Prospectus by Investment Company - Form 497

Prospectus August 1, 2024

The fund listed above (the "Fund") is a series of the Calamos ETF Trust (the "Trust") and an exchange-traded fund ("ETF"). The Fund lists and principally trades its shares on the NYSE Arca, Inc. ("NYSE Arca" or the "Exchange").

The U.S. Securities and Exchange Commission ("SEC") has not approved or disapproved these securities or passed upon the accuracy or adequacy of this prospectus. Any representation to the contrary is a criminal offense.

As described in more detail in the Fund's summary, the Fund seeks to provide investment results that, before taking fees and expenses into account, match the positive price return of the SPDR^®​ S&P 500^®​ ETF Trust ("Underlying ETF") up to a predetermined upside cap (the "Cap"), while protecting against 100% of the Underlying ETF's losses (before fees and expenses), over a period of approximately one-year (the "Outcome Period").

• Upside Cap: A pre-determined upside return Cap that represents the maximum percentage return an investor can achieve from an investment in the Fund for an entire Outcome Period. The Cap is determined before fees and expenses. The Cap is expected to change at the beginning of each new Outcome Period.

• Capital Protection: Represents downside protection target equal to 100% of losses (before fees and expenses) of the Underlying ETF, over the Outcome Period. There is no guarantee the Fund will be successful in providing the sought-after downside protection.

• Outcome Period: The approximate one-year period over which the Fund seeks to produce the Capital Protected Target Outcome. The current Outcome Period is from August 1, 2024 through July 31, 2025. The Fund will not terminate after the conclusion of the Outcome Period. After the conclusion of the Outcome Period, another will begin.

• Together, the Upside Cap, Capital Protection, and Outcome Period makeup the Capital Protected Target Outcome (alternatively, the "Target Outcome").

• The Target Outcome may not be achieved, and investors may lose some or all of their money. The Fund is designed to achieve the Target Outcome only if an investor buys on the first day of the Outcome Period and holds the Fund until the end of the Outcome Period.

• If investors buy or sell on a date other than the start or end date of the Outcome Period, their returns will be different and they may incur losses in excess of the Capital Protection level (i.e., losses exceeding 0%) and they may not experience gains up to the Cap.

• Investors considering purchasing shares after the beginning of the Outcome Period or considering selling their shares prior to the end of the Outcome Period should visit the Fund's website at www.calamos.com for important information and considerations regarding the Fund's potential outcomes.

• In periods of extreme market volatility, or during market disruption events, the Fund's ability to offset investor losses via the Capital Protection or provide a return up to the stated upside Cap may be impaired.

• The Fund will not terminate upon reaching the end of an Outcome Period. Rather, the Fund will rebalance, entering into a new set of options positions, thereby establishing a new Outcome Period, with a new Cap, and reset Capital Protection.

• The Fund has characteristics unlike many traditional investment products and may not be suitable for all investors. The Fund is only appropriate for shareholders willing to bear losses, including some or all of their investment.

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Calamos S&P 500^®​ Structured Alt Protection ETF^TM​ - August

Investment Objective

Calamos S&P 500 Structured Alt Protection ETF - August (the "Fund") seeks to provide investment results that, before taking fees and expenses into account, match the positive price return of the SPDR^®​ S&P 500^®​ ETF Trust ("Underlying ETF") up to a cap of 8.74% (the "Cap"), while protecting against 100% of negative price return of the Underlying ETF (before fees and expenses), for the period from August 1, 2024 through July 31, 2025.

Fees and Expenses of the Fund

The following table describes the fees and expenses that you may pay if you buy, hold and sell shares of the Fund ("Fund Shares"). Investors may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in the tables and examples below.

Annual Fund Operating Expenses (ongoing expenses that you pay each year as a percentage of the value of your investments):

1 "Other Expenses" is an estimate based on the expenses the Fund expects to incur for the current fiscal year.

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, and then sell all of your Fund Shares at the end of those periods. The example also assumes that your investment has a 5% return each year and that the Fund's operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs, whether you sell or hold your Fund Shares, would be:

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund Shares are held in a taxable account. These costs, which are not reflected in Annual Fund Operating Expenses or in the example, affect the Fund's performance. Because the Fund has not yet commenced operations, portfolio turnover information is unavailable at this time.

Principal Investment Strategies

The Fund is an actively managed exchange-traded fund ("ETF") that is designed to provide investors with the opportunity to benefit from increases in the Underlying ETF's share price up to the stated cap over a specified period of time of approximately one-year (the "Outcome Period"), while providing protection against decreases in the Underlying ETF's share price over the same Outcome Period (before taking fees and expenses into account).

Under normal market conditions, the Fund will invest substantially all of its assets in FLexible EXchange Options ("FLEX Options") that reference the price performance of the SPDR^®​ S&P 500^®​ ETF Trust (the "Underlying ETF"). FLEX Options are customized equity or index option contracts that trade on an exchange but provide investors with the ability to customize key contract terms like exercise prices, styles and expiration dates.

Calamos S&P 500^®​ Structured Alt Protection ETF^TM​ - August

The Underlying ETF is an exchange-traded unit investment trust that uses a replication strategy, meaning it invests in as many of the stocks in the S&P 500^®​ Index as is practicable. PDR Services, LLC ("PDR") serves as the Underlying ETF's sponsor. The investment objective of the Underlying ETF is to seek to provide investment results that, before fees and expenses, correspond generally to the price and yield performance of the S&P 500^®​ Index. The Fund's performance will not reflect the payment of dividends by the Underlying ETF. See "The Underlying ETF" for more information.

The returns an investor will receive from an investment in the Fund have characteristics that are distinct from many other investment vehicles, including the Underlying ETF. It is important that you understand these characteristics before making an investment in the Fund.

The Fund uses FLEX Options to employ a capital protected target outcome strategy. Target outcome strategies seek to produce pre-determined investment outcomes based upon the performance of an underlying security or index. The pre-determined outcomes sought by the Fund, which include capital protection to absorb 100% of losses (before fees and expenses) in the Underlying ETF (the "Capital Protection") and upside participation to a stated cap (before fees and expenses) (the "Cap"), are based on the price performance of the Underlying ETF over an Outcome Period.

The outcomes the Fund seeks for investors that hold Fund Shares for an entire Outcome Period are as follows, though there can be no guarantee these results will be achieved:

• If the Underlying ETF appreciates over the Outcome Period, the combination of FLEX Options held by the Fund seeks to provide upside participation matching that of the Underlying ETF, up to a cap that is determined at the start of the Outcome Period.

• If the Underlying ETF decreases over the Outcome Period, the combination of FLEX Options held by the Fund seeks to provide protection against 100% of Underlying ETF losses, prior to taking into account the Fund's fees and expenses.

The Fund does not seek to provide capital protection against 100% of losses (before fees and expenses) of the Underlying ETF as of any time other than the end of the Outcome Period.

For the Outcome Period beginning on August 1, 2024 through July 31, 2025, the Cap is 8.74% and the Capital Protection is 100%. When the Fund's fees and expenses are taken into account, the Cap is 8.05% and the Capital Protection is 99.31%. The Cap and Capital Protection will be further reduced by any brokerage commissions, trading fees, taxes and extraordinary expenses not included in the Fund's management fee.

The current Outcome Period is from August 1, 2024 through July 31, 2025. The Fund will not terminate after the conclusion of the Outcome Period. After the conclusion of the Outcome Period, another will begin. On the first day of each new Outcome Period, the Fund resets by investing in a new set of FLEX Options that are designed to provide a new cap for the new Outcome Period. This means that the Cap will change for each Outcome Period based upon prevailing market conditions at the beginning of each Outcome Period. The capital protection will remain the same for each Outcome Period. The Capital Protection and Cap, and the Fund's value relative to each, should be considered before investing in the Fund. The Fund will be perpetually offered and not terminate after the current or any subsequent Outcome Period. Approximately one week prior to the end of an Outcome Period, the Fund's website will be updated to alert existing shareholders that the Outcome Period is approaching its conclusion and will disclose the anticipated Cap range for the next Outcome Period. See "Subsequent Outcome Periods" for more information.

Upon conclusion of the Outcome Period, the Fund will receive the cash value of all the FLEX Options it held for that Outcome Period. It will then invest in a new series of FLEX Options with an expiration date of approximately one year in the future, and a new Outcome Period will begin. Each FLEX Option's value is ultimately derived from the performance of the Underlying ETF's share price during that time. As the terms of the FLEX Options do not change during an Outcome Period, the outcomes, including the Cap and Capital Protection discussed below, will be measured to the Fund's net asset value ("NAV") on the first day of the Outcome Period.

The stated Cap and Capital Protection may only be realized by investors who continuously hold Fund Shares from the commencement of an Outcome Period until its conclusion. An investor who purchases Fund Shares other than on the first day of an Outcome Period and/or sells Fund Shares prior to the end of an Outcome Period may experience results that are very different from the target outcomes sought by the Fund for that Outcome Period. While the Cap and Capital Protection provide

Calamos S&P 500^®​ Structured Alt Protection ETF^TM​ - August

the intended outcomes only for investors that hold their Fund Shares throughout the complete term of the Outcome Period, an investor can expect the value of their Fund Shares to generally move in the same direction as the Underlying ETF during the Outcome Period. If investors buy or sell on a date other than the start or end date of the Outcome Period, their returns will be different and they may incur losses in excess of the Capital Protection level (i.e., losses exceeding 0%) and they may not experience gains up to the Cap. See "Capital Protection and Cap" for more information.

The Fund's website, www.calamos.com, provides information relating to the possible outcomes for an investor of an investment in the Fund on a daily basis, if purchased on that date and held through the end of the Outcome Period, including the Fund's value relative to the Cap and Capital Protection. Before purchasing Fund Shares, an investor should visit the Fund's website to review this information and understand the possible outcomes of an investment in Fund Shares on a particular day and held through the end of the Outcome Period.

The Fund's investment objective is not a fundamental policy, and therefore may be changed by the Board without shareholder approval.

The Fund seeks to generate returns that match the Underlying ETF, up to the Cap (discussed in detail below), while limiting downside losses. The hypothetical illustrations provided below are designed to illustrate the outcomes that the Fund seeks to provide for investors who hold Fund Shares for the entirety of the Outcome Period. The hypothetical examples set forth below do not represent the performance of the Fund and investors should not rely on the hypothetical examples shown below as an indication of the actual or future performance of the Fund. There is no guarantee that the Fund will be successful in its attempt to provide the target outcomes for an Outcome Period. The returns that the Fund seeks to provide do not include the costs associated with purchasing Fund Shares and certain expenses incurred by the Fund. In the payoff profile illustration, the dotted line represents the Underlying ETF's performance, and the solid line represents the return profile gross of fees and expenses sought by the Fund in relation to the Underlying ETF's indicated performance. The bar chart below represents the Fund's hypothetical intended return profile based upon the performance of the Underlying ETF.

Calamos S&P 500^®​ Structured Alt Protection ETF^TM​ - August

Explanation of diagram:

1. Calamos S&P 500 Structured Alt Protection ETF - August Participation Layer: The dotted grey line represents the first layer, which involves purchasing a near zero-strike (i.e., deep in-the-money) call on the reference asset, at a pre-determined strike to provide full participation to the price return of the underlying reference asset. In other words, the full price participation provided by this layer provides potential gains and losses that are tantamount to that of owning the underlying reference asset outright, except that this layer does not participate in the dividend yield of the underlying reference asset.

2. Capital Protection Layer: The solid grey line represents the second layer, which involves purchasing an at-the-money put option, which produces protection equal to 100% of losses (before fees and expenses) of the price return of the reference asset, over the Outcome Period.

3. Upside Participation Layer (the "Cap"): The solid black line illustrates the final layer, which involves selling an out-of-the-money call, thereby creating the upside cap. The strike price at which the call is sold is determined so that the combined net options purchase price is approximately equal to the underlying asset's current value. The cost of this layer is a credit equal to the price that would make the total package "no-cost" or fully financed.

The Fund is classified as "non-diversified" under the Investment Company Act of 1940, as amended (the "1940 Act").

Capital Protection and Cap

The Fund seeks to provide capital protection to absorb 100% of losses (before fees and expenses) of the Underlying ETF at the end of each Outcome Period. When the Fund's management fees are taken into account, the Capital Protection level is reduced to 99.31%. The Capital Protection level will be further reduced by any brokerage commissions, trading fees, taxes and extraordinary expenses not included in the Fund's management fee. If the Fund is required to increase its holdings of cash during the Outcome Period to pay fees and expenses incurred by the Fund, the Capital Protection level may be further reduced. The Fund does not seek to provide capital protection against 100% of losses (before fees and expenses) of the Underlying ETF as of any time other than the end of the Outcome Period.

During the Outcome Period, there may be periods of significant disparity between the Fund's NAV and the Underlying ETF's price performance. As the Underlying ETF price and the Fund's NAV change over the Outcome Period, an investor acquiring Fund Shares after the start of the Outcome Period will likely have a different return potential than an investor who purchased Fund Shares at the start of the Outcome Period. This is because while the Cap and Capital Protection for the Outcome Period

Calamos S&P 500^®​ Structured Alt Protection ETF^TM​ - August

are fixed levels that are calculated in relation to the Underlying ETF price and the Fund's NAV at the start of an Outcome Period and remain constant throughout the Outcome Period, an investor purchasing Fund Shares at market value during the Outcome Period likely purchased Fund Shares at a price that is different from the Fund's NAV at the start of the Outcome Period (i.e., the NAV that the Cap and Capital Protection reference). For example, if an investor purchases Fund Shares during an Outcome Period at a time when the Fund has increased in value from the value of the Fund on the first day of the Outcome Period (the "Initial Fund Value"), that investor's Cap will essentially be decreased by the amount of the increase in the Underlying ETF's value, and the capital protection will not set in until the Fund's NAV returns to its Initial Fund Value (i.e., a shareholder must experience losses prior to gaining the protection offered by the Fund's Capital Protection because the Fund must first decrease in value to its Initial Fund Value for the Outcome Period before subsequent losses will be protected by the Capital Protection). Conversely, if an investor purchases Fund Shares during an Outcome Period at a time when the Underlying ETF has decreased in value, the Fund's NAV may dip below the Initial Fund Value. However, in this scenario, that investor's potential gain could be larger than the Fund's Cap for the Outcome Period because the investor may experience the full gain if the Fund recovers the value it has lost from the first day of the Outcome Period through the date the investor purchased its Fund Shares plus any additional gains between the Initial Fund Value and the Cap. There is no guarantee that the Fund will recover such value or experience such gains. The Cap and capital protection relative to the Initial Fund Value, however, will not change over the Outcome Period.

While the Fund seeks to provide 100% protection against losses experienced by the Underlying ETF (before fees and expenses) for shareholders who hold Fund Shares for an entire Outcome Period, there is no guarantee it will successfully do so. If the Fund's NAV has increased significantly, a shareholder that purchases Fund Shares after the first day of an Outcome Period could lose their entire investment. An investment in the Fund is only appropriate for shareholders willing to bear those losses. There is no guarantee the capital protection and cap will be successful and a shareholder investing at the beginning of an Outcome Period could also lose their entire investment.

The returns of the Fund are subject to a cap for each Outcome Period, calculated (before fees and expenses) at the beginning of each Outcome Period. Unlike other investment products, the potential returns an investor can receive from the Fund are subject to a pre-determined upside return Cap that represents the maximum percentage return an investor can achieve from an investment in the Fund for an entire Outcome Period. If the Underlying ETF experiences any percentage gains over the amount of the Cap, Fund shareholders will not experience those gains. Therefore, regardless of the price return of the Underlying ETF, the Cap (net of fees) is the maximum return an investor can achieve from an investment in the Fund for that Outcome Period. The Cap is set on the first day of each Outcome Period. The Cap is provided prior to taking into account annual Fund management fees of 0.69% of the Fund's daily net assets, brokerage commissions, trading fees, taxes and any extraordinary expenses (such as unexpected litigation) incurred by the Fund. The pre-determined Cap applicable to an Outcome Period will vary based on prevailing market conditions at the time that the Cap is set, including interest rate levels, Underlying ETF volatility, and the relationship of puts and calls on the FLEX Options.

The Cap level is a result of the design of the Fund's principal investment strategy. To provide the Capital Protected Target Outcome, the Fund purchases and sells a series of put and call FLEX Options on or around the last business day of the month prior to the beginning of an Outcome Period. As the purchaser of these FLEX Options, the Fund is obligated to pay a premium to the seller of those FLEX Options. The Adviser will calculate the amount of premiums that the Fund will owe on the put options acquired to provide the Capital Protection and will then sell call FLEX Options with terms that entitle the Fund to receive premiums such that the net amount of premiums paid per unit of the Underlying ETF is approximately equal to the price per unit of shares of the Underlying ETF. The Cap is the strike price of those FLEX Options the Fund is selling. The Cap, and the Fund's value relative to it on any given day, should be considered before investing in the Fund. If an investor purchases Fund Shares during an Outcome Period, and the Fund has already increased in value above its Initial Fund Value for that Outcome Period to a level near the Cap, an investor purchasing Fund Shares will have limited to no gain potential for the remainder of the Outcome Period (because the investor's potential gain will be limited to the difference between the Fund's NAV on the date the investor purchased the Fund Shares and the Cap). However, the investor will remain vulnerable to significant downside risk because the investor will bear the losses between the price at which it purchased its Fund Shares and the Initial Fund Value for the Outcome Period before subsequent losses will be protected by the Capital Protection. If an

Calamos S&P 500^®​ Structured Alt Protection ETF^TM​ - August

investor buys Fund Shares when the price exceeds the Cap, an investor selling their shares at the end of the Outcome Period will not experience any gain regardless of the price return of the Underlying ETF.

