As filed with the Securities and Exchange Commission on April 9, 2018

1933 Act File No. 333-

1940 Act File No. 811-21547

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.

and

☒REGISTRATION STATEMENT UNDER THE INVESTMENT COMPANY ACT OF 1940

☒Amendment No. 24

CALAMOS GLOBAL TOTAL RETURN FUND

2020 Calamos Court
Naperville, Illinois 60563
(630) 245-7200

Agent for Service
John P. Calamos, Sr.
President
Calamos Global Total Return Fund
2020 Calamos Court
Naperville, Illinois 60563

Copies of Communications to:

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)

CALCULATION OF REGISTRATION FEE
UNDER THE SECURITIES ACT OF 1933

(1)There are being registered hereunder a presently indeterminate number of shares of common stock to be offered on an immediate, continuous or delayed basis.

(2)Estimated solely for the purpose of calculating the registration fee pursuant to Rule 457(o) under the Securities Act of 1933, as amended.

(3)Transmitted prior to filing. 

The Registrant hereby amends this Registration Statement on such date or dates as may be necessary to delay its effective date until the Registrant shall file a further amendment which specifically states that this Registration Statement shall thereafter become effective in accordance with Section 8(a) of the Securities Act of 1933 or until the Registration Statement shall become effective on such dates as the Commission, acting pursuant to said Section 8(a), may determine.

Base Prospectus

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

Subject to Completion Dated [                   ], 2018

$

Calamos Global Total Return Fund

Common Shares
Preferred Shares
Debt Securities

Calamos Global Total Return Fund (the “Fund,” “we,” “us,” or “our”) is a diversified, closed-end management investment company that commenced investment operations in October 2005. 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 $                     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 or 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 “CGO.” As of February 28, 2018, the last reported sale price for our common shares was $14.88. As of February 28, 2018, the last reported net asset value for our common shares was $13.55.

Investing in our securities involves certain risks. You could lose some or all of your investment. See “Risk Factors” beginning on page 41 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.

Prospectus dated                    , 2018

This prospectus, together with any accompanying other 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 82 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 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. 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. 20549-0102.

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 investors of any material changes to the extent required by applicable law.

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 the 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”).

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. 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 41 of this prospectus.

The Fund

The Fund is a diversified, closed-end management investment company. We commenced operations in October 2005 following our initial public offering. As of February 28, 2018, we had $169.0 million of total managed assets, including $12 million of outstanding mandatory redeemable preferred shares (“MRP Shares”) and $28 million of outstanding borrowings under a liquidity agreement, plus additional structural leverage that amounted to approximately $14 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 February 28, 2018, Calamos managed approximately $21.6 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 1.00% 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). “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 $ 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.

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 (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.

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, 2018, 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 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 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 his, her or its 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 his, her or its 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 will invest primarily in a portfolio of common and preferred stocks, convertible securities and income producing securities such as investment grade and below investment grade (high yield/high risk) debt securities. The Fund, under normal circumstances, will invest at least 50% of its managed assets in equity securities (including securities that are convertible into equity securities). The Fund may invest up to 100% of its managed assets in securities of foreign issuers, including debt and equity securities of corporate issuers and debt securities of government issuers, in developed and emerging markets. Under normal circumstances, the Fund will invest at least 30% of its managed assets in securities of foreign issuers. The Fund will invest in the securities of issuers of several different countries throughout the world, in addition to the United States.

Calamos will dynamically allocate the Fund’s investments among multiple asset classes (rather than maintaining a fixed or static allocation), seeking to obtain an appropriate balance of risk and reward through all market cycles using multiple strategies and combining them to seek to achieve favorable risk adjusted returns.

The Fund will attempt to keep a consistent balance between risk and reward over the course of different market cycles, through various combinations of stocks, bonds, and/or convertible securities, to achieve what Calamos believes to be an appropriate blend for the then current market. As the market environment changes,

portfolio securities may change in an attempt to achieve a relatively consistent risk level over time. At some points in a market cycle, one type of security may make up a substantial portion of the Fund’s portfolio, while at other times certain securities may have minimal or no representation, depending on market conditions.

