-Frank Act, many of the provisions are subject to further final rulemaking, and thus the Dodd-Frank Act’s ultimate impact remains unclear. New
regulations could, among other things, restrict the Fund’s ability to engage in derivatives transactions (for example, by making certain types of derivatives transactions no longer available to our funds),

42

increase the costs of using these instruments (for example, by increasing margin, capital or reporting requirements) and/or make them less effective and, as a result, the Fund may be unable to
execute its investment strategy. Limits or restrictions applicable to the counterparties with which the Fund engages in derivative transactions could also prevent the Fund from using these instruments, affect the pricing or other factors relating to
these instruments or may change availability of certain investments. It is unclear how the regulatory changes will affect counterparty risk.

General Derivative Risks. Derivatives also involve the risk of mispricing or improper valuation and the risk that changes in the value of a derivative may not correlate perfectly with an underlying
asset, interest rate or index. Suitable derivative transactions may not be available in all circumstances and there can be no assurance that the Fund will engage in these transactions to reduce exposure to other risks when that would be beneficial.
Furthermore, the skills needed to employ derivatives strategies are different from those needed to select portfolio securities and, in connection with such strategies, the Fund may make predictions with respect to market conditions, liquidity,
currency movements, market values, interest rates and other applicable factors, which may be inaccurate. Thus, the use of derivative investments may require the Fund to sell or purchase portfolio securities at inopportune times or for prices below
or above the current market values, may limit the amount of appreciation the Fund can realize on an investment or may cause the Fund to hold a security that it might otherwise want to sell. Tax rules governing the Fund’s transactions in
derivative instruments may affect whether gains and losses recognized by the Fund are treated as ordinary or capital, accelerate the recognition of income or gains to the Fund, defer losses to the Fund, and cause adjustments in the holding periods
of the Fund’s securities, thereby affecting, among other things, whether capital gains and losses are treated as short-term or long-term. These rules could therefore affect the amount, timing and/or character of distributions to shareholders.
In addition, there may be situations in which the Fund elects not to use derivative investments that result in losses greater than if they had been used. Amounts paid by the Fund as premiums and cash or other assets held in margin accounts with
respect to the Fund’s derivative investments would not be available to the Fund for other investment purposes, which may result in lost opportunities for gain.

Emerging Markets Risk.    Investments in foreign securities may include investments in securities of foreign issuers located in less developed countries, which are sometimes
referred to as emerging markets. Emerging market countries may have relatively unstable governments and economies based on only a few industries, which may cause greater instability. The value of emerging market securities will likely be
particularly sensitive to changes in the economies of such countries. These countries are also more likely to experience higher levels of inflation, deflation or currency devaluations, which could adversely affect the value of the Fund’s
investments and hurt those countries’ economies and securities markets. Securities issued in these countries may be more volatile and less liquid than securities issued in foreign countries with more developed economies or markets. Loss may
also result from the imposition of exchange controls, confiscations and other government restrictions, or from problems in share registration, settlement, custody, or other operational risks.

Foreign Securities Risk.    Investments in non-U.S. issuers may involve unique risks compared to investing in
securities of U.S. issuers. These risks are more pronounced to the extent that the Fund invests a significant portion of its non-U.S. investments in one region or in the securities of emerging market issuers. See also “— Emerging
Markets Risk” below. These risks may include:

less information may be available about non-U.S. issuers or markets due to less rigorous disclosure or accounting standards or regulatory practices in
foreign jurisdictions;

many non-U.S. markets are smaller, less liquid and more volatile. In a changing market, Calamos may not be able to sell the Fund’s portfolio
securities at times, in amounts and at prices it considers reasonable;

an adverse effect of currency exchange rate changes or controls on the value of the Fund’s investments;

the economies of non-U.S. countries may grow at slower rates than expected or may experience a downturn or recession;

economic, political and social developments may adversely affect the securities markets in foreign jurisdictions, including expropriation and
nationalization;

43

the difficulty in obtaining or enforcing a court judgment in non-U.S. countries;

restrictions on foreign investments in non-U.S. jurisdictions;

difficulties in effecting the repatriation of capital invested in non-U.S. countries;

withholding and other non-U.S. taxes may decrease the Fund’s return; and

dividend income the Fund receives from foreign securities may not be eligible for the special tax treatment applicable to qualified dividend income.

There may be less publicly available information about non-U.S. markets and issuers than is available with
respect to U.S. securities and issuers. Non-U.S. companies generally are not subject to accounting, auditing and financial reporting standards, practices and requirements comparable to those applicable to U.S. companies. The trading markets for most
non-U.S. securities are generally less liquid and subject to greater price volatility than the markets for comparable securities in the United States. The markets for securities in certain emerging markets are in the earliest stages of their
development. Even the markets for relatively widely traded securities in certain non-U.S. markets, including emerging market countries, may not be able to absorb, without price disruptions, a significant increase in trading volume or trades of a
size customarily undertaken by institutional investors in the United States. Additionally, market making and arbitrage activities are generally less extensive in such markets, which may contribute to increased volatility and reduced liquidity.

Economies and social and political conditions in individual countries may differ unfavorably from those in the United States.
Non-U.S. economies may have less favorable rates of growth of gross domestic product, rates of inflation, currency valuation, capital reinvestment, resource self-sufficiency and balance of payments positions. Many countries have experienced
substantial, and in some cases extremely high, rates of inflation for many years. Inflation and rapid fluctuations in inflation rates have had, and may continue to have, very negative effects on the economies and securities markets of certain
emerging market countries. Unanticipated political or social developments may also affect the values of the Fund’s investments and the availability to the Fund of additional investments in such countries.

Based upon the Fund’s test for determining whether an issuer is a “foreign issuer” as described above, it is possible that
an issuer of securities in which the Fund invests could be organized under the laws of a foreign country, yet still conduct a substantial portion of its business in the U.S. or have substantial assets in the U.S. In this case, such a “foreign
issuer” may be subject to the market conditions in the U.S. to a greater extent than it may be subject to the market conditions in the country of its organization. See “— Non-U.S. Government Obligation Risk.”

High Yield Securities Risk.    The Fund may invest in high yield securities of any rating. Investment in high
yield securities involves substantial risk of loss. Below investment grade non-convertible debt securities or comparable unrated securities are commonly referred to as “junk bonds” and are considered predominantly speculative with respect
to the issuer’s ability to pay interest and principal and are susceptible to default or decline in market value due to adverse economic and business developments. The market values for high yield securities tend to be very volatile, and these
securities are less liquid than investment grade debt securities. For these reasons, your investment in the Fund is subject to the following specific risks:

increased price sensitivity to changing interest rates and to a deteriorating economic environment;

greater risk of loss due to default or declining credit quality;

adverse company specific events are more likely to render the issuer unable to make interest and/or principal payments; and

if a negative perception of the high yield market develops, the price and liquidity of high yield securities may be depressed. This negative perception
could last for a significant period of time.

Securities rated below investment grade are speculative
with respect to the capacity of the issuer to pay interest and repay principal in accordance with the terms of such securities. A rating of “Ba1” from Moody’s

44

means that the issue so rated can have speculative elements and is subject to substantial credit risk. Standard & Poor’s assigns a rating of “BB+” to issues that are less
vulnerable to nonpayment than other speculative issues, but nonetheless subject to major ongoing uncertainties or exposure to adverse business, financial, or economic conditions which could lead to the obligor’s inadequate capacity to meet its
financial commitment on the obligation. A rating of “C” from Moody’s means that the issue so rated can be regarded as having extremely poor prospects of ever attaining any real investment standing. Standard & Poor’s
assigns a rating of “C” to issues that are currently highly vulnerable to nonpayment, and the “C” rating may be used to cover a situation in which a bankruptcy petition has been filed or similar action taken, but payments on the
obligation are being continued (a “C” rating is also assigned to a preferred stock issue in arrears on dividends or sinking fund payments, but that is currently paying). See the statement of additional information for a description of
Moody’s and Standard & Poor’s ratings.

Adverse changes in economic conditions are more likely to lead to a
weakened capacity of a high yield issuer to make principal payments and interest payments than an investment grade issuer. The principal amount of high yield securities outstanding has proliferated in the past decade as an increasing number of
issuers have used high yield securities for corporate financing. An economic downturn could severely affect the ability of highly leveraged issuers to service their debt obligations or to repay their obligations upon maturity. Similarly, downturns
in profitability in specific industries could adversely affect the ability of high yield issuers in those industries to meet their obligations. The market values of lower quality debt securities tend to reflect individual developments of the issuer
to a greater extent than do higher quality securities. Factors having an adverse impact on the market value of lower quality securities may have an adverse effect on the Fund’s net asset value and the market value of its common shares. In
addition, the Fund may incur additional expenses to the extent it is required to seek recovery upon a default in payment of principal or interest on its portfolio holdings. In certain circumstances, the Fund may be required to foreclose on an
issuer’s assets and take possession of its property or operations. In such circumstances, the Fund would incur additional costs in disposing of such assets and potential liabilities from operating any business acquired.

The secondary market for high yield securities may not be as liquid as the secondary market for more highly rated securities, a factor
which may have an adverse effect on the Fund’s ability to dispose of a particular security. There are fewer dealers in the market for high yield securities than for investment grade obligations. The prices quoted by different dealers may vary
significantly and the spread between the bid and asked price is generally much larger than for higher quality instruments.

Because investors generally perceive that there are greater risks associated with lower quality debt securities of the type in which the
Fund may invest a portion of its assets, the yields and prices of such securities may tend to fluctuate more than those for higher rated securities. In the lower quality segments of the debt securities market, changes in perceptions of issuers’
creditworthiness tend to occur more frequently and in a more pronounced manner than do changes in higher quality segments of the debt securities market, resulting in greater yield and price volatility.

If the Fund invests in high yield securities that are rated “C” or below, the Fund will incur significant risk in addition to
the risks associated with investments in high yield securities and corporate loans. Distressed securities frequently do not produce income while they are outstanding. The Fund may purchase distressed securities that are in default or the issuers of
which are in bankruptcy. The Fund may be required to bear certain extraordinary expenses in order to protect and recover its investment. The Fund also will be subject to significant uncertainty as to when and in what manner and for what value the
obligations evidenced by the distressed securities will eventually be satisfied.

Interest Rate
Risk.    In addition to the risks described above, debt securities, including high yield securities, are subject to certain risks, including:

if interest rates go up, the value of debt securities in the Fund’s portfolio generally will decline;

during periods of declining interest rates, the issuer of a security may exercise its option to prepay principal earlier than scheduled, forcing the
Fund to reinvest in lower yielding securities. This is known as

45

call or prepayment risk. Debt securities frequently have call features that allow the issuer to repurchase the security prior to its stated maturity. An issuer may redeem an obligation if the
issuer can refinance the debt at a lower cost due to declining interest rates or an improvement in the credit standing of the issuer;

during periods of rising interest rates, the average life of certain types of securities may be extended because of slower than expected principal
payments. This may lock in a below market interest rate, increase the estimated period until the security is paid in full and reduce the value of the security. This is known as extension risk;

rising interest rates could result in an increase in the cost of the Fund’s leverage and could adversely affect the ability of the Fund to meet
asset coverage requirements with respect to leverage;

variable rate securities generally are less sensitive to interest rate changes but may decline in value if their interest rates do not rise as much, or
as quickly, as interest rates in general. When the Fund holds variable rate securities, a decrease in market interest rates will adversely affect the income received from such securities and the NAV of the Fund’s shares; and

the risks associated with rising interest rates may be particularly acute in the current market environment because market interest rates are currently
near historically low levels. Thus, the Fund currently faces a heightened level of interest rate risk, especially since the Federal Reserve Board has ended its quantitative easing program and has begun, and may continue, to raise interest rates. To
the extent the Federal Reserve Board continues to raise interest rates, there is a risk that interest rates across the financial system may rise. Increases in volatility and interest rates in the fixed-income market may expose the Fund to heightened
interest rate risk.

Many financial instruments use or may use a floating rate based on LIBOR, which is
the offered rate for short-term Eurodollar deposits between major international banks. On July 27, 2019-2020, the head of the United Kingdom’s Financial Conduct Authority announced a desire to phase out the use of LIBOR by the end of 2021.
There remains uncertainty regarding the future utilization of LIBOR and the nature of any replacement rate. As such, the potential effect of a transition away from LIBOR on the Fund or the financial instruments in which the Fund invests cannot yet
be determined.

Leverage Risk.    The Fund has issued indebtedness and preferred shares and may
borrow money or issue debt securities as permitted by the 1940 Act. As of January 31, 2020, the Fund has leverage in the form of borrowings under the SSB Agreement and outstanding MRP Shares. Leverage is the potential for the Fund to
participate in gains and losses on an amount that exceeds the Fund’s investment. The borrowing of money or issuance of debt securities and preferred shares represents the leveraging of the Fund’s common shares. As a non-fundamental policy,
the Fund may not issue preferred shares or borrow money and/or issue debt securities with an aggregate liquidation preference and aggregate principal amount exceeding 38% of the Fund’s managed assets as measured at the time of borrowing or
issuance of the new securities. However, the Board of Trustees reserves the right to issue preferred shares or debt securities or borrow to the extent permitted by the 1940 Act and the Fund’s policies. See “Leverage.”

Leverage creates risks which may adversely affect the return for the holders of common shares, including:

the likelihood of greater volatility in the net asset value and market price of the Fund’s common shares;

fluctuations in the dividend rates on any preferred shares borne by the Fund or in interest rates on borrowings and short-term debt;

increased operating costs, which are effectively borne by common shareholders, may reduce the Fund’s total return; and

the potential for a decline in the value of an investment acquired with borrowed funds, while the Fund’s obligations under such borrowing or
preferred shares remain fixed.

In addition, the rights of lenders and the holders of preferred shares and
debt securities issued by the Fund will be senior to the rights of the holders of common shares with respect to the payment of dividends or to the

46

payment of assets upon liquidation. Holders of preferred shares have voting rights in addition to and separate from the voting rights of common shareholders. See “Description of Securities
— Preferred Shares” and “Certain Provisions of the Agreement and Declaration of Trust and By-Laws, Including Antitakeover Provisions.” The holders of preferred shares or debt, if any, on the one hand, and the holders of the
common shares, on the other, may have interests that conflict in certain situations.

The Fund’s use of leverage is
premised upon the expectation that the Fund’s preferred share dividends or borrowing cost will be lower than the return the Fund achieves on its investments with the proceeds of the issuance of preferred shares or debt securities or borrowing.
Such difference in return may result from the Fund’s higher credit rating or the short-term nature of its borrowing compared to the lower credit quality, long-term nature of its investments. Because Calamos seeks to invest the Fund’s
managed assets (including the assets obtained from leverage) in a portfolio of potentially higher yielding investments or portfolio investments with the potential for capital appreciation, the holders of common shares will be the beneficiaries of
any incremental return but will bear the risk of loss on investments made with the leverage proceeds. Should the differential between the Fund’s return on its investments made with the proceeds of leverage and the cost of the leverage narrow,
the incremental return “pick up” will be reduced or the Fund may incur losses. If long-term interest rates rise without a corresponding increase in the yield on the Fund’s portfolio investments or the Fund otherwise incurs losses on
its investments, the Fund’s net asset value attributable to its common shareholders will reflect the decline in the value of portfolio holdings resulting therefrom.

Leverage is a speculative technique that could adversely affect the returns to common shareholders. Leverage can cause the Fund to lose money and can magnify the effect of any losses. To the extent the
income or capital appreciation derived from securities purchased with funds received from leverage exceeds the cost of leverage, the Fund’s return will be greater than if leverage had not been used. Conversely, if the income or capital
appreciation from the securities purchased with such funds is not sufficient to cover the cost of leverage or if the Fund incurs capital losses, the return of the Fund will be less than if leverage had not been used, and therefore the amount
available for distribution to common shareholders as dividends and other distributions will be reduced or potentially eliminated.

The Fund will pay, and common shareholders will effectively bear, any costs and expenses relating to any borrowings and to the issuance and ongoing maintenance of preferred shares or debt securities. Such
costs and expenses include the higher management fee resulting from the use of any such leverage, offering and/or issuance costs, and interest and/or dividend expense and ongoing maintenance. These conditions may, directly or indirectly, result in
higher leverage costs to common shareholders.

Certain types of borrowings may result in the Fund being subject to
covenants in credit agreements, including those relating to asset coverage, borrowing base and portfolio composition requirements and additional covenants that may affect the Fund’s ability to pay dividends and distributions on common shares in
certain instances. The Fund may also be required to pledge its assets to the lenders in connection with certain types of borrowings. The Fund may be subject to certain restrictions on investments imposed by guidelines of and covenants with rating
agencies which may issue ratings for the preferred shares or short-term debt instruments issued by the Fund. These guidelines and covenants may impose asset coverage or portfolio composition requirements that are more stringent than those imposed by
the 1940 Act. If the Fund’s ability to make dividends and distributions on its common shares is limited, such limitation could, under certain circumstances, impair the ability of the Fund to maintain its qualification for taxation as a
regulated investment company or to reduce or eliminate tax at the Fund level, which would have adverse tax consequences for common shareholders. To the extent that the Fund is required, in connection with maintaining 1940 Act asset coverage
requirements or otherwise, or elects to redeem any preferred shares or debt securities or prepay any borrowings, the Fund may need to liquidate investments to fund such redemptions or prepayments. Liquidation at times of adverse economic conditions
may result in capital loss and reduce returns to common shareholders.

The Board reserves the right to change the amount and
type of leverage that the Fund uses, and reserves the right to implement changes to the Fund’s borrowings that it believes are in the long-term interests of the Fund and its shareholders, even if such changes impose a higher interest rate or
other costs or impacts over the

47

intermediate, or short-term time period. There is no guarantee that the Fund will maintain leverage at the current rate, and the Board reserves the right to raise, decrease, or eliminate the
Fund’s leverage exposure. See “Prospectus Summary — Use of Leverage by the Fund.”

Because Calamos’
investment management fee is a percentage of the Fund’s managed assets, Calamos’ fee will be higher if the Fund is leveraged and Calamos will have an incentive to be more aggressive and leverage the Fund. Consequently, the Fund and Calamos
may have differing interests in determining whether to leverage the Fund’s assets. Any additional use of leverage by the Fund effected through new, additional or increased credit facilities or the issuance of preferred shares would require
approval by the Board of Trustees of the Fund. In considering whether to approve the use of additional leverage through those means, the Board would be presented with all relevant information necessary to make a determination whether or not
additional leverage would be in the best interests of the Fund, including information regarding any potential conflicts of interest.

Liquidity Risk.    The Fund may invest without limit in securities that, at the time of investment, are illiquid (i.e., any investment that the Fund reasonably expects cannot be
sold or disposed of in current market conditions in seven calendar days or less without the sale or disposition significantly changing the market value of the investment). Illiquid securities may be difficult to dispose of at a fair price at the
times when the Fund believes it is desirable to do so. Investment of the Fund’s assets in illiquid securities may restrict the Fund’s ability to take advantage of market opportunities. The market price of illiquid securities generally is
more volatile than that of more liquid securities, which may adversely affect the price that the Fund pays for or recovers upon the sale of illiquid securities. Illiquid securities are also more difficult to value and may be fair valued by the
Board, in which case Calamos’ judgment may play a greater role in the valuation process. The risks associated with illiquid securities may be particularly acute in situations in which the Fund’s operations require cash and could result in
the Fund borrowing to meet its short-term needs or incurring losses on the sale of illiquid securities. Under adverse market or economic conditions, the secondary market for securities could contract further, independent of any specific adverse
changes in the condition of a particular issuer, and these instruments may become illiquid. As a result, the Fund could find it more difficult to sell these securities or may be able to sell the securities only at prices lower than if such
securities were widely traded. Prices realized upon the sale of such lower rated or unrated securities, under these circumstances, may be less than the prices used in calculating the Fund’s net asset value. The Fund may also invest without
limitation in securities that have not been registered for public sale, but that are eligible for purchase and sale by certain qualified institutional buyers.

Management Risk.    Calamos’ judgment about the attractiveness, relative value or potential appreciation of a particular sector, security or investment strategy may prove
to be incorrect.

Market Disruption Risk.    Certain events have a disruptive effect on the
securities markets, such as terrorist attacks, war and other geopolitical events, earthquakes, storms and other disasters. The Fund cannot predict the effects of similar events in the future on the U.S. economy or any foreign economy. High yield
securities tend to be more volatile than higher rated debt securities so that these events and any actions resulting from them may have a greater impact on the prices and volatility of high yield securities than on higher rated securities.

Non-Convertible Income Securities Risk.    The Fund will also invest
in non-convertible income securities. The Fund’s investments in non-convertible income securities may have fixed or variable principal payments and all types of interest rate and dividend payment and reset terms, including
fixed rate, adjustable rate, zero coupon, contingent, deferred, payment in kind and auction rate features. Recent events in the fixed-income markets, including the potential impact of the Federal Reserve Board tapering its quantitative easing
program, may expose the Fund to heightened interest rate risk and volatility as a result of a rise in interest rates. In addition, the Fund is subject to the risk that interest rates may exhibit increased volatility, which could cause the
Fund’s net asset value to fluctuate more. A decrease in fixed-income market maker capacity may act to decrease liquidity in the fixed-income markets and act to further increase volatility, affecting the Fund’s return.

Non-U.S. Government Obligation Risk.    An investment in debt obligations of non-U.S. governments and their
political subdivisions involves special risks that are not present in corporate debt obligations. The non-U.S. issuer of the sovereign debt or the non-U.S. governmental authorities that control the repayment of the debt may be unable or unwilling to
repay principal or interest when due, and the Fund may have limited recourse in the

48

event of a default. During periods of economic uncertainty, the market prices of sovereign debt may be more volatile than prices of debt obligations of U.S. issuers.

Recent Market Events.    In the past decade, financial markets throughout the world have experienced increased
volatility, depressed valuations, decreased liquidity and heightened uncertainty and turmoil. This turmoil resulted in unusual and extreme volatility in the equity and debt markets, in the prices of individual securities and in the world economy.
Events that have contributed to these market conditions include, but are not limited to, major cybersecurity events, geopolitical events (including wars and terror attacks), measures to address budget deficits, downgrading of sovereign debt,
declines in oil and commodity prices, dramatic changes in currency exchange rates, and public sentiment. In addition, many governments and quasi-governmental entities throughout the world have responded to the turmoil with a variety of significant
fiscal and monetary policy changes, including, but not limited to, direct capital infusions into companies, new monetary programs and dramatically lower interest rates.

While the extreme volatility and disruption that U.S. and global markets experienced for an extended period of time beginning in 2007 and 2008 has generally subsided, uncertainty and periods of volatility
remain, and risks to a robust resumption of growth persist. Federal Reserve policy, including with respect to certain interest rates and the decision to begin tapering its quantitative easing policy, may adversely affect the value, volatility and
liquidity of dividend and interest paying securities. Market volatility, rising interest rates and/or a return to unfavorable economic conditions may lower the Fund’s performance or impair the Fund’s ability to achieve its investment
objective.

In June 2019-2020, the United Kingdom approved a referendum to leave the European Union (“EU”)
(“Brexit”). On March 29, 2019-2020, the United Kingdom formally notified the European Council of its intention to leave the EU and commenced the formal process of withdrawing from the EU. The withdrawal agreement entered into between the
United Kingdom and the EU entered into force on January 31, 2020, at which time the United Kingdom ceased to be a member of the EU. Following the withdrawal, there will be an eleven-month transition period, ending December 31, 2020, during
which the United Kingdom will negotiate its future relationship with the EU. Brexit has resulted in volatility in European and global markets and could have negative long-term impacts on financial markets in the United Kingdom and throughout Europe.
There is considerable uncertainty about the potential consequences for Brexit, how it will be conducted, how negotiations of trade agreements will proceed, and how the financial markets will react, and as this process unfolds, markets may be further
disrupted. Given the size and importance of the United Kingdom’s economy, uncertainty about its legal, political, and economic relationship with the remaining member states of the EU may continue to be a source of instability. Moreover, other
countries may seek to withdraw from the European Union and/or abandon the euro, the common currency of the EU.

A number of
countries in Europe have suffered terror attacks, and additional attacks may occur in the future. Ukraine has experienced ongoing military conflict; this conflict may expand and military attacks could occur elsewhere in Europe. Europe has also been
struggling with mass migration from the Middle East and Africa. The ultimate effects of these events and other socio-political or geographical issues are not known but could profoundly affect global economies and markets.

As a result of political and military actions undertaken by Russia, the U.S. and the EU have instituted sanctions against certain Russian
officials and companies. These sanctions and any additional sanctions or other intergovernmental actions that may be undertaken against Russia in the future may result in the devaluation of Russian currency, a downgrade in the country’s credit
rating, and a decline in the value and liquidity of Russian securities. Such actions could result in a freeze of Russian securities, impairing the ability of a fund to buy, sell, receive, or deliver those securities. Retaliatory action by the
Russian government could involve the seizure of US and/or European residents’ assets, and any such actions are likely to impair the value and liquidity of such assets. Any or all of these potential results could have an adverse/recessionary
effect on Russia’s economy. All of these factors could have a negative effect on the performance of funds that have significant exposure to Russia.

In addition, policy and legislative changes in the United States and in other countries are changing many aspects of financial regulation. The impact of these changes on the markets, and the practical
implications for

49

market participants, may not be fully known for some time. Widespread disease and virus epidemics could likewise be highly disruptive, adversely affecting individual companies, sectors,
industries, markets, currencies, interest and inflation rates, credit ratings, investor sentiment, and other factors affecting the value of the Fund’s investments.

REIT Risk.    Investing in REITs involves certain unique risks in addition to those risks associated with investing in the real estate industry in general. An equity REIT may be
affected by changes in the value of the underlying properties owned by the REIT. A mortgage REIT may be affected by changes in interest rates and the ability of the issuers of its portfolio mortgages to repay their obligations. REITs are dependent
upon the skills of their managers and are not diversified. REITs are generally dependent upon maintaining cash flows to repay borrowings and to make distributions to shareholders and are subject to the risk of default by lessees or borrowers. REITs
whose underlying assets are concentrated in properties used by a particular industry, such as health care, are also subject to risks associated with such industry.

REITs (especially mortgage REITs) are also subject to interest rate risks. When interest rates decline, the value of a REIT’s investment in fixed rate obligations can be expected to rise. Conversely,
when interest rates rise, the value of a REIT’s investment in fixed rate obligations can be expected to decline. If the REIT invests in adjustable rate mortgage loans the interest rates on which are reset periodically, yields on a REIT’s
investments in such loans will gradually align themselves to reflect changes in market interest rates. This causes the value of such investments to fluctuate less dramatically in response to interest rate fluctuations than would investments in fixed
rate obligations.

REITs may have limited financial resources, may utilize significant amounts of leverage, may trade less
frequently and in a limited volume and may be subject to more abrupt or erratic price movements than larger company securities. Historically, REITs have been more volatile in price than the larger capitalization stocks included in
Standard & Poor’s 500 Stock Index.

Risks Associated with Options.    The Fund may
use options, including on the Fund’s convertible securities or during the creation of synthetic convertible instruments. There are several risks associated with transactions in options. For example, there are significant differences between the
securities markets and options markets that could result in an imperfect correlation among these markets, causing a given transaction not to achieve its objectives. A decision as to whether, when and how to use options involves the exercise of skill
and judgment, and even a well-conceived transaction may be unsuccessful to some degree because of market behavior or unexpected events. The Fund’s ability to utilize options successfully will depend on Calamos’ ability to predict pertinent
market movements, which cannot be assured.

The Fund intends to seek to generate income from option premiums by writing
(selling) options. The Fund may write (sell) call options (i) on a portion of the equity securities (including securities that are convertible into equity securities) in the Fund’s portfolio, (ii) on a portion of the equity securities
the Fund has a right to receive upon conversion of a convertible security that it owns at the time it writes the call, and (iii) on broad-based securities indices (such as the S&P 500 or MSCI EAFE) or certain ETFs that trade like common
stocks but seek to replicable such market indices. All call options sold by the Fund must be “covered.” For example, a call option written by the Fund will require the Fund to hold the securities subject to the call (or securities
convertible into the needed securities without additional consideration) or to segregate cash or liquid assets sufficient to purchase and deliver the securities if the call is exercised. Even though the Fund will receive the option premium to help
protect it against loss, a call option sold by the Fund exposes the Fund during the term of the option to possible loss of opportunity to realize appreciation in the market price of the underlying security or instrument and may require the Fund to
hold a security or instrument that it might otherwise have sold. The Fund may purchase and sell put options on individual securities and securities indices. In selling put options, there is a risk that the Fund may be required to buy the underlying
security at a disadvantageous price above the market price. A put option written by the Fund requires the Fund to segregate cash or liquid assets equal to the exercise price minus any margin the Fund is required to post.

Rule 144A Securities Risk.    The Fund may invest in securities that are issued and sold through transactions
under Rule 144A of the Securities Act of 1933. Under the supervision and oversight of the Board, Calamos will

50

determine whether Rule 144A Securities are illiquid. If qualified institutional buyers are unwilling to purchase these Rule 144A Securities, the percentage of the Fund’s assets invested in
illiquid securities would increase. Typically, the Fund purchases Rule 144A Securities only if the Fund’s adviser has determined them to be liquid. If any Rule 144A Security held by the Fund should become illiquid, the value of the security may
be reduced and a sale of the security may be more difficult.

Synthetic Convertible Instruments
Risk.    The value of a synthetic convertible instrument may respond differently to market fluctuations than a convertible instrument because a synthetic convertible instrument is composed of two or more separate securities,
each with its own market value. In addition, if the value of the underlying common stock or the level of the index involved in the convertible component falls below the exercise price of the warrant or option, the warrant or option may lose all
value. Synthetic convertible instruments created by other parties have the same attributes of a convertible security; however, the issuer of the synthetic convertible instrument assumes the credit risk associated with the investment, rather than the
issuer of the underlying equity security into which the instrument is convertible. Investing in synthetic convertible instruments also involves the risk that the Fund does not achieve the investment exposure desired by Calamos. The Fund remains
subject to the credit risk associated with the counterparty creating the synthetic convertible instrument.

Tax
Risk.    The Fund may invest in certain securities, such as certain convertible securities and high yield securities, for which the federal income tax treatment may not be clear or may be subject to re-characterization by the
IRS. It could be more difficult for the Fund to comply with certain federal income tax requirements applicable to regulated investment companies if the tax characterization of the Fund’s investments is not clear or if the tax treatment of the
income from such investments was successfully challenged by the IRS. In addition, the tax treatment of the Fund may be affected by future interpretations of the Code and changes in the tax laws and regulations, all of which may apply with
retroactive effect. See “Certain Federal Income Tax Matters.”

Certain of the Fund’s investment practices may be
subject to special and complex federal income tax provisions that may, among other things, (i) disallow, suspend or otherwise limit the allowance of certain losses or deductions, (ii) convert tax-advantaged, long-term capital gains and
qualified dividend income into higher taxed short-term capital gain or ordinary income, (iii) increase ordinary income distributions, (iv) convert an ordinary loss or a deduction into a capital loss (the deductibility of which is more
limited), (v) cause the Fund to recognize income or gain without a corresponding receipt of cash, (vi) adversely affect the timing as to when a purchase or sale of stock or securities is deemed to occur, and (vii) adversely alter the
characterization of certain complex financial transactions. The Fund will monitor its transactions and may make certain tax elections where applicable in order to mitigate the effect of these provisions, if possible.

Additional Risks to Common Shareholders

Generally, an investment in common shares is subject to the following risks:

Diminished Voting Power and Excess Cash Risk.    The voting power of current shareholders will be diluted to the extent that such shareholders do not purchase shares in any
future common share offerings or do not purchase sufficient shares to maintain their percentage interest. In addition, if we are unable to invest the proceeds of such offering as intended, our per share distribution may decrease (or may consist of
return of capital) and we may not participate in market advances to the same extent as if such proceeds were fully invested as planned.

Interest Rate Transactions Risk.    The Fund may enter into an interest rate swap, cap or floor transaction to attempt to protect itself from increasing dividend or interest
expenses on its leverage resulting from increasing short-term interest rates and to hedge its portfolio securities. A decline in interest rates may result in a decline in the value of the swap or cap, which may result in a decline in the net asset
value of the Fund.

Depending on the state of interest rates in general, the Fund’s use of interest rate swap or cap
transactions could enhance or harm the overall performance of the common shares. To the extent there is a decline in interest rates, the value of the interest rate swap or cap could decline, and could result in a decline in the net asset value

51

of the common shares. In addition, if the counterparty to an interest rate swap or cap defaults, the Fund would not be able to use the anticipated net receipts under the swap or cap to offset the
dividend or interest payments on the Fund’s leverage or offset certain losses in its portfolio.

Depending on whether the
Fund would be entitled to receive net payments from the counterparty on the swap or cap, which in turn would depend on the general state of short-term interest rates at that point in time, such a default could negatively impact the performance of
the common shares. In addition, at the time an interest rate swap or cap transaction reaches its scheduled termination date, there is a risk that the Fund would not be able to obtain a replacement transaction or that the terms of the replacement
would not be as favorable as on the expiring transaction. If either of these events occurs, it could have a negative impact on the performance of the common shares.

If the Fund fails to maintain a required 200% asset coverage of the liquidation value of any outstanding preferred shares or if the Fund loses its rating on its preferred shares or fails to maintain other
covenants with respect to the preferred shares, the Fund may be required to redeem some or all of the preferred shares. Similarly, the Fund could be required to prepay the principal amount of any debt securities or other borrowings. Such redemption
or prepayment would likely result in the Fund seeking to terminate early all or a portion of any swap or cap transaction. Early termination of a swap could result in a termination payment by or to the Fund. Early termination of a cap could result in
a termination payment to the Fund. The Fund intends to segregate with its custodian cash or liquid securities having a value at least equal to the Fund’s net payment obligations under any swap transaction, marked-to-market daily.

Currently, certain categories of interest rate swaps are subject to mandatory clearing, and more are expected to be cleared in the future.
The counterparty risk for cleared derivatives is generally lower than for uncleared OTC derivative transactions because generally a clearing organization becomes substituted for each counterparty to a cleared derivative contract and, in effect,
guarantees the parties’ performance under the contract as each party to a trade looks only to the clearing house for performance of financial obligations. However, there can be no assurance that a clearing house, or its members, will satisfy
the clearing house’s obligations to the Fund.

Market Discount Risk.    The Fund’s common
shares have traded both at a premium and at a discount relative to net asset value. Common shares of closed-end investment companies frequently trade at a discount from net asset value, but in some cases trade above net asset value. The risk of the
Fund’s common shares trading at a discount is a risk separate from the risk of a decline in the Fund’s net asset value as a result of investment activities. The Fund’s net asset value may be reduced immediately following this offering
by the offering costs for common shares or other securities, which will be borne entirely by all common shareholders.

Whether
shareholders will realize a gain or loss upon the sale of the Fund’s common shares depends upon whether the market value of the shares at the time of sale is above or below the price the shareholder paid, taking into account transaction costs
for the shares, and is not directly dependent upon the Fund’s net asset value. Because the market value of the Fund’s common shares will be determined by factors such as the relative demand for and supply of the shares in the market,
general market conditions and other factors beyond the control of the Fund, the Fund cannot predict whether its common shares will trade at, below or above the Fund’s net asset value, or below or above the public offering price for the common
shares.

Market Impact Risk.    The sale of our common shares (or the perception that such sales may
occur) may have an adverse effect on prices in the secondary market for our common shares. An increase in the number of common shares available may put downward pressure on the market price for our common shares. These sales also might make it more
difficult for us to sell additional equity securities in the future at a time and price we deem appropriate.

Reduction
of Leverage Risk.    We have previously taken, and may in the future take, action to reduce the amount of leverage employed by the Fund. Reduction of the leverage employed by the Fund, including by redemption of preferred
shares, will in turn reduce the amount of assets available for investment in portfolio securities. This reduction in leverage may negatively impact our financial performance, including our ability to sustain current levels of distributions on common
shares.

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The Board reserves the right to change the amount and type of leverage that the Fund uses,
and reserves the right to implement changes to the Fund’s borrowings that it believes are in the best interests of the Fund, even if such changes impose a higher interest rate or other costs or impacts over the intermediate, or short-term time
period. There is no guarantee that the Fund will maintain leverage at the current rate, and the Board reserves the right to raise, decrease, or eliminate the Fund’s leverage exposure.

Additional Risks to Senior Security Holders

Additional risks of investing in senior securities include the following:

Generally, an investment in preferred shares (including exchange-listed preferred shares) or debt securities (collectively, “senior securities”) is subject to the following risks:

Decline in Net Asset Value Risk.    A material decline in our NAV may impair our ability to maintain
required levels of asset coverage for outstanding borrowings or any debt securities or preferred shares.

Early Redemption
Risk.    The Fund may voluntarily redeem preferred shares or may be forced to redeem preferred shares to meet regulatory requirements and the asset coverage requirements of the preferred shares. Such redemptions may be at a
time that is unfavorable to holders of the preferred shares.

Inflation Risk.    Inflation is the
reduction in the purchasing power of money resulting from an increase in the price of goods and services. Inflation risk is the risk that the inflation adjusted or “real” value of an investment in preferred stock or debt securities or the
income from that investment will be worth less in the future. As inflation occurs, the real value of the preferred stock or debt securities and the dividend payable to holders of preferred stock or interest payable to holders of debt securities
declines.

Interest Rate Risk.    Rising market interest rates could impact negatively the
value of our investment portfolio, reducing the amount of assets serving as asset coverage for the senior securities. Rising market interest rates could also reduce the value of the Fund’s senior securities.

Market Discount Risk.    The market price of exchange-listed preferred shares that the Fund may issue may also
be affected by such factors as the Fund’s use of leverage, dividend stability, portfolio credit quality, liquidity, and the Fund’s dividends paid (which are, in turn, affected by expenses), call protection for portfolio securities and
interest rate movements.

Ratings and Asset Coverage Risk.    To the extent that senior securities
are rated, a rating does not eliminate or necessarily mitigate the risks of investing in our senior securities, and a rating may not fully or accurately reflect all of the credit and market risks associated with that senior security. A rating agency
could downgrade the rating of our shares of preferred stock or debt securities, which may make such securities less liquid in the secondary market, though potentially with higher resulting interest rates. If a rating agency downgrades the rating
assigned to a senior security, we may alter our portfolio or redeem the senior security. We may voluntarily redeem senior securities under certain circumstances.

Secondary Market Risk.    The market value of exchange-listed preferred shares that the Fund may issue will be determined by factors such as the relative demand for and supply
of the preferred shares in the market, general market conditions and other factors beyond the control of the Fund. It may be difficult to predict the trading patterns of preferred shares, including the effective costs of trading. There is a risk
that the market for preferred shares may be thinly traded and relatively illiquid compared to the market for other types of securities.

Senior Leverage Risk.    Preferred shares will be junior in liquidation and with respect to distribution rights to debt securities and any other borrowings. Senior securities
representing indebtedness may constitute a substantial lien and burden on preferred shares by reason of their prior claim against our income and against our net assets in liquidation. We may not be permitted to declare dividends or other
distributions with respect to any series of preferred shares unless at such time we meet applicable asset coverage requirements and the payment of principal or interest is not in default with respect to any borrowings.

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MANAGEMENT OF THE FUND

Trustees and Officers

The Fund’s Board of Trustees provides broad supervision over the affairs of the Fund. The officers of the Fund are responsible for
the Fund’s operations. Currently, there are seven Trustees of the Fund, one of whom is an “interested person” of the Fund (as defined in the 1940 Act) and six of whom are not “interested persons.” The names and business
addresses of the trustees and officers of the Fund and their principal occupations and other affiliations during the past five years are set forth under “Management of the Fund” in the statement of additional information.

Investment Adviser

The Fund’s investments are managed by Calamos, 2020 Calamos Court, Naperville, Illinois 60563. On January 31, 2020, Calamos
managed approximately $26.6 billion in assets of individuals and institutions. Calamos is a wholly-owned subsidiary of Calamos Investments LLC (“CILLC”). Calamos Asset Management, Inc. (“CAM” or the “Company”) is
the sole manager of CILLC and a wholly-owned subsidiary of Calamos Partners LLC (“CPL” or “Parent”). As of January 31, 2020, approximately 22% of the outstanding equity interest of CILLC is owned by CAM and the remaining
approximately 78% of CILLC is owned by CPL and John P. Calamos, Sr. CPL is owned by Calamos Family Partners, Inc. (“CFP”), John P. Calamos, Sr. and John S. Koudounis. CFP is owned by members of the Calamos family, including John P.
Calamos, Sr.

Investment Management Agreement

Subject to the overall supervision and review of the Board of Trustees, Calamos provides the Fund with investment research, advice and supervision and furnishes continuously an investment program for the
Fund, consistent with the investment objective and policies of the Fund. In addition, Calamos furnishes for use of the Fund such office space and facilities as the Fund may require for its reasonable needs, supervises the Fund’s business and
affairs and provides the following other services on behalf of the Fund (not provided by persons not a party to the investment management agreement): (a) preparing or assisting in the preparation of reports to and meeting materials for the
Trustees; (b) supervising, negotiating contractual arrangements with, to the extent appropriate, and monitoring the performance of, accounting agents, custodians, depositories, transfer agents and pricing agents, accountants, attorneys,
printers, underwriters, brokers and dealers, insurers and other persons in any capacity deemed to be necessary or desirable to Fund operations; (c) assisting in the preparation and making of filings with the Commission and other regulatory and
self-regulatory organizations, including, but not limited to, preliminary and definitive proxy materials, registration statements on Form N-2 and amendments thereto, and reports on Form N-CEN and
Form N-CSR; (d) overseeing the tabulation of proxies by the Fund’s transfer agent; (e) assisting in the preparation and filing of the Fund’s federal, state and local tax returns; (f) assisting in the preparation
and filing of the Fund’s federal excise tax returns pursuant to Section 4982 of the Code; (g) providing assistance with investor and public relations matters; (h) monitoring the valuation of portfolio securities and the
calculation of net asset value; (i) monitoring the registration of shares of beneficial interest of the Fund under applicable federal and state securities laws; (j) maintaining or causing to be maintained for the Fund all books, records
and reports and any other information required under the 1940 Act, to the extent that such books, records and reports and other information are not maintained by the Fund’s custodian or other agents of the Fund; (k) assisting in
establishing the accounting policies of the Fund; (l) assisting in the resolution of accounting issues that may arise with respect to the Fund’s operations and consulting with the Fund’s independent accountants, legal counsel and the
Fund’s other agents as necessary in connection therewith; (m) reviewing the Fund’s bills; (n) assisting the Fund in determining the amount of dividends and distributions available to be paid by the Fund to its shareholders,
preparing and arranging for the printing of dividend notices to shareholders, and providing the transfer and dividend paying agent, the custodian, and the accounting agent with such information as is required for such parties to effect the payment
of dividends and distributions; and (o) otherwise assisting the Fund as it may reasonably request in the conduct of the Fund’s business, subject to the direction and control of the Trustees.

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Under the investment management agreement, the Fund pays to Calamos a fee based on the
average weekly managed assets that is computed weekly and payable monthly in arrears. The fee paid by the Fund is set at the annual rate of 0.80% of the Fund’s average weekly managed assets. Because the fees paid to Calamos are determined on
the basis of the Fund’s managed assets, the amount of management fees paid to Calamos when the Fund uses leverage will be higher than if the Fund did not use leverage. Therefore, Calamos has a financial incentive to use leverage, which creates
a conflict of interest between Calamos and the Fund’s common shareholders. A discussion regarding the basis of the approval of the Investment Management Agreement is available in the Fund’s annual report for the year ended October 31,
2019.

Under the terms of its investment management agreement, except for the services and facilities provided by Calamos as
set forth therein, the Fund shall assume and pay all expenses for all other Fund operations and activities and shall reimburse Calamos for any such expenses incurred by Calamos. The expenses borne by the Fund shall include, without limitation:
(a) organizational expenses of the Fund (including out-of-pocket expenses, but not including Calamos’ overhead or employee costs); (b) fees payable to Calamos; (c) legal expenses; (d) auditing and accounting
expenses; (e) maintenance of books and records that are required to be maintained by the Fund’s custodian or other agents of the Fund; (f) telephone, telex, facsimile, postage and other communications expenses; (g) taxes and
governmental fees; (h) fees, dues and expenses incurred by the Fund in connection with membership in investment company trade organizations and the expense of attendance at professional meetings of such organizations; (i) fees and expenses
of accounting agents, custodians, subcustodians, transfer agents, dividend disbursing agents and registrars; (j) payment for portfolio pricing or valuation services to pricing agents, accountants, bankers and other specialists, if any;
(k) expenses of preparing share certificates; (l) expenses in connection with the issuance, offering, distribution, sale, redemption or repurchase of securities issued by the Fund; (m) expenses relating to investor and public
relations provided by parties other than Calamos; (n) expenses and fees of registering or qualifying shares of beneficial interest of the Fund for sale; (o) interest charges, bond premiums and other insurance expenses; (p) freight,
insurance and other charges in connection with the shipment of the Fund’s portfolio securities; (q) the compensation and all expenses (specifically including travel expenses relating to Fund business) of Trustees, officers and employees of
the Fund who are not affiliated persons of Calamos; (r) brokerage commissions or other costs of acquiring or disposing of any portfolio securities of the Fund; (s) expenses of printing and distributing reports, notices and dividends to
shareholders; (t) expenses of preparing and setting in type, printing and mailing prospectuses and statements of additional information of the Fund and supplements thereto; (u) costs of stationery; (v) any litigation expenses;
(w) indemnification of Trustees and officers of the Fund; (x) costs of shareholders’ and other meetings; (y) interest on borrowed money, if any; and (z) the fees and other expenses of listing the Fund’s shares on Nasdaq
or any other national stock exchange.

Portfolio Managers

John P. Calamos, Sr. John P. Calamos, Sr. has been President, Trustee and Co-Portfolio Manager of the Fund since inception and for
Calamos: Founder, Chairman and Global Chief Investment Officer (“CIO”) since August 2019-2020; Chairman and Global CIO from April to August 2019-2020; Chairman, Chief Executive Officer and Global Co-CIO between April 2013 and April 2019-2020; Chief
Executive Officer and Global Co-CIO between August 2012 and April 2013; and Chief Executive Officer and Co-CIO prior thereto.

Dennis Cogan. Dennis Cogan joined Calamos in March 2005 and since March 2013 is a Co-Portfolio Manager. Between March 2005 and March 2013 he was a senior strategy analyst.

R. Matthew Freund. R. Matthew Freund joined Calamos in November 2019-2020 as a Co-CIO, Head of Fixed Income Strategies, as well as a
Senior Co-Portfolio Manager. Previously, he was SVP of Investment Portfolio Management and Chief Investment Officer at USAA Investments since 2010.

John Hillenbrand. John Hillenbrand joined Calamos in 2002 and since September 2015 is a Co-CIO, Head of Multi-Asset Strategies and Co-Head of Convertible Strategies, as well as a Senior
Co-Portfolio Manager. From March 2013 to September 2015 he was a Co-Portfolio Manager. Between August 2002 and March 2013 he was a senior strategy analyst.

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Nick Niziolek. Nick Niziolek joined Calamos in March 2005 and has been a Co-CIO,
Head of Global Strategies, as well as a Senior Co-Portfolio Manager, since September 2015. Between August 2013 and September 2015, he was a Co-Portfolio Manager, Co-Head of Research. Between March 2013 and August 2013 he was a Co-Portfolio Manager.
Between March 2005 and March 2013 he was a senior strategy analyst.

Eli Pars. Eli Pars joined Calamos in May 2013
and has been a Co-CIO, Head of Alternative Strategies and Co-Head of Convertible Strategies, as well as Senior Co-Portfolio Manager, since September 2015. Between May 2013 and September 2015, he was a Co-Portfolio Manager. Previously, he was a
Portfolio Manager at Chicago Fundamental Investment Partners from February 2009 until November 2012.

Jon Vacko. Jon
Vacko joined Calamos in June 2000 and has been a Senior Co-Portfolio Manager since September 2015. Previously, he was a Co-Portfolio Manager from August 2013 to September 2015; prior thereto he was a Co-Head of Research and Investments from July
2010 to August 2013.

Joe Wysocki. Joe Wysocki joined Calamos in October 2003 and since March 2015 has been a
Co-Portfolio Manager. Previously, Mr. Wysocki was a sector head from March 2014 to March 2015. Prior thereto, he was a Co-Portfolio Manager from March 2013 to March 2014. Between February 2007 and March 2013 he was a senior strategy analyst.

Calamos employs a “team of teams” approach to portfolio management, led by the Global CIO and our CIO team
consisting of 5 Co-CIOs with specialized areas of investment expertise. The Global CIO and Co-CIO team are responsible for oversight of investment team resources, investment processes, performance and risk. As heads of investment verticals, Co-CIOs
manage investment team members and, along with Co-Portfolio Managers, have day-to-day portfolio oversight and construction responsibilities of their respective investment strategies. While investment research professionals within each Co-CIO’s
team are assigned specific strategy responsibilities, they also provide support to other investment team verticals, creating deeper insights across a wider range of investment strategies. The combination of specialized investment teams with cross
team collaboration results in what we call our team of teams approach.

This team of teams approach is further reflected in
the composition of Calamos’ Investment Committee, made up of the Global CIO, the Co-CIO team, the Head of Global Trading, and the Chief of IT and Operations. Other members of the investment team participate in Investment Committee meetings in
connection with specific investment related issues or topics as deemed appropriate.

The structure and composition of the
Investment Committee results in a number of benefits, as it:

Leads to broader perspective on investment decisions: multiple viewpoints and areas of expertise feed into consensus;

Promotes collaboration between teams; and

Functions as a think tank with the goal of identifying ways to outperform the market on a risk-adjusted basis.

The objectives of the Investment Committee are to:

Form the firm’s top-down macro view, market direction, asset allocation, and sector/country positioning.

Establish firm-wide secular and cyclical themes for review.

Review firm-wide and portfolio risk metrics, recommending changes where appropriate.

Review firm-wide, portfolio and individual security liquidity constraints.

Evaluate firm-wide and portfolio investment performance.

Evaluate firm-wide and portfolio hedging policies and execution.

Evaluate enhancements to the overall investment process.

John P. Calamos, Sr., Founder, Chairman and Global CIO, is responsible for the day-to-day management of the team, bottom-up research efforts and strategy implementation. R. Matthew Freund, John
Hillenbrand, Nick

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Niziolek, Eli Pars, and Jon Vacko are each Sr. Co-Portfolio Managers, and Dennis Cogan and Joe Wysocki are each Co-Portfolio Managers.

For over 20 years, the Calamos portfolio management team has managed money for their clients in convertible, high yield and global
strategies. Furthermore, Calamos has extensive experience investing in foreign markets through its convertible securities and high yield securities strategies. Such experience has included investments in established as well as emerging foreign
markets. The Fund’s statement of additional information provides additional information about the Co-Portfolio Managers, including other accounts they manage, their ownership in the Calamos Family of Funds and their compensation.

Fund Administration and Accounting

Under the arrangements with State Street to provide fund accounting services, State Street provides certain administrative and accounting services to the Fund and such other funds advised by Calamos that
may be part of those arrangements (the Fund and such other funds are collectively referred to as the “Calamos Funds”) as described more fully in the statement of additional information. For the services rendered to the Calamos Funds, State
Street receives a fee based on the combined managed assets of the closed-end Calamos Funds and the combined total average daily net assets of the open-end Calamos Funds (“Combined Assets”). State Street receives a fee at the annual rate of
0.005% for the first $20.0 billion of Combined Assets, 0.004% for the next $10.0 billion of Combined Assets and 0.003% for the Combined Assets in excess of $30.0 billion. Each fund of the Calamos Funds pays its pro-rata share of the
fees payable to State Street based on relative Combined Assets of each fund. Because the fees payable to State Street are based on the relative Combined Assets of the Calamos Funds, the fees increase as the Calamos Funds increase their leverage.

CLOSED-END FUND STRUCTURE

The Fund is a diversified, closed-end management investment company (commonly referred to as a closed-end fund) which
commenced investment operations in June 2002. Closed-end funds differ from open-end management investment companies (which are generally referred to as mutual funds) in that closed-end funds generally list their shares for trading on a stock
exchange and do not redeem their shares at the request of the shareholder. This means that if you wish to sell your shares of a closed-end fund you must trade them on the market like any other stock at the prevailing market price at that time. In a
mutual fund, if the shareholder wishes to sell shares of the fund, the mutual fund will redeem or buy back the shares at “net asset value.” Also, mutual funds generally offer new shares on a continuous basis to new investors, and
closed-end funds generally do not. From time to time, the Fund may engage in a continuous at the market offering of its common shares as described in the applicable prospectus supplement. The continuous inflows and outflows of assets in a mutual
fund can make it difficult to manage the fund’s investments. By comparison, closed-end funds are generally able to stay more fully invested in securities that are consistent with their investment objectives and also have greater flexibility to
make certain types of investments and to use certain investment strategies, such as financial leverage and investments in illiquid securities.

Shares of closed-end funds frequently trade at a discount to their net asset value. To the extent the Fund’s common shares trade at a discount, the Fund’s Board of Trustees may from time to time
engage in open-market repurchases or tender offers for shares after balancing the benefit to shareholders of the increase in the net asset value per share resulting from such purchases against the decrease in the assets of the Fund and potential
increase in the expense ratio of expenses to assets of the Fund. The Board of Trustees believes that in addition to the beneficial effects described above, any such purchases or tender offers may result in the temporary narrowing of any discount but
may not have any long-term effect on the level of any discount. We cannot guarantee or assure, however, that the Fund’s Board of Trustees will decide to engage in any of these actions. Nor is there any guarantee or assurance that such actions,
if undertaken, would result in the shares trading at a price equal or close to net asset value per share. The Board of Trustees might also consider converting the Fund to an open-end mutual fund, which would also require a vote of the shareholders
of the Fund. Conversion of the Fund to an open-end mutual fund would require an amendment to the Fund’s Agreement and Declaration of Trust. Such an

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amendment would require the favorable vote of the holders of at least 75% of the Fund’s outstanding shares (including any preferred shares) entitled to be voted on the matter, voting as a
single class (or a majority of such shares if the amendment were previously approved, adopted or authorized by 75% of the total number of Trustees fixed in accordance with the By-Laws), and, assuming preferred shares are issued, the affirmative vote
of a majority of outstanding preferred shares, voting as a separate class.

CERTAIN FEDERAL
INCOME TAX MATTERS

The following is a summary discussion of certain U.S. federal income tax consequences affecting the
Fund and its shareholders and noteholders (as the case may be). The discussion reflects applicable tax laws of the United States as of the date of this prospectus, which tax laws may be changed or subject to new interpretations by the courts or the
IRS retroactively or prospectively. No assurance can be given that the IRS would not assert, or that a court would not sustain, a position different from any of the tax aspects set forth below. The specific terms of preferred shares and debt
securities may result in different tax consequences to holders than those described herein. Tax matters are very complicated, and the tax consequences of an investment in and holding of our securities will depend on the particular facts of each
investor’s situation. No attempt is made to present a detailed explanation of all U.S. federal, state, local and foreign tax concerns affecting the Fund and its shareholders and noteholders (including shareholders and noteholders subject to
special tax rules and shareholders owning large positions in the Fund), and the discussion set forth herein does not constitute tax advice. Investors are advised to consult their own tax advisers with respect to the application to their own
circumstances of the general federal income taxation rules described below and with respect to other federal, state, local or foreign tax consequences applicable to them before making an investment in our securities. Unless otherwise noted, this
discussion assumes that investors are U.S. persons and hold our securities as capital assets. More detailed information regarding the U.S. federal income tax consequences of investing in our securities is in the statement of additional information.