There is no guarantee that the Fund will be successful in providing these investment outcomes for any Outcome Period, and an investor may experience returns on the Fund significantly below the Cap.

In periods of extreme market volatility or during market disruption events, the Fund's ability to offset investor losses through the use of the FLEX Options to achieve the stated Capital Protection, or provide a return up to the stated upside Cap may be impaired, resulting in an upside limit significantly below the Cap and downside protection significantly lower than full capital protection (i.e., losses greater than 0%), because the Fund may not be able to trade or exercise existing FLEX Options, or may not receive timely payment from its counterparties. An investor may lose their entire investment and an investment in the Fund is only appropriate for investors willing to bear those losses.

For each Outcome Period, the Fund will invest in both purchased and written put and call FLEX Options that reference the Underlying ETF. Because the value of the Fund is based on FLEX Options that reference the Underlying ETF and not the Underlying ETF directly, variations in the value of the FLEX Options impact the correlation between the Fund's NAV and the price of the Underlying ETF.

General Information about FLEX Options

FLEX Options are customizable exchange-traded option contracts guaranteed for settlement by the Options Clearing Corporation ("OCC"). The OCC guarantees performance by each of the counterparties to the FLEX Options, becoming the "buyer for every seller and the seller for every buyer," with the goal of protecting clearing members and options traders from counterparty risk. The OCC may make adjustments to FLEX Options for certain significant events, as more fully described in the Fund's Statement of Additional Information. Although guaranteed for settlement by the OCC, FLEX Options are still subject to counterparty risk with the OCC and subject to the risk that the OCC may fail to perform the settlement of the FLEX Options due to bankruptcy or other adverse reasons. The FLEX Options that the Fund will hold that reference the Underlying ETF will give the Fund the right or the obligation to either receive or deliver shares of the Underlying ETF, or the right or the obligation to either receive or deliver a cash payment on the option expiration date based upon the difference between the Underlying ETF's value and a strike price, depending on whether the option is a put or call option and whether the Fund purchases or sells the option. The FLEX Options held by the Fund are European style options, which are exercisable at the strike price only on the FLEX Option expiration date. The Fund will generally, under normal conditions, hold FLEX Options for each Outcome Period. The Fund will purchase call options (giving the Fund the right to receive shares of the Underlying ETF or a cash payment) and put options (giving the Fund the right to deliver shares of the Underlying ETF or a cash payment), while simultaneously selling (i.e., writing) call options (giving the Fund the obligation to deliver shares of the Underlying ETF or a cash payment). The Fund intends to structure the FLEX Options so that any amount owed by the Fund on the written FLEX Options will be covered by payouts at expiration from the purchased FLEX Options. As a result, the Fund expects the FLEX Options to be fully covered and no additional collateral will be necessary during the life of the Fund. The Fund receives premiums in exchange for the written FLEX Options and pays premiums in exchange for the purchased FLEX Options. The OCC and securities exchanges on which the FLEX Options are listed do not charge ongoing fees to writers or purchasers of the FLEX Options during their life for continuing to hold the option contracts but may charge transaction fees. Each of the FLEX Options purchased and sold throughout the Outcome Period will have the same terms, such as strike price and expiration date, as the FLEX Options purchased and sold on the first day of the Outcome Period. On the Flex Options expiration date, the Fund intends to sell the Flex Options prior to their expiration or cash-settle the Flex Options and use the resulting proceeds to purchase new Flex Options for the next Outcome Period.

The Underlying ETF

The Underlying ETF is an exchange-traded unit investment trust that uses a replication strategy, meaning it invests in as many of the stocks in the S&P 500^®​ Index as is practicable. PDR Services, LLC ("PDR") serves as the Underlying ETF's sponsor. The investment objective of the Underlying ETF is to seek to provide investment results that, before fees and expenses, correspond generally to the price and yield performance of the S&P 500^®​ Index (the "Index"). See below for a description of the Underlying ETF's principal investment strategies and risks. You can find the Underlying ETF's prospectus and other information

Calamos S&P 500^®​ Structured Alt Protection ETF^TM​ - August

about the ETF, including the statement of additional information and most recent reports to shareholders, online at https://us.spdrs.com/en/etf/spdr-sp-500-etf-SPY.

The summary information below regarding the Underlying ETF comes from its filings with the SEC. You are urged to refer to the SEC filings made by the Underlying ETF and to other publicly available information (e.g., the ETF's annual reports) to obtain an understanding of the ETF's business and financial prospects. The following description of the Underlying ETF's principal investment strategies was taken directly from the Underlying ETF's prospectus, dated January 26, 2024 ("SPY" refers to the Underlying ETF; other defined terms have been modified).

"SPY seeks to achieve its investment objective by holding a portfolio of the common stocks that are included in the Index (the "Portfolio"), with the weight of each stock in SPY's Portfolio substantially corresponding to the weight of such stock in the Index. In SPY's prospectus, the term "Portfolio Securities" refers to the common stocks that are actually held by SPY and make up SPY's Portfolio, while the term "Index Securities" refers to the common stocks that are included in the Index, as determined by the index provider, S&P Dow Jones Indices LLC ("S&P"). At any time, SPY's Portfolio will consist of as many of the Index Securities as is practicable. To maintain the correspondence between the composition and weightings of Portfolio Securities and Index Securities, State Street Global Advisors Trust Company (the "Trustee") or its parent company, State Street Bank and Trust Company ("SSBT") adjusts SPY's Portfolio from time to time to conform to periodic changes made by S&P to the identity and/or relative weightings of Index Securities in the Index. SPY's Trustee or SSBT aggregates certain of these adjustments and makes changes to SPY's Portfolio at least monthly, or more frequently in the case of significant changes to the Index. SPY may pay transaction costs, such as brokerage commissions, when it buys and sells securities (or "turns over" its Portfolio). Such transaction costs may be higher if there are significant rebalancings of Index Securities in the Index, which may also result in higher taxes when SPY's units are held in a taxable account. These costs, which are not reflected in SPY's estimated annual Trust ordinary operating expenses, affect SPY's performance. During the most recent fiscal year, SPY's portfolio turnover rate was 2% of the average value of its portfolio. SPY's portfolio turnover rate does not include securities received or delivered from processing creations or redemptions of SPY's units. Portfolio turnover will be a function of changes to the Index as well as requirements of SPY's trust agreement. ... Although SPY may fail to own certain Index Securities at any particular time, SPY generally will be substantially invested in Index Securities, which should result in a close correspondence between the performance of the Index and the performance of SPY. ... SPY does not hold or trade futures or swaps and is not a commodity pool. ... The Index includes five hundred (500) selected companies, all of which are listed on national stock exchanges and spans a broad range of major industries. ... Since 1968, the Index has been a component of the U.S. Commerce Department's list of Leading Indicators that track key sectors of the U.S. economy. Current information regarding the market value of the Index is available from market information services. The Index is determined, comprised and calculated without regard to SPY."

As of December 1, 2023, the Underlying ETF had significant investments in information technology companies.

Subsequent Outcome Periods

The Fund will alert existing shareholders to the new Cap at the beginning of each new Outcome Period in the following manner:

1. Approximately one week prior to the end of the current Outcome Period, the Fund will make a sticker filing that will alert existing shareholders that the Outcome Period is approaching its conclusion and disclose the anticipated Cap range for the next Outcome Period. This filing will be mailed to existing shareholders.

2. Following the close of business on the last day of the Outcome Period, the Fund will make a sticker filing that discloses the Fund's Cap for the next Outcome Period. This filing will be mailed to existing shareholders.

3. On the first day of the new Outcome Period, the Fund will file a full prospectus that incorporates the sticker filing from the previous evening which replaces the Caps/dates associated with the previous Outcome Period with the Caps/dates associated with the new Outcome Period. Correspondingly, the Fund will file a revised summary prospectus that reflects such changes.

The information referenced above will also be available on the Fund's website at www.calamos.com.

Calamos S&P 500^®​ Structured Alt Protection ETF^TM​ - August

Principal Risks

An investment in the Fund is subject to risks, and you could lose money on your investment in the Fund. There can be no assurance that the Fund will achieve its investment objective. You should not consider investing in the Fund if your investment objective differs from the Fund's investment objective or if you are not willing to accept the principal risks associated with an investment in the Fund. The risks associated with an investment in the Fund can increase during times of significant market volatility. Your investment in the Fund is not a deposit in a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency. The principal risks are presented in alphabetical order to facilitate finding particular risks and comparing them with other funds. Each risk summarized below is considered a "principal risk" of investing in the Fund, regardless of the order in which it appears. The principal risks of investing in the Fund include:

• Authorized Participant Concentration Risk - Only an Authorized Participant may engage in creation or redemption transactions directly with the Fund, and none of those Authorized Participants is obligated to engage in creation and/or redemption transactions. The Fund has a limited number of institutions that may act as Authorized Participants on an agency basis (i.e., on behalf of other market participants). To the extent that Authorized Participants exit the business or are unable to proceed with creation or redemption orders with respect to the Fund and no other Authorized Participant is able to step forward to create or redeem, Fund Shares may be more likely to trade at a premium or discount to NAV and possibly face trading halts or delisting. Authorized Participant concentration risk may be heightened for ETFs, such as the Fund, that invest in securities issued by non-U.S. issuers or other securities or instruments that have lower trading volumes.

• Cap Change Risk - A new Cap is established at the beginning of each Outcome Period and is dependent on prevailing market conditions at the time the Cap is established. As such, the Cap may rise or fall from one Outcome Period to the next and is unlikely to remain the same for consecutive Outcome Periods. Investors should monitor the changes in the Cap for each Outcome Period, information for which will be made available pursuant to the procedure outlined in the Fund's prospectus.

• Capital Protection Risk - There can be no guarantee that the Fund will be successful in its strategy to provide protection against 100% of Underlying ETF losses if the Underlying ETF's share price decreases over the duration of the Outcome Period. The Fund's strategy seeks to deliver returns that match those of the Underlying ETF (up to the Cap), while limiting downside losses, if Fund Shares are held at the time at which the Fund enters into the FLEX Options and held until those FLEX Options expire at the end of the Outcome Period. In the event an investor purchases Fund Shares after the FLEX Options were entered into or sells Fund Shares prior to the expiration of the FLEX Options, the Capital Protection that the Fund seeks to provide may not be available. If the Outcome Period has begun and the Underlying ETF has increased in value, the Capital Protection will not protect any decreases in the value of the Underlying ETF to the extent of such appreciation, and therefore an investor may experience losses from this appreciated value until the Fund reaches its original NAV from the commencement of the Outcome Period. Similarly, if an investor purchases Fund Shares after the commencement of the Outcome period and the Underlying ETF has increased in value, an investor purchasing Shares at that point will not benefit from the Capital Protection until the Underlying ETF's value decreases to its original value at the commencement of the Outcome Period. Accordingly, such investor will not receive the protection that the Fund seeks to provide until the Fund experiences losses that return it to its value at the commencement of the Outcome Period. If the FLEX Options (and therefore the Capital Protection) do not perform as expected, an investor may experience significant losses on its investment, including the loss of its entire investment.

• Capped Upside Risk - The Fund's strategy seeks to provide returns that are subject to the Cap. In the event that the Underlying ETF experiences gains in excess of the Cap for the Outcome Period, the Fund will not participate in, and will underperform the Underlying ETF to the extent of, those gains beyond the Cap. The Fund's strategy seeks to deliver returns that match those of the Underlying ETF (up to the Cap), while protecting against the entirety of downside losses of the Underlying ETF, if Fund Shares are held at the time at which the Fund enters into the FLEX Options and held until those FLEX Options expire at the end of the Outcome Period. In the event an investor purchases Fund Shares after the FLEX Options were entered into, there may be little or no ability for that investor to experience an investment gain on their Fund Shares (and such investor may be subjected to potential losses between that Fund Share price and the Fund's

Calamos S&P 500^®​ Structured Alt Protection ETF^TM​ - August

NAV at the commencement of the Outcome Period). Further, because the FLEX Options are designed to produce returns that match the price return of the Underlying ETF (subject to the Cap) on the last day of the Outcome Period, if an investor sells Fund Shares prior to the expiration date of the FLEX Options such investor may sell at a point where the Fund's performance does not match the performance of the Underlying ETF over the Outcome Period, and therefore may sell at a point where the Fund has underperformed the Underlying ETF.

• Cash Holdings Risk - To the extent the Fund holds cash positions, the Fund risks achieving lower returns and potential lost opportunities to participate in market appreciation which could negatively impact the Fund's performance and ability to achieve its investment objective.

• Clearing Member Default Risk - Transactions in some types of derivatives, including FLEX Options, are required to be centrally cleared ("cleared derivatives"). In a transaction involving cleared derivatives, the Fund's counterparty is a clearing house, such as the OCC, rather than a bank or broker. Since the Fund is not a member of clearing houses and only members of a clearing house ("clearing members") can participate directly in the clearing house, the Fund will hold cleared derivatives through accounts at clearing members. In cleared derivatives positions, the Fund will make payments (including margin payments) to, and receive payments from, a clearing house through their accounts at clearing members. Customer funds held at a clearing organization in connection with any option contracts are held in a commingled omnibus account and are not identified to the name of the clearing member's individual customers. As a result, assets deposited by the Fund with any clearing member as margin for its FLEX Options may, in certain circumstances, be used to satisfy losses of other clients of the Fund's clearing member. In addition, although clearing members guarantee performance of their clients' obligations to the clearing house, there is a risk that the assets of the Fund might not be fully protected in the event of the clearing member's bankruptcy. The Fund is also subject to the risk that a limited number of clearing members are willing to transact on the Fund's behalf, which heightens the risks associated with a clearing member's default. If a clearing member defaults the Fund could lose some or all of the benefits of a transaction entered into by the Fund with the clearing member. The loss of a clearing member for the Fund to transact with could result in increased transaction costs and other operational issues that could impede the Fund's ability to implement its investment strategy. If the Fund cannot find a clearing member to transact with on the Fund's behalf, the Fund may be unable to effectively implement its investment strategy.

• Correlation Risk - The FLEX Options held by the Fund will be exercisable at the strike price only on their expiration date. Prior to the expiration date, the value of the FLEX Options will be determined based upon market quotations or using other recognized pricing methods, consistent with the Fund's valuation policy. Because a component of the FLEX option's value will be affected by, among other things, changes in the Underlying ETF's share price, changes in interest rates, changes in the actual and implied volatility of the Underlying ETF's share price and the remaining time until the FLEX Options expire, the value of the Fund's FLEX Options positions is not anticipated to increase or decrease at the same rate as the Underlying ETF's share price, and it is possible they may move in different directions, and as a result, the Fund's NAV may not increase or decrease at the same rate as the Underlying ETF's share price. The Fund's strategy is designed to produce the outcomes upon the expiration of the FLEX Options on the last business day of the Outcome Period, and it should not be expected that the outcomes will be provided at any point other than the end of the Outcome Period.

• Costs of Buying and Selling Fund Shares - Due to the costs of buying or selling Fund Shares, including brokerage commissions imposed by brokers and bid/ask spreads, frequent trading of Fund Shares may significantly reduce investment results and an investment in Fund Shares may not be advisable for investors who anticipate regularly making small investments.

• Derivatives Risk - Derivatives are instruments, such as options, futures and forward foreign currency contracts, whose value is derived from that of other assets, rates or indices. The use of derivatives for non-hedging purposes may be considered more speculative than other types of investments. Derivatives can be used for hedging (attempting to reduce risk by offsetting one investment position with another) or non-hedging purposes. Hedging with derivatives may increase expenses, and there is no guarantee that a hedging strategy will work. While hedging can reduce or eliminate losses, it can also reduce or eliminate gains. In addition, derivative instruments are subject to counterparty risk, meaning that the party with whom the Fund enters into a derivative transaction may experience a significant credit event and/or may be

Calamos S&P 500^®​ Structured Alt Protection ETF^TM​ - August

unwilling or unable to make timely settlement payments or otherwise honor its obligations. Changes in the value of a derivative may not correlate perfectly with the underlying asset, rate or index, and the Fund could lose more than the principal amount invested.

• Equity Securities Risk - The securities markets are volatile, and the market prices of the Underlying ETF's securities may decline generally. The price of equity securities fluctuates based on changes in a company's financial condition and overall market and economic conditions. If the market prices of the securities owned by the Underlying ETF fall, the value of your investment in the Fund will decline.