The Fund may also seek to generate income from option premiums by writing (selling) options (with an aggregate notional value of up to 33% of the value of the Fund’s managed assets). The Fund will opportunistically employ a strategy of writing options. The extent of option writing activity will depend upon market conditions and Calamos’ ongoing assessment of the attractiveness of writing options on the Fund’s equity holdings.

The Fund’s derivative activities are principally focused on the following derivatives: interest rate swaps, convertible securities, synthetic convertible securities, options on individual securities, index options and forward currency exchange contracts (“forward contracts”). However, the Fund reserves the right to invest in other derivative instruments to the extent it is consistent with the Fund’s investment objective and restrictions.

Equity Securities. Equity securities include common and preferred stocks, warrants, rights, and depository receipts. Under normal circumstances, the Fund will invest at least 50% of its managed assets in equity securities (including securities that are convertible into equity securities). See “— Convertible Securities” below. The Fund may invest in preferred stocks and convertible securities of any rating, including below investment grade. See “— High Yield Securities” below. 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 movements in the stock market. A drop in the stock market may depress the price of equity securities held by the Fund.

Debt Securities. The Fund may invest in debt securities, including debt securities of U.S. and foreign corporate issuers (also known as corporate bonds). Holders of corporate bonds, as creditors, have a prior legal claim over common and preferred stockholders as to both income and assets of the issuer for the principal and interest due them and may have a prior claim over other creditors if liens or mortgages are involved. Interest on corporate bonds may be fixed or floating, or the securities may be zero coupon fixed income securities which pay no interest. Corporate bonds contain elements of both interest rate risk and credit risk. The market value of a corporate bond generally may be expected to rise and fall inversely with changes in interest rates and may also be affected by the credit rating of the issuer, the issuer’s performance and perceptions of the issuer in the marketplace.

High Yield Securities. The Fund may invest in high yield securities for either current income or capital appreciation or both. These securities are rated below investment grade—i.e., 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. 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. They 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. The Fund may invest up to 100% of its managed 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. Under normal circumstances, the Fund will invest at least 30% of its managed assets in securities of foreign issuers; however, the Fund anticipates that ordinarily Calamos’ investment process will result in the Fund investing at least 40% of its managed assets in securities of foreign issuers. The Fund will invest in the securities of issuers of several different countries throughout the world, in addition to the United States. 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 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. See “Investment Objective and Principal Investment Strategies — Principal Investment Strategies — Foreign Securities.”

Convertible Securities. The Fund may invest in convertible securities. A convertible security is a debt security or preferred stock that is exchangeable for an equity security (typically 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. Securities that are convertible into equity securities are considered equity securities for purposes of the Fund’s policy to invest at least 50% of its managed assets in equity securities.

Synthetic Convertible Securities. The Fund may invest in “synthetic” convertible securities. A synthetic convertible security is a financial instrument that is designed to simulate the characteristics of another instrument (i.e., a convertible security) through the combined features of a collection of other securities or assets. Calamos may create a synthetic convertible security 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 securities created by third parties, typically investment banks. Synthetic convertible securities 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 securities may alter these characteristics by offering enhanced yields in exchange for reduced capital appreciation or 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 securities are considered equity securities for purposes of the Fund’s policy to invest at least 50% of its managed assets in equity securities. If the Fund purchases a synthetic convertible security, a component of which is an option, such option will not be considered an option for the purpose of the Fund’s limitations on options described below. See “Investment Objective and Principal Investment Strategies — Principal Investment Strategies — Synthetic Convertible Securities.”

Options Writing. The Fund may seek to generate income from option premiums by writing (selling) options (with an aggregate notional value of up to 33% of the value of the Fund’s managed assets). 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 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. See “Investment Objective and Principal Investment Strategies — Principal Investment Strategies — Options Writing” and “Investment Objective and Principal Investment Strategies — Principal Investment Strategies — Options in General.”

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.”

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 approximates 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 may experience greater volatility in market value than U.S. government or other 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, in which case the Fund will forego the opportunity to purchase additional income producing assets with the liquidation proceeds. 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. See “Investment Objective and Principal Investment Strategies — Principal Investment Strategies — Zero Coupon Securities.”

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 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.