Federal Income Taxation of the Fund

The Fund has elected to be treated, and intends to qualify and to be eligible to be treated each year, as a “regulated investment company” under Subchapter M of the Code, so that it will not pay
U.S. federal income tax on income and capital gains timely distributed to shareholders. In order to qualify and be eligible for treatment as a regulated investment company, the Fund must, among other things, satisfy diversification, 90% gross income
and distribution requirements. The Fund’s failure to qualify and be eligible for treatment as a regulated investment company would result in corporate level taxation, and consequently, a reduction in income available for distribution to
shareholders.

If the Fund qualifies as a regulated investment company and distributes to its shareholders at least 90% of
the sum of (i) its “investment company taxable income” as that term is defined in the Code (which includes, among other things, dividends, taxable interest, the excess of any net short-term capital gains over net long-term capital
losses, taking into account any capital loss carryforwards and certain net foreign currency exchange gains, less certain deductible expenses) without regard to the deduction for dividends paid, and (ii) the excess of its gross tax-exempt
interest, if any, over certain disallowed deductions, the Fund will be relieved of U.S. federal income tax on any income of the Fund, including long-term capital gains, distributed to shareholders. However, if the Fund retains any investment company
taxable income or net capital gain (i.e., the excess of net long-term capital gain over net short-term capital loss, taking into account any capital loss carryforwards), it will be subject to U.S. federal income tax at regular corporate federal
income tax rates on the amount retained. The Fund intends to distribute at least annually all or substantially all of its investment company taxable income, net tax-exempt interest, and net capital gain. Under the Code, the Fund will generally be
subject to a nondeductible 4% federal excise tax on its undistributed ordinary income and capital gains if it fails to meet certain distribution requirements with respect to each calendar year. The Fund intends to make distributions in a timely
manner in amounts necessary to avoid the excise tax and accordingly does not expect to be subject to this tax.

If, for any
taxable year, the Fund were not to qualify as a regulated investment company for U.S. federal income tax purposes, it would be treated in the same manner as a regular corporation subject to U.S. federal

58

income tax and distributions to its shareholders would not be deducted by the Fund in computing its taxable income. In such event, the Fund’s distributions, to the extent derived from the
Fund’s current and accumulated earnings and profits, would generally constitute ordinary dividends, which would generally be eligible for the dividends received deduction available to corporate shareholders, and noncorporate shareholders would
generally be able to treat such distributions as “qualified dividend income” eligible for reduced rates of U.S. federal income taxation.

The Fund could be required to recognize unrealized gains, pay substantial taxes and interest and make substantial distributions before requalifying as a regulated investment company that is accorded
special tax treatment.

From time to time, a substantial portion of the Fund’s investments in loans and other debt
obligations could be treated as having market discount and/or “original issue discount” (“OID”) for U.S. federal income tax purposes, which, in some cases, could be significant and could cause the Fund to recognize income in
respect of these investments before or without receiving cash representing such income. If so, the Fund could be required to pay out as an income distribution each year an amount which is greater than the total amount of cash interest the Fund
actually received. As a result, the Fund could be required at times to liquidate investments (including at potentially disadvantageous times or prices) in order to satisfy its distribution requirements or to avoid incurring Fund-level U.S. federal
income or excise taxes. If the Fund liquidates portfolio securities to raise cash, the Fund may realize gain or loss on such liquidations; in the event the Fund realizes net long-term or short-term capital gains from such liquidation transactions,
its shareholders may receive larger capital gain or ordinary dividends, respectively, than they would in the absence of such transactions.

Investments in debt obligations that are at risk of or in default present special tax issues for the Fund. Tax rules are not entirely clear about issues such as whether or to what extent the Fund should
recognize market discount on a debt obligation; when the Fund may cease to accrue interest, OID or market discount; when and to what extent the Fund may take deductions for bad debts or worthless securities; and how the Fund should allocate payments
received on obligations in default between principal and income. These and other related issues will be addressed by the Fund when, as, and if it invests in such securities in order to seek to ensure that it distributes sufficient income to preserve
its status as a regulated investment company and avoid becoming subject to U.S. federal income or excise tax.

The Fund is
permitted to carry forward net capital losses to one or more subsequent taxable years without expiration. Any such carryforward losses will retain their character as short-term or long-term. Capital loss carryforwards are reduced to the extent they
offset current-year net realized capital gains, whether the Fund retains or distributes such gains.

Certain of the
Fund’s investment practices may be subject to special and complex federal income tax provisions that may, among other things, (i) disallow, suspend or otherwise limit the allowance of certain losses or deductions, (ii) convert
tax-advantaged, long-term capital gains and qualified dividend income into higher taxed short-term capital gain or ordinary income, (iii) increase ordinary income distributions, (iv) convert an ordinary loss or a deduction into a capital
loss (the deductibility of which is more limited), (v) cause the Fund to recognize income or gain without a corresponding receipt of cash, (vi) adversely affect the timing as to when a purchase or sale of stock or securities is deemed to
occur, and (vii) adversely alter the characterization of certain complex financial transactions. The Fund will monitor its transactions and may make certain tax elections where applicable in order to mitigate the effect of these provisions, if
possible.

Because the tax treatment and the tax rules applicable to these types of transactions are in some cases
uncertain under current law, an adverse determination or future guidance by the IRS with respect to these rules or treatment (which determination or guidance could be retroactive) may affect whether the Fund has made sufficient distributions, and
otherwise satisfied the relevant requirements, to maintain its qualification as a regulated investment company and avoid a Fund-level tax.

It is possible that the Fund’s use of derivatives and foreign currency-denominated instruments, and any of the Fund’s transactions in foreign currencies and hedging activities, could produce a
difference between its book

59

income and the sum of its taxable income (including realized capital gains) and net tax-exempt income (if any). If such a difference arises, and the Fund’s book income is less than the sum
of its taxable income (including realized capital gains) and net tax-exempt income (if any), the Fund could be required to make distributions exceeding book income to qualify for treatment as a regulated investment company and to eliminate
Fund-level tax. In the alternative, if the Fund’s book income exceeds the sum of its taxable income (including realized capital gains) and its net tax-exempt income (if any), the distribution (if any) of such excess generally will be treated as
(i) a dividend to the extent of the Fund’s remaining current and accumulated earnings and profits (including earnings and profits arising from tax-exempt income), if any, (ii) thereafter, as a return of capital to the extent of the
recipient’s adjusted tax basis in its shares, and (iii) thereafter, as gain from the sale or exchange of a capital asset.

Dividends, interest, proceeds and gains received by the Fund on foreign securities may be subject to foreign withholding or other taxes, which would reduce the yield on or return from those investments.
If more than 50% of the value of the Fund’s assets at the close of the taxable year consists of stock or securities of foreign corporations, the Fund may make an election under the Code to pass through such taxes to shareholders of the Fund. If
the Fund is eligible to and makes such an election, shareholders will generally be able (subject to applicable limitations under the Code) to claim a credit or deduction (but not both) on their federal income tax return for, and will be required to
treat as part of the amounts distributed to them, their pro rata portion of the income taxes paid by the Fund to foreign countries. If the Fund makes such an election, it will provide relevant information to its shareholders. If such election is not
made, shareholders will not be required to include such taxes in their gross incomes and will not be entitled to a tax deduction or credit for such taxes on their own federal income tax returns.

Each prospective investor is urged to consult its tax adviser regarding taxation of foreign securities in the Fund’s portfolio and
any available foreign tax credits with respect to the prospective investor’s own situation.

Federal Income Taxation of Common and
Preferred Shareholders

Federal Income Tax Treatment of Common Share
Distributions.    Unless a shareholder is ineligible to participate or elects otherwise, all distributions will be automatically reinvested in additional shares of common stock of the Fund pursuant to the Fund’s
Automatic Dividend Reinvestment Plan (the “Plan”). For taxpayers subject to U.S. federal income tax, all dividends will generally be taxable regardless of whether a shareholder takes them in cash or they are reinvested pursuant to the Plan
in additional shares of the Fund. Distributions of the Fund’s investment company taxable income (determined without regard to the deduction for dividends paid) will generally be taxable at ordinary federal income tax rates to the extent of the
Fund’s current and accumulated earnings and profits. However, a portion of such distributions derived from certain corporate dividends, if any, may qualify for either the dividends received deduction available to corporate shareholders
under Section 243 of the Code or the reduced rates of U.S. federal income taxation for “qualified dividend income” currently available to noncorporate shareholders under Section 1(h)(11) of the Code, provided certain holding
period and other requirements are met at both the Fund and shareholder levels. Distributions of net capital gains (as defined above), if any, that are properly reported as capital gain dividends are generally taxable as long-term capital gains for
U.S. federal income tax purposes without regard to the length of time a shareholder has held shares of the Fund. A distribution of an amount in excess of the Fund’s current and accumulated earnings and profits, if any, will be treated by a
shareholder as a tax-free return of capital, which is applied against and reduces the shareholder’s basis in their shares. Such distributions represent a return of the investor’s capital to the extent of his or her basis in the shares, and
thus, could potentially subject the shareholder to capital gains taxation in connection with a later sale of Fund shares, even if those shares are sold at a price that is lower than the shareholder’s original investment price. To the extent
that the amount of any such distribution exceeds the shareholder’s basis in their shares, the excess will be treated by the shareholder as gain from the sale or exchange of shares. The U.S. federal income tax status of all dividends and
distributions will be reported by the Fund to the shareholders annually.

If the Fund retains any net capital gain, the
Fund may report the retained amount as undistributed capital gains to shareholders who, if subject to U.S. federal income tax on long-term capital gains, (i) will be required to

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include in income as long-term capital gain their proportionate share of such undistributed amount, and (ii) will be entitled to credit their proportionate share of the federal income tax
paid by the Fund on the undistributed amount against their U.S. federal income tax liabilities, if any, and to claim refunds to the extent the credit exceeds such liabilities. If the Fund makes this designation, the tax basis of shares owned by a
shareholder of the Fund will, for U.S. federal income tax purposes, generally be increased by the difference between the amount of undistributed net capital gain included in the shareholder’s gross income and the federal income tax deemed paid
by the shareholder.

If a shareholder’s distributions are automatically reinvested pursuant to the Plan and the Plan
Agent invests the distribution in shares acquired on behalf of the shareholder in open-market purchases, for U.S. federal income tax purposes, the shareholder will be treated as having received a taxable distribution in the amount of the cash
dividend that the shareholder would have received if the shareholder had elected to receive cash. If a shareholder’s distributions are automatically reinvested pursuant to the Plan and the Plan Agent invests the distribution in newly issued
shares of the Fund, the shareholder will generally be treated as receiving a taxable distribution equal to the fair market value of the stock the shareholder receives.

At the time of an investor’s purchase of the Fund’s shares, a portion of the purchase price may be attributable to realized or unrealized appreciation in the Fund’s portfolio or
undistributed taxable income of the Fund. Consequently, subsequent distributions by the Fund with respect to these shares from such appreciation or income may be taxable to such investor even if the net asset value of the investor’s shares is,
as a result of the distributions, reduced below the investor’s cost for such shares and the distributions economically represent a return of a portion of the investment.

Dividends declared by the Fund in October, November or December with a record date in such month that are paid during the following January will be treated for U.S. federal income tax purposes as paid by
the Fund and received by the shareholders on December 31 of the calendar year in which they were declared.

Federal
Income Tax Treatment of Preferred Share Distributions.    Under present law, the Fund intends to treat its preferred shares as equity, and, in such case, distributions with respect to preferred shares (other than
distributions in redemption of preferred shares subject to Section 302(b) of the Code) will generally constitute dividends to the extent of the Fund’s current and accumulated earnings and profits, as calculated for federal income tax
purposes. Except in the case of distributions of net capital gain, such dividends generally will be taxable to holders at ordinary federal income tax rates but may qualify for the dividends received deduction available to corporate shareholders
under Section 243 of the Code or the reduced rates of U.S. federal income taxation under Section 1(h)(11) of the Code that apply to qualified dividend income received by noncorporate shareholders. Distributions reported by the Fund as net
capital gain distributions will be taxable as long-term capital gain regardless of the length of time a shareholder has held shares of the Fund. Please see the discussion above on qualified dividend income, dividends received deductions and net
capital gain.

The IRS currently requires that a regulated investment company that has two or more classes of stock
allocate to each such class proportionate amounts of each type of its income (such as ordinary income and capital gains). Accordingly, the Fund intends to report distributions made with respect to preferred shares as ordinary income, capital gain
distributions, dividends qualifying for the dividends received deduction, if any, and qualified dividend income, if any, in proportion to the preferred shares’ share of total dividends paid during the year. See “Certain Federal Income Tax
Matters” in the statement of additional information.

Earnings and profits are generally treated, for U.S. federal income
tax purposes, as first being used to pay distributions on the preferred shares, and then to the extent remaining, if any, to pay distributions on the common shares. Distributions in excess of the Fund’s earnings and profits, if any, will first
reduce a shareholder’s adjusted tax basis in his or her preferred shares and, after the adjusted tax basis is reduced to zero, will constitute capital gains to a shareholder who holds such shares as a capital asset.

Dividends declared by the Fund in October, November or December with a record date in such month that are paid during the following
January will be treated for federal income tax purposes as paid by the Fund and received by the shareholders on December 31 of the calendar year in which they were declared.

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Sale of Shares.    Sales and other dispositions of the
Fund’s shares, including a repurchase by the Fund of its shares, generally are taxable events for shareholders that are subject to U.S. federal income tax. Shareholders should consult their own tax advisers with reference to their individual
circumstances to determine whether any particular transaction in the Fund’s shares is properly treated as a sale or exchange for federal income tax purposes, as the following discussion assumes, and the tax treatment of any gains or losses
recognized in such transactions. In particular, a repurchase by the Fund of its shares may be subject to different rules, as discussed in more detail in the statement of additional information. Gain or loss will generally be equal to the difference
between the amount of cash and the fair market value of other property received and the shareholder’s adjusted tax basis in the shares sold or exchanged. Such gain or loss will generally be characterized as capital gain or loss and will be
long-term or short-term depending on the shareholder’s holding period in the shares disposed. However, any loss realized by a shareholder upon the sale or other disposition of shares with a federal income tax holding period of six months or
less will be treated as a long-term capital loss to the extent of any amounts treated as distributions of long-term capital gain with respect to such shares. The ability to deduct capital losses may be limited.

Gain or loss will generally be long-term capital gain or loss if the shares disposed of were held for more than one year and will be
short-term capital gain or loss if the shares disposed of were held for one year or less. Net long-term capital gain recognized by a noncorporate U.S. shareholder generally will be subject to federal income tax at a lower rate than net short-term
capital gain or ordinary income. For corporate shareholders, capital gain is generally taxed for federal income tax purposes at the same rate as ordinary income. In addition, losses on sales or other dispositions of shares may be disallowed under
the “wash sale” rules in the event that substantially identical stock or securities are treated as acquired by a shareholder (including those made pursuant to reinvestment of dividends) within a period of 61 days beginning 30 days before
and ending 30 days after a sale or other disposition of shares by such shareholder. In such a case, the disallowed portion of any loss generally would be included in the U.S. federal tax basis of the shares acquired.

Backup Withholding.    The Fund is required in certain circumstances to withhold federal income tax
(“backup withholding”) from reportable payments including dividends, capital gain distributions, and proceeds of sales or other dispositions of the Fund’s shares paid to certain holders of the Fund’s shares who do not furnish the
Fund with their correct social security number or other taxpayer identification number and certain other certifications, or who are otherwise subject to backup withholding. Backup withholding is not an additional tax. Any amounts withheld from
payments made to a shareholder may be refunded or credited against such shareholder’s U.S. federal income tax liability, if any, provided that the required information is furnished to the IRS.

Shares Purchased Through Tax-Qualified Plans.    Special tax rules apply to investments through defined
contribution plans and other tax-qualified plans. Shareholders should consult their tax advisers to determine the suitability of shares of the Fund as an investment through such plans and the precise effect of an investment on their particular tax
situation.

Taxation of Non-U.S. Shareholders.    The description of certain federal income tax
provisions above relates only to U.S. federal income tax consequences for shareholders who are U.S. persons (i.e., U.S. citizens or resident aliens or U.S. corporations, partnerships, trusts or estates who are subject to U.S. federal income tax on a
net income basis). Investors other than U.S. persons, including non-resident alien individuals, may be subject to different U.S. federal income tax treatment. With respect to such persons, the Fund must generally withhold U.S. federal withholding
tax at the rate of 30% (or, if the Fund receives certain certifications from such non-U.S. shareholder, such lower rate as prescribed by an applicable tax treaty) on amounts treated as ordinary dividends from the Fund. However, the Fund is not
required to withhold tax on any amounts paid to a non-U.S. person with respect to capital gain distributions (i.e., distributions of net capital gain that are properly reported by the Fund as capital gain dividends), dividends attributable to
“qualified short-term gain” (i.e., the excess of net short-term capital gain over net long-term capital loss) reported as such by the Fund and dividends attributable to certain U.S. source interest income of types similar to those not
subject to federal withholding tax if earned directly by a non-U.S. person, provided such amounts are properly reported by the Fund. Shareholders should consult their

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own tax advisers on these matters and on any specific question of U.S. federal, state, local, foreign and other applicable tax laws before making an investment in the Fund.

Federal Income Taxation of Holders of Debt Securities

Federal Income Tax Treatment of Holders of Debt Securities.    Under present law, the Fund intends to treat its debt securities as indebtedness of the Fund for federal income
tax purposes, which treatment the discussion below assumes. The Fund intends to treat all payments made with respect to the debt securities consistent with this characterization. The following discussion assumes that all interest on the debt
securities will be qualified stated interest (which is generally interest that is unconditionally payable at least annually at a fixed or qualified floating rate), and that the debt securities will have a fixed maturity date of more than one year
from the date of issuance.

Taxation of Interest.    Payments or accruals of interest on debt
securities generally will be taxable to holders as ordinary interest income at the time such interest is received (actually or constructively) or accrued, in accordance with their regular method of accounting for federal income tax purposes.

Purchase, Sale and Redemption of Debt Securities.    Initially, the tax basis in debt
securities acquired generally will be equal to the cost to acquire such debt securities. This basis will be increased by the amounts, if any, that a holder includes in income under the rules governing OID (taking into account any acquisition premium
that offsets such OID) and market discount, and will be decreased by the amount of any amortized premium on such debt securities, as discussed below, and any payments on such debt securities other than stated interest. When a holder sells, exchanges
or redeems any of their debt securities, or otherwise disposes of their debt securities in a taxable transaction, the holder of the debt securities generally will recognize gain or loss equal to the difference between the amount realized on the
transaction (less any accrued and unpaid interest (including OID), which will be subject to federal income tax as interest in the manner described above) and the tax basis in the debt securities relinquished.

Except as discussed below with respect to market discount, the gain or loss recognized on the sale, exchange, redemption or other taxable
disposition of any debt securities generally will be capital gain or loss. Such gain or loss will generally be long-term capital gain or loss if the disposed debt securities were held for more than one year and will be short-term capital gain or
loss if the disposed debt securities were held for one year or less. A holder’s ability to deduct capital losses may be limited.

Amortizable Premium.    If a holder purchases debt securities at a cost greater than their stated redemption price at maturity, plus accrued interest, the holder will be
considered to have purchased the debt securities at a premium, and generally may elect to amortize this premium as an offset to interest income, using a constant yield method, over the remaining term of the debt securities. If the holder makes the
election to amortize the premium, it generally will apply to all debt instruments held at the beginning of the first taxable year to which the election applies, as well as any debt instruments subsequently acquired. In addition, the holder may not
revoke the election without the consent of the IRS. If the holder elects to amortize the premium, the holder will be required to reduce its tax basis in the debt securities by the amount of the premium amortized during its holding period. If the
holder does not elect to amortize premium, the amount of premium will be included in its tax basis in the debt securities. Therefore, if the holder does not elect to amortize the premium and holds the debt securities to maturity, the holder
generally will be required to treat the premium as a capital loss when the debt securities are redeemed.

Original Issue
Discount.    If the stated redemption price at maturity of the debt securities exceeds their issue price by at least the statutory de minimis amount, the debt securities will be treated as being issued with OID for
U.S. federal income tax purposes. In that case, the holder will be required to include such OID in gross income (as ordinary income) as it accrues over the term of the debt securities on a constant-yield basis, in advance of the receipt of cash
attributable to that income and regardless of its regular method of accounting for U.S. federal income tax purposes.

Acquisition Premium.    If a holder purchases debt securities that were issued with OID at a cost greater than
their issue price and less than or equal to their stated redemption price at maturity, the holder will be considered

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to have purchased the debt securities with acquisition premium. Such holder will generally be permitted to reduce the daily portions of OID required to be included in income by a fraction, the
numerator of which is the excess of the holder’s initial basis in the debt securities over the debt securities’ issue price, and the denominator of which is the excess of the redemption price at maturity of the debt securities over their
issue price.

Market Discount.    If the holder purchases debt securities in the secondary
market at a price that reflects a “market discount,” any principal payments on, or any gain realized on the disposition of the debt securities generally will be treated as ordinary interest income to the extent of the market discount that
accrued on the debt securities during the time the holder held such debt securities. “Market discount” is defined under the Code as, in general, the excess (subject to a statutory de minimis amount) of the stated redemption price at
maturity (or in the case of an obligation issued with OID, its “revised issue price”) over the purchase price of the debt security. In addition, the holder may be required to defer the deduction of all or a portion of any interest paid on
any indebtedness incurred or continued to purchase or carry the debt securities that were acquired at a market discount.

The
holder may elect to include market discount in gross income currently as it accrues (on either a ratable or constant yield basis), in lieu of treating a portion of any gain realized on a sale of, the debt securities as ordinary income. If the holder
elects to include market discount on a current basis, the interest deduction deferral rule described above will not apply and the holder will increase its basis in the debt security by the amount of market discount it includes in gross income. If
the holder does make such an election, it will apply to all market discount debt instruments that the holder acquires on or after the first day of the first taxable year to which the election applies. This election may not be revoked without the
consent of the IRS.

Information Reporting and Backup Withholding.    In general, information
reporting requirements will apply to payments of principal, interest, and premium, if any, paid on debt securities and to the proceeds of the sale of debt securities paid to U.S. holders other than certain exempt recipients (such as certain
corporations) provided they establish such exemption. Information reporting generally will apply to payments of interest on the debt securities to non-U.S. Holders (as defined below) and the amount of tax, if any, withheld with respect to such
payments. Copies of the information returns reporting such interest payments and any withholding may also be made available to the tax authorities in the country in which the non-U.S. Holder resides under the provisions of an applicable income tax
treaty. In addition, for non-U.S. Holders, information reporting will apply to the proceeds of the sale of debt securities within the United States or conducted through United States-related financial intermediaries unless the certification
requirements described below have been complied with and the statement described below in “Taxation of Non-U.S. Holders” has been received (and the payor does not have actual knowledge or reason to know that the holder is a United States
person) or the holder otherwise establishes an exemption.

We may be required to withhold, for U.S. federal income tax
purposes, a portion of all payments (including redemption proceeds) payable to holders of debt securities who fail to provide us with their correct taxpayer identification number, who fail to make required certifications or who have been notified by
the IRS that they are subject to backup withholding (or if we have been so notified). Certain corporate and other shareholders specified in the Code and the regulations thereunder are exempt from backup withholding. Backup withholding is not an
additional tax. Any amounts withheld may be credited against the holder’s U.S. federal income tax liability provided the appropriate information is furnished to the IRS.

A holder who is a non-U.S. Holder may have to comply with certification procedures to establish its non-U.S. status in order to avoid
backup withholding tax requirements. The certification procedures required to claim the exemption from withholding tax on interest income described below with respect to non-U.S. Holders will satisfy these requirements.

Taxation of Non-U.S. Holders.    If a holder is a non-resident alien individual or a foreign corporation (a
“non-U.S. Holder”), the payment of interest on the debt securities generally will be considered “portfolio interest” and thus generally will be exempt from U.S. federal withholding tax. This exemption will apply provided that
(1) interest paid on the debt securities is not effectively connected with the holder’s conduct of a trade or business in the United States, (2) the holder is not a bank whose receipt of interest on the debt securities

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is described in Section 881(c)(3)(A) of the Code, (3) the holder does not actually or constructively own 10 percent or more of the combined voting power of all classes of the
Fund’s stock entitled to vote, (4) the holder is not a controlled foreign corporation that is related, directly or indirectly, to the Fund through stock ownership, and (5) the holder satisfies the certification requirements described
below.

To satisfy the certification requirements, either (1) the holder of any debt securities must certify, under
penalties of perjury, that such holder is a non-U.S. person and must provide such owner’s name, address and taxpayer identification number, if any, on IRS Form W-8BEN or W-8BEN-E, or (2) a securities clearing organization, bank or other
financial institution that holds customer securities in the ordinary course of its trade or business and holds the debt securities on behalf of the holder thereof must certify, under penalties of perjury, that it has received a valid and properly
executed IRS Form W-8BEN or W-8BEN-E from the beneficial holder and comply with certain other requirements. Special certification rules apply for debt securities held by a foreign partnership and other intermediaries.

Interest on debt securities received by a non-U.S. Holder that is not excluded from U.S. federal withholding tax under the portfolio
interest exemption as described above generally will be subject to withholding at a 30% rate, except where (1) the interest is effectively connected with the conduct of a U.S. trade or business, in which case the interest will generally be
subject to U.S. income tax on a net basis at graduated rates as applicable to U.S. holders generally (and, in the case of corporate non-U.S. Holders, may be subject to an additional 30% branch profits tax) or (2) a non-U.S. Holder can claim the
benefits of an applicable income tax treaty to reduce or eliminate such withholding tax. To claim the benefit of an income tax treaty or to claim an exemption from withholding because the interest is effectively connected with a U.S. trade or
business, a non-U.S. Holder must timely provide the appropriate, properly executed IRS forms. These forms may be required to be periodically updated. Also, a non-U.S. Holder who is claiming the benefits of an income tax treaty may be required to
obtain a U.S. taxpayer identification number and to provide certain documentary evidence issued by foreign governmental authorities to prove residence in the foreign country.

Any capital gain that a non-U.S. Holder realizes on a sale, exchange or other disposition of debt securities generally will be exempt from United States federal income tax, including withholding tax. This
exemption will not apply to a holder whose gain is effectively connected with their conduct of a trade or business in the U.S. or who is an individual holder and is present in the U.S. for a period or periods aggregating 183 days or more in the
taxable year of the disposition and, in each case, certain other conditions are met.

See “Information Reporting and
Backup Withholding” above for a general discussion of information reporting and backup withholding requirements applicable to non-U.S. Holders.

Other Tax Matters

Other Reporting and Withholding
Requirements.    Sections 1471-1474 of the Code and the U.S. Treasury and IRS guidance issued thereunder (collectively, “FATCA”) generally require the Fund to obtain information sufficient to identify the status of
each of its shareholders and holders of its debt securities under FATCA or under an applicable intergovernmental agreement (an “IGA”) between the United States and a foreign government. If a shareholder or holder of debt securities fails
to provide the required information or otherwise fails to comply with FATCA or an IGA, the Fund may be required to withhold under FATCA at a rate of 30% with respect to that holder on ordinary dividends and interest payments. The IRS and the
Department of Treasury have issued proposed regulations providing that these withholding rules will not be applicable to the gross proceeds of share redemptions or capital gains dividends that the Fund pays. If a payment by the Fund is subject to
FATCA withholding, the Fund is required to withhold even if such payment would otherwise be exempt from withholding under the rules applicable to non-U.S. persons. Each prospective investor is urged to consult its tax adviser regarding the
applicability of FATCA and any other reporting requirements with respect to the prospective investor’s own situation, including investments through an intermediary.

Medicare Tax on Certain Investment Income.    Certain noncorporate taxpayers are subject to an additional tax of 3.8% with respect to the lesser of (1) their “net
investment income” (or undistributed “net investment income” in the case of an estate or trust) or (2) the excess of their “modified adjusted gross income” over a

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threshold amount ($250,000 for married persons filing jointly and $200,000 for single taxpayers). For this purpose, “net investment income” includes interest, dividends (including
dividends paid with respect to shares), annuities, royalties, rent, net gain attributable to the disposition of property not held in a trade or business (including net gain from the sale, exchange or other taxable disposition of shares) and certain
other income, but will be reduced by any deductions properly allocable to such income or net gain.

Alternative Minimum Tax

Investors may be subject to the federal alternative minimum tax on their income (including taxable income from the Fund), depending on
their individual circumstances.

NET ASSET VALUE

Net asset value per share is determined no less frequently than the close of regular session trading on the NYSE (usually 4:00 p.m.,
Eastern time), on the last business day in each week, or such other time as the Fund may determine. Net asset value is calculated by dividing the value of all of the securities and other assets of the Fund, less its liabilities (including accrued
expenses and indebtedness) and the aggregate liquidation value of any outstanding preferred shares, by the total number of common shares outstanding. Currently, the net asset values of shares of publicly traded closed-end investment companies
investing in debt securities are published in Barron’s and periodic publications of The Wall Street Journal.

The
valuation of the Fund’s portfolio securities is in accordance with policies and procedures adopted by and under the ultimate supervision of the Board of Trustees. Securities for which market quotations are readily available will be valued using
the market value of those securities. Securities for which market quotations are not readily available will be fair valued in accordance with policies and procedures adopted by and under the ultimate supervision of the Board of Trustees. The method
by which a security may be fair valued will depend on the type of security and the circumstances under which the security is being fair valued.

Portfolio securities that are traded on U.S. securities exchanges, except option securities, are valued at the last current reported sales price at the time the Fund determines its NAV. Securities traded
in the over-the-counter market and quoted on The Nasdaq Stock Market are valued at the Nasdaq Official Closing Price, as determined by Nasdaq, or lacking a Nasdaq Official Closing Price, the last current reported sale price on Nasdaq at the time the
Fund determines its NAV.

When a last sale or closing price is not available, equity securities, other than option
securities, that are traded on a U.S. securities exchange and other equity securities traded in the over-the-counter market are valued at the mean between the most recent bid and asked quotations in accordance with guidelines adopted by the Board of
Trustees. Each option security traded on a U.S. securities exchange is valued at the mid-point of the consolidated bid/ask quote for the option security, also in accordance with guidelines adopted by the Board of Trustees. Each over-the-counter
option that is not traded through the Options Clearing Corporation is valued based on a quotation provided by the counterparty to such option under the ultimate supervision of the Board of Trustees.

Fixed income securities and certain convertible preferred securities are generally traded in the over-the-counter market and are valued
based on evaluations provided by independent pricing services or by dealers who make markets in such securities. Valuations of such fixed income securities and certain convertible preferred securities consider yield or price of equivalent securities
of comparable quality, coupon rate, maturity, type of issue, trading characteristics and other market data and do not rely exclusively upon exchange or over-the-counter prices.

Trading on European and Far Eastern exchanges and over-the-counter markets is typically completed at various times before the close of business on each day on which the NYSE is open. Each security trading
on these exchanges or over-the-counter markets may be valued utilizing a systematic fair valuation model provided by an independent pricing service approved by the Board of Trustees. The valuation of each security that meets certain criteria in
relation to the valuation model is systematically adjusted to reflect the impact of movement in

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the U.S. market after the foreign markets close. Securities that do not meet the criteria, or that are principally traded in other foreign markets, are valued as of the last reported sale price
at the time the Fund determines its NAV, or when reliable market prices or quotations are not readily available, at the mean between the most recent bid and asked quotations as of the close of the appropriate exchange or other designated time.
Trading of foreign securities may not take place on every NYSE business day. In addition, trading may take place in various foreign markets on Saturdays or on other days when the NYSE is not open and on which the Fund’s NAV is not calculated.

If the pricing committee, whose members are appointed by the Board of Trustees and which is comprised of officers of the
Fund and employees of Calamos, determines that the valuation of a security, in accordance with the methods described above, is not reflective of a fair value for such security, the security is valued at a fair value by the pricing committee, under
the ultimate supervision of the Board of Trustees, following the guidelines and/or procedures adopted by the Board of Trustees.

The Fund also may use fair value pricing, pursuant to guidelines adopted by the Board of Trustees and under the ultimate supervision of
the Board of Trustees, if trading in a security is halted or if the value of a security it holds is materially affected by events occurring before the Fund’s pricing time but after the close of the primary market or exchange on which the
security is listed. Those procedures may utilize valuations furnished by pricing services approved by the Board of Trustees, which may be based on market transactions for comparable securities and various relationships between securities that are
generally recognized by institutional traders, a computerized matrix system, or appraisals derived from information concerning the securities or similar securities received from recognized dealers in those securities.

When fair value pricing of securities is employed, the prices of securities used by the Fund to calculate its NAV may differ from market
quotations or official closing prices. In light of the judgment involved in fair valuations, there can be no assurance that a fair value assigned to a particular security is accurate.

DIVIDENDS AND DISTRIBUTIONS ON COMMON SHARES;

AUTOMATIC DIVIDEND REINVESTMENT PLAN

Dividends and Distributions on Common Shares

The Fund intends to
distribute to common shareholders all or a portion of its net investment income monthly and net realized capital gains, if any, at least annually.

On November 4, 2008, the Commission granted Calamos, on behalf of itself and certain registered closed-end funds that it manages, including the Fund, or may manage in the future, an order granting an
exemption from Section 19(b) of, and Rule 19b-1 under, the 1940 Act to conditionally permit the Fund to make periodic distributions of long-term capital gains with respect to the Fund’s outstanding common shares as frequently as twelve
times each year, so long as it complies with the conditions of the order and maintains in effect a distribution policy with respect to its common shares calling for periodic distributions of an amount equal to a fixed amount per share, a fixed
percentage of market price per share or a fixed percentage of the Fund’s net asset value per share (the “Managed Distribution Policy”).

As of January 1, 2019-2020, the Fund adopted such Managed Distribution Policy. Pursuant to such policy, the Fund currently makes monthly distributions to common shareholders stated in terms of a fixed
cent per common share distribution rate that would be composed of, in addition to net investment income, supplemental amounts generally representing realized capital gains or, possibly, returns of capital representing either unrealized capital gains
or a return of original investment. Monthly distributions, including such supplemental amounts, are sometimes referred to as “managed distributions.”

The Fund will seek to establish a distribution rate that roughly corresponds to the Adviser’s projections of the total return that could reasonably be expected to be generated by the Fund over an
extended period of time, although the distribution rate will not be solely dependent on the amount of income earned or capital gains realized by the Fund. Calamos, in making such projections, may consider long-term historical returns and a

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variety of other factors. If, for any monthly distribution, net investment income and net realized capital gains were less than the amount of the distribution, the difference would be distributed
from the Fund’s assets. In addition, in order to make such distributions, the Fund might have to sell a portion of its investment portfolio at a time when independent investment judgment might not dictate such action. The Fund’s final
distribution for each calendar year will include any remaining net investment income undistributed during the year and may include any remaining net realized capital gains undistributed during the year. The Fund’s actual financial performance
will likely vary significantly from quarter-to-quarter and from year-to-year, and there may be extended periods of up to several years when the distribution rate will exceed the Fund’s actual total returns. The Fund’s projected or actual
distribution rate is not a prediction of what the Fund’s actual total returns will be over any specific future period.

As
portfolio and market conditions change, the rate of distributions on the common shares and the Fund’s distribution policy could change. To the extent that the total return of the Fund exceeds the distribution rate for an extended period, the
Fund may be in a position to increase the distribution rate or distribute supplemental amounts to shareholders. Conversely, if the total return of the Fund is less than the distribution rate for an extended period of time, the Fund will effectively
be drawing upon its net assets to meet payments prescribed by its distribution policy. The rate may be modified by the Fund’s Board from time to time.

To the extent the Fund distributes an amount in excess of the Fund’s current and accumulated earnings and profits, such excess, if any (the “Excess”), will be treated by a shareholder for
federal income tax purposes as a tax-free return of capital to the extent of the shareholder’s adjusted tax basis in their shares and thereafter as a gain from the sale or exchange of such shares. See “Certain Federal Income Tax
Matters.” Any such distributions made by the Fund will reduce the shareholder’s adjusted tax basis in their shares to the extent that the distribution constitutes a return of capital during any calendar year, and thus could potentially
subject the shareholder to capital gains taxation in connection with the sale of Fund shares, even if those shares are sold at a price that is lower than the shareholder’s original investment price. To the extent that the Fund’s
distributions exceed the Fund’s current and accumulated earnings and profits, the distribution payout rate will exceed the yield generated from the Fund’s investments. There is no guarantee that the Fund will realize capital gain in any
given year, nor that the Fund’s distribution rates will equal in any period the Fund’s net investment income. Pursuant to the requirements of the 1940 Act and other applicable laws, a notice will accompany each monthly distribution with
respect to the estimated source of the distribution made. Distributions are subject to recharacterization for federal income tax purposes after the end of the fiscal year.

For U.S. federal income tax purposes, the Fund is required to distribute substantially all of its net investment income and net realized capital gains each year to both reduce its federal income tax
liability and to avoid a potential excise tax. Accordingly, the Fund intends to distribute all or substantially all of its net investment income and all net realized capital gains, if any. Therefore, the Fund’s final distribution with respect
to each calendar year would include any remaining net investment income and net realized capital gains, if any, undistributed during the year.

In the event the Fund distributed an Excess, such distribution would decrease the Fund’s managed assets and, therefore, have the likely effect of increasing the Fund’s expense ratio. There is a
risk that the Fund would not eventually realize capital gains in an amount corresponding to a distribution of the Excess.

Pursuant to and in reliance on the order granted by the Commission, under the Managed Distribution Policy, the Fund is required to:

implement certain compliance review and reporting procedures with respect to the Managed Distribution Policy;

include in each notice to shareholders that accompanies distributions certain information in addition to the information currently required by
Section 19(a) of and Rule 19a-1 under the 1940 Act;

include disclosure regarding the Managed Distribution Policy on the inside front cover of each annual and semi-annual report to shareholders;

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provide the Fund’s total return in relation to changes in NAV in the financial highlights table and in any discussion about the Fund’s total
return in each prospectus and annual and semi-annual report to shareholders;

include the information contained in each notice to shareholders that accompanies distributions in: (a) communications regarding the Managed
Distribution Policy to shareholders, prospective shareholders and third-party information providers; (b) a press release issued contemporaneously with the issuance of the notice; (c) an exhibit to the Fund’s next report filed with the
Commission on Form N-CSR; and (d) a statement posted prominently on its website; and

take certain steps to ensure the delivery of the notices accompanying distributions to beneficial owners whose Fund shares are held through a financial
intermediary.

In addition, if the Fund’s common shares were to trade at a significant premium to NAV
following the implementation of the Managed Distribution Policy, and certain other circumstances were present, the Fund’s Board of Trustees would be required to determine whether to approve or disapprove the continuation, or continuation after
amendment, of the Managed Distribution Policy. Finally, pursuant to the order, the Fund would not be permitted to make a public offering of common shares other than:

a rights offering below NAV to holders of the Fund’s common shares;

an offering in connection with a dividend reinvestment plan, merger, consolidation, acquisition, spin-off or reorganization of the Fund; or

an offering other than those described above, unless, with respect to such other offering:

the Fund’s average annual distribution rate for the six months ending on the last day of the month ended immediately prior to the most recent
distribution record date, expressed as a percentage of NAV per share as of such date, is no more than one percentage point greater than the Fund’s average annual total return for the five-year period ending on such date; and

the transmittal letter accompanying any registration statement filed with the Commission in connection with such offering discloses that the Fund has
received an order under Section 19(b) of the 1940 Act to permit it to make periodic distributions of long-term capital gains with respect to its common stock as frequently as twelve times each year, and as frequently as distributions are
specified in accordance with the terms of any outstanding preferred stock that such fund may issue.

The
relief described above will expire on the effective date of any amendment to Rule 19b-1 under the 1940 Act that provides relief permitting certain closed-end investment companies to make periodic distributions of long-term capital gains with respect
to their outstanding common stock as frequently as twelve times each year. Under the Managed Distribution Policy, if, for any distribution, undistributed net investment income and net realized capital gains were less than the amount of the
distribution, the difference would be distributed from the Fund’s other assets. In addition, in order to make such distributions, the Fund might have to sell a portion of its investment portfolio at a time when independent investment judgment
might not dictate such action.

Under the 1940 Act, the Fund is not permitted to incur indebtedness unless immediately after
such incurrence the Fund has an asset coverage of at least 300% of the aggregate outstanding principal balance of indebtedness. Additionally, under the 1940 Act, the Fund generally may not declare any dividend or other distribution upon any class of
its shares, or purchase any such shares, unless the aggregate indebtedness of the Fund has, at the time of the declaration of any such dividend or distribution or at the time of any such purchase, an asset coverage of at least 300% after deducting
the amount of such dividend, distribution, or purchase price, as the case may be, except that dividends may be declared upon any preferred shares if such indebtedness has an asset coverage of at least 200% at the time of declaration thereof after
deducting the amount of the dividend. This limitation does not apply to certain privately placed debt.

While any preferred
shares are outstanding, the Fund may not declare any dividend or other distribution on its common shares, unless at the time of such declaration, (1) all accumulated preferred dividends have been paid

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and (2) the net asset value of the Fund’s portfolio (determined after deducting the amount of such dividend or other distribution) is at least 200% of the liquidation value of the
outstanding preferred shares (expected to be equal to the original purchase price per share plus any accumulated and unpaid dividends thereon).

In addition to the limitations imposed by the 1940 Act described above, certain lenders may impose additional restrictions on the payment of dividends or distributions on common shares in the event of a
default on the Fund’s borrowings. If the Fund’s ability to make distributions on its common shares is limited, such limitation could, under certain circumstances, impair the ability of the Fund to maintain its qualification for federal
income taxation as a regulated investment company and to reduce or eliminate tax at the Fund level, which would have adverse tax consequences for shareholders. See “Leverage” and “Certain Federal Income Tax Matters.”

See “— Automatic Dividend Reinvestment Plan” for information concerning the manner in which dividends and distributions to
common shareholders may be automatically reinvested in common shares. Dividends and distributions are taxable to shareholders for federal income tax purposes whether they are reinvested in shares of the Fund or received in cash.

The yield on the Fund’s common shares may vary from period to period depending on factors including, but not limited to, market
conditions, the timing of the Fund’s investment in portfolio securities, the securities comprising the Fund’s portfolio, changes in interest rates including changes in the relationship between short-term rates and long-term rates, the
amount and timing of the use of borrowings and other leverage by the Fund, the effects of leverage on the common shares discussed above under “Leverage,” the timing of the investment of leverage proceeds in portfolio securities, the
Fund’s net assets and its operating expenses. Consequently, the Fund cannot guarantee any particular yield on its common shares and the yield for any given period is not an indication or representation of future yields on the Fund’s common
shares.

Automatic Dividend Reinvestment Plan

Pursuant to the Plan, unless a common shareholder is ineligible or elects otherwise, all dividend and capital gains on common shares distributions are automatically reinvested by Computershare Shareowner
Services LLC, a subsidiary of Computershare Limited, as agent for shareholders in administering the Plan (“Plan Agent”), in additional common shares of the Fund. Shareholders who elect not to participate in the Plan will receive all
dividends and distributions payable in cash paid by check mailed directly to the shareholder of record (or, if the shares are held in street or other nominee name, then to such nominee) by Plan Agent, as dividend paying agent. Shareholders may elect
not to participate in the Plan and to receive all dividends and distributions in cash by sending written instructions to Plan Agent, as dividend paying agent, at the address set forth below. Participation in the Plan is completely voluntary and may
be terminated or resumed at any time without penalty by giving notice in writing to the Plan Agent; such termination will be effective with respect to a particular dividend or distribution if notice is received prior to the record date for the
applicable distribution.

Whenever the Fund declares a dividend or distribution payable either in common shares or in cash,
non-participants in the Plan will receive cash, and participants in the Plan will receive the equivalent in shares of common shares. The common shares are acquired by the Plan Agent for the participant’s account, depending upon the
circumstances described below, either (i) through receipt of additional common shares from the Fund (“newly issued shares”) or (ii) by purchase of outstanding common shares on the open market (“open-market purchases”)
on Nasdaq or elsewhere. If, on the payment date, the net asset value per share of the common shares is equal to or less than the market price per common share plus estimated brokerage commissions (such condition being referred to herein as
“market premium”), the Plan Agent will receive newly issued common shares from the Fund for each participant’s account. The number of newly issued common shares to be credited to the participant’s account will be determined by
dividing the dollar amount of the dividend or distribution by the greater of (i) the net asset value per common share on the payment date, or (ii) 95% of the market price per common share on the payment date.

If, on the payment date, the net asset value per common share exceeds the market price plus estimated brokerage commissions (such
condition being referred to herein as “market discount”), the Plan Agent has until

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the last business day before the next date on which the shares trade on an “ex-dividend” basis or in no event more than 30 days after the payment date (“last purchase date”)
to invest the dividend or distribution amount in shares acquired in open-market purchases. It is contemplated that the Fund will pay monthly income dividends. Therefore, the period during which open-market purchases can be made will exist only from
the payment date on the dividend through the date before the next ex-dividend date, which typically will be approximately ten days. The weighted average price (including brokerage commissions) of all common shares purchased by the Plan Agent as Plan
Agent will be the price per common share allocable to each participant. If, before the Plan Agent has completed its open-market purchases, the market price of a common share exceeds the net asset value per share, the average per share purchase price
paid by the Plan Agent may exceed the net asset value of the Fund’s shares, resulting in the acquisition of fewer shares than if the dividend had been paid in newly issued shares on the payment date. Because of the foregoing difficulty with
respect to open-market purchases, the Plan provides that if the Plan Agent is unable to invest the full dividend amount in open-market purchases during the purchase period or if the market discount shifts to a market premium during the purchase
period, the Plan Agent will cease making open-market purchases and will invest the uninvested portion of the dividend or distribution amount in newly issued shares at the close of business on the last purchase date.

The Plan Agent maintains all shareholders’ accounts in the Plan and furnishes written confirmation of each acquisition made for the
participant’s account as soon as practicable, but in no event later than 60 days after the date thereof. Shares in the account of each Plan participant will be held by the Plan Agent in non-certificated form in the Plan Agent’s name or
that of its nominee, and each shareholder’s proxy will include those shares purchased or received pursuant to the Plan. The Plan Agent will forward all proxy solicitation materials to participants and vote proxies for shares held pursuant to
the Plan first in accordance with the instructions of the participants then with respect to any proxies not returned by such participant, in the same proportion as the Plan Agent votes the proxies returned by the participants.

There will be no brokerage charges with respect to common shares issued directly by the Fund as a result of dividends or distributions
payable either in shares or in cash. However, each participant will pay a pro rata share of brokerage commissions incurred with respect to the Plan Agent’s open-market purchases in connection with the reinvestment of dividends or distributions.
If a participant elects to have the Plan Agent sell part or all of his or her common shares and remit the proceeds, such participant will be charged his or her pro rata share of brokerage commissions on the shares sold, plus a $15.00 transaction
fee.

The automatic reinvestment of dividends and distributions will not relieve participants of any federal, state or
local income tax that may be payable (or required to be withheld) on such dividends. See “Certain Federal Income Tax Matters.”

Shareholders participating in the Plan may receive benefits not available to shareholders not participating in the Plan. If the market price plus commissions of the Fund’s shares is higher than the
net asset value, participants in the Plan will receive shares of the Fund at less than they could otherwise purchase them and will have shares with a cash value greater than the value of any cash distribution they would have received on their
shares. If the market price plus commissions is below the net asset value, participants receive distributions of shares with a net asset value greater than the value of any cash distribution they would have received on their shares. However, there
may be insufficient shares available in the market to make distributions in shares at prices below the net asset value. Also, since the Fund does not redeem its shares, the price on resale may be more or less than the net asset value. See
“Certain Federal Income Tax Matters” for a discussion of federal income tax consequences of the Plan.

Experience under the Plan may indicate that changes are desirable. Accordingly, the Fund reserves the right to amend or terminate the Plan
if in the judgment of the Board of Trustees such a change is warranted. The Plan may be terminated by the Plan Agent or the Fund upon notice in writing mailed to each participant at least 60 days prior to the effective date of the termination.
Upon any termination, the Plan Agent will cause a certificate or certificates to be issued for the full shares held by each participant under the Plan and cash adjustment for any fraction of a common share at the then current market value of the
common shares to be delivered to him or her. If preferred, a participant may request the sale of all of the common shares held by the

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Plan Agent in his or her Plan account in order to terminate participation in the Plan. If such participant elects in advance of such termination to have the Plan Agent sell part or all of his or
her shares, the Plan Agent is authorized to deduct from the proceeds a $15.00 fee plus the brokerage commissions incurred for the transaction. If a participant has terminated his or her participation in the Plan but continues to have common shares
registered in his or her name, he or she may re-enroll in the Plan at any time by notifying the Plan Agent in writing at the address below. The terms and conditions of the Plan may be amended by the Plan Agent or the Fund at any time but, except
when necessary or appropriate to comply with applicable law or the rules or policies of the Commission or any other regulatory authority, only by mailing to each participant appropriate written notice at least 30 days prior to the effective date
thereof. The amendment shall be deemed to be accepted by each participant unless, prior to the effective date thereof, the Plan Agent receives notice of the termination of the participant’s account under the Plan. Any such amendment may include
an appointment by the Plan Agent of a successor Plan Agent, subject to the prior written approval of the successor Plan Agent by the Fund. There is no direct service charge to participants in the Plan; however, the Fund reserves the right to amend
the Plan to include a service charge payable by the participants. Since investors can participate in the Plan only if their broker or nominee participates in our Plan, you should contact your broker or nominee to confirm that you are eligible to
participate in the Plan.

For more information, please direct all correspondence concerning the Plan to the Plan Agent at P.O.
Box 30170, College Station, TX 77842-3170.

DESCRIPTION OF SECURITIES

The Fund is authorized to issue an unlimited number of common shares, without par value. The Fund is also authorized to issue preferred
shares and debt securities. As of January 31, 2020, the Fund had 70,923,815 common shares outstanding and MRP Shares outstanding in the following amounts: 1,330,000 Series A MRP Shares, 1,330,000 Series B MRP Shares, and 1,340,000 Series C MRP
Shares. As of such date, the Fund had not issued any debt securities. Subject to the restrictions under the 1940 Act, the Board of Trustees may, from time to time, establish additional series or classes of Fund shares and set forth the designations,
preferences, conversion or other rights, voting powers, restrictions, limitations as to dividends, qualifications or terms or conditions of redemption of such shares and pursuant to such classification or reclassification to increase or decrease the
number of authorized shares of any existing class or series but the Board may not change any outstanding shares in a manner materially adverse to such shareholders. The Board of Trustees, without shareholder approval but subject to the governing
documents of the Fund and the MRP Shares, is authorized to amend the Agreement and Declaration of Trust and By-Laws to reflect the terms of any such class or series.

As of January 31, 2020, the Fund had total leverage of approximately $385 million representing approximately 32.5% of the Fund’s managed assets as of that date. The Fund will pay, and
common shareholders will effectively bear, any costs and expenses relating to any borrowings by the Fund, including the financial leverage described above, as well as any additional leverage incurred as a result of this offering. Such costs and
expenses include the higher management fee resulting from the use of any such leverage, offering and/or issuance costs, and interest and/or dividend expense and ongoing maintenance. Borrowings under the SSB Agreement are secured by assets of the
Fund that are held with the Fund’s custodian in a separate account. Interest on the SSB Agreement is charged on the drawn amount at the rate of Overnight LIBOR plus 0.80%, payable monthly in arrears. Interest on overdue amounts or interest on
the drawn amount paid during an event of default will be charged at Overnight LIBOR plus 2.8%. The SSB Agreement has a commitment fee of 0.10% of any undrawn amount. As of January 31, 2020, the interest rate charged under the SSB Agreement was
2.37%.

Under the terms of the SSB Agreement, all securities lent or subject to repurchase transactions through SSB must
be secured continuously by collateral received in cash. Cash collateral held by SSB on behalf of the Fund may be credited against the amounts borrowed under the SSB Agreement, with the effect of reducing interest expense payable by the Fund. Any
amounts credited against the borrowings under the SSB Agreement would count against the Fund’s leverage limitations under the 1940 Act, unless otherwise covered in accordance with SEC Release IC-10666. Under the terms of the SSB Agreement, SSB
will return the value of the collateral to the

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borrower upon the return of the lent securities, which will eliminate the credit against the borrowings under the SSB Agreement and will increase the balance on which the Fund will pay interest.
Under the terms of the SSB Agreement, the Fund will make a variable “net income” payment related to any collateral credited against the borrowings under the SSB Agreement which will be paid to the securities borrower, less any payments due
to the Fund or SSB under the terms of the SSB Agreement. The Fund reserves the right to utilize sources of borrowings in addition to, or in lieu of, the SSB Agreement. See “Prospectus Summary — Use of Leverage by the Fund.”

While unsecured and unsubordinated indebtedness may rank equally with the borrowings under the SSB Agreement in right of
payment, the lender under the agreement, together with the holders of other outstanding secured indebtedness, may, to the exclusion of unsecured creditors, seek recourse against the collateral as security for the borrowings and such other secured
indebtedness until amounts owed under the SSB Agreement and the other secured indebtedness are satisfied in full. All borrowings under the SSB Agreement and the securities lending agreement rank senior to the Fund’s common and preferred shares
as to the payment of interest and distribution of assets upon liquidation.

A declaration of a dividend or other
distribution on or purchase or redemption of any common or preferred shares of the Fund may be prohibited (i) at any time that an event of default under any borrowings has occurred and is continuing, or (ii) if after giving effect to such
declaration, purchase or redemption, the Fund would not meet the 1940 Act asset coverage requirements or any temporary requirements imposed under an order issued by the SEC.

Common Shares

Common shares, when issued and outstanding, will be
legally issued, fully paid and non-assessable and will have no preemptive or conversion rights or rights to cumulative voting, except as described below. The Board has not granted such common shares conversion rights. Shareholders are entitled to
share pro rata in the net assets of the Fund available for distribution to common shareholders upon liquidation of the Fund. Common shareholders are entitled to one vote for each share held.

The Fund’s Agreement and Declaration of Trust provides that the Trustees have the power to cause each shareholder to pay directly, in
advance or arrears, for charges of the Fund’s custodian or transfer, shareholder servicing or similar agent, an amount fixed from time to time by the Trustees, by setting off such charges due from a shareholder from declared but unpaid
dividends owed to such shareholder and/or by reducing the number of shares in the account of such shareholder.

So long as any
preferred shares that may be issued by the Fund are outstanding, holders of common shares will not be entitled to receive any net income of or other distributions from the Fund unless all accumulated dividends on preferred shares have been paid, and
unless asset coverage (as defined in the 1940 Act) with respect to preferred shares would be at least 200% after giving effect to such distributions. See “Leverage.”

