Summary Prospectus by Investment Company - Form 497K

September 9, 2024

Summary Prospectus

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

(NYSE Arca - CPSL)

Before you invest, you may want to review the Fund's prospectus and statement of additional information, which contain more information about the Fund and its risks. You can find the Fund's prospectus, statement of additional information, reports to shareholders and other information about the Fund online at www.calamos.com/resources. You can also get this information at no cost by calling 866.363.9219 or by sending an e-mail request to [email protected]. The current prospectus and statement of additional information, both dated September 9, 2024 (and as each may be amended or supplemented), are incorporated by reference into this summary prospectus.

Investment Objective

Calamos Laddered S&P 500^®​ Structured Alt Protection ETF^TM​ (the "Fund") seeks to provide investors with capital appreciation.

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.

2 "Acquired Fund Fees and Expenses" include certain expenses incurred in connection with the Fund's investment in various exchange-traded funds ("ETFs"). The amount shown is based on estimated amounts for the current fiscal year.

3 The "Total Annual Fund Operating Expenses" in this fee table may not correlate to the expense ratios in the Fund's financial highlights and financial statements because the financial highlights and financial statements reflect only the operating expenses of the Fund and do not include Acquired Fund Fees and Expenses, which are fees and expenses incurred indirectly by the Fund through its investments in certain underlying investment companies.

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 seeks to achieve its investment objective by providing investors with US large-cap equity market exposure while attempting to limit downside risk through a laddered portfolio of twelve Calamos S&P 500^®​ Structured Alt Protection ETFs (the "Underlying ETFs"). The term "laddered portfolio" refers to the Fund's investment in multiple Underlying ETFs that have target outcome period expiration dates which occur on a rolling, or periodic, basis. See below for a discussion of "target outcome periods" and their meaning within the strategies of the Underlying ETFs. The rolling or "laddered" nature of the investments in the Underlying ETFs creates diversification of investment time period compared to the risk of acquiring or disposing of any one Underlying ETF at any one time. This diversification of investment time period is intended to mitigate the risk of failing to benefit from the downside protection of a single Underlying ETF due to the timing of investment in such Underlying ETF and the relative price of the reference asset or having limited or no upside potential remaining because of the cap of a single Underlying ETF. The Fund's laddered approach is intended to allow the Fund to continue to benefit from increases in the value of the SPDR^®​ S&P 500^®​ ETF Trust ("SPY"), while limiting downside losses. Depending on when the Fund acquires shares of an Underlying ETF, even

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

with a laddered approach, the cap and/or downside protection of an Underlying ETF may be exhausted unless the Fund acquires shares at the beginning of a Target Outcome Period (as defined below). The Fund does not typically buy shares at the beginning of the Target Outcome Period. Unlike the Underlying ETFs, the Fund itself does not pursue a target outcome strategy. The protection is only provided by the Underlying ETFs and the Fund itself does not provide any stated downside protection against losses. The Fund will likely not receive the full benefit of the Underlying ETF downside protections and could have limited upside potential. The Fund's returns are limited by the caps of the Underlying ETFs.

In order to understand the Fund's strategy and risks, it is important to understand the strategies and risks of the Underlying ETFs. See "Additional Information on the Fund's Investment Objective and Strategies" for a discussion of the principal investment strategies of the Underlying ETFs.

Under normal market conditions, the Fund will invest substantially all of its assets in the Underlying ETFs, which seek to provide investors with returns (before fees and expenses) that match the price return of SPY, up to a predetermined upside cap, while providing downside protection (before fees and expenses) against SPY losses, over a defined one-year outcome period. The Fund intends only to acquire shares of Underlying ETFs in the secondary market and will not engage in any principal transactions with the Underlying ETFs. The Fund and each Underlying ETF are advised by Calamos Advisors LLC ("Calamos" or the "Adviser"). PDR Services, LLC ("PDR") serves as SPY's sponsor. The investment objective of SPY is to seek to provide investment results that, before expenses, correspond generally to the price and yield performance of the S&P 500^®​ Index. See "SPDR^®​ S&P 500^®​ ETF Trust" below for more information.