See “Investment Objective and Principal Investment Strategies — Principal Investment Strategies” for a further discussion of the primary investments and principal investment strategies of the Fund.

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”) that allows the Fund to borrow up to $55 million and (ii) through the issuance of three series of mandatory redeemable preferred shares (“MRP Shares”) with an aggregate liquidation preference of $12.0 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 160,000 Series A MRP Shares, with an aggregate liquidation preference of $4.0 million and a mandatory redemption date of September 6, 2022; 160,000 Series B MRP Shares, with an aggregate liquidation preference of $4.0 million and a mandatory redemption date of September 6, 2024; and 160,000 Series C MRP Shares, with an aggregate liquidation preference of $4.0 million 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 February 28, 2018, the Fund had utilized $42 million of the $55 million available under the SSB Agreement ($28 million in borrowings outstanding, and $14 million in structural leverage consisting of collateral received from SSB in connection with securities on loan), representing 24.9% of managed assets as of that date, and had $12 million of MRP Shares outstanding, representing 7.1% of managed assets. Combined, the borrowings under the SSB Agreement and the outstanding MRP Shares represented 32.0% 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 total 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 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 or cap 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.”

Forward Currency Exchange Transactions

The Fund may use forward currency exchange 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 in the statement of additional information under “Investment Objective and Policies — 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.

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. See “Investment Objective and Principal Investment Strategies — “Forward Currency Exchange 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 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 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; or (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. See “Investment Objective and Principal Investment Strategies — Conflicts of Interest.”

Fund Risks

Equity Securities Risk. Equity investments are subject to greater fluctuations in market value than other asset classes as a result of such factors as the issuer’s business performance, investor perceptions, stock market trends and general economic conditions. Equity securities are subordinated to bonds and other debt instruments in a company’s capital structure in terms of priority to corporate income and liquidation payments. The Fund may invest in preferred stocks and convertible securities of any rating, including below investment grade. See “Risk Factors — Fund Risks — Equity Securities Risk.”

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.

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.

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 since the inception of the Fund 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. 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. See “Risk Factors — Fund Risks — High Yield Securities 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.”

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 economics 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.”

Currency Risk. The value of the securities denominated or quoted in foreign currencies may be adversely affected by fluctuations in the relative currency exchange rates and by exchange control regulations. The Fund’s investment performance may be negatively affected by a devaluation of a currency in which the Fund’s investments are denominated or quoted. Further, the Fund’s investment performance may be significantly affected, either positively or negatively, by currency exchange rates because the U.S. dollar value of securities denominated or quoted in another currency will increase or decrease in response to changes in the value of such currency in relation to the U.S. dollar. See “Risk Factors — Fund Risks — Currency 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; and

•the risks associated with rising interest rates may be particularly acute in the current market environment because market interest rates currently are near historically low levels. However, continued economic recovery, the end of the Federal Reserve Board’s quantitative easing program, and an increased likelihood of a rising interest rate environment increase the risk that interest rates will continue to rise in the near future.

See “Risk Factors — Fund Risks — Interest Rate 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.

Leverage Risk. The Fund has issued indebtedness and preferred shares and may borrow money or issue debt securities. As of February 28, 2018, 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 total 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. 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 borrowings. The Fund may be subject to certain restrictions on investments imposed by guidelines of rating agencies which may issue ratings for the preferred shares or short-term 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. 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. See “Prospectus Summary — Use of Leverage by 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.”

Liquidity Risk. The Fund may invest up to 15% of its managed assets in securities that, at the time of investment, are illiquid (i.e., securities that cannot be disposed of within 7 days in the ordinary course of business at approximately the value at which the Fund has valued the securities). The Fund may also invest without limit in Rule 144A Securities determined to be liquid. Calamos, under the supervision and oversight of the Board of Trustees, will determine whether Rule 144A Securities are illiquid (that is, not readily marketable) and thus subject to the Fund’s limit on investing no more than 15% of its managed assets in illiquid securities. Investments in Rule 144A Securities could have the effect of increasing the amount of the Fund’s assets invested in illiquid securities if qualified institutional buyers are unwilling to purchase these Rule 144A Securities. 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. See “Risk Factors — Fund Risks — Liquidity Risk.”