The Fund will send unaudited semi-annual financial statements and audited annual financial statements to all of its shareholders.

Other offerings of common shares, if made, will require approval of the Board of Trustees and will be subject to the requirement of the
1940 Act that common shares may not be sold at a price below the then-current net asset value, exclusive of underwriting discounts and commissions, except in limited circumstances including in connection with an offering to existing shareholders.
Common shares may be sold in one or more at the market offerings through sales on Nasdaq at a price equal to or above the Fund’s per share NAV plus any sales commissions paid by the Fund to execute such sales.

Preferred Shares

Preferred shares, when issued and outstanding, will be legally issued, fully paid and non-assessable. Holders of preferred shares will be
entitled to the rights and preferences set out in the documents creating the preferred shares. As a non-fundamental policy, the Fund may not issue preferred shares or borrow money and/or issue debt securities with an aggregate liquidation preference
and aggregate principal amount exceeding 38% of the Fund’s

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managed assets. However, the Board of Trustees reserves the right to issue preferred shares to the extent permitted by the 1940 Act, which currently limits the aggregate liquidation preference of
all outstanding preferred shares to 50% of the value of the Fund’s total assets less the Fund’s liabilities and indebtedness not represented by senior securities. Under the 1940 Act, the Fund may only issue one class of preferred shares.
So long as any preferred shares are outstanding, additional issuances of preferred shares may not have preference or priority over the outstanding preferred shares.

In the event of any voluntary or involuntary liquidation, dissolution or winding up of the Fund, the holders of preferred shares will be entitled to receive a preferential liquidating distribution, which
is expected to equal the original purchase price per preferred share plus accumulated and unpaid dividends, whether or not declared, before any distribution of assets is made to holders of common shares. After payment of the full amount of the
liquidating distribution to which they are entitled, the holders of preferred shares will not be entitled to any further participation in any distribution of assets by the Fund.

The 1940 Act requires that the holders of any preferred shares, voting separately as a single class, have the right to elect at least two
Trustees at all times. The remaining Trustees will be elected by holders of common shares and preferred shares, voting together as a single class. In addition, subject to the prior rights, if any, of the holders of any other class of senior
securities outstanding, the holders of any preferred shares have the right to elect a majority of the Trustees at any time two years’ accumulated dividends on any preferred shares are unpaid. The 1940 Act also requires that, in addition to any
approval by shareholders that might otherwise be required, the approval of the holders of a majority of any outstanding preferred shares, voting separately as a class, would be required to (1) adopt any plan of reorganization that would
adversely affect the preferred shares, and (2) take any action requiring a vote of security holders under Section 13(a) of the 1940 Act, including, among other things, changes in the Fund’s subclassification as a closed-end investment
company or changes in its fundamental investment restrictions. See “Certain Provisions of the Agreement and Declaration of Trust and By-Laws, Including Antitakeover Provisions.” As a result of these voting rights, the Fund’s ability
to take any such actions may be impeded to the extent that there are any preferred shares outstanding. Except as otherwise indicated in this prospectus and except as otherwise required by applicable law, holders of preferred shares have equal voting
rights with holders of common shares (one vote per share, unless otherwise required by the 1940 Act) and will vote together with holders of common shares as a single class.

The affirmative vote of the holders of a majority of the outstanding preferred shares, voting as a separate class, will be required to amend, alter or repeal any of the preferences, rights or powers of
holders of preferred shares so as to affect materially and adversely such preferences, rights or powers, or to increase or decrease the authorized number of preferred shares. The class vote of holders of preferred shares described above will in each
case be in addition to any other vote required to authorize the action in question.

Any redemption or purchase of any
preferred shares by the Fund will reduce the leverage applicable to the common shares, while any resale of shares by the Fund will increase that leverage.

Preferred shares that may be issued by the Fund may or may not be listed on an exchange or automated quotation system. The details on how to buy and sell such securities, along with the other terms of the
securities, will be described in a prospectus supplement. We cannot assure you that any market will exist for our preferred securities or if a market does exist, whether it will provide holders with liquidity.

Debt Securities

General.    Under Delaware law and the Fund’s Agreement and Declaration of Trust, it may borrow money,
without prior approval of holders of common and preferred shares. The Fund may issue debt securities, or other evidence of indebtedness (including bank borrowings or commercial paper) and may secure any such notes or borrowings by mortgaging,
pledging or otherwise subjecting as security our assets to the extent permitted by the 1940 Act or rating agency guidelines. Any borrowings will rank senior to preferred shares and the common shares.

Under the 1940 Act, the Fund may only issue one class of senior securities representing indebtedness other than promissory notes or other
evidences of indebtedness not intended to be publicly distributed, which in the

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aggregate, may represent no more than 33 1/3% of our managed assets. A prospectus supplement and indenture (a summary of the expected terms of which is attached as Appendix A to the statement of
additional information) relating to any debt securities will include specific terms relating to the offering. These terms are expected to include the following:

the form and title of the security;

the aggregate principal amount of the securities;

the interest rate of the securities;

the maturity dates on which the principal of the securities will be payable;

any changes to or additional events of default or covenants;

any optional or mandatory redemption provisions;

identities of, and any changes in trustees, paying agents or security registrar; and

any other terms of the securities.

Interest.    Unless otherwise stated in a prospectus supplement, debt securities will bear interest as generally determined by the Board of Trustees, as more fully described in
the related prospectus supplement. Interest on debt securities shall be payable when due as described in the related prospectus supplement. If we do not pay interest when due, it will trigger an event of default and we will be restricted from
declaring dividends and making other distributions with respect to our common shares and preferred shares.

Limitations.    Under the requirements of the 1940 Act, immediately after issuing any senior securities
representing indebtedness, we must have an asset coverage of at least 300%. Asset coverage means the ratio which the value of our total assets, less all liabilities and indebtedness not represented by senior securities, bears to the aggregate amount
of senior securities representing indebtedness. Other types of borrowings also may result in our being subject to similar covenants in credit agreements.

Events of Default and Acceleration of Maturity of Debt Securities; Remedies.    Unless stated otherwise in the related prospectus supplement, any one of the following events are
expected to constitute an “event of default” for that series under the indenture:

default in the payment of any interest upon a series of debt securities when it becomes due and payable and the continuance of such default for 30
days;

default in the payment of the principal of, or premium on, a series of debt securities at its stated maturity;

default in the performance, or breach, of any covenant or warranty of ours in the indenture, and continuance of such default or breach for a period of
90 days after written notice has been given to us by the trustee;

certain voluntary or involuntary proceedings involving us and relating to bankruptcy, insolvency or other similar laws;

if, on the last business day of each of twenty-four consecutive calendar months, the debt securities have a 1940 Act asset coverage of less than 100%;
or

any other “event of default” provided with respect to a series, including a default in the payment of any redemption price payable on the
redemption date.

Upon the occurrence and continuance of an event of default, the holders of a majority in
principal amount of a series of outstanding debt securities or the trustee may declare the principal amount of that series of debt securities immediately due and payable upon written notice to us. A default that relates only to one series of debt
securities does not affect any other series and the holders of such other series of debt securities are not entitled to receive notice of such a default under the indenture. Upon an event of default relating to bankruptcy, insolvency or other
similar laws, acceleration of maturity occurs automatically with respect to all series. At any time after a

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declaration of acceleration with respect to a series of debt securities has been made, and before a judgment or decree for payment of the money due has been obtained, the holders of a majority in
principal amount of the outstanding debt securities of that series, by written notice to us and the trustee, may rescind and annul the declaration of acceleration and its consequences if all events of default with respect to that series of debt
securities, other than the non-payment of the principal of that series of debt securities which has become due solely by such declaration of acceleration, have been cured or waived and other conditions have been met.

Liquidation Rights.    In the event of (a) any insolvency or bankruptcy case or proceeding, or any
receivership, liquidation, reorganization or other similar case or proceeding in connection therewith, relative to us or to our creditors, as such, or to our assets, or (b) any liquidation, dissolution or other winding up of the Fund, whether
voluntary or involuntary and whether or not involving insolvency or bankruptcy, or (c) any assignment for the benefit of creditors or any other marshalling of assets and liabilities of ours, then (after any payments with respect to any secured
creditor of ours outstanding at such time) and in any such event the holders of debt securities shall be entitled to receive payment in full of all amounts due or to become due on or in respect of all debt securities (including any interest accruing
thereon after the commencement of any such case or proceeding), or provision shall be made for such payment in cash or cash equivalents or otherwise in a manner satisfactory to the holders of the debt securities, before the holders of any common or
preferred stock of the Fund are entitled to receive any payment on account of any redemption proceeds, liquidation preference or dividends from such shares. The holders of debt securities shall be entitled to receive, for application to the payment
thereof, any payment or distribution of any kind or character, whether in cash, property or securities, including any such payment or distribution which may be payable or deliverable by reason of the payment of any other indebtedness of ours being
subordinated to the payment of the debt securities, which may be payable or deliverable in respect of the debt securities in any such case, proceeding, dissolution, liquidation or other winding up event.

Unsecured creditors of ours may include, without limitation, service providers including Calamos, the Fund’s custodian, the
Fund’s administrator, broker-dealers and the trustee, pursuant to the terms of various contracts with us. Secured creditors of ours may include without limitation SSB and other lenders to the Fund, parties entering into any interest rate swap,
floor or cap transactions, or other similar transactions with us that create liens, pledges, charges, security interests, security agreements or other encumbrances on our assets.

A consolidation, reorganization or merger of the Fund with or into any other company, or a sale, lease or exchange of all or substantially
all of our assets in consideration for the issuance of equity securities of another company shall not be deemed to be a liquidation, dissolution or winding up of the Fund.

Voting Rights.    Debt securities have no voting rights, except to the extent required by law or as otherwise provided in the indenture relating to the acceleration of maturity
upon the occurrence and continuance of an event of default. In connection with any other borrowings (if any), the 1940 Act does in certain circumstances grant to the lenders certain voting rights in the event of default in the payment of interest on
or repayment of principal.

Market.    Our debt securities are not likely to be listed on an
exchange or automated quotation system. The details on how to buy and sell such securities, along with the other terms of the securities, will be described in a prospectus supplement. We cannot assure you that any market will exist for our debt
securities or if a market does exist, whether it will provide holders with liquidity.

Book-Entry, Delivery and
Form.    Unless otherwise stated in the related prospectus supplement, the debt securities will be issued in book-entry form and will be represented by one or more notes in registered global form. The global notes will be
deposited with the trustee as custodian for The Depository Trust Company (“DTC”) and registered in the name of Cede & Co., as nominee of DTC. DTC will maintain the notes in designated denominations through its book-entry
facilities.

Under the expected terms of the indenture, we and the trustee may treat the persons in whose names any notes,
including the global notes, are registered as the owners thereof for the purpose of receiving payments and for any and all other purposes whatsoever. Therefore, so long as DTC or its nominee is the registered owner of the global notes, DTC or such
nominee will be considered the sole holder of outstanding notes under the

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indenture. We or the trustee may give effect to any written certification, proxy or other authorization furnished by DTC or its nominee.

A global note may not be transferred except as a whole by DTC, its successors or their respective nominees. Interests of beneficial owners
in the global note may be transferred or exchanged for definitive securities in accordance with the rules and procedures of DTC. In addition, a global note may be exchangeable for notes in definitive form if:

DTC notifies us that it is unwilling or unable to continue as a depository and we do not appoint a successor within 60 days;

we, at our option, notify the trustee in writing that we elect to cause the issuance of notes in definitive form under the indenture; or

an event of default has occurred and is continuing.

In each instance, upon surrender by DTC or its nominee of the global note, notes in definitive form will be issued to each person that DTC or its nominee identifies as being the beneficial owner of the
related notes.

Under the expected terms of the indenture, the holder of any global note may grant proxies and otherwise
authorize any person, including its participants and persons who may hold interests through DTC participants, to take any action which a holder is entitled to take under the indenture.

RATING AGENCY GUIDELINES

The Rating Agencies, which may assign ratings to our senior securities, impose asset coverage requirements, which may limit our ability to engage in certain types of transactions and may limit our ability
to take certain actions without confirming that such action will not impair the ratings. Any agency that may rate our debt securities or preferred shares is referred to as the “Rating Agency.”

We may, but are not required to, adopt any modification to the guidelines that may hereafter be established by any Rating Agency. Failure
to adopt any modifications, however, may result in a change in the ratings described above or a withdrawal of ratings altogether. In addition, any Rating Agency may, at any time, change or withdraw any rating. The Board may, without shareholder
approval, modify, alter or repeal certain of the definitions and related provisions which have been adopted pursuant to each Rating Agency’s guidelines (“Rating Agency Guidelines”) only in the event we receive written confirmation
from the Rating Agency or Agencies that any amendment, alteration or repeal would not impair the ratings then assigned to the senior securities.

We may be required to satisfy two separate asset maintenance requirements with respect to outstanding rated debt securities and with respect to rated preferred shares: (1) we must maintain assets in
our portfolio that have a value, discounted in accordance with guidelines set forth by each Rating Agency, at least equal to 115% of the aggregate principal amount/liquidation preference of the debt securities/preferred stock, respectively, plus
specified liabilities, payment obligations and other amounts (the “Basic Maintenance Amount”); and (2) we must satisfy the 1940 Act asset coverage requirements.

Basic Maintenance Amounts.    We may be required to maintain, as of each valuation date on which senior securities are outstanding, eligible assets having an aggregate
discounted value at least equal to 115% of the applicable Basic Maintenance Amount, which is calculated separately for debt securities and preferred shares for each Rating Agency that is then rating the senior securities and so requires. If we fail
to maintain eligible assets having an aggregated discounted value at least equal to 115% of the applicable Basic Maintenance Amount as of any valuation date and such failure is not cured, we will be required in certain circumstances to redeem
certain of the senior securities.

The applicable Basic Maintenance Amount is defined in the Rating Agency’s Guidelines.
Each Rating Agency may amend the definition of the applicable Basic Maintenance Amount from time to time.

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The market value of our portfolio securities (used in calculating the discounted value of
eligible assets) is calculated using readily available market quotations when appropriate, and in any event, consistent with our valuation procedures. For the purpose of calculating the applicable Basic Maintenance Amount, portfolio securities are
valued in the same manner as we calculate our NAV. See “Net Asset Value.”

Each Rating Agency’s discount
factors, the criteria used to determine whether the assets held in our portfolio are eligible assets, and the guidelines for determining the discounted value of our portfolio holdings for purposes of determining compliance with the applicable Basic
Maintenance Amount are based on Rating Agency Guidelines established in connection with rating the senior securities. The discount factor relating to any asset, the applicable basic maintenance amount requirement, the assets eligible for inclusion
in the calculation of the discounted value of our portfolio and certain definitions and methods of calculation relating thereto may be changed from time to time by the applicable Rating Agency, without our approval, or the approval of our Board of
Trustees or shareholders.

A Rating Agency’s Guidelines will apply to the senior securities only so long as that Rating
Agency is rating such securities. In connection with obtaining a rating, we will pay certain fees to Moody’s, Fitch and any other Rating Agency that may provide a rating for the senior securities. The ratings assigned to the senior securities
are not recommendations to buy, sell or hold the senior securities. Such ratings may be subject to revision or withdrawal by the assigning Rating Agency at any time.

1940 Act Asset Coverage.    We are also required to maintain, with respect to senior securities, as of the last business day on any month in which any senior securities are
outstanding, asset coverage of at least 300% for debt securities and 200% for preferred stock (or such other percentage as may in the future be specified in or under the 1940 Act or in any order granted by the Commission as the minimum asset
coverage for senior securities representing shares of a closed-end investment company as a condition of declaring dividends on its common stock). If we fail to maintain the applicable 1940 Act asset coverage as of the last business day of any month
and such failure is not cured as of the last business day of the following month (the “Asset Coverage Cure Date”), we may be required to redeem certain senior securities.

Notices.    Under the current Rating Agency Guidelines, in certain circumstances, we may be required to deliver
to any Rating Agency which is then rating the senior securities (1) a certificate with respect to the calculation of the applicable Basic Maintenance Amount; (2) a certificate with respect to the calculation of the applicable 1940 Act
asset coverage and the value of our portfolio holdings; and (3) a letter prepared by our independent accountants regarding the accuracy of such calculations.

Notwithstanding anything herein to the contrary, the Rating Agency Guidelines, as they may be amended from time to time by each Rating Agency will be reflected in a written document and may be amended by
each Rating Agency without the vote, consent or approval of the Fund, the Board of Trustees or any shareholder of the Fund.

A
copy of the current Rating Agency Guidelines will be provided to any holder of rated, senior securities promptly upon request made by such holder to the Fund by writing the Fund at 2020 Calamos Court, Naperville, Illinois 60563.

CERTAIN PROVISIONS OF THE AGREEMENT AND DECLARATION OF TRUST AND BY-LAWS, INCLUDING ANTITAKEOVER
PROVISIONS

The Fund’s Agreement and Declaration of Trust includes provisions that could have the effect of limiting
the ability of other entities or persons to acquire control of the Fund or to change the composition of its Board of Trustees and could have the effect of depriving shareholders of an opportunity to sell their shares at a premium over prevailing
market prices by discouraging a third party from seeking to obtain control of the Fund. These provisions, however, have the advantage of potentially requiring persons seeking control of the Fund to negotiate with our management regarding the price
to be paid and facilitating the continuity of the Fund’s investment objective and policies. The Board of Trustees of the Fund has considered these provisions and concluded that they are in the best interests of the Fund.

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The Board of Trustees is divided into three classes. The terms of the Trustees of the
different classes are staggered. A Trustee may be removed from office with or without cause (1) at any time by a written instrument signed by at least two-thirds of the then Trustees, specifying the effective date of removal, or (2) by a
vote of at least a majority of the then Trustees if such removal is approved by the holders of at least two-thirds of the outstanding shares entitled to vote with respect to the election of such Trustee and present in person or by proxy at a meeting
of shareholders called for such purpose.

In addition, subject to certain exceptions in the Agreement and Declaration of Trust,
the Agreement and Declaration of Trust requires the affirmative vote of at least 75% of the outstanding shares entitled to vote on the matter for the Fund to merge or consolidate with any other corporation, association, trust or other organization
or to sell, lease or exchange all or substantially all of the Fund’s assets; unless such action has been approved by the affirmative vote of at least 75% of the Trustees then in office, in which case, the affirmative vote of a majority of the
outstanding shares entitled to vote on the matter is required.

In addition, conversion of the Fund to
an open-end investment company would require an amendment to the Fund’s Agreement and Declaration of Trust. Such an amendment would require the favorable vote of a majority of the then Trustees followed by a favorable vote of the
holders of at least 75% of the shares of each affected class or series outstanding, voting as separate classes or series (or a majority of the shares outstanding and entitled to vote if the amendment was previously approved by 75% of the Trustees).
Such a vote also would satisfy a separate requirement in the 1940 Act that the change be approved by the shareholders.

Under
the 1940 Act, shareholders of an open-end investment company may require the company to redeem their shares of common stock at any time (except in certain circumstances as authorized by or under the 1940 Act) at their net asset value, less
such redemption charge, if any, as might be in effect at the time of a redemption. If the Fund is converted to an open-end investment company, it could be required to liquidate portfolio securities to meet requests for redemption, and the
common shares would no longer be listed on Nasdaq. Conversion to an open-end investment company would also require changes in certain of the Fund’s investment policies and restrictions. In addition, if then outstanding, the Fund would
be required to redeem all of its outstanding preferred shares prior to conversion to an open-end investment company.

In addition, the Agreement and Declaration of Trust requires the affirmative vote or consent of a majority of the then Trustees followed by the affirmative vote or consent of the holders of at least 75%
of the shares of each affected class or series of the Fund outstanding, voting separately as a class or series, to approve certain transactions with a Principal Shareholder, unless the transaction has been approved by at least 75% of the Trustees,
in which case a majority of the outstanding shares entitled to vote shall be required. For purposes of these provisions, a “Principal Shareholder” refers to any person who, whether directly or indirectly and whether alone or together with
its affiliates and associates, beneficially owns 5% or more of the outstanding shares of any class or series of shares of beneficial interest of the Fund. The 5% holder transactions subject to these special approval requirements are:

the merger or consolidation of the Fund or any subsidiary of the Fund with or into any Principal Shareholder;

the issuance of any securities of the Fund to any Principal Shareholder for cash (other than pursuant to any automatic dividend reinvestment plan); or

the sale, lease or exchange to the Fund or any subsidiary of the Fund in exchange for securities of the Fund, of any assets of any Principal
Shareholder, except assets having an aggregate fair market value of less than $1,000,000, aggregating for the purpose of such computation all assets sold, leased or exchanged in any series of similar transactions within a 12-month period.

The Fund may be terminated by the affirmative vote of not less than 75% of the Trustees then in office by
written notice to the shareholders.

The Fund’s Agreement and Declaration of Trust and By-Laws provide that the
Board of Trustees has the power, to the exclusion of shareholders, to make, alter or repeal any of the By-Laws, except for any By-Law that

79

requires a vote of the shareholders to be amended, adopted or repealed by the terms of the Agreement and Declaration of Trust, By-Laws or applicable law. Neither this provision of the
Agreement and Declaration of Trust, nor any of the foregoing provisions thereof requiring the affirmative vote of 75% of outstanding shares of the Fund, can be amended or repealed except by the vote of such required number of shares.

With respect to proposals by shareholders submitted outside the process of Rule 14a-8 under the Securities Exchange Act of 1934,
as amended (the “Exchange Act”), the Fund’s By-Laws generally require that advance notice be given to the Fund in the event a shareholder desires to nominate a person for election to the Board of Trustees or to transact any
other business at an annual meeting of shareholders. With respect to an annual meeting following the first annual meeting of shareholders, notice of any such nomination or business must be delivered to the principal executive offices of the Fund not
less than 90 calendar days nor more than 120 calendar days prior to the anniversary date of the mailing of the notice for the prior year’s annual meeting (subject to certain exceptions). Any notice by a shareholder must be accompanied by
certain information as provided in the By-Laws, including information regarding the shares held by the shareholder and information regarding the candidate’s background and qualifications to serve as trustee.

PLAN OF DISTRIBUTION

We may offer, from time to time, our common shares, preferred shares or debt securities, and certain of our shareholders may sell our common shares, on an immediate, continuous or delayed basis, in one or
more underwritten public offerings, “at the market” offerings or a combination of both offerings under this prospectus and any related prospectus supplement. The aggregate amount of securities that may be offered by us in connection with
this offering is limited to $100,000,000. Any underwriter or agent involved in the offer and sale of the securities will be named in the applicable prospectus supplement. A prospectus supplement or supplements will also describe the terms of the
offering of the securities, including as applicable: the purchase price of the securities and the proceeds, if any, we will receive from the sale; any overallotment options under which underwriters may purchase additional securities from us; any
agency fees or underwriting discounts and other items constituting agents’ or underwriters’ compensation; the public offering price; any discounts or concessions allowed or re-allowed or paid to dealers; and any securities exchange or
market on which the securities may be listed. Only underwriters named in the prospectus supplement will be underwriters of the securities offered by such prospectus supplement.

Direct Sales

We may sell our common shares, preferred shares or debt
securities, and certain of our shareholders may sell our common shares, directly to, and solicit offers from, institutional investors or others who may be deemed to be underwriters as defined in the 1933 Act for any resales of the securities. If
such an offering occurs, no underwriters or agents would be involved. We, or any selling shareholder, may use electronic media, including the Internet, to sell offered securities directly. The terms of any of those sales will be described in a
prospectus supplement.

If our common shares are to be offered for sale by certain of our shareholders, each prospectus
supplement relating to such offering will indicate the nature of any position, office, or other material relationship which the selling shareholder has had within the past three years with the Fund or any of its predecessors or affiliates, and will
state the amount of securities of the class owned by such shareholder prior to the offering, the amount to be offered for the shareholder’s account, the amount and (if one percent or more) the percentage of the class to be owned by such
shareholder after completion of the offering.

By Agents

We may offer our common shares, preferred shares and debt securities through agents that we or they designate. Any agent involved in the offer and sale will be named and any commissions payable by us to
such agent will be described in the applicable prospectus supplement. Unless otherwise indicated in the prospectus supplement, the agents will be acting on a commercially reasonable efforts basis for the period of their appointment.

80

Sales of our common shares may be made in transactions that are deemed to be “at
the market” as defined in Rule 415 under the 1933 Act, including sales made directly on Nasdaq or sales made to or through a market maker other than on an exchange.

By Underwriters

We may offer and sell securities from time to time to one
or more underwriters who would purchase the securities as principal for resale to the public, either on a firm commitment or best efforts basis. If we sell securities to underwriters, we will execute an underwriting agreement with them at the time
of the sale and will name them in the prospectus supplement. In connection with these sales, the underwriters may be deemed to have received compensation from us in the form of underwriting discounts and commissions. The underwriters also may
receive commissions from purchasers of securities for whom they may act as agent. Unless otherwise stated in the prospectus supplement, the underwriters will not be obligated to purchase the securities unless the conditions set forth in the
underwriting agreement are satisfied, and if the underwriters purchase any of the securities, they will be required to purchase all of the offered securities. The underwriters may sell the offered securities to or through dealers, and those dealers
may receive discounts, concessions or commissions from the underwriters as well as from the purchasers for whom they may act as agent. Any public offering price and any discounts or concessions allowed or reallowed or paid to dealers may be changed
from time to time. Our common shareholders will indirectly bear such fees and expenses as well as any other fees and expenses incurred by us in connection with any sale of securities. Underwriters, dealers and agents that participate in the
distribution of the securities may be deemed to be underwriters under the 1933 Act, and any discounts and commissions they receive from us and any profit realized by them on the resale of the securities may be deemed to be underwriting discounts and
commissions under the 1933 Act. Any such underwriter or agent will be identified and any such compensation received from us will be described in the applicable prospectus supplement.

If a prospectus supplement so indicates, we may grant the underwriters an option to purchase additional shares of common stock at the
public offering price, less the underwriting discounts and commissions, within 45 days from the date of the prospectus supplement, to cover any overallotments.

By Dealers

We may offer and sell securities from time to time to one or
more dealers who would purchase the securities as principal. The dealers then may resell the offered securities to the public at fixed or varying prices to be determined by those dealers at the time of resale. The names of the dealers and the terms
of the transactions with them will be set forth in the applicable prospectus supplement.

General Information

Agents, underwriters, or dealers participating in an offering of securities may be deemed to be underwriters, and any discounts and
commission received by them and any profit realized by them on resale of the offered securities for whom they act as agent may be deemed to be underwriting discounts and commissions under the 1933 Act.

We may offer to sell securities either at a fixed price or at prices that may vary, at market prices prevailing at the time of sale, at
prices related to prevailing market prices, or at negotiated prices.

Ordinarily, each series of offered securities will be a
new issue of securities and will have no established trading market.

To facilitate an offering of common stock in an
underwritten transaction and in accordance with industry practice, the underwriters may engage in transactions that stabilize, maintain, or otherwise affect the market price of the common stock or any other security. Those transactions may include
overallotment, entering stabilizing bids, effecting syndicate covering transactions, and reclaiming selling concessions allowed to an underwriter or a dealer. An overallotment in connection with an offering creates a short position in the common
stock for the

81

underwriter’s own account. An underwriter may place a stabilizing bid to purchase the common stock for the purpose of pegging, fixing, or maintaining the price of the common stock.
Underwriters may engage in syndicate covering transactions to cover overallotments or to stabilize the price of the common stock by bidding for, and purchasing, the common stock or any other securities in the open market in order to reduce a short
position created in connection with the offering. The managing underwriter may impose a penalty bid on a syndicate member to reclaim a selling concession in connection with an offering when the common stock originally sold by the syndicate member is
purchased in syndicate covering transactions or otherwise.

Any of these activities may stabilize or maintain the market price
of the securities above independent market levels. The underwriters are not required to engage in these activities, and may end any of these activities at any time.

Any underwriters to whom the offered securities are sold for offering and sale may make a market in the offered securities, but the underwriters will not be obligated to do so and may discontinue any
market-making at any time without notice. The offered securities may or may not be listed on a securities exchange. We cannot assure you that there will be a liquid trading market for the offered securities.

Under agreements entered into with us, underwriters and agents may be entitled to indemnification by us against certain civil liabilities,
including liabilities under the 1933 Act, or to contribution by us for payments the underwriters or agents may be required to make.

The underwriters, agents, and their affiliates may engage in financial or other business transactions with us and our subsidiaries in the ordinary course of business.

The maximum commission or discount to be received by any member of the Financial Industry Regulatory Authority or independent
broker-dealer will not be greater than eight percent of the initial gross proceeds from the sale of any security being sold.

The aggregate offering price specified on the cover of this prospectus relates to the offering of the securities not yet issued as of the
date of this prospectus.

To the extent permitted under the 1940 Act and the rules and regulations promulgated thereunder, the
underwriters may from time to time act as a broker or dealer and receive fees in connection with the execution of our portfolio transactions after the underwriters have ceased to be underwriters and, subject to certain restrictions, each may act as
a broker while it is an underwriter.

This prospectus and any accompanying prospectus supplement in electronic form may be made
available on the websites maintained by underwriters. The underwriters may agree to allocate a number of securities for sale to their online brokerage account holders. Such allocations of securities for internet distributions will be made on the
same basis as other allocations. In addition, securities may be sold by the underwriters to securities dealers who resell securities to online brokerage account holders.

CUSTODIAN, TRANSFER AGENT, DIVIDEND DISBURSING AGENT AND REGISTRAR

The Fund’s securities and cash are held under a custodian agreement with State Street Bank and Trust Company, 100 Lincoln Street, Boston, Massachusetts 02111. The transfer agent, dividend disbursing
agent and registrar for the Fund’s common shares is Computershare Investor Services, P.O. Box 505000, Louisville, KY 40233-5000.

LEGAL MATTERS

Ropes & Gray LLP
(“Ropes & Gray”) is counsel to the Fund. Richards, Layton & Finger, P.A. (“RLF”) has opined on certain matters of Delaware law relating to the legality of the securities to be offered hereby. If certain legal
matters in connection with an offering of securities are passed upon by counsel for the underwriters of such offering, such matters will be passed upon by counsel to be identified in a prospectus supplement.

82

EXPERTS

The financial highlights included in this prospectus and the financial statements and financial highlights, including the notes thereto,
appearing in the statement of additional information, which is incorporated by reference in its entirety into this prospectus, have been audited by Deloitte & Touche LLP, an independent registered public accounting firm, as stated in their
report, which is also included in the statement of additional information and incorporated by reference herein. Such financial statements and financial highlights are included and incorporated in reliance upon the report and consent of such firm
given upon the firm’s authority as experts in accounting and auditing.

AVAILABLE
INFORMATION

We are subject to the informational requirements of the Exchange Act and the 1940 Act and are required to
file reports, including annual and semi-annual reports, proxy statements and other information with the Commission. These documents are available on the EDGAR database on the Commission’s website at www.sec.gov.

This prospectus does not contain all of the information in our registration statement, including amendments, exhibits, and schedules.
Statements in this prospectus about the contents of any contract or other document are not necessarily complete and in each instance reference is made to the copy of the contract or other document filed as an exhibit to the registration statement,
each such statement being qualified in all respects by this reference.

Additional information about us can be found in our
registration statement (including amendments, exhibits, and schedules) on Form N-2 filed with the Commission. The Commission maintains a website (http://www.sec.gov) that contains our registration statement, other documents incorporated by
reference, and other information we have filed electronically with the Commission, including proxy statements and reports filed under the Exchange Act.

83

TABLE OF CONTENTS

OF THE STATEMENT OF ADDITIONAL INFORMATION

84

The information in this prospectus supplement is not complete and may be changed. We may not
sell these securities until the registration statement filed with the Securities and Exchange Commission is effective. This prospectus supplement is not an offer to sell these securities and is not soliciting an offer to buy these securities in any
jurisdiction where the offer or sale is not permitted.

SUBJECT TO COMPLETION, DATED [Date]

FORM OF PROSPECTUS SUPPLEMENT

Prospectus Supplement

(To Prospectus dated
                ,         )

Calamos Convertible Opportunities and Income Fund

Up to [                ] Common Shares

Calamos Convertible Opportunities and Income Fund (the “Fund,” “we,” “us,” or “our”) is a diversified, closed-end management investment company that commenced investment operations in June 2002. Our investment objective is to provide total return through a combination of capital appreciation
and current income.

Our common shares are listed on the NASDAQ Global Select Market (“NASDAQ”) under the symbol
“CHI.” As of [                ], the last reported sale price for our common shares was $xx.xx per share. As of
[                ], the last reported net asset value for our common shares was $xx.xx.

Sales of our common shares, if any, under this prospectus supplement and the accompanying prospectus may be made in negotiated transactions or transactions that are deemed to be “at the market”
as defined in Rule 415 under the Securities Act of 1933, as amended (the “1933 Act”), including sales made directly on the NASDAQ or sales made to or through a market maker other than on an exchange.

Per Share
 
  
Total(1)

[Publicofferingprice[Publicofferingprice

$
         
 
  
$

Sales load

$
 
 
  
$

Proceeds to us (before expenses)

$
 
 
  
$

(1)

The aggregate expenses of the offering are estimated to be $    , which represents approximately
$    per share.

The underwriters may also purchase up to an additional
[    ] common shares from the Fund at the public offering price, less underwriting discounts and commissions if any, within [    ] days after the date of this prospectus supplement. If the over-allotment
option is exercised in full, the total proceeds, before expenses, to the Fund would be $[    ] and the total underwriting discounts and commissions would be $[    ]. The common shares will be ready for
delivery on or about [                ].]

Investing in our securities involves certain risks, including the risks associated with the Fund’s use of leverage. You could
lose some or all of your investment. See “Risk Factors” beginning on page [  ] of the accompanying prospectus. You should consider carefully these risks together with all of the other information
contained in this prospectus supplement and the accompanying prospectus before making a decision to purchase our securities.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or determined if this prospectus supplement or the accompanying
prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

[UNDERWRITER(S)]

Prospectus Supplement dated
[                ]

This prospectus supplement, together with the accompanying prospectus, sets forth
concisely the information that you should know before investing. You should read the accompanying prospectus and prospectus supplement, which contain important information, before deciding whether to invest in our securities. You should retain the
accompanying prospectus and prospectus supplement for future reference. A statement of additional information, dated [                ] as supplemented from time to
time, containing additional information, has been filed with the Securities and Exchange Commission (“Commission”) and is incorporated by reference in its entirety into this prospectus supplement and the accompanying prospectus. This
prospectus supplement, the accompanying prospectus and the statement of additional information are part of a “shelf” registration statement that we filed with the Commission. This prospectus supplement describes the specific details
regarding this offering, including the method of distribution. If information in this prospectus supplement is inconsistent with the accompanying prospectus or the statement of additional information, you should rely on this prospectus supplement.
You may request a free copy of the statement of additional information, the table of contents of which is on page [  ] of the accompanying prospectus, request a free copy of our annual and semi-annual reports, request other
information or make shareholder inquiries, by calling toll-free 1-800-582-6959 or by writing to the Fund at 2020
Calamos Court, Naperville, Illinois 60563. The Fund’s annual and semi-annual reports also are available on our website, free of charge, at www.calamos.com, which also provides a link to the Commission’s website, as described below, where
the Fund’s statement of additional information can be obtained. Information included on our website does not form part of this prospectus supplement or the accompanying prospectus. You can review and copy documents we have filed at the
Commission’s Public Reference Room in Washington, D.C. Call 1-202-551-8090 for information. The Commission charges
a fee for copies. You can get the same information free from the Commission’s website (http://www.sec.gov). You may also e-mail requests for these documents to publicinfo@sec.gov or make a
request in writing to the Commission’s Public Reference Section, Washington, D.C. 20549-1520.

Our securities do not
represent a deposit or obligation of, and are not guaranteed or endorsed by, any bank or other insured depository institution and are not federally insured by the Federal Deposit Insurance Corporation, the Federal Reserve Board or any other
government agency.

TABLE OF CONTENTS

Prospectus Supplement

You should rely only on the information contained or incorporated by reference in this prospectus
supplement and the accompanying prospectus in making your investment decisions. We have not authorized any other person to provide you with different or inconsistent information. If anyone provides you with different or inconsistent information, you
should not rely on it. This prospectus supplement and the accompanying prospectus do not constitute an offer to sell or solicitation of an offer to buy any securities in any jurisdiction where the offer or sale is not permitted. The information
appearing in this prospectus supplement and in the accompanying prospectus is accurate only as of the dates on their covers. Our business, financial condition and prospects may have changed since such dates. We will advise investors of any material
changes to the extent required by applicable law.

i

CAUTIONARY NOTICE REGARDING FORWARD-LOOKING STATEMENTS

This prospectus supplement, the accompanying prospectus and the statement of additional information contain “forward-looking
statements.” Forward-looking statements can be identified by the words “may,” “will,” “intend,” “expect,” “estimate,” “continue,” “plan,” “anticipate,” and similar
terms and the negative of such terms. By their nature, all forward-looking statements involve risks and uncertainties, and actual results could differ materially from those contemplated by the forward-looking statements. Several factors that could
materially affect our actual results are the performance of the portfolio of securities we hold, the price at which our shares will trade in the public markets and other factors discussed in our periodic filings with the Commission. Currently known
risk factors that could cause actual results to differ materially from our expectations include, but are not limited to, the factors described in the “Risk Factors” section of the accompanying prospectus. We urge you to review carefully
that section for a more detailed discussion of the risks of an investment in our securities.

Although we believe that the
expectations expressed in our forward-looking statements are reasonable, actual results could differ materially from those projected or assumed in our forward-looking statements. Our future financial condition and results of operations, as well as
any forward-looking statements, are subject to change and are subject to inherent risks and uncertainties, such as those disclosed in the “Risk Factors” section of the accompanying prospectus. All forward-looking statements contained or
incorporated by reference in this prospectus supplement or the accompanying prospectus are made as of the date of this prospectus supplement or the accompanying prospectus, as the case may be. Except for our ongoing obligations under the federal
securities laws, we do not intend, and we undertake no obligation, to update any forward-looking statement.

ii

PROSPECTUS SUPPLEMENT SUMMARY

The following summary contains basic information about us and our securities. It is not complete and may not contain all of the
information you may want to consider. You should review the more detailed information contained in this prospectus supplement and in the accompanying prospectus and in the statement of additional information, especially the information set forth
under the heading “Risk Factors” beginning on page [  ] of the accompanying prospectus.

The Fund

The Fund is a diversified, closed-end management investment company,
with total managed assets of $x.xx billion as of [                ]. We commenced operations in June 2002 following our initial public offering. Our investment
objective is to provide total return through a combination of capital appreciation and current income.

Investment Adviser

Calamos Advisors LLC (the “Adviser” or “Calamos”) serves as our investment adviser. Calamos is
responsible on a day-to-day basis for investment of the Fund’s portfolio in accordance with its investment objective and policies. Calamos makes all
investment decisions for the Fund and places purchase and sale orders for the Fund’s portfolio securities. As of [                ] Calamos managed approximately
$xx.x billion in assets of individuals and institutions. Calamos is a wholly-owned subsidiary of Calamos Investments LLC and an indirect subsidiary of Calamos Asset Management, Inc.

The Fund pays Calamos an annual fee, payable monthly, for its investment management services equal to 0.80% of the Fund’s average
weekly managed assets. “Managed assets” means the total assets of the Fund (including any assets attributable to any leverage that may be outstanding) minus the sum of liabilities (other than debt representing financial leverage). See
“Management of the Fund” on page [  ] of the accompanying prospectus.

The principal business
address of the Adviser is 2020 Calamos Court, Naperville, Illinois 60563.

The Offering

The Fund and Calamos entered into the [                 ]
Agreement with [                ] (“[                 ]”) relating to the
common shares offered by this prospectus supplement and the accompanying prospectus. In accordance with the terms of the [                ] Agreement, we may offer and
sell up to x,xxx,xxx of our common shares, no par value per share, from time to time through [                ] as our agent for the offer and sale of the common shares.

As of [                ], the Fund had
offered and sold xx,xxx,xxx common shares pursuant to a prior sales agreement with [                ], resulting in proceeds (net of all fees, expenses and commissions)
of $xx million. The prior sales agreement with [                ] has been terminated.

Our common shares are listed on the NASDAQ Global Select Market (“NASDAQ”) under the symbol “CHI.” As of
[                ], the last reported sale price for our common shares was $xx.xx.

Sales of our common shares, if any, under this prospectus supplement and the accompanying prospectus may be made in negotiated transactions or transactions that are deemed to be “at the market”
as defined in Rule 415 under the 1933 Act, including sales made directly on the NASDAQ or sales made to or through a market maker other than on an exchange. See “Plan of Distribution” in this prospectus supplement. Our common shares
may not be sold through agents, underwriters or dealers without delivery or deemed delivery of a prospectus and a prospectus supplement describing the method and terms of the offering of our securities. Under the 1940 Act, the Fund may not sell any
common shares at a price below the current net asset value of such common shares, exclusive of any distributing commission or discount.

SUP-1

Use of Proceeds

Unless otherwise specified in this prospectus supplement, we currently intend to use the net proceeds from the sale of our common shares in this offering primarily to invest in accordance with our
investment objective and policies (as described under “Investment Objective and Principal Investment Strategies,” beginning on page [  ] of the accompanying prospectus) within approximately three months of receipt of
such proceeds. We may also use proceeds from the sale of our securities (i) to retire all or a portion of any short-term debt we incur in pursuit of our investment objective and policies, (ii) to redeem any outstanding senior securities,
and (iii) for working capital purposes, including the payment of interest and operating expenses, although there is currently no intent to issue securities primarily for these purposes.

SUP-2

CAPITALIZATION

We may offer and sell up to [                ] of our
common shares, no par value per share. The following table sets forth our capitalization on a historical basis as of                :

Actual
 
  
As Adjusted

Loans(1)

Preferred shares

Common shares, no par value per share, unlimited shares authorized,
[            ] outstanding (actual) shares outstanding (as adjusted)

Undistributed net investment income (loss)

Accumulated net realized gain (loss) on investments, foreign currency transaction, written options and interest rate
swaps

Net unrealized appreciation (depreciation) on investments, foreign currency transaction, written options and interest rate
swaps

Net assets applicable to common shareholders

Total Capitalization

(1)

Figures do not reflect additional structural leverage related to certain securities lending programs, which were $[    ]
million as of [    ].

SUMMARY OF FUND EXPENSES

The following table and example contain information about the costs and expenses that common shareholders will bear
directly or indirectly. In accordance with Commission requirements, the table below shows our expenses, including interest payments on borrowed funds and preferred stock dividend payments, as a percentage of our average net assets as of
[                ], and not as a percentage of gross assets or managed assets.

By showing expenses as a percentage of average net assets, expenses are not expressed as a percentage of all of the assets we invest. The table and example are based on our capital structure as of
[                ]. As of [                ], the Fund had $xxx million in
borrowings outstanding, $[                ] in outstanding preferred shares and additional structural leverage of $xxx million, collectively representing xx.x% of
managed assets.

Shareholder Transaction Expenses

Sales Load (as a percentage of offering price)

[        
]%(1)

Offering Expenses Borne by the Fund (as a percentage of offering price)

[        
]%

Dividend Reinvestment Plan Fees (per sales transaction fee) (2)

[$
15.00
]

Percentage of Average Net
 

 
  
Assets Attributable to

Annual Expenses

Common Shareholders

Management Fee(3)

Interest Payments on Borrowed Funds(4)

Preferred Stock Dividend Payments(5)

Other Expenses(6)

Acquired Fund Fees and Expenses

Total Annual Expenses

SUP-3

Example:

The following example illustrates the expenses that common shareholders would pay on a $1,000 investment in common shares, assuming (1) total annual expenses of [    ]% of net
assets attributable to common shareholders; (2) a 5% annual gross return; and (3) all distributions are reinvested at net asset value:

1 Year
 
  
3 Years
 
  
5 Years
 
  
10 Years

Total Expenses Paid by Common Shareholders(7)

$
[    
]

$
[    
]

$
[    
]

$
[    
]

The example should not be considered a representation of future expenses. Actual expenses may be
greater or less than those assumed. Moreover, our actual rate of return may be greater or less than the hypothetical 5% return shown in the example.

(1)

[Represents the estimated commission with respect to our common shares being sold in this offering, which we will pay to in connection with
sales of common shares effected by              in this offering. While              is entitled to a commission of
        % to         % of the gross sales price for common shares sold, with the exact amount to be agreed upon by the parties, we have assumed, for purposes of this
offering, that              will receive a commission of         % of such gross sales price. This is the only sales load to be paid in connection
with this offering. There is no guarantee that there will be any sales of our common shares pursuant to this prospectus supplement and the accompanying prospectus. Actual sales of our common shares under this prospectus supplement and the
accompanying prospectus, if any, may be less than as set forth in the table. In addition, the price per share of any such sale may be greater or less than the price set forth in the table, depending on the market price of our common shares at the
time of any such sale.]

(2)

Shareholders will pay a $15.00 transaction fee plus a $0.02 per share brokerage charge if they direct the Plan Agent to sell common shares
held in a Plan account. In addition, each participant will pay a pro rata share of brokerage commissions incurred with respect to the Plan Agent’s open-market purchases in connection with the reinvestment of dividends or distributions. If a
participant elects to have the Plan Agent sell part or all of his or her common shares and remit the proceeds, such participant will be charged his or her pro rata share of brokerage commissions on the shares sold. See “Dividends and
Distributions on Common Shares; Automatic Dividend Reinvestment Plan” on page [  ] of the accompanying prospectus.

(3)

The Fund pays Calamos an annual management fee, payable monthly, for its investment management services in an amount equal to 0.80% of the
Fund’s average weekly managed assets. In accordance with the requirements of the Commission, the table above shows the Fund’s management fee as a percentage of average net assets attributable to common shareholders. By showing the
management fee as a percentage of net assets, the management fee is not expressed as a percentage of all of the assets the Fund intends to invest. For purposes of the table, the management fee has been converted to [    ]% of the
Fund’s average weekly net assets as of [    ] by dividing the total dollar amount of the management fee by the Fund’s average weekly net assets (managed assets less outstanding leverage).

(4)

Reflects interest expense paid on $     million in average borrowings under the Fund’s Amended and Restated Liquidity
Agreement with State Street Bank and Trust Company, plus $     million in additional average structural leverage related to certain securities lending programs, as described in the prospectus under “Prospectus Summary —
Use of Leverage by the Fund.”

(5)

Reflects estimated dividend expense on $[    ] million aggregate liquidation preference of mandatory redeemable
preferred shares (“MRP Shares”) outstanding. See “Prospectus Summary — Use of Leverage by the Fund” and “Leverage” in the accompanying prospectus for additional information.

(6)

“Other Expenses” are based on estimated amounts for the current fiscal year.

(7)

The example includes sales load and estimated offering costs.

The purpose of the table and the example above is to help investors understand the fees and expenses that they, as common shareholders,
would bear directly or indirectly. For additional information with respect to our expenses, see “Management of the Fund” on page [  ] of the accompanying prospectus.

SUP-4

MARKET AND NET ASSET VALUE INFORMATION

Our common shares are listed on the NASDAQ Global Select Market (“NASDAQ”) under the symbol “CHI.” Our common shares
commenced trading on the New York Stock Exchange (“NYSE”) in June 2002. On July 2, 2012, the common shares ceased trading on the NYSE and commenced trading on the NASDAQ.

Our common shares have traded both at a premium and a discount to net asset value or NAV. We cannot predict whether our shares will trade
in the future at a premium or discount to NAV. The provisions of the 1940 Act generally require that the public offering price of common shares (less any underwriting commissions and discounts) must equal or exceed the NAV per share of a
company’s common stock (calculated within 48 hours of pricing). Our issuance of common shares may have an adverse effect on prices in the secondary market for our common shares by increasing the number of common shares available, which may put
downward pressure on the market price for our common shares. Shares of common stock of closed-end investment companies frequently trade at a discount from NAV. See “Risk Factors —
Additional Risks to Common Shareholders — Market Discount Risk” on page [    ] of the accompanying prospectus.

The following table sets forth for each of the periods indicated the high and low closing market prices for our common shares on the NASDAQ, the NAV per share and the premium or discount to NAV per share
at which our common shares were trading. NAV is shown for the last business day of each quarter. See “Net Asset Value” on page [    ] of the accompanying prospectus for information as to the determination of our NAV.

Premium/(Discount)
 

 
  
Market Price(1)
 
  
Net AssetValue(2)
 
  
to Net AssetValue(3)

Quarter Ended

High
 
  
Low
 
  
High
 
  
Low

Source: Bloomberg Financial and Fund Accounting Records.

(1)

Based on high and low closing market price per share during the respective quarter and does not reflect commissions.

(2)

Based on the NAV calculated on the close of business on the last business day of each calendar quarter.

(3)

Premium and discount information is shown for the days when the Fund experienced its high and low closing market prices, respectively, per
share during the respective quarter.

The last reported sale price, NAV per common share and percentage
discount to NAV per common share on [                ], were $xx.xx, $xx.xx and (x.xx)%, respectively. As of
[                ], we had xx,xxx,xxx common shares outstanding and managed assets of approximately $x.xx billion.

The following table provides information about our outstanding securities as of
[                ]:

Title of Class

AmountAuthorized
 
  
AmountHeld by theFund or forits Account
 
  
AmountOutstanding

SUP-5

The following table sets forth information regarding the Fund’s outstanding bank
loans and MRP Shares as of the end of each of the Fund’s last ten fiscal years, as applicable. The information in the table shown below comes from the Fund’s financial statements for the fiscal year ended
                , and each of the prior nine years then ended, all of which have been audited by
[                ], the Fund’s independent registered public accounting firm.

Fiscal Year Ended

Total AmountOutstanding
 
  
AssetCoverage(a)
 
  
LiquidatingPreference perPreferred Share(c)
 
  
AverageMarketValue perPreferred Share
 
  
Type ofSeniorSecurity

(a)

Calculated by subtracting the Fund’s total liabilities (not including notes payable and MRPS) from the Fund’s total assets and
dividing this by the amount of notes payable outstanding, and by multiplying the result by 1,000.

(b)

Calculated by subtracting the Fund’s total liabilities (not including MRPS) from the Fund’s total assets and dividing this by the
number of MRPS outstanding, and by multiplying the result by 25.

(c)

“Liquidating Preference per Preferred Share” means the amount to which a holder of preferred shares would be entitled upon
involuntary liquidation of the Fund in preference to common shareholders, expressed as a dollar amount per preferred share.

(d)

The MRPS are not listed on any exchange or automated quotation system. The MRPS are considered debt of the issuer; and the liquidation
preference approximates fair value.

USE OF PROCEEDS

Unless otherwise specified in this prospectus supplement, we currently intend to use the net proceeds from the sale of our common shares
in this offering primarily to invest in accordance with our investment objective and policies (as described under “Investment Objective and Principal Investment Strategies,” beginning on page [  ] of the accompanying
prospectus) within approximately three months of receipt of such proceeds. Such investments may be delayed if suitable investments are unavailable at the time or for other reasons. Pending such investment, we anticipate that we will invest the
proceeds in securities issued by the U.S. government or its agencies or instrumentalities or in high quality, short-term or long-term debt obligations. We may also use proceeds from the sale of our securities to (i) retire all or a portion of
any short-term debt we incur in pursuit of our investment objective and policies and (ii) for working capital purposes, including the payment of interest and operating expenses, although there is currently no intent to issue securities
primarily for this purpose. A delay in the anticipated use of proceeds could lower returns, reduce our distribution to common shareholders and reduce the amount of cash available to make dividend and interest payments on preferred shares and debt
securities, respectively.

SUP-6

PLAN OF DISTRIBUTION

[To be updated at the time of the offering]

LEGAL MATTERS

Ropes & Gray LLP,
which is serving as counsel to the Fund in connection with the offering, has opined on the legality of the issuance of the common shares offered hereby. Ropes & Gray LLP may rely on the opinion of
[                ] with respect to certain matters of Delaware law. [Certain legal matters will be passed upon for the underwriter(s) by [ ].

AVAILABLE INFORMATION

We are subject to the informational requirements of the Securities Exchange Act of 1934, as amended (the “Exchange Act”) and the 1940 Act and are required to file reports, including annual and
semi-annual reports, proxy statements and other information with the Commission. These documents are available on the Commission’s EDGAR system and can be inspected and copied for a fee at the Commission’s public reference room, 100 F
Street, N.E., Room 1580, Washington, D.C. 20549. Additional information about the operation of the public reference room facilities may be obtained by calling the Commission at (202) 551-5850.

This prospectus supplement and the accompanying prospectus do not contain all of the information in our registration statement, including
amendments, exhibits, and schedules. Statements in this prospectus supplement and the accompanying prospectus about the contents of any contract or other document are not necessarily complete and in each instance reference is made to the copy of the
contract or other document filed as an exhibit to the registration statement, each such statement being qualified in all respects by this reference.

Additional information about us can be found in our registration statement (including amendments, exhibits, and schedules) on Form N-2 filed with the Commission.
The Commission maintains a web site (http://www.sec.gov) that contains our registration statement, other documents incorporated by reference, and other information we have filed electronically with the Commission, including proxy statements and
reports filed under the Exchange Act.

SUP-7

[                ] Common Shares

Calamos Convertible Opportunities and Income Fund

PROSPECTUS SUPPLEMENT

[Date], 2019

[Until[Until[Date] (25 days after the date of this prospectus supplement), all dealers that buy, sell or trade the common
shares, whether or not participating in this offering, may be required to deliver a prospectus. This is in addition to the dealers’ obligation to deliver a prospectus when acting as underwriters.]

CHIPRO
[                ]

SUP-8

The information in this prospectus supplement is not complete and may be changed. We may not
sell these securities until the registration statement filed with the Securities and Exchange Commission is effective. This prospectus supplement is not an offer to sell these securities and is not soliciting an offer to buy these securities in any
jurisdiction where the offer or sale is not permitted.

SUBJECT TO COMPLETION, DATED [Date]

[LOGO]

FORM OF
PROSPECTUS SUPPLEMENT

(To prospectus dated
                ,         )

$

CALAMOS CONVERTIBLE OPPORTUNITIES AND INCOME FUND

Preferred Shares

Shares, Series

Liquidation Preference $ per share

Calamos Convertible Opportunities and Income Fund (the “Fund,” “we”, “us” or “our”) is a
diversified, closed-end management investment company. Our investment objective is to provide total return through a combination of capital appreciation and current income.

We are offering an additional series
(“Series                ”) of our series                 preferred shares
(referred to as “Preferred Shares” or “Series                 Preferred Shares”) in this prospectus supplement. This prospectus supplement is not
complete and should be read in conjunction with our prospectus dated , 20                (the “prospectus”), which accompanies this prospectus supplement. This
prospectus supplement does not include all information that you should consider before purchasing any Preferred Shares. You should read this prospectus supplement and our prospectus prior to purchasing any Preferred Shares.