The Underlying ETFs invest substantially all of their assets in FLexible EXchange^®​ Options ("FLEX Options") on SPY. FLEX Options are customizable exchange-traded option contracts guaranteed for settlement by the Options Clearing Corporation. Each Underlying ETF uses FLEX Options to employ a "target outcome strategy." Target outcome strategies seek to produce pre-determined investment outcomes based upon the performance of an underlying security or index (in this case, SPY). The pre-determined outcomes sought by the Underlying ETFs, which include downside protection against (before fees and expenses) SPY losses and a cap on upside potential, are based on the price return of SPY over an approximate one-year period beginning on the first business day in the month for which each Underlying ETF is named and ending on the last business day of the preceding month in the following year (the "Target Outcome Period"). Each Underlying ETF establishes a new cap annually at the beginning of each Target Outcome Period. See "Capital Protection and Cap" below under "Additional Information About Investment Strategies and Related Risks."

Each Underlying ETF's strategy has been specifically designed to produce the outcomes (before fees and expenses) based upon SPY's returns over the duration of a Target Outcome Period. At the end of each Target Outcome Period, an Underlying ETF's FLEX Options are generally allowed to expire or be sold at or near their expiration, and the proceeds are used to purchase (or roll into) a new set of FLEX Options expiring in approximately one year. This means that approximately every 30 days, one of the Underlying ETFs will undergo a "reset" of its cap and a refresh of its downside protection. At any given time after the initial ramp up period, the Fund will generally hold one Underlying ETF with FLEX Options expiring within one month, a second Underlying ETF with FLEX Options expiring within two months, a third Underlying ETF with FLEX Options expiring within three months, etc., up to and including twelve months. The rolling or "laddered" nature of the investments in the Underlying ETFs creates diversification of investment time period and market level (meaning the price of SPY at any given time) compared to the risk of acquiring or disposing of any one Underlying ETF at any one time. Because the Fund typically will not acquire shares of the Underlying ETFs on the first day of a Target Outcome Period and may dispose of shares of the Underlying ETFs before the end of the Target Outcome Period, the Fund may experience investment returns that are very different from those that the Underlying ETFs seek to provide. If an Underlying ETF has experienced certain levels of either gains or losses since the beginning of its current Target Outcome Period, there may be little to no ability for the Fund to achieve gains or benefit from the downside protection for the remainder of the Target Outcome Period.

When an investor purchases shares of a single Underlying ETF, his or her potential outcomes are limited by the Underlying ETF's stated cap and downside protection over a defined time period (depending on when the shares were purchased). Alternatively, the Fund's laddered approach provides a diversified exposure to all of the Underlying ETFs in a single investment. By owning a laddered portfolio of Underlying ETFs, the Fund has the ability to continue to benefit from increases in the value of SPY and to provide a level of downside protection as one of the Underlying ETFs will reset its cap and refresh its downside protection every month based on the price of SPY at the time of the reset. In other words, the continual and periodic "refreshing" of the Underlying ETF caps and downside protection at current SPY prices is intended to allow the Fund to continue to benefit from increases in the value of SPY, while limiting downside losses. This approach reduces the risk inherent in the Underlying ETFs of having the upside potential for an entire Target Outcome Period capped out in cases of rapid appreciation of SPY. It also reduces the risk of failing to benefit from an individual Underlying ETF downside protection in cases where SPY has depreciated. Approximately every 30 days, one of the Underlying ETFs will undergo a reset of its cap and a refresh of its downside protection, meaning that investors will have the ability to benefit from any appreciation in SPY for future periods up to the respective caps of the Underlying ETFs and will have the benefit of the downside protection for future periods. A laddered portfolio can diversify timing risk, similar to how laddered bond portfolios seek to manage timing risks for fixed-income investors.

The Fund intends only to acquire shares of Underlying ETFs in the secondary market and will not engage in any principal transactions with the Underlying ETFs. The Fund intends to generally rebalance its portfolio to equal weight (i.e., 8.33% per Underlying ETF) semi-annually. During the Ramp-Up Period the Fund will rebalance monthly to add newly-launched Underlying ETFs. The Fund also will acquire and dispose of Underlying ETFs in connection with the creation and redemption of Creation Units between semi-annual rebalances. In between such rebalances, market movements in the prices of the Underlying ETFs may result in the Fund having temporary larger exposures to certain

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

Underlying ETFs compared to others. Under such circumstances, the Fund's returns would be more greatly influenced by the returns of the Underlying ETFs with the larger exposures. If an over-weighted Underlying ETF underperforms the other Underlying ETFs, the Fund will experience returns that are inferior to those that would have been achieved if the Underlying ETFs were equally weighted. See Significant Exposure Risk below.