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, the convertible’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’s “conversion price.” The conversion price is defined as the predetermined price at which the convertible 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.”

Synthetic Convertible Instruments Risk. The value of a synthetic convertible instrument may respond differently to market fluctuations than a convertible security because a synthetic convertible instrument is composed of two or more separate instruments, 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.”

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 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 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. See “Risk Factors — Fund Risks — Risks Associated with Options.”

Forward Currency Exchange Contracts Risk. Forward contracts are contractual agreements to purchase or sell a specified currency at a specified future date (or within a specified time period) at a price set at the time of the contract. The Fund may not fully benefit from, or may lose money on, forward currency exchange transactions if changes in currency exchange rates do not occur as anticipated or do not correspond accurately to changes in the value of the Fund’s holdings.

Tax Risk. The Fund may invest in certain securities, such as certain convertible 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. See “Risk Factors — Fund Risks — Tax Risk” and “Certain Federal Income Tax Matters.”

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.”

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, if any, may 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 other 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.”

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.”

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.”

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 quasigovernmental 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.

Following the financial crisis that began in 2007, the Federal Reserve attempted to stabilize the U.S. economy and support the U.S. economic recovery by keeping the federal funds rate low. More recently, the Federal Reserve has terminated certain of its market support activities and began raising interest rates. The withdrawal of this support could negatively affect financial markets generally as well as reduce the value and liquidity of certain securities. Additionally, with continued economic recovery and the cessation of certain

market support activities, the Portfolio may face a heightened level of interest rate risk as a result of a rise or increased volatility in interest rates. These policy changes may reduce liquidity for certain of the Portfolio’s investments, causing the value of the Portfolio’s investments and share price to decline. To the extent the Portfolio experiences high redemptions because of these policy changes, the Portfolio may experience increased portfolio turnover, which will increase the costs that the Portfolio incurs and may lower the Portfolio’s performance.

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 a Fund’s portfolio investments. In June 2016, the United Kingdom approved a referendum to leave the European Union (“EU”).

On March 29, 2017, the United Kingdom formally notified the European Council of its intention to leave the EU. As a result, the United Kingdom will remain a member state, subject to European law, with privileges to provide services under the single market directives for at least two years from that date. 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. The 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. See “Risk Factors — Fund Risks — Recent Market Events.”

Additional Risks to Common Shareholders

Additional risks of investing in common shares include the following:

Interest Rate Transactions Risk. The Fund may enter into an interest rate swap or cap transaction to attempt to protect itself from increasing dividend or interest expenses on its leverage resulting from increasing short-term interest rates. 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.”

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.

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.

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.

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.

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:

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.

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.

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.

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.

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

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.

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.

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.

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

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 February 28, 2018, 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 February 28, 2018. As of February 28, 2018, we had $28 million in borrowings outstanding, $12 million in outstanding preferred shares and additional structural leverage of $14 million, collectively representing 32.0% of managed assets as of that date.

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 2.70% of net assets attributable to common shareholders; (2) a 5% annual return; and (3) all distributions are reinvested at net asset value:

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 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, for its investment management services in an amount equal to 1.00% 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 1.44% of the Fund’s average weekly net assets as of February 28, 2018 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 $26.5 million in average borrowings under the SSB Agreement, plus $12.7 million in additional average structural leverage related to certain securities lending programs, as described under “Leverage.”

(5)Reflects estimated dividend expense on $12.0 million aggregate liquidation preference of mandatory redeemable preferred shares outstanding. See “Leverage.”

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

(7)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.”

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, 2017 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 our annual report dated October 31, 2017 and is included in the statement of additional information, both of which are available from us. See “Available Information” in this prospectus.

Selected data for a share outstanding throughout each period were as follows:

*Net investment income calculated based on average shares method.

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

(d)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 1.62%, 1.62%, 1.63%, 1.59%, 1.57%, 1.58%, 1.46%, 1.49%, 1.55%, 1.69%, respectively.

(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 number of Mandatory Redeemable Preferred Shares outstanding, and by multiplying the result by 25.