The Series                 Preferred Shares offered in
this prospectus supplement, together with the previously issued and currently outstanding Preferred Shares, are collectively referred to as “Preferred Shares.” Individual series of Preferred Shares are referred to as a “series.”
Except as otherwise described in this prospectus supplement, the terms of this series and all other series are the same.

The
Preferred Shares have a liquidation preference of $                per share, plus any accumulated, unpaid dividends. The Preferred Shares also have priority over the
Fund’s common shares as to distribution of assets as described in this prospectus supplement.

Investing
in Preferred Shares involves certain risks, including the risks associated with the Fund’s use of leverage. See “Risk Factors” beginning on page [  ] of the accompanying prospectus and
beginning on page [    ] of this prospectus supplement.

Neither the Securities and
Exchange Commission nor any state securities commission has approved or disapproved of these securities or determined if this prospectus supplement is truthful or complete. Any representation to the contrary is a criminal offense.

Per Share
 
  
Total

Public offering price

$
         
 
  
$

Sales load

$
 
 
  
$

Proceeds to us (before expenses)(1)

$
 
 
  
$

(1)

Does not include offering expenses payable to us estimated to be $ .

The underwriters expect to deliver the Series
                Preferred Shares in book-entry form, through the facilities of The Depository Trust Company, to broker-dealers on or about ,
20            .

[UNDERWRITER(S)]

, 20

This prospectus supplement has been filed with the Securities and Exchange Commission (the
“Commission”). Additional copies of this prospectus supplement, the prospectus, the statement of additional information dated                , as supplemented
from time to time, or the Fund’s annual or semi-annual reports are available by calling (800) 582-6959 or by writing to the Fund, or you may obtain copies (and other information regarding
us) from the SEC’s web site (http://www.sec.gov). The Fund’s annual and semi-annual reports are also available on the Fund’s website at www.calamos.com, which provides a link to the Commission’s website where the Fund’s
statement of additional information may be obtained. You also may e-mail requests for these documents to the Commission at publicinfo@sec.gov or make a request in writing to the Commission’s
Public Reference Section, 100 F Street, N.E., Room 1580, Washington, D.C. 20549.

This prospectus supplement, which describes
the specific terms of this offering, also adds to and updates information contained in the accompanying prospectus and the documents incorporated by reference in the prospectus. The prospectus gives more general information, some of which may not
apply to this offering.

If the description of this offering varies between this prospectus supplement and the accompanying
prospectus, you should rely on the information contained in this prospectus supplement; provided that if any statement in one of these documents is inconsistent with a statement in another document having a later date, the statement in the document
having the later date modifies or supersedes the earlier statement.

The Preferred Shares do not represent a deposit or
obligation of, and are not guaranteed or endorsed by, any bank or other insured depository institution, and are not federally insured by the Federal Deposit Insurance Corporation, the Federal Reserve Board or any other government agency.

TABLE OF CONTENTS

Prospectus Supplement

You should rely only on the information contained in or incorporated by reference in this
prospectus supplement. Neither we nor the underwriters have authorized anyone to provide you with different or inconsistent information. If anyone provides you with different or inconsistent information, you should not rely on it. We are not, and
the underwriters are not, making an offer to sell these Series                 Preferred Shares in any jurisdiction where the offer or sale is not permitted. You should
assume that the information in this prospectus supplement is accurate only as of the date of this prospectus supplement, and that our business, financial condition and prospects may have changed since this date. We will amend or supplement this
prospectus supplement to reflect material changes to the information contained in this prospectus supplement to the extent required by applicable law.

i

CAUTIONARY NOTICE REGARDING FORWARD-LOOKING STATEMENTS

This prospectus supplement, the accompanying prospectus and the statement of additional information contain “forward-looking
statements.” Forward-looking statements can be identified by the words “may,” “will,” “intend,” “expect,” “estimate,” “continue,” “plan,” “anticipate,” and similar
terms and the negative of such terms. Such forward-looking statements may be contained in this prospectus supplement, as well as in the accompanying prospectus. By their nature, all forward-looking statements involve risks and uncertainties, and
actual results could differ materially from those contemplated by the forward-looking statements. Several factors that could materially affect our actual results are the performance of the portfolio of securities we hold, the conditions in the U.S.
and international financial, petroleum and other markets, the price at which our shares will trade in the public markets and other factors discussed in our periodic filings with the Commission.

Although we believe that the expectations expressed in our forward-looking statements are reasonable, actual results could differ
materially from those projected or assumed in our forward-looking statements. Our future financial condition and results of operations, as well as any forward-looking statements, are subject to change and are subject to inherent risks and
uncertainties, such as those disclosed in the “Risk Factors” section of the prospectus accompanying this prospectus supplement. All forward-looking statements contained or incorporated by reference in this prospectus supplement or the
accompanying prospectus are made as of the date of this prospectus supplement or the accompanying prospectus, as the case may be. Except for our ongoing obligations under the federal securities laws, we do not intend, and we undertake no obligation,
to update any forward-looking statement. The forward-looking statements contained in this prospectus supplement are excluded from the safe harbor protection provided by section 27A of the Securities Act of 1933, as amended.

Currently known risk factors that could cause actual results to differ materially from our expectations include, but are not limited to,
the factors described in the “Risk Factors” section of the prospectus accompanying this prospectus supplement. We urge you to review carefully that section for a more detailed discussion of the risks of an investment in the Preferred
Shares.

ii

PROSPECTUS SUPPLEMENT SUMMARY

This summary contains basic information about us but does not contain all of the information that is important to your investment decision.
You should read this summary together with the more detailed information contained elsewhere in this prospectus supplement and accompanying prospectus and in the statement of additional information, especially the information set forth under the
heading “Risk Factors” beginning on page [  ] of the accompanying prospectus and on page [    ] of this prospectus supplement.

The Fund

Calamos Convertible
Opportunities and Income Fund is a diversified, closed-end management investment company. Throughout the prospectus, we refer to Calamos Convertible Opportunities and Income Fund as the
“Fund” or as “we,” “us,” or “our.” The Fund’s common shares are traded on the NASDAQ Global Select Market (“NASDAQ”) under the symbol “CHI.” As
of [                 ], the Fund had [                ] common shares
outstanding and net assets of $[                ]. The Fund’s principal offices are located at 2020 Calamos Court, Naperville, Illinois 60563. We have a fiscal year
ending October 31st.

Our investment objective is to provide total return through a combination of capital appreciation and current
income. There can be no assurance that we will achieve our investment objective. See “The Fund” in the accompanying prospectus.

We commenced operations in June 2002 following our initial public offering.

Investment Adviser

Calamos Advisors LLC
(“Calamos”) is the Fund’s investment adviser. Calamos is responsible on a day-to-day basis for investment of the Fund’s portfolio in
accordance with its investment objective and policies. Calamos makes all investment decisions for the Fund and places purchase and sale orders for the Fund’s portfolio securities. As
of [                 ], Calamos managed approximately $xxx billion in assets of individuals and institutions. Calamos is a wholly owned subsidiary of Calamos
Investments LLC (“CILLC”) and an indirect subsidiary of Calamos Asset Management, Inc.

The Fund pays Calamos an annual fee,
payable monthly, for its investment management services equal to [                 ]% of the Fund’s average weekly managed assets. See “Management of the
Fund” in the accompanying prospectus.

The principal business address of the Adviser is 2020 Calamos Court, Naperville, Illinois,
60563.

The Offering

Preferred Shares offered by the Fund

We are offering Series             Preferred Shares, each at a purchase price of $         per share. The
Series             Preferred Shares are offered through            .

Use of Proceeds

The Fund estimates the net proceeds of the offering of Preferred Shares, after payment of sales load and offering expenses, will be approximately $        .

The Fund will invest the net proceeds of any sales of securities in accordance with our investment objective and policies. Such investments may be delayed if suitable investments are unavailable at the time or for other
reasons.

Pref-1

Pending such investment, we anticipate that we will invest the proceeds in securities issued by the U.S. government or its agencies or instrumentalities or in high quality, short-term or long-term debt obligations. We
may also use proceeds from the sale of our securities to (i) retire all or a portion of any short-term debt we incur in pursuit of our investment objective and policies, (ii) redeem any outstanding senior securities, and (iii) for
working capital purposes, including the payment of interest and operating expenses, although there is currently no intent to issue securities primarily for this purpose. A delay in the anticipated use of proceeds could lower returns, reduce our
distribution to common shareholders and reduce the amount of cash available to make dividend and interest payments on preferred shares and debt securities, respectively. See “Investment Objective and Principal Investment Strategies” in the
accompanying prospectus.

Risk Factors

See “Risk Factors” and other information included in the accompanying prospectus and in this prospectus supplement for a discussion of factors you should carefully consider before deciding to invest in the Preferred Shares.

Pref-2

USE OF PROCEEDS

The Fund estimates the net proceeds of the offering of Preferred Shares, after payment of sales load and offering expenses, will be
approximately $            . Subject to the remainder of this section, we will invest the net proceeds of any sales of securities in accordance with our investment objective and policies.
Such investments may be delayed if suitable investments are unavailable at the time or for other reasons. Pending such investment, we anticipate that we will invest the proceeds in securities issued by the U.S. government or its agencies or
instrumentalities or in high quality, short-term or long-term debt obligations. We may also use proceeds from the sale of our securities to (i) retire all or a portion of any short-term debt we incur in pursuit of our investment objective and
policies, (ii) redeem any outstanding senior securities, and (iii) for working capital purposes, including the payment of interest and operating expenses, although there is currently no intent to issue securities primarily for this
purpose. A delay in the anticipated use of proceeds could lower returns, reduce our distribution to common shareholders and reduce the amount of cash available to make dividend and interest payments on preferred shares and debt securities,
respectively. See “Investment Objective and Principal Investment Strategies” in the accompanying prospectus.

CAPITALIZATION

The following table sets forth the capitalization of the Fund as
of             , 20            , and as adjusted, to give effect to the issuance of all the Preferred Shares offered hereby
(including estimated offering expenses and sales load of $        ). The sales load and offering expenses of the Preferred Shares will be effectively borne by common shareholders.

Actual
 
  
As AdjustedPreferred Shares

Loan

Shareholders Equity

Preferred Shares, no par value per share, $25,000 stated value per share, at liquidation value;
unlimited shares authorized (no shares issued; and shares issued, respectively)*

Common shares, no par value per share, unlimited shares authorized,
        shares outstanding*

Undistributed net investment income

Accumulated net realized gain (loss) on investments

Net Unrealized appreciation (depreciation) on investments

Net Assets

*

None of these outstanding shares are held by or for the account of the Fund

ASSET COVERAGE REQUIREMENTS

The Fund may be subject to certain restrictions on investments imposed by guidelines of one or more rating agencies that may issue ratings for
the preferred shares or debt instruments issued by the Fund. These guidelines may impose asset coverage or portfolio composition requirements that are more stringent than those imposed by the 1940 Act. Certain types of borrowings may result in the
Fund being subject to covenants in credit agreements, including those relating to asset coverage, borrowing base and portfolio composition requirements and additional covenants. The Fund may also be required to pledge its assets to the lenders in
connection with certain types of borrowing. Calamos does not anticipate that these covenants or restrictions will adversely affect its ability to manage the Fund’s portfolio in accordance with the Fund’s investment objective and policies.
Due to these covenants or restrictions, the Fund may be forced to liquidate investments at times and at prices that are not favorable to the Fund, or the Fund may be forced to forgo investments that Calamos otherwise views as favorable.

Pref-3

DESCRIPTION OF PREFERRED SHARES

The following is a brief description of the terms of the Preferred Shares. For the complete terms of the Preferred Shares, please refer to the
detailed description of the Preferred Shares in the Statement of Preferences of Preferred Shares (the “Statement”) attached as Appendix          to the statement of additional information. Where
appropriate, terms used in “Description of Preferred Shares” below will have the same meanings as those terms in the Statement.

General

The Fund’s Agreement and Declaration of Trust authorizes the issuance of preferred shares, no par value per share, in one or more
classes or series with rights as determined by the Board of Trustees without the approval of common shareholders. The Statement currently authorizes the issuance of          Preferred Shares, Series
        . All Preferred Shares will have a liquidation preference of $         per share, plus an amount equal to accumulated but unpaid dividends (whether or not earned
or declared).

The Preferred Shares of each series will rank on parity with any other series of Preferred Shares and any other series of
preferred shares of the Fund as to the payment of dividends and the distribution of assets upon liquidation. Each Preferred Share carries one vote on matters on which Preferred Shares can be voted. The Preferred Shares, when issued by the Fund and
paid for pursuant to the terms of this prospectus supplement and the accompanying prospectus, will be fully paid and non-assessable and will have no preemptive, exchange or conversion rights. Any
Preferred Shares repurchased or redeemed by the Fund will be classified as authorized and unissued Preferred Shares. The Board of Trustees may by resolution classify or reclassify any authorized and unissued Preferred Shares from time to time by
setting or changing the preferences, rights, voting powers, restrictions, limitations as to dividends, qualifications or terms or conditions of redemption of such shares. The Preferred Shares will not be subject to any sinking fund, but will be
subject to mandatory redemption under certain circumstances described below.

Dividends and Dividend Periods

The following is a general description of dividends and dividend periods for the Preferred Shares.

Dividend Periods. The dividend period for the Preferred Shares is          and the
dividend rate is         % per annum.

Dividend Payment Dates. Dividends on the
Preferred Shares will be payable, when, as and if declared by the Board of Trustees, out of legally available funds in accordance with the Agreement and Declaration of Trust, the Statement and applicable law.

Dividends on Preferred Shares will accumulate from the date of their original issue, which is
        , 20        .

Restrictions on Dividend,
Redemption and Other Payments. Under the 1940 Act, the Fund may not (i) declare any dividend with respect to the Preferred Shares if, at the time of such declaration (and after giving effect thereto), asset coverage with respect to the
Fund’s senior securities representing indebtedness (as defined in the 1940 Act) would be less than 200% (or such other percentage as may in the future be specified in or under the 1940 Act as the minimum asset coverage for senior securities
representing indebtedness of a closed-end investment company as a condition of declaring dividends on its preferred shares) or (ii) declare any other distribution on the Preferred Shares or
purchase or redeem Preferred Shares if at the time of the declaration (and after giving effect thereto), asset coverage with respect to the Fund’s senior securities representing indebtedness would be less than 300% (or such other percentage as
may in the future be specified in or under the 1940 Act as the minimum asset coverage for senior securities representing indebtedness of a closed-end investment company as a condition of declaring
distributions, purchases or redemptions of its shares of beneficial interest). “Senior securities representing indebtedness” generally means any bond, debenture, note or similar obligation or instrument constituting a security (other than
shares of beneficial interest) and evidencing

Pref-4

indebtedness and could include the Fund’s obligations under any Borrowings. The term “senior security” also does not include any promissory note or other evidence of indebtedness
in any case where such a loan is for temporary purposes only and in an amount not exceeding 5% of the value of the total assets of the Fund at the time when the loan is made. A loan is presumed under the 1940 Act to be for temporary purposes if it
is repaid within 60 days and is not extended or renewed; otherwise it is presumed not to be for temporary purposes. For purposes of determining whether the 200% and 300% asset coverage requirements described above apply in connection with dividends
or distributions on or purchases or redemptions of Preferred Shares, such asset coverages may be calculated on the basis of values calculated as of a time within 48 hours (not including Sundays or holidays) next preceding the time of the applicable
determination.

In addition, a declaration of a dividend or other distribution on, or purchase or redemption of, Preferred Shares may be
prohibited (i) at any time when an event of default under any borrowings has occurred and is continuing; or (ii) if, after giving effect to such declaration, the Fund would not have eligible portfolio holdings with an aggregated discounted
value at least equal to any asset coverage requirements associated with such borrowings; or (iii) the Fund has not redeemed the full amount of borrowings, if any, required to be redeemed by any provision for mandatory redemption.

Voting Rights

The Fund’s common
shares and Preferred Shares have equal voting rights of one vote per share and vote together as a single class. In elections of trustees, the holders of Preferred Shares, as a separate class, vote to elect two trustees. The Board of Trustees will
determine to which class or classes the trustees elected by the holders of Preferred Shares will be assigned. The holders of the Preferred Shares shall only be entitled to elect the trustees so designated when their term shall have expired. Such
trustees appointed by the holders of Preferred Shares will be allocated as evenly as possible among the classes of trustees.

So long as
any of the Preferred Shares are outstanding, the Fund will not, without the affirmative vote of the holders of a majority of the outstanding Preferred Shares, take certain other actions as described in the Indenture.

The common shares and the Preferred Shares also will vote separately to the extent otherwise required under Delaware law or the 1940 Act as in
effect from time to time. The class votes of holders of Preferred Shares described above will in each case be in addition to any separate vote of the requisite percentage of common shares and Preferred Shares, voting together as a single class,
necessary to authorize the action in question.

For the purpose of any right of the holders of Preferred Shares to vote on any matter,
whether the right is created by the Agreement and Declaration of Trust, by statute or otherwise, a holder of a Preferred Share is not entitled to vote and the Preferred Shares will not be deemed to be outstanding for the purpose of voting or
determining the number of Preferred Shares required to constitute a quorum, if prior to or concurrently with a determination of the Preferred Shares entitled to vote or of Preferred Shares deemed outstanding for quorum purposes, as the case may be,
a notice of redemption was given in respect of those Preferred Shares and sufficient deposit securities for the redemption of those Preferred Shares were deposited.

Redemption

Mandatory
Redemption. Under certain circumstances, the Preferred Shares will be subject to mandatory redemption by the Fund out of funds legally available therefor in accordance with the Statement and applicable law.

Optional Redemption. Under certain circumstances, to the extent permitted under the 1940 Act and Delaware law, the Fund may have
the option to redeem, in whole or in part, Preferred Shares.

Liquidation

Subject to the rights of holders of any series or class or classes of shares ranking on a parity with Preferred Shares with respect to the
distribution of assets upon liquidation of the Fund, upon a liquidation, dissolution or

Pref-5

winding up of the affairs of the Fund, whether voluntary or involuntary, the holders of Preferred Shares then outstanding will be entitled to receive and to be paid out of the assets of the Fund
available for distribution to its shareholders, after claims of creditors but before any payment or distribution is made on the common shares or any other shares of beneficial interest of the Fund ranking junior to the Preferred Shares, an amount
equal to the liquidation preference with respect to such shares ($            per share), plus an amount equal to all unpaid dividends thereon. After the payment to the holders of Preferred
Shares of the full preferential amounts provided for as described herein, the holders of Preferred Shares as such will have no right or claim to any of the remaining assets of the Fund.

If, upon any such liquidation, dissolution or winding up of the affairs of the Fund, whether voluntary or involuntary, the assets of the Fund
available for distribution among the holders of all outstanding Preferred Shares, including each series, shall be insufficient to permit the payment in full to such holders of the amounts to which they are entitled, then such available assets shall
be distributed among the holders of all outstanding Preferred Shares, including each series, ratably in any such distribution of assets according to the respective amounts which would be payable on all such shares if all amounts thereon were paid in
full. Unless and until payment in full has been made to the holders of all outstanding Preferred Shares, including each series, of the liquidation distributions to which they are entitled, no dividends or distributions will be made to holders of
common shares or any shares of beneficial interest of the Fund ranking junior to the Preferred Shares as to liquidation.

UNDERWRITING

[To be provided at the time of an offering.]

WHERE YOU CAN FIND MORE INFORMATION

The Fund is subject to the informational requirements of the Securities Exchange Act of 1934 and the 1940 Act and is required to file reports,
proxy statements and other information with the Securities and Exchange Commission. These documents can be inspected and copied for a fee at the Commission’s public reference room, 100 F Street, N.E., Washington, D.C. 20549. Reports, proxy
statements, and other information about the Fund can be inspected at the offices of the NASDAQ OMX Group Inc., 165 Broadway #4900, New York, NY 10006.

This prospectus supplement and the accompanying prospectus do not contain all of the information in the Fund’s registration statement,
including amendments, exhibits, and schedules. Statements in this prospectus supplement and the accompanying prospectus about the contents of any contract or other document are not necessarily complete and in each instance reference is made to the
copy of the contract or other document filed as an exhibit to the registration statement, each such statement being qualified in all respects by this reference.

Additional information about the Fund and Preferred Shares can be found in the Fund’s registration statement (including amendments,
exhibits, and schedules) on Form N-2 filed with the Commission. The Commission maintains a web site (http://www.sec.gov) that contains the Fund’s registration statement, other documents
incorporated by reference, and other information the Fund has filed electronically with the Commission, including proxy statements and reports filed under the Securities Exchange Act of 1934.

LEGAL MATTERS

,
(“                ”), is counsel to the Fund.                 will pass on the
legality of the securities to be offered hereby. If certain legal matters in connection with an offering of securities are passed upon by counsel for the underwriters of such offering, such matters will be passed upon by counsel to be identified in
a prospectus supplement.                 and counsel to the underwriters may rely on the opinion of
                
for certain matters of Delaware law.

[UNAUDITED] FINANCIAL STATEMENTS AS
OF                 , 20

Pref-6

$

Calamos Convertible Opportunities and Income Fund

Preferred Shares

Shares, Series

PROSPECTUS SUPPLEMENT

,
20

[Underwriters]

Pref-7

The information in this prospectus supplement is not complete and may be changed. We may not
sell these securities until the registration statement filed with the Securities and Exchange Commission is effective. This prospectus supplement is not an offer to sell these securities and is not soliciting an offer to buy these securities in any
jurisdiction where the offer or sale is not permitted.

SUBJECT TO COMPLETION, DATED [Date]

FORM OF PROSPECTUS SUPPLEMENT

(To prospectus dated                 ,         )

$

CALAMOS CONVERTIBLE OPPORTUNITIES AND INCOME FUND

Notes (“Calamos Notes”)

$                Series     , Due
                , 20

$                Denominations

Calamos Convertible Opportunities and Income Fund (the “Fund,” “we,” “us” or “our”) is a diversified, closed-end management investment company. Our investment objective is to provide total return through a combination of capital appreciation and current income.

We are offering an aggregate principal amount of
$                Series                  Calamos Notes in this prospectus supplement.
This prospectus supplement is not complete and should be read in conjunction with our prospectus dated , 20     (the “prospectus”), which accompanies this prospectus supplement. This prospectus supplement does not
include all information that you should consider before purchasing any Calamos Notes. You should read this prospectus supplement and our prospectus prior to purchasing any Calamos Notes.

The notes offered in this prospectus supplement are referred to as “Calamos Notes.” Individual series of Calamos Notes are
referred to as a “series.” Except as otherwise described in this prospectus supplement, the terms of this series and all other series are the same.

Investing in Calamos Notes involves certain risks, including the risks associated with the Fund’s use of leverage. See “Risk Factors” beginning on page
[  ] of the accompanying prospectus and on page [    ] of this prospectus supplement.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or
determined if this prospectus supplement or accompanying prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

Per Share
 
  
Total

Public offering price

$
         
 
  
$

Sales load

$
 
 
  
$

Proceeds to us (before expenses)(1)

$
 
 
  
$

(1)

Does not include offering expenses payable to us estimated to be $         .

The underwriters expect to deliver the Calamos Notes in book-entry form, through the facilities of The
Depository Trust Company, to broker-dealers on or about                 , 20    .

[UNDERWRITER(S)]

, 20

This prospectus supplement has been filed with the Securities and Exchange Commission (the
“Commission”). Additional copies of this prospectus supplement, the prospectus, the statement of additional information dated                 , as supplemented
from time to time, or the Fund’s annual or semi-annual reports are available by calling (800) 582-6959 or by writing to the Fund, or you may obtain copies (and other information regarding
us) from the Commission’s web site (http://www.sec.gov). The Fund’s annual and semi-annual reports are also available on the Fund’s website at www.calamos.com, which provides a link to the Commission’s website where the
Fund’s statement of additional information may be obtained. You also may e-mail requests for these documents to the Commission at publicinfo@sec.gov or make a request in writing to the
SEC’s Public Reference Section, 100 F Street, N.E., Room 1580, Washington, D.C. 20549.

This prospectus supplement, which
describes the specific terms of this offering, also adds to and updates information contained in the accompanying prospectus and the documents incorporated by reference in the prospectus. The prospectus gives more general information, some of which
may not apply to this offering.

If the description of this offering varies between this prospectus supplement and the
accompanying prospectus, you should rely on the information contained in this prospectus supplement; provided that if any statement in one of these documents is inconsistent with a statement in another document having a later date, the statement in
the document having the later date modifies or supersedes the earlier statement.

The Calamos Notes do not represent a deposit
or obligation of, and are not guaranteed or endorsed by, any bank or other insured depository institution, and are not federally insured by the Federal Deposit Insurance Corporation, the Federal Reserve Board or any other government agency.

TABLE OF CONTENTS

Prospectus Supplement

You should rely on the information contained in or incorporated by reference in this prospectus
supplement in making an investment decision. Neither we nor the underwriters have authorized anyone to provide you with different or inconsistent information. If anyone provides you with different or inconsistent information, you should not rely on
it. We are not, and the underwriters are not, making an offer to sell these notes in any jurisdiction where the offer or sale is not permitted. You should assume that the information in this prospectus supplement is accurate only as of the date of
this prospectus supplement, and that our business, financial condition and prospects may have changed since this date. We will amend or supplement this prospectus supplement to reflect material changes to the information contained in this prospectus
supplement to the extent required by applicable law.

i

CAUTIONARY NOTICE REGARDING FORWARD-LOOKING STATEMENTS

This prospectus supplement, the accompanying prospectus and the statement of additional information contain “forward-looking
statements.” Forward-looking statements can be identified by the words “may,” “will,” “intend,” “expect,” “estimate,” “continue,” “plan,” “anticipate,” and similar
terms and the negative of such terms. Such forward-looking statements may be contained in this prospectus supplement, as well as in the accompanying prospectus. By their nature, all forward-looking statements involve risks and uncertainties, and
actual results could differ materially from those contemplated by the forward-looking statements. Several factors that could materially affect our actual results are the performance of the portfolio of securities we hold, the conditions in the U.S.
and international financial, petroleum and other markets, the price at which our shares will trade in the public markets and other factors discussed in our periodic filings with the Commission.

Although we believe that the expectations expressed in our forward-looking statements are reasonable, actual results could differ
materially from those projected or assumed in our forward-looking statements. Our future financial condition and results of operations, as well as any forward-looking statements, are subject to change and are subject to inherent risks and
uncertainties, such as those disclosed in the “Risk Factors” section of the prospectus accompanying this prospectus supplement. All forward-looking statements contained or incorporated by reference in this prospectus supplement or the
accompanying prospectus are made as of the date of this prospectus supplement or the accompanying prospectus, as the case may be. Except for our ongoing obligations under the federal securities laws, we do not intend, and we undertake no obligation,
to update any forward-looking statement. The forward-looking statements contained in this prospectus supplement are excluded from the safe harbor protection provided by section 27A of the Securities Act of 1933, as amended.

Currently known risk factors that could cause actual results to differ materially from our expectations include, but are not limited to,
the factors described in the “Risk Factors” section of the prospectus accompanying this prospectus supplement. We urge you to review carefully this section for a more detailed discussion of the risks of an investment in the Calamos Notes.

ii

PROSPECTUS SUPPLEMENT SUMMARY

This summary contains basic information about us but does not contain all of the information that is important to your investment
decision. You should read this summary together with the more detailed information contained elsewhere in this prospectus supplement and accompanying prospectus and in the statement of additional information, especially the information set forth
under the heading “Risk Factors” beginning on page [  ] of the accompanying prospectus and on page [    ] of this prospectus summary.

The Fund

The Fund is a
diversified, closed-end management investment company. Throughout the prospectus, we refer to Calamos Convertible Opportunities and Income Fund as the “Fund” or as “we,”
“us,” or “our.” See “The Fund.” The Fund’s common shares are traded on the NASDAQ Global Select Market (“NASDAQ”) under the symbol “CHI.” As of
                , the Fund had                 common shares outstanding and net assets
of $                . The Fund’s principal offices are located at 2020 Calamos Court, Naperville, Illinois 60563. We have a fiscal year ending October 31st.

Our investment objective is to provide total return through a combination of capital appreciation and current income. There
can be no assurance that we will achieve our investment objective. See “The Fund” in the accompanying prospectus.

We
commenced operations in June 2002 following our initial public offering.

Investment Adviser

Calamos Advisors LLC (“Calamos”) is the Fund’s investment adviser. Calamos is responsible on
a day-to-day basis for investment of the Fund’s portfolio in accordance with its investment objective and policies. Calamos makes all investment decisions
for the Fund and places purchase and sale orders for the Fund’s portfolio securities. As of                , Calamos managed approximately
$                billion in assets of individuals and institutions. Calamos is a wholly owned subsidiary of Calamos Investments LLC (“CILLC”) and an indirect
subsidiary of Calamos Asset Management, Inc.

The Fund pays Calamos an annual fee, payable monthly, for its investment
management services equal to    % of the Fund’s average weekly managed assets. See “Management of the Fund” in the accompanying prospectus.

The principal business address of the Adviser is 2020 Calamos Court, Naperville, Illinois 60563.

The Offering

Calamos Notes offered by the Fund

$                 aggregate principal amount of Series
                 Calamos Notes. Series                 Calamos Notes will be sold in
denominations of $                and any integral multiple thereof. The Series
                Calamos Notes are being offered by                 and
                , as underwriters. See “Underwriting.”

Use of proceeds

The Fund estimates the net proceeds of the offering of Series                 Calamos
                Notes, after payment of sales load and offering expenses, will be approximately
$                .

The Fund will invest the net proceeds of any sales of securities in accordance with our investment objective and policies. Such investments may be delayed if
suitable investments are unavailable at the time or for other reasons. Pending such investment, we anticipate

Debt-1

that we will invest the proceeds in securities issued by the U.S. government or its agencies or instrumentalities or in high quality, short-term or long-term debt obligations. We may also use
proceeds from the sale of our securities to (i) retire all or a portion of any short-term debt we incur in pursuit of our investment objective and policies, (ii) redeem any outstanding senior securities, and (iii) for working capital
purposes, including the payment of interest and operating expenses, although there is currently no intent to issue securities primarily for this purpose. A delay in the anticipated use of proceeds could lower returns, reduce our distribution to
common shareholders and reduce the amount of cash available to make dividend and interest payments on preferred shares and debt securities, respectively. See “Investment Objective and Principal Investment Strategies” in the accompanying
prospectus.

Risk factors

See “Risk Factors” and other information included in the accompanying prospectus and in this prospectus supplement, for a discussion of factors you should carefully consider before
deciding to invest in the Calamos Notes.

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USE OF PROCEEDS

The Fund estimates the net proceeds of the offering of Calamos Notes, after payment of sales load and offering expenses, will be
approximately $                . The Fund will invest the net proceeds of any sales of securities in accordance with our investment objective and policies. Such
investments may be delayed if suitable investments are unavailable at the time or for other reasons. Pending such investment, we anticipate that we will invest the proceeds in securities issued by the U.S. government or its agencies or
instrumentalities or in high quality, short-term or long-term debt obligations. We may also use proceeds from the sale of our securities to (i) retire all or a portion of any short-term debt we incur in pursuit of our investment objective and
policies, (ii) redeem any outstanding senior securities, and (iii) for working capital purposes, including the payment of interest and operating expenses, although there is currently no intent to issue securities primarily for this
purpose. A delay in the anticipated use of proceeds could lower returns, reduce our distribution to common shareholders and reduce the amount of cash available to make dividend and interest payments on preferred shares and debt securities,
respectively. See “Investment Objective and Principal Investment Strategies” in the accompanying prospectus.

CAPITALIZATION

The following table sets forth the capitalization of the Fund as of
                , 20    , and as adjusted, to give effect to the issuance of all the Calamos Notes offered hereby (including estimated offering
expenses and sales load of $                ). The sales load and offering expenses of the Calamos Notes will be effectively borne by common shareholders.

Actual
 
  
As AdjustedCalamos Notes

Long-Term Debt

Calamos Notes, denominations of $             or any multiple
thereof

Loan

Shareholders Equity

Preferred Shares, no par value per share, $25,000 stated value per share, at liquidation value; unlimited shares authorized (no
shares issued; and             shares issued, respectively)*

Common shares, no par value per share, unlimited shares authorized,
            shares outstanding*

Undistributed net investment income

Accumulated net realized gain (loss) on investments

Net Unrealized appreciation (depreciation) on investments

Net Assets

*

None of these outstanding shares are held by or for the account of the Fund

ASSET COVERAGE REQUIREMENTS

The Fund may be subject to certain restrictions on investments imposed by guidelines of one or more rating agencies that may issue ratings
for the preferred shares or debt instruments issued by the Fund. These guidelines may impose asset coverage or portfolio composition requirements that are more stringent than those imposed by the 1940 Act. Certain types of borrowings may result in
the Fund being subject to covenants in credit agreements, including those relating to asset coverage, borrowing base and portfolio composition requirements and additional covenants. The Fund may also be required to pledge its assets to the lenders
in connection with certain types of borrowing. Calamos does not anticipate that these covenants or restrictions will adversely affect its ability to manage the Fund’s portfolio in accordance with the Fund’s investment objective and
policies. Due to these covenants or restrictions, the Fund may be forced to liquidate investments at times and at prices that are not favorable to the Fund, or the Fund may be forced to forgo investments that Calamos otherwise views as favorable.

Debt-3

DESCRIPTION OF CALAMOS NOTES

Calamos Notes of each series will rank on a parity with any other series of Calamos Notes as to the payment of interest and distribution
of assets upon liquidation. All Calamos Notes rank senior to our common and preferred shares as to the payment of interest and distribution of assets upon liquidation. Under the 1940 Act, we may only issue one class of senior securities representing
indebtedness other than promissory notes or other evidences of indebtedness not intended to be publicly distributed.

The
Series                 Calamos Notes will be issued pursuant to the indenture between the Fund and the trustee dated as
of                , 20    , as it may be supplemented from time to time (referred to herein collectively as the “Indenture”). The following
summary sets forth certain general terms and provisions of the Indenture under which the Calamos Notes may be issued. The summary is not complete and is qualified in its entirety by the provisions of the Indenture, a more detailed summary of which
is contained in Appendix     to the statement of additional information, which is on file with the Commission. Whenever defined terms are used, but not defined in this prospectus supplement, the terms have the meaning given to
them in Appendix                 to the statement of additional information.

General

The Board of Trustees has authorized us to issue the Series
     Calamos Notes representing indebtedness pursuant to the terms of the Indenture. Currently, the Indenture provides for the issuance of up
to $                 aggregate principal amount of Series      Calamos Notes. The principal amount of the Series     
Calamos Notes is due and payable on                 , 20    . The Series      Calamos Notes, when issued and sold pursuant to the
terms of the Indenture, will be issued in fully registered form without coupons and in denominations of $                and any integral multiple thereof, unless
otherwise provided in the Indenture. The Series      Calamos Notes will be unsecured obligations of ours and, upon our liquidation, dissolution or winding up, will rank: (1) senior to our outstanding common shares and any
outstanding preferred shares; (2) on a parity with any of our unsecured creditors, including any other series of Calamos Notes; and (3) junior to any of our secured creditors. The Calamos Notes may be subject to optional and mandatory
redemption and acceleration of maturity, as described in the Indenture and the accompanying prospectus under “Description of Securities — Debt Securities — Events of Default and Acceleration of Maturity of Debt Securities;
Remedies.”

The Calamos Notes have no voting rights, except to the extent required by law or as otherwise provided in the
Indenture relating to the acceleration of maturity upon the occurrence and continuance of an event of default.

Unsecured Investment

The Calamos Notes represent an unsecured obligation of ours to pay interest and principal, when due. We cannot assure you
that we will have sufficient funds or that we will be able to arrange for additional financing to pay interest on the Calamos Notes when due or to repay the Calamos Notes at the Stated Maturity. Our failure to pay interest on the Calamos Notes when
due or to repay the Calamos Notes upon the Stated Maturity would, subject to the cure provisions under the Indenture, constitute an event of default under the Indenture and could cause a default under other agreements that we may enter into from
time to time. There is no sinking fund with respect to the Calamos Notes, and at the Stated Maturity, the entire outstanding principal amount of the Calamos Notes will become due and payable.

Securities Depository

The nominee of the Securities Depository is expected
to be the sole record holder of the Calamos Notes. Accordingly, each purchaser of Calamos Notes must rely on (1) the procedures of the Securities Depository and, if such purchaser is not a member of the Securities Depository, such
purchaser’s Agent Member, to receive interest payments and notices and (2) the records of the Securities Depository and, if such purchaser is not a member of the Securities Depository, such purchaser’s Agent Member, to evidence its
ownership of the Calamos Notes.

Debt-4

Purchasers of Calamos Notes will not receive certificates representing their ownership
interest in such securities. DTC initially will act as Securities Depository for the Agent Members with respect to the Calamos Notes.

Interest and Rate Periods

Calamos Notes will bear interest from the Original Issue Date at the Applicable Rate and shall be payable on each Interest Payment Date
thereafter. Interest will be paid through the Securities Depository on each Interest Payment Date. Interest on the Calamos Notes shall be payable when due as described in this prospectus supplement. If we do not pay interest when due, it will
trigger an event of default under the Indenture (subject to the cure provisions), and we will be restricted from declaring dividends and making other distributions with respect to our common shares and preferred shares.

Redemption

Optional
Redemption. To the extent permitted under the 1940 Act, Delaware law and the Indenture, we may, at our option, redeem Calamos Notes, in whole or in part, out of funds legally available therefor, in accordance with the terms set forth in this
prospectus supplement and the Indenture.

Mandatory Redemption. Under certain circumstances described in this
prospectus supplement and the Indenture, the Calamos Notes will be subject to mandatory redemption out of funds legally available therefor. The redemption price per Calamos Note in the event of any mandatory redemption will be not less than the
principal amount, plus an amount equal to accrued but unpaid interest to the date fixed for redemption.

Redemption
Procedure. Pursuant to Rule 23c-2 under the 1940 Act, we will file a notice of our intention to redeem with the Commission so as to provide at least the minimum notice required by such Rule or
any successor provision (notice currently must be filed with the Commission generally at least 30 days prior to the redemption date).

If less than all of the outstanding Calamos Notes of a series are redeemed on any date, the amount per holder to be redeemed on such date will be selected by us on a pro rata basis in proportion to the
principal amount of Calamos Notes held by such holder, by lot or by such other method as is determined by us to be fair and equitable.

If Notice of Redemption has been given, then upon the deposit of funds with the Paying Agent sufficient to effect such redemption, interest on such Calamos Notes will cease to accrue and such Calamos
Notes will no longer be deemed to be outstanding for any purpose and all rights of the holders of the Calamos Notes so called for redemption will cease and terminate, except the right of the holders of such Calamos Notes to receive the redemption
price, but without any interest or additional amount.

So long as any Calamos Notes are held of record by the nominee of the
Securities Depository, the redemption price for such Calamos Notes will be paid on the redemption date to the nominee of the Securities Depository. The Securities Depository’s normal procedures provide for it to distribute the amount of the
redemption price to Agent Members who, in turn, are expected to distribute such funds to the persons for whom they are acting as agent.

Notwithstanding the provisions for redemption described above, no Calamos Notes may be redeemed unless all interest in arrears on the outstanding Calamos Notes, and any of our indebtedness ranking on a
parity with the Calamos Notes, have been or are being contemporaneously paid or set aside for payment, except in connection with our liquidation, in which case all Calamos Notes and all indebtedness ranking on a parity with the Calamos Notes must
receive proportionate amounts. At any time we may purchase or acquire all the outstanding Calamos Notes pursuant to the successful completion of an otherwise lawful purchase or exchange offer made on the same terms to, and accepted by, holders of
all outstanding Calamos Notes.

Debt-5

Payment of Proceeds Upon Dissolution, Etc.

In the event of (a) any insolvency or bankruptcy case or proceeding, or any receivership, liquidation, reorganization or other
similar case or proceeding in connection therewith, relative to us or to our creditors, as such, or to our assets, or (b) our liquidation, dissolution or other winding up, whether voluntary or involuntary and whether or not involving insolvency
or bankruptcy, or (c) our assignment for the benefit of creditors or any other marshalling of assets and liabilities, then (after any payments with respect to our secured creditor outstanding at such time) and in any such event the holders of
Calamos Notes shall be entitled to receive payment in full of all amounts due or to become due on or in respect of all Calamos Notes (including any interest accruing thereon after the commencement of any such case or proceeding), or provision shall
be made for such payment in cash or cash equivalents or otherwise in a manner satisfactory to the holders of the Calamos Notes, before the holders of any of our common or preferred shares are entitled to receive any payment on account of any
redemption proceeds, liquidation preference or dividends from such shares, and to that end the holders of Calamos Notes shall be entitled to receive, for application to the payment thereof, any payment or distribution of any kind or character,
whether in cash, property or securities, including any such payment or distribution which may be payable or deliverable by reason of the payment of any of our other indebtedness being subordinated to the payment of the Calamos Notes, which may be
payable or deliverable in respect of the Calamos Notes in any such case, proceeding, dissolution, liquidation or other winding up event.

Unsecured creditors of ours may include, without limitation, service providers including Calamos, the Fund’s custodian, the Fund’s administrator, broker-dealers and the trustee, pursuant to the
terms of various contracts with us. Secured creditors of ours may include without limitation State Street Bank and Trust Company and other lenders to the Fund, parties entering into any interest rate swap, floor or cap transactions, or other similar
transactions with us that create liens, pledges, charges, security interests, security agreements or other encumbrances on our assets.

UNDERWRITING

[To be provided at the time of an offering.]

WHERE YOU CAN FIND MORE INFORMATION

We are subject to the informational requirements of the Securities Exchange Act of 1934, as amended (the “1934 Act”) and the
1940 Act and are required to file reports, including annual and semi-annual reports, proxy statements and other information with the Commission. We voluntarily file quarterly shareholder reports. Our most recent shareholder report filed with the
Commission is for the period ended , 20    . These documents are available on the Commission’s EDGAR system and can be inspected and copied for a fee at the Commission’s public reference room, 100 F Street, N.E., Room
1580, Washington, D.C. 20549. Additional information about the operation of the public reference room facilities may be obtained by calling the Commission at (202) 551-5850.

This prospectus supplement and the accompanying prospectus do not contain all of the information in our registration statement, including
amendments, exhibits, and schedules. Statements in this prospectus supplement and the accompanying prospectus about the contents of any contract or other document are not necessarily complete and in each instance reference is made to the copy of the
contract or other document filed as an exhibit to the registration statement, each such statement being qualified in all respects by this reference.

Additional information about us can be found in our Registration Statement (including amendments, exhibits, and schedules) on Form N-2 filed with the
Commission. The Commission maintains a web site (http://www.sec.gov) that contains our Registration Statement, other documents incorporated by reference, and other information we have filed electronically with the Commission, including proxy
statements and reports filed under the Exchange Act.

Debt-6

LEGAL MATTERS

,
(“                ”), is counsel to the Fund.                 will opine on the
legality of the securities to be offered hereby. If certain legal matters in connection with an offering of securities are passed upon by counsel for the underwriters of such offering, such matters will be passed upon by counsel to be identified in
a prospectus supplement.                 and counsel to the underwriters may rely on the opinion of
                 for certain matters of Delaware law.

[UNAUDITED] FINANCIAL STATEMENTS AS OF                 ,
20

Debt-7

$

Calamos Convertible Opportunities and Income Fund

Notes (“Calamos Notes”)

$             Series     
Due                , 20

PROSPECTUS SUPPLEMENT

,
20

[Underwriter]

Debt-8

CALAMOS CONVERTIBLE OPPORTUNITIES AND INCOME FUND

STATEMENT OF ADDITIONAL INFORMATION

Calamos Convertible Opportunities and Income Fund (the “Fund”) is a diversified, closed-end management investment company. This
Statement of Additional Information relates to the offering, on an immediate, continuous or delayed basis, of up to $100,000,000 aggregate initial offering price of common shares, preferred shares or debt securities in one or more offerings. This
Statement of Additional Information does not constitute a prospectus, but should be read in conjunction with the prospectus relating thereto dated the date hereof and any related prospectus supplement. This Statement of Additional Information does
not include all information that a prospective investor should consider before purchasing any of the Fund’s securities, and investors should obtain and read the prospectus and any related prospectus supplement prior to purchasing such
securities. A copy of the prospectus and any related prospectus supplement may be obtained without charge by calling 1-800-582-6959. You may also obtain a copy of the prospectus and any related prospectus supplement on the Securities and Exchange
Commission’s website (http://www.sec.gov). Capitalized terms used but not defined in this Statement of Additional Information have the same meanings ascribed to them in the prospectus and any related prospectus supplement.

TABLE OF CONTENTS FOR STATEMENT OF ADDITIONAL INFORMATION

This Statement of Additional Information is dated February 28, 2020.

USE OF PROCEEDS

Unless otherwise specified in a prospectus supplement, we currently intend to use the net proceeds from the sale of our securities primarily
to invest in accordance with our investment objective and policies within approximately three months of receipt of such proceeds. We may also use proceeds from the sale of our securities to retire all or a portion of any short-term debt we incur in
pursuit of our investment objective and policies and for working capital purposes, including the payment of interest and operating expenses, although there is currently no intent to issue securities primarily for these purposes. Pending such
investments, the net proceeds may be invested in U.S. government securities and high grade, short-term money market instruments. If necessary, the Fund may also purchase, as temporary investments, securities of other open- or closed-end investment
companies that invest primarily in the types of securities in which the Fund may invest directly.

INVESTMENT OBJECTIVE AND POLICIES

The prospectus presents the investment objective and the principal investment strategies and risks of the Fund. This section supplements the
disclosure in the Fund’s prospectus and provides additional information on the Fund’s investment policies or restrictions. Restrictions or policies stated as a maximum percentage of the Fund’s assets are only applied immediately after
a portfolio investment to which the policy or restriction is applicable (other than the limitations on borrowing). Accordingly, any later increase or decrease resulting from a change in values, managed assets or other circumstances will not be
considered in determining whether the investment complies with the Fund’s restrictions and policies.

Primary Investments

Under normal circumstances, the Fund invests at least 80% of its managed assets in a diversified portfolio of convertible securities and
non-convertible income securities. The Fund will provide written notice to shareholders at least 60 days prior to any change to the requirement that it invest at least 80% of its managed assets as described in the sentence above. The portion of the
Fund’s assets invested in convertible securities and non-convertible income securities will vary from time to time consistent with the Fund’s investment objective, changes in equity prices and changes in interest rates and other economic
and market factors, although, under normal circumstances, the Fund will invest at least 35% of its managed assets in convertible securities. “Managed assets” means the total assets of the Fund (including any assets attributable to any
leverage that may be outstanding) minus the sum of accrued liabilities (other than debt representing financial leverage). For this purpose, the liquidation preference on the preferred shares will not constitute a liability.

Convertible Securities

Convertible
securities include any corporate debt security or preferred stock that may be converted into underlying shares of common stock. The common stock underlying convertible securities may be issued by a different entity than the issuer of the convertible
securities. Convertible securities entitle the holder to receive interest payments paid on corporate debt securities or the dividend preference on a preferred stock until such time as the convertible security matures or is redeemed or until the
holder elects to exercise the conversion privilege. As a result of the conversion feature, however, the interest rate or dividend preference on a convertible security is generally less than would be the case if the security were a non-convertible
obligation. The value of convertible securities is influenced by both the yield of non-convertible securities of comparable issuers and by the value of the underlying common stock. A convertible security’s value viewed without regard to its
conversion feature (i.e., strictly on the basis of its yield) is sometimes referred to as its “investment value.” A convertible security’s investment value typically will fluctuate inversely with changes in prevailing interest rates.
However, at the same time, the convertible security will be influenced by its “conversion value,” which is the market value of the underlying common stock that would be obtained if the convertible security were converted. Conversion value
fluctuates directly with the price of the underlying common stock.

S-1

If, because of a low price of the common stock, a convertible security’s conversion
value is substantially below its investment value, the convertible security’s price is governed principally by its investment value. If a convertible security’s conversion value increases to a point that approximates or exceeds its
investment value, the convertible security’s value will be principally influenced by its conversion value. A convertible security will sell at a premium over its conversion value to the extent investors place value on the right to acquire the
underlying common stock while holding a fixed income security. Holders of convertible securities have a claim on the issuer’s assets prior to the common stockholders, but may be subordinated to holders of similar non-convertible securities of
the same issuer.

Synthetic Convertible Instruments

Calamos Advisors LLC (“Calamos”) may create a “synthetic” convertible instrument by combining fixed income securities with
the right to acquire equity securities. More flexibility is possible in the assembly of a synthetic convertible instrument than in the purchase of a convertible security. Although synthetic convertible instruments may be selected where the two
components are issued by a single issuer, thus making the synthetic convertible instrument similar to the true convertible security, the character of a synthetic convertible instrument allows the combination of components representing distinct
issuers, when Calamos believes that such a combination would better promote the Fund’s investment objective. A synthetic convertible instrument also is a more flexible investment in that its two components may be purchased separately. For
example, the Fund may purchase a warrant for inclusion in a synthetic convertible instrument but temporarily hold short-term investments while postponing the purchase of a corresponding bond pending development of more favorable market conditions.

A holder of a synthetic convertible instrument faces the risk of a decline in the price of the security or the level of the index
involved in the convertible component, causing a decline in the value of the call option or warrant purchased to create the synthetic convertible instrument. Should the price of the stock fall below the exercise price and remain there throughout the
exercise period, the entire amount paid for the call option or warrant would be lost. Because a synthetic convertible instrument includes the fixed-income component as well, the holder of a synthetic convertible instrument also faces the risk that
interest rates will rise, causing a decline in the value of the fixed-income instrument.

The Fund may also purchase synthetic
convertible instruments manufactured by other parties, including convertible structured notes. Convertible structured notes are fixed income debentures linked to equity, and are typically issued by investment banks. Convertible structured notes have
the attributes of a convertible security; however, the investment bank that issued the convertible note assumes the credit risk associated with the investment, rather than the issuer of the underlying common stock into which the note is convertible.

The Fund’s holdings of synthetic convertible instruments are considered convertible securities for purposes of the Fund’s
policy to invest at least 35% of its managed assets in convertible securities and 80% of its managed assets in a diversified portfolio of convertible and non-convertible income securities.

Zero Coupon and Payment-in-Kind Securities

Investments in zero coupon and payment-in-kind securities are subject to certain risks, including that market prices of zero coupon and
payment-in-kind securities generally are more volatile than the prices of securities that pay interest periodically and in cash, and are likely to respond to changes in interest rates to a greater degree than other types of debt securities with
similar maturities and credit quality. Because zero coupon securities bear no interest, their prices are especially volatile. And because zero coupon bondholders do not receive interest payments, the prices of zero coupon securities generally fall
more dramatically than those of bonds that pay interest on a current basis when interest rates rise. However, when interest rates fall, the prices of zero coupon securities generally rise more rapidly in value than those of similar interest paying
bonds. Under many market and other conditions, the market for the zero coupon and payment-in-kind securities may suffer decreased

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liquidity making it difficult for the Fund to dispose of them or to determine their current value. In addition, as these securities may not pay cash interest, the Fund’s investment exposure
to these securities and their risks, including credit risk, will increase during the time these securities are held in the Fund’s portfolio. Further, to maintain its qualification for treatment as a regulated investment company and to avoid
Fund-level U.S. federal income and/or excise taxes, the Fund is required to distribute to its shareholders any income it is deemed to have received in respect of such investments, notwithstanding that cash has not been received currently, and the
value of paid-in-kind interest. Consequently, the Fund may have to dispose of portfolio securities under disadvantageous circumstances to generate the cash, or may have to leverage itself by borrowing the cash to satisfy this distribution
requirement. The required distributions, if any, would result in an increase in the Fund’s exposure to these securities.

High Yield Securities

A substantial portion of the Fund’s assets may be invested in below investment grade (high yield) securities. The high yield securities in
which the Fund invests are rated “Ba” or lower by Moody’s Investors Service, Inc. (“Moody’s”) or “BB” or lower by Standard & Poor’s Corporation, a division of The McGraw-Hill Companies
(“S&P” or “Standard & Poor’s”) or are unrated but determined by Calamos to be of comparable quality. Non-convertible debt securities rated below investment grade are commonly referred to as “junk
bonds” and are considered speculative with respect to the issuer’s capacity to pay interest and repay principal.

Below
investment grade non-convertible debt securities or comparable unrated securities are susceptible to greater risk of default or decline in market value due to adverse economic and business developments than higher-rated debt securities. The market
values for high yield securities tend to be very volatile, and these securities are less liquid than investment grade debt securities. For these reasons, your investment in the Fund is subject to the following specific risks:

increased price sensitivity to changing interest rates and to a deteriorating economic environment;

greater risk of loss due to default or declining credit quality;

adverse company specific events are more likely to render the issuer unable to make interest and/or principal
payments; and

if a negative perception of the high yield market develops, the price and liquidity of high yield securities may
be depressed. This negative perception could last for a significant period of time.

Securities rated below investment
grade are speculative with respect to the capacity to pay interest and repay principal in accordance with the terms of such securities. A rating of “Ba1” from Moody’s means that the issue so rated can have speculative elements and is
subject to substantial credit risk. Standard & Poor’s assigns a rating of “BB+” to issues that are less vulnerable to nonpayment than other speculative issues, but nonetheless subject to major ongoing uncertainties or
exposure to adverse business, financial, or economic conditions which could lead to the obligor’s inadequate capacity to meet its financial commitment on the obligation. A rating of “C” from Moody’s means that the issue so rated
can be regarded as having extremely poor prospects of ever attaining any real investment standing. Standard & Poor’s assigns a rating of “C” to issues that are currently highly vulnerable to nonpayment, and the “C”
rating may be used to cover a situation where a bankruptcy petition has been filed or similar action taken, but payments on the obligation are being continued (a “C” rating is also assigned to a preferred stock issue in arrears on
dividends or sinking fund payments, but that is currently paying). See Appendix B to this Statement of Additional Information for a description of Moody’s and Standard & Poor’s ratings.

Adverse changes in economic conditions are more likely to lead to a weakened capacity of a high yield issuer to make principal payments and
interest payments than an investment grade issuer. The principal amount of high yield securities outstanding has proliferated in the past decade as an increasing number of issuers have used high yield securities for corporate financing. An economic
downturn could severely affect the ability

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of highly leveraged issuers to service their debt obligations or to repay their obligations upon maturity. Similarly, down-turns in profitability in specific industries could adversely affect the
ability of high yield issuers in that industry to meet their obligations. The market values of lower quality debt securities tend to reflect individual developments of the issuer to a greater extent than do higher quality securities, which react
primarily to fluctuations in the general level of interest rates. Factors having an adverse impact on the market value of lower quality securities may have an adverse effect on the Fund’s net asset value and the market value of its common
shares. In addition, the Fund may incur additional expenses to the extent it is required to seek recovery upon a default in payment of principal or interest on its portfolio holdings. In certain circumstances, the Fund may be required to foreclose
on an issuer’s assets and take possession of its property or operations. In such circumstances, the Fund would incur additional costs in disposing of such assets and potential liabilities from operating any business acquired.