The current list of Underlying ETFs in the Fund's portfolio can be found at https://www.calamos.com/capabilities/structured-protection-etfs/. The Fund's website will provide, on a daily basis, the proportion of the Fund's assets invested in each Underlying ETF at any given time. Each Underlying ETF's website provides important information (including Target Outcome Period start and end dates and the cap (both gross and net of fees) and downside protection both at the start of the Underlying ETF's Target Outcome Period and on any particular day relative to the end of the Target Outcome Period).

Although this website information may be useful in understanding the investment strategies of the Underlying ETFs, it is limited in providing an investor of the Fund with all of the risks and potential outcomes associated with an investment in the Underlying ETFs. For example, it does not provide a direct example of your potential investment return in the Fund because of the Fund's laddered exposure to the Underlying ETFs in which each one of the Underlying ETFs will reset its cap and refresh its downside protection annually based on prevailing market conditions.

The Fund is classified as "non-diversified" under the Investment Company Act of 1940, as amended (the "1940 Act"). The Fund's investment strategy may include active and frequent trading. The Fund may not invest 25% or more of the value of its total assets in securities of issuers in any one industry or group of industries except to the extent that the underlying referenced index of the Underlying ETFs invests more than 25% of its assets in an industry or group of industries. This restriction does not apply to obligations issued or guaranteed by the U.S. government, its agencies or instrumentalities, or securities of other investment companies. As of August 15, 2024, SPY had significant investments in information technology companies.

Ramp-Up Period

At the current time, four of the Underlying ETFs are available for investing. For the following months - the Fund will rebalance until June 2025 when the Fund is expected to have equal weights of 8.33% of each Underlying Fund. During the Ramp-Up Period the Fund will be over weighted in certain Underlying Funds which could cause the Fund to experience returns that are inferior to those that would have been achieved if the Underlying ETFs were equally weighted. During this time, the Fund's ability to take advantage of the "laddered" nature of the investments in the Underlying ETFs will be limited.

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:

• Absence of an Active Market Risk - The Fund faces numerous market trading risks, including the potential lack of an active market for Fund shares due to a limited number of market makers or authorized participants. The Fund may rely on a small number of third-party market makers to provide a market for the purchase and sale of shares and market makers are under no obligation to make a market in the Fund's shares. Additionally, only a limited number of institutions act as authorized participants for the Fund and only an authorized participant may engage in creation or redemption transactions directly with the Fund and are not obligated to submit purchase or redemption orders for Creation Units. 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. Any trading halt or other problem relating to the trading activity of these market makers or any issues disrupting the authorized participants' ability to proceed with creation and/or redemption orders could result in a dramatic change in the spread between the Fund's net asset value and the price at which the Fund's shares are trading on the Exchange, which could result in a decrease in value of the Fund's shares. This reduced effectiveness could result in Fund shares trading at a premium or discount to net asset value and also in greater than normal intraday bid-ask spreads for Fund shares.

• 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.

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

• Cap Change Risk - A new Underlying ETF cap is established at the beginning of each Target Outcome Period and is dependent on prevailing market conditions. As a result, a cap may rise or fall from one Target Outcome Period to the next and is unlikely to remain the same for consecutive Target Outcome Periods.

• Capped Upside Risk - Each Underlying ETF's strategy seeks to provide returns (before fees and expenses) that match the price return of SPY for shares acquired on the first day of a Target Outcome Period and held for the entire Target Outcome Period, subject to a pre-determined upside cap. Because the Fund will acquire shares of the Underlying ETFs in connection with creations of new shares of the Fund and during each semi-annual rebalance and Ramp-Up Period, the Fund typically will not acquire Underlying ETF shares on the first day of a Target Outcome Period. Likewise, the Fund will dispose of shares of the Underlying ETFs in connection with redemptions of shares of the Fund and during each semi-annual rebalance, and such disposals typically will not occur on the last day of a Target Outcome Period. In the event that the Fund acquires Underlying ETF shares after the first day of a Target Outcome Period and the Underlying ETF has risen in value to a level near or at the cap (because the Fund's potential gain will be limited to the difference between the Underlying ETF's NAV on the date the Fund purchases Underlying ETF shares and the cap), there may be little or no ability for the Fund to experience an investment gain on its shares, however, the Fund will remain vulnerable to downside risks. This could be true for all of the Underlying ETFs held by the Fund at a certain point in time severely limiting the Fund's ability to participate in gains during that time. If SPY experiences gains during a Target Outcome Period, an Underlying ETF will not participate in those gains beyond the cap. If the Fund buys Underlying ETF shares when the price exceeds the cap, the Fund will not experience any gain regardless of the performance of SPY.