MARKET AND NET ASSET VALUE INFORMATION

Our common shares are listed on the NASDAQ Global Select Market (“NASDAQ”) under the symbol “CGO.” Our common shares commenced trading on the New York Stock Exchange (“NYSE”) on October 27, 2005. 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 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 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” for information as to the determination of our NAV.

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 premium to NAV per common share on February 28, 2018 were $14.88, $13.55 and 9.82%, respectively. As of February 28, 2018, we had 8,486,017 common shares outstanding and managed assets of $169.0 million.

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 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.

THE FUND

Calamos Global Total Return Fund is a diversified, closed-end management investment company which commenced investment operations in October 2005. The Fund was organized as a statutory trust under the laws of the State of Delaware on March 30, 2004, and has registered under the 1940 Act. On October 31, 2005, the Fund issued an aggregate of 8,000,000 common shares, no par value, in an initial public offering and commenced its operations. The net proceeds of the initial public offering were approximately $114,700,003. As of February 28, 2018, the Fund had issued 314,362 common shares in connection with a continuous, at-the-market offering that commenced in March 2010 and ceased in March 2014. The net proceeds of that at-the-market offering were $4,622,875.

As of February 28, 2018, the Fund had $28 million in borrowings outstanding under the SSB Agreement, plus MRP Shares outstanding with an aggregate liquidation preference of $12.0 million, plus additional structural leverage that amounted to approximately $14 million, collectively representing 32.0% 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 the NASDAQ under the symbol “CGO.” 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 February 28, 2018:

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 will invest primarily in a portfolio of common and preferred stocks, convertible securities and income producing securities such as investment grade and below investment grade (high yield/high risk) debt securities. The Fund, under normal circumstances, will invest at least 50% of its managed assets in equity securities (including securities that are convertible into equity securities). The Fund may invest up to 100% of its managed assets in securities of foreign issuers, including debt and equity securities of corporate issuers and debt securities of government issuers, in developed and emerging markets. Under normal circumstances, the Fund will invest at least 30% of its managed assets in securities of foreign issuers. The Fund will invest in the securities of issuers of several different countries throughout the world, in addition to the United States.

Calamos will dynamically allocate the Fund’s investments among multiple asset classes (rather than maintaining a fixed or static allocation), seeking to obtain an appropriate balance of risk and reward on a long-term basis through all market cycles using multiple strategies and combining them to seek to achieve favorable risk adjusted returns.

The Fund will attempt to keep a consistent balance between risk and reward over the course of different market cycles, through various combinations of stocks, bonds, and/or convertible securities, to achieve what Calamos believes to be an appropriate blend for the then current market. As the market environment changes, portfolio securities may change in an attempt to achieve a relatively consistent risk level over time. At some points in a market cycle, one type of security may make up a substantial portion of the Fund’s portfolio, while at other times certain securities may have minimal or no representation, depending on market conditions.

The Fund may also seek to generate income from option premiums by writing (selling) options (with an aggregate notional value of up to 33% of the value of the Fund’s managed assets). The Fund will opportunistically employ a strategy of writing options. The extent of option writing activity will depend upon market conditions and Calamos’ ongoing assessment of the attractiveness of writing options on the Fund’s equity holdings.

The Fund’s derivative activities are principally focused on the following derivatives: interest rate swaps, convertible securities, synthetic convertible securities, options on individual securities, index options and forward currency exchange contracts. However, the Fund reserves the right to invest in other derivative instruments to the extent it is consistent with the Fund’s investment objective and restrictions.

Equity Securities. Equity securities include common and preferred stocks, warrants, rights, and depository receipts. Under normal circumstances, the Fund will invest at least 50% of its managed assets in equity securities (including securities that are convertible into equity securities). See “— Convertible Securities” below. The Fund may invest in preferred stocks and convertible securities of any rating, including below investment grade. See “— High Yield Securities” below. 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.