• FLEX Options Risk - The Fund may invest in FLEX Options issued and guaranteed for settlement by The Options Clearing Corporation ("OCC"). FLEX Options are customized option contracts that trade on an exchange but provide investors with the ability to customize key contract terms like strike price, style and expiration date while achieving price discovery in competitive, transparent auctions markets and avoiding the counterparty exposure of over-the-counter options positions. Like traditional exchange-traded options, FLEX Options are guaranteed for settlement by the OCC, a market clearinghouse that guarantees performance by counterparties to certain derivatives contracts. The Fund bears the risk that the OCC will be unable or unwilling to perform its obligations under the FLEX Options contracts. Additionally, FLEX Options may be illiquid, and in such cases, the Fund may have difficulty closing out certain FLEX Options positions at desired times and prices. The FLEX Options held by the Fund will be exercisable at the strike price only on their expiration date. Prior to the expiration date, the value of the FLEX Options will be determined based upon market quotations or using other recognized pricing methods. The value of the FLEX Options prior to the expiration date may vary because of related factors other than the value of the reference asset. Factors that may influence the value of the FLEX Options, other than gains or losses in the reference asset, may include interest rate changes, changing supply and demand, decreased liquidity of the FLEX Options and changing volatility levels of the reference asset. In connection with the creation and redemption of Fund Shares, to the extent market participants are not willing or able to enter into FLEX Option transactions with the Fund at prices that reflect the market price of the Fund Shares, the Fund's NAV and, in tum the share price of the Fund, could be negatively impacted. The Fund may experience substantial downside from specific FLEX Option positions and certain FLEX Option positions may expire worthless.

• Investment Timing Risk - An investor who purchases Fund Shares other than on the first day of the options package and/or sells Fund Shares before the options package expires may not experience the 100% downside protection or upside participation in the Underlying ETF. The Fund's downside protection and upside participation of the Underlying ETF may only be available for investors who hold Fund Shares throughout the complete term of the options package. An investor can expect their Fund Shares to move generally in the same direction as the Underlying ETF during the one-year options package. However, Fund Shares may not experience the same price movement as the price movement of the Underlying ETF. During the duration of the option package, there may be periods of significant disparity between the Fund's NAV and the Underlying ETF's price performance. For example, if an investor purchases Fund Shares during an options package period at a time when the Underlying ETF's share price has increased from its price at the beginning of the options package period, the investor may not be 100% protected against Underlying ETF downside losses. In addition, if an investor purchases Fund Shares during an options package period at a time when the Underlying ETF's share price has increased from its price at the beginning of the options package period, that investor's cap will essentially be decreased from the stated Cap by the amount of the increase in the Underlying ETF's value.

• Large-Capitalization Investing Risk - Large-capitalization stocks as a group could fall out of favor with the market, which may cause the Fund to underperform funds that focus on other types of stocks. In addition, larger, more established companies may be unable to respond quickly to new competitive challenges such as changes in technology and consumer preferences. Many larger companies also may not be able to attain the high growth rate of successful smaller companies, especially during extended periods of economic expansion.

• Liquidity Risk - Liquidity risk exists when particular investments are difficult to purchase or sell. The Fund's investments in illiquid securities may reduce the returns of the Fund because it may be unable to sell the illiquid securities at an advantageous time or price.

Calamos S&P 500^®​ Structured Alt Protection ETF^TM​ - August

• Liquidity Risk - FLEX Options - In the event that trading in the underlying FLEX Options is limited or absent, the value of the Fund's FLEX Options may decrease. There is no guarantee that a liquid secondary trading market will exist for the FLEX Options. The trading in FLEX Options may be less deep and liquid than the market for certain other securities, including certain non-customized option contracts. In a less liquid market for the FLEX Options, terminating the FLEX Options may require the payment of a premium or acceptance of a discounted price and may take longer to complete. Additionally, the liquidation of a large number of FLEX Options may more significantly impact the price in a less liquid market. Further, the Fund requires a sufficient number of participants to facilitate the purchase and sale of options on an exchange to provide liquidity to the Fund for its FLEX Option positions. A less liquid trading market may adversely impact the value of the FLEX Options and the value of your investment.

• Market Maker Risk - If the Fund has lower average daily trading volumes, it may rely on a small number of third-party market makers to provide a market for the purchase and sale of Fund Shares. Any trading halt or other problem relating to the trading activity of these market makers could result in a dramatic change in the spread between the Fund's net asset value and the price at which the Fund Shares are trading on the Exchange, which could result in a decrease in value of the Fund Shares. In addition, decisions by market makers or authorized participants to reduce their role or step away from these activities in times of market stress could inhibit the effectiveness of the arbitrage process in maintaining the relationship between the underlying values of the Fund's portfolio securities and the Fund's market price. This reduced effectiveness could result in Fund Shares trading at a discount to net asset value and also in greater than normal intra-day bid-ask spreads for Fund Shares.

• Market Risk - The risk that the securities markets will increase or decrease in value is considered market risk and applies to any security. If there is a general decline in the stock or fixed-income market, it is possible your investment may lose value regardless of the individual results of the companies in which the Fund invests.

• New Fund Risk - The Fund is a recently organized investment company with a limited operating history. As a result, prospective investors have a limited track record or history on which to base their investment decision.

• Non-Diversification Risk - The Fund is classified as "non-diversified" under the 1940 Act. As a result, the Fund is only limited as to the percentage of its assets which may be invested in the securities of any one issuer by the diversification requirements imposed by the Internal Revenue Code of 1986, as amended (the "Code").

• Options Risk - The Fund's ability to close out its position as a purchaser or seller of an over-the-counter or exchange-listed put or call option is dependent, in part, upon the liquidity of the options market. There are significant differences between the securities and options markets that could result in an imperfect correlation among these markets, causing a given transaction not to achieve its objectives. The Fund's ability to utilize options successfully will depend on the ability of the Fund's investment adviser to predict pertinent market movements, which cannot be assured. The Fund may also purchase or write over-the-counter put or call options, which involves risks different from, and possibly greater than, the risks associated with exchange-listed put or call options. Over-the-counter put or call options may expose the Fund to the risk that a counterparty may be unable or unwilling to perform according to a contract, and that any deterioration in a counterparty's creditworthiness could adversely affect the instrument. In addition, the Fund may be exposed to a risk that losses may exceed the amount originally invested.

• Premium-Discount Risk - Fund Shares may trade above or below their NAV. The market prices of Fund Shares will generally fluctuate in accordance with changes in NAV as well as the relative supply of, and demand for, Fund Shares on the Exchange. The trading price of Fund Shares may deviate significantly from NAV during periods of market volatility.

• Secondary Market Trading Risk - Investors buying or selling Fund Shares in the secondary market will pay brokerage commissions or other charges imposed by brokers as determined by that broker. Brokerage commissions are often a fixed amount and may be a significant proportional cost for investors seeking to buy or sell relatively small amounts of Fund Shares. Although the Fund Shares are listed on the Exchange, there can be no assurance that an active or liquid trading market for them will develop or be maintained. In addition, trading in Fund Shares on the Exchange may be halted.

• Sector Risk - To the extent the Underlying ETF invests a significant portion of its assets in a particular sector, a greater portion of the Fund's performance may be affected by the general business and economic conditions affecting that

Calamos S&P 500^®​ Structured Alt Protection ETF^TM​ - August

sector. Each sector may share economic risk with the broader market, however there may be economic risks specific to each sector. As a result, returns from those sectors may trail returns from the overall stock market, and it is possible that the Underlying ETF may underperform the broader market.

• Tax Risk - The Fund intends to elect and to qualify each year to be treated as a regulated investment company ("RIC") under Subchapter M of the Internal Revenue Code of 1986, as amended (the "Code"). The federal income tax treatment of the securities in which the Fund may invest, including the Fund's option strategy, may not be clear or may be subject to recharacterization by the Internal Revenue Service. It could be more difficult to comply with the tax requirements applicable to RICs if the tax characterization of investments or the tax treatment of the income from such investments were successfully challenged by the Internal Revenue Service. Any such failure to comply with the rules applicable to RICs could cause the Fund to fail to qualify as such. To qualify and maintain its status as a RIC, the Fund must meet certain income, diversification and distributions tests. For purposes of the diversification test, the identification of the issuer (or, in some cases, issuers) of a particular Fund investment can depend on the terms and conditions of that investment. In particular, there is no published Internal Revenue Service guidance or case law on how to determine the "issuer" of certain derivatives that the Fund will enter into. Based upon the language in the legislative history, the Fund intends to treat the issuer of an equity option as the referenced asset, which and to treat any income it may derive from an equity option as "qualifying income" under the provisions of the Code applicable to RICs. In the case of FLEX Options, as the referenced asset, which, assuming the referenced asset qualifies as a RIC, treating the issuer as the referenced asset would allow the Fund to count the FLEX Options as automatically diversified investments under the RIC diversification requirements. If the income is not qualifying income or the issuer of equity options, including FLEX Options. is not appropriately the referenced asset, the Fund may not qualify, or may be disqualified, as a RIC. If the Fund does not qualify as a RIC for any taxable year and certain relief provisions are not available, the Fund's taxable income will be subject to tax at the Fund level and to a further tax at the shareholder level when such income is distributed.

The Fund's investments in offsetting positions with respect to the Underlying ETF may affect the character of gains or losses realized by the Fund under the Code's "straddle" rules and may increase the amount of short-term capital gain realized by the Fund. Certain options the Fund holds may not qualify as "Section 1256 contracts" under Section 1256 of the Code, and disposition of such options will likely result in short-term or long-term capital gains or losses depending on the holding period.

There is a risk that if the offsetting FLEX Options are held by a single person that the IRS may take the position that the FLEX Options, viewed together, should be treated as a single debt instrument for federal tax purposes. The result of such a position would be that the Fund would fail the RIC diversification tests causing the RIC to be taxed as a C corporation, unless certain cure rights based upon reasonable cause may apply. The Fund has obtained an opinion of tax counsel that the FLEX Options should not be collapsed into a single instrument. However, such an opinion is not binding upon the IRS or the courts.

• Trading Issues Risk - Trading in Fund Shares on the Exchange may be halted due to market conditions or for reasons that, in the view of the Exchange, make trading in shares inadvisable. In addition, trading in Fund Shares on the Exchange is subject to trading halts caused by extraordinary market volatility pursuant to the Exchange's "circuit breaker" rules. There can be no assurance that the requirements of the Exchange necessary to maintain the listing of the Fund will continue to be met or will remain unchanged. The Fund may have difficulty maintaining its listing on the Exchange in the event the Fund's assets are small, the Fund does not have enough shareholders, or if the Fund is unable to proceed with creation and/or redemption orders.

• Underlying ETF Risk - The Fund invests in FLEX Options that reference an ETF, which subjects the Fund to certain of the risks of owning shares of an ETF as well as the types of instruments in which the Underlying ETF invests. The value of an ETF will fluctuate over time based on fluctuations in the values of the securities held by the ETF, which may be affected by changes in general economic conditions, expectations for future growth and profits, interest rates and the supply and demand for those securities. In addition, ETFs are subject to absence of an active market risk, premium/discount risk, tracking error risk and trading issues risk. Brokerage, tax and other expenses may negatively impact the performance of the Underlying ETF and, in turn, the value of the Fund's shares. An ETF that tracks an index may not exactly match the

Calamos S&P 500^®​ Structured Alt Protection ETF^TM​ - August

performance of the index due to cash drag, differences between the portfolio of the ETF and the components of the index, expenses and other factors.

• Valuation Risk - During periods of reduced market liquidity or in the absence of readily available market quotations for the holdings of the Fund, the ability of the Fund to value the FLEX Options may become more difficult. In market environments where there is reduced availability of reliable objective pricing data, the judgment of the Fund's investment adviser in determining the fair value of the security may play a greater role. While such determinations may be made in good faith, it may nevertheless be more difficult for the Fund to accurately assign a daily value.

Fund Performance

The Fund had not commenced operations as of the date of this prospectus. Once available, the Fund's performance information, and information that gives some indication of the risks of an investment in the Fund by comparing the Fund's performance with a broad measure of market performance, will be available on the Fund's website at: www.calamos.com. Past performance (before and after taxes) is not an indication of future performance.

Investment Adviser

Calamos Advisors LLC ("Calamos Advisors" or the "Adviser")

Portfolio Managers

Other Important Information Regarding Fund Shares

Portfolio Holdings. The Fund's portfolio holdings are disclosed on its website daily after the close of trading on the Exchange and prior to the opening of trading on the Exchange the following day. A description of the Fund's policies and procedures with respect to the disclosure of such Fund's portfolio holdings is available in the Fund's Statement of Additional Information ("SAI").

Premium/Discount Information. Information about the premiums and discounts at which the Fund's Shares have traded will be available at www.calamos.com.

Purchase and Sale of Fund Shares

The Fund will issue (or redeem) Fund Shares to certain institutional investors (typically market makers or other broker-dealers) only in large blocks of Fund Shares known as "Creation Units." Creation Unit transactions are conducted in exchange for the deposit or delivery of a designated portfolio of in-kind securities and/or cash.

Individual Fund Shares may only be purchased and sold on the Exchange, other national securities exchanges, electronic crossing networks and other alternative trading systems through your broker-dealer at market prices. Because Fund Shares trade at market prices rather than at net asset value ("NAV"), Fund Shares may trade at a price greater than NAV (premium) or less than NAV (discount). When buying or selling Fund Shares in the secondary market, you may incur costs attributable to the difference between the highest price a buyer is willing to pay to purchase Fund Shares (bid) and the lowest price a seller is willing to accept for Fund Shares (ask) (the "bid-ask spread"). Recent information regarding the Fund's NAV, market price, premiums and discounts, and bid-ask spreads is available at https://www.calamos.com/.

Tax Information

Net investment income and capital gains distributions you receive from the Fund generally are subject to federal income taxes and may also be subject to state and local taxes. The Fund intends to distribute net investment income and capital gains, if any, at least annually.

Payments to Broker-Dealers and Other Financial Intermediaries

If you purchase shares of the Fund through a broker-dealer or other financial intermediary (such as a bank), such Fund and its related companies may pay the intermediary for the sale of Fund Shares and related services. These payments may create a conflict of interest by influencing the broker-dealer or other intermediary and your salesperson to recommend the Fund over another investment. Ask your salesperson or visit your financial intermediary's website for more information.

Additional Information About Investment Strategies
and Related Risks

The Fund's investment objective and each of the policies described herein are non-fundamental policies that may be changed by the Board of Trustees of the Trust (the "Board") without shareholder approval. The Fund may liquidate and terminate at any time without shareholder approval.

What are the investment objectives and principal strategies for the Fund?

The Fund is an actively managed exchange-traded fund ("ETF") that is designed to provide investors with the opportunity to benefit from increases in the Underlying ETF's share price up to the stated cap over a specified period of time of approximately one-year (the "Outcome Period"), while providing protection against decreases in the Underlying ETF's share price over the same Outcome Period (before taking fees and expenses into account).

Under normal market conditions, the Fund will invest substantially all of its assets in FLexible EXchange Options ("FLEX Options") that reference the price performance of the SPDR^®​ S&P 500^®​ ETF Trust (the "Underlying ETF"). FLEX Options are customized equity or index option contracts that trade on an exchange but provide investors with the ability to customize key contract terms like exercise prices, styles and expiration dates.

The Underlying ETF is an exchange-traded unit investment trust that uses a replication strategy, meaning it invests in as many of the stocks in the S&P 500^®​ Index as is practicable. PDR Services, LLC ("PDR") serves as the Underlying ETF's sponsor. The investment objective of the Underlying ETF is to seek to provide investment results that, before fees and expenses, correspond generally to the price and yield performance of the S&P 500^®​ Index. The Fund's performance will not reflect the payment of dividends by the Underlying ETF. See "The Underlying ETF" for more information.

The returns an investor will receive from an investment in the Fund have characteristics that are distinct from many other investment vehicles, including the Underlying ETF. It is important that you understand these characteristics before making an investment in the Fund.

The Fund uses FLEX Options to employ a capital protected target outcome strategy. Target outcome strategies seek to produce pre-determined investment outcomes based upon the performance of an underlying security or index. The pre-determined outcomes sought by the Fund, which include capital protection to absorb 100% of losses (before fees and expenses) in the Underlying ETF (the "Capital Protection") and upside participation to a stated cap of 8.74% (before fees and expenses) (the "Cap"), are based on the price performance of the Underlying ETF over an approximate one-year period (the "Outcome Period").

The outcomes the Fund seeks for investors that hold Fund Shares for an entire Outcome Period are as follows, though there can be no guarantee these results will be achieved:

• If the Underlying ETF appreciates over the Outcome Period, the combination of FLEX Options held by the Fund seeks to provide upside participation matching that of the Underlying ETF, up to a Cap that is determined at the start of the Outcome Period.

• If the Underlying ETF decreases over the Outcome Period, the combination of FLEX Options held by the Fund seeks to provide protection against 100% of Underlying ETF losses, prior to taking into account the Fund's fees and expenses.

The Fund does not seek to provide capital protection against 100% of losses (before fees and expenses) of the Underlying ETF as of any time other than the end of the Outcome Period.