• 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.

• 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.

• Counterparty Risk - Underlying ETF transactions involving a counterparty are subject to the risk that the counterparty will not fulfill its obligation to the Underlying ETF. Counterparty risk may arise because of the counterparty's financial condition (i.e., financial difficulties, bankruptcy, or insolvency), market activities and developments, or other reasons, whether foreseen or not. A counterparty's inability to fulfill its obligation may result in significant financial loss to an Underlying ETF and, in turn, the Fund. An Underlying ETF may be unable to recover its investment from the counterparty or may obtain a limited recovery, and/or recovery may be delayed. The OCC acts as guarantor and central counterparty with respect to the FLEX Options. As a result, the ability of an Underlying ETF to meet its objective depends on the OCC being able to meet its obligations. In the unlikely event that the OCC becomes insolvent or is otherwise unable to meet its settlement obligations, an Underlying ETF and, in turn, the Fund could suffer significant losses.

• 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 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 SPY'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 SPY fall, the value of your investment in the Fund will decline.

• Flex Options Risk - The Underlying ETFs invest in FLEX Options. Trading FLEX Options involves risks different from, or possibly greater than, the risks associated with investing directly in securities. The Underlying ETFs may experience substantial downside 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 Underlying ETFs' 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 Underlying ETFs' shares and result in the Underlying ETFs and, in turn, the Fund being unable to achieve their investment objective. Less liquidity in the trading of the Underlying ETF's FLEX Options could have an impact on the prices paid or received by the Underlying ETFs for the FLEX Options in connection with creations and redemptions of the Underlying ETF's shares. Depending on the nature of this impact to pricing, an Underlying ETF 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 Underlying ETF and whether the Underlying ETF 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 the Underlying ETFs. 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.

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

• Flex Options Valuation Risk - The FLEX Options held by the Underlying ETFs 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 SPY (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 SPY, 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 SPY 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 Underlying ETFs, the ability of the Underlying ETFs to value the FLEX Options becomes more difficult and the judgment of the Underlying ETFs' 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 Underlying ETFs' 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 Underlying ETFs 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 Underlying ETFs.

• Fund-of-Funds Risk - Shareholders of the Fund will experience investment returns that are different than the investment returns provided by an Underlying ETF. The Fund does not itself pursue a defined outcome strategy, nor does the Fund itself provide downside protection against SPY losses. Because the Fund will typically not purchase an Underlying ETF on the first day of a Target Outcome Period, it is not likely that the stated outcome of the Underlying ETF will be realized by the Fund. The Fund will be continuously exposed to the investment profiles of each of the Underlying ETFs during their respective Target Outcome Periods. The Fund, with its aggregate exposure to each of the Underlying ETFs, may have investment returns that are inferior to that of any single Underlying ETF or group of Underlying ETFs over any given time period. In between the semi-annual rebalance period of the Index, because the Fund is not equally weighted on a continuous basis, the Fund may be exposed to one or more Underlying ETFs disproportionately when compared to other Underlying ETFs. In such circumstances, the Fund will be subject to the over-weighted performance of such Underlying ETF. As a shareholder in other ETFs, the Fund bears its proportionate share of each ETF's expenses, subjecting Fund shareholders to duplicative expenses.

• Index or Model Constituent Risk - The Fund may be a constituent of one or more indices or ETF models. As a result, the Fund may be included in one or more index-tracking exchange-traded funds or mutual funds. Being a component security of such a vehicle could greatly affect the trading activity involving the Fund's shares, the size of the Fund and the market volatility of the Fund. Inclusion in an index could increase demand for the Fund and removal from an index could result in outsized selling activity in a relatively short period of time. As a result, the Fund's net asset value could be negatively impacted and the Fund's market price may be below the Fund's net asset value during certain periods. In addition, index rebalances may potentially result in increased trading activity in the Fund's shares.

• Information Technology Companies Risk - SPY invests significantly in information technology companies. Information technology companies produce and provide hardware, software and information technology systems and services. These companies may be adversely affected by rapidly changing technologies, short product life cycles, fierce competition, aggressive pricing and reduced profit margins, the loss of patent, copyright and trademark protections, cyclical market patterns, evolving industry standards and frequent new product introductions. In addition, information technology companies are particularly vulnerable to federal, state and local government regulation, and competition and consolidation, both domestically and internationally, including competition from foreign competitors with lower production costs. Information technology companies also heavily rely on intellectual property rights and may be adversely affected by the loss or impairment of those rights.