Debt Securities. The Fund may invest in debt securities, including debt securities of U.S. and foreign corporate issuers (also known as corporate bonds). Corporate bonds are generally used by corporations to borrow money from investors, and may be either secured or unsecured. Collateral used for secured debt includes, but is not limited to, real property, machinery, equipment, accounts receivable, stocks, bonds or notes. Holders of corporate bonds, as creditors, have a prior legal claim over common and preferred stockholders as to both income and assets of the issuer for the principal and interest due them and may have a prior claim over other creditors if liens or mortgages are involved. Interest on corporate bonds may be fixed or floating, or the securities may be zero coupon fixed income securities which pay no interest. Interest on corporate bonds is typically paid semi-annually and is fully taxable to the holder of the bonds. Corporate bonds contain elements of both interest rate risk and credit risk. The market value of a corporate bond generally may be expected to rise and fall inversely with changes in interest rates and may also be affected by the credit rating of the issuer, the issuer’s performance and perceptions of the issuer in the marketplace. See also “— Other Income Securities” below.

High Yield Securities. The Fund may invest in high yield securities for either current income or capital appreciation or both. The high yield securities in which the Fund invests are rated below investment grade—i.e., rated “Ba” or lower by Moody’s or “BB” or lower by S&P’s, or are unrated but determined by Calamos to be of comparable quality. The Fund may invest in high yield securities of any rating. 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. They 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.

Other Income Securities. The Fund may also invest in investment grade debt securities. The Fund’s investments in investment grade debt 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.

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.

Foreign Securities. The Fund may invest up to 100% of its managed 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. Under normal circumstances, the Fund will invest at least 30% of its managed assets in securities of foreign issuers; however, the Fund anticipates that ordinarily Calamos’ investment process will result in the Fund investing at least 40% of its managed assets in securities of foreign issuers. The Fund will invest in the securities of issuers of several different countries throughout the world, in addition to the United States. 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 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.

Convertible Securities. The Fund may invest in convertible securities. A convertible security is a debt security or preferred stock that is exchangeable for an equity security (typically 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 including below investment grade. See “— High Yield Securities” above. Securities that are convertible into equity securities are considered equity-securities for purposes of the Fund’s policy to invest at least 50% of its managed assets in equity securities.

Synthetic Convertible Securities. The Fund may invest in “synthetic” convertible securities. A synthetic convertible security is a financial instrument that is designed to simulate the characteristics of another instrument (i.e., a convertible security) through the combined features of a collection of other securities or assets. Calamos may create a synthetic convertible security 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 securities created by third parties, typically investment banks. Synthetic convertible securities 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 securities 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.

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.

The Fund’s holdings of synthetic convertible securities are considered equity securities for purposes of the Fund’s policy to invest at least 50% of its managed assets in equity securities. If the Fund purchases a synthetic convertible instrument, a component of which is an option, such option will not be considered an option for the purpose of the Fund’s limitations on options described below.

Options Writing. The Fund may seek to generate income from option premiums by writing (selling) options (with an aggregate notional value of up to 33% of the value of the Fund’s managed assets). 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 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.

The Fund may also purchase and sell put options and call options on 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.

In addition, to seek to offset some of the risk of a potential decline in value of certain long positions, the Fund may also, to a limited extent, purchase put options 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 replicate such 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 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 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 (“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.

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 comparable 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, 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.

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.

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 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 advance 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 SEC 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.

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 similar investment strategies as the Fund. Calamos or its affiliates may have financial incentives to favor certain of such accounts over the Fund. Any of their proprietary accounts and 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, the Fund which advice or securities may differ from advice given to, or securities recommended or bought or sold for, other accounts and customers, even though their investment objectives may be the same as, or similar to, the Fund’s 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 client’s 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 the relevant 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 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 funds or 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 and leverage the Fund.

LEVERAGE

The Fund may issue preferred shares or debt securities or borrow to increase its assets available for investment. As of February 28, 2018, the Fund had $28.0 million in borrowings outstanding under the SSB Agreement, MRP Shares outstanding with an aggregate liquidation preference of $12.0 million and used approximately $14.0 million of collateral obtained through securities lending arrangements as an offset against borrowings under the SSB Agreement, for a total of $54.0 million of leverage representing 32.0% of managed assets as of that date. The SSB Agreement provides for additional credit availability for the Fund, such that it may borrow up to $55 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 or borrow money and/or issue debt securities with an aggregate liquidation preference and aggregate principal amount exceeding 38% of the Fund’s total 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 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 involves 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 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.