The secondary market for high yield securities may not be as liquid as the secondary market for more highly rated securities, a factor which
may have an adverse effect on the Fund’s ability to dispose of a particular security when necessary to meet its liquidity needs. There are fewer dealers in the market for high yield securities than investment grade obligations. The prices
quoted by different dealers may vary significantly and the spread between the bid and asked price is generally much larger than higher quality instruments. Under adverse market or economic conditions, the secondary market for high yield securities
could contract further, independent of any specific adverse changes in the condition of a particular issuer, and these instruments may become illiquid. As a result, the Fund could find it more difficult to sell these securities or may be able to
sell the securities only at prices lower than if such securities were widely traded. Prices realized upon the sale of such lower rated or unrated securities, under these circumstances, may be less than the prices used in calculating the Fund’s
net asset value.

Because investors generally perceive that there are greater risks associated with lower quality debt securities of the
type in which the Fund may invest a portion of its assets, the yields and prices of such securities may tend to fluctuate more than those for higher rated securities. In the lower quality segments of the debt securities market, changes in
perceptions of issuers’ creditworthiness tend to occur more frequently and in a more pronounced manner than do changes in higher quality segments of the debt securities market, resulting in greater yield and price volatility.

If the Fund invests in high yield securities that are rated C or below, the Fund will incur significant risk in addition to the risks
associated with investments in high yield securities and corporate loans. Distressed securities frequently do not produce income while they are outstanding. The Fund may purchase distressed securities that are in default or the issuers of which are
in bankruptcy. The Fund may be required to bear certain extraordinary expenses in order to protect and recover its investment.

Distressed Securities

The Fund may, but currently does not intend to, invest up to 5% of its managed assets in distressed securities, including
corporate loans, which are the subject of bankruptcy proceedings or otherwise in default as to the repayment of principal and/or payment of interest at the time of acquisition by the Fund or are rated in the lower rating categories (“Ca”
or lower by Moody’s or “CC” or lower by Standard & Poor’s) or which are unrated investments considered by Calamos to be of comparable quality. Investment in distressed securities is speculative and involves significant
risk of loss. Distressed securities frequently do not produce income while they are outstanding and may require the Fund to bear certain extraordinary expenses in order to protect and recover its investment. Therefore, to the extent the Fund seeks
capital appreciation through investment in distressed securities, the Fund’s ability to achieve current income for its shareholders may be diminished. The Fund also will be subject to significant uncertainty as to when and in what manner and
for what value the obligations evidenced by the distressed securities will eventually be satisfied (e.g., through a liquidation of the obligor’s assets, an exchange offer or plan of reorganization involving the distressed securities or a
payment of some amount in satisfaction of the obligation). In addition, even if an exchange offer is made or a plan of

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reorganization is adopted with respect to distressed securities held by the Fund, there can be no assurance that the securities or other assets received by the Fund in connection with such
exchange offer or plan of reorganization will not have a lower value or income potential than may have been anticipated when the investment was made. Moreover, any securities received by the Fund upon completion of an exchange offer or plan of
reorganization may be restricted as to resale. As a result of the Fund’s participation in negotiations with respect to any exchange offer or plan of reorganization with respect to an issuer of distressed securities, the Fund may be restricted
from disposing of such securities.

Loans

The Fund may invest in loan participations and other direct claims against a borrower. The corporate loans in which the Fund may invest
primarily consist of direct obligations of a borrower and may include debtor in possession financings pursuant to Chapter 11 of the U.S. Bankruptcy Code, obligations of a borrower issued in connection with a restructuring pursuant to Chapter 11 of
the U.S. Bankruptcy Code, leveraged buy-out loans, leveraged recapitalization loans, receivables purchase facilities, and privately placed notes. The Fund may invest in a corporate loan at origination as a co-lender or by acquiring in the secondary
market participations in, assignments of or novations of a corporate loan. By purchasing a participation, the Fund acquires some or all of the interest of a bank or other lending institution in a loan to a corporate or government borrower. The
participations typically will result in the Fund having a contractual relationship only with the lender not the borrower. The Fund will have the right to receive payments of principal, interest and any fees to which it is entitled only from the
lender selling the participation and only upon receipt by the lender of the payments from the borrower. Many such loans are secured, although some may be unsecured. Such loans may be in default at the time of purchase. Loans that are fully secured
offer the Fund more protection than an unsecured loan in the event of non-payment of scheduled interest or principal. However, there is no assurance that the liquidation of collateral from a secured loan would satisfy the corporate borrower’s
obligation, or that the collateral can be liquidated. Direct debt instruments may involve a risk of loss in case of default or insolvency of the borrower and may offer less legal protection to the Fund in the event of fraud or misrepresentation. In
addition, loan participations involve a risk of insolvency of the lending bank or other financial intermediary. The markets in such loans are not regulated by federal securities laws or the Securities and Exchange Commission (“SEC” or the
“Commission”).

As in the case of other high yield investments, such corporate loans may be rated in the lower rating
categories of the established rating services (“Ba” or lower by Moody’s or “BB” or lower by Standard & Poor’s), or may be unrated investments considered by Calamos to be of comparable quality. As in the case of
other high yield investments, such corporate loans can be expected to provide higher yields than lower yielding, higher rated fixed income securities, but may be subject to greater risk of loss of principal and income. There are, however, some
significant differences between corporate loans and high yield bonds. Corporate loan obligations are frequently secured by pledges of liens and security interests in the assets of the borrower, and the holders of corporate loans are frequently the
beneficiaries of debt service subordination provisions imposed on the borrower’s bondholders. These arrangements are designed to give corporate loan investors preferential treatment over high yield investors in the event of a deterioration in
the credit quality of the issuer. Even when these arrangements exist, however, there can be no assurance that the borrowers of the corporate loans will repay principal and/or pay interest in full. Corporate loans generally bear interest at rates set
at a margin above a generally recognized base lending rate that may fluctuate on a day-to-day basis, in the case of the prime rate of a U.S. bank, or which may be adjusted on set dates, typically 30 days but generally not more than one year, in the
case of the London Interbank Offered Rate. Consequently, the value of corporate loans held by the Fund may be expected to fluctuate significantly less than the value of other fixed rate high yield instruments as a result of changes in the interest
rate environment. On the other hand, the secondary dealer market for certain corporate loans may not be as well developed as the secondary dealer market for high yield bonds, and therefore presents increased market risk relating to liquidity and
pricing concerns.

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Foreign Securities

The Fund may invest up to 25% of its net assets in securities of foreign issuers. A foreign security is a security issued by a foreign
government or a company whose country of incorporation is a foreign country. For this purpose, foreign securities do not include American Depositary Receipts (“ADRs”) or securities guaranteed by a U.S. person but which represent underlying
shares of foreign issuers, but may include foreign securities in the form of European Depositary Receipts (“EDRs”), Global Depositary Receipts (“GDRs”) or other securities representing underlying shares of foreign issuers.
Positions in those securities are not necessarily denominated in the same currency as the common stocks into which they may be converted. ADRs are receipts typically issued by an American bank or trust company evidencing ownership of the underlying
securities. EDRs are European receipts listed on the Luxembourg Stock Exchange evidencing a similar arrangement. GDRs are U.S. dollar-denominated receipts issued by international banks evidencing ownership of foreign securities. Generally, ADRs, in
registered form, are designed for the U.S. securities markets and EDRs and GDRs, in bearer form, are designed for use in foreign securities markets. The Fund may invest in sponsored or unsponsored ADRs. In the case of an unsponsored ADR, the Fund is
likely to bear its proportionate share of the expenses of the depository and it may have greater difficulty in receiving shareholder communications than it would have with a sponsored ADR.

To the extent positions in portfolio securities are denominated in foreign currencies, the Fund’s investment performance is affected by
the strength or weakness of the U.S. dollar against those currencies. For example, if the dollar falls in value relative to the Japanese yen, the dollar value of a Japanese stock held in the portfolio will rise even though the price of the stock
remains unchanged. Conversely, if the dollar rises in value relative to the yen, the dollar value of the Japanese stock will fall. (See discussion of transaction hedging and portfolio hedging below under “Currency Exchange Transactions.”)

Investors should understand and consider carefully the risks involved in foreign investing. Investing in foreign securities, which
are generally denominated in foreign currencies, and utilization of forward foreign currency exchange contracts involve certain considerations comprising both risks and opportunities not typically associated with investing in U.S. securities. These
considerations include: fluctuations in exchange rates of foreign currencies; possible imposition of exchange control regulation or currency restrictions that would prevent cash from being brought back to the United States less public information
with respect to issuers of securities; less governmental supervision of stock exchanges, securities brokers, and issuers of securities; lack of uniform accounting, auditing and financial reporting standards; lack of uniform settlement periods and
trading practices; less liquidity and frequently greater price volatility in foreign markets than in the United States; greater costs of buying, holding and selling securities, including brokerage, tax and custody costs; and sometimes less
advantageous legal, operational and financial protections applicable to foreign sub-custodial arrangements.

Although the Fund
intends primarily to invest in companies and government securities of countries having stable political environments, there is the possibility of expropriation or confiscatory taxation, seizure or nationalization of foreign bank deposits or other
assets, establishment of exchange controls, the adoption of foreign government restrictions, or other adverse political, social or diplomatic developments that could affect investment in these nations.

The Fund may invest in the securities of issuers located in emerging market countries. The securities markets of emerging countries are
substantially smaller, less developed, less liquid and more volatile than the securities markets of the U.S. and other more developed countries. Disclosure and regulatory standards in many respects are less stringent than in the U.S. and other major
markets. There also may be a lower level of monitoring and regulation of emerging markets and the activities of investors in such markets, and enforcement of existing regulations has been extremely limited. Economies in individual emerging markets
may differ favorably or unfavorably from the U.S. economy in such respects as growth of gross domestic product, rates of inflation, currency depreciation, capital reinvestment, resource self-sufficiency and balance of payments positions. Many
emerging market countries have experienced high rates of inflation for many years, which has had and may continue to have very negative effects on the economies and securities markets of those countries.

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Currency Exchange Transactions

Currency exchange transactions may be conducted either on a spot (i.e., cash) basis at the spot rate for purchasing or selling currency
prevailing in the foreign exchange market or through forward currency exchange contracts (“forward contracts”). Forward contracts are contractual agreements to purchase or sell a specified currency at a specified future date (or within a
specified time period) and price set at the time of the contract. Forward contracts are usually entered into with banks, foreign exchange dealers and broker-dealers, are not exchange traded, and are usually for less than one year, but may be
renewed.

Forward currency exchange transactions may involve currencies of the different countries in which the Fund may invest and serve
as hedges against possible variations in the exchange rate between these currencies and the U.S. dollar. Currency exchange transactions are limited to transaction hedging and portfolio hedging involving either specific transactions or portfolio
positions, except to the extent described below under “Synthetic Foreign Money Market Positions.” Transaction hedging is the purchase or sale of forward contracts with respect to specific receivables or payables of the Fund accruing in
connection with the purchase and sale of its portfolio securities or the receipt of dividends or interest thereon. Portfolio hedging is the use of forward contracts with respect to portfolio security positions denominated or quoted in a particular
foreign currency. Portfolio hedging allows the Fund to limit or reduce its exposure in a foreign currency by entering into a forward contract to sell such foreign currency (or another foreign currency that acts as a proxy for that currency) at a
future date for a price payable in U.S. dollars so that the value of the foreign denominated portfolio securities can be approximately matched by a foreign denominated liability. The Fund may not engage in portfolio hedging with respect to the
currency of a particular country to an extent greater than the aggregate market value (at the time of making such sale) of the securities held in its portfolio denominated or quoted in that particular currency, except that the Fund may hedge all or
part of its foreign currency exposure through the use of a basket of currencies or a proxy currency where such currencies or currency act as an effective proxy for other currencies. In such a case, the Fund may enter into a forward contract where
the amount of the foreign currency to be sold exceeds the value of the securities denominated in such currency. The use of this basket hedging technique may be more efficient and economical than entering into separate forward contracts for each
currency held in the Fund. The Fund may not engage in “speculative” currency exchange transactions.

If the Fund enters into
a forward contract, the Fund’s custodian will segregate liquid assets of the Fund having a value equal to the Fund’s commitment under such forward contract from day to day, except to the extent that the Fund’s forward contract
obligation is covered by liquid portfolio securities denominated in, or whose value is tied to, the currency underlying the forward contract. At the maturity of the forward contract to deliver a particular currency, the Fund may either sell the
portfolio security related to the contract and make delivery of the currency, or it may retain the security and either acquire the currency on the spot market or terminate its contractual obligation to deliver the currency by purchasing an
offsetting contract with the same currency trader obligating it to purchase on the same maturity date the same amount of the currency. It is impossible to forecast with absolute precision the market value of portfolio securities at the expiration of
a forward contract. Accordingly, it may be necessary for the Fund to purchase additional currency on the spot market (and bear the expense of such purchase) if the market value of the security is less than the amount of currency the Fund is
obligated to deliver and if a decision is made to sell the security and make delivery of the currency. Conversely, it may be necessary to sell on the spot market some of the currency received upon the sale of the portfolio security if its market
value exceeds the amount of currency the Fund is obligated to deliver.

If the Fund retains the portfolio security and engages in an
offsetting currency transaction, the Fund will incur a gain or a loss to the extent that there has been movement in forward contract prices. If the Fund engages in an offsetting currency transaction, it may subsequently enter into a new forward
contract to sell the currency. Should forward prices decline during the period between the Fund’s entering into a forward contract for the sale of a currency and the date it enters into an offsetting contract for the purchase of the currency,
the Fund will realize a gain to the extent the price of the currency it has agreed to sell exceeds the price of the currency it has agreed to purchase. Should forward prices increase, the Fund will suffer a loss to the extent the price of the

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currency it has agreed to purchase exceeds the price of the currency it has agreed to sell. A default on the contract would deprive the Fund of unrealized profits or force the Fund to cover its
commitments for purchase or sale of currency, if any, at the current market price.

Hedging against a decline in the value of a currency
does not eliminate fluctuations in the value of a portfolio security traded in that currency or prevent a loss if the value of the security declines. Hedging transactions also preclude the opportunity for gain if the value of the hedged currency
should rise. Moreover, it may not be possible for the Fund to hedge against a devaluation that is so generally anticipated that the Fund is not able to contract to sell the currency at a price above the devaluation level it anticipates. The cost to
the Fund of engaging in currency exchange transactions varies with such factors as the currency involved, the length of the contract period, and prevailing market conditions.

Synthetic Foreign Money Market Positions

The Fund may invest in money market instruments denominated in foreign currencies. In addition to, or in lieu of, such direct investment, the
Fund may construct a synthetic foreign money market position by (a) purchasing a money market instrument denominated in one currency, generally U.S. dollars, and (b) concurrently entering into a forward contract to deliver a corresponding
amount of that currency in exchange for a different currency on a future date and at a specified rate of exchange. For example, a synthetic money market position in Japanese yen could be constructed by purchasing a U.S. dollar money market
instrument, and entering concurrently into a forward contract to deliver a corresponding amount of U.S. dollars in exchange for Japanese yen on a specified date and at a specified rate of exchange. Because of the availability of a variety of highly
liquid short-term U.S. dollar money market instruments, a synthetic money market position utilizing such U.S. dollar instruments may offer greater liquidity than direct investment in foreign currency and a concurrent construction of a synthetic
position in such foreign currency, in terms of both income yield and gain or loss from changes in currency exchange rates, in general should be similar, but would not be identical because the components of the alternative investments would not be
identical. The Fund currently does not intend to invest a significant amount of its assets in synthetic foreign money market positions.

Debt
Obligations of Non-U.S. Governments

An investment in debt obligations of non-U.S. governments and their political subdivisions
(sovereign debt) involves special risks that are not present in corporate debt obligations. The non-U.S. issuer of the sovereign debt or the non-U.S. governmental authorities that control the repayment of the debt may be unable or unwilling to repay
principal or interest when due, and the Fund may have limited recourse in the event of a default. During periods of economic uncertainty, the market prices of sovereign debt may be more volatile than prices of debt obligations of U.S. issuers. In
the past, certain non-U.S. countries have encountered difficulties in servicing their debt obligations, withheld payments of principal and interest and declared moratoria on the payment of principal and interest on their sovereign debt.

A sovereign debtor’s willingness or ability to repay principal and pay interest in a timely manner may be affected by, among other
factors, its cash flow situation, the extent of its foreign currency reserves, the availability of sufficient non-U.S. currency, the relative size of the debt service burden, the sovereign debtor’s policy toward its principal international
lenders and local political constraints. Sovereign debtors may also be dependent on expected disbursements from non-U.S. governments, multilateral agencies and other entities to reduce principal and interest arrearages on their debt. The failure of
a sovereign debtor to implement economic reforms, achieve specified levels of economic performance or repay principal or interest when due may result in the cancellation of third-party commitments to lend funds to the sovereign debtor, which may
further impair such debtor’s ability or willingness to service its debts.

Eurodollar Instruments and Samurai and Yankee Bonds

The Fund may invest in Eurodollar instruments and Samurai and Yankee bonds. Eurodollar instruments are bonds of corporate and government
issuers that pay interest and principal in U.S. dollars but are issued in

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markets outside the United States, primarily in Europe. Samurai bonds are yen-denominated bonds sold in Japan by non-Japanese issuers. Yankee bonds are U.S. dollar-denominated bonds typically
issued in the U.S. by non-U.S. governments and their agencies and non-U.S. banks and corporations. The Fund may also invest in Eurodollar Certificates of Deposit (“ECDs”), Eurodollar Time Deposits (“ETDs”) and Yankee Certificates
of Deposit (“Yankee CDs”). ECDs are U.S. dollar-denominated certificates of deposit issued by non-U.S. branches of domestic banks; ETDs are U.S. dollar-denominated deposits in a non-U.S. branch of a U.S. bank or in a non-U.S. bank; and
Yankee CDs are U.S. dollar-denominated certificates of deposit issued by a U.S. branch of a non-U.S. bank and held in the U.S. These investments involve risks that are different from investments in securities issued by U.S. issuers, including
potential unfavorable political and economic developments, non-U.S. withholding or other taxes, seizure of non-U.S. deposits, currency controls, interest limitations or other governmental restrictions which might affect payment of principal or
interest.

Lending of Portfolio Securities

The Fund has authorized State Street Bank and Trust Company (“SSB”) as securities lending agent to lend portfolio securities to
broker-dealers and banks. Any such loan must be continuously secured by collateral received in cash under the terms of the Amended and Restated Liquidity Agreement (“SSB Agreement”) between the Fund and SSB. Cash collateral held by SSB on
behalf of the Fund may be credited against the amounts borrowed under the SSB Agreement, such that the Fund will effectively bear lower interest expense with respect to those borrowed amounts. Any amounts credited against the borrowings under SSB
Agreement would count against the Fund’s leverage limitations under the Investment Company Act of 1940, as amended (the “1940 Act”), unless otherwise covered in accordance with SEC Release IC-10666.

Under the terms of the SSB Agreement, SSB will return the value of the collateral to the borrower upon the return of the lent securities,
which will eliminate the credit against the borrowings under SSB Agreement and will increase the balance on which the Fund will pay interest. The Fund is obligated to make payment to the entity in the event SSB is unable to return the value of the
collateral. The Fund would continue to receive the equivalent of the interest or dividends paid by the issuer on the securities loaned, and would also receive an additional return that may be in the form of a fixed fee or a percentage of income
earned on the collateral. The Fund may experience losses as a result of a diminution in value of its cash collateral investments. The Fund may pay reasonable fees to persons unaffiliated with the Fund for services in arranging these loans. The Fund
would have the right to call the loan and obtain the securities loaned at any time on notice of not less than five business days. The Fund would not have the right to vote the securities during the existence of the loan; however, the Fund may
attempt to call back the loan and vote the proxy if time permits prior to the record date. In the event of bankruptcy or other default of the borrower, the Fund could experience both delays in liquidating the loaned collateral (or recovering the
loaned securities) or losses, including (a) possible decline in the value of the collateral or in the value of the securities loaned during the period while the Fund seeks to enforce its rights thereto, (b) possible subnormal levels of
income and lack of access to income during this period and (c) expenses of enforcing its rights. The Fund may also experience losses as a result of the diminution in value of its cash collateral investments. In an effort to reduce these risks,
the Fund’s securities lending agent will monitor, and report to Calamos on, the creditworthiness of the firms to which the Fund lends securities.

Options on Securities, Indices and Currencies

The Fund may purchase and sell (write) put options and call options on securities, indices or foreign currencies. The Fund may purchase
agreements, sometimes called cash puts, that may accompany the purchase of a new issue of bonds from a dealer. The successful use of options depends principally on the price movements of the underlying securities, indices or other reference assets
or rates. Investing in options can result in a greater potential for profit or loss than directly investing in the underlying assets. The value of an option may change because of, including but not limited to, a change in the value of the underlying
assets, the passage of time, changes in the market’s perception as to the future price behavior of the underlying assets or rates, or any combination of the foregoing.

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A put option gives the purchaser of the option, upon payment of a premium, the right to
sell, and the writer the obligation to buy, the underlying security, commodity, index, currency or other instrument at the exercise price. For instance, the Fund’s purchase of a put option on a security might be designed to protect its holdings
in the underlying instrument (or, in some cases, a similar instrument) against a substantial decline in the market value by giving the Fund the right to sell such instrument at the option exercise price. A call option, upon payment of a premium,
gives the purchaser of the option the right to buy, and the seller the obligation to sell, the underlying instrument at the exercise price. The Fund’s purchase of a call option on a security, financial future, index, currency or other
instrument might be intended to protect it against an increase in the price of the underlying instrument that it intends to purchase in the future by fixing the price at which it may purchase such instrument.

Certain options, known as “American style” options, may be exercised at any time during the term of the option. Other options, known
as “European style” options, may be exercised only on the expiration date of the option. The Fund expects that substantially all of the options written by the Fund will be American style options.

The Fund may purchase and sell (write) exchange listed options and over-the-counter options (“OTC options”). Exchange listed options
are issued by a regulated intermediary such as the Options Clearing Corporation (“OCC”), which guarantees the performance of the obligations of the parties to such options. The discussion below uses the OCC as an example, but is also
applicable to other financial intermediaries.

With certain exceptions, OCC issued and exchange listed options generally settle by
physical delivery of the underlying security or currency, although in the future cash settlement may become available. Index options and Eurodollar instruments are cash settled for the net amount, if any, by which the option is
“in-the-money” (i.e., where the value of the underlying instrument exceeds, in the case of a call option, or is less than, in the case of a put option, the exercise price of the option) at the time the option is exercised. Frequently,
rather than taking or making delivery of the underlying instrument through the process of exercising the option, listed options are closed by entering into offsetting purchase or sale transactions that do not result in ownership of the new option.

OTC options are purchased from or sold to securities dealers, financial institutions or other parties (“Counterparties”)
through direct bilateral agreement with the Counterparty. In contrast to exchange listed options, which generally have standardized terms and performance mechanics, all the terms of an OTC option, including such terms as method of settlement, term,
exercise price, premium, guarantees and security, are set by negotiation of the parties. The Fund may sell (write) OTC options (other than OTC currency options) that are subject to a buy-back provision permitting the Fund to require the Counterparty
to sell the option back to the Fund at a formula price within seven days. The Fund generally is expected to enter into OTC options that have cash settlement provisions, although it is not required to do so. The staff of the SEC currently takes the
position that OTC options purchased by a fund, and portfolio securities “covering” the amount of a fund’s obligation pursuant to an OTC option sold by it (or the amount of assets equal to the formula price for the repurchase of the
option, if any, less the amount by which the option is “in the money”) are illiquid.

The Fund may also purchase and sell
(write) options on securities indices and other financial indices. Options on securities indices and other financial indices are similar to options on a security or other instrument except that, rather than settling by physical delivery of the
underlying instrument, they settle by cash settlement, i.e., an option or an index gives the holder the right to receive, upon exercise of the option, an amount of cash if the closing level of the index upon which the option is based exceeds, in the
case of a call, or is less than, in the case of a put, the exercise price of the option (except if, in the case of an OTC option, physical delivery is specified). This amount of cash is equal to the excess of the closing price of the index over the
exercise price of the option, which also may be multiplied by a formula value. The seller of the option is obligated, in return for the premium received, to make delivery of this amount. The gain or loss on an option on an index depends on price
movements in the instruments making upon the market, market segment, industry or other composite on which the underlying index is based, rather than primarily on the price movements in individual securities, as is the case with respect to options on
securities.

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The Fund will write call options and put options only if they are “covered.” For
example, a call option written by the Fund will require the Fund to hold the securities subject to the call (or securities convertible into the needed securities without additional consideration) or to segregate cash or liquid assets sufficient to
purchase and deliver the securities if the call is exercised. A call option sold by the Fund on an index will require the Fund to own portfolio securities which correlate with the index or to segregate cash or liquid assets equal to the excess of
the index value over the exercise price on a current basis. A put option written by the Fund requires the Fund to segregate cash or liquid assets equal to the exercise price.

OTC options entered into by the Fund and OCC issued and exchange listed index options will generally provide for cash settlement. As a result,
when the Fund sells these instruments it will only segregate an amount of cash or liquid assets equal to its accrued net obligations, as there is no requirement for payment or delivery of amounts in excess of the net amount. These amounts will equal
100% of the exercise price in the case of a non cash-settled put, the same as an OCC guaranteed listed option sold by the Fund, or the in-the-money amount plus any sell-back formula amount in the case of a cash-settled put or call. In addition, when
the Fund sells a call option on an index at a time when the in-the-money amount exceeds the exercise price, the Fund will segregate, until the option expires or is closed out, cash or cash equivalents equal in value to such excess. OCC issued and
exchange listed options sold by the Fund other than those above generally settle with physical delivery, or with an election of either physical delivery or cash settlement and the Fund will segregate an amount of cash or liquid assets equal to the
full value of the option. OTC options settling with physical delivery, or with an election of either physical delivery or cash settlement, will be treated the same as other options settling with physical delivery.

If an option written by the Fund expires, the Fund realizes a capital gain equal to the premium received at the time the option was written.
If an option purchased by the Fund expires, the Fund realizes a capital loss equal to the premium paid.

Prior to the earlier of
exercise or expiration, an option may be closed out by an offsetting purchase or sale of an option of the same series (type, exchange, underlying security or index, exercise price and expiration). There can be no assurance, however, that a closing
purchase or sale transaction can be effected when the Fund desires.

The Fund will realize a capital gain from a closing purchase
transaction if the cost of the closing option is less than the premium received from writing the option, or, if it is more, the Fund will realize a capital loss. If the premium received from a closing sale transaction is more than the premium paid
to purchase the option, the Fund will realize a capital gain or, if it is less, the Fund will realize a capital loss. The principal factors affecting the market value of a put or a call option include supply and demand, interest rates, the current
market price of the underlying security or index in relation to the exercise price of the option, the volatility of the underlying security or index, and the time remaining until the expiration date.

A put or call option purchased by the Fund is an asset of the Fund, valued initially at the premium paid for the option. The premium received
for an option written by the Fund is recorded as a deferred credit. The value of an option purchased or written is marked-to-market daily and is valued at the closing price on the exchange on which it is traded or, if not traded on an exchange or no
closing price is available, at the mean between the last bid and asked prices.

Risks Associated with Options

There are several risks associated with transactions in options. For example, there are significant differences between the securities markets,
the currency markets and the options markets that could result in an imperfect correlation among these markets, causing a given transaction not to achieve its objectives. A decision as to whether, when and how to use options involves the exercise of
skill and judgment, and even a well-conceived transaction may be unsuccessful because of market behavior or unexpected events. The Fund’s ability to utilize options successfully will depend on Calamos’ ability to predict pertinent market
investments, which cannot be assured.

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The Fund’s ability to close out its position as a purchaser or seller (writer) of
an OCC or exchange listed put or call option is dependent, in part, upon the liquidity of the option market. Among the possible reasons for the absence of a liquid option market on an exchange are: (i) insufficient trading interest in certain
options; (ii) restrictions on transactions imposed by an exchange; (iii) trading halts, suspensions or other restrictions imposed with respect to particular classes or series of options or underlying securities including reaching daily
price limits; (iv) interruption of the normal operations of the OCC or an exchange; (v) inadequacy of the facilities of an exchange or OCC to handle current trading volume; or (vi) a decision by one or more exchanges to discontinue
the trading of options (or a particular class or series of options), in which event the relevant market for that option on that exchange would cease to exist, although outstanding options on that exchange would generally continue to be exercisable
in accordance with their terms. If the Fund were unable to close out an option that it has purchased on a security, it would have to exercise the option in order to realize any profit or the option would expire and become worthless. If the Fund were
unable to close out a covered call option that it had written on a security, it would not be able to sell the underlying security until the option expired. As the writer of a covered call option on a security, the Fund foregoes, during the
option’s life, the opportunity to profit from increases in the market value of the security covering the call option above the sum of the premium and the exercise price of the call. As the writer of a covered call option on a foreign currency,
the Fund foregoes, during the option’s life, the opportunity to profit from any currency appreciation.

The hours of trading for
listed options may not coincide with the hours during which the underlying financial instruments are traded. To the extent that the option markets close before the markets for the underlying financial instruments, significant price and rate
movements can take place in the underlying markets that cannot be reflected in the option markets.

Unless the parties provide for it,
there is no central clearing or guaranty function in an OTC option. As a result, if the Counterparty (as described above under “Options on Securities, Indices and Currencies”) fails to make or take delivery of the security, currency or
other instrument underlying an OTC option it has entered into with the Fund or fails to make a cash settlement payment due in accordance with the terms of that option, the Fund may lose any premium it paid for the option as well as any anticipated
benefit of the transaction unless the Fund has collected sufficient collateral from the counterparty to cover its exposure. Accordingly, Calamos must assess the creditworthiness of each such Counterparty or any guarantor or credit enhancement of the
Counterparty’s credit to determine the likelihood that the terms of the OTC option will be satisfied. The Fund will engage in OTC option transactions only with U.S. government securities dealers recognized by the Federal Reserve Bank of New
York as “primary dealers” or broker/dealers, domestic or foreign banks or other financial institutions which have received (or the guarantors of the obligation of which have received) a short-term credit rating of “A-1” from
S&P or “P-1” from Moody’s or an equivalent rating from any nationally recognized statistical rating organization (“NRSRO”) or, in the case of OTC currency transactions, are determined to be of equivalent credit quality
by Calamos.

The Fund may purchase and sell (write) call options on securities indices and currencies. All calls sold by the Fund must be
“covered.” Even though the Fund will receive the option premium to help protect it against loss, a call sold by the Fund exposes the Fund during the term of the option to possible loss of opportunity to realize appreciation in the market
price of the underlying security or instrument and may require the Fund to hold the security or instrument that it might otherwise have sold. In addition, a loss on a call option sold may be greater than the premium received. The Fund may purchase
and sell (write) put options on securities indices and currencies. In selling (writing) put options, there is a risk that the Fund may be required to buy the underlying index or currency at a disadvantageous price above the market price. A put
option written by the Fund requires the Fund to segregate cash or liquid assets equal to the exercise price minus any margin the Fund is required to post.

Futures Contracts and Options on Futures Contracts

The Fund may enter into interest rate futures contracts, index futures contracts and foreign currency futures contracts. An interest rate,
index or foreign currency futures contract provides for the future sale by one party and

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purchase by another party of a specified quantity of a financial instrument or the cash value of an index at a specified price and time. A public market exists in futures contracts covering
a number of indices (including, but not limited to, the Standard & Poor’s 500 Index, the Russell 2000 Index, the Value Line Composite Index, and the New York Stock Exchange (“NYSE”) Composite Index) as well as financial
instruments (including, but not limited to, U.S. Treasury bonds, U.S. Treasury notes, Eurodollar certificates of deposit and foreign currencies). Other index and financial instrument futures contracts are available and it is expected that additional
futures contracts will be developed and traded.

The Fund may purchase and write call and put futures options. Futures options possess
many of the same characteristics as options on securities, indices and foreign currencies (discussed above). A futures option gives the holder the right, in return for the premium paid, to assume a long position (call) or short position (put) in a
futures contract at a specified exercise price at any time during the period of the option. Upon exercise of a call option, the holder acquires a long position in the futures contract and the writer is assigned the opposite short position. In the
case of a put option, the opposite is true. The Fund might, for example, use futures contracts to hedge against or gain exposure to fluctuations in the general level of stock prices, anticipated changes in interest rates or currency fluctuations
that might adversely affect either the value of the Fund’s securities or the price of the securities that the Fund intends to purchase. Although other techniques could be used to reduce or increase the Fund’s exposure to stock price,
interest rate and currency fluctuations, the Fund may be able to achieve its desired exposure more effectively and perhaps at a lower cost by using futures contracts and futures options.

The Fund will only enter into futures contracts and futures options that are standardized and traded on an exchange, board of trade or similar
entity, or quoted on an automated quotation system.

The success of any futures transaction by the Fund depends on Calamos correctly
predicting changes in the level and direction of stock prices, interest rates, currency exchange rates and other factors. Should those predictions be incorrect, the Fund’s return might have been better had the transaction not been attempted;
however, in the absence of the ability to use futures contracts, Calamos might have taken portfolio actions in anticipation of the same market movements with similar investment results, but, presumably, at greater transaction costs. When the Fund
makes a purchase or sale of a futures contract, the Fund is required to deposit with its custodian (or broker, if legally permitted) a specified amount of cash or U.S. Government securities or other securities acceptable to the broker (“initial
margin”). The margin required for a futures contract is set by the exchange on which the contract is traded and may be modified during the term of the contract, although the Fund’s broker may require margin deposits in excess of the
minimum required by the exchange. The initial margin is in the nature of a performance bond or good faith deposit on the futures contract, which is returned to the Fund upon termination of the contract, assuming all contractual obligations have been
satisfied. The Fund expects to earn interest income on its initial margin deposits. A futures contract held by the Fund is valued daily at the official settlement price of the exchange on which it is traded. Each day the Fund pays or receives cash,
called “variation margin,” equal to the daily change in value of the futures contract. This process is known as “marking-to-market.” Variation margin paid or received by the Fund does not represent a borrowing or loan by the Fund
but is instead settlement between the Fund and the broker of the amount one would owe the other if the futures contract had expired at the close of the previous day. In computing daily net asset value, the Fund will mark-to-market its open futures
positions.

The Fund is also required to deposit and maintain margin with respect to put and call options on futures contracts
written by it. Such margin deposits will vary depending on the nature of the underlying futures contract (and the related initial margin requirements), the current market value of the option and other futures positions held by the Fund.

Although some futures contracts call for making or taking delivery of the underlying securities, usually these obligations are closed out
prior to delivery by offsetting purchases or sales of matching futures contracts (same exchange, underlying security or index, and delivery month). If an offsetting purchase price is less than the original sale price, the Fund engaging in the
transaction realizes a capital gain, or if it is more, the Fund realizes a

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capital loss. Conversely, if an offsetting sale price is more than the original purchase price, the Fund engaging in the transaction realizes a capital gain, or if it is less, the Fund realizes a
capital loss. The transaction costs must also be included in these calculations.

Risks Associated with Futures

There are several risks associated with the use of futures contracts and futures options. A purchase or sale of a futures contract or option
may result in losses in excess of the amount invested in the futures contract or option. In trying to increase or reduce market exposure, there can be no guarantee that there will be a correlation between price movements in the futures contract or
option and in the portfolio exposure sought. In addition, there are significant differences between the securities and futures markets that could result in an imperfect correlation between the markets, causing a given transaction not to achieve its
objectives. The degree of imperfection of correlation depends on circumstances such as: variations in speculative market demand for futures, futures options and the related securities, including technical influences in futures and futures options
trading and differences between the securities markets and the securities underlying the standard contracts available for trading. For example, in the case of index futures contracts, the composition of the index, including the issuers and the
weighing of each issue, may differ from the composition of the Fund’s portfolio, and, in the case of interest rate futures contracts, the interest rate levels, maturities and creditworthiness of the issues underlying the futures contract may
differ from the financial instruments held in the Fund’s portfolio. A decision as to whether, when and how to use futures contracts involves the exercise of skill and judgment, and even a well-conceived transaction may be unsuccessful to some
degree because of market behavior or unexpected stock price or interest rate trends.

Futures exchanges may limit the amount of
fluctuation permitted in certain futures contract prices during a single trading day. The daily limit establishes the maximum amount that the price of a futures contract may vary either up or down from the previous day’s settlement price at the
end of the current trading session. Once the daily limit has been reached in a futures contract subject to the limit, no more trades may be made on that day at a price beyond that limit. The daily limit governs only price movements during a
particular trading day and therefore does not limit potential losses because the limit may work to prevent the liquidation of unfavorable positions. For example, futures prices have occasionally moved to the daily limit for several consecutive
trading days with little or no trading, thereby preventing prompt liquidation of positions and subjecting some holders of futures contracts to substantial losses. Stock index futures contracts are not normally subject to such daily price change
limitations.

There can be no assurance that a liquid market will exist at a time when the Fund seeks to close out a futures or futures
option position. The Fund would be exposed to possible loss on the position during the interval of inability to close, and would continue to be required to meet margin requirements until the position is closed. In addition, many of the contracts
discussed above are relatively new instruments without a significant trading history. As a result, there can be no assurance that an active secondary market will develop or continue to exist.

Limitations on Options and Futures

If
other options, futures contracts or futures options of types other than those described herein are traded in the future, the Fund may also use those investment vehicles, provided the Board of Trustees determines that their use is consistent with the
Fund’s investment objective.

When purchasing a futures contract or writing a put option on a futures contract, the Fund must
maintain with its custodian (or futures commission merchant (“FCM”), if legally permitted) cash or cash equivalents (including any margin) equal to the market value of such contract. When writing a call option on a futures contract, the
Fund similarly will maintain with its custodian (or FCM) cash or cash equivalents (including any margin) equal to the amount by which such option is in-the-money until the option expires or is closed by the Fund.

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The Fund may not maintain open short positions in futures contracts, call options
written on futures contracts or call options written on indices if, in the aggregate, the market value of all such open positions exceeds the current value of the securities in its portfolio, plus or minus unrealized gains and losses on the open
positions, adjusted for the historical relative volatility of the relationship between the portfolio and the positions. For this purpose, to the extent the Fund has written call options on specific securities in its portfolio, the value of those
securities will be deducted from the current market value of the securities portfolio.

The use of options and futures contracts is
subject to applicable regulations of the SEC, the several exchanges upon which they are traded and the U.S. Commodity Futures Trading Commission (the “CFTC”). In addition, the Fund’s ability to use options and futures contracts may be
limited by tax considerations. See “Certain Federal Income Tax Matters” below. Pursuant to CFTC Regulation 4.5, Calamos, the Fund’s investment adviser, is excluded from the definition of commodity pool operator (“CPO”) under
the Commodity Exchange Act (“CEA”) and is not subject to registration or regulation as such under the CEA. The terms of the exclusion require the Fund, among other things, to adhere to certain limits on its investments in “commodity
interests.” Pursuant to the exemption, if the Fund uses commodity interests (such as futures contracts, options on futures contracts and most swaps) the aggregate initial margin and premiums required to establish these positions (after taking
into account unrealized profits and unrealized losses on any such positions and excluding the amount by which options that are “in-the-money”1 at the time of purchase) may not exceed 5%
of the Fund’s NAV, or alternatively, the aggregate net notional value of those positions, as determined at the time the most recent position was established, may not exceed 100% of the Fund’s NAV (after taking into account unrealized
profits and unrealized losses on any such positions). If, in the future, the Fund can no longer satisfy these requirements, Calamos would withdraw its exclusion from the definition of CPO, and Calamos would be subject to registration and regulation
as a CPO with respect to the Fund, in accordance with CFTC rules that apply to CPOs of registered investment companies.

Warrants

The Fund may invest in warrants. A warrant is a right to purchase common stock at a specific price (usually at a premium above the market value
of the underlying common stock at time of issuance) during a specified period of time. A warrant may have a life ranging from less than a year to twenty years or longer, but a warrant becomes worthless unless it is exercised or sold before
expiration. In addition, if the market price of the common stock does not exceed the warrant’s exercise price during the life of the warrant, the warrant will expire worthless. Warrants have no voting rights, pay no dividends and have no rights
with respect to the assets of the corporation issuing them. The percentage increase or decrease in the value of a warrant may be greater than the percentage increase or decrease in the value of the underlying common stock.

Portfolio Turnover

Although the Fund
does not purchase securities with a view to rapid turnover, there are no limitations on the length of time that a portfolio security must be held. Portfolio turnover can occur for a number of reasons, including calls for redemption, general
conditions in the securities markets, more favorable investment opportunities in other securities, or other factors relating to the desirability of holding or changing a portfolio investment. The portfolio turnover rates may vary greatly from year
to year. A high rate of portfolio turnover in the Fund would result in increased transaction expense, which must be borne by the Fund. High portfolio turnover may also result in the realization of capital gains or losses and, to the extent net
short-term capital gains are realized, any distributions resulting from such gains will be taxed at ordinary income tax rates for U.S. federal income tax purposes.

1

A call option is “in-the-money” to the extent, if any, that the value of the futures contract that is
the subject of the option exceeds the exercise price. A put option is “in-the-money” if the exercise price exceeds the value of the futures contract that is the subject of the option.

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Short Sales

A short sale may be effected when Calamos believes that the price of a security will decline or underperform the market, and involves the sale
of borrowed securities, in the hope of purchasing the same securities at a later date at a lower price. There can be no assurance that the Fund will be able to close out a short position (i.e., purchase the same securities) at any particular time or
at an acceptable or advantageous price. To make delivery to the buyer, the Fund must borrow the securities from a broker-dealer through which the short sale is executed, and the broker-dealer delivers the securities, on behalf of the Fund, to the
buyer. The broker-dealer may be entitled to retain the proceeds from the short sale until the Fund delivers to it the securities sold short or the Fund may receive and invest the proceeds. In addition, the Fund is required to pay to the
broker-dealer the amount of any dividends or interest paid on the securities sold short.

To secure its obligation to deliver to the
broker-dealer the securities sold short, the Fund must segregate an amount of cash or liquid securities that are marked to market daily with its custodian equal to any excess of the current market value of the securities sold short over any cash or
liquid securities deposited as collateral with the broker in connection with the short sale (not including the proceeds of the short sale). As a result of that requirement, the Fund will not gain any leverage merely by selling short, except to the
extent that it earns interest or other income or gains on the segregated cash or liquid securities while also being subject to the possibility of gain or loss from the securities sold short.

The Fund is said to have a short position in the securities sold until it delivers to the broker-dealer the securities sold. The Fund will
normally close out a short position by purchasing on the open market and delivering to the broker-dealer an equal amount of the securities sold short.

The Fund will realize a gain if the price of the securities declines between the date of the short sale and the date on which the Fund
purchases securities to replace the borrowed securities. On the other hand, the Fund will incur a loss if the price of the securities increases between those dates. The amount of any gain will be decreased and the amount of any loss increased by any
premium or interest that the Fund may be required to pay in connection with the short sale. It should be noted that possible losses from short sales differ from those that could arise from a cash investment in a security in that losses from a short
sale may be limitless, while the losses from a cash investment in a security cannot exceed the total amount of the investment in the security.

There is also a risk that securities borrowed by the Fund and delivered to the buyer of the securities sold short will need to be returned to
the broker-dealer on short notice. If the request for the return of securities occurs at a time when other short sellers of the security are receiving similar requests, a “short squeeze” can occur, meaning that the Fund might be compelled,
at the most disadvantageous time, to replace the borrowed securities with securities purchased on the open market, possibly at prices significantly in excess of the proceeds received from the short sale.

It is possible that the market value of the securities the Fund holds in long positions will decline at the same time that the market value of
the securities the Fund has sold short increases, thereby increasing the Fund’s potential volatility.

Rule 10a-1 under the
Securities Exchange Act of 1934, as amended (“Exchange Act”) provides that exchange-traded securities can be sold short only at a price that is higher than the last trade or the same as the last trade price if that price is higher than the
price of the previous reported trade. The requirements of Rule 10a-1 can delay, or in some cases prevent, execution of short sales, resulting in opportunity costs and increased exposure to market action.

The Fund may also make short sales “against the box,” meaning that at all times when a short position is open the Fund owns an equal
amount of such securities or securities convertible into or exchangeable, without payment of further consideration, for securities of the same issue as, and in an amount equal to, the securities sold short. Short sales “against the box”
result in a “constructive sale” and require the Fund to recognize any taxable gain unless an exception to the constructive sale rule applies.

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The Fund will not make a short sale of securities (other than a short sale “against the
box”), if more than 20% of its net assets would be deposited with brokers as collateral or allocated to segregated accounts in connection with all outstanding short sales (other than short sales “against the box”).

Short sales also may afford the Fund an opportunity to earn additional current income to the extent it is able to enter into arrangements with
broker-dealers through which the short sales are executed to receive income with respect to the proceeds of the short sales during the period the Fund’s short positions remain open. Calamos believes that some broker-dealers may be willing to
enter into such arrangements, but there is no assurance that the Fund will be able to enter into such arrangements to the desired degree.

Swaps,
Caps, Floors and Collars

The Fund may enter into interest rate, currency, index, credit default and other swaps and the purchase or sale of
related caps, floors and collars. The Fund expects to enter into these transactions primarily as a hedge to preserve a return or spread on a particular investment or portion of its portfolio, to protect against currency fluctuations, as a duration
management technique or to protect against any increase in the price of securities the Fund anticipates purchasing at a later date. The Fund will not sell interest rate caps or floors where it does not own securities or other instruments providing
the income stream the Fund may be obligated to pay. Interest rate swaps involve the exchange by the Fund with another party of their respective commitments to pay or receive interest, e.g., an exchange of floating rate payments for fixed rate
payments with respect to a notional amount of principal. A currency swap is an agreement to exchange cash flows on a notional amount of two or more currencies based on the relative value differential among them and an index swap is an agreement to
swap cash flows on a notional amount based on changes in the values of the reference indices. A credit default swap is an agreement to transfer the credit exposure of fixed income products between parties. The purchase of a cap entitles the
purchaser to receive payments on a notional principal amount from the party selling such cap to the extent that a specified index exceeds a predetermined interest rate or amount. The purchase of a floor entitles the purchaser to receive payments on
a notional principal amount from the party selling such floor to the extent that a specified index falls below a predetermined interest rate or amount. A collar is a combination of a cap and a floor that preserves a certain return within a
predetermined range of interest rates or values for the purchases.

The Fund will usually enter into swaps or caps on a net basis; that is, the two
payment streams will be netted out in a cash settlement on the payment date or dates specified in the instrument, with the Fund receiving or paying, as the case may be, only the net amount of the two payments. The Fund intends to maintain in a
segregated account with its custodian cash or liquid securities having a value at least equal to the Fund’s net payment obligations under any swap transaction, marked-to-market daily.

The use of swaps and caps is a highly specialized activity that involves investment techniques and risks different from those associated with ordinary
portfolio security transactions. The Fund’s use of swaps or caps could enhance or harm the overall performance on the common shares. To the extent there is a decline in interest rates, the value of the interest rate swap or cap could decline,
and could result in a decline in the net asset value of the common shares. In addition, if short-term interest rates are lower than the Fund’s fixed rate of payment on the interest rate swap, the swap will reduce common share net earnings. If,
on the other hand, short-term interest rates are higher than the fixed rate of payment on the interest rate swap, the swap will enhance common share net earnings. Buying caps could enhance the performance of the common shares by limiting certain
leverage expenses. Buying caps could also decrease the net earnings of the common shares in the event that the premium paid by the Fund to the counterparty exceeds the additional amount the Fund would have been required to pay had it not entered
into the cap agreement. The Fund has no current intention of selling swaps or caps.

Swaps and caps do not involve the delivery of securities or other
underlying assets or principal. Accordingly, the risk of loss with respect to swaps is limited to the net amount of payments that the Fund is contractually obligated to make. If the counterparty defaults, the Fund would not be able to use the
anticipated net receipts under the swap or cap to offset the payments on the Fund’s leverage or offset certain losses in the portfolio. Depending on

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whether the Fund would be entitled to receive net payments from the counterparty on the swap or cap, such a default could negatively impact the performance of the common shares.

Although this will not guarantee the counterparty does not default, the Fund will not enter into any swap, cap, floor or collar transaction unless, at the
time of entering into such transaction, the Fund believes that the counterparty has the financial resources to honor its obligation under the transaction. Further, Calamos will continually monitor the financial stability of a counterparty to a swap
or cap transaction in an effort to proactively protect the Fund’s investments.

In addition, at the time the swap or cap transaction reaches its
scheduled termination date, there is a risk that the Fund would not be able to obtain a replacement transaction or that the terms of the replacement would not be as favorable as on the expiring transaction. If this occurs, it could have a negative
impact on the performance of the Fund’s common shares.

If the Fund were to issue preferred shares, the Fund may choose or be required to redeem some
or all of the preferred shares or prepay any borrowings. Such redemption or prepayment would likely result in the Fund seeking to terminate early all or a portion of any swap or cap transaction. Such early termination of a swap could result in
termination payment by or to the Fund.

The swap market has grown substantially in recent years with a large number of banks and investment banking
firms acting both as principals and as agents utilizing standardized swap documentation. As a result, the swap market has become relatively liquid, however, some swaps may be considered illiquid. Caps, floors and collars are more recent innovations
for which standardized documentation has not yet been fully developed and, accordingly, they are less liquid than certain other swaps.

In addition,
certain categories of interest rate and credit default swaps are, and more in the future will be, centrally cleared. Swaps that are centrally-cleared are subject to the creditworthiness of the clearing organizations involved in the transaction. For
example, a swap investment by the Fund could lose margin payments deposited with the clearing organization, as well as the net amount of gains not yet paid by the clearing organization, if the clearing organization breaches the swap agreement with
the Fund or becomes insolvent or goes into bankruptcy. Also, the Fund will be exposed to the credit risk of the FCM who acts as the Fund’s clearing member on the clearinghouse for a centrally cleared swap. If the Fund’s FCM becomes
bankrupt or insolvent, or otherwise defaults on its obligations to the Fund, the Fund may not receive all amounts owed to it in respect of its trading, even if the clearinghouse fully discharges all of its obligations. In the event of bankruptcy of
the Fund’s FCM, the Fund may be entitled to the net amount of gains the Fund is entitled to receive, plus the return of margin owed to it, only in proportion to the amount received by the FCM’s other customers, potentially resulting in
losses to the Fund.

“When Issued” and Delayed Delivery Securities and Reverse Repurchase Agreements

The Fund may purchase securities on a when issued or delayed delivery basis. Although the payment and interest terms of these securities are
established at the time the Fund enters into the commitment, the securities may be delivered and paid for a month or more after the date of purchase, when their value may have changed. The Fund makes such commitments only with the intention of
actually acquiring the securities, but may sell the securities before settlement date if Calamos deems it advisable for investment reasons. The Fund may utilize spot and forward foreign currency exchange transactions to reduce the risk inherent in
fluctuations in the exchange rate between one currency and another when securities are purchased or sold on a when issued or delayed delivery basis.

The Fund may enter into reverse repurchase agreements with banks and securities dealers. A reverse repurchase agreement is a repurchase
agreement in which the Fund is the seller of, rather than the investor in, securities and agrees to repurchase them at an agreed upon time and price. Use of a reverse repurchase agreement

S-18

may be preferable to a regular sale and later repurchase of securities because it avoids certain market risks and transaction costs. Reverse repurchase agreements involve the risk that the market
value of securities and/or other instruments purchased by the Fund with the proceeds received by the Fund in connection with such reverse repurchase agreements may decline below the market value of the securities the Fund is obligated to repurchase
under such reverse repurchase agreements. They also involve the risk that the counterparty liquidates the securities delivered to it by the Fund under the reverse repurchase agreement following the occurrence of an event of default under the
applicable master repurchase agreement by the Fund.

At the time when the Fund enters into a binding obligation to purchase securities on
a when-issued basis or enters into a reverse repurchase agreement, liquid securities (cash, U.S. Government securities or other “high grade” debt obligations) of the Fund having a value at least as great as the purchase price of the
securities to be purchased will be segregated on the books of the Fund and held by the custodian throughout the period of the obligation. The use of these investment strategies may increase net asset value fluctuation.

Illiquid Securities

The Fund may invest
without limit in securities that, at the time of investment, are illiquid (i.e., any investment that the Fund reasonably expects cannot be sold or disposed of in current market conditions in seven calendar days or less without the sale or
disposition significantly changing the market value of the investment). Illiquid securities may be difficult to dispose of at a fair price at the times when the Fund believes it is desirable to do so. The market price of illiquid securities
generally is more volatile than that of more liquid securities, which may adversely affect the price that the Fund pays for or recovers upon the sale of illiquid securities. Illiquid securities are also more difficult to value and Calamos’
judgment may play a greater role in the valuation process. Investment of the Fund’s assets in illiquid securities may restrict the Fund’s ability to take advantage of market opportunities. The risks associated with illiquid securities may
be particularly acute in situations in which the Fund’s operations require cash and could result in the Fund borrowing to meet its short-term needs or incurring losses on the sale of illiquid securities.

The Fund may invest in bonds, corporate loans, convertible securities, preferred stocks and other securities that lack a secondary trading
market or are otherwise considered illiquid. Liquidity of a security relates to the ability to easily dispose of the security and the price to be obtained upon disposition of the security, which may be less than would be obtained for a comparable
more liquid security. Such investments may affect the Fund’s ability to realize the net asset value in the event of a voluntary or involuntary liquidation of its assets.

Temporary Defensive Investments

The
Fund may make temporary investments without limitation when Calamos determines that a defensive position is warranted. Such investments may be in money market instruments, consisting of obligations of, or guaranteed as to principal and interest by,
the U.S. Government or its agencies or instrumentalities; certificates of deposit, bankers’ acceptances and other obligations of domestic banks having total assets of at least $500 million and that are regulated by the U.S. Government, its
agencies or instrumentalities; commercial paper rated in the highest category by a recognized rating agency; cash; and repurchase agreements. If the Fund temporarily uses a different investment strategy for defensive purposes, different factors
could affect the Fund’s performance, and the Fund may not achieve its investment objective.

Repurchase Agreements

As part of its strategy for the temporary investment of cash, the Fund may enter into “repurchase agreements” with member banks of
the Federal Reserve System or primary dealers (as designated by the Federal Reserve Bank of New York) in such securities. A repurchase agreement arises when the Fund purchases a security and simultaneously agrees to resell it to the vendor at an
agreed upon future date. The resale price is greater than the purchase price, reflecting an agreed upon market rate of return that is effective for the period of

S-19

time the Fund holds the security and that is not related to the coupon rate on the purchased security. Such agreements generally have maturities of no more than seven days and could be used to
permit the Fund to earn interest on assets awaiting long-term investment. The Fund requires continuous maintenance by the custodian for the Fund’s account in the Federal Reserve/Treasury Book Entry System of collateral in an amount equal to, or
in excess of, the market value of the securities that are the subject of a repurchase agreement. Repurchase agreements maturing in more than seven days are considered illiquid securities. In the event of a bankruptcy or other default of a seller of
a repurchase agreement, the Fund could experience both delays in liquidating the underlying security and losses, including: (a) possible decline in the value of the underlying security during the period while the Fund seeks to enforce its
rights thereto; (b) possible subnormal levels of income and lack of access to income during this period; and (c) expenses of enforcing its rights.