For the Outcome Period beginning on August 1, 2024 through July 31, 2025, the Cap is 8.74% and the Capital Protection is 100%. When the Fund's fees and expenses are taken into account, the Cap is 8.05% and the Capital Protection is 99.31%. The Cap and Capital Protection will be further reduced by any brokerage commissions, trading fees, taxes and extraordinary expenses not included in the Fund's management fee.

The current Outcome Period is from August 1, 2024 through July 31, 2025. The Fund will not terminate after the conclusion of the Outcome Period. After the conclusion of the Outcome Period, another will begin. On the first day of each new Outcome Period, the Fund resets by investing in a new set of FLEX Options that are designed to provide a new cap for the new Outcome

Additional Information About Investment Strategies and Related Risks

Period. This means that the Cap will change for each Outcome Period based upon prevailing market conditions at the beginning of each Outcome Period. The capital protection will remain the same for each Outcome Period. The Capital Protection and Cap, and the Fund's value relative to each, should be considered before investing in the Fund. The Fund will be perpetually offered and not terminate after the current or any subsequent Outcome Period. Approximately one week prior to the end of an Outcome Period, the Fund's website will be updated to alert existing shareholders that the Outcome Period is approaching its conclusion and will disclose the anticipated Cap range for the next Outcome Period. See "Subsequent Outcome Periods" for more information.

Upon conclusion of the Outcome Period, the Fund will receive the cash value of all the FLEX Options it held for that Outcome Period. It will then invest in a new series of FLEX Options with an expiration date of approximately one year in the future, and a new Outcome Period will begin. Each FLEX Option's value is ultimately derived from the performance of the Underlying ETF's share price during that time. As the terms of the FLEX Options do not change during an Outcome Period, the outcomes, including the Cap and 100% Capital Protection discussed below, will be measured to the Fund's net asset value ("NAV") on the first day of the Outcome Period.

The stated Cap and Capital Protection may only be realized by investors who continuously hold Fund Shares from the commencement of an Outcome Period until its conclusion. An investor who purchases Fund Shares other than on the first day of an Outcome Period and/or sells Fund Shares prior to the end of an Outcome Period may experience results that are very different from the target outcomes sought by the Fund for that Outcome Period. While the Cap and Capital Protection provide the intended outcomes only for investors that hold their Fund Shares throughout the complete term of the Outcome Period, an investor can expect the value of their Fund Shares to generally move in the same direction as the Underlying ETF during the Outcome Period. If investors buy or sell on a date other than the start or end date of the Outcome Period, their returns will be different and they may incur losses in excess of the Capital Protection level (i.e., losses exceeding 0%) and they may not experience gains up to the Cap. See "Capital Protection and Cap" for more information.

The Fund's website, www.calamos.com, provides information relating to the possible outcomes for an investor of an investment in the Fund on a daily basis, if purchased on that date and held through the end of the Outcome Period, including the Fund's value relative to the Cap and Capital Protection. Before purchasing Fund Shares, an investor should visit the Fund's website to review this information and understand the possible outcomes of an investment in Fund Shares on a particular day and held through the end of the Outcome Period.

The Fund's investment objective is not a fundamental policy, and therefore may be changed by the Board without shareholder approval.

The Fund seeks to generate returns that match the Underlying ETF, up to the Cap (discussed in detail below), while limiting downside losses. The hypothetical illustrations provided below are designed to illustrate the outcomes that the Fund seeks to provide for investors who hold Fund Shares for the entirety of the Outcome Period. The hypothetical examples set forth below do not represent the performance of the Fund and investors should not rely on the hypothetical examples shown below as an indication of the actual or future performance of the Fund. There is no guarantee that the Fund will be successful in its attempt to provide the target outcomes for an Outcome Period. The returns that the Fund seeks to provide do not include the costs associated with purchasing Fund Shares and certain expenses incurred by the Fund. In the payoff profile illustration, the dotted line represents the Underlying ETF's performance, and the solid line represents the return profile gross of fees and expenses sought by the Fund in relation to the Underlying ETF's indicated performance. The bar chart below represents the Fund's hypothetical intended return profile based upon the performance of the Underlying ETF.

Additional Information About Investment Strategies and Related Risks

Explanation of diagram:

1. Calamos S&P 500 Structured Alt Protection ETF - August Participation Layer: The dotted grey line represents the first layer, which involves purchasing a near zero-strike (i.e., deep in-the-money) call on the reference asset, at a pre-determined strike to provide full participation to the price return of the underlying reference asset. In other words, the full price participation provided by this layer provides potential gains and losses that are tantamount to that of owning the underlying reference asset outright, except that this layer does not participate in the dividend yield of the underlying reference asset.

2. Capital Protection Layer: The solid grey line represents the second layer, which involves purchasing an at-the-money put option, which produces protection equal to 100% of losses (before fees and expenses) of the price return of the reference asset, over the Outcome Period.

3. Upside Participation Layer (the "Cap"): The solid black line illustrates the final layer, which involves selling an out-of-the-money call, thereby creating the upside cap. The strike price at which the call is sold is determined so that the combined net options purchase price is approximately equal to the underlying asset's current value. The cost of this layer is a credit equal to the price that would make the total package "no-cost" or fully financed.

Additional Information About Investment Strategies and Related Risks

The Fund is classified as "non-diversified" under the Investment Company Act of 1940, as amended (the "1940 Act").

Capital Protection and Cap

The Fund seeks to provide capital protection to absorb 100% of losses (before fees and expenses) of the Underlying ETF at the end of each Outcome Period. When the Fund's management fees are taken into account, the Capital Protection level is reduced to 99.31%. The Capital Protection level will be further reduced by any brokerage commissions, trading fees, taxes and extraordinary expenses not included in the Fund's management fee. If the Fund is required to increase its holdings of cash during the Outcome Period to pay fees and expenses incurred by the Fund, the Capital Protection level may be further reduced. The Fund does not seek to provide capital protection against 100% of losses (before fees and expenses) of the Underlying ETF as of any time other than the end of the Outcome Period.

During the Outcome Period, there may be periods of significant disparity between the Fund's NAV and the Underlying ETF's price performance. As the Underlying ETF price and the Fund's Net Asset Value ("NAV") change over the Outcome Period, an investor acquiring Fund Shares after the start of the Outcome Period will likely have a different return potential than an investor who purchased Fund Shares at the start of the Outcome Period. This is because while the Cap and Capital Protection for the Outcome Period are fixed levels that are calculated in relation to the Underlying ETF price and the Fund's NAV at the start of an Outcome Period and remain constant throughout the Outcome Period, an investor purchasing Fund Shares at market value during the Outcome Period likely purchased Fund Shares at a price that is different from the Fund's NAV at the start of the Outcome Period (i.e., the NAV that the Cap and Capital Protection reference). For example, if an investor purchases Fund Shares during an Outcome Period at a time when the Fund has increased in value from the value of the Fund on the first day of the Outcome Period (the "Initial Fund Value"), that investor's Cap will essentially be decreased by the amount of the increase in the Underlying ETF's value, and the capital protection will not set in until the Fund's NAV returns to its Initial Fund Value (i.e., a shareholder must experience losses prior to gaining the protection offered by the Fund's Capital Protection because the Fund must first decrease in value to its Initial Fund Value for the Outcome Period before subsequent losses will be protected by the Capital Protection). Conversely, if an investor purchases Fund Shares during an Outcome Period at a time when the Underlying ETF has decreased in value, the Fund's NAV may dip below the Initial Fund Value. However, in this scenario, that investor's potential gain could be larger than the Fund's Cap for the Outcome Period because the investor may experience the full gain if the Fund recovers the value it has lost from the first day of the Outcome Period through the date the investor purchased its Fund Shares plus any additional gains between the Initial Fund Value and the Cap. There is no guarantee that the Fund will recover such value or experience such gains. The Cap and capital protection relative to the Initial Fund Value, however, will not change over the Outcome Period.

Additional Information About Investment Strategies and Related Risks

While the Fund seeks to provide 100% protection against losses experienced by the Underlying ETF (before fees and expenses) for shareholders who hold Fund Shares for an entire Outcome Period, there is no guarantee it will successfully do so. If the Fund's NAV has increased significantly, a shareholder that purchases Fund Shares after the first day of an Outcome Period could lose their entire investment. An investment in the Fund is only appropriate for shareholders willing to bear those losses. There is no guarantee the capital protection and cap will be successful and a shareholder investing at the beginning of an Outcome Period could also lose their entire investment.

The returns of the Fund are subject to a cap for each Outcome Period, calculated (before fees and expenses) at the beginning of each Outcome Period. Unlike other investment products, the potential returns an investor can receive from the Fund are subject to a pre-determined upside return Cap that represents the maximum percentage return an investor can achieve from an investment in the Fund for an entire Outcome Period. If the Underlying ETF experiences any percentage gains over the amount of the Cap, Fund shareholders will not experience those gains. Therefore, regardless of the price return of the Underlying ETF, the Cap (net of fees) is the maximum return an investor can achieve from an investment in the Fund for that Outcome Period. The Cap is set on the first day of each Outcome Period. The Cap is provided prior to taking into account annual Fund management fees of 0.69% of the Fund's daily net assets, brokerage commissions, trading fees, taxes and any extraordinary expenses (such as unexpected litigation) incurred by the Fund. The pre-determined Cap applicable to an Outcome Period will vary based on prevailing market conditions at the time that the Cap is set, including interest rate levels, Underlying ETF volatility, and the relationship of puts and calls on the FLEX Options.

The Cap level is a result of the design of the Fund's principal investment strategy. To provide the Capital Protected Target Outcome, the Fund purchases and sells a series of put and call FLEX Options on or around the last business day of the month prior to the beginning of an Outcome Period. As the purchaser of these FLEX Options, the Fund is obligated to pay a premium to the seller of those FLEX Options. The Adviser will calculate the amount of premiums that the Fund will owe on the put options acquired to provide the Capital Protection and will then sell call FLEX Options with terms that entitle the Fund to receive premiums such that the net amount of premiums paid per unit of the Underlying ETF is approximately equal to the price per unit of shares of the Underlying ETF. The Cap is the strike price of those FLEX Options the Fund is selling. The Cap, and the Fund's value relative to it on any given day, should be considered before investing in the Fund. If an investor purchases Fund Shares during an Outcome Period, and the Fund has already increased in value above its Initial Fund Value for that Outcome Period to a level near the Cap, an investor purchasing Fund Shares will have limited to no gain potential for the remainder of the Outcome Period (because the investor's potential gain will be limited to the difference between the Fund's NAV on the date the investor purchased the Fund Shares and the Cap). However, the investor will remain vulnerable to significant downside risk because the investor will bear the losses between the price at which it purchased its Fund Shares and the Initial Fund Value for the Outcome Period before subsequent losses will be protected by the Capital Protection. If an investor buys Fund Shares when the price exceeds the Cap, an investor selling their shares at the end of the Outcome Period will not experience any gain regardless of the price return of the Underlying ETF. There is no guarantee that the Fund will be successful in providing these investment outcomes for any Outcome Period, and an investor may experience returns on the Fund significantly below the Cap.

In periods of extreme market volatility or during market disruption events, the Fund's ability to offset investor losses through the use of the FLEX Options to achieve the stated Capital Protection, or provide a return up to the stated upside Cap may be impaired, resulting in an upside limit significantly below the Cap and downside protection significantly lower than full capital protection (i.e., losses greater than 0%), because the Fund may not be able to trade or exercise existing FLEX Options, or may not receive timely payment from its counterparties. An investor may lose their entire investment and an investment in the Fund is only appropriate for investors willing to bear those losses.

For each Outcome Period, the Fund will invest in both purchased and written put and call FLEX Options that reference the Underlying ETF. Because the value of the Fund is based on FLEX Options that reference the Underlying ETF and not the Underlying ETF directly, variations in the value of the FLEX Options impact the correlation between the Fund's NAV and the price of the Underlying ETF.

Additional Information About Investment Strategies and Related Risks

General Information about FLEX Options

FLEX Options are customizable exchange-traded option contracts guaranteed for settlement by the Options Clearing Corporation ("OCC"). The OCC guarantees performance by each of the counterparties to the FLEX Options, becoming the "buyer for every seller and the seller for every buyer," with the goal of protecting clearing members and options traders from counterparty risk. The OCC may make adjustments to FLEX Options for certain significant events, as more fully described in the Fund's Statement of Additional Information. Although guaranteed for settlement by the OCC, FLEX Options are still subject to counterparty risk with the OCC and subject to the risk that the OCC may fail to perform the settlement of the FLEX Options due to bankruptcy or other adverse reasons. The FLEX Options that the Fund will hold that reference the Underlying ETF will give the Fund the right or the obligation to either receive or deliver shares of the Underlying ETF, or the right or the obligation to either receive or deliver a cash payment on the option expiration date based upon the difference between the Underlying ETF's value and a strike price, depending on whether the option is a put or call option and whether the Fund purchases or sells the option. The FLEX Options held by the Fund are European style options, which are exercisable at the strike price only on the FLEX Option expiration date. The Fund will generally, under normal conditions, hold FLEX Options for each Outcome Period. The Fund will purchase call options (giving the Fund the right to receive shares of the Underlying ETF or a cash payment) and put options (giving the Fund the right to deliver shares of the Underlying ETF or a cash payment), while simultaneously selling (i.e., writing) call options (giving the Fund the obligation to deliver shares of the Underlying ETF or a cash payment). The Fund intends to structure the FLEX Options so that any amount owed by the Fund on the written FLEX Options will be covered by payouts at expiration from the purchased FLEX Options. As a result, the Fund expects the FLEX Options to be fully covered and no additional collateral will be necessary during the life of the Fund. The Fund receives premiums in exchange for the written FLEX Options and pays premiums in exchange for the purchased FLEX Options. The OCC and securities exchanges on which the FLEX Options are listed do not charge ongoing fees to writers or purchasers of the FLEX Options during their life for continuing to hold the option contracts but may charge transaction fees. Each of the FLEX Options purchased and sold throughout the Outcome Period will have the same terms, such as strike price and expiration date, as the FLEX Options purchased and sold on the first day of the Outcome Period. On the Flex Options expiration date, the Fund intends to sell the Flex Options prior to their expiration or cash-settle the Flex Options and use the resulting proceeds to purchase new Flex Options for the next Outcome Period.

The Underlying ETF

The Underlying ETF is an exchange-traded unit investment trust that uses a replication strategy, meaning it invests in as many of the stocks in the S&P 500^®​ Index as is practicable. PDR Services, LLC ("PDR") serves as the Underlying ETF's sponsor. The investment objective of the Underlying ETF is to seek to provide investment results that, before fees and expenses, correspond generally to the price and yield performance of the S&P 500^®​ Index (the "Index"). See below for a description of the Underlying ETF's principal investment strategies and risks. You can find the Underlying ETF's prospectus and other information about the ETF, including the statement of additional information and most recent reports to shareholders, online at https://us.spdrs.com/en/etf/spdr-sp-500-etf-SPY.

The summary information below regarding the Underlying ETF comes from its filings with the SEC. You are urged to refer to the SEC filings made by the Underlying ETF and to other publicly available information (e.g., the ETF's annual reports) to obtain an understanding of the ETF's business and financial prospects. The following description of the Underlying ETF's principal investment strategies was taken directly from the Underlying ETF's prospectus, dated January 26, 2024 ("SPY" refers to the Underlying ETF; other defined terms have been modified).

"SPY seeks to achieve its investment objective by holding a portfolio of the common stocks that are included in the Index (the "Portfolio"), with the weight of each stock in SPY's Portfolio substantially corresponding to the weight of such stock in the Index. In SPY's prospectus, the term "Portfolio Securities" refers to the common stocks that are actually held by SPY and make up SPY's Portfolio, while the term "Index Securities" refers to the common stocks that are included in the Index, as determined by the index provider, S&P Dow Jones Indices LLC ("S&P"). At any time, SPY's Portfolio will consist of as many of the Index Securities as is practicable. To maintain the correspondence between the composition and weightings of Portfolio Securities and Index Securities, State Street Global Advisors Trust Company (the "Trustee") or its parent company, State Street Bank and Trust Company ("SSBT") adjusts SPY's Portfolio from time to time to conform to periodic changes made by S&P to the identity and/or relative weightings of Index Securities in the Index. SPY's Trustee or SSBT aggregates certain of these adjustments and

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makes changes to SPY's Portfolio at least monthly, or more frequently in the case of significant changes to the Index. SPY may pay transaction costs, such as brokerage commissions, when it buys and sells securities (or "turns over" its Portfolio). Such transaction costs may be higher if there are significant rebalancings of Index Securities in the Index, which may also result in higher taxes when SPY's units are held in a taxable account. These costs, which are not reflected in SPY's estimated annual Trust ordinary operating expenses, affect SPY's performance. During the most recent fiscal year, SPY's portfolio turnover rate was 2% of the average value of its portfolio. SPY's portfolio turnover rate does not include securities received or delivered from processing creations or redemptions of SPY's units. Portfolio turnover will be a function of changes to the Index as well as requirements of SPY's trust agreement. ... Although SPY may fail to own certain Index Securities at any particular time, SPY generally will be substantially invested in Index Securities, which should result in a close correspondence between the performance of the Index and the performance of SPY. ... SPY does not hold or trade futures or swaps and is not a commodity pool. ... The Index includes five hundred (500) selected companies, all of which are listed on national stock exchanges and spans a broad range of major industries. ... Since 1968, the Index has been a component of the U.S. Commerce Department's list of Leading Indicators that track key sectors of the U.S. economy. Current information regarding the market value of the Index is available from market information services. The Index is determined, comprised and calculated without regard to SPY."