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, 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. 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 one or more rating agencies, which may issue ratings for any debt securities or preferred shares issued by the Fund. These guidelines 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. 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, 2017, the Fund completed a private placement of 160,000 Series A MRP Shares, 160,000 Series B MRP Shares and 160,000 Series C MRP Shares. Each MRP Share has a liquidation preference of $25.00, resulting in an aggregate liquidation preference of $12.0 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:

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 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” (or the equivalent of such rating by such other rating agency), the Dividend Rate applicable to such 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:

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 series 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.

In connection with the issuance of the MRP Shares, William R. Rybak and Stephen B. Timbers were designated by the Board of Trustees as the Preferred Share Trustees of the Fund. As of February 28, 2018, there were four other Trustees of the Fund, Ms. Breen and Messrs. Calamos, Neal, Tripple. 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 $55.0 million. As of February 28, 2018, the Fund had utilized $42 million of the $55.0 million available under the SSB Agreement ($28 million in borrowings outstanding, and $14 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 0.10% of any undrawn amount. As of February 28, 2018, the interest rate charged under the SSB Agreement was 2.24%. “Net income” payments related to cash collateral in connection with securities lending were 1.12% 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 February 28, 2018, the Fund’s portfolio would need to experience an annual return of 1.12% (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 borrowings. The Fund may be subject to certain restrictions on investments imposed by rating agencies or covenants with respect to any preferred shares or short term debt instruments it issues. These guidelines 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 February 28, 2018). 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 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.

(1)Includes interest expense on the borrowings under the SSB Agreement, accrued at interest rates in effect on February 28, 2018 of 2.24%, 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 or cap transactions to attempt to protect itself from increasing dividend or interest expenses on its leverage. 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 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 of the common shares.

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 1.44% and pay a fixed swap rate of 2.34% over the term of the swap, the swap would effectively increase Fund expenses and reduce Fund common share net earnings by approximately 0.25% as a percentage of net assets attributable to common shareholders and approximately 0.17% 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.

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. 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. 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.

FORWARD CURRENCY EXCHANGE TRANSACTIONS

The Fund may use forward currency exchange 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 in the statement of additional information under “Investment Objective and Policies — 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. 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 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 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 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.

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

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 common and preferred stocks, convertible securities and income-producing securities such as investment grade and below investment grade debt 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.

Equity Securities Risk. Equity investments are subject to greater fluctuations in market value than other asset classes as a result of such factors as the issuer’s business performance, investor perceptions, stock market trends and general economic conditions. Equity securities are subordinated to bonds and other debt instruments in a company’s capital structure in terms of priority to corporate income and liquidation payments. The Fund may invest in preferred stocks and convertible securities of any rating, including below investment grade.

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.

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 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 since the inception of the Fund 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 when necessary to meet its liquidity needs. 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. 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. 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.

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.

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.”

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 economics 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.

Currency Risk. The value of the securities denominated or quoted in foreign currencies may be adversely affected by fluctuations in the relative currency exchange rates and by exchange control regulations. The Fund’s investment performance may be negatively affected by a devaluation of a currency in which the Fund’s investments are denominated or quoted. Further, the Fund’s investment performance may be significantly affected, either positively or negatively, by currency exchange rates because the U.S. dollar value of securities denominated or quoted in another currency will increase or decrease in response to changes in the value of such currency in relation to the U.S. dollar.

Interest Rate Risk. Fixed income securities, including high yield securities, are subject to certain common 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; and

•the risks associated with rising interest rates may be particularly acute in the current market environment because market interest rates currently are at historically low levels. However, continued economic recovery, the end of the Federal Reserve Board’s quantitative easing program, and an increased likelihood of a rising interest rate environment increase the risk that interest rates will continue to rise in the near future.

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.

Leverage Risk. As of February 28, 2018, 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 total assets. 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.”

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

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

•fluctuations in the dividend rates on any preferred shares 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.

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 the 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.

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 rating agencies or covenants with respect to any preferred shares or short-term debt instruments it issues. These guidelines 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 and 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.

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.

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 issuer.