• Large Capitalization Companies Risk - SPY invests in the securities of large capitalization companies. Large capitalization companies may grow at a slower rate and be less able to adapt to changing market conditions than smaller capitalization companies. Thus, the return on investment in securities of large capitalization companies may be less than the return on investment in securities of small and/or mid capitalization companies. The performance of large capitalization companies also tends to trail the overall market during different market cycles.

• Management Risk - The Fund is subject to management risk because it is an actively managed portfolio. In managing the Fund's investment portfolio, the portfolio managers will apply investment techniques and risk analyses that may not produce the desired result. There can be no guarantee that the Fund will meet its investment objective.

• Market Fluctuation Tax Risk - The Fund is acquiring shares of the Underlying ETFs in the open market. When the Fund sells shares of the Underlying ETFs in the open market, the Fund will recognize gain or loss on the disposition of the shares, which could have a negative impact on Fund returns. In addition, note that the Fund may, under certain circumstances, effect a portion of its creations and redemptions for cash rather than in-kind. If the Fund effects redemptions for cash, it may be required to sell shares of the Underlying ETFs in order to obtain the cash needed to distribute redemption proceeds. Any recognized gain on these sales by the Fund will generally cause the Fund to recognize a gain it might not otherwise have recognized, or to recognize such gain sooner than would otherwise be required if it were to distribute such shares only in-kind. The Fund intends to distribute these gains to shareholders to avoid being taxed on this gain at the fund level and otherwise comply with the special tax rules that apply to it. This strategy may cause shareholders to be subject to tax on gains they would not otherwise be subject to, or at an earlier date than if they had made an investment in a different ETF. Moreover, cash

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

transactions may have to be carried out over several days if the securities market is relatively illiquid and may involve considerable brokerage fees and taxes. These brokerage fees and taxes, which will be higher than if the Fund sold and redeemed its shares entirely in-kind, will be passed on to those purchasing and redeeming Creation Units in the form of creation and redemption transaction fees. In addition, these factors may result in wider spreads between the bid and the offered prices of the Fund's shares than for ETFs that distribute portfolio securities in-kind. The Fund's use of cash for creations and redemptions could also result in dilution to the Fund and increased transaction costs, which could negatively impact the Fund's ability to achieve its investment objective.

• 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"). 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.

• 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 Fund's investment advisor seek to reduce these operational risks through controls and procedures, there is no way to completely protect against such risks.

• Options Risk - The use of options by the Underlying ETFs involves investment strategies and risks different from those associated with ordinary portfolio securities transactions and depends on the ability of the Underlying ETFs' portfolio managers to forecast market movements correctly. The prices of options are volatile and are influenced by, among other things, actual and anticipated changes in the value of the underlying instrument, or in interest or currency exchange rates, including the anticipated volatility, which in turn are affected by fiscal and monetary policies and by national and international political and economic events. The effective use of options by the Underlying ETFs also depends on the Underlying ETFs' ability to terminate option positions at times deemed desirable to do so. There is no assurance that the Underlying ETFs will be able to effect closing transactions at any particular time or at an acceptable price. In addition, there may at times be an imperfect correlation between the movement in values of options and their underlying securities and there may at times not be a liquid secondary market for certain options.

• Premium/Discount Risk - The market price of the Fund's shares will generally fluctuate in accordance with changes in the Fund's net asset value as well as the relative supply of and demand for shares on the Exchange. The Fund's investment advisor cannot predict whether shares will trade below at or above their net asset value because the shares trade on the Exchange at market prices and not at net asset value. Price differences may be due, in large part, to the fact that supply and demand forces at work in the secondary trading market for shares will be closely related, but not identical, to the same forces influencing the prices of the holdings of the Fund trading individually or in the aggregate at any point in time. However, given that shares can only be purchased and redeemed in Creation Units, and only to and from broker-dealers and large institutional investors that have entered into participation agreements (unlike shares of closed-end funds, which frequently trade at appreciable discounts from, and sometimes at premiums to, their net asset value), the Fund's investment advisor believes that large discounts or premiums to the net asset value of shares should not be sustained. During stressed market conditions, the market for the Fund's shares may become less liquid in response to deteriorating liquidity in the market for the Fund's underlying portfolio holdings, which could in turn lead to differences between the market price of the Fund's shares and their net asset value and the bid/ask spread on the Fund's shares may widen.