As of December 1, 2023, the Underlying ETF had significant investments in information technology companies.

Subsequent Outcome Periods

The Fund will alert existing shareholders to the new Cap at the beginning of each new Outcome Period in the following manner:

1. Approximately one week prior to the end of the current Outcome Period, the Fund will make a sticker filing that will alert existing shareholders that the Outcome Period is approaching its conclusion and disclose the anticipated Cap range for the next Outcome Period. This filing will be mailed to existing shareholders.

2. Following the close of business on the last day of the Outcome Period, the Fund will make a sticker filing that discloses the Fund's Cap for the next Outcome Period. This filing will be mailed to existing shareholders.

3. On the first day of the new Outcome Period, the Fund will file a full prospectus that incorporates the sticker filing from the previous evening which replaces the Caps/dates associated with the previous Outcome Period with the Caps/dates associated with the new Outcome Period. Correspondingly, the Fund will file a revised summary prospectus that reflects such changes.

The information referenced above will also be available on the Fund's website at www.calamos.com.

Changes in 80% policy

The Fund has adopted a non-fundamental operating policy that requires it, under normal circumstances, to invest at least 80% of its net assets (plus borrowings for investment purposes, if any) in investments that provide exposure to the S&P 500^®​ Index. Although this requirement may be changed by the Board of Trustees without shareholder approval, the Fund will notify shareholders in writing at least 60 days prior to any change in its 80% policy.

Non-Principal Investments

Cash Equivalents and Short-Term Investments

The Fund may invest in securities with maturities of less than one year or cash equivalents, or it may hold cash. The percentage of the Fund invested in such holdings varies and depends on several factors, including market conditions. For temporary defensive purposes and during periods of high cash inflows or outflows, the Fund may invest part or all of its assets in these securities or it may hold cash. During such periods, the Fund may not be able to achieve its investment objective. The Fund may adopt a defensive strategy when the portfolio managers believe securities in which such Fund normally invests have elevated risks due to political or economic factors and in other extraordinary circumstances. For more information on eligible short-term investments, see the SAI.

Illiquid Investments

The Fund may invest up to 15% of its net assets in securities and other instruments that are, at the time of investment, illiquid (determined using the Securities and Exchange Commission's standard applicable to investment companies, i.e., any investment

Additional Information About Investment Strategies and Related Risks

that the Fund reasonably expects cannot be sold or disposed of in current market conditions in seven calendar days or less without the sale or disposition significantly changing the market value of the investment). For this purpose, illiquid investments may include, but are not limited to, certain restricted securities (securities the disposition of which is restricted under the federal securities laws), certain securities that may only be resold pursuant to Rule 144A under the Securities Act, and certain repurchase agreements, among others.

Temporary Investments

In response to market, economic, political, or other conditions, the Fund may temporarily invest for defensive purposes that are inconsistent with the Fund's principal investment strategies. If the Fund does so, different factors could affect the Fund's performance, and the Fund may not achieve its investment objective.

Risks of Investing in the Fund

This prospectus describes the risks you may face as an investor in the Fund. It is important to keep in mind that generally, investments with a higher potential reward also have a higher risk of losing money. The reverse is also commonly true: the lower the risk, the lower the potential reward. However, as you consider an investment in the Fund, you should also take into account your tolerance for the daily fluctuations of the financial markets and whether you can afford to leave your money in this investment for a long period of time to ride out down periods.

As with any security, there are market and investment risks associated with your investment in the Fund. The value of your investment will fluctuate over time, and it is possible to lose money. Each risk summarized below is considered a "principal risk" of investing in the Fund, regardless of the order in which it appears.

Principal Risks

Authorized Participant Concentration Risk. Only an Authorized Participant may engage in creation or redemption transactions directly with the Fund, and none of those Authorized Participants is obligated to engage in creation and/or redemption transactions. The Fund has a limited number of institutions that may act as Authorized Participants on an agency basis (i.e., on behalf of other market participants). To the extent that Authorized Participants exit the business or are unable to proceed with creation or redemption orders with respect to the Fund and no other Authorized Participant is able to step forward to create or redeem, Fund Shares may be more likely to trade at a premium or discount to NAV and possibly face trading halts or delisting. Authorized Participant concentration risk may be heightened for ETFs, such as the Fund, that invest in securities issued by non-U.S. issuers or other securities or instruments that have lower trading volumes.

Cap Change Risk. A new Cap is established at the beginning of each Outcome Period and is dependent on prevailing market conditions at the time the Cap is established. Expected dividends of the Underlying ETF, market interest rates, the Underlying ETF's share price relative to the FLEX Options' strike prices, and the "implied volatility" of the Underlying ETF (the expected frequency and magnitude of changes of the Underlying ETF's share price) can impact the Cap the Fund is able to establish at the beginning of each outcome period. Extremely low interest rates (e.g., 0%) may result in a significantly lower Cap. As such, the Cap may rise or fall from one Outcome Period to the next and is unlikely to remain the same for consecutive Outcome Periods. Investors should monitor the changes in the Cap for each Outcome Period, information for which will be made available pursuant to the procedure outlined in the Fund's prospectus.

Capital Protection Risk. There can be no guarantee that the Fund will be successful in its strategy to provide protection against 100% of Underlying ETF losses if the Underlying ETF's share price decreases over the duration of the Outcome Period. The Fund's strategy seeks to deliver returns that match those of the Underlying ETF (up to the Cap), while limiting downside losses, if Fund Shares are held at the time at which the Fund enters into the FLEX Options and held until those FLEX Options expire at the end of the Outcome Period. In the event an investor purchases Fund Shares after the FLEX Options were entered into or sells Fund Shares prior to the expiration of the FLEX Options, the Capital Protection that the Fund seeks to provide may not be available. If the Outcome Period has begun and the Underlying ETF has increased in value, the Capital Protection will not protect any decreases in the value of the Underlying ETF to the extent of such appreciation, and therefore an investor may experience losses from this appreciated value until the Fund reaches its original NAV from the commencement of the Outcome Period. Similarly, if an investor purchases Fund Shares after the commencement of the Outcome period and the Underlying ETF

Additional Information About Investment Strategies and Related Risks

has increased in value, an investor purchasing Shares at that point will not benefit from the Capital Protection until the Underlying ETF's value decreases to its original value at the commencement of the Outcome Period. Accordingly, such investor will not receive the protection that the Fund seeks to provide until the Fund experiences losses that return it to its value at the commencement of the Outcome Period. If the FLEX Options (and therefore the Capital Protection) do not perform as expected, an investor may experience significant losses on its investment, including the loss of its entire investment.

Capped Upside Risk. The Fund's strategy seeks to provide returns that are subject to the Cap. In the event that the Underlying ETF experiences gains in excess of the Cap for the Outcome Period, the Fund will not participate in, and will underperform the Underlying ETF to the extent of, those gains beyond the Cap. The Fund's strategy seeks to deliver returns that match those of the Underlying ETF (up to the Cap), while protecting against the entirety of downside losses of the Underlying ETF, if Fund Shares are held at the time at which the Fund enters into the FLEX Options and held until those FLEX Options expire at the end of the Outcome Period. In the event an investor purchases Fund Shares after the FLEX Options were entered into, there may be little or no ability for that investor to experience an investment gain on their Shares (and such investor may be subjected to potential losses between that Fund Share price and the Fund's NAV at the commencement of the Outcome Period). Further, because the FLEX Options are designed to produce returns that match the price return of the Underlying ETF (subject to the Cap) on the last day of the Outcome Period, if an investor sells Fund Shares prior to the expiration date of the FLEX Options such investor may sell at a point where the Fund's performance does not match the performance of the Underlying ETF over the Outcome Period, and therefore may sell at a point where the Fund has underperformed the Underlying ETF.

Cash Holdings Risk. The Fund may invest in cash and cash equivalents for indefinite periods of time when the Fund's investment adviser determines the prevailing market environment warrants doing so. When the Fund holds cash positions, it may lose opportunities to participate in market appreciation, which may result in lower returns than if the Fund had remained fully invested in the market. Furthermore, cash and cash equivalents may generate minimal or no income and could negatively impact the Fund's performance and ability to achieve its investment objective.

Clearing Member Default Risk. Transactions in some types of derivatives, including FLEX Options, are required to be centrally cleared ("cleared derivatives"). In a transaction involving cleared derivatives, the Fund's counterparty is a clearing house, such as the OCC, rather than a bank or broker. Since the Fund is not a member of clearing houses and only members of a clearing house ("clearing members") can participate directly in the clearing house, the Fund will hold cleared derivatives through accounts at clearing members. In cleared derivatives positions, the Fund will make payments (including margin payments) to, and receive payments from, a clearing house through their accounts at clearing members. Customer funds held at a clearing organization in connection with any option contracts are held in a commingled omnibus account and are not identified to the name of the clearing member's individual customers. As a result, assets deposited by the Fund with any clearing member as margin for its FLEX Options may, in certain circumstances, be used to satisfy losses of other clients of the Fund's clearing member. In addition, although clearing members guarantee performance of their clients' obligations to the clearing house, there is a risk that the assets of the Fund might not be fully protected in the event of the clearing member's bankruptcy. The Fund is also subject to the risk that a limited number of clearing members are willing to transact on the Fund's behalf, which heightens the risks associated with a clearing member's default. If a clearing member defaults the Fund could lose some or all of the benefits of a transaction entered into by the Fund with the clearing member. The loss of a clearing member for the Fund to transact with could result in increased transaction costs and other operational issues that could impede the Fund's ability to implement its investment strategy. If the Fund cannot find a clearing member to transact with on the Fund's behalf, the Fund may be unable to effectively implement its investment strategy.

Correlation Risk. The FLEX Options held by the Fund will be exercisable at the strike price only on their expiration date. Prior to the expiration date, the value of the FLEX Options will be determined based upon market quotations or using other recognized pricing methods, consistent with the Fund's valuation policy. Because a component of the FLEX option's value will be affected by, among other things, changes in the Underlying ETF's share price, changes in interest rates, changes in the actual and implied volatility of the Underlying ETF's share price and the remaining time until the FLEX Options expire, the value of the Fund's FLEX Options positions is not anticipated to increase or decrease at the same rate as the Underlying ETF's share price, and it is possible they may move in different directions, and as a result, the Fund's NAV may not increase or decrease at the same rate as the Underlying ETF's share price. The Fund's strategy is designed to produce the outcomes upon the expiration of

Additional Information About Investment Strategies and Related Risks

the FLEX Options on the last business day of the Outcome Period, and it should not be expected that the outcomes will be provided at any point other than the end of the Outcome Period.

Costs of Buying and Selling Fund Shares. Due to the costs of buying or selling Fund Shares, including brokerage commissions imposed by brokers and bid/ask spreads, frequent trading of Fund Shares may significantly reduce investment results and an investment in Fund Shares may not be advisable for investors who anticipate regularly making small investments.

Derivatives Risk. Derivatives are instruments, such as futures and forward foreign currency contracts, whose value is derived from that of other assets, rates or indices. Derivatives may be more volatile than other investments and may magnify the Fund's gains or losses. Successful use of derivatives depends upon the level to which prices of the underlying assets correlate with price movements in the derivatives the Fund buys or sells. The Fund could be negatively affected if the change in market value of its securities fails to correlate with the value of derivatives it purchased or sold. The potential lack of a liquid market for a derivative may prevent the Fund from closing its derivatives positions to limit losses or realize profits. Derivatives may be purchased for a fraction of their value and small price movements may result in an immediate and substantial loss to the Fund. The use of derivatives for non-hedging purposes may be considered more speculative than other types of investments. Derivatives can be used for hedging (attempting to reduce risk by offsetting one investment position with another) or non-hedging purposes. Hedging with derivatives may increase expenses, and there is no guarantee that a hedging strategy will work. While hedging can reduce or eliminate losses, it can also reduce or eliminate gains. In addition, derivative instruments are subject to counterparty risk, meaning that the party with whom the Fund enters into the derivatives transaction (e.g., the clearinghouse or the broker holding the Fund's position for a futures contract or the counterparty for a forward contract) may experience a significant credit event and/or may be unwilling or unable to make timely settlement payments or otherwise honor its obligations. Changes in the value of a derivative may not correlate perfectly with the underlying asset, rate or index, and the Fund could lose more than the principal amount invested.

Equity Securities Risk. Equity investments are subject to greater fluctuations in market value than other asset classes as a result of such factors as a company's business performance, investor perceptions, stock market trends and general economic conditions.

FLEX Options Risk. Trading FLEX Options involves risks different from, or possibly greater than, the risks associated with investing directly in securities. The Fund may not experience substantial upside participation from specific FLEX Option positions and certain FLEX Option positions may expire worthless. The FLEX Options are listed on an exchange; however, no one can guarantee that a liquid secondary trading market will exist for the FLEX Options. In the event that trading in the FLEX Options is limited or absent, the value of the Fund's FLEX Options may decrease. In a less liquid market for the FLEX Options, liquidating the FLEX Options may require the payment of a premium (for written FLEX Options) or acceptance of a discounted price (for purchased FLEX Options) and may take longer to complete. A less liquid trading market may adversely impact the value of the FLEX Options and Fund Shares and result in the Fund being unable to achieve its investment objective. Less liquidity in the trading of the Fund's FLEX Options could have an impact on the prices paid or received by the Fund for the FLEX Options in connection with creations and redemptions of the Fund's Shares. Depending on the nature of this impact to pricing, the Fund may be forced to pay more for redemptions (or receive less for creations) than the price at which it currently values the FLEX Options. Such overpayment or under collection may impact the value of the Fund and whether the Fund can satisfy its investment objective. Additionally, in a less liquid market for the FLEX Options, the liquidation of a large number of options may more significantly impact the price. A less liquid trading market may adversely impact the value of the FLEX Options and the value of your investment. The trading in FLEX Options may be less deep and liquid than the market for certain other exchange-traded options, non-customized options or other securities.

The FLEX Options held by the Fund will be exercisable at the strike price only on their expiration date. Prior to the expiration date, the value of the FLEX Options will be determined based upon market quotations or using other recognized pricing methods. The FLEX Options are also subject to correlation risk, meaning the value of the FLEX Options does not increase or decrease at the same rate as the Underlying ETF (although they generally move in the same direction) or its underlying securities. The value of the FLEX Options prior to the expiration date may vary because of factors other than the value of the Underlying ETF, such as interest rate changes, changing supply and demand, decreased liquidity of the FLEX Options, a change in the actual and perceived volatility of the stock market and the Underlying ETF and the remaining time to expiration. FLEX Option prices may also be highly volatile and may fluctuate substantially during a short period of time. During periods of reduced market liquidity or in the absence of readily available market quotations for the holdings of the Fund, the ability of the Fund to value the FLEX Options becomes more difficult

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and the judgment of the Fund's investment adviser (employing the fair value procedures approved by the Board of Trustees of the Trust) may play a greater role in the valuation of the Fund's holdings due to reduced availability of reliable objective pricing data. Consequently, while such determinations may be made in good faith, it may nevertheless be more difficult for the Fund to accurately assign a daily value. Under those circumstances, the value of the FLEX Options will require more reliance on the investment adviser's judgment than that required for securities for which there is an active trading market. This creates a risk of mispricing or improper valuation of the FLEX Options which could impact the value paid for shares of the Fund.

Investment Timing Risk. An investor who purchases Fund Shares other than on the first day of the options package and/or sells Fund Shares before the options package expires may not experience the 100% downside protection or upside participation in the Underlying ETF. The Fund's downside protection and upside participation of the Underlying ETF may only be available for investors who hold Fund Shares throughout the complete term of the options package. An investor can expect their Fund Shares to move generally in the same direction as the Underlying ETF during the one-year options package. However, Fund Shares may not experience the same price movement as the price movement of the Underlying ETF. During the duration of the option package, there may be periods of significant disparity between the Fund's NAV and the Underlying ETF's price performance. For example, if an investor purchases Fund Shares during an options package period at a time when the Underlying ETF's share price has increased from its price at the beginning of the options package period, the investor may not be 100% protected against Underlying ETF downside losses. In addition, if an investor purchases Fund Shares during an options package period at a time when the Underlying ETF's share price has increased from its price at the beginning of the options package period, that investor's cap will essentially be decreased from the stated Cap by the amount of the increase in the Underlying ETF's value.

Large-Capitalization Investing Risk. Large-capitalization stocks as a group could fall out of favor with the market, which may cause the Fund to underperform funds that focus on other types of stocks. In addition, larger, more established companies may be unable to respond quickly to new competitive challenges such as changes in technology and consumer preferences. Many larger companies also may not be able to attain the high growth rate of successful smaller companies, especially during extended periods of economic expansion.