Preferred Shares

The Fund may invest in
preferred shares. The preferred shares that the Fund will invest in will typically be convertible securities. Preferred shares are equity securities, but they have many characteristics of fixed income securities, such as a fixed dividend payment
rate and/or a liquidity preference over the issuer’s common shares.

Real Estate Investment Trusts (“REITs”) and Associated Risk
Factors

REITs are pooled investment vehicles which invest primarily in income producing real estate or real estate related loans
or interests. REITs are generally classified as equity REITs, mortgage REITs or a combination of equity and mortgage REITs. Equity REITs invest the majority of their assets directly in real property and derive income primarily from the collection of
rents. Equity REITs can also realize capital gains by selling properties that have appreciated in value. Mortgage REITs invest the majority of their assets in real estate mortgages and derive income from the collection of interest payments. REITs
are not taxed on income and gains distributed to shareholders provided they comply with the applicable requirements of the Internal Revenue Code of 1986, as amended (the “Code”). The Fund will indirectly bear its proportionate share of any
management and other expenses paid by REITs in which it invests in addition to the expenses paid by the Fund. Debt securities issued by REITs are, for the most part, general and unsecured obligations and are subject to risks associated with REITs.

Investing in REITs involves certain unique risks in addition to those risks associated with investing in the real estate industry in
general. An equity REIT may be affected by changes in the value of the underlying properties owned by the REIT. A mortgage REIT may be affected by changes in interest rates and the ability of the issuers of its portfolio mortgages to repay their
obligations. REITs are dependent upon the skills of their managers and are not diversified. REITs are generally dependent upon maintaining cash flows to repay borrowings and to make distributions to shareholders and are subject to the risk of
default by lessees or borrowers. REITs whose underlying assets are concentrated in properties used by a particular industry, such as health care, are also subject to risks associated with such industry.

REITs (especially mortgage REITs) are also subject to interest rate risks. When interest rates decline, the value of a REIT’s investment
in fixed rate obligations can be expected to rise. Conversely, when interest rates rise, the value of a REIT’s investment in fixed rate obligations can be expected to decline. If the REIT invests in adjustable rate mortgage loans the interest
rates on which are reset periodically, yields on a REIT’s investments in such loans will gradually align themselves to reflect changes in market interest rates. This causes the value of such investments to fluctuate less dramatically in
response to interest rate fluctuations than would investments in fixed rate obligations.

REITs may have limited financial resources, may
utilize significant amounts of leverage, may trade less frequently and in a limited volume and may be subject to more abrupt or erratic price movements than larger company securities. Historically REITs have been more volatile in price than the
larger capitalization stocks included in Standard & Poor’s 500 Stock Index.

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Other Investment Companies (including ETFs)

The Fund may invest in the securities of other investment companies, including ETFs, to the extent that such investments are consistent with
the Fund’s investment objective and policies and permissible under the 1940 Act. Under the 1940 Act, the Fund generally may not acquire the securities of other domestic or non-U.S. investment companies if, as a result, (i) more than 10% of
the Fund’s total assets would be invested in securities of other investment companies, (ii) such purchase would result in more than 3% of the total outstanding voting securities of any one investment company being held by the Fund,
(iii) more than 5% of the Fund’s total assets would be invested in any one investment company, or (iv) such purchase would result in more than 10% of the total outstanding voting securities of a registered closed-end investment
company being held by the Fund and other investment companies advised by Calamos. These limitations do not apply to the purchase of shares of money market funds or any investment company in connection with a merger, consolidation, reorganization or
acquisition of substantially all the assets of another investment company, or to purchases of investment companies made in accordance with SEC exemptive relief or rule.

The Fund, as a holder of the securities of other investment companies, will bear its pro rata portion of the other investment companies’
expenses, including advisory fees. These expenses are in addition to the direct expenses of the Fund’s own operations.

Dodd-Frank Act and
Other Derivatives Regulations

The financial crisis in both the U.S. and global economies over the past several years, including
the European sovereign debt crisis, has resulted, and may continue to result, in an unusually high degree of volatility in the financial markets and the economy at large. Both domestic and international equity and fixed income markets have been
experiencing heightened volatility and turmoil, with issuers that have exposure to the real estate, mortgage and credit markets particularly affected. It is uncertain how long these conditions will continue.

In addition to the recent unprecedented turbulence in financial markets, the reduced liquidity in credit and fixed income markets may
negatively affect many issuers worldwide. Reduced liquidity in these markets may mean there is less money available to purchase raw materials, goods and services, which may, in turn, bring down the prices of these economic staples. It may also
result in some issuers having more difficulty obtaining financing and ultimately may lead to a decline in their stock prices. The values of some sovereign debt and of securities of issuers that hold that sovereign debt have fallen. These events, and
the potential for continuing market turbulence, may have an adverse effect on the Fund. In addition, global economies and financial markets are becoming increasingly interconnected, which increases the possibilities that conditions in one country or
region might adversely impact issuers in a different country or region.

Continuing uncertainty as to the status of the Euro and the
European Monetary Union (“EMU”) and the potential for certain countries to withdraw from the institution has created significant volatility in currency and financial markets generally. Any partial or complete dissolution of the EMU could
have significant adverse effects on currency and financial markets, and on the values of the Fund’s portfolio investments.

The U.S.
federal government and certain foreign central banks have acted to calm credit markets and increase confidence in the U.S. and world economies. Certain of these entities have injected liquidity into the markets and taken other steps in an effort to
stabilize the markets and grow the economy. The ultimate effect of these efforts is, of course, not yet known. Changes in government policies may exacerbate the market’s difficulties and the withdrawal of this support, or other policy changes
by governments or central banks, could negatively affect the value and liquidity of certain securities.

The situation in the financial
markets has resulted in calls for increased regulation, and the need of many financial institutions for government help has given lawmakers and regulators new leverage. The Dodd-Frank Act initiated a dramatic revision of the U.S. financial
regulatory framework that is expected to continue to unfold

S-21

over several years. The Dodd-Frank Act covers a broad range of topics, including (among many others) a reorganization of federal financial regulators; a process intended to improve financial
systemic stability and the resolution of potentially insolvent financial firms; new rules for derivatives trading; the creation of the Consumer Financial Protection Bureau; the registration and additional regulation of hedge and private equity fund
managers; and new federal requirements for residential mortgage loans. Instruments in which the Fund may invest, or the issuers of such instruments, may be affected by the new legislation and regulation in ways that may be unforeseeable. Because
these requirements are new and evolving (and some of the rules are not yet final), their ultimate impact remains unclear.

The statutory
provisions of the Dodd-Frank Act significantly change in several respects the ways in which investment products are marketed, sold, settled or terminated. In particular, the Dodd-Frank Act mandates the elimination of references to credit ratings in
numerous securities laws, including the 1940 Act. Transactions in some types of swaps (including interest rate swaps and credit default index swaps on North American and European indices) are required to be centrally cleared. Clearinghouses and
futures commission merchants have broad rights to increase margin requirements for existing cleared transactions or to terminate cleared transactions at any time. Any increase in margin requirements or termination by the clearing member or the
clearinghouse may have an effect on the performance of the Fund.

Under rules adopted under the Dodd-Frank Act, certain derivatives
contracts are required to be executed through swap execution facilities (“SEFs”). A SEF is a trading platform where multiple market participants can execute derivatives by accepting bids and offers made by multiple other participants in
the platform. Such requirements may make it more difficult and costly for investment funds, such as the Fund, to enter into highly tailored or customized transactions. Trading swaps on a SEF may offer certain advantages over traditional bilateral
over-the-counter trading, such as ease of execution, price transparency, increased liquidity and/or favorable pricing. Execution through a SEF is not, however, without additional costs and risks, as parties are required to comply with SEF and CFTC
rules and regulations, including disclosure and recordkeeping obligations, and SEF rights of inspection, among others. SEFs typically charge fees, and if the Fund executes derivatives on an SEF through a broker intermediary, the intermediary may
impose fees as well. The Fund also may be required to indemnify a SEF, or a broker intermediary who executes swaps on a SEF on the Fund’s behalf, against any losses or costs that may be incurred as a result of the Fund’s transactions on
the SEF. In addition, the Fund may be subject to execution risk if it enters into a derivatives transaction that is required to be cleared, and no clearing member is willing to clear the transaction on the Fund’s behalf. In that case, the
transaction might have to be terminated, and the Fund could lose some or all of the benefit of any increase in the value of the transaction after the time of the trade.

The European Union (and some other countries) are implementing similar requirements that will affect the Fund when it enters into derivatives
transactions with a counterparty organized in that country or otherwise subject to that country’s derivatives regulations.

The new
requirements may result in increased uncertainty about counterparty credit risk, and they may also limit the flexibility of the Fund to protect its interests in the event of an insolvency of a derivatives counterparty. In the event of a
counterparty’s (or its affiliate’s) insolvency, the Fund’s ability to exercise remedies, such as the termination of transactions, netting of obligations and realization on collateral, could be stayed or eliminated under new special
resolution regimes adopted in the United States, the European Union and various other jurisdictions. Such regimes provide government authorities with broad authority to intervene when a financial institution is experiencing financial difficulty. In
particular, with respect to counterparties who are subject to such proceedings in the European Union, the liabilities of such counterparties to the Fund could be reduced, eliminated, or converted to equity in such counterparties (sometimes referred
to as a “bail in”).

Additionally, U.S. regulators, the European Union and certain other jurisdictions have adopted minimum
margin and capital requirements for uncleared derivatives transactions. It is expected that these regulations will have a material impact on the Fund’s use of uncleared derivatives. These rules will impose minimum margin

S-22

requirements on derivatives transactions between the Fund and its swap counterparties and may increase the amount of margin the Fund is required to provide. They will impose regulatory
requirements on the timing of transferring margin. The Fund is subject to variation margin requirements under such rules and the Fund may become subject to initial margin requirements under such rules in 2020.

These and other new rules and regulations could, among other things, further restrict the Fund’s ability to engage in, or increase the
cost to the Fund of, derivatives transactions, for example, by making some types of derivatives no longer available to the Fund or otherwise limiting liquidity.

Because the situation in the markets is widespread and largely unprecedented, it may be unusually difficult to identify both risks and
opportunities using past models of the interplay of market forces, or to predict the duration of these market conditions.

INVESTMENT RESTRICTIONS

The following are the Fund’s fundamental investment restrictions. These restrictions may not be
changed without the approval of the holders of a majority of the Fund’s outstanding voting securities (which for this purpose and under the 1940 Act means the lesser of (i) 67% of the common shares represented at a meeting at which more
than 50% of the outstanding common shares are represented or (ii) more than 50% of the outstanding common shares). As long as preferred shares are outstanding, the investment restrictions cannot be changed without the approval of a majority of
the outstanding common and preferred shares, voting together as a class, and the approval of a majority of the outstanding preferred shares, voting separately by class.

The Fund may not:

(1)

Issue senior securities, except as permitted by the 1940 Act and the rules and interpretive positions of the
SEC thereunder.

(2)

Borrow money, except as permitted by the 1940 Act and the rules and interpretive positions of the SEC
thereunder.

(3)

Invest in real estate, except that the Fund may invest in securities of issuers that invest in real estate or
interests therein, securities that are secured by real estate or interests therein, securities of real estate investment funds and mortgage-backed securities.

(4)

Make loans, except by the purchase of debt obligations, by entering into repurchase agreements or through the
lending of portfolio securities and as otherwise permitted by the 1940 Act and the rules and interpretive positions of the SEC thereunder.

(5)

Invest in physical commodities or contracts relating to physical commodities.

(6)

Act as an underwriter, except as it may be deemed to be an underwriter in a sale of securities held in its
portfolio.

(7)

Make any investment inconsistent with the Fund’s classification as a diversified investment company under
the 1940 Act and the rules and interpretive positions of the SEC thereunder.

(8)

Concentrate its investments in securities of companies in any particular industry as defined in the 1940 Act
and the rules and interpretive positions of the SEC thereunder.

All other investment policies of the Fund are
considered non-fundamental and may be changed by the Board of Trustees without prior approval of the Fund’s outstanding voting shares.

Currently under the 1940 Act, the Fund is not permitted to issue preferred shares unless immediately after such issuance the net asset value
of the Fund’s portfolio is at least 200% of the liquidation value of the

S-23

outstanding preferred shares (i.e., such liquidation value may not exceed 50% of the value of the Fund’s total assets). In addition, currently under the 1940 Act, the Fund is not permitted
to declare any cash dividend or other distribution on its common shares unless, at the time of such declaration, the net asset value of the Fund’s portfolio (determined after deducting the amount of such dividend or distribution) is at least
200% of such liquidation value plus any senior securities representing indebtedness. Currently under the 1940 Act, the Fund is not permitted to issue senior securities representing indebtedness unless immediately after such borrowing the Fund has
asset coverage of at least 300% of the aggregate outstanding principal balance of indebtedness (i.e., such indebtedness may not exceed 33 1/3% of the value of the Fund’s total assets). Additionally, currently under the 1940 Act, the Fund
generally may not declare any dividend or other distribution upon any class of its shares, or purchase any such shares, unless the aggregate indebtedness of the Fund has, at the time of the declaration of any such dividend or distribution or at the
time of any such purchase, an asset coverage of at least 300% after deducting the amount of such dividend, distribution, or purchase price, as the case may be, except that dividends may be declared upon any preferred shares if such indebtedness has
an asset coverage of at least 200% at the time of declaration thereof after deducting the amount of the dividend. This limitation does not apply to certain privately placed debt.

Currently under the 1940 Act, the Fund is not permitted to lend money or property to any person, directly or indirectly, if such person
controls or is under common control with the Fund, except for a loan from the Fund to a company which owns all of the outstanding securities of the Fund, except directors’ qualifying shares.

Currently, under interpretive positions of the SEC, the Fund may not have on loan at any time securities representing more than one third of
its total assets.

Currently under the 1940 Act, a “senior security” does not include any promissory note or evidence of
indebtedness where such loan is for temporary purposes only and in an amount not exceeding 5% of the value of the total assets of the issuer at the time the loan is made. A loan is presumed to be for temporary purposes if it is repaid within sixty
days and is not extended or renewed.

Currently, the Fund would be deemed to “concentrate” in a particular industry if it
invested 25% or more of its total assets in that industry.

Currently under the 1940 Act, a “diversified company” means a
management company which meets the following requirements: at least 75% of the value of its total assets is represented by cash and cash items (including receivables), government securities, securities of other investment companies, and other
securities for the purposes of this calculation limited in respect of any one issuer to an amount not greater in value than 5% of the value of the total assets of such management company and not more than 10% of the outstanding voting securities of
such issuer.

Under the 1940 Act, the Fund may not acquire the securities of other domestic or non-U.S. investment companies if, as a
result, (1) more than 10% of the Fund’s total assets would be invested in securities of other investment companies, (2) such purchase would result in more than 3% of the total outstanding voting securities of any one investment
company being held by the Fund, (3) more than 5% of the Fund’s total assets would be invested in any one investment company, or (4) such purchase would result in more than 10% of the total outstanding voting securities of a registered
closed-end investment company being held by the Fund and any other registered investment companies advised by Calamos. These limitations do not apply, however, to the purchase of shares of money market funds or of any investment company in
connection with a merger, consolidation, reorganization or acquisition of substantially all the assets of another investment company, or to purchases of investment companies made in accordance with SEC exemptive relief or rule. As a shareholder in
any investment company, the Fund will bear its ratable share of that investment company’s expenses, and would remain subject to payment of the Fund’s advisory fees and other expenses with respect to assets so invested. Holders of common
shares would therefore be subject to duplicative expenses to the extent the Fund invests in other investment companies. In addition, the securities of other investment companies may also be leveraged and

S-24

will therefore be subject to the same leverage risks described herein and in the prospectus. As described in the prospectus in the section entitled “Risks,” the net asset value and
market value of leveraged shares will be more volatile and the yield to shareholders will tend to fluctuate more than the yield generated by unleveraged shares.

In addition, to comply with federal income tax requirements for qualification as a regulated investment company, the Fund’s investments
will be limited by both an income and an asset test. See “Certain Federal Income Tax Matters.”

As a non-fundamental policy,
the Fund may not issue preferred shares, borrow money and/or issue debt securities with an aggregate liquidation preference and aggregate principal amount exceeding 38% of the Fund’s managed assets measured at the time of borrowing or issuance
of the new securities. Investments of short sale proceeds and economic leverage through derivatives are not considered borrowings.

The Fund presently utilizes leverage through its outstanding borrowings pursuant to the SSB Agreement, and its issuance of mandatory
redeemable preferred shares. See the prospectus (under the caption “Leverage”) for more information about the Fund’s present activities related to the issuance of senior securities and the borrowing of money.

MANAGEMENT OF THE FUND

Trustees and Officers

The Fund’s
Board of Trustees provides broad oversight over the Fund’s affairs. The officers of the Fund are responsible for the Fund’s operations. The Fund’s Trustees and officers are listed below, together with their year of birth, positions
held with the Fund, term of office and length of service and principal occupations during the past five years. Asterisks indicate those Trustees who are interested persons of the Fund within the meaning of the 1940 Act, and they are referred to as
Interested Trustees. Trustees who are not interested persons of the Fund are referred to as “Independent Trustees.” Each of the Trustees serves as a Trustee of other investment companies (26 U.S. registered investment portfolios) for
which Calamos serves as investment adviser (collectively, the “Calamos Funds”). The address for all Independent and Interested Trustees and all officers of the Fund is 2020 Calamos Court, Naperville, Illinois 60563.

Trustees Who Are Interested Persons of the Fund:

NAME ANDYEAR OF BIRTH

POSITION(S) WITH FUND

PORTFOLIOS INFUND COMPLEX^OVERSEEN

PRINCIPAL OCCUPATION(S)

DURING THE PAST 5 YEARS

AND
OTHER DIRECTORSHIPS

John P. Calamos, Sr. (1940)*

Chairman, Trustee and President (since 1988)

Term Expires 2020

Co-Portfolio Manager (since inception)

26
  
Founder, Chairman and Global Chief Investment Officer, Calamos Asset Management, Inc. (“CAM”), Calamos Investments LLC (“CILLC”), Calamos Advisors LLC and its predecessor (“Calamos Advisors”) and
Calamos Wealth Management LLC (“CWM”); Director, CAM; and previously Chief Executive Officer, Calamos Financial Services LLC and its predecessor (“CFS”), CAM, CILLC, Calamos Advisors, and CWM

S-25

Trustees Who Are Not Interested Persons of the Fund:

NAME ANDYEAR OF BIRTH

POSITION(S) WITH FUND

PORTFOLIOS INFUND COMPLEX^OVERSEEN

PRINCIPAL OCCUPATION(S)DURING THE
PAST 5 YEARSAND OTHER DIRECTORSHIPS

John E. Neal (1950)

Trustee (since 2002); Lead Independent Trustee (since July 2019)Term Expires 2021
  
26
  
Retired; private investor; formerly, Director, Equity Residential Trust (publicly-owned REIT); Director, Creation Investments (private international microfinance company); Director, Centrust Bank (Northbrook, Illinois community
bank); Director, Neuro-ID (private company providing prescriptive analytics for the risk industry); Partner, Linden LLC (health care private equity) (until 2019-2020)

William R. Rybak (1951)

Trustee (since 2002)

Term Expires
2020

26
  
Private investor; Chairman (since 2019-2020) and Director (since 2010), Christian Brothers Investment Services Inc.; Trustee, JNL Series Trust, JNL Investors Series Trust, and JNL Variable Fund LLC (since 2007), Jackson Variable Series
Trust (since 2019-2020) and JNL Strategic Income Fund LLC (2007-2019-2020) (open-end mutual funds)**; Trustee, Lewis University (since 2012); formerly Director, Private Bancorp (2003-2019-2020); Executive Vice President and
Chief Financial Officer, Van Kampen Investments, Inc. and subsidiaries (investment manager)

Virginia G. Breen (1964)

Trustee (since 2015)

Term Expires 2022

26
  
Private Investor; Director, Paylocity Holding Corporation (since 2019-2020); Trustee, Neuberger Berman Private Equity Registered Funds (registered private equity funds) (since 2015)***; Trustee, Jones Lang LaSalle Income Property Trust,
Inc. (REIT) (since 2004); Director, UBS A&Q Fund Complex (closed-end funds) (since 2008)****; Director, Bank of America/US Trust Company (until 2015)

Lloyd A. Wennlund (1957)

Trustee (since 2019-2020)

Term Expires 2022

26
  
Expert Affiliate, Bates Group, LLC (financial services consulting and expert testimony firm) (since 2019-2020); Executive Vice President, The

S-26

NAME ANDYEAR OF BIRTH

POSITION(S) WITH FUND

PORTFOLIOS INFUND COMPLEX^OVERSEEN

PRINCIPAL OCCUPATION(S)DURING THE
PAST 5 YEARSAND OTHER DIRECTORSHIPS

Northern Trust Company (1989-2019-2020); President and Business Unit Head of Northern Funds and Northern Institutional Funds (1994-2019-2020); Director, Northern Trust Investments (1998-2019-2020); Governor (2004-2019-2020) and Executive Committee
member (2011-2019-2020), Investment Company Institute Board of Governors; Member, Securities Industry Financial Markets Association (SIFMA) Advisory Council, Private Client Services Committee and Private Client Steering Group (2006-2019-2020); Board Member,
Chicago Advisory Board of the Salvation Army (2011-2019)

Karen L. Stuckey (1953)

Trustee (since December 2019) Term Expires 2020
  
26
  
Member (since 2015) of Desert Mountain Community Foundation Advisory Board (non-profit organization); Emeritus Trustee (since 2007) of Lehigh University; Member, Women’s Investment Management Forum (professional
organization) (since inception); formerly, Trustee, Denver Board of OppenheimerFunds (open-end mutual funds) (2012-2019)

Christopher M. Toub (1959)

Trustee (since December 2019)

Term Expires
2020

26
  
Private investor; formerly, Director of Equities, AllianceBernstein LP (until 2012)

*

Mr. Calamos, Sr. is an “interested person” of the Fund as defined in the 1940 Act because he is
an officer of the Fund and an affiliate of Calamos and CFS.

**

Overseeing 161 portfolios in fund complex.

***

Overseeing five portfolios in fund complex.

****

Overseeing four portfolios in fund complex.

^

The Fund Complex consists of Calamos Investment Trust, Calamos Advisors Trust, Calamos Convertible
Opportunities and Income Fund, Calamos Convertible and High Income Fund, Calamos Strategic Total Return Fund, Calamos Global Total Return Fund, Calamos Global Dynamic Income Fund, Calamos Dynamic Convertible and Income Fund, and Calamos Long/Short
Equity & Dynamic Income Trust.

Officers. The preceding table gives information about Mr. John P.
Calamos, Sr., who is Chairman, Trustee and President of the Fund. The following table sets forth each other officer’s name and year of birth, position with the Fund and date first appointed to that position, and principal occupation(s) during
the past five years.

S-27

Each officer serves until his or her successor is chosen and qualified or until his or her resignation or removal by the board of trustees.

NAME ANDYEAR OF BIRTH

POSITION(S) WITH FUND

PRINCIPAL OCCUPATION(S)

Robert F. Behan (1964)

Vice President (since 2013)
  
President (since 2015), Head of Global Distribution (since 2013), CAM, CILLC, Calamos Advisors and CFS; prior thereto Executive Vice President (2013-2015); Senior Vice President (2009-2013), Head of US Intermediary Distribution
(2010-2013)

Thomas E. Herman (1961)

Vice President (since 2019-2020) and Chief Financial Officer (2019-2020-2019-2020 and since August 2019)
  
Chief Financial Officer, CAM, CILLC, Calamos Advisors, and CWM (since 2019-2020); Chief Financial Officer and Treasurer, Harris Associates (2010-2019-2020)

J. Christopher Jackson (1951)

Vice President and Secretary (since 2010)
  
Senior Vice President, General Counsel and Secretary, CAM, CILLC, Calamos Advisors, CWM and CFS (since 2010); Director, Calamos Global Funds plc (since 2011)

John S. Koudounis (1966)

Vice President (since 2019-2020)
  
Chief Executive Officer, CAM, CILLC, Calamos Advisors, CWM, and CFS (since 2019-2020); Director, CAM (since 2019-2020); President and Chief Executive Officer (2010-2019-2020), Mizuho Securities USA Inc.

Mark J. Mickey (1951)

Chief Compliance Officer (since 2005)
  
Chief Compliance Officer, Calamos Funds (since 2005)

Dave Vanisko (1968)

Treasurer (since August 2019)
  
Head of Fund Administration (since August 2019, Calamos Advisors; prior thereto Assistant Controller (2003-August 2019)

The Fund’s Board of Trustees consists of seven members. In accordance with the Fund’s
Agreement and Declaration of Trust, the Board of Trustees is divided into three classes of approximately equal size. The terms of the trustees of the different classes are staggered. The terms of John P. Calamos, Sr., William R. Rybak, Karen L.
Stuckey and Christopher M. Toub will expire at the annual meeting of shareholders in 2020. The term of John E. Neal will expire at the annual meeting of shareholders in 2021. The terms of Virginia G. Breen and Lloyd A. Wennlund will expire at
the annual meeting of shareholders in 2022. Such classification of the Trustees may prevent the replacement of a majority of the Trustees for up to a two-year period. Each of the Fund’s officers serves until his or her successor is chosen and
qualified or until his or her resignation or removal by the Board of Trustees. In connection with the issuance of the MRP Shares, Mr. Rybak and Ms. Breen were designated as the Trustees who represent the holders of preferred shares of the Fund.

Committees of the Board of Trustees. The Fund’s Board of Trustees currently has five standing committees:

Executive Committee. Messrs. John P. Calamos, Sr. and John E. Neal are members of the Executive Committee, which has authority during
intervals between meetings of the Board of Trustees to exercise the powers of the Board, with certain exceptions.

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Audit Committee. Messrs. William R. Rybak (Chair), John E. Neal, Christopher M.
Toub and Lloyd A. Wennlund and Mses. Virginia G. Breen and Karen L. Stuckey, each a non-interested Trustee, serve on the Audit Committee.

The Audit Committee approves the selection of the independent auditors to the Trustees, approves services to be rendered by the auditors,
monitors the auditors’ performance, reviews the results of the Fund’s audit, determines whether to recommend to the Board that the Fund’s audited financial statements be included in the Fund’s annual report and responds to other
matters deemed appropriate by the Board of Trustees.

Governance Committee. Mses. Virginia G. Breen (Chair) and Karen L. Stuckey
and Messrs. John E. Neal, William R. Rybak, Christopher M. Toub and Lloyd A. Wennlund, each a non-interested Trustee, serve on the Governance Committee. The Governance Committee oversees the independence and effective functioning of the Board of
Trustees and endeavors to be informed about good practices for fund boards. The members of the Governance Committee make recommendations to the Board of Trustees regarding candidates for election as non-interested Trustees. The Governance Committee
will consider shareholder recommendations regarding potential candidates for nomination as Trustees properly submitted to the Governance Committee for its consideration. A Fund shareholder who wishes to nominate a candidate to the Fund’s Board
of Trustees must submit any such recommendation in writing via regular mail to the attention of the Fund’s Secretary, at the address of the Fund’s principal executive offices. The shareholder recommendation must include:

the number and class of all Fund shares owned beneficially and of record by the nominating shareholder at the
time the recommendation is submitted and the dates on which such shares were acquired, specifying the number of shares owned beneficially;

a full listing of the proposed candidate’s education, experience (including knowledge of the investment
company industry, experience as a director or senior officer of public or private companies, and directorships on other boards of other registered investment companies), current employment, date of birth, business and residence address, and the
names and addresses of at least three professional references;

information as to whether the candidate is, has been or may be an “interested person” (as such term is
defined in the 1940 Act) of the Fund, Calamos or any of its affiliates, and, if believed not to be or have been an “interested person,” information regarding the candidate that will be sufficient for the Committee to make such
determination;

the written and signed consent of the candidate to be named as a nominee and to serve as a Trustee of the Fund,
if elected;

a description of all arrangements or understandings between the nominating shareholder, the candidate and/or any
other person or persons (including their names) pursuant to which the shareholder recommendation is being made, and if none, so specify;

the class or series and number of all shares of the Fund owned of record or beneficially by the candidate, as
reported by the candidate; and

such other information that would be helpful to the Governance Committee in evaluating the candidate.

The Governance Committee may require the nominating shareholder to furnish other information it may reasonably require
or deem necessary to verify any information furnished pursuant to the procedures delineated above or to determine the qualifications and eligibility of the candidate proposed by the nominating shareholder to serve as a Trustee. If the nominating
shareholder fails to provide such additional information in writing within seven days of receipt of a written request from the Governance Committee, the recommendation of such candidate as a nominee will be deemed not properly submitted for
consideration, and the Governance Committee is not required to consider such candidate.

Unless otherwise specified by the Governance
Committee’s chairman or by legal counsel to the non-interested Trustees, the Fund’s Secretary will promptly forward all shareholder recommendations to the

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Governance Committee’s chairman and the legal counsel to the non-interested Trustees, indicating whether the shareholder recommendation has been properly submitted pursuant to the procedures
adopted by the Governance Committee for the consideration of trustee candidates nominated by shareholders.

Recommendations for candidates
as trustees will be evaluated, among other things, in light of whether the number of Trustees is expected to change and whether the Trustees expect any vacancies. During periods when the Governance Committee is not actively recruiting new Trustees,
shareholder recommendations will be kept on file until active recruitment is under way. After consideration of a shareholder recommendation, the Governance Committee may dispose of the shareholder recommendation.

Dividend Committee. Mr. John P. Calamos, Sr. serves as the sole member of the dividend committee and Mr. Neal serves as
the liaison to the Dividend Committee for the non-interested Trustees. The Dividend Committee is authorized to declare distributions on the Fund’s shares including, but not limited to, regular dividends, special dividends and short- and
long-term capital gains distributions.

Valuation Committee. Messrs. Lloyd A. Wennlund (Chair), John E. Neal, William R. Rybak and
Christopher M. Toub and Mses. Virginia G. Breen, and Karen L. Stuckey, each a non-interested Trustee, serve on the Valuation Committee.

The Valuation
Committee is responsible for overseeing the implementation of the valuation procedures adopted by the Board of Trustees. The members of the Valuation Committee make recommendations to the Board of Trustees regarding valuation matters relating to the
Fund.

In addition to the above committees, there is a Board of Trustees directed pricing committee comprised of officers of the Fund
and employees of Calamos.

The following table identifies the number of meetings the Board of Trustees and each standing committee
held during the fiscal year ended October 31, 2019.

NUMBER OF MEETINGSDURING FISCAL YEAR ENDEDOctober 31, 2019

Board of Trustees

4

Executive Committee

0

Audit Committee

4

Governance Committee

4

Dividend Committee(1)

0

Valuation Committee

4

(1)

Although the Dividend Committee held no meetings, it acted by written consent on twelve occasions.

The Fund’s Agreement and Declaration of Trust provides that the Fund will indemnify the Trustees and officers
against liabilities and expenses incurred in connection with any claim in which they may be involved because of their offices with the Fund, unless it is determined in the manner specified in the Agreement and Declaration of Trust that they have not
acted in good faith in the reasonable belief that their actions were in the best interests of the Fund or that such indemnification would relieve any officer or Trustee of any liability to the Fund or its shareholders by reason of willful
misfeasance, bad faith, gross negligence or reckless disregard of his or her duties.

Leadership Structure and Qualifications of
the Board of Trustees. The Board of Trustees is responsible for oversight of the Fund. The Fund has engaged Calamos to manage the Fund on a day-to-day basis. The Board of Trustees oversees Calamos and certain other principal service
providers in the operations of the Fund. The Board of Trustees is currently composed of seven members, six of whom are non-interested trustees. The Board of

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Trustees meets in-person at regularly scheduled meetings four times throughout the year. In addition, the Board may meet in-person or by telephone at special meetings or on an informal basis at
other times. As described above, the Board of Trustees has established five standing committees — Audit, Dividend, Executive, Governance and Valuation — and may establish ad hoc committees or working groups from time to time, to assist the
Board of Trustees in fulfilling its oversight responsibilities. The non-interested trustees also have engaged independent legal counsel to assist them in fulfilling their responsibilities. Such independent legal counsel also serves as counsel to the
Fund.

The chairman of the Board of Trustees is an “interested person” of the Fund (as such term is defined in the 1940 Act).
The non-interested trustees have appointed a lead independent trustee. The lead independent trustee serves as a liaison between Calamos and the non-interested trustees and leads the non-interested trustees in all aspects of their oversight of the
Fund. Among other things, the lead independent trustee reviews and approves, with the chairman, the agenda for each board and committee meeting and facilitates communication among the Fund’s non-interested trustees. The Trustees believe that
the Board’s leadership structure is appropriate given the characteristics and circumstances of the Fund. The Trustees also believe that this structure facilitates the exercise of the Board’s independent judgment in fulfilling its oversight
function and efficiently allocates responsibility among committees.

The Board of Trustees has concluded that, based on each
Trustee’s experience, qualifications, attributes or skills on an individual basis and in combination with those of the other Trustees, each Trustee should serve as a member of the Board. In making this determination, the Board has taken into
account the actual service of the Trustees during their tenure in concluding that each should continue to serve. The Board also has considered each Trustee’s background and experience. Set forth below is a brief discussion of the specific
experience qualifications, attributes or skills of each Trustee that led the Board to conclude that he should serve as a Trustee.

Each of Messrs. Calamos, Neal and Rybak has served for more than ten years as a Trustee of the Fund. In addition, each of Mses. Breen and
Stuckey and Messrs. Calamos, Neal, Rybak, Toub and Wennlund has more than 25 years of experience in the financial services industry. Each of Mses. Breen and Stuckey and Messrs. Calamos, Neal, Rybak and Wennlund has experience serving on
boards of other entities, including other investment companies. Each of Ms. Breen and Messrs. Calamos, Neal, Rybak and Toub has earned a Masters of Business Administration degree.

Risk Oversight. The operation of a registered investment company, including its investment activities, generally involves a
variety of risks. As part of its oversight of the Fund, the Board of Trustees oversees risk through various regular board and committee activities. The Board of Trustees, directly or through its committees, reviews reports from, among others,
Calamos, the Fund’s Compliance Officer, the Fund’s independent registered public accounting firm, independent outside legal counsel, and internal auditors of Calamos or its affiliates, as appropriate, regarding risks faced by the Fund and
the risk management programs of Calamos and certain service providers. The actual day-to-day risk management with respect to the Fund resides with Calamos and other service providers to the Fund. Although the risk management policies of Calamos and
the service providers are designed to be effective, there is no guarantee that they will anticipate or mitigate all risks. Not all risks that may affect the Fund can be identified, eliminated or mitigated and some risks simply may not be anticipated
or may be beyond the control of the Board of Trustees or Calamos, its affiliates or other service providers.

Compensation of
Officers and Trustees. John P. Calamos, Sr., the trustee who is an “interested person” of the Fund, does not receive compensation from the Fund. Non-interested trustees are compensated by the Fund, but do not receive any pension
or retirement benefits from the Fund. Mr. Mickey, the Fund’s Chief Compliance Officer, is the only Fund officer who receives compensation from the Fund. The following table sets forth the total compensation (including any amounts deferred,
as described below) paid by the Fund and the Calamos Fund

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Complex during the fiscal year ended October 31, 2019 to each of the current non-interested trustees and the one officer compensated by the Fund.

Name of Trustee

AggregateCompensation fromFund
 
  
Total Compensationfrom CalamosFund Complex(1)*

John P. Calamos, Sr.

$

 
  
$
0

Virginia G. Breen

$
7,811
 
  
$
156,581

John E. Neal(1)

$
9,049
 
  
$
181,505

William R. Rybak

$
8,309
 
  
$
166,556

Karen L. Stuckey(2)

$
1,710
 
  
$
35,750

Christopher M. Toub(2)

$
1,710
 
  
$
35,750

Lloyd A. Wennlund

$
7,811
 
  
$
156,581

Mark J. Mickey

$
7,628
 
  
$
150,000

(1)

Includes fees that may have been deferred during the year pursuant to a deferred compensation plan with Calamos
Investment Trust. Deferred amounts are treated as though such amounts have been invested and reinvested in shares of one or more of the portfolios of the Calamos Investment Trust as selected by the Trustee. As of October 31, 2019, the value of
the deferred compensation account for Mr. Neal was $1,931,728.

(2)

Ms. Stuckey and Mr. Toub were elected to the Board effective December 16, 2019.

*

The Calamos Fund Complex consists of nine investment companies and each applicable series thereunder including
the Fund, Calamos Investment Trust, Calamos Advisors Trust, Calamos Global Total Return Fund, Calamos Convertible and High Income Fund, Calamos Strategic Total Return Fund, Calamos Global Dynamic Income Fund, Calamos Dynamic Convertible and Income
Fund and Calamos Long/Short Equity & Dynamic Income Trust.

The compensation paid to the non-interested
trustees of the Calamos Funds for their services consists of an annual retainer fee in the amount of $100,000, with annual supplemental retainers of $40,000 to the lead independent trustee, $20,000 to the chair of the audit committee and $10,000 to
the chair of any other standing committee. Each non-interested trustee also receives a meeting attendance fee of $7,000 for any regular or special board meeting attended in person, $3,500 for any regular or special board meeting attended by
telephone, and $3,000 for any committee meeting attended in person or by telephone. Compensation paid to the non-interested trustees is allocated among the series of the Calamos Funds in accordance with a procedure determined from time to time by
the Board.

The Fund has adopted a deferred compensation plan for non-interested trustees (the “Plan”). Under the Plan, a
trustee who is not an “interested person” of Calamos and has elected to participate in the Plan (“a participating trustee”) may defer receipt of all or a portion of his compensation from the Fund in order to defer payment of
income taxes or for other reasons. The deferred compensation payable to the participating trustee is credited to the trustee’s deferral account as of the business day such otherwise compensation would have been paid to the trustee. The value of
a trustee’s deferred compensation account at any time is equal to what the value if the amounts credited to the account had instead been invested in Class I shares of one or more of the portfolios of Calamos Investment Trust as designated
by the trustee. Thus, the value of the account increases with contributions to the account or with increases in the value of the measuring shares, and the value of the account decreases with withdrawals from the account or with declines in the value
of the measuring shares. If a participating trustee retires, the trustee may elect to receive payments under the plan in a lump sum or in equal annual installments over a period of five years. If a participating trustee dies, any amount payable
under the Plan will be paid to the trustee’s beneficiaries. Each Calamos Fund’s obligation to make payments under the Plan is a general obligation of that Fund. No Fund is liable for any other Fund’s obligations to make payments under
the Plan.

Ownership of Shares of the Fund and Other Calamos Funds. The following table indicates the value of shares that
each Trustee beneficially owns in the Fund and the Calamos Fund Complex in the aggregate. The

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value of shares of the Calamos Funds is determined on the basis of the net asset value of the class of shares held as of December 31, 2019. The value of the shares held, are stated in ranges
in accordance with the requirements of the SEC. The table reflects the Trustee’s beneficial ownership of shares of the Calamos Fund Complex. Beneficial ownership is determined in accordance with the rules of the SEC.

NAME OF TRUSTEE

DOLLAR RANGEOF EQUITY SECURITIESIN THE FUND
  
AGGREGATE DOLLAR RANGE OFEQUITY SECURITIESIN ALL REGISTERED INVESTMENTCOMPANIES OVERSEEN BY 
TRUSTEEIN THE CALAMOS FUNDS

John P. Calamos, Sr.(1)(2)

Over $100,000
  
Over $100,000

Virginia G. Breen

None
  
Over $100,000

John E. Neal

None
  
Over $100,000

William R. Rybak

$50,001 – $100,000
  
Over $100,000

Karen L. Stuckey(3)

None
  
Over $100,000

Christopher M. Toub(3)

None
  
None

Lloyd A. Wennlund (4)

None
  
None

(1)

Pursuant to Rule 16a-1(a)(2) of the Exchange Act, John P. Calamos, Sr. may be deemed to have indirect
beneficial ownership of Fund shares held by Calamos Investments LLC, its subsidiaries, and its parent companies (Calamos Asset Management, Inc. and Calamos Partners LLC, and its parent company, Calamos Family Partners, Inc.) due to his direct or
indirect ownership interest in those entities. As a result, these amounts reflect any holdings of those entities in addition to the individual, personal accounts of John P. Calamos, Sr.

(2)

Indicates an “interested person” of the Trust, as defined in the 1940 Act.

(3)

Ms. Stuckey and Mr. Toub were elected to the Board effective December 16, 2019.

(4)

As of February 7, 2020, Mr. Wennlund owned shares of the Fund having a value of $50,001 –
$100,000 and shares of funds in the Fund Complex having an aggregate value of over $100,000.

Code of Ethics. The
Fund and Calamos have adopted a code of ethics under Rule 17j-1 under the 1940 Act which is applicable to officers, directors/Trustees and designated employees of Calamos and CFS. Employees of Calamos and CFS are permitted to make personal
securities transactions, including transactions in securities that the Fund may purchase, sell or hold, subject to requirements and restrictions set forth in the code of ethics of Calamos and CFS. The code of ethics contains provisions and
requirements designed to identify and address certain conflicts of interest between personal investment activities of Calamos and CFS employees and the interests of investment advisory clients such as the Fund. Among other things, the code of ethics
prohibits certain types of transactions absent prior approval, imposes time periods during which personal transactions may not be made in certain securities, and requires the submission of duplicate broker confirmations and statements and quarterly
reporting of securities transactions. Additional restrictions apply to portfolio managers, traders, research analysts and others involved in the investment advisory process. Exceptions to these and other provisions of the code of ethics may be
granted in particular circumstances after review by appropriate personnel. Text only versions of the code of ethics can be viewed online or downloaded from the EDGAR Database on the SEC’s internet website at www.sec.gov.

Proxy Voting Procedures. The Fund has delegated proxy voting responsibilities to Calamos, subject to the Board of Trustees’
general oversight. The Fund expects Calamos to vote proxies related to the Fund’s portfolio securities for which the Fund has voting authority consistent with the Fund’s best economic interests. Calamos has adopted its own Proxy Voting
Policies and Procedures (“Policies”). The Policies address, among other things, conflicts of interest that may arise between the interests of the Fund, and the interests of the adviser and its affiliates.

The following is a summary of the Policies used by Calamos in voting proxies.

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To assist it in voting proxies, Calamos has established a Committee comprised of members of
its Portfolio Management and Research Departments. The Committee and/or its members will vote proxies using the following guidelines.

In
general, if Calamos believes that a company’s management and board have interests sufficiently aligned with the Fund’s interest, Calamos will vote in favor of proposals recommended by a company’s board. More specifically, Calamos
seeks to ensure that the board of directors of a company is sufficiently aligned with security holders’ interests and provides proper oversight of the company’s management. In many cases this may be best accomplished by having a majority
of independent board members. Although Calamos will examine board member elections on a case-by-case basis, it will generally vote for the election of directors that would result in a board comprised of a majority of independent directors.

Because of the enormous variety and complexity of transactions that are presented to shareholders, such as mergers, acquisitions,
reincorporations, adoptions of anti-takeover measures (including adoption of a shareholder rights plan, requiring supermajority voting on particular issues, adoption of fair price provisions, issuance of blank check preferred stocks and the creation
of a separate class of stock with unequal voting rights), changes to capital structures (including authorizing additional shares, repurchasing stock or approving a stock split), executive compensation and option plans, that occur in a variety of
industries, companies and market cycles, it is extremely difficult to foresee exactly what would be in the best interests of the Fund in all circumstances. Moreover, voting on such proposals involves considerations unique to each transaction.
Accordingly, Calamos will vote on a case-by-case basis on proposals presenting these transactions.

Finally, Calamos has established
procedures to help resolve conflicts of interests that might arise when voting proxies for the Fund. These procedures provide that the Committee, along with Calamos’ Legal and Compliance Departments, will examine conflicts of interests with the
Fund of which Calamos is aware and seek to resolve such conflicts in the best interests of the Fund, irrespective of any such conflict. If a member of the Committee has a personal conflict of interest, that member will refrain from voting and the
remainder of the Committee will determine how to vote the proxy solely on the investment merits of any proposal. The Committee will then memorialize the conflict and the procedures used to address the conflict.

The Fund is required to file with the SEC its complete proxy voting record for the twelve-month period ending June 30, by no later than
August 31 of each year. The Fund’s proxy voting record for the most recent twelve-month period ending June 30 is available by August 31 of each year (1) on the SEC’s website at www.sec.gov and (2) without charge,
upon request, by calling 1-800-582-6959.

You may obtain a copy of Calamos’ Policies by calling 1-800-582-6959, by visiting the
Fund’s website at www.calamos.com, by writing Calamos at: Calamos Investments, Attn: Client Services, 2020 Calamos Court, Naperville, IL 60563, and on the SEC’s website at www.sec.gov.

Investment Adviser and Investment Management Agreement

Subject to the overall supervision and review of the Board of Trustees, Calamos provides the Fund with investment research, advice and
supervision and furnishes continuously an investment program for the Fund, consistent with the investment objective and policies of the Fund. In addition, Calamos furnishes for use of the Fund such office space and facilities as the Fund may require
for its reasonable needs, supervises the Fund’s business and affairs and provides the following other services on behalf of the Fund and not provided by persons not a party to the investment management agreement: (i) preparing or assisting
in the preparation of reports to and meeting materials for the Trustees; (ii) supervising, negotiating contractual arrangements with, to the extent appropriate, and monitoring the performance of, accounting agents, custodians, depositories,
transfer agents and pricing agents, accountants, attorneys, printers, underwriters, brokers and dealers, insurers and other persons in any capacity deemed to be necessary or desirable to Fund operations; (iii) assisting in the preparation and
making of filings with the SEC and other regulatory and self-regulatory organizations, including, but not limited to,

S-34

preliminary and definitive proxy materials, amendments to the Fund’s registration statement on Form N-2 and reports on Form N-CEN and Form N-CSR; (iv) overseeing the
tabulation of proxies by the Fund’s transfer agent; (v) assisting in the preparation and filing of the Fund’s federal, state and local tax returns; (vi) assisting in the preparation and filing of the Fund’s federal excise
tax returns pursuant to Section 4982 of the Code; (vii) providing assistance with investor and public relations matters; (viii) monitoring the valuation of portfolio securities and the calculation of net asset value;
(ix) monitoring the registration of shares of beneficial interest of the Fund under applicable federal and state securities laws; (x) maintaining or causing to be maintained for the Fund all books, records and reports and any other
information required under the 1940 Act, to the extent that such books, records and reports and other information are not maintained by the Fund’s custodian or other agents of the Fund; (xi) assisting in establishing the accounting
policies of the Fund; (xii) assisting in the resolution of accounting issues that may arise with respect to the Fund’s operations and consulting with the Fund’s independent accountants, legal counsel and the Fund’s other agents
as necessary in connection therewith; (xiii) reviewing the Fund’s bills; (xiv) assisting the Fund in determining the amount of dividends and distributions available to be paid by the Fund to its shareholders, preparing and arranging
for the printing of dividend notices to shareholders, and providing the transfer and dividend paying agent, the custodian, and the accounting agent with such information as is required for such parties to effect the payment of dividends and
distributions; and (xv) otherwise assisting the Fund as it may reasonably request in the conduct of the Fund’s business, subject to the direction and control of the Trustees.

Under the investment management agreement, the Fund pays to Calamos a fee based on the average weekly managed assets that is computed weekly
and payable monthly in arrears. The fee paid by the Fund is set at the annual rate of 0.80% of the Fund’s average weekly managed assets. Because the management fees paid to Calamos are based upon a percentage of the Fund’s managed assets,
the amount of management fees paid to Calamos when the Fund uses leverage will be higher than if the Fund did not use leverage. Therefore, Calamos has a financial incentive to use leverage, which creates a conflict of interest between Calamos and
the Fund’s common shareholders. Subject to the oversight of the Board, Calamos intends to use leverage only when it believes it will serve the best interests of the Fund’s common shareholders.

Under the terms of its investment management agreement with the Fund, except for the services and facilities provided by Calamos as set forth
therein, the Fund shall assume and pay all expenses for all other Fund operations and activities and shall reimburse Calamos for any such expenses incurred by Calamos. The expenses borne by the Fund shall include, without limitation:
(a) organization expenses of the Fund (including out-of-pocket expenses, but not including Calamos’ overhead or employee costs); (b) fees payable to Calamos; (c) legal expenses; (d) auditing and accounting expenses;
(e) maintenance of books and records that are required to be maintained by the Fund’s custodian or other agents of the Fund; (f) telephone, telex, facsimile, postage and other communications expenses; (g) taxes and governmental
fees; (h) fees, dues and expenses incurred by the Fund in connection with membership in investment company trade organizations and the expense of attendance at professional meetings of such organizations; (i) fees and expenses of
accounting agents, custodians, subcustodians, transfer agents, dividend disbursing agents and registrars; (j) payment for portfolio pricing or valuation services to pricing agents, accountants, bankers and other specialists, if any;
(k) expenses of preparing share certificates; (l) expenses in connection with the issuance, offering, distribution, sale, redemption or repurchase of securities issued by the Fund; (m) expenses relating to investor and public
relations provided by parties other than Calamos; (n) expenses and fees of registering or qualifying shares of beneficial interest of the Fund for sale; (o) interest charges, bond premiums and other insurance expenses; (p) freight,
insurance and other charges in connection with the shipment of the Fund’s portfolio securities; (q) the compensation and all expenses (specifically including travel expenses relating to Fund business) of Trustees, officers and employees of
the Fund who are not affiliated persons of Calamos; (r) brokerage commissions or other costs of acquiring or disposing of any portfolio securities of the Fund; (s) expenses of printing and distributing reports, notices and dividends to
shareholders; (t) expenses of preparing and setting in type, printing and mailing prospectuses and statements of additional information of the Fund and supplements thereto; (u) costs of stationery; (v) any litigation expenses;
(w) indemnification of Trustees and officers of the Fund; (x) costs of shareholders’ and other meetings;

S-35

(y) interest on borrowed money, if any; and (z) the fees and other expenses of listing the Fund’s shares on Nasdaq or any other national stock exchange.

For the fiscal years ended October 31, 2019-2020, October 31, 2019-2020 and October 31, 2019, the Fund incurred $8,720,578, $9,363,206
and $9,012,929 respectively, in advisory fees.

The investment management agreement had an initial term ending August 1, 2003
and continues in effect from year to year thereafter so long as such continuation is approved at least annually by (1) the Board of Trustees or the vote of a majority of the outstanding voting securities (as defined in the 1940 Act) of the
Fund, and (2) a majority of the Trustees who are not interested persons of any party to the investment management agreement, cast in person at a meeting called for the purpose of voting on such approval. The investment management agreement may
be terminated at any time, without penalty, by either the Fund or Calamos upon 60 days’ written notice, and is automatically terminated in the event of its assignment as defined in the 1940 Act.

Calamos is a wholly-owned subsidiary of Calamos Investments LLC (“CILLC”). Calamos Asset Management, Inc. (“CAM”) is the
sole manager of CILLC and a wholly-owned subsidiary of Calamos Partners LLC (“CPL”). As of January 31, 2020, approximately 22% of the outstanding equity interest of CILLC is owned by CAM and the remaining approximately 78% of CILLC is
owned by CPL and John P. Calamos, Sr. CPL is owned by Calamos Family Partners, Inc. (“CFP”), John P. Calamos, Sr., and John S. Koudounis. CFP is owned by members of the Calamos family, including John P. Calamos, Sr. In addition,
Mr. Koudounis has the option to purchase a controlling interest in CPL upon the death or permanent disability of John P. Calamos, Sr., provided Mr. Koudounis is then serving as Chief Executive Officer of CAM and CILLC. John P. Calamos, Sr.
is an affiliated person of the Fund and Calamos by virtue of his position as Chairman, Trustee and President of the Fund and Chairman and Global Chief Investment Officer (“Global CIO”) of Calamos. John S. Koudounis, Robert F. Behan,
Thomas E. Herman, J. Christopher Jackson and Dave Vanisko are affiliated persons of the Fund and Calamos by virtue of their positions as Vice President; Vice President; Vice President and Chief Financial Officer; Vice President and Secretary; and
Treasurer of the Fund, respectively, and as Chief Executive Officer; President and Head of Global Distribution; Chief Financial Officer; Senior Vice President, General Counsel and Secretary; and Head of Fund Administration of Calamos, respectively.

A discussion regarding the basis for the Board of Trustees’ decision to approve the renewal of the Investment Management Agreement
is available in the Fund’s Annual Report to shareholders for the fiscal year ended October 31, 2019.

The use of the name
“Calamos” in the name of the Fund is pursuant to licenses granted by CILLC, and the Fund has agreed to change its name to remove that reference if Calamos ceases to act as investment adviser to the Fund.

Portfolio Managers

John P. Calamos,
Sr. During the past five years, John P. Calamos, Sr. has been President, Trustee and Co-Portfolio Manager of the Fund since inception and for Calamos: Founder, Chairman and Global CIO since August 2019-2020; Chairman and Global CIO from April to
August 2019-2020; Chairman, Chief Executive Officer and Global Co-CIO between April 2013 and April 2019-2020; Chief Executive Officer and Global Co-CIO between August 2012 and April 2013; and Chief Executive Officer and Co-CIO prior thereto.

Dennis Cogan. Dennis Cogan joined Calamos in March 2005 and since March 2013 is a Co-Portfolio Manager. Between March 2005 and
March 2013 he was a senior strategy analyst.

R. Matthew Freund. R. Matthew Freund joined Calamos in November 2019-2020 as a
Co-CIO, Head of Fixed Income Strategies, as well as a Senior Co-Portfolio Manager. Previously, he was SVP of Investment Portfolio Management and Chief Investment Officer at USAA Investments since 2010.

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John Hillenbrand. John Hillenbrand joined Calamos in 2002 and since September
2015 is a Co-CIO, Head of Multi-Asset Strategies and Co-Head of Convertible Strategies, as well as a Senior Co-Portfolio Manager. From March 2013 to September 2015 he was a Co-Portfolio Manager. Between August 2002 and March 2013 he was a senior
strategy analyst.

Nick Niziolek. Nick Niziolek joined Calamos in March 2005 and has been a Co-CIO, Head of Global
Strategies, as well as a Senior Co-Portfolio Manager, since September 2015. Between August 2013 and September 2015 he was a Co-Portfolio Manager, Co-Head of Research. Between March 2013 and August 2013 he was a Co-Portfolio Manager. Between March
2005 and March 2013 he was a senior strategy analyst.

Eli Pars. Eli Pars joined Calamos in May 2013 and has been a
Co-CIO, Head of Alternative Strategies and Co-Head of Convertible Strategies, as well as Senior Co-Portfolio Manager, since September 2015. Between May 2013 and September 2015, he was a Co-Portfolio Manager. Previously, he was a Portfolio Manager at
Chicago Fundamental Investment Partners from February 2009 until November 2012.

Jon Vacko. Jon Vacko joined Calamos in
June 2000 and has been a Senior Co-Portfolio Manager since September 2015. Previously, he was a Co-Portfolio Manager from August 2013 to September 2015; prior thereto he was a Co-Head of Research and Investments from July 2010 to August 2013.