Liquidity Risk. The Fund may invest up to 15% of its managed assets in securities that, at the time of investment, are illiquid (i.e., securities that cannot be disposed of within 7 days in the ordinary course of business at approximately the value at which the Fund has valued the securities). The Fund may also invest without limit in Rule 144A Securities. Calamos, under the supervision of the Board of Trustees, will determine whether securities purchased under Rule 144A are illiquid (that is, not readily marketable) and thus subject to the Fund’s limit of

investing no more than 15% of its managed assets in illiquid securities. Investments in Rule 144A Securities could have the effect of increasing the amount of the Fund’s assets invested in illiquid securities if qualified institutional buyers are unwilling to purchase these Rule 144A Securities. 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.

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 will also be influenced by its “conversion price,” which is the market value of the underlying common stock that would be obtained if the convertible security were converted. A convertible security’s conversion price tends to increase as the price of the underlying common stock increases, and decrease as the price of the underlying common stock decreases. As the market price of the underlying common stock declines such that the conversion price is substantially below the investment value of the convertible security, 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. If the market price of the underlying common stock increases to a point where the conversion value approximates or exceeds the investment value, the price of the convertible security tends to be influenced more by the market price of 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.

Synthetic Convertible Instrument Risk. The value of a synthetic convertible instrument may respond differently to market fluctuations than a convertible security because a synthetic convertible instrument is composed of two or more separate instruments, 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.

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 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 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.

Forward Currency Exchange Contracts Risk. Forward contracts are contractual agreements to purchase or sell a specified currency at a specified future date (or within a specified time period) at a price set at the time of the contract. The Fund may not fully benefit from, or may lose money on, forward currency exchange transactions if changes in currency exchange rates do not occur as anticipated or do not correspond accurately to changes in the value of the Fund’s holdings.

Tax Risk. The Fund may invest in certain securities, such as certain convertible 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. See “Certain Federal Income Tax Matters.”

Certain of the Fund’s investment practices are 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) convert an ordinary loss or a deduction into a capital loss (the deductibility of which is more limited), (iv) cause the Fund to recognize income or gain without a corresponding receipt of cash, (v) adversely affect the timing as to when a purchase or sale of stock or securities is deemed to occur, and (vi) 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.

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.

Antitakeover Provisions. The Fund’s Agreement and Declaration of Trust and Bylaws 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, 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 preferred shares, see “Leverage Risk” above.

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.

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.

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 quasigovernmental 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.

Following the financial crisis that began in 2007, the Federal Reserve attempted to stabilize the U.S. economy and support the U.S. economic recovery by keeping the federal funds rate low. More recently, the Federal Reserve has terminated certain of its market support activities and began raising interest rates. The withdrawal of this support could negatively affect financial markets generally as well as reduce the value and liquidity of certain securities. Additionally, with continued economic recovery and the cessation of certain market support activities, the Portfolio may face a heightened level of interest rate risk as a result of a rise or increased volatility in interest rates. These policy changes may reduce liquidity for certain of the Portfolio’s investments, causing the value of the Portfolio’s investments and share price to decline. To the extent the Portfolio experiences high redemptions because of these policy changes, the Portfolio may experience increased portfolio turnover, which will increase the costs that the Portfolio incurs and may lower the Portfolio’s performance.

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 a Fund’s portfolio investments. In June 2016, the United Kingdom approved a referendum to leave the European Union (“EU”).

On March 29, 2017, the United Kingdom formally notified the European Council of its intention to leave the EU. As a result, the United Kingdom will remain a member state, subject to European law, with privileges to provide services under the single market directives for at least two years from that date. 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. The 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. See “Risk Factors — Fund Risks — Recent Market Events.”

Additional Risks to Common Shareholders

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

Interest Rate Transactions Risk. The Fund may enter into an interest rate swap or cap transaction to attempt to protect itself from increasing dividend or interest expenses on its leverage resulting from increasing short-term interest rates. 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 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.

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 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.

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.

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.

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.

Diminished Voting Power and Excess Cash Risk. The voting power of current shareholders will be diluted to the extent that current 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 and we may not participate in market advances to the same extent as if such proceeds were fully invested as planned.

Market Discount Risk. The Fund’s common shares have traded both at a premium and at a discount in relation to net asset value. 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 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