Liquidity Risk. Liquidity risk exists when particular investments are difficult to purchase or sell. The Fund's investments in illiquid securities may reduce the returns of the Fund because it may be unable to sell the illiquid securities at an advantageous time or price.

Liquidity Risk - FLEX Options. In the event that trading in the underlying FLEX Options is limited or absent, the value of the Fund's FLEX Options may decrease. There is no guarantee that a liquid secondary trading market will exist for the FLEX Options. The trading in FLEX Options may be less deep and liquid than the market for certain other securities, including certain non-customized option contracts. In a less liquid market for the FLEX Options, terminating the FLEX Options may require the payment of a premium or acceptance of a discounted price and may take longer to complete. Additionally, the liquidation of a large number of FLEX Options may more significantly impact the price in a less liquid market. Further, the Fund requires a sufficient number of participants to facilitate the purchase and sale of options on an exchange to provide liquidity to the Fund for its FLEX Option positions. A less liquid trading market may adversely impact the value of the FLEX Options and the value of your investment.

Market Maker Risk. If the Fund has lower average daily trading volumes, it may rely on a small number of third-party market makers to provide a market for the purchase and sale of Fund Shares. Any trading halt or other problem relating to the trading activity of these market makers could result in a dramatic change in the spread between the Fund's net asset value and the price at which the Fund Shares are trading on the Exchange, which could result in a decrease in value of the Fund Shares. In addition, decisions by market makers or authorized participants to reduce their role or step away from these activities in times of market stress could inhibit the effectiveness of the arbitrage process in maintaining the relationship between the underlying values of the Fund's portfolio securities and the Fund's market price. This reduced effectiveness could result in Fund Shares trading at a discount to net asset value and also in greater than normal intra-day bid-ask spreads for Fund Shares.

Market Risk. The risk that the securities markets will increase or decrease in value is considered market risk and applies to any security. If there is a general decline in the stock or fixed-income market, it is possible your investment may lose value regardless of the individual results of the companies in which the Fund invests.

Additional Information About Investment Strategies and Related Risks

New Fund Risk. The Fund is a recently organized investment company with a limited operating history. As a result, prospective investors have a limited track record or history on which to base their investment decision.

Non-Diversification Risk. The Fund is classified as "non-diversified" under the 1940 Act. As a result, the Fund is only limited as to the percentage of its assets which may be invested in the securities of any one issuer by the diversification requirements imposed by the Internal Revenue Code of 1986, as amended. The Fund may invest a relatively high percentage of its assets in a limited number of issuers. As a result, the Fund may be more susceptible to a single adverse economic or regulatory occurrence affecting one or more of these issuers, experience increased volatility and be highly invested in certain issuers.

Options Risk. There are significant differences between the securities and options markets that could result in an imperfect correlation among these markets, causing a given transaction not to achieve its objectives. The Fund's ability to utilize options successfully will depend on Calamos Advisors' ability to predict pertinent market movements, which cannot be assured.

The Fund's ability to close out its position as a purchaser or seller of an Options Clearing Corporation or exchange-listed put or call option is dependent, in part, upon the liquidity of the options market. If the Fund were unable to close out an option that it had purchased on a security, it would have to exercise the option to realize any profit or the option would expire and become worthless. If the Fund were unable to close out a covered call option that it had written on a security, it would not be able to sell the underlying security until the option expired. As the writer of a covered call option on a security, the Fund foregoes, during the option's life, the opportunity to profit from increases in the market value of the security covering the call option above the sum of the premium and the exercise price of the call. The hours of trading for listed options may not coincide with the hours during which the underlying financial instruments are traded. To the extent that the option markets close before the markets for the underlying financial instruments, significant price and rate movements can take place in the underlying markets that cannot be reflected in the option markets until the next trading day.

Unless the parties provide for it, there is no central clearing or guaranty function in an over-the-counter option. As a result, if the counterparty fails to make or take delivery of the security or other instrument underlying an over-the-counter option it has entered into with the Fund or fails to make a cash settlement payment due in accordance with the terms of that option, the Fund will lose any premium it paid for the option as well as any anticipated benefit of the transaction. Accordingly, the Adviser must assess the creditworthiness of each such counterparty or any guarantor or credit enhancement of the counterparty's credit to determine the likelihood that the terms of the over-the-counter option will be satisfied.

The Fund may also purchase or write over-the-counter put or call options, which involves risks different from, and possibly greater than, the risks associated with exchange-listed put or call options. In some instances, over-the-counter put or call options may expose the Fund to the risk that a counterparty may be unable or unwilling to perform according to a contract, and that any deterioration in a counterparty's creditworthiness could adversely affect the instrument. In addition, the Fund may be exposed to a risk that losses may exceed the amount originally invested.

Premium-Discount Risk. The Fund's Shares may trade above or below their NAV. The market prices of Fund Shares will generally fluctuate in accordance with changes in NAV as well as the relative supply of, and demand for, Fund Shares on the Exchange. The trading price of Fund Shares may deviate significantly from NAV during periods of market volatility.

Secondary Market Trading Risk. Investors buying or selling Fund Shares in the secondary market will pay brokerage commissions or other charges imposed by brokers as determined by that broker. Brokerage commissions are often a fixed amount and may be a significant proportional cost for investors seeking to buy or sell relatively small amounts of Fund Shares. Although the Fund's Shares are listed on the Exchange, there can be no assurance that an active or liquid trading market for them will develop or be maintained. In addition, trading in Fund Shares on the Exchange may be halted.

Sector Risk. To the extent the Underlying ETF invests a significant portion of its assets in a particular sector, a greater portion of the Fund's performance may be affected by the general business and economic conditions affecting that sector. Each sector may share economic risk with the broader market, however there may be economic risks specific to each sector. As a result, returns from those sectors may trail returns from the overall stock market and it is possible that the Underlying ETF may underperform the broader market.

Additional Information About Investment Strategies and Related Risks

Tax Risk. The Fund intends to elect and to qualify each year to be treated as a regulated investment company ("RIC") under Subchapter M of the Internal Revenue Code of 1986, as amended (the "Code"). The federal income tax treatment of the securities in which the Fund may invest, including the Fund's option strategy, may not be clear or may be subject to recharacterization by the Internal Revenue Service. It could be more difficult to comply with the tax requirements applicable to RICs if the tax characterization of investments or the tax treatment of the income from such investments were successfully challenged by the Internal Revenue Service. Any such failure to comply with the rules applicable to RICs could cause the Fund to fail to qualify as such. To qualify and maintain its status as a RIC, the Fund must meet certain income, diversification and distributions tests. For purposes of the diversification test, the identification of the issuer (or, in some cases, issuers) of a particular Fund investment can depend on the terms and conditions of that investment. In particular, there is no published Internal Revenue Service guidance or case law on how to determine the "issuer" of certain derivatives that the Fund will enter into. Based upon the language in the legislative history, the Fund intends to treat the issuer of an equity option as the referenced asset and to treat any income it may derive from an equity option as "qualifying income" under the provisions of the Code applicable to RICs. In the case of FLEX Options, assuming the referenced asset qualifies as a RIC, treating the issuer as the referenced asset would allow the Fund to count the FLEX Options as automatically diversified investments under the RIC diversification requirements. If the income is not qualifying income or the issuer of equity options, including FLEX Options, is not appropriately the referenced asset, the Fund may not qualify, or may be disqualified, as a RIC. If the Fund does not qualify as a RIC for any taxable year and certain relief provisions are not available, the Fund's taxable income will be subject to tax at the Fund level and to a further tax at the shareholder level when such income is distributed.

The Fund's investments in offsetting positions with respect to the Underlying ETF may affect the character of gains or losses realized by the Fund under the Code's "straddle" rules and may increase the amount of short-term capital gain realized by the Fund. Certain options the Fund holds may not qualify as "Section 1256 contracts" under Section 1256 of the Code, and disposition of such options will likely result in short-term or long-term capital gains or losses depending on the holding period.

There is a risk that if the offsetting FLEX Options are held by a single person that the IRS may take the position that the FLEX Options, viewed together, should be treated as a single debt instrument for federal tax purposes. The result of such a position would be that the Fund would fail the RIC diversification tests causing the RIC to be taxed as a C corporation, unless certain cure rights based upon reasonable cause may apply. The Fund has obtained an opinion of tax counsel that the FLEX Options should not be collapsed into a single instrument. However, such an opinion is not binding upon the IRS or the courts.

Trading Issues Risk. Trading in Fund Shares on the Exchange may be halted due to market conditions or for reasons that, in the view of the Exchange, make trading in shares inadvisable. In addition, trading in Fund Shares on the Exchange is subject to trading halts caused by extraordinary market volatility pursuant to the Exchange's "circuit breaker" rules. There can be no assurance that the requirements of the Exchange necessary to maintain the listing of the Fund will continue to be met or will remain unchanged. The Fund may have difficulty maintaining its listing on the Exchange in the event the Fund's assets are small, the Fund does not have enough shareholders, or if the Fund is unable to proceed with creation and/or redemption orders.

Underlying ETF Risk. The Fund invests in FLEX Options that reference an ETF, which subjects the Fund to certain of the risks of owning shares of an ETF as well as the types of instruments in which the Underlying ETF invests. The value of an ETF will fluctuate over time based on fluctuations in the values of the securities held by the ETF, which may be affected by changes in general economic conditions, expectations for future growth and profits, interest rates and the supply and demand for those securities. In addition, ETFs are subject to absence of an active market risk, premium/discount risk, tracking error risk and trading issues risk. Brokerage, tax and other expenses may negatively impact the performance of the Underlying ETF and, in turn, the value of the Fund's shares. An ETF that tracks an index may not exactly match the performance of the index due to cash drag, differences between the portfolio of the ETF and the components of the index, expenses and other factors.

Valuation Risk. During periods of reduced market liquidity or in the absence of readily available market quotations for the holdings of the Fund, the ability of the Fund to value the FLEX Options and/or LEAPS Options may become more difficult. In market environments where there is reduced availability of reliable objective pricing data, the judgment of Calamos Advisors in determining the fair value of the security may play a greater role. While such determinations may be made in good faith, it may nevertheless be more difficult for the Fund to accurately assign a daily value.

Additional Information About Investment Strategies and Related Risks

The following are non-principal risks that generally apply to the Fund:

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

Investment Management Risk. Whether the Fund achieves its investment objective(s) is significantly impacted by whether the Adviser is able to choose suitable investments for the Fund.

Market Disruption Risk. Certain events have a disruptive effect on securities markets, including but not limited to, terrorist attacks, war and other geopolitical events or catastrophes. The Adviser cannot predict the effect of similar events in the future on the U.S. or foreign economies. Certain securities such as high yield and equity securities tend to be impacted more by these events than other types of securities in terms of price and volatility.

Operational Risk. The Fund is subject to risks arising from various operational factors, including, but not limited to, human error, processing and communication errors, errors of the Fund's service providers, counterparties or other third-parties, failed or inadequate processes and technology or systems failures. The Fund relies on third-parties for a range of services, including custody. Any delay or failure relating to engaging or maintaining such service providers may affect the Fund's ability to meet its investment objective. Although the Fund and the Adviser seek to reduce these operational risks through controls and procedures, there is no way to completely protect against such risks.

Recent Market Events. Since the 2008 financial crisis, financial markets throughout the world have experienced periods of 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 (such as wars (including Russia's military invasion of the Ukraine), terror attacks, natural or environmental disasters, country instability, and public health emergencies), measures to address budget deficits, downgrading of sovereign debt, declines in oil and commodity prices, dramatic changes in currency exchange rates, and public sentiment. In addition, many governments and quasi-governmental entities throughout the world have responded to the turmoil with a variety of significant fiscal and monetary policy changes, including, but not limited to, direct capital infusions into companies, new monetary programs and dramatically lower interest rates.

The full extent of the political, economic and legal consequences of Brexit are not yet fully known, and the long-term impact of Brexit on the UK, the EU and the broader global economy may be significant. As a result of the political divisions within the UK and between the UK and the EU that the referendum vote has highlighted and the uncertain consequences of Brexit, the UK and European economies and the broader global economy could be significantly impacted, potentially resulting in increased market volatility and illiquidity, political, economic, and legal uncertainty, and lower economic growth for companies that rely significantly on Europe for their business activities and revenues. Any further exits from the EU, or the possibility of such exits, or the abandonment of the Euro, may cause additional market disruption globally and introduce new legal and regulatory uncertainties.

In addition, policy and legislative changes in the United States and in other countries are changing many aspects of financial regulation. The impact of these changes on the markets, and the practical implications for market participants, may not be fully known for some time. Widespread disease and virus epidemics and pandemics, such as the coronavirus outbreak, could likewise be highly disruptive, adversely affecting individual companies, sectors, industries, markets, currencies, interest and inflation rates, credit ratings, investor sentiment, and other factors affecting the value of the Fund's investments.

Portfolio security holdings disclosure

A description of the Fund's policies and procedures in connection with the disclosure of portfolio security holdings of the Fund are available in the SAI and on the Fund's website, www.calamos.com.

Fund Facts

Who manages the Fund?

Investment Adviser

The Fund is advised by Calamos Advisors LLC ("Calamos Advisors" or the "Advisor"), 2020 Calamos Court, Naperville, Illinois 60563. Calamos Advisors, an investment adviser registered with the SEC effective May 29, 1987, is a wholly owned subsidiary of Calamos Investments LLC ("CILLC"). CILLC's assets under management as of December 31, 2023, were $35 billion ($34 billion of which represented Calamos Advisors' assets under management). Calamos Asset Management, Inc. ("CAM") is the sole manager of CILLC. As of December 31, 2023, approximately 22% of the outstanding interests of CILLC was owned by CAM and the remaining approximately 78% of CILLC was owned by Calamos Partners LLC ("CPL") and John P. Calamos, Sr. CAM was owned by John P. Calamos, Sr. and John S. Koudounis, and CPL was owned by John S. Koudounis and Calamos Family Partners, Inc. ("CFP"). CFP was beneficially owned by members of the Calamos family, including John P. Calamos, Sr.

Subject to the overall authority of the Board of Trustees, Calamos Advisors provides continuous investment supervision and management to the Fund under a management agreement and also furnishes office space, equipment and management personnel. For these services, the Fund pays Calamos Advisors a fee based on its average daily net assets, which is accrued daily and paid on a quarterly basis. The Fund will pay fees (before any reimbursement) under the management agreement in the following amounts as a percentage of its average net assets:

Out of this management fee, Calamos Advisors pays substantially all expenses of the Fund, including the cost of transfer agency, custody, fund administration, legal, audit and other service and license fees, except for distribution and service fees payable pursuant to a Rule 12b-1 plan, if any, acquired fund fees and expenses, brokerage commissions and other expenses connected with the execution of portfolio transactions, taxes, interest, and extraordinary expenses.

At a meeting held on March 28, 2024, the Board of Trustees approved the Investment Management Agreement for the Fund. A discussion regarding the basis for the Board's approval of the Investment Management Agreement on behalf of the Fund will be included in the first shareholder report that covers the period in which the Fund commences operations.

Portfolio Managers

David O'Donohue. David O'Donohue joined Calamos Advisors in August 2014 and has been a Co-Portfolio Manager since September 2015. Between March 2013 and August 2014, he was a Trader at Forty4 Asset Management LLC/Hard8 Futures LLC. Prior thereto, Mr. O'Donohue was a Portfolio Manager at Chicago Fundamental Investment Partners LLC from February 2009 to November 2012.

Jimmy Young. Jimmy Young joined Calamos Advisors in June 2003 and has been a Co-Portfolio Manager since February 2019. Between February 2018 and February 2019, he was an Assistant Portfolio Manager. Prior thereto, he was a senior strategy analyst from September 2015 to February 2018. Between July 2013 and August 2015, he was a strategy analyst.

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

Jason Hill. Jason Hill joined Calamos Advisors in March 2004 and has been a Co-Portfolio Manager since June 2014. Between August 2013 and June 2014, he was a Senior Strategy Analyst. Previously, he was a Portfolio Administrator.

Anthony Vecchiolla. Anthony Vecchiolla joined Calamos Advisors in May 2014 and since February 2023 has been Co-Portfolio Manager. Previously, he was Research Associate from May 2014 to August 2015, Research Analyst from September 2015 to February 2020, Senior Research Analyst from February 2020 to February 2021, and Assistant Portfolio Manager from February 2021 to January 2023.

Fund Facts

The Fund's SAI provides additional information about each portfolio manager, including other accounts they manage, their ownership in the Calamos Family of Funds and their compensation.

Management Approach

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

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

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

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

• Promotes collaboration between teams; and

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

The objectives of the Investment Committee are to:

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

• Establish firm-wide secular and cyclical themes for review.

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

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

• Evaluate firm-wide and portfolio investment performance.

• Evaluate firm-wide and portfolio hedging policies and execution.

• Evaluate enhancements to the overall investment process.