Joe Wysocki. Joe Wysocki joined Calamos in October 2003 and since March 2015 is a Co-Portfolio Manager. Previously,
Mr. Wysocki was a sector head from March 2014 to March 2015. Prior thereto, he was a Co-Portfolio Manager from March 2013 to March 2014. Between February 2007 and March 2013 he was a senior strategy analyst.

Calamos employs a “team of teams” approach to portfolio management, led by the Global CIO and our CIO team consisting of 5 Co-CIOs
with specialized areas of investment expertise. The Global CIO and Co-CIO team are responsible for oversight of investment team resources, investment processes, performance and risk. As heads of investment verticals, Co-CIOs manage investment team
members and, along with Co-Portfolio Managers, have day-to-day portfolio oversight and construction responsibilities of their respective investment strategies. While investment research professionals within each Co-CIO’s team are assigned
specific strategy responsibilities, they also provide support to other investment team verticals, creating deeper insights across a wider range of investment strategies. The combination of specialized investment teams with cross team collaboration
results in what we call our team of teams approach.

This team of teams approach is further reflected in the composition of
Calamos’ Investment Committee, made up of the Global CIO, the Co-CIO team, the Head of Global Trading, and the Chief of IT and Operations. Other members of the investment team participate in Investment Committee meetings in connection with
specific investment related issues or topics as deemed appropriate.

The structure and composition of the Investment Committee results
in a number of benefits, as it:

Leads to broader perspective on investment decisions: multiple viewpoints and areas of expertise feed into
consensus;

Promotes collaboration between teams; and

Functions as a think tank with the goal of identifying ways to outperform the market on a risk-adjusted basis.

The objectives of the Investment Committee are to:

Form the firm’s top-down macro view, market direction, asset allocation, and sector/country positioning.

Establish firm-wide secular and cyclical themes for review.

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Review firm-wide and portfolio risk metrics, recommending changes where appropriate.

Review firm-wide, portfolio and individual security liquidity constraints.

Evaluate firm-wide and portfolio investment performance.

Evaluate firm-wide and portfolio hedging policies and execution.

Evaluate enhancements to the overall investment process.

John P. Calamos, Sr., Founder, Chairman and Global CIO, is responsible for the day-to-day management of the team, bottom-up research efforts
and strategy implementation. R. Matthew Freund, John Hillenbrand, Nick Niziolek, Eli Pars, and Jon Vacko are each Sr. Co-Portfolio Managers, and Dennis Cogan and Joe Wysocki are each Co-Portfolio Managers.

For over 20 years, the Calamos portfolio management team has managed money for their clients in convertible, high yield and global strategies.
Furthermore, Calamos has extensive experience investing in foreign markets through its convertible securities and high yield securities strategies. Such experience has included investments in established as well as emerging foreign markets.

The Global CIO, Sr. Co-Portfolio Managers and Co-Portfolio Managers also have responsibility for the day-to-day management of accounts other
than the Fund. Information regarding these other accounts as of October 31, 2019 is set forth below:

Other Accounts Managed and Assets by Account
Type as of October 31, 2019

RegisteredInvestmentCompanies
 
  
Other PooledInvestmentVehicles
 
  
OtherAccounts
 

 
  
Accounts
 
  
Assets
 
  
Accounts
 
  
Assets
 
  
Accounts
 
  
Assets

John P. Calamos, Sr.

22
 
  
 
20,948,430,824
 
  
 
7
 
  
 
602,462,665
 
  
 
2,987
 
  
 
2,146,154,412

R. Matthew Freund

13
 
  
 
10,219,327,480
 
  
 
1
 
  
 
236,209,807
 
  
 
2,314
 
  
 
1,637,267,916

John Hillenbrand

19
 
  
 
11,936,190,360
 
  
 
7
 
  
 
602,462,665
 
  
 
2,987
 
  
 
2,146,154,412

Nick Niziolek

10
 
  
 
6,865,778,886
 
  
 
6
 
  
 
366,252,858
 
  
 
2,078
 
  
 
888,330,672

Eli Pars

18
 
  
 
19,428,325,425
 
  
 
7
 
  
 
602,462,665
 
  
 
2,319
 
  
 
1,682,341,962

Jon Vacko

19
 
  
 
11,936,190,360
 
  
 
7
 
  
 
602,462,665
 
  
 
2,987
 
  
 
2,146,154,412

Dennis Cogan

10
 
  
 
6,865,778,886
 
  
 
6
 
  
 
366,252,858
 
  
 
2,078
 
  
 
888,330,672

Joe Wysocki

11
 
  
 
9,923,291,097
 
  
 
4
 
  
 
586,193,466
 
  
 
2,182
 
  
 
1,045,109,351

Number of Accounts and Assets for which Advisory Fee is Performance Based as of October 31, 2019

RegisteredInvestmentCompanies
 
  
Other PooledInvestmentVehicles
 
  
OtherAccounts
 

 
  
Accounts
 
  
Assets
 
  
Accounts
 
  
Assets
 
  
Accounts
 
  
Assets

John P. Calamos, Sr.

2
 
  
 
285,877,403
 
  
 

 
  
 

 
  
 

 
  
 

R. Matthew Freund


 
  
 

 
  
 

 
  
 

 
  
 

 
  
 

John Hillenbrand

2
 
  
 
285,877,403
 
  
 

 
  
 

 
  
 

 
  
 

Nick Niziolek

2
 
  
 
285,877,403
 
  
 

 
  
 

 
  
 

 
  
 

Eli Pars

2
 
  
 
285,877,403
 
  
 

 
  
 

 
  
 

 
  
 

Jon Vacko

2
 
  
 
285,877,403
 
  
 

 
  
 

 
  
 

 
  
 

Dennis Cogan

2
 
  
 
285,877,403
 
  
 

 
  
 

 
  
 

 
  
 

Joe Wysocki


 
  
 

 
  
 

 
  
 

 
  
 

 
  
 

Each Co-Portfolio Manager may invest for his own benefit in securities held in brokerage and mutual fund
accounts. The information shown in the table does not include information about those accounts where the

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Co-Portfolio Manager or members of his family have a beneficial or pecuniary interest because no advisory relationship exists with Calamos or any of its
affiliates.

The Fund’s Co-Portfolio Managers are responsible for managing both the Fund and other accounts, including separate
accounts and funds not required to be registered under the 1940 Act.

Other than potential conflicts between investment strategies,
the side-by-side management of both the Fund and other accounts may raise potential conflicts of interest due to the interest held by Calamos in an account and certain trading practices used by the portfolio managers (e.g., cross-trades between the
Fund and another account and allocation of aggregated trades). Calamos has developed policies and procedures reasonably designed to mitigate those conflicts. For example, Calamos will place cross-trades in securities held by the Fund only in
accordance with the rules promulgated under the 1940 Act and has adopted policies designed to ensure the fair allocation of securities purchased on an aggregated basis.

The allocation methodology employed by Calamos varies depending on the type of securities sought to be bought or sold and the type of client
or group of clients. Generally, however, orders are placed first for those clients that have given Calamos brokerage discretion (including the ability to step out a portion of trades), and then to clients that have directed Calamos to execute trades
through a specific broker. However, if the directed broker allows Calamos to execute with other brokerage firms, which then book the transaction directly with the directed broker, the order will be placed as if the client had given Calamos full
brokerage discretion. Calamos and its affiliates frequently use a “rotational” method of placing and aggregating client orders and will build and fill a position for a designated client or group of clients before placing orders for other
clients. A client account may not receive an allocation of an order if: (a) the client would receive an unmarketable amount of securities based on account size; (b) the client has precluded Calamos from using a particular broker;
(c) the cash balance in the client account will be insufficient to pay for the securities allocated to it at settlement; (d) current portfolio attributes make an allocation inappropriate; and (e) account specific guidelines,
objectives and other account specific factors make an allocation inappropriate. Allocation methodology may be modified when strict adherence to the usual allocation is impractical or leads to inefficient or undesirable results. Calamos’ head
trader must approve each instance that the usual allocation methodology is not followed and provide a reasonable basis for such instances and all modifications must be reported in writing to Calamos’ Chief Compliance Officer on a monthly basis.

Investment opportunities for which there is limited availability generally are allocated among participating client accounts
pursuant to an objective methodology (i.e., either on a pro rata basis or using a rotational method, as described above). However, in some instances, Calamos may consider subjective elements in attempting to allocate a trade, in which case the Fund
may not participate, or may participate to a lesser degree than other clients, in the allocation of an investment opportunity. In considering subjective criteria when allocating trades, Calamos is bound by its fiduciary duty to its clients to treat
all client accounts fairly and equitably.

The Co-Portfolio Managers advise certain accounts under a performance fee arrangement. A
performance fee arrangement may create an incentive for a Co-Portfolio Manager to make investments that are riskier or more speculative than would be the case in the absence of performance fees. A performance fee arrangement may result in increased
compensation to the Co-Portfolio Managers from such accounts due to unrealized appreciation as well as realized gains in the client’s account.

As of October 31, 2019, John P. Calamos, Sr., our Global CIO, aside from distributions arising from his ownership from various entities,
receives all of his compensation from Calamos. He has entered into an employment agreement that provides for compensation in the form of an annual base salary and an annual bonus, both components payable in cash. Similarly, Mr. Calamos, Sr., is
eligible for a Long-Term Incentive (“LTI”). The LTI program at Calamos currently consists of deferred bonus payments, which fluctuate in value over time based upon either (1) the performance of certain managed investment products for
investment professionals (“Mutual Fund Incentive Awards”); or (2) the overall value of the firm for non-investment professionals (“Company Incentive Awards”).

S-39

As of October 31, 2019, R. Matthew Freund, John Hillenbrand, Nick Niziolek, Eli
Pars, Jon Vacko, Dennis Cogan, and Joe Wysocki receive all of their compensation from Calamos. These individuals each receive compensation in the form of an annual base salary, a discretionary bonus (payable in cash) and are eligible for
discretionary Mutual Fund Incentive Awards. Additionally, Messrs. Hillenbrand, Niziolek, and Pars received additional compensation awards in prior years.

The amounts paid to all Co-Portfolio Managers, together with the criteria utilized to determine such amounts, are benchmarked against industry
specific data provided by third party analytical agencies. The Co-Portfolio Managers’ compensation structure considers annually the performance of the various strategies managed by the Co-Portfolio Managers, among other factors, including,
without limitation, the overall performance of the firm.

At October 31, 2019, each portfolio manager beneficially owned (as
determined pursuant to Rule 16a-1(a)(2) under the Exchange Act) shares of the Fund having value within the indicated dollar ranges.

Portfolio Manager

Fund

John P. Calamos, Sr.(1)

$100,001 – $500,000

Nick Niziolek

None

Dennis Cogan

None

John Hillenbrand

None

Jon Vacko

None

Joe Wysocki

None

Eli Pars

None

R. Matthew Freund

None

(1)

Pursuant to Rule 16a-1(a)(2) of the Exchange Act, John P. Calamos, Sr. may be deemed to have indirect
beneficial ownership of Fund shares held by Calamos Investments LLC, its subsidiaries, and its parent companies (Calamos Asset Management, Inc. and Calamos Partners LLC, and its parent company Calamos Family Partners, Inc.) due to his direct or
indirect ownership interest in those entities. As a result, these amounts reflect any holdings of those entities in addition to the individual, personal accounts of John P. Calamos, Sr.

Fund Accountant and Administration Arrangements

The
Fund has entered into an agreement with Ernst & Young LLP (“EY”) located at 155 N. Wacker Drive, Chicago, IL 60606 to provide certain tax services to the Fund. The tax services include the following: calculating, tracking and
reporting tax adjustments on all assets of the Fund, including but not limited to contingent debt and preferred trust obligations; preparing excise tax and fiscal year distribution schedules; preparing tax information required for financial
statement footnotes; preparing state and federal income tax returns; preparing specialized calculations of amortization on convertible securities; preparing year-end dividend disclosure information providing treaty-based foreign withholding tax
reclaim services; providing certain global compliance and reporting services; providing a match service and analysis of the “passive foreign investment company” status of foreign corporate entities; and providing services related to
corporate actions that may or may not have a tax impact on the Fund’s holdings. For the fiscal years ended October 31, 2019, October 31, 2019-2020 and October 31, 2019-2020, the Fund paid EY $48,931, $0, and $0, respectively, for tax
services.

Under the arrangements with State Street Bank and Trust Company (“State Street”) located at One Iron Street, Boston, MA 02111 to
provide fund accounting services, State Street provides certain administrative and accounting services including providing daily reconciliation of cash, trades and positions; maintaining general ledger and capital stock accounts; preparing daily
trial balance; calculating net asset value; providing selected general ledger reports; preferred share compliance; calculating total returns; and providing monthly distribution analysis to the Fund. For the fiscal years ended October 31,
2019, October 31, 2019-2020 and October 31, 2019-2020, the

S-40

Fund paid State Street $79,226, $82,471 and $78,372, respectively, for fund accounting services. The Fund has also entered into an agreement with State Street pursuant to which State Street
provides certain administration treasury services to the Fund. These services include: monitoring the calculation of expense accrual amounts for the Fund and making any necessary modifications; managing the Fund’s expenses and expense payment
processing; coordinating any expense reimbursement calculations and payment; calculating net investment income dividends and capital gain distributions; coordinating the audits for the Fund; preparing financial reporting statements for the Fund;
preparing certain regulatory filings; and calculating asset coverage tests for certain Calamos Funds. For the fiscal years ended October 31, 2019, October 31, 2019-2020 and October 31, 2019-2020, the Fund paid State Street $100,026, $0,
and $0, respectively, for administration services. Under a prior agreement for administration services, the Fund paid the previous service provider $0, $135,065 and $126,750 for the fiscal years ended, October 31, 2019, October 31, 2019-2020 and
October 31, 2019-2020, respectively.

CERTAIN SHAREHOLDERS

At January 31, 2020, the following persons were known to own beneficially or of record more than 5% of the outstanding securities of the
Fund:

Class of Shares

Name and Address of Beneficial Owner

Number ofSharesOwned
 
  
Percent ofClass

Common

National Financial Services LLC

499
Washington Blvd.

Jersey City, NJ 07310

8,718,832
 
  
 
12.3
%

Charles Schwab & Co., Inc.

2423 E.
Lincoln Drive

Phoenix, AZ 85016-1215

7,387,928
 
  
 
10.4
%

Merrill Lynch Pierce Fenner & Smith

4804 Deer Lake Dr. E.

Jacksonville, FL 32246

6,946,977
 
  
 
9.8
%

TD Ameritrade

200 S. 108th Ave

Omaha, NE 68154

5,799,962
 
  
 
8.2
%

Common

Morgan Stanley Smith Barney LLC

1300 Thames
Street

6th Floor

Baltimore, MD 21231

5,398,218
 
  
 
7.6
%

UBS Financial Services Inc.

1000 Harbor
Blvd

Weehawken, NJ 07086

4,565,850
 
  
 
6.4
%

Wells Fargo Clearing Services LLC

2801
Market Street

H0006-09B

St. Louis, MO 63103

4,398,787
 
  
 
6.2
%

Bank of New York Mellon

525 William Penn
Place

Suite 153-0400

Pittsburgh, PA 15259

3,857,529
 
  
 
5.4
%

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Class of Shares

Name and Address of Beneficial Owner

Number ofSharesOwned
 
  
Percent ofClass

Pershing LLC

One Pershing Plaza

Jersey City, NJ 07399

3,749,127
 
  
 
5.3
%

Series A Mandatory Redeemable Preferred Shares

Massachusetts Mutual Life Insurance Companyc/o Barings LLC1500 Main Street – Suite 2200P.O. Box 15189Springfield, MA 0115-5189
  
 
1,050,000
 
  
 
78.9

  
Massachusetts Mutual Life Insurance Companyc/o Barings LLC1500 Main Street – Suite 2200P.O. Box 15189Springfield, MA 0115-5189
  
 
280,000
 
  
 
21.1
%

Series B Mandatory Redeemable Preferred Shares

Massachusetts Mutual Life Insurance Companyc/o Barings LLC1500 Main Street – Suite 2200P.O. Box 15189Springfield, MA 0115-5189
  
 
1,050,000
 
  
 
78.9

  
Massachusetts Mutual Life Insurance Companyc/o Barings LLC1500 Main Street – Suite 2200P.O. Box 15189Springfield, MA 0115-5189
  
 
280,000
 
  
 
21.1
%

Series C Mandatory Redeemable Preferred Shares

Massachusetts Mutual Life Insurance Companyc/o Barings LLC1500 Main Street – Suite 2200P.O. Box 15189Springfield, MA 0115-5189
  
 
1,060,000
 
  
 
79.1

  
Massachusetts Mutual Life Insurance Companyc/o Barings LLC1500 Main Street – Suite 2200P.O. Box 15189Springfield, MA 0115-5189
  
 
280,000
 
  
 
20.9
%

At January 31, 2020, the trustees and officers as a group owned less than one percent of the
Fund’s outstanding common shares.

S-42

PORTFOLIO TRANSACTIONS

Portfolio transactions on behalf of the Fund effected on stock exchanges involve the payment of negotiated brokerage commissions. There is
generally no stated commission in the case of securities traded in the over-the-counter markets, but the price paid by the Fund usually includes an undisclosed dealer commission or mark-up. In underwritten offerings, the price paid by the Fund
includes a disclosed, fixed commission or discount retained by the underwriter or dealer.

In executing portfolio transactions,
Calamos seeks to obtain for the Fund the most favorable combination of price and execution available. In seeking the most favorable combination of price and execution, Calamos considers all factors it deems relevant, including price, the size of the
transaction, the nature of the market for the security, the amount of commission, the timing of the transaction taking into account market prices and trends, the execution capability of the broker-dealer and the quality of service rendered by the
broker-dealer in other transactions.

The Trustees have determined that portfolio transactions for the Fund may be executed through CFS,
an affiliate of Calamos, if, in the judgment of Calamos, the use of CFS is likely to result in prices and execution at least as favorable to the Fund as those available from other qualified brokers and if, in such transactions, CFS charges the Fund
commission rates consistent with those charged by CFS to comparable unaffiliated customers in similar transactions. The Board of Trustees, including a majority of the Trustees who are not “interested” trustees, has adopted procedures that
are reasonably designed to provide that any commissions, fees or other remuneration paid to CFS are consistent with the foregoing standard. The Fund will not effect principal transactions with CFS.

In allocating the Fund’s portfolio brokerage transactions to unaffiliated broker-dealers, Calamos may take into consideration the
research, analytical, statistical and other information and services provided by the broker-dealer, such as general economic reports and information, reports or analyses of particular companies or industry groups, market timing and technical
information, and the availability of the brokerage firm’s analysts for consultation. Although Calamos believes these services have substantial value, they are considered supplemental to Calamos’ own efforts in the performance of its duties
under the management agreement.

Calamos does not guarantee any broker the placement of a predetermined amount of securities
transactions in return for the research or brokerage services it provides. Calamos has adopted internal procedures which it believes are reasonably designed to allocate transactions in a manner consistent with its execution policies to brokers that
it has identified as providing research, research-related products or services, or execution-related services of a particular benefit to its clients. Calamos has entered into client commission agreements (“CCAs”) with certain
broker-dealers under which the broker-dealers may use a portion of their commissions to pay third parties or other broker-dealers that provide Calamos with research or brokerage services, as permitted under Section 28(e) of the Exchange Act.
CCAs allow Calamos to direct broker-dealers to pool commissions that are generated from orders executed at that broker-dealer, and then periodically direct the broker-dealer to pay third parties or other broker-dealers for research or brokerage
services. All uses of CCAs by Calamos are subject to applicable law and its best execution obligations. Brokerage and research products and services furnished by brokers may be used in servicing any or all of the clients of Calamos and such research
may not necessarily be used by Calamos in connection with the accounts which paid commissions to the broker providing such brokerage and research products and services.

As permitted by Section 28(e) of the Exchange Act, Calamos may cause the Fund to pay a broker-dealer that provides brokerage and research
services an amount of commission for effecting a securities transaction for the Fund in excess of the commission that another broker-dealer would have charged for effecting that transaction if the amount is believed by Calamos to be reasonable in
relation to the value of the overall quality of the brokerage and research services provided. Other clients of Calamos may indirectly benefit from the provision of these services to Calamos, and the Fund may indirectly benefit from services provided
to Calamos as a result of transactions for other clients.

S-43

The Fund paid $0, $0, and $0 in aggregate brokerage commissions for the fiscal years
ended October 31, 2019-2020, October 31, 2019-2020 and October 31, 2019, including $0, $0, and $0 to CFS, which represented 0%, 0% and 0% of the Fund’s aggregate brokerage fees paid for the respective fiscal year, and 0%, 0%, and 0%
of the Fund’s aggregate dollar amount of transactions involving brokerage commissions for the respective fiscal year.

Portfolio Turnover

Our annual portfolio turnover rate may vary greatly from year to year. Although we cannot accurately predict our annual portfolio
turnover rate, it is not expected to exceed 100% annually under normal circumstances. For the fiscal years ended October 31, 2019-2020 and October 31, 2019, the portfolio turnover rate was 58% and 51%, respectively. However, portfolio
turnover is not considered a limiting factor in the execution of investment decisions for the Fund, and it is possible that the Fund may exceed this level of turnover in any given year. A higher turnover rate results in correspondingly greater
brokerage commissions and other transactional expenses that are borne by the Fund. High portfolio turnover also may result in the realization of capital gains or losses and, to the extent net short-term capital gains are realized, any distributions
resulting from such gains will be taxed at ordinary income tax rates for U.S. federal income tax purposes. See “Certain Federal Income Tax Matters.”

NET ASSET VALUE

Net asset value per share is determined as of the close of regular session trading on the New York Stock Exchange (usually 4:00 p.m., Eastern
time), on the last business day in each week, or such other time as the Fund may determine. Net asset value is calculated by dividing the value of all of the securities and other assets of the Fund, less its liabilities (including accrued expenses
and indebtedness) and the aggregate liquidation value of any outstanding preferred shares, by the total number of common shares outstanding. Currently, the net asset values of shares of publicly traded closed-end investment companies investing in
debt securities are published in Barron’s and periodic publications of The Wall Street Journal.

The valuation of the
Fund’s portfolio securities is in accordance with policies and procedures adopted by and under the ultimate supervision of the Board of Trustees. Securities for which market quotations are readily available will be valued using the market value
of those securities. Securities for which market quotations are not readily available will be fair valued in accordance with policies and procedures adopted by and under the ultimate supervision of the Board of Trustees. The method by which a
security may be fair valued will depend on the type of security and the circumstances under which the security is being fair valued.

Portfolio securities that are traded on U.S. securities exchanges, except option securities, are valued at the last current reported sales
price at the time the Fund determines its NAV. Securities traded in the over-the-counter market and quoted on The Nasdaq Stock Market are valued at the Nasdaq Official Closing Price, as determined by Nasdaq, or lacking a Nasdaq Official Closing
Price, the last current reported sale price on Nasdaq at the time the Fund determines its NAV.

When a last sale or closing price is
not available, equity securities, other than option securities, that are traded on a U.S. securities exchange and other equity securities traded in the over-the-counter market are valued at the mean between the most recent bid and asked quotations
in accordance with guidelines adopted by the Board of Trustees. Each option security traded on a U.S. securities exchange is valued at the mid-point of the consolidated bid/ask quote for the option security, also in accordance with guidelines
adopted by the Board of Trustees. Each over-the-counter option that is not traded through the Options Clearing Corporation is valued based on a quotation provided by the counterparty to such option under the ultimate supervision of the Board of
Trustees.

Fixed income securities are generally traded in the over-the-counter market and are valued based on evaluations provided by
independent pricing services or by dealers who make markets in such securities.

S-44

Valuations of fixed income securities consider yield or price of bonds of comparable quality, coupon rate, maturity, type of issue, trading characteristics and other market data and do not rely
exclusively upon exchange or over-the-counter prices.

Trading on European and Far Eastern exchanges and over-the-counter markets is
typically completed at various times before the close of business on each day on which the NYSE is open. Each security trading on these exchanges or over-the-counter markets may be valued utilizing a systematic fair valuation model provided by an
independent pricing service approved by the Board of Trustees. The valuation of each security that meets certain criteria in relation to the valuation model is systematically adjusted to reflect the impact of movement in the U.S. market after the
foreign markets close. Securities that do not meet the criteria, or that are principally traded in other foreign markets, are valued as of the last reported sale price at the time the Fund determines its NAV, or when reliable market prices or
quotations are not readily available, at the mean between the most recent bid and asked quotations as of the close of the appropriate exchange or other designated time. Trading of foreign securities may not take place on every NYSE business day. In
addition, trading may take place in various foreign markets on Saturdays or on other days when the NYSE is not open and on which the Fund’s NAV is not calculated.

If the pricing committee determines that the valuation of a security in accordance with the methods described above is not reflective of a
market value for such security, the security is valued at a fair value by the pricing committee, under the ultimate supervision of the Board of Trustees, following the guidelines and/or procedures adopted by the Board of Trustees.

The Fund also may use fair value pricing, pursuant to guidelines adopted by the Board of Trustees and under the ultimate supervision of the
Board of Trustees, if trading in the security is halted or if the value of a security it holds is materially affected by events occurring before the Fund’s pricing time but after the close of the primary market or exchange on which the security
is listed. Those procedures may utilize valuations furnished by pricing services approved by the Board of Trustees, which may be based on market transactions for comparable securities and various relationships between securities that are generally
recognized by institutional traders, a computerized matrix system, or appraisals derived from information concerning the securities or similar securities received from recognized dealers in those securities.

When fair value pricing of securities is employed, the prices of securities used by the Fund to calculate its NAV may differ from market
quotations or official closing prices. In light of the judgment involved in fair valuations, there can be no assurance that a fair value assigned to a particular security is accurate.

REPURCHASE OF COMMON SHARES

The Fund is a closed-end investment company and as such its shareholders will not have the right to cause the Fund to redeem their shares.
Instead, the Fund’s common shares trade in the open market at a price that is a function of several factors, including dividend levels (which are in turn affected by expenses), net asset value, call protection, dividend stability, relative
demand for and supply of such shares in the market, general market and economic conditions and other factors. Because shares of a closed-end investment company may frequently trade at prices lower than net asset value, the Fund’s Board of
Trustees may consider action that might be taken to reduce or eliminate any material discount from net asset value in respect of common shares, which may include the repurchase of such shares in the open market or in private transactions, the making
of a tender offer for such shares, or the conversion of the Fund to an open-end investment company. The Board of Trustees may decide not to take any of these actions. In addition, there can be no assurance that share repurchases or tender offers, if
undertaken, will reduce market discount.

Notwithstanding the foregoing, at any time when the Fund’s preferred shares are
outstanding, the Fund may not purchase, redeem or otherwise acquire any of its common shares unless (1) all accumulated preferred shares

S-45

dividends have been paid and (2) at the time of such purchase, redemption or acquisition, the net asset value of the Fund’s portfolio (determined after deducting the acquisition price
of the common shares) is at least 200% of the liquidation value of the outstanding preferred shares (expected to equal the original purchase price per share plus any accrued and unpaid dividends thereon). Any service fees incurred in connection with
any tender offer made by the Fund will be borne by the Fund and will not reduce the stated consideration to be paid to tendering shareholders.

Subject to its investment restrictions, the Fund may borrow to finance the repurchase of shares or to make a tender offer. Interest on any
borrowings to finance share repurchase transactions or the accumulation of cash by the Fund in anticipation of share repurchases or tenders will reduce the Fund’s net income. Any share repurchase, tender offer or borrowing that might be
approved by the Fund’s Board of Trustees would have to comply with the Exchange Act, the 1940 Act and the rules and regulations thereunder.

Although the decision to take action in response to a discount from net asset value will be made by the Board of Trustees at the time it
considers such issue, it is not currently anticipated that the Board of Trustees would authorize repurchases of common shares or a tender offer for such shares if: (1) such transactions, if consummated, would (a) result in the delisting of
the common shares from Nasdaq, or (b) impair the Fund’s status as a regulated investment company under the Code (which would make the Fund a taxable entity, causing the Fund’s income to be taxed at the corporate level in addition to
the taxation of shareholders who receive dividends from the Fund) or as a registered closed-end investment company under the 1940 Act; (2) the Fund would not be able to liquidate portfolio securities in an orderly manner and consistent with the
Fund’s investment objective and policies in order to repurchase shares; or (3) there is, in the board’s judgment, any (a) material legal action or proceeding instituted or threatened challenging such transactions or otherwise
materially adversely affecting the Fund, (b) general suspension of or limitation on prices for trading securities on Nasdaq, (c) declaration of a banking moratorium by federal or state authorities or any suspension of payment by United
States or New York banks, (d) material limitation affecting the Fund or the issuers of its portfolio securities by federal or state authorities on the extension of credit by lending institutions or on the exchange of foreign currency,
(e) commencement of war, armed hostilities or other international or national calamity directly or indirectly involving the United States, or (f) other event or condition which would have a material adverse effect (including any adverse
tax effect) on the Fund or its shareholders if shares were repurchased.

The repurchase by the Fund of its shares at prices below net
asset value will result in an increase in the net asset value of those shares that remain outstanding. However, there can be no assurance that share repurchases or tender offers at or below net asset value will result in the Fund’s shares
trading at a price equal to their net asset value. Nevertheless, the fact that the Fund’s shares may be the subject of repurchase or tender offers from time to time, or that the Fund may be converted to an open-end investment company, may
reduce any spread between market price and net asset value that might otherwise exist.

In addition, a purchase by the Fund of its common
shares will decrease the Fund’s total managed assets which would likely have the effect of increasing the Fund’s expense ratio. Any purchase by the Fund of its common shares at a time when preferred shares are outstanding will increase the
leverage applicable to the outstanding common shares then remaining.

Before deciding whether to take any action if the common shares
trade below net asset value, the Fund’s Board of Trustees would likely consider all relevant factors, including the extent and duration of the discount, the liquidity of the Fund’s portfolio, the impact of any action that might be taken on
the Fund or its shareholders and market considerations. Based on these considerations, even if the Fund’s shares should trade at a discount, the Board of Trustees may determine that, in the interest of the Fund and its shareholders, no action
should be taken.

CERTAIN FEDERAL INCOME TAX MATTERS

The following is a summary discussion of certain U.S. federal income tax consequences that may be relevant to a shareholder or a noteholder
(as the case may be) that acquires, holds and/or disposes of the Fund’s

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securities. This discussion only addresses certain U.S. federal income tax consequences to U.S. shareholders and noteholders (as the case may be) who hold their Fund securities as capital assets
and does not address all of the U.S. federal income tax consequences that may be relevant to particular shareholders and noteholders (as the case may be) in light of their individual circumstances. This discussion also does not address all U.S.
federal, state, local and foreign tax concerns affecting the Fund and its shareholders and noteholders (including shareholders and noteholders subject to special tax rules and shareholders owning large positions in the Fund), and the discussion set
forth herein does not constitute tax advice. The discussion reflects applicable tax laws of the United States as of the date of this Statement of Additional Information, which tax laws may be changed or subject to new interpretations by the courts
or the Internal Revenue Service (“IRS”) retroactively or prospectively. No assurance can be given that the IRS would not assert, or that a court would not sustain, a position different from any of the tax aspects set forth below. The
specific terms of preferred shares and debt securities may result in different tax consequences to holders than those described herein. No attempt is made to present a detailed explanation of all U.S. federal income tax concerns affecting the Fund
and its shareholders and noteholders, and the discussion set forth herein does not constitute tax advice. Investors are urged to consult their own tax advisers to determine the specific tax consequences to them of investing in the Fund,
including the applicable federal, state, local and foreign tax consequences to them and the effect of possible changes in tax laws.

Federal
Income Taxation of the Fund

The Fund has elected to be treated, and intends to qualify and to be eligible to be treated each year,
as a “regulated investment company” under Subchapter M of the Code, so that it will not pay U.S. federal income tax on investment company taxable income and capital gains timely distributed to shareholders. If the Fund qualifies as a
regulated investment company and distributes to its shareholders at least 90% of the sum of (i) its “investment company taxable income” as that term is defined in the Code (which includes, among other things, dividends, taxable
interest, the excess of any net short-term capital gains over net long-term capital losses, taking into account any capital loss carryforwards, and certain net foreign currency exchange gains, less certain deductible expenses) without regard to the
deduction for dividends paid and (ii) the excess of its gross tax-exempt interest, if any, over certain disallowed deductions, the Fund will be relieved of U.S. federal income tax on any income of the Fund, including long-term capital gains,
distributed to shareholders. However, if the Fund retains any investment company taxable income or “net capital gain” (i.e., the excess of net long-term capital gain over the sum of net short-term capital loss and any capital loss
carryforwards), it will be subject to U.S. federal income tax at regular corporate rates on the amount retained. The Fund intends to distribute at least annually, all or substantially all of its investment company taxable income, net tax-exempt
interest, if any, and net capital gain.

In determining its net capital gain, its taxable income, and its earnings and profits, a
regulated investment company generally may elect to treat part or all of any post-October capital loss (defined as any net capital loss attributable to the portion, if any, of the taxable year after October 31 or, if there is no such loss, the
net long-term capital loss or net short-term capital loss attributable to any such portion of the taxable year) or late-year ordinary loss (generally, the sum of (i) net ordinary loss, if any, from the sale, exchange or other taxable
disposition of property, attributable to the portion, if any, of the taxable year after October 31, and its (ii) other net ordinary loss, if any, attributable to the portion of the taxable year, if any, after December 31) as if
incurred in the succeeding taxable year.

Capital losses in excess of capital gains (“net capital losses”) are not permitted to
be deducted against the Fund’s net investment income. Instead, potentially subject to certain limitations, the Fund may carry net capital losses from any taxable year forward to subsequent taxable years without expiration to offset capital
gains, if any, realized during such subsequent taxable years. Capital loss carryforwards are reduced to the extent they offset current-year net realized capital gains, whether the Fund retains or distributes such gains. The Fund must apply such
carryforwards first against gains of the same character.

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If for any taxable year the Fund did not qualify as a regulated investment company for
U.S. federal income tax purposes, it would be treated in the same manner as a regular corporation subject to U.S. federal income tax and distributions to its shareholders would not be deductible by the Fund in computing its taxable income. In such
event, the Fund’s distributions, to the extent derived from the Fund’s current and accumulated earnings and profits, would generally constitute ordinary dividends, which would generally be eligible for the dividends received deduction
available to corporate shareholders under Section 243 of the Code, and noncorporate shareholders of the Fund would generally be able to treat such distributions as “qualified dividend income” eligible for reduced rates of federal
income taxation under Section 1(h)(11) of the Code, as described below. The Fund could be required to recognize unrealized gains, pay substantial taxes and interest and make substantial distributions before re-qualifying as a regulated
investment company that is accorded special tax treatment. If the Fund failed to qualify for a period greater than two taxable years, it would also be required to elect to recognize and pay tax on any net built-in gain (the excess of aggregate gain,
including items of income, over aggregate loss that would have been realized if the Fund had been liquidated) or, alternatively, be subject to taxation on such built-in gain recognized for a period of five years.

Under the Code, the Fund will be subject to a nondeductible 4% federal excise tax on its undistributed ordinary income for a calendar year and
its undistributed capital gains for the one-year period generally ending on October 31 of such calendar year if it fails to meet certain distribution requirements with respect to that year. Generally the excise tax applies to the extent the
Fund fails to distribute by the end of any calendar year at least the sum of (i) 98% of its ordinary income (not taking into account any capital gain or loss) for the calendar year and (ii) 98.2% of its capital gains in excess of its
capital losses (adjusted for certain ordinary losses). In addition, the minimum amounts that must be distributed in any year to avoid the excise tax will be increased or decreased to reflect the total amount of any under-distribution or
over-distribution, as the case may be, from the previous year. For purposes of the required excise tax distribution, a regulated investment company’s ordinary gains and losses from the sale, exchange, or other taxable disposition of property
that would otherwise be taken into account after October 31 generally are treated as arising on January 1 of the following calendar year. Also, for purposes of the excise tax, the Fund will be treated as having distributed any amount on
which it is subject to corporate income tax for the taxable year ending within the calendar year. The Fund intends to generally make distributions in a timely manner and in an amount sufficient to avoid such tax and accordingly does not expect to be
subject to this excise tax.

In order to qualify as a regulated investment company under Subchapter M of the Code, the Fund must,
among other things, derive at least 90% of its gross income for each taxable year from (i) dividends, interest, payments with respect to securities loans, gains from the sale or other disposition of stock, securities or foreign currencies, or
other income (including gains from options, futures and forward contracts) derived with respect to its business of investing in such stock, securities or currencies and (ii) net income derived from interests in certain publicly traded
partnerships that derive less than 90% of their gross income from the items described in (i) above (each, a “Qualified Publicly Traded Partnership”) (the “90% income test”). For purposes of the 90% income test, the character
of income earned by certain entities in which the Fund invests that are not treated as corporations for U.S. federal income tax purposes will generally pass through to the Fund. Consequently, the Fund may be required to limit its equity investments
in certain such entities.

In addition to the 90% income test, the Fund must also diversify its holdings (the “asset test”)
so that, at the end of each quarter of its taxable year (i) at least 50% of the market value of the Fund’s total assets is represented by cash and cash items, U.S. government securities, securities of other regulated investment companies
and other securities, with such other securities of any one issuer limited for the purposes of this calculation to an amount not greater in value than 5% of the value of the Fund’s total assets and to not more than 10% of the outstanding voting
securities of such issuer, and (ii) not more than 25% of the market value of its total assets is invested, including through corporations in which the Fund owns a 20% or more voting stock interest, in the securities (other than U.S. government
securities or securities of other regulated investment companies) of any one issuer or of two or more issuers controlled by the Fund and engaged in the same, similar or related trades or businesses or in the securities of one or more Qualified
Publicly Traded Partnerships.

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Foreign exchange gains and losses realized by the Fund in connection with certain
transactions involving foreign currency-denominated debt securities, certain options and futures contracts relating to foreign currency, foreign currency forward contracts, foreign currencies, or payables or receivables denominated in a foreign
currency are subject to Section 988 of the Code, which generally causes such gains and losses to be treated as ordinary income and losses and may affect the amount, timing and character of distributions to shareholders.

If the Fund acquires any equity interest (generally including not only stock but also an option to acquire stock such as is inherent in a
convertible bond) in certain foreign corporations that receive at least 75% of their annual gross income from passive sources (such as interest, dividends, certain rents and royalties, or capital gains) or that hold at least 50% of their assets in
investments held for the production of such passive income (“passive foreign investment companies”), the Fund could be subject to U.S. federal income tax and additional interest charges on “excess distributions” received from
such companies or on gain from the sale of equity interests in such companies, even if all income or gain actually received by the Fund is timely distributed to its shareholders. These investments could also result in the treatment as ordinary
income of associated gains on a sale of the investment. The Fund would not be able to pass through to its shareholders any credit or deduction for such tax. Tax elections may generally be available that would ameliorate these adverse tax
consequences, but any such election could require the Fund to recognize taxable income or gain (which would be subject to the distribution requirements described above) without the concurrent receipt of cash. The Fund may limit and/or manage its
holdings in passive foreign investment companies to limit its U.S. federal income tax liability or maximize its return from these investments.

If the Fund invests in certain pay-in-kind securities, zero coupon securities, deferred interest securities or, in general, any other
securities with original issue discount (“OID”) (or with market discount if the Fund elects to include market discount in income currently), the Fund must accrue income on such investments for each taxable year, which generally will be
prior to the receipt of the corresponding cash payments. However, the Fund must distribute, at least annually, all or substantially all of its investment company taxable income, including such accrued income, to shareholders to avoid U.S. federal
income and excise taxes. Therefore, the Fund may have to dispose of its portfolio securities under disadvantageous circumstances to generate cash, or may have to leverage itself by borrowing the cash, to satisfy distribution requirements.

The Fund may acquire market discount bonds. A market discount bond is a security acquired in the secondary market at a price below its stated
redemption price at maturity (or its adjusted issue price if it is also an OID bond). If the Fund invests in a market discount bond, it will be required to treat any gain recognized on the disposition of such market discount bond as ordinary income
(instead of capital gain) to the extent of the accrued market discount, unless the Fund elects to include the market discount in income as it accrues as discussed above. Such market discount will not constitute qualified dividend income.

The Fund may invest to a significant extent in debt obligations that are in the lowest rating categories or are unrated, including debt
obligations of issuers not currently paying interest or who are in default. Investments in debt obligations that are at risk of or in default present special tax issues for the Fund. The U.S. federal income tax laws are not entirely clear about
issues such as when the Fund may cease to accrue interest, OID or market discount, when and to what extent deductions may be taken for bad debts or worthless securities and how payments received on obligations in default should be allocated between
principal and income. These and other related issues will be addressed by the Fund when, as and if it invests in such securities, in order to ensure that it distributes sufficient income to preserve its status as a regulated investment company and
does not become subject to U.S. federal income or excise taxes.

Very generally, where the Fund purchases a bond at a price that
exceeds the stated redemption price at maturity — that is, at a premium — the premium is amortizable over the remaining term of the bond. In the case of a taxable bond, if the Fund makes an election applicable to all such bonds it
purchases, which election is irrevocable without consent of the IRS, the Fund reduces the current taxable income from the bond by the amortized premium and reduces its tax basis in the bond by the amount of such offset; upon the disposition or

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maturity of such bonds, the Fund is permitted to deduct any remaining premium allocable to a prior period. In the case of a tax-exempt bond, tax rules require the Fund to reduce its tax basis by
the amount of amortized premium.

The interest on municipal bonds is generally exempt from U.S. federal income tax. The Fund does not
expect to invest 50% or more of its assets in municipal bonds on which the interest is exempt from U.S. federal income tax, or in interests in other regulated investment companies. As a result, it does not expect to be eligible to pay
“exempt-interest dividends” to its shareholders under the applicable tax rules. As a result, interest on municipal bonds is taxable to shareholders of the Fund when received as a distribution from the Fund. In addition, gains realized by
the Fund on the sale or exchange of municipal bonds are taxable to shareholders of the Fund when distributed to them.

Certain of the
Fund’s other investments may cause the Fund to recognize income without the corresponding receipt of cash, which could result in the Fund being required to dispose of its portfolio securities under disadvantageous circumstances to generate cash
or leverage itself by borrowing cash to satisfy distribution requirements and to avoid entity-level tax.

The Fund may engage in various
transactions in options, futures contracts, forward contracts, hedging instruments, straddles, swaps and other similar transactions. In addition to the special rules described below, such transactions may be subject to special provisions of the Code
that, among other things, affect the character of any income realized by the Fund from such investments, accelerate recognition of income to the Fund, defer Fund losses, affect the holding period of the Fund’s securities, affect whether
distributions will be eligible for the dividends received deduction or be treated as qualified dividend income and affect the determination of whether capital gain and loss is characterized as long-term or short-term capital gain or loss. These
rules could therefore affect the character, amount and timing of distributions to shareholders. These provisions may also require the Fund to “mark-to-market” certain types of the positions in its portfolio (i.e., treat them as if they
were closed out), which may cause the Fund to recognize income without receiving cash with which to make distributions in amounts necessary to satisfy the distribution requirements for avoiding U.S. federal income and excise taxes. Because these and
other tax rules applicable to these types of transactions are in some cases uncertain under current law, an adverse determination or future guidance by the IRS with respect to these rules (which determination or guidance could be retroactive) may
affect whether the Fund has made sufficient distributions, and otherwise satisfied the relevant requirements, to maintain its qualification as a regulated investment company and avoid a Fund-level tax. The Fund will monitor its transactions and will
make the appropriate entries in its books and records when it acquires an option, futures contract, forward contract, hedge instrument, swap or other similar investment, and if the Fund deems it advisable, will make appropriate elections in order to
mitigate the effect of these rules, prevent disqualification of the Fund as a regulated investment company and minimize the imposition of U.S. federal income and excise taxes.

Certain of the Fund’s investments in derivative instruments and foreign currency denominated instruments, and any of the Fund’s
transactions in foreign currencies and hedging activities, are likely to produce a difference between its book income and the sum of its taxable income (including realized capital gains) and net tax-exempt income (if any). If such a difference
arises and the Fund’s book income is less than the sum of its taxable income (including realized capital gains) and net tax-exempt income (if any), the Fund could be required to make distributions exceeding book income to qualify as a regulated
investment company that is accorded special tax treatment and to avoid a Fund-level tax. If the Fund’s book income exceeds the sum of its taxable income (including realized capital gains) and net tax-exempt income (if any), the distribution (if
any) of such excess generally will be treated as (i) a dividend to the extent of the Fund’s remaining current and accumulated earnings and profits (including earnings and profits arising from tax-exempt income), if any,
(ii) thereafter, as a return of capital to the extent of the recipient’s adjusted tax basis in its shares, and (iii) thereafter, as gain from the sale or exchange of a capital asset.

In general, option premiums received by the Fund are not immediately included in the income of the Fund. Instead, the premiums are recognized
when the option contract expires, the option is exercised by the holder, or

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the Fund transfers or otherwise terminates the option (e.g., through a closing transaction). If a call option written by the Fund is exercised and the Fund sells or delivers the underlying stock,
the Fund generally will recognize capital gain or loss equal to (a) the sum of the strike price and the option premium received by the Fund minus (b) the Fund’s basis in the stock. Such gain or loss generally will be short-term or
long-term depending upon the holding period of the underlying stock. If securities are purchased by the Fund pursuant to the exercise of a put option written by it, the Fund generally will subtract the premium received for purposes of computing its
cost basis in the securities purchased. The termination of the Fund’s obligation under an option other than through the exercise of the option will result in gain or loss, depending on whether the premium income received by the Fund is greater
or less than the amount paid by the Fund (if any) in terminating the transaction. Subject to certain exceptions, some of which are described below, such gain or loss generally will be short-term. Thus, for example, if an option written by the Fund
expires unexercised, the Fund generally will recognize short-term gain equal to the premium received.

The Fund’s options
activities may include transactions constituting straddles for U.S. federal income tax purposes, that is, that trigger the U.S. federal income tax straddle rules contained primarily in Section 1092 of the Code. Such straddles include, for
example, positions in a particular security, or an index of securities, and one or more options that offset the former position, including options that are “covered” by the Fund’s long position in the subject security. Very generally,
where applicable, Section 1092 requires (i) that losses be deferred on positions deemed to be offsetting positions with respect to “substantially similar or related property,” to the extent of unrealized gain in the latter, and
(ii) that the holding period of such a straddle position that has not already been held for the long-term holding period be terminated and begin anew once the position is no longer part of a straddle. Options on single stocks that are not
“deep in the money” may constitute qualified covered calls, which generally are not subject to the straddle rules; the holding period on stock underlying qualified covered calls that are “in the money” although not “deep in
the money” will be suspended during the period that such calls are outstanding. These straddle rules and the rules governing qualified covered calls could cause gains that would otherwise constitute long-term capital gains to be treated as
short-term capital gains, and distributions that would otherwise constitute “qualified dividend income” or qualify for the dividends received deduction to fail to satisfy the holding period requirements and therefore to be taxed as
ordinary income or to fail to qualify for the dividends received deduction, as the case may be.

The Fund’s transactions in certain
investments (including broad based equity index options and certain other futures contracts) are generally considered “Section 1256 contracts” for federal income tax purposes. Any unrealized gains or losses on such Section 1256
contracts are treated as though they were realized at the end of each taxable year. The resulting gain or loss is treated as sixty percent long-term capital gain or loss and forty percent short-term capital gain or loss. Gain or loss recognized on
actual sales of Section 1256 contracts is treated in the same manner. As noted below, distributions of net short-term capital gain are taxable to shareholders as ordinary income while distributions of net long-term capital gain that are
properly reported as capital gain dividends are taxable to shareholders as long-term capital gain, regardless of how long the shareholder has held shares of the Fund.

The Fund’s entry into a short sale transaction, an option or certain other contracts could be treated as the constructive sale of an
appreciated financial position, causing the Fund to realize gain, but not loss, on the position.

Any investment by the Fund in equity
securities of REITs may result in the Fund’s receipt of cash in excess of the REIT’s earnings; if the Fund distributes these amounts, these distributions could constitute a return of capital to Fund shareholders for U.S. federal income tax
purposes. Dividends received by the Fund from a REIT will not qualify for the corporate dividends-received deduction and generally will not constitute qualified dividend income. The Fund may invest in REITs that hold residual interests in real
estate mortgage investment conduits (“REMICs”). Under a notice issued by the IRS, a portion of the Fund’s income from a REIT that is attributable to the REIT’s residual interest in a REMIC (referred to in the Code as an
“excess inclusion”) will be subject to U.S. federal income tax in all events. This notice also provides that excess inclusion income of a

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regulated investment company, such as the Fund, will be allocated to shareholders of the regulated investment company in proportion to the dividends received by such shareholders, with the same
consequences as if the shareholders held the related REMIC residual interest directly. In general, excess inclusion income allocated to shareholders (i) cannot be offset by net operating losses (subject to a limited exception for certain thrift
institutions), (ii) will constitute unrelated business taxable income (“UBTI”) to entities (including a qualified pension plan, an individual retirement account, a 401(k) plan, a Keogh plan or other tax-exempt entity) subject to
federal income tax on unrelated business income, thereby potentially requiring such an entity that is allocated excess inclusion income, and otherwise might not be required to file a federal income tax return, to file a tax return and pay tax on
such income, and (iii) in the case of a foreign shareholder, will not qualify for any reduction in U.S. federal withholding tax. In addition, special tax consequences apply to charitable remainder trusts (“CRTs”) that invest in
regulated investment companies that invest directly or indirectly in residual interests in REMICs. Under legislation enacted in December 2006, a CRT, as defined in Section 664 of the Code, that realizes any UBTI for a taxable year, must pay an
excise tax annually of an amount equal to such UBTI. Under IRS guidance issued in 2006, a CRT will not recognize UBTI solely as a result of investing in a regulated investment company that recognizes “excess inclusion income.” Rather, if
at any time during any taxable year a CRT (or one of certain other tax-exempt shareholders, such as the United States, a state or political subdivision, or an agency or instrumentality thereof, and certain energy cooperatives) is a record holder of
a share in a regulated investment company that recognizes “excess inclusion income,” then the regulated investment company will be subject to a tax on that portion of its “excess inclusion income” for the taxable year that is
allocable to such shareholders at the highest federal corporate income tax rate. The extent to which this IRS guidance remains applicable in light of the December 2006 legislation is unclear. To the extent permitted under the 1940 Act, the Fund may
elect to specially allocate any such tax to the applicable CRT, or other shareholder, and thus reduce such shareholder’s distributions for the year by the amount of the tax that relates to such shareholder’s interest in the Fund. The Fund
has not yet determined whether such an election will be made. CRTs and other tax-exempt shareholders are urged to consult their tax advisers concerning the consequences of investing in the Fund. The Fund does not intend to invest in REITs in which a
substantial portion of the assets will consist of residual interests in REMICs.

The Fund may be subject to withholding and other taxes
imposed by foreign countries, including taxes on interest, dividends and capital gains with respect to its investments in those countries, which would, if imposed, reduce the yield on or return from those investments. If more than 50% of the value
of the Fund’s assets at the close of the taxable year consists of stock or securities of foreign corporations, the Fund may make an election under the Code to pass through such taxes to shareholders of the Fund. If the Fund is eligible to and
makes such an election, shareholders will generally be able (subject to applicable limitations under the Code) to claim a credit or deduction (but not both) on their federal income tax return for, and will be required to treat as part of the amounts
distributed to them, their pro rata portion of the income taxes paid by the Fund to foreign countries. If the Fund makes such an election, it will provide relevant information to its shareholders. If such an election is not made, shareholders will
not be required to include such taxes in their gross incomes and will not be entitled to a tax deduction or credit for such taxes on their own federal income tax returns. Each prospective investor is urged to consult its tax adviser regarding
taxation of foreign securities in the Fund’s portfolio and any available foreign tax credits with respect to the prospective investor’s own situation.

Common Shares and Preferred Shares

Common Share Distributions. Unless a shareholder is ineligible to participate or elects otherwise, all distributions on common shares
will be automatically reinvested in additional common shares of the Fund pursuant to the Automatic Dividend Reinvestment Plan (the “Dividend Reinvestment Plan”). For U.S. federal income tax purposes, dividends are generally taxable whether
a shareholder takes them in cash or they are reinvested pursuant to the Dividend Reinvestment Plan in additional shares of the Fund.

Distributions of investment company taxable income (determined without regard to the deduction for dividends paid), which includes dividends,
taxable interest, net short-term capital gain in excess of net long-term

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capital loss, taking into account any capital loss carryforwards and certain net foreign currency exchange gains, are, except as discussed below, taxable as ordinary income to the extent of the
Fund’s current and accumulated earnings and profits. A portion of such dividends may qualify for the dividends received deduction available to corporations under Section 243 of the Code and the reduced rate of taxation under
Section 1(h)(11) of the Code that applies to qualified dividend income received by noncorporate shareholders. In general, dividends of net investment income received by corporate shareholders of the Fund qualify for the dividends received
deduction generally available to corporations only to the extent of the amount of eligible dividends received by the Fund from domestic corporations (other than REITs) for the taxable year. Qualified dividend income received by noncorporate
shareholders is taxed at rates equivalent to long-term capital gain tax rates. Qualified dividend income generally includes dividends from domestic corporations and dividends from foreign corporations that meet certain specified criteria, although
dividends paid by REITs will not generally be eligible for treatment as qualified dividend income. The Fund generally can pass the tax treatment of dividends eligible for the dividends received deduction and qualified dividend income it receives
through to Fund shareholders. For the Fund to receive tax-advantaged dividend income, the Fund must meet certain holding period requirements with respect to the stock on which the dividend is paid. In addition, the Fund cannot be obligated to make
payments (pursuant to a short sale or otherwise) with respect to substantially similar or related property. Similar provisions, including holding period requirements, apply to each shareholder’s investment in the Fund. Moreover, the dividends
received deduction may otherwise be disallowed or reduced by application of various provisions of the Code (for instance, the dividends received deduction is reduced in the case of a dividend received on debt-financed portfolio stock (generally,
stock acquired with borrowed funds)).

Distributions of net capital gain, if any, that are properly reported as capital gain
dividends are generally taxable as long-term capital gains for U.S. federal income tax purposes without regard to the length of time the shareholder has held shares of the Fund. A distribution of an amount in excess of the Fund’s current and
accumulated earnings and profits, if any, will be treated by a shareholder as a tax-free return of capital which is applied against and reduces the shareholder’s basis in his or her shares. Such distributions represent a return of the
investor’s capital to the extent of his or her basis in the shares. To the extent that the amount of any such distribution exceeds the shareholder’s basis in his or her shares, the excess will be treated by the shareholder as gain from the
sale or exchange of shares. The U.S. federal income tax status of all distributions will be reported to the shareholders annually.

Pursuant to proposed regulations on which the Fund may rely, distributions by the Fund to its shareholders that the Fund properly reports as
“section 199A dividends,” as defined and subject to certain conditions described below, are treated as qualified REIT dividends in the hands of non-corporate shareholders. Non-corporate shareholders are permitted a federal income tax
deduction equal to 20% of qualified REIT dividends received by them, subject to certain limitations. Very generally, a “section 199A dividend” is any dividend or portion thereof that is attributable to certain dividends received by a
regulated investment company from REITs, to the extent such dividends are properly reported as such by the regulated investment company in a written notice to its shareholders. A section 199A dividend is treated as a qualified REIT dividend only if
the shareholder receiving such dividend holds the dividend-paying regulated investment company shares for at least 46 days of the 91-day period beginning 45 days before the shares become ex-dividend, and is not under an obligation to make related
payments with respect to a position in substantially similar or related property. The Fund is permitted to report such part of its dividends as section 199A dividends as are eligible, but is not required to do so.

If the Fund retains any net capital gain, the Fund may report the retained amount as undistributed capital gains to shareholders who, if
subject to U.S. federal income tax on long-term capital gains, (i) will be required to include in income, as long-term capital gain, their proportionate share of such undistributed amount, and (ii) will be entitled to credit their
proportionate share of the federal income tax paid by the Fund on the undistributed amount against their U.S. federal income tax liabilities, if any, and to claim refunds to the extent the credit exceeds such liabilities. For U.S. federal income tax
purposes, the tax basis of shares owned by a shareholder of the Fund will be increased by the difference between the amount of undistributed net capital gain included in the shareholder’s gross income and the federal income tax deemed paid by
the shareholder.

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If a shareholder’s distributions are automatically reinvested pursuant to the Dividend
Reinvestment Plan and the plan agent invests the distribution in shares acquired on behalf of the shareholder in open-market purchases, for U.S. federal income tax purposes, the shareholder will be treated as having received a taxable distribution
in the amount of the cash dividend that the shareholder would have received if the shareholder had elected to receive cash. If a shareholder’s distributions are automatically reinvested pursuant to the Dividend Reinvestment Plan and the plan
agent invests the distribution in newly issued shares of the Fund, the shareholder will generally be treated as receiving a taxable distribution equal to the fair market value of the shares the shareholder receives.

At the time of an investor’s purchase of the Fund’s shares, a portion of the purchase price may be attributable to unrealized
appreciation in the Fund’s portfolio or undistributed taxable income of the Fund. Consequently, subsequent distributions by the Fund with respect to these shares from such appreciation or income may be taxable to such investor even if the net
asset value of the investor’s shares is, as a result of the distributions, reduced below the investor’s cost for such shares and the distributions economically represent a return of a portion of the investment.

Any dividend declared by the Fund in October, November or December with a record date in such a month and paid during the following January
will be treated for U.S. federal income tax purposes as paid by the Fund and received by shareholders on December 31 of the calendar year in which it is declared.

Preferred Share Distributions. Under present law and based in part on the fact that there is and will be no express or implied
agreement between or among a broker-dealer or any other party, and the Fund or any owners of preferred shares, that the broker-dealer or any other party will guarantee or otherwise arrange to ensure that an owner of preferred shares will be able to
sell his or her shares, the Fund has treated, and intends to continue to treat, the preferred shares as equity for federal income tax purposes. As such, distributions with respect to the preferred shares (other than distributions in redemption of
the preferred shares subject to Section 302(b) of the Code) will generally constitute dividends to the extent of the Fund’s current and accumulated earnings and profits, as calculated for U.S. federal income tax purposes. Except in the
case of net capital gain distributions, such dividends generally will be taxable at ordinary income tax rates to holders of preferred shares but may qualify for the dividends received deduction available to corporate shareholders under
Section 243 of the Code and the reduced rates of federal income taxation that apply to qualified dividend income received by noncorporate shareholders under Section 1(h)(11) of the Code. Distributions reported by the Fund as net capital
gain distributions will be taxable as long-term capital gain regardless of the length of time a shareholder has held shares of the Fund. Please see the discussion above on qualified dividend income, dividends received deductions and net capital
gain.

The character of the Fund’s income will not affect the amount of dividends which the holders of preferred shares are
entitled to receive. If the preferred shares are auction rate securities, holders of preferred shares are entitled to receive only the amount of dividends as determined by periodic auctions. For U.S. federal income tax purposes, the IRS requires
that a regulated investment company that has two or more classes of shares allocate to each such class proportionate amounts of each type of its income (such as ordinary income and net capital gain) for each tax year. Accordingly, the Fund intends
to report distributions made with respect to the common shares and preferred shares as consisting of particular types of income (e.g., net capital gain and ordinary income), in accordance with each class’s proportionate share of the total
dividends paid to both classes. Thus, each year the Fund will report dividends qualifying for the corporate dividends received deduction, qualified dividend income, ordinary income and net capital gains in a manner that allocates such income between
the preferred shares and common shares in proportion to the total dividends made to each class with respect to such taxable year, or otherwise as required by applicable law. In addition, solely for the purpose of satisfying the 90% distribution
requirement and the distribution requirement for avoiding income taxes, certain distributions made after the close of a taxable year of the Fund may be “spilled back” and treated as paid during such taxable year. In such case, shareholders
will be treated as having received such dividends in the taxable year in which the distribution was actually made. The Fund intends to treat any dividends that are paid following the close of a taxable year as “paid” in the prior year for
purposes of determining a class’s proportionate share of a particular type of income.

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The IRS has ruled privately that dividends paid following the close of the taxable year that are treated for federal income tax purposes as derived from income from the prior year will be treated
as dividends “paid” in the prior year for purposes of determining the proportionate share of a particular type of income for each class. The private ruling is not binding on the IRS, and there can be no assurance that the IRS will respect
such treatment. Each shareholder will be notified of the allocation within 60 days after the end of the year.

Although the Fund is
required to distribute annually at least 90% of its investment company taxable income (determined without regard to the deduction for dividends paid), the Fund is not required to distribute net capital gains to the shareholders. The Fund may retain
and reinvest such gains and pay federal income taxes on such gains (the “net undistributed capital gain”). Please see the discussion above on undistributed capital gains. The Fund intends to distribute its net capital gain for any year
during which it has preferred shares outstanding.

Although dividends generally will be treated as distributed when paid, dividends
declared in October, November or December with a record date in such a month, and paid in January of the following year, will be treated as having been distributed by the Fund and received by the shareholders on December 31 of the year in which
the dividend was declared.

Earnings and profits are generally treated, for federal income tax purposes, as first being used to pay
distributions on preferred shares, and then to the extent remaining, if any, to pay distributions on the common shares. Distributions in excess of current and accumulated earnings and profits of the Fund are treated first as return of capital to the
extent of the shareholder’s basis in the shares and, after the adjusted basis is reduced to zero, will be treated as capital gain to a shareholder who holds such shares as a capital asset.

If the Fund utilizes leverage through borrowings, or otherwise, asset coverage limitations imposed by the 1940 Act as well as additional
restrictions that may be imposed by certain lenders on the payment of dividends or distributions potentially could limit or eliminate the Fund’s ability to make distributions on its common shares and/or preferred shares until the asset coverage
is restored. These limitations could prevent the Fund from distributing at least 90% of its investment company taxable income as is required under the Code and therefore might jeopardize the Fund’s qualification as a regulated investment
company and/or might subject the Fund to a nondeductible 4% federal excise tax. Upon any failure to meet the asset coverage requirements imposed by the 1940 Act, the Fund may, in its sole discretion and to the extent permitted under the 1940 Act,
purchase or redeem preferred shares in order to maintain or restore the requisite asset coverage and avoid the adverse consequences to the Fund and its shareholders of failing to meet the distribution requirements. There can be no assurance,
however, that any such action would achieve these objectives. The Fund will endeavor to avoid restrictions on its ability to distribute dividends.

Sales of Fund Shares. Sales and other dispositions of the Fund’s shares, including a repurchase by the Fund of its shares,
generally are taxable events for shareholders that are subject to federal income tax. Selling shareholders will generally recognize gain or loss in an amount equal to the difference between the amount received for such shares and their adjusted tax
basis in the shares sold. If such shares are held as a capital asset at the time of sale, the gain or loss will generally be a long-term capital gain or loss if the shares have been held for more than one year, and, if not held for such period, a
short-term capital gain or loss. Similarly, a repurchase by the Fund, including as a result of a tender offer by the Fund, if any, of all of the shares (common and preferred) actually and constructively held by a shareholder generally will give rise
to capital gain or loss under Section 302(b) of the Code if the shareholder does not own (and is not regarded under certain federal income tax law rules of constructive ownership as owning) any other common or preferred shares of the Fund and
provided that the proceeds from the purchase do not represent declared but unpaid dividends. If the Fund repurchases fewer than all of a shareholder’s common shares or a shareholder continues to hold (directly or by attribution) other Fund
shares (including preferred shares if then outstanding) subsequent to a Fund repurchase, in certain circumstances such shareholder may be treated as having received a distribution under Section 301 of the Code (“Section 301
distribution”) unless the repurchase is treated as being either (i) “substantially disproportionate” with respect to such shareholder or (ii) otherwise “not essentially equivalent to a dividend” under the relevant

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rules of the Code. A Section 301 distribution is not treated as a sale or exchange giving rise to capital gain or loss, but rather is treated as a dividend to the extent supported by the
Fund’s current and accumulated earnings and profits, with the excess treated as a return of capital reducing the shareholder’s tax basis in its Fund shares, and thereafter as capital gain. Where a selling shareholder is treated as
receiving a dividend, there is a risk that non-selling shareholders whose percentage interests in the Fund increase as a result of such repurchase will be treated as having received a taxable distribution from the Fund. The extent of such risk will
vary depending upon the particular circumstances of the repurchase, in particular whether such repurchase is a single and isolated event or is part of a plan for periodically repurchasing the common shares of the Fund; if isolated, any such risk is
likely remote.

Gain or loss will generally be long-term capital gain or loss if the shares disposed of were held for more than one year
and will be short-term capital gain or loss if the shares disposed of were held for one year or less. Net long-term capital gain recognized by a noncorporate U.S. shareholder generally will be subject to federal income tax at a lower rate than net
short-term capital gain or ordinary income. For corporate holders, capital gain is generally taxed for federal income tax purposes at the same rate as ordinary income. A holder’s ability to deduct capital losses may be limited.

Any loss realized by a shareholder upon the sale or other disposition of shares with a tax holding period of six months or less will be
treated as a long-term capital loss to the extent of any amounts treated as distributions of long-term capital gain with respect to such shares. Losses on sales or other dispositions of shares may be disallowed under “wash sale” rules in
the event a shareholder acquires, or is treated as acquiring, substantially identical stock or securities (including Fund shares acquired pursuant to the reinvestment of dividends) within a period of 61 days beginning 30 days before and
ending 30 days after a sale or other disposition of shares. In such a case, the disallowed portion of any loss generally would be included in the U.S. federal income tax basis of the shares acquired. Shareholders should consult their own tax
advisers regarding their individual circumstances to determine whether any particular transaction in the Fund’s shares is properly treated as a sale for U.S. federal income tax purposes and the tax treatment of any gains or losses recognized in
such transactions.

Upon the dissolution of the Fund, shareholders generally will realize capital gain or loss in an amount equal to
the difference between the amount of cash or other property received by the shareholder (including any property deemed received by reason of its being placed in a liquidating trust) and the shareholder’s adjusted tax basis in shares of the Fund
for U.S. federal income tax purposes. Any such gain or loss will be long-term if the shareholder is treated as having a holding period in Fund shares of greater than one year, and otherwise will be short-term.

Federal Income Tax Withholding. Federal law requires that the Fund withhold, as “backup withholding,” a percentage of
reportable payments, including dividends, capital gain distributions and the proceeds of sales or other dispositions of the Fund’s shares paid to shareholders who have not complied with IRS regulations. In order to avoid this withholding
requirement, shareholders must certify on their account applications, or on a separate IRS Form W-9, that the social security number or other taxpayer identification number they provide is their correct number and that they are not currently subject
to backup withholding, or that they are exempt from backup withholding. The Fund may nevertheless be required to backup withhold if it receives notice from the IRS or a broker that the number provided is incorrect or backup withholding is
applicable. Backup withholding is not an additional tax. Any amounts withheld from payments made to a shareholder may be refunded or credited against such shareholder’s U.S. federal income tax liability, if any, provided that the required
information is furnished to the IRS.

Other Matters. Treasury regulations provide that if a shareholder recognizes a loss with
respect to shares of $2 million or more in a single taxable year (or $4 million or more in any combination of taxable years in which the transaction is entered into and the five succeeding taxable years) for a shareholder who is an
individual, S corporation or trust or $10 million or more for a corporate shareholder in any single taxable year (or $20 million or more in any combination of taxable years in which the transaction is entered into and the five succeeding

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taxable years), the shareholder must file with the IRS a disclosure statement on Form 8886. Direct shareholders of portfolio securities are in many cases excepted from this reporting requirement,
but under current guidance, shareholders of a regulated investment company are not excepted. Future guidance may extend the current exception from this reporting requirement to shareholders of most or all regulated investment companies. The fact
that a loss is reportable under these regulations does not affect the legal determination of whether the taxpayer’s treatment of the loss is proper. Shareholders should consult their tax advisers to determine the applicability of these
regulations in light of their individual circumstances.

Special tax rules apply to investments through defined contribution plans
and other tax-qualified plans. Shareholders should consult their tax advisers to determine the suitability of shares of the Fund as an investment through such plans and the precise effect of an investment on their particular tax situation.

Taxation of Non-U.S. Shareholders. The description of certain federal income tax provisions above relates only to U.S. federal
income tax consequences for shareholders who are U.S. persons (i.e., U.S. citizens or resident aliens or U.S. corporations, partnerships, trusts or estates who are subject to U.S. federal income tax on a net income basis). Investors other than U.S.
persons, including non-resident alien individuals, may be subject to different U.S. federal income tax treatment. With respect to such persons, the Fund must generally withhold U.S. federal withholding tax at the rate of 30% (or, if the Fund
receives certain certifications from such non-U.S. shareholder, such lower rate as prescribed by an applicable tax treaty) on amounts treated as ordinary dividends from the Fund. However, the Fund is not required to withhold tax on any amounts paid
to a non-U.S. person with respect to capital gain dividends (that is, distributions of net capital gain that are properly reported by the Fund as capital gain dividends), dividends attributable to “qualified short-term gain”
(i.e., the excess of net short-term capital gain over net long-term capital loss) reported as such by the Fund and dividends attributable to certain U.S. source interest income of types similar to those not subject to federal withholding tax if
earned directly by a non-U.S. person, provided such amounts are properly reported by the Fund. Shareholders should consult their own tax advisers on these matters and on any specific question of U.S. federal, state, local, foreign and other
applicable tax laws before making an investment in the Fund.

Debt Securities

Under present law, the Fund intends to treat the debt securities as indebtedness for federal income tax purposes, which treatment the
discussion below assumes. We intend to treat all payments made with respect to the debt securities consistent with this characterization. The following discussion assumes that all interest on the debt securities will be qualified stated interest
(which is generally interest that is unconditionally payable at least annually at a fixed or qualified floating rate), and that the debt securities will have a fixed maturity date of more than one year from the date of issuance.

Taxation of Interest. Payments or accruals of interest on debt securities generally will be taxable to holders as ordinary interest
income at the time such interest is received (actually or constructively) or accrued, in accordance with the holder’s regular method of accounting for federal income tax purposes.

Purchase, Sale and Redemption of Debt Securities. Initially, a holder’s tax basis in debt securities acquired generally will be
equal to the cost to acquire such debt securities. This basis will be increased by the amounts, if any, that the holder includes in income under the rules governing OID (taking into account any acquisition premium that offsets such OID) and market
discount, and will be decreased by the amount of any amortized premium on such debt securities, as discussed below, and any payments on such debt securities other than stated interest. When the holder sells, exchanges or redeems any of its debt
securities, or otherwise disposes of its debt securities in a taxable transaction, the holder generally will recognize gain or loss equal to the difference between the amount realized on the transaction (less any accrued and unpaid interest
(including any OID), which will be subject to federal income tax as interest in the manner described above) and the tax basis in the debt securities relinquished.

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Except as discussed below with respect to market discount, the gain or loss recognized on
the sale, exchange, redemption or other taxable disposition of any debt securities generally will be capital gain or loss. Such gain or loss will generally be long-term capital gain or loss if the disposed debt securities were held for more than one
year and will be short-term capital gain or loss if the disposed debt securities were held for one year or less. Net long-term capital gain recognized by a noncorporate U.S. holder generally will be subject to federal income tax at a lower rate than
net short-term capital gain or ordinary income. For corporate holders, capital gain is generally taxed for federal income tax purposes at the same rate as ordinary income. A holder’s ability to deduct capital losses may be limited.

Amortizable Premium. If a holder purchases debt securities at a cost greater than their stated redemption price at maturity, plus
accrued interest, the holder will be considered to have purchased the debt securities at a premium, and generally may elect to amortize this premium as an offset to interest income, using a constant yield method, over the remaining term of the debt
securities. If the holder makes the election to amortize the premium, it generally will apply to all debt instruments held at the beginning of the first taxable year to which the election applies, as well as any debt instruments that were
subsequently acquired. In addition, the holder may not revoke the election without the consent of the IRS. If the holder elects to amortize the premium, it will be required to reduce its tax basis in the debt securities by the amount of the premium
amortized during its holding period. If the holder does not elect to amortize premium, the amount of premium will be included in the holder’s tax basis in the debt securities. Therefore, if the holder does not elect to amortize the premium and
holds the debt securities to maturity, the holder generally will be required to treat the premium as a capital loss when the debt securities are redeemed.

Original Issue Discount. If the stated redemption price at maturity of the debt securities exceeds their issue price by at least the
statutory de minimis amount, the debt securities will be treated as being issued with OID for U.S. federal income tax purposes. The stated redemption price at maturity includes all payments on the debt securities other than qualified stated
interest, which is generally interest that is unconditionally payable at least annually at a fixed or qualified floating rate. If the debt securities are issued with OID, you will be required to include such OID in gross income (as ordinary income)
as it accrues over the term of the debt securities on a constant-yield basis, in advance of the receipt of cash attributable to that income and regardless of your regular method of accounting for U.S. federal income tax purposes.

Acquisition Premium. If a holder purchases debt securities that were issued with OID at a cost greater than their issue price and
less than or equal to their stated redemption price at maturity, the holder will be considered to have purchased the debt securities with acquisition premium. Such holder will generally be permitted to reduce the daily portions of OID required to be
included in income by a fraction, the numerator of which is the excess of the holder’s initial basis in the debt securities over the debt securities’ issue price, and the denominator of which is the excess of the redemption price at
maturity of the debt securities over their issue price.

Market Discount. If the holder purchases debt securities in the
secondary market at a price that reflects a “market discount,” any principal payments on, or any gain that the holder realized on the disposition of, the debt securities generally will be treated as ordinary interest income to the extent
of the market discount that accrued on the debt securities during the time such debt securities were held. “Market discount” is defined under the Code as, in general, the excess (subject to a statutory de minimis amount) of the stated
redemption price at maturity (or in the case of an obligation issued with OID, its “revised issue price”) over the purchase price of the debt security. In addition, the holder may be required to defer the deduction of all or a portion of
any interest paid on any indebtedness incurred or continued to purchase or carry the debt securities that were acquired at a market discount.

The holder may elect to include market discount in gross income currently as it accrues (on either a ratable or constant yield basis), in lieu
of treating a portion of any gain realized on a sale of the debt securities as ordinary income. If the holder elects to include market discount on a current basis, the interest deduction deferral rule described above will not apply and the holder
will increase its basis in the debt security by the amount of

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market discount included in gross income. If the holder does make such an election, it will apply to all market discount debt instruments acquired on or after the first day of the first taxable
year to which the election applies. This election may not be revoked without the consent of the IRS.

Information Reporting and Backup
Withholding. In general, information reporting requirements will apply to payments of principal, interest, and premium, if any, paid on debt securities and to the proceeds of the sale of debt securities paid to U.S. holders other than certain
exempt recipients (such as certain corporations) provided they establish such exemption. Information reporting generally will apply to payments of interest on the debt securities to non-U.S. Holders (as defined below) and the amount of tax, if any,
withheld with respect to such payments. Copies of the information returns reporting such interest payments and any withholding may also be made available to the tax authorities in the country in which the non-U.S. Holder resides under the provisions
of an applicable income tax treaty. In addition, for non-U.S. Holders, information reporting will apply to the proceeds of the sale of debt securities within the United States or conducted through United States-related financial intermediaries
unless the certification requirements described below have been complied with and the statement described below in “Taxation of Non-U.S. Holders” has been received (and the payor does not have actual knowledge or reason to know that the
holder is a United States person) or the holder otherwise establishes an exemption.

We may be required to withhold, for U.S. federal
income tax purposes, a portion of all payments (including redemption proceeds) payable to holders of debt securities who fail to provide us with their correct taxpayer identification number, who fail to make required certifications or who have been
notified by the IRS that they are subject to backup withholding (or if we have been so notified). Certain corporate and other shareholders specified in the Code and the regulations thereunder are exempt from backup withholding. Backup withholding is
not an additional tax. Any amounts withheld may be credited against the holder’s U.S. federal income tax liability, provided the appropriate information is furnished to the IRS.

A holder who is a non-U.S. Holder may have to comply with certification procedures to establish its non-U.S. status in order to avoid backup
withholding tax requirements. The certification procedures required to claim the exemption from withholding tax on interest income described below with respect to non-U.S. Holders will satisfy these requirements.

Taxation of Non-U.S. Holders. If a holder is a non-resident alien individual or a foreign corporation (a “non-U.S. Holder”),
the payment of interest on the debt securities generally will be considered “portfolio interest” and thus generally will be exempt from U.S. federal withholding tax. This exemption will apply to the holder provided that (1) interest
paid on the debt securities is not effectively connected with the holder’s conduct of a trade or business in the United States, (2) the holder is not a bank whose receipt of interest on the debt securities is described in
Section 881(c)(3)(A) of the Code, (3) the holder does not actually or constructively own 10 percent or more of the combined voting power of all classes of our stock entitled to vote, (4) the holder is not a controlled foreign
corporation that is related, directly or indirectly, to us through stock ownership, and (5) the holder satisfies the certification requirements described below.

To satisfy the certification requirements, either (1) the holder of any debt securities must certify, under penalties of perjury, that
such holder is a non-U.S. person and must provide such owner’s name, address and taxpayer identification number, if any, on IRS Form W-8BEN or W-8BEN-E, or (2) a securities clearing organization, bank or other financial institution that
holds customer securities in the ordinary course of its trade or business and holds the debt securities on behalf of the holder thereof must certify, under penalties of perjury, that it has received a valid and properly executed IRS Form W-8BEN or
W-8BEN-E from the beneficial holder and comply with certain other requirements. Special certification rules apply for debt securities held by a foreign partnership and other intermediaries.

Interest on debt securities received by a non-U.S. Holder that is not excluded from U.S. federal withholding tax under the portfolio interest
exemption as described above generally will be subject to withholding at a 30%

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rate, except where (1) the interest is effectively connected with the conduct of a U.S. trade or business, in which case the interest will be subject to U.S. income tax on a net basis as
applicable to U.S. holders generally (and, in the case of corporate non-U.S. Holders, may be subject to an additional 30% branch profits tax) or (2) a non-U.S. Holder can claim the benefits of an applicable income tax treaty to reduce or
eliminate such withholding tax. To claim the benefit of an income tax treaty or to claim an exemption from withholding because the interest is effectively connected with a U.S. trade or business, a non-U.S. Holder must timely provide the
appropriate, properly executed IRS forms. These forms may be required to be periodically updated. Also, a non-U.S. Holder who is claiming the benefits of an income tax treaty may be required to obtain a U.S. taxpayer identification number and to
provide certain documentary evidence issued by foreign governmental authorities to prove residence in the foreign country.

Any
capital gain that a non-U.S. Holder realizes on a sale, exchange or other disposition of debt securities generally will be exempt from U.S. federal income tax, including withholding tax. This exemption will not apply to a holder if their gain is
effectively connected with the conduct of a trade or business in the U.S. or the holder is an individual holder and is present in the U.S. for a period or periods aggregating 183 days or more in the taxable year of the disposition and, in each
case, certain other conditions are met.

See “Information Reporting and Backup Withholding” above for a general discussion of
information reporting and backup withholding requirements applicable to non-U.S. Holders.

Other Tax Matters

Medicare Tax on Certain Investment Income. Certain noncorporate taxpayers are subject to an additional tax of 3.8% with respect to
the lesser of (1) their “net investment income” (or undistributed “net investment income” in the case of an estate or trust) or (2) the excess of their “modified adjusted gross income” over a threshold amount
($250,000 for married persons filing jointly and $200,000 for single taxpayers). For this purpose, “net investment income” includes interest, dividends (including dividends paid with respect to shares), annuities, royalties, rent, net gain
attributable to the disposition of property not held in a trade or business (including net gain from the sale, exchange or other taxable disposition of shares) and certain other income, but will be reduced by any deductions properly allocable to
such income or net gain.

Other Reporting and Withholding Requirements. Sections 1471-1474 of the Code and the U.S.
Treasury and IRS guidance issued thereunder (collectively, “FATCA”) generally require the Fund to obtain information sufficient to identify the status of each of its shareholders and holders of its debt securities under FATCA or under an
applicable intergovernmental agreement (an “IGA”) between the United States and a foreign government. If a shareholder or holder of debt securities fails to provide the required information or otherwise fails to comply with FATCA or an
IGA, the Fund may be required to withhold under FATCA at a rate of 30% with respect to that holder on ordinary dividends and interest payments. The IRS and the Department of Treasury have issued proposed regulations providing that these withholding
rules will not be applicable to the gross proceeds of share redemptions or capital gains dividends that the Fund pays. If a payment by the Fund is subject to FATCA withholding, the Fund is required to withhold even if such payment would otherwise be
exempt from withholding under the rules applicable to non-U.S. persons. Each prospective investor is urged to consult its tax adviser regarding the applicability of FATCA and any other reporting requirements with respect to the prospective
investor’s own situation, including investments through an intermediary.

Shareholders that are U.S. persons and own, directly
or indirectly, more than 50% of the Fund could be required to report annually their “financial interest” in the Fund’s “foreign financial accounts,” if any, on FinCEN Form 114, Report of Foreign Bank and Financial Accounts
(FBAR). Shareholders should consult a tax adviser regarding the applicability to them of this reporting requirement.

Alternative Minimum Tax

Investors may be subject to the federal alternative minimum tax on their income (including taxable income from the Fund), depending on
their individual circumstances.

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CUSTODIAN, TRANSFER AGENT, DIVIDEND DISBURSING AGENT AND
REGISTRAR

The Fund’s securities and cash are held under a custodian agreement with State Street Bank and Trust Company, 100
Lincoln Street, Boston, Massachusetts 02111. The transfer agent, dividend disbursing agent and registrar for the Fund’s shares is Computershare Investor Services, P.O. Box 505000, Louisville, KY 40233-5000.

INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

Deloitte & Touche LLP, 111 S. Wacker Drive, Chicago, IL 60606, serves as our independent registered public accounting firm.
Deloitte & Touche LLP provides audit and audit-related services and consultation in connection with the review of our filing with the SEC.

ADDITIONAL INFORMATION

A Registration Statement on Form N-2, including amendments thereto, relating to the securities offered hereby, has been filed by the Fund with
the SEC, Washington, D.C. The prospectus, any prospectus supplement and this Statement of Additional Information do not contain all of the information set forth in the Registration Statement, including any exhibits and schedules thereto. For further
information with respect to the Fund and the securities offered hereby, reference is made to the Registration Statement. Statements contained in the prospectus, prospectus supplement and this Statement of Additional Information as to the contents of
any contract or other document referred to are not necessarily complete and in each instance reference is made to the copy of such contract or other document filed as an exhibit to the Registration Statement, each such statement being qualified in
all respects by such reference. A copy of the Registration Statement may be inspected without charge at the SEC’s principal office in Washington, D.C., and copies of all or any part thereof may be obtained from the SEC upon the payment of
certain fees prescribed by the SEC.

ADDITIONAL INFORMATION CONCERNING THE AGREEMENT AND DECLARATION OF
TRUST

The Fund’s Agreement and Declaration of Trust provides that the Fund’s Trustees shall have the power to cause each
shareholder to pay directly, in advance or arrears, for charges of the Fund’s custodian or transfer, shareholder servicing or similar agent, an amount fixed from time to time by the Trustees, by setting off such charges due from such
shareholder from declared but unpaid dividends owed such shareholder and/or by reducing the number of shares in the account of such shareholder by that number of full and/or fractional shares which represents the outstanding amount of such charges
due from such shareholder. The Fund has no present intention of relying on this provision of the Agreement and Declaration of Trust and would only do so if consistent with the 1940 Act or the rules and regulations or interpretations of the SEC
thereunder.

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Report of Independent Registered Public Accounting Firm

To the shareholders and the Board of Trustees of Calamos Convertible Opportunities and Income Fund

Opinion on the Financial Statements and Financial Highlights

We have audited the accompanying statement of assets and liabilities of Calamos Convertible Opportunities and Income Fund (the “Fund”), including the
schedule of investments, as of October 31, 2019, the related statements of operations and cash flows for the year then ended, the statements of changes in net assets for each of the two years in the period then ended, the financial highlights
for each of the five years in the period then ended, and the related notes. In our opinion, the financial statements and financial highlights present fairly, in all material respects, the financial position of the Fund as of October 31, 2019,
and the results of its operations and its cash flows for the year then ended, the changes in its net assets for each of the two years in the period then ended, and the financial highlights for each of the five years in the period then ended in
conformity with accounting principles generally accepted in the United States of America.

Basis for Opinion

These financial statements and financial highlights are the responsibility of the Fund’s management. Our responsibility is to express an opinion on the
Fund’s financial statements and financial highlights based on our audits. We are a public accounting firm registered with the Public Company Accounting Oversight Board (United States) (PCAOB) and are required to be independent with respect to
the Fund in accordance with the U.S. federal securities laws and the applicable rules and regulations of the Securities and Exchange Commission and the PCAOB.

We conducted our audits in accordance with the standards of the PCAOB. Those standards require that we plan and perform the audit to obtain reasonable
assurance about whether the financial statements and financial highlights are free of material misstatement, whether due to error or fraud. The Fund is not required to have, nor were we engaged to perform, an audit of its internal control over
financial reporting. As part of our audits we are required to obtain an understanding of internal control over financial reporting but not for the purpose of expressing an opinion on the effectiveness of the Fund’s internal control over
financial reporting. Accordingly, we express no such opinion.

Our audits included performing procedures to assess the risks of material misstatement of
the financial statements and financial highlights, whether due to error or fraud, and performing procedures that respond to those risks. Such procedures included examining, on a test basis, evidence regarding the amounts and disclosures in the
financial statements and financial highlights. Our audits also included evaluating the accounting principles used and significant estimates made by management, as well as evaluating the overall presentation of the financial statements and financial
highlights. Our procedures included confirmation of securities owned as of October 31, 2019, by correspondence with the custodian and brokers; when replies were not received from brokers, we performed other auditing procedures. We believe that
our audits provide a reasonable basis for our opinion.

Chicago, Illinois

December 18, 2019

We have served as the auditor of one or
more Calamos Advisors LLC investment companies since 2003.

F-1

Statement of Assets and Liabilities

October 31, 2019

ASSETS

Investments in securities, at value (cost $1,173,512,890)

$
1,134,945,027

Receivables:

Accrued interest and dividends

8,338,912

Investments sold

2,653,247

Prepaid expenses

387,726

Other assets

157,674

Total assets

1,146,482,586

LIABILITIES

Due to custodian bank

397,606

Mandatory Redeemable Preferred Shares ($25 liquidation value per share applicable to 4,000,000
shares authorized, issued, and outstanding) (net of deferred offering costs of $754,065) (Note 7)

99,245,935

Payables:

Notes payable

277,400,000

Distributions payable to Mandatory Redeemable Preferred Shareholders

331,721

Investments purchased

13,106,353

Affiliates:

Investment advisory fees

763,302

Deferred compensation to trustees

157,674

Trustees’ fees and officer compensation

13,846

Other accounts payable and accrued liabilities

756,120

Total liabilities

392,172,557

NET ASSETS

$
754,310,029

COMPOSITION OF NET ASSETS

Common stock, no par value, unlimited shares authorized 70,898,658 shares issued and
outstanding

$
790,471,430

Undistributed net investment income (loss)

(9,375,303
)

Accumulated net realized gain (loss) on investments and written options

11,781,765

Unrealized appreciation (depreciation) of investments

(38,567,863
)

NET ASSETS

$
754,310,029

Net asset value per common shares based upon 70,898,658 shares issued and outstanding

$
10.64

See accompanying Notes to Financial Statements

F-2

Statement of Operations

Year Ended October 31, 2019

INVESTMENT INCOME

Interest

$
50,332,735

Dividends

6,852,091

Total investment income

57,184,826

EXPENSES

Investment advisory fees

9,012,929

Interest expense on Notes Payable (Note 6)

7,653,512

Interest expense and amortization of offering costs on Mandatory Redeemable Preferred Shares
(Notes 1 and 7)

4,230,208

Printing and mailing fees

105,488

Fund administration fees

100,026

Accounting fees

79,226

Legal fees

60,302

Trustees’ fees and officer compensation

56,974

Audit fees

49,533

Transfer agent fees

33,341

Custodian fees

19,707

Registration fees

18,134

Other

141,239

Total expenses

21,560,619

NET INVESTMENT INCOME (LOSS)

35,624,207

REALIZED AND UNREALIZED GAIN (LOSS)

Net realized gain (loss) from:

Investments, excluding purchased options

21,572,119

Purchased options

(2,246,218
)

Written options

70,049

Change in net unrealized appreciation/(depreciation) on:

Investments, excluding purchased options

24,909,171

Purchased options

840,903

Written options

(1,017
)

NET GAIN (LOSS)

45,145,007

NET INCREASE (DECREASE) IN NET ASSETS RESULTING FROM OPERATIONS

$
80,769,214

See accompanying Notes to Financial Statements

F-3

Statements of Changes in Net Assets

YEAR ENDEDOCTOBER 31, 2019
 
 
YEAR ENDEDOCTOBER 31, 2019-2020

OPERATIONS

Net investment income (loss)

$
35,624,207
 
 
$
40,330,614

Net realized gain (loss)

19,395,950
 
 
 
51,164,984

Change in unrealized appreciation/(depreciation)

25,749,057
 
 
 
(74,760,138
)

Net increase (decrease) in net assets applicable to common shareholders resulting from
operations

80,769,214
 
 
 
16,735,460

DISTRIBUTIONS TO COMMON SHAREHOLDERS

Total distributions

(68,037,902

 
 
(79,591,792
)

Net decrease in net assets from distributions to common shareholders

(68,037,902

 
 
(79,591,792
)

CAPITAL STOCK TRANSACTIONS

Proceeds from shares sold

—  
 
 
 
3,750,338

Offering costs on shares

—  
 
 
 
(31,543
)

Reinvestment of distributions resulting in the issuance of stock

272,867
 
 
 
2,475,449

Net increase (decrease) in net assets from capital stock transactions

272,867
 
 
 
6,194,244

TOTAL INCREASE (DECREASE) IN NET ASSETS

13,004,179
 
 
 
(56,662,088
)

NET ASSETS

Beginning of year

$
741,305,850
 
 
$
797,967,938

End of year

$
754,310,029
 
 
$
741,305,850

See accompanying Notes to Financial Statements

F-4

Statements of Cash Flows

YEARENDEDOCTOBER 31,2019
 
 
YEARENDEDOCTOBER 31,2019-2020

CASH FLOWS FROM OPERATING ACTIVITIES:

Net increase/(decrease) in net assets from operations

$
80,769,214
 
 
$
16,735,460

Adjustments to reconcile net increase/(decrease) in net assets from operations to net cash provided
by operating activities:

Purchase of investment securities, including purchased options

(537,855,441

 
 
(673,388,665
)

Net proceeds from disposition of short term investments

(10,017,684

 
 
7,098,191

Proceeds paid on closing written options

(849,720

 
 
(752,981
)

Proceeds from disposition of investment securities, including purchased options

604,818,078
 
 
 
697,557,826

Premiums received from written options

450,617
 
 
 
1,647,918

Amortization and accretion of fixed-income
securities

(15,850,862

 
 
(13,333,186
)

Amortization of offering costs on Mandatory Redeemable Preferred Shares

228,156
 
 
 
167,404

Net realized gains/losses from investments, excluding purchased options

(21,572,121

 
 
(48,896,213
)

Net realized gains/losses from purchased options

2,246,218
 
 
 
(1,538,771
)

Net realized gains/losses from written options

(70,049

 
 
(744,198
)

Change in unrealized appreciation or depreciation on investments, excluding purchased
options

(24,909,171

 
 
73,455,391

Change in unrealized appreciation or depreciation on purchased options

(840,903

 
 
1,317,098

Change in unrealized appreciation or depreciation on written options

1,017
 
 
 
(10,364
)

Net change in assets and liabilities:

(Increase)/decrease in assets:

Accrued interest and dividends receivable

1,300,330
 
 
 
626,923

Prepaid expenses

43,874
 
 
 
(344,633
)

Other assets

(284

 
 
1,057,521

Increase/(decrease) in liabilities:

Payables to affiliates

(46,558

 
 
(16,875
)

Other accounts payable and accrued liabilities

75,142
 
 
 
(100,243
)

Net cash provided by/(used in) operating activities

$
77,919,853
 
 
$
60,537,603

CASH FLOWS FROM FINANCING ACTIVITIES:

Increase/(Decrease) in Proceeds from shares sold


 
 
 
3,750,338

Offering costs related to shares sold


 
 
 
(31,543
)

Distributions to shareholders

(67,765,035

 
 
(77,116,343
)

(Decrease)/Increase in Distributions to Mandatory Redeemable Preferred Shareholders

21,402
 
 
 
310,319

Offering costs on Mandatory Redeemable Preferred Shares

(69,595

 
 
(22,884
)

Net increase/(decrease) in due to custodian bank

397,606
 
 
 
(331,721
)

(Repayment)/Proceeds from note payable

(10,600,000

 
 
13,000,000

Net cash provided by/(used in) financing activities

$
(78,015,622

 
$
(60,441,834
)

Net increase/(decrease) in cash

$
(95,769

 
$
95,769

Cash and restricted cash at beginning of year

$
95,769
 
 
$

Cash at end of year

$
—  
 
 
$
95,769

Supplemental disclosure

Cash paid for interest on Notes Payable

$
7,599,323
 
 
$
5,702,742

Cash paid for interest expense and amortization of offering costs on Mandatory Redeemable Preferred
Shares

$
4,208,806
 
 
$
4,436,971

Non-cash financing activities not included herein consists
of reinvestment of dividends and distributions

$
272,867
 
 
$
2,475,449

The following table provides a reconciliation of cash and restricted cash reported within the Statement of Assets and
Liabilities that sum to the total of the same such amounts shown in the Statements of Cash Flows.

Cash with custodian

$
                —  
 
 
$
           95,769

Restricted cash for swap collateral

—  
 
 
 

Total cash and restricted cash at period end

$
                —  
 
 
$
95,769

See accompanying Notes to Financial Statements

F-5

Notes to Financial Statements

Note 1 – Organization and Significant Accounting Policies

Organization. Calamos Convertible Opportunities and Income Fund (the “Fund”) was organized as a Delaware statutory trust on
April 17, 2002 and is registered under the Investment Company Act of 1940 (the “1940 Act”) as a diversified, closed-end management investment company. The Fund commenced operations on
June 26, 2002.

The Fund’s investment strategy is to provide total return through a combination of capital appreciation and
current income. Under normal circumstances, the Fund will invest at least 80% of its managed assets in a diversified portfolio of convertibles and non-convertible income securities and under normal
circumstances, the Fund will invest at least 35% of its managed assets in convertible securities. The Fund invests in securities with a broad range of maturities. The average term to maturity of the Fund’s securities typically will range from
five to ten years. A substantial portion of the Fund’s assets may be invested in below investment grade (high yield, high risk) securities. “Managed assets” means the Fund’s total assets (including any assets attributable to any
leverage that may be outstanding) minus total liabilities (other than debt representing financial leverage).

Significant Accounting
Policies. The financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (U.S. GAAP), and the Fund is considered an investment company under U.S. GAAP and follows the
accounting and reporting guidance applicable to investment companies. Under U.S. GAAP, management is required to make certain estimates and assumptions at the date of the financial statements and actual results may differ from those estimates.
Subsequent events, if any, through the date that the financial statements were issued, have been evaluated in the preparation of the financial statements. The following summarizes the significant accounting policies of the Fund:

Fund Valuation. The valuation of the Fund’s investments is in accordance with policies and procedures adopted by and under the
ultimate supervision of the board of trustees.

Fund securities that are traded on U.S. securities exchanges, except option securities,
are valued at the official closing price, which is the last current reported sales price on its principal exchange at the time each Fund determines its net asset value (“NAV”). Securities traded in the over-the-counter market and quoted on The NASDAQ Stock Market are valued at the NASDAQ Official Closing Price, as determined by NASDAQ, or lacking a NASDAQ Official Closing Price, the last current reported
sale price on NASDAQ at the time a Fund determines its NAV. When a last sale or closing price is not available, equity securities, other than option securities, that are traded on a U.S. securities exchange and other equity securities traded in the over-the-counter market are valued at the mean between the most recent bid and asked quotations on its principal exchange in accordance with guidelines adopted by the board of
trustees. Each option security traded on a U.S. securities exchange is valued at the mid-point of the consolidated bid/ask quote for the option security, also in accordance with guidelines adopted by the board
of trustees. Each over-the-counter option that is not traded through the Options Clearing Corporation is valued either by an independent pricing agent approved by the
board of trustees or based on a quotation provided by the counterparty to such option under the ultimate supervision of the board of trustees.

Fixed income securities, bank loans, certain convertible preferred securities, and non-exchange traded
derivatives are normally valued by independent pricing services or by dealers or brokers who make markets in such securities. Valuations of such fixed income securities, bank loans, certain convertible preferred securities, and non-exchange traded derivatives consider yield or price of equivalent securities of comparable quality, coupon rate, maturity, type of issue, trading characteristics and other market data and do not rely exclusively
upon exchange or over-the-counter prices.

Trading on
European and Far Eastern exchanges and over-the-counter markets is typically completed at various times before the close of business on each day on which the New York
Stock Exchange (“NYSE”) is

F-6

open. Each security trading on these exchanges or in over-the-counter markets may be valued utilizing a systematic
fair valuation model provided by an independent pricing service approved by the board of trustees. The valuation of each security that meets certain criteria in relation to the valuation model is systematically adjusted to reflect the impact of
movement in the U.S. market after the foreign markets close. Securities that do not meet the criteria, or that are principally traded in other foreign markets, are valued as of the last reported sale price at the time the Fund determines its NAV, or
when reliable market prices or quotations are not readily available, at the mean between the most recent bid and asked quotations as of the close of the appropriate exchange or other designated time. Trading of foreign securities may not take place
on every NYSE business day. In addition, trading may take place in various foreign markets on Saturdays or on other days when the NYSE is not open and on which the Fund’s NAV is not calculated.

If the pricing committee determines that the valuation of a security in accordance with the methods described above is not reflective of a
fair value for such security, the security is valued at a fair value by the pricing committee, under the ultimate supervision of the board of trustees, following the guidelines and/or procedures adopted by the board of trustees.

The Fund also may use fair value pricing, pursuant to guidelines adopted by the board of trustees and under the ultimate supervision of the
board of trustees, if trading in the security is halted or if the value of a security it holds is materially affected by events occurring before the Fund’s pricing time but after the close of the primary market or exchange on which the security
is listed. Those procedures may utilize valuations furnished by pricing services approved by the board of trustees, which may be based on market transactions for comparable securities and various relationships between securities that are generally
recognized by institutional traders, a computerized matrix system, or appraisals derived from information concerning the securities or similar securities received from recognized dealers in those securities.

When fair value pricing of securities is employed, the prices of securities used by a Fund to calculate its NAV may differ from market
quotations or official closing prices. There can be no assurance that the Fund could purchase or sell a portfolio security at the price used to calculate the Fund’s net asset value (“NAV”).

Investment Transactions. Investment transactions are recorded on a trade date basis as of October 31, 2019. Net realized gains and
losses from investment transactions are reported on an identified cost basis. Interest income is recognized using the accrual method and includes accretion of original issue and market discount and amortization of premium. Dividend income is
recognized on the ex-dividend date, except that certain dividends from foreign securities are recorded as soon as the information becomes available after the ex-dividend
date.

Foreign Currency Translation. Values of investments and other assets and liabilities denominated in foreign currencies are
translated into U.S. dollars using a rate quoted by a major bank or dealer in the particular currency market, as reported by a recognized quotation dissemination service.

The Fund does not isolate that portion of the results of operations resulting from changes in foreign exchange rates on investments from the
fluctuations arising from changes in market prices of securities held. Such fluctuations are included with the net realized and unrealized gain or loss from investments.

Reported net realized foreign currency gains or losses arise from disposition of foreign currency, the difference in the foreign exchange
rates between the trade and settlement dates on securities transactions, and the difference between the amounts of dividends, interest and foreign withholding taxes recorded on the ex-date or accrual date and
the U.S. dollar equivalent of the amounts actually received or paid. Net unrealized foreign exchange gains and losses arise from changes (due to the changes in the exchange rate) in the value of foreign currency and other assets and liabilities
denominated in foreign currencies held at period end.

Allocation of Expenses Among Funds. Expenses directly attributable to the
Fund are charged to the Fund; certain other common expenses of Calamos Advisors Trust, Calamos Investment Trust, Calamos Convertible

F-7

Opportunities and Income Fund, Calamos Convertible and High Income Fund, Calamos Strategic Total Return Fund, Calamos Global Total Return Fund, Calamos Global Dynamic Income Fund and
Calamos Dynamic Convertible and Income Fund are allocated proportionately among each Fund to which the expenses relate in relation to the net assets of each Fund or on another reasonable basis.

Income Taxes. No provision has been made for U.S. income taxes because the Fund’s policy is to continue to qualify as a regulated
investment company under the Internal Revenue Code of 1986, as amended, and distribute to shareholders substantially all of the Fund’s taxable income and net realized gains.

Dividends and distributions paid to common shareholders are recorded on the ex-dividend date. The
amount of dividends and distributions from net investment income and net realized capital gains is determined in accordance with federal income tax regulations, which may differ from U.S. generally accepted accounting principles. To the extent these
“book/tax” differences are permanent in nature, such amounts are reclassified within the capital accounts based on their federal tax-basis treatment. These differences are primarily due to differing
treatments for foreign currency transactions, contingent payment debt instruments and methods of amortizing and accreting for fixed income securities. The financial statements are not adjusted for temporary differences.

Distributions to holders of mandatory redeemable preferred shares (“MRPS”) as described in Note 7 are accrued on a daily basis and
are treated as an operating expense due to the fixed term of the obligation. The distributions are shown on the Statement of Operations as Interest expense and amortization of offering costs on Mandatory Redeemable Preferred Shares. For tax
purposes, the distributions made to the holders of the MRPS are treated as dividends.

The Fund recognized no liability for uncertain tax
positions. A reconciliation is not provided as the beginning and ending amounts of unrecognized benefits are zero, with no interim additions, reductions or settlements. Tax years 2019-2020 – 2019-2020 remain subject to examination by the U.S. and the
State of Illinois tax jurisdictions.

Indemnifications. Under the Fund’s organizational documents, the Fund is obligated to
indemnify its officers and trustees against certain liabilities incurred by them by reason of having been an officer or trustee of the Fund. In addition, in the normal course of business, the Fund may enter into contracts that provide general
indemnifications to other parties. The Fund’s maximum exposure under these arrangements is unknown as this would involve future claims that may be made against the Fund that have not yet occurred. Currently, the Fund’s management expects
the risk of material loss in connection to a potential claim to be remote.

Note 2 – Investment Adviser and Transactions With Affiliates Or
Certain Other Parties

Pursuant to an investment advisory agreement with Calamos Advisors LLC (“Calamos Advisors”), the Fund
pays an annual fee, payable monthly, equal to 0.80% based on the average weekly managed assets.

The Fund has an agreement with
Ernst & Young LLP (“EY”) to provide certain tax services to the Fund. The tax services include the following: calculating, tracking and reporting tax adjustments on all assets of the Fund, including but not limited to contingent
debt and preferred trust obligations; preparing excise tax and fiscal year distribution schedules; preparing tax information required for financial statement footnotes; preparing state and federal income tax returns; preparing specialized
calculations of amortization on convertible securities; preparing year-end dividend disclosure information; providing treaty-based foreign withholding tax reclaim services; providing certain global compliance
and reporting services; providing a match service and analysis of the “passive foreign investment company status of foreign corporate entities; and providing services related to corporate actions that may or may not have a tax impact on the
Fund’s holdings. The Fund has an agreement with State Street pursuant to which State Street provides certain administration treasury services to the Fund. These services include: monitoring the calculation of expense accrual amounts for the
Fund and making any necessary

F-8

modifications; managing the Fund’s expenses and expense payment processing; coordinating any expense reimbursement calculations and payment; calculating net investment income dividends and
capital gain distributions; coordinating the audits for the Fund; preparing financial reporting statements for the Fund; preparing certain regulatory filings; and calculating asset coverage tests for certain Calamos Funds.

The Fund reimburses Calamos Advisors for a portion of compensation paid to the Fund’s Chief Compliance Officer. This compensation is
reported as part of the “Trustees’ fees and officer compensation” expense on the Statement of Operations.

The Fund has
adopted a deferred compensation plan (the “Plan”). Under the Plan, a trustee who is not an “interested person” (as defined in the 1940 Act) and has elected to participate in the Plan (a “participating trustee”) may
defer receipt of all or a portion of their compensation from the Fund. The deferred compensation payable to the participating trustee is credited to the trustee’s deferral account as of the business day such compensation would have been paid to
the participating trustee. The value of amounts deferred for a participating trustee is determined by reference to the change in value of Class I shares of one or more funds of Calamos Investment Trust designated by the participant. The value
of the account increases with contributions to the account or with increases in the value of the measuring shares, and the value of the account decreases with withdrawals from the account or with declines in the value of the measuring shares.
Deferred compensation of $157,674 is included in “Other assets” on the Statement of Assets and Liabilities at October 31, 2019. The Fund’s obligation to make payments under the Plan is a general obligation of the Fund and is
included in “Payable for deferred compensation to trustees” on the Statement of Assets and Liabilities at October 31, 2019.

Note 3
– Investments

The cost of purchases and proceeds from sales of long-term investments for the year ended October 31, 2019
were as follows:

U.S. GOVERNMENTSECURITIES
 
  
OTHER

Cost of purchases

$
—  
 
  
$
553,280,359

Proceeds from sales

10,116,035
 
  
 
554,392,185

The cost basis of investments (excluding Investments of Collateral for Securities on Loan) for federal income
tax purposes at October 31, 2019 was as follows:

Cost basis of investments

$
1,170,969,428

Gross unrealized appreciation

51,630,392

Gross unrealized depreciation

(87,654,793
)

Net unrealized appreciation (depreciation)

$
(36,024,401
)

Note 4 – Income Taxes

For the fiscal year ended October 31, 2019, the Fund recorded the following permanent reclassifications to reflect tax character. The
results of operations and net assets were not affected by these reclassifications.

Paid-in capital

$
(12,901,113
)

Undistributed net investment income/(loss)

16,706,571

Accumulated net realized gain/(loss) on investments

(3,805,458
)

The Fund intends to make monthly distributions from its income available for distribution, which consists of
the Fund’s dividends and interest income after payment of Fund expenses, and net realized gains on stock

F-9

investments. At least annually, the Fund intends to distribute all or substantially all of its net realized capital gains, if any. Distributions are recorded on the
ex-dividend date. The Fund distinguishes between distributions on a tax basis and a financial reporting basis. Accounting principles generally accepted in the United States of America require that only
distributions in excess of tax basis earnings and profits be reported in the financial statements as a return of capital. Permanent differences between book and tax accounting relating to distributions are reclassified to paid-in-capital. For tax purposes, distributions from short-term capital gains are considered to be from ordinary income. Distributions in any year may include a return of
capital component.

Distributions for the year ended October 31, 2019 were characterized for federal income tax purposes as follows:

YEAR ENDEDOCTOBER 31, 2019
 
  
YEAR ENDEDOCTOBER 31, 2019-2020

Distributions paid from:

Ordinary income

$
38,246,735
 
  
$
81,202,251

Long-term capital gains

21,493,844
 
  
 
2,348,789

Return of capital

12,299,375
 
  
 

As of October 31, 2019, the components of
accumulated earnings/(loss) on a tax basis were as follows:

Undistributed ordinary income

$

Undistributed capital gains

Total undistributed earnings

Accumulated capital and other losses

Net unrealized gains/(losses)

(36,024,401
)

Total accumulated earnings/(losses)

(36,024,401
)

Other

(137,000
)

Paid-in-capital

790,471,430

Net assets applicable to common shareholders

$
754,310,029

Note 5 – Derivative Instruments

Foreign Currency Risk. The Fund may engage in portfolio hedging with respect to changes in currency exchange rates by entering into forward
foreign currency contracts to purchase or sell currencies. A forward foreign currency contract is a commitment to purchase or sell a foreign currency at a future date at a negotiated forward rate. Risks associated with such contracts include, among
other things, movement in the value of the foreign currency relative to the U.S. dollar and the ability of the counterparty to perform.

To mitigate the counterparty risk, the Fund may enter into an International Swaps and Derivatives Association, Inc. Master Agreement
(“ISDA Master Agreement”) or similar agreement with its derivative contract counterparties. An ISDA Master Agreement is a bilateral agreement between the Fund and a counterparty that governs over-the-counter derivatives and foreign exchange contracts and typically contains, among other things, collateral posting terms and netting provisions in the event of a default and/or termination event.
Under an ISDA Master Agreement, the Fund may, under certain circumstances, offset with the counterparty certain derivative financial instrument’s payables and/or receivables with collateral held and/or posted and create one single net payment.
The provisions of the ISDA Master Agreement typically permit a single net payment in the event of default (close-out netting), including the bankruptcy or insolvency of the counterparty. Generally, collateral
is exchanged between the Fund and the counterparty and the amount of collateral due from the Fund or to a counterparty has to exceed a minimum transfer amount threshold before a transfer has to be made. To the extent amounts due to the Fund from its
counterparties are not fully

F-10

collateralized, contractually or otherwise, the Fund bears the risk of loss from counterparty nonperformance. When a Fund is required to post collateral under the terms of a derivatives
transaction and master netting agreement, the Fund’s custodian holds the collateral in a segregated account, subject to the terms of a tri-party agreement among the Fund, the custodian and the
counterparty. The master netting agreement and tri-party agreement provide, in relevant part, that the counterparty may have rights to the amounts in the segregated account in the event that the Fund
defaults in its obligation with respect to the derivative instrument that is subject to the collateral requirement. When a counterparty is required to post collateral under the terms of a derivatives transaction and master netting agreement,
the counterparty delivers such amount to the Fund’s custodian. The master netting agreement provides, in relevant part, that the Fund may have rights to such collateral in the event that the counterparty defaults in its obligation with
respect to the derivative instrument that is subject to the collateral requirement. Generally before a default, neither the Fund nor the counterparty may resell, rehypothecate, or repledge any collateral that it receives.