How to Buy and Sell Shares

Fund Shares are listed for secondary trading on the Exchange under the symbol CPSA and individual Fund Shares may only be purchased and sold in the secondary market through a broker-dealer. The Exchange and secondary markets are closed on weekends and also are generally closed on the following holidays: New Year's Day, Dr. Martin Luther King, Jr. Day, Presidents' Day, Good Friday, Memorial Day (observed), Juneteenth, Independence Day, Labor Day, Thanksgiving Day and Christmas Day. The Exchange may close early on the business day before certain holidays and on the day after Thanksgiving Day. Exchange holiday schedules are subject to change without notice. If you buy or sell Fund Shares in the secondary market, you will pay the secondary market price for Fund Shares. In addition, you may incur customary brokerage commissions and charges and may pay some or all of the spread between the bid and the offered price in the secondary market on each leg of a round trip (purchase and sale) transaction.

The trading prices of Fund Shares will fluctuate continuously throughout trading hours based on market supply and demand rather than the relevant Fund's net asset value, which is calculated at the end of each business day. Fund Shares will trade on the Exchange at prices that may be above (i.e., at a premium) or below (i.e., at a discount), to varying degrees, the daily net asset value of Fund Shares. The trading prices of Fund Shares may deviate significantly from the Fund's net asset value during periods of market volatility. Given, however, that Fund Shares can be issued and redeemed daily in Creation Units, the Adviser believes that large discounts and premiums to net asset value should not be sustained over long periods.

Fund Facts

Authorized Participants may acquire shares directly from the Fund, and Authorized Participants may tender their shares for redemption directly to the Fund, at NAV per share only in Creation Units. Purchases and redemptions directly with the Fund must follow the Fund's procedures, which are described in the SAI.

The Fund may liquidate and terminate at any time without shareholder approval.

Book Entry

Fund Shares are held in book-entry form, which means that no stock certificates are issued. The Depository Trust Company ("DTC") or its nominee is the record owner of all outstanding Shares of the Fund and is recognized as the owner of all Shares for all purposes.

Investors owning Fund Shares are beneficial owners as shown on the records of DTC or its participants. DTC serves as the securities depository for all Fund Shares. Participants in DTC include securities brokers and dealers, banks, trust companies, clearing corporations and other institutions that directly or indirectly maintain a custodial relationship with DTC. As a beneficial owner of Fund Shares, you are not entitled to receive physical delivery of stock certificates or to have Fund Shares registered in your name, and you are not considered a registered owner of Fund Shares. Therefore, to exercise any right as an owner of Fund Shares, you must rely upon the procedures of DTC and its participants. These procedures are the same as those that apply to any other securities that you hold in book entry or "street name" form.

Fund Share Trading Prices

The trading prices of Shares of the Fund on the Exchange may differ from the Fund's daily NAV. Market forces of supply and demand, economic conditions and other factors may affect the trading prices of Shares of the Fund.

The approximate value of Shares of the Fund, an amount representing on a per share basis the sum of the current market price of the cash or securities, as applicable, accepted by the Fund in exchange for Shares of the Fund and an estimated cash component, if any, is disseminated every 15 seconds throughout the trading day through the facilities of the Consolidated Tape Association. This approximate value should not be viewed as a "real-time" update of the NAV per Share of the Fund because the approximate value may not be calculated in the same manner as the NAV, which is computed once a day, generally at the end of the business day. The Fund is not involved in, or responsible for, the calculation or dissemination of the approximate value of the Fund Shares and the Fund does not make any warranty as to its accuracy.

Frequent Purchases and Redemptions of Fund Shares

Shares of the Fund may be purchased and redeemed directly from the Fund only in Creation Units by Authorized Participants. The vast majority of trading in Shares of the Fund occurs on the secondary market, and does not involve the Fund directly. In-kind purchases and redemptions of Creation Units by Authorized Participants and cash trades on the secondary market are unlikely to cause many of the harmful effects of frequent purchases and/or redemptions of Fund Shares. Cash purchases and/or redemptions of Creation Units, however, can result in disruption of portfolio management, dilution to the Fund and increased transaction costs, which could negatively impact the Fund's ability to achieve its investment objective, and may lead to the realization of capital gains. These consequences may increase as the frequency of cash purchases and redemptions of Creation Units by Authorized Participants increases. However, direct trading by Authorized Participants is critical to ensuring that Fund Shares trade at or close to NAV.

The Fund impose no restrictions on the frequency of purchases and redemptions ("market timing"). To minimize these potential consequences of frequent purchases and redemptions of Fund Shares, the Fund employs fair valuation pricing, and imposes transaction fees on purchases and redemptions of Creation Units to cover the custodial and other costs the Fund incurs in effecting trades. In addition, the Adviser monitors trades by Authorized Participants for patterns of abusive trading and the Fund reserves the right to not accept orders from Authorized Participants that the Adviser has determined may be disruptive to the management of the Fund, or otherwise are not in the best interests of the Fund. For these reasons, the Board has not adopted policies and procedures with respect to frequent purchases and redemptions of Fund Shares. The Trust's policies and procedures regarding frequent purchases and redemptions may be modified by the Board of Trustees at any time.

The Trust's policies and procedures prohibit the practice of any officer or employee of the Trust, a Trust investment adviser (including any sub-adviser), the distributor, custodian, or transfer agent, or other affiliated person of the Trust placing orders to

Fund Facts

purchase or redeem shares of a series of the Trust after the designated time as of which the Fund calculates its NAV (i.e., "late trading").

Distribution and Service Plan

The Fund has adopted a distribution and service plan ("Plan") pursuant to Rule 12b-1 under the 1940 Act. Under the Plan, the Fund is authorized to pay distribution fees to the Distributor and other firms that provide distribution and shareholder services ("Service Providers"). If a Service Provider provides such services, the Fund may pay fees at an annual rate not to exceed 0.25% of average daily net assets, pursuant to Rule 12b-1 under the 1940 Act.

No distribution or service fees are currently paid by the Fund, however, and there are no current plans to impose these fees. In the event Rule 12b-1 fees are charged, over time they would increase the cost of an investment in the Fund because they would be paid on an ongoing basis.

Fund Website and Disclosure of Portfolio Holdings

The Trust maintains a website for the Fund at www.calamos.com. Among other things, this website includes this Prospectus and the SAI, and will include the Fund's holdings, the Fund's last annual and semi-annual reports (when available), pricing information about Fund Shares trading on the Exchange, daily NAV calculations and a historical comparison of the trading prices to NAV.

Each day the Fund is open for business, the Trust publicly disseminates the Fund's full portfolio holdings as of the close of the previous day through its website at www.calamos.com. A description of the Trust's policies and procedures with respect to the disclosure of the Fund's portfolio holdings is available in the Fund's SAI.

Dividends, Other Distributions and Taxes

Fund Distributions

The Fund distributes its net realized capital gains, if any, to shareholders annually. Ordinarily, dividends from net investment income, if any, are declared and paid at least annually by the Fund.

Distributions in cash may be reinvested automatically in additional whole Fund Shares only if the broker through whom you purchased Fund Shares makes such option available. The Fund realizes capital gains or losses whenever it sells securities. Net long-term capital gains are distributed to shareholders as "capital gain dividends."

Brokers may make available to their customers who own Fund Shares the DTC book-entry dividend reinvestment service. To determine whether the dividend reinvestment service is available and whether there is a commission or other charge for using this service, consult your broker. Brokers may require Fund shareholders to adhere to specific procedures and timetables. If this service is available and used, dividend distributions of both income and net realized gains will be automatically reinvested in additional whole Fund Shares of the Fund purchased in the secondary market. Without this service, investors would receive their distributions in cash.

Taxes

As with any investment, you should consider how your investment in Fund Shares of the Fund will be taxed. The tax information in this prospectus is provided only as general information. This section is current as of the date of this prospectus. Tax laws and interpretations change frequently, and these summaries do not describe all of the tax consequences to all taxpayers. For example, these summaries generally do not describe your situation if you are a corporation, a non-U.S. person, a broker-dealer, or other investor with special circumstances. However, with respect to certain tax issues, the summaries describe the general tax treatment of certain distributions made to corporations and non-U.S. persons. In addition, this section does not describe your state, local or non-U.S. tax consequences You should consult your own tax advisor about the tax consequences of an investment in Fund Shares.

Fund distributions to you and the sale or redemption of your Fund Shares will have tax consequences to you. Such consequences may be different if you hold your Fund Shares through a tax-exempt entity or tax-advantaged retirement account, such as an individual retirement account or 401(k) plan.

Fund Facts

The Fund intends to elect to be treated, and intends to qualify each year, as a regulated investment company (a "RIC") under the Code. As a RIC, the Fund is generally not subject to corporate-level U.S. federal income tax on any net ordinary income or capital gains that are timely distributed to shareholders. However, the Fund's failure to qualify as a RIC or to meet minimum distribution requirements would result (if certain relief provisions were not available) in corporate-level taxation and, consequently, a reduction in amounts available for distribution to shareholders.

The Fund may enter into option agreements with the same counterparty but has taken the position that the option agreements are separate agreements. Under general tax principles, the Fund would not accrue income on separate option agreements during the term of the agreements. However, if the agreements are treated as one agreement, the Fund might be required to accrue income and make annual distributions of income. If the Fund is required to accrue income, but does not distribute the income to shareholders, the Fund may fail to qualify as a RIC. In addition, if the agreements are treated as one agreement, the Fund may fail either or both of the RIC income and diversification tests.

For purposes of the diversification tests, the identification of the issuer (or, in some cases, issuers) of a particular investment can depend on the terms and conditions of such investment. In particular, there is no published Internal Revenue Service guidance or case law on how to determine the "issuer" of various derivatives that the Fund may enter into. Therefore, there is a risk that the Fund will not meet the Code's diversification requirements and will not qualify, or will be disqualified, as a RIC.

Taxes on Distributions

Distributions by the Fund generally are taxable to you as ordinary income or capital gains. Distributions are subject to federal income tax, whether received in cash or reinvested in additional Fund shares or shares of another fund, and may be subject to state or local taxes. Distributions of the Fund's "investment company taxable income" generally will be taxable as ordinary income to the extent of the Fund's current or accumulated earnings and profits. Notwithstanding the foregoing, distributions that are attributable to "qualified dividends" received by the Fund may be eligible to be taxed at long-term capital gains rates, as long as the Fund and the shareholder meet certain holding period requirements. It is not anticipated that the Fund will have qualified dividend income.

Distributions of the Fund's net capital gain that are properly reported by the Fund as "capital gain dividends" will generally be taxable to you as long-term capital gains, currently at a maximum rate of 20%, regardless of your holding period in the Fund's Shares. The Fund's option strategy is likely to reduce the amount of dividends that might otherwise qualify as capital gains dividends. Distributions in excess of the Fund's current and accumulated earnings and profits first will reduce your adjusted tax basis in your Fund Shares and, after the adjusted basis is reduced to zero, will constitute capital gain. Such capital gain will be long-term capital gain and thus, will be taxed at a maximum rate of 20%, if the distributions are attributable to Fund Shares that you have held for more than one year.

Certain non-corporate taxpayers will also be subject to a 3.8% U.S. federal Medicare contribution tax with respect to the lesser of (1) their "net investment income" or (2) the excess of their "modified adjusted gross income" over a threshold amount ($200,000 for single taxpayers and $250,000 for taxpayers who are married and filing jointly).

Corporate shareholders of the Fund are generally eligible for a dividends-received deduction with respect to ordinary income dividends (but not capital gain dividends) properly designated as eligible for such deduction by the Fund, as long as the Fund and the corporate shareholder meet certain holding period and other requirements. It is not anticipated that the Fund will make distributions eligible for the dividend-received deduction.

Under a dividend reinvestment service, you may have the option to have all cash distributions automatically reinvested in additional Fund Shares. Any distributions reinvested under such a service will nevertheless be taxable to you as described above.

You will have an adjusted basis in the additional Fund Shares purchased through such a reinvestment service equal to the amount of the reinvested distribution plus the amount of any fees charged for the transaction. The additional Fund Shares will have a holding period commencing on the day following the day on which they are credited to your account.

A distribution will reduce the Fund's NAV per Share and generally will be taxable to you as ordinary income or capital gain even if it is paid from income or gains earned by the Fund before you invested in the Fund. From an investment standpoint, such a

Fund Facts

distribution constitutes a return of capital. However, from a tax standpoint, it constitutes taxable income. In general, distributions are subject to federal income tax as of the date of payment. However, distributions paid in January will be treated as paid on December 31 of the prior year if they were declared and payable to shareholders of record on a date in October, November or December of the prior year.

The Fund's transactions in derivatives, as well as any of its hedging, short sale, securities loan or similar transactions may be subject to one or more special tax rules. These rules may affect whether gains and losses recognized by the Fund are treated as ordinary or capital, accelerate the recognition of income or gains to the Fund, defer losses to the Fund, and cause adjustments in the holding periods of the Fund's securities, thereby affecting whether capital gains and losses are treated as short-term or long-term. These rules could therefore affect the amount, timing and/or character of distributions to shareholders and thus taxes payable by shareholders.

The FLEX Options included in the Fund's portfolio are exchange-traded options. Under Section 1256 of the Code, certain types of exchange-traded options are treated as if they were sold (i.e., "marked to market") at the end of each year. The Fund does not believe that some of the positions in FLEX Options held by the Fund will be subject to Section 1256, which means that the positions will not be marked to market, but the positions will be subject to the straddle rules.

The straddle rules may affect the character of gains (or losses) realized by the Fund, and losses realized by the Fund on positions that are part of a straddle may be deferred under the straddle rules, rather than being taken into account in calculating taxable income for the taxable year in which the losses are realized. In addition, certain carrying charges (including interest expense) associated with positions in a straddle may be required to be capitalized rather than deducted currently. Certain elections that the Fund may make with respect to its straddle positions may also affect the amount, character and timing of the recognition of gains or losses from the affected positions.

The tax consequences of straddle transactions to the Fund are not entirely clear in all situations under currently available authority. The straddle rules may increase the amount of short-term capital gain realized by the Fund, which is taxed as ordinary income when distributed to U.S. shareholders in a non-liquidating distribution. Because application of the straddle rules may affect the character of gains or losses, defer losses and/or accelerate the recognition of gains or losses from the affected straddle positions, if the Fund makes a non-liquidating distribution of its short-term capital gain, the amount which must be distributed to U.S. shareholders as ordinary income may be increased substantially as compared to the Fund that did not engage in such transactions.

You may be subject to federal back-up withholding tax, if you do not provide the Fund with a taxpayer identification number (for an individual, a social security number) and make other required certifications, or the Internal Revenue Service informs the Fund that your tax identification number is incorrect. Backup withholding is not an additional tax. You may claim the amount withheld as a credit on your federal income tax return, provided you furnish the appropriate information to the Internal Revenue Service.

Taxes When Shares are Sold

Any capital gain or loss realized upon a sale of Fund Shares is generally treated as long-term capital gain or loss if you have held the Fund Shares for more than one year and as short-term capital gain or loss if you have held the Fund Shares for one year or less. The ability to deduct capital losses realized on a sale of Fund Shares may be limited.

Taxes on Purchase and Redemption of Creation Units

An Authorized Participant that exchanges equity securities for Creation Units will generally recognize a gain or a loss on the exchange. Any such gain or loss will be equal to the difference between the market value of the Creation Units at the time of the exchange, plus (or minus) the cash amount received (or paid), and such Authorized Participant's aggregate basis in the securities surrendered. A person who redeems Creation Units for equity securities will generally recognize a gain or loss equal to the difference between the aggregate market value of the securities received plus (or minus) any cash received (or paid), and such person's basis in the Creation Units redeemed. The Internal Revenue Service, however, may assert that a loss realized upon an exchange of securities for Creation Units cannot be deducted currently under the rules governing "wash sales," or on the basis that there has been no significant change in the Authorized Participant's economic position with respect to such Creation Units. Persons exchanging securities should consult their own tax advisor with respect to the applicability of the wash sale rules

Fund Facts

and the availability and timing of a deduction for any loss. In addition, when a regulated investment company redeems a shareholder in kind, the regulated investment company generally is not required to recognize taxable gains in respect of the portfolio securities it distributes to the redeeming shareholder. However, the Fund may be required to recognize taxable gain on the distribution of certain securities, and the Internal Revenue Service may assert that the Fund must recognize taxable gain in respect of certain other securities that the Fund distributes to a shareholder in exchange for Creation Units, which may increase the amount of taxable gains that the Fund would otherwise be required to distribute in order to maintain its qualification as a regulated investment company and avoid the Fund-level tax.

Any capital gain or loss realized upon a redemption of Creation Units is generally treated as long-term capital gain or loss if the Creation Units have been held for more than one year and as short-term capital gain or loss if the Creation Units have been held for one year or less. If you purchase or redeem Creation Units, you will be sent a confirmation statement showing how many Fund Shares you purchased or sold and at what price.

Authorized Participants that are dealers may be subject to special tax rules and should consult their own tax advisors regarding the tax consequences of purchasing and redeeming Creation Units in their capacity as dealers.

Treatment of Fund Expenses

Expenses incurred and deducted by the Fund will generally not be treated as income taxable to you.

Non-U.S. Investors

If you are a non-U.S. investor (i.e., an investor other than a U.S. citizen or resident or a U.S. corporation, partnership, estate or trust), you should be aware that, generally, subject to applicable tax treaties, distributions from the Fund will be characterized as dividends for U.S. federal income tax purposes (other than dividends which the Fund properly reports as capital gain dividends) and will be subject to U.S. federal income taxes, including withholding taxes, subject to certain exceptions described below. However, distributions received by a non-U.S. investor from the Fund that are properly reported by the Fund as capital gain dividends may not be subject to U.S. federal income taxes, including withholding taxes, provided that the Fund makes certain elections and certain other conditions are met. The Fund's option strategy is likely to reduce the amount of distributions otherwise eligible to be capital gains dividends.

Distributions may be subject to a U.S. withholding tax of 30% in the case of distributions to (i) certain non-U.S. financial institutions that have not entered into an agreement with the U.S. Treasury to collect and disclose certain information and are not resident in a jurisdiction that has entered into such an agreement with the U.S. Treasury and (ii) certain other non-U.S. entities that do not provide certain certifications and information about the entity's U.S. owners. The Internal Revenue Service and the Department of Treasury have issued proposed regulations providing that these withholding rules will not be applicable to the gross proceeds of share redemptions or capital gains dividends that the Fund pays.

Other Tax Matters

The foregoing is only a summary of certain federal income tax considerations of investing in the Fund under current law, which is subject to change in the future. Shareholders who are not U.S. persons within the meaning of the Code, such as non-resident aliens, foreign trusts or estates, or foreign corporations or partnerships may be subject to different U.S. federal income tax treatment.

You may also be subject to state and local taxes on distributions paid by the Fund, and sales and redemptions of Fund shares. You should consult your tax advisor for further information regarding federal, state, local and/or foreign tax consequences relevant to your specific tax situation. More information about taxes can be found in the Fund's SAI.

Net Asset Value

The NAV of shares is determined at the close of regular trading on the New York Stock Exchange (normally 4:00 p.m. Eastern Time) on each day the New York Stock Exchange ("NYSE") is open. NAV is computed by determining the aggregate market value of all assets of the Fund, less its liabilities, divided by the total number of shares outstanding (assets-liabilities)/number of shares = NAV). The NYSE is closed on weekends and New Year's Day, Martin Luther King, Jr. Day, Presidents' Day, Good Friday, Memorial Day, Juneteenth National Independence Day, Independence Day, Labor Day, Thanksgiving Day and Christmas Day. The NAV takes into account the expenses and fees of the Fund, including management, administration, and distribution fees,

Fund Facts

which are accrued daily. The determination of NAV for the Fund for a particular day is applicable to all applications for the purchase of shares, as well as all requests for the redemption of shares, received by the Fund (or an authorized broker or agent, or its authorized designee) before the close of trading on the NYSE on that day.

Generally, securities traded or dealt in upon one or more securities exchanges (whether domestic or foreign) for which market quotations are readily available and not subject to restrictions against resale shall be valued at the last quoted sales price on the primary exchange or, in the absence of a sale on the primary exchange, at the mean between the current bid and ask prices on such exchange. Securities primarily traded in the National Association of Securities Dealers' Automated Quotation System ("NASDAQ") National Market System for which market quotations are readily available shall be valued using the NASDAQ official closing price. Securities that are not traded or dealt in any securities exchange (whether domestic or foreign) and for which over-the-counter market quotations are readily available generally shall be valued at the last sale price or, in the absence of a sale, at the mean between the current bid and ask price on such over-the-counter market. Debt securities not traded on an exchange may be valued at prices supplied by a pricing agent (s) based on broker or dealer supplied valuations or matrix pricing, a method of valuing securities by reference to the value of other securities with similar characteristics, such as rating, interest rate and maturity. Futures, swaps and options contracts listed for trading on a futures or options exchange or board of trade for which market quotations are generally available are valued at the last quoted sale price, or, in the absence of a sale, at the mean of the last bid and ask price. Total return swaps on exchange-listed securities are valued at the last quoted sale price, or, in the absence of a sale, at the mean of the last bid and ask price.

Securities held by the Fund are valued in accordance with policies and procedures established by the Adviser pursuant to Rule 2a-5 under the 1940 Act and approved by and subject to the oversight of the Board of Trustees ("Valuation Procedures"). If market quotations are not readily available, securities or other assets will be valued at their fair value as determined in good faith by the Adviser in accordance with procedures approved by the Board and evaluated by the Board as to the reliability of the fair value method used. In these cases, the Fund's NAV will reflect certain portfolio securities' fair values rather than their market prices. Fair value pricing involves subjective judgments, and it is possible that the fair value determined for a security or other asset may be materially different than the value that could be realized upon the sale of that security or other asset. The fair value prices can differ from market prices. The Board of Trustees has designated Calamos Advisors as "valuation designee" for the Fund. The valuation designee is responsible for determining the value of the Fund's investments. The designee may also enlist third party consultants such as an audit firm or financial officer of a security issuer on an as-needed basis to assist in determining a security-specific fair value. The Board reviews and ratifies the execution of this process and the resultant fair value prices at least quarterly to ensure the process produces reliable results.

The Fund may use independent pricing services to assist in calculating the value of the Fund's securities or other assets.

With respect to any portion of the Fund's assets that are invested in one or more open-end management investment companies registered under the 1940 Act, the Fund's net asset value is calculated based upon the net asset values of those open-end management investment companies, and the prospectuses for these companies explain the circumstances under which those companies will use fair value pricing and the effects of using fair value pricing.

Fund Service Providers

State Street Bank and Trust Company ("State Street"), located at One Congress Street, Suite 1, Boston, Massachusetts 02114-2016, serves as the Fund's administrator, custodian, fund accounting and transfer agent.

Calamos Financial Services LLC ("CFS"), located at 2020 Calamos Court, Naperville, Illinois 60563, serves as the distributor of Creation Units for the Fund on an agency basis. The Distributor does not maintain a secondary market in Fund Shares.

Ropes & Gray LLP, located at 191 North Wacker Drive, 32^nd​ Floor, Chicago, IL 60606, serves as legal counsel to the Trust.

Premium/Discount Information

Information showing the number of days the market price of the Fund Shares was greater (at a premium) and less (at a discount) than the Fund's NAV for the most recently completed calendar year, and the most recently completed calendar quarters since that year (or the life of the Fund, if shorter), is available at www.calamos.com.

Fund Facts

Investments by Other Investment Companies

Section 12(d)(1) of the 1940 Act restricts investments by investment companies in the securities of other investment companies, including Fund Shares. The SEC adopted Rule 12d1-4 under the 1940 Act on November 19, 2020, which became effective January 19, 2021. The Fund is required to comply with the conditions of Rule 12d1-4, which allows, subject to certain conditions, the Fund to invest in other registered investment companies and other registered investment companies to invest in the Fund beyond the limits contained in Section 12(d)(1) of the 1940 Act.

Financial Highlights

The Fund is new and has no performance history as of the date of this prospectus. Financial information is therefore not available.

Other Information

Continuous Offering

The method by which Creation Units of Fund Shares are created and traded may raise certain issues under applicable securities laws. Because new Creation Units of Fund Shares are issued and sold by the Fund on an ongoing basis, a "distribution," as such term is used in the Securities Act of 1933, as amended (the "Securities Act"), may occur at any point. Broker-dealers and other persons are cautioned that some activities on their part may, depending on the circumstances, result in their being deemed participants in a distribution in a manner which could render them statutory underwriters and subject them to the prospectus delivery requirements and liability provisions of the Securities Act. For example, a broker-dealer firm or its client may be deemed a statutory underwriter if it takes Creation Units after placing an order with the Distributor, breaks them down into constituent Fund Shares and sells the Fund Shares directly to customers or if it chooses to couple the creation of a supply of new Fund Shares with an active selling effort involving solicitation of secondary market demand for Fund Shares. A determination of whether one is an underwriter for purposes of the Securities Act must take into account all the facts and circumstances pertaining to the activities of the broker-dealer or its client in the particular case, and the examples mentioned above should not be considered a complete description of all the activities that could lead to a characterization as an underwriter.

Broker-dealer firms should also note that dealers who are not "underwriters" but are effecting transactions in Fund Shares, whether or not participating in the distribution of Fund Shares, are generally required to deliver a prospectus. This is because the prospectus delivery exemption in Section 4(3) of the Securities Act is not available in respect of such transactions as a result of Section 24(d) of the 1940 Act. As a result, broker-dealer firms should note that dealers who are not "underwriters" but are participating in a distribution (as contrasted with engaging in ordinary secondary market transactions) and thus dealing with the Fund Shares that are part of an overallotment within the meaning of Section 4(3)(C) of the Securities Act, will be unable to take advantage of the prospectus delivery exemption provided by Section 4(3) of the Securities Act. For delivery of prospectuses to exchange members, the prospectus delivery mechanism of Rule 153 under the Securities Act is only available with respect to transactions on a national exchange.

Disclaimer

The "S&P 500^®​" is a product of S&P Dow Jones Indices LLC or its affiliates ("SPDJI") and has been licensed for use by Calamos Advisors LLC ("Calamos Advisors"). Standard & Poor's^®​ and S&P^®​ are registered trademarks of Standard & Poor's Financial Services LLC ("S&P") and Dow Jones^®​ is a registered trademark of Dow Jones Trademark Holdings LLC ("Dow Jones"). Calamos S&P 500 Structured Alt Protection ETF - August (the "Fund") is not sponsored, endorsed, sold or promoted by SPDJI, Dow Jones, S&P, any of their respective affiliates (collectively, "S&P Dow Jones Indices"). S&P Dow Jones Indices makes no representation or warranty, express or implied, to the owners of the Fund or any member of the public regarding the advisability of investing in securities generally or in the Fund particularly or the ability of the S&P 500^®​ to track general market performance. S&P Dow Jones Indices' only relationship to Calamos Advisors with respect to the S&P 500^®​ is the licensing of the Index and certain trademarks, service marks and/or trade names of S&P Dow Jones Indices and/or its licensors. The S&P 500^®​ is determined, composed and calculated by S&P Dow Jones Indices without regard to Calamos Advisors or the Fund. S&P Dow Jones Indices has no obligation to take the needs of Calamos or the owners of the Fund into consideration in determining, composing or calculating the S&P 500^®​. S&P Dow Jones is not responsible for and has not participated in the determination of the prices, and amount of the Fund or the timing of the issuance or sale of the Fund or in the determination or calculation of the equation by which the Fund is to be converted into cash, surrendered or redeemed, as the case may be. S&P Dow Jones Indices has no obligation or liability in connection with the administration, marketing or trading of the Fund. There is no assurance that investment products based on the S&P 500^®​ will accurately track index performance or provide positive investment returns. S&P Dow Jones Indices LLC is not an investment advisor. Inclusion of a security within an index is not a recommendation by S&P Dow Jones Indices to buy, sell, or hold such security, nor is it considered to be investment advice.

S&P DOW JONES INDICES DOES NOT GUARANTEE THE ADEQUACY, ACCURACY, TIMELINESS AND/OR THE COMPLETENESS OF THE S&P 500^®​ OR ANY DATA RELATED THERETO OR ANY COMMUNICATION, INCLUDING BUT NOT LIMITED TO, ORAL OR WRITTEN COMMUNICATION (INCLUDING ELECTRONIC COMMUNICATIONS) WITH RESPECT THERETO. S&P DOW JONES INDICES SHALL NOT BE SUBJECT TO ANY DAMAGES OR LIABILITY FOR ANY ERRORS, OMISSIONS, OR DELAYS THEREIN. S&P DOW JONES INDICES MAKES NO EXPRESS OR IMPLIED WARRANTIES, AND EXPRESSLY DISCLAIMS ALL WARRANTIES, OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE OR USE OR AS TO RESULTS TO BE OBTAINED BY CALAMOS

Other Information

ADVISORS, OWNERS OF THE FUND, OR ANY OTHER PERSON OR ENTITY FROM THE USE OF THE S&P 500^®​ OR WITH RESPECT TO ANY DATA RELATED THERETO. WITHOUT LIMITING ANY OF THE FOREGOING, IN NO EVENT WHATSOEVER SHALL S&P DOW JONES INDICES BE LIABLE FOR ANY INDIRECT, SPECIAL, INCIDENTAL, PUNITIVE, OR CONSEQUENTIAL DAMAGES INCLUDING BUT NOT LIMITED TO, LOSS OF PROFITS, TRADING LOSSES, LOST TIME OR GOODWILL, EVEN IF THEY HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES, WHETHER IN CONTRACT, TORT, STRICT LIABILITY, OR OTHERWISE. THERE ARE NO THIRD PARTY BENEFICIARIES OF ANY AGREEMENTS OR ARRANGEMENTS BETWEEN S&P DOW JONES INDICES AND CALAMOS ADVISORS, OTHER THAN THE LICENSORS OF S&P DOW JONES INDICES.

Summary of Certain Provisions of the Second Amended and Restated Trust Instrument

The summary below is a synopsis of certain provisions contained in the Trust's Second Amended and Restated Trust Instrument (the "Trust Instrument"). Shareholders should refer to the Trust Instrument for further information. Defined terms have the meanings contained in the Trust Instrument.

Derivative Actions

The Second Amended and Restated Trust Instrument (the "Trust Instrument") requires, within Section 9 of Article IV, that before bringing any derivative action on behalf of the Fund, Shareholders must have made a written demand to the Board of Trustees requesting that they cause the Trust or affected Series or Class, as applicable, to file the action itself.

In order to warrant consideration, any such written demand must include at least the following:

(1) a detailed description of the action or failure to act complained of and the facts upon which each such allegation is made;

(2) a statement to the effect that the complaining Shareholders believe that they will fairly and adequately represent the interests of similarly situated Shareholders in enforcing the right of the Trust or the affected Series or Class, as applicable and an explanation of why the complaining Shareholders believe that to be the case;

(3) a certification that the following requirements have been met, as well as information reasonably designed to allow the Trustees to verify that certification:

(a) each complaining Shareholder was a Shareholder of the Trust or the affected Series or Class, as applicable, at the time of the action or failure to act complained of, or acquired the Shares afterwards by operation of law from a Person who was a Shareholder at that time; and

(b) each complaining Shareholder was a Shareholder of the Trust or the affected Series or Class, as applicable, as of the time the demand required by Section 9 of Article IV was made; and

(4) a certification that each complaining Shareholder will be a Shareholder of the Trust or the affected Series or Class, as applicable as of the commencement of the derivative action.

The Trust Instrument further provides that at least 10% of the Shareholders of the Trust or the affected Series or Class, as applicable, must join in bringing the derivative action. This provision does not apply to claims brought under the federal securities laws.

The Trust Instrument also provides that a copy of the derivative complaint must be served on the Trust, assuming the requirements described above have already been met and the derivative action has not been barred as further described in the Trust Instrument.

Forum and Waiver of Jury Trial

Section 10 of Article X of the Trust Instrument outlines which shareholder actions must be brought in state court and which must be brought in federal court. This section states in particular that, unless the Trust consents in writing to the selection of an alternative forum, the Federal District Courts of the United States of America shall be the sole and exclusive forum for the resolution of any complaint asserting a cause of action arising under any federal securities law. This provision may increase costs for a shareholder to bring a claim or may limit a shareholder's ability to bring a claim in a judicial forum that they find more convenient or favorable. While the enforceability of the exclusive forum provisions may be challenged, this section also provides that if any provisions of Section 10 shall be held to be invalid, illegal or unenforceable, the validity, legality and enforceability of the remaining portions will still apply.

Other Information

Section 10 of Article X of the Trust Instrument also states that shareholders and all other such persons bringing any such suit, action, or proceeding in the Superior Court in the State of Delaware waive the right to a trial by jury to the fullest extent permitted by law.

For more detailed information on the Fund, several additional sources of information are available to you. The Fund's SAI, incorporated by reference into this prospectus, contains detailed information on the Fund's policies and operation. Additional information about the Fund's investments is available in the annual and semi-annual reports to shareholders. In the Fund's annual reports, you will find a discussion of the market conditions and investment strategies that significantly impacted the Fund's performance during the last fiscal year. The Fund's most recent SAI, annual or semi-annual reports and certain other information are available free of charge by calling the Fund at (866) 363-9219, on the Fund's website at www.calamos.com or through your financial advisor. Shareholders may call the toll-free number above with any inquiries.

You may obtain this and other information regarding the Fund, including the SAI and Codes of Ethics adopted by the Adviser, Distributor and the Trust, directly from the SEC. Information on the SEC's website is free of charge. Visit the SEC's on-line EDGAR database at http://www.sec.gov. You may also request information regarding the Fund by sending a request (along with a duplication fee) to the SEC by sending an electronic request to [email protected].

Calamos S&P 500^®​ Structured Alt Protection ETF^TM​ - August

2020 Calamos Court
Naperville, IL 60563-2787
866.363.9219
www.calamos.com

SEC File
#811-22887

CPSASTAPRO 080124