• Sector Risk - To the extent the SPY invests a significant portion of its assets in a particular sector, a greater portion of the Underlying ETF's and 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 SPY may underperform the broader market.

• Significant Exposure Risk - The Fund intends to generally rebalance its portfolio to equal weight (i.e., 8.33% per Underlying ETF) semi-annually, in connection with the reset of each Underlying ETF. In between such rebalances, market movements in the prices of the Underlying ETFs may result in the Fund having temporary larger exposures to certain Underlying ETFs compared to others. Under such circumstances, the Fund's returns would be more greatly influenced by the returns of the Underlying ETFs with the larger exposures.

• SPY Equity Risk - Because each Underlying ETF holds FLEX Options that reference SPY, each Underlying ETF has exposure to the equity securities markets. Equity securities prices fluctuate for several reasons, including changes in investors' perceptions of the financial condition of an issuer or the general condition of the relevant equity market, such as market volatility, or when political or economic events affecting

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

an issuer occur. Common stock prices may be particularly sensitive to rising interest rates, as the cost of capital rises and borrowing costs increase. Equity securities may decline significantly in price over short or extended periods of time, and such declines may occur in the equity market as a whole, or they may occur in only a particular country, company, industry or sector of the market.

• SPY Risk - Each Underlying ETF invests in FLEX Options that reference SPY, which subjects the Underlying ETFs to certain of the risks of owning shares of an ETF as well as the types of instruments in which SPY invests. The value of SPY will fluctuate over time based on fluctuations in the values of the securities held by SPY, 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 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.

• Target Outcome Period Risk - Each Underlying ETF's investment strategy is designed to deliver returns that match the price return of SPY if shares are bought on the day on which the Underlying ETF enters into the FLEX Options (i.e., the first day of a Target Outcome Period) and held until those FLEX Options expire at the end of the Target Outcome Period subject to the cap. Because the Fund will acquire shares of the Underlying ETFs in connection with creations of new shares of the Fund and during each semi-annual rebalance, the Fund typically will not acquire Underlying ETF shares on the first day of a Target Outcome Period. Likewise, the Fund will dispose of shares of the Underlying ETFs in connection with redemptions of shares of the Fund and during each semi-annual rebalance, and such disposals typically will not occur on the last day of a Target Outcome Period. In the event the Fund acquires shares after the first day of a Target Outcome Period or disposes of shares prior to the expiration of the Target Outcome Period, the value of the Fund's investment in Underlying ETF shares may not be protected against a decline in the value of SPY and may not participate in a gain in the value of SPY for the Fund's investment period.

• Tax Risk from Investment in Other Investment Companies - The Fund has based its analysis of its qualification as a "regulated investment company" ("RIC") as defined by the Code on the belief that its portfolio funds are themselves RICs. If a portfolio fund were to lose its status as a RIC for purposes of the Code, the Fund may fail its requirement to have a diversified portfolio, and, thus, lose its own RIC status. If the Fund did not qualify as a RIC for any taxable year and certain relief provisions were not available, the Fund's taxable income would be subject to tax at the Fund level and to a further tax at the shareholder level when such income is distributed. In such event, in order to requalify for taxation as a RIC, the Fund might be required to recognize unrealized gains, pay substantial taxes and interest and make certain distributions. This would cause investors to incur higher tax liabilities than they otherwise would have incurred and would have a negative impact on Fund returns. In such event, the Fund's Board of Trustees may determine to reorganize or close the Fund or materially change the Fund's investment objective and strategies. In the event that the Fund fails to qualify as a RIC, the Fund will promptly notify shareholders of the implications of that failure.

• 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 Fund 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 Concentration Risk - An Underlying ETF may be susceptible to an increased risk of loss, including losses due to adverse events that affect the Underlying ETF's investments more than the market as a whole, to the extent that the Underlying ETF's investments are concentrated in the securities and/or other assets of a particular issuer or issuers, country, group of countries, region, market, industry, group of industries, sector, market segment or asset class.

• Underlying ETF Exposure Risk - An investment in the Fund may provide returns that are lower than the returns that an investor could achieve by investing in one or more of the Underlying ETFs alone. Additionally, if one or more of the Underlying ETFs has exceeded its cap at the time that you invest in the Fund, you may derive no benefit from the Fund's investment in that Underlying ETF until the next reset of the Underlying ETF. Likewise, if one or more of the Underlying ETFs has decreased in value below its downside protection at the time that you invest in the Fund, you may derive no downside protection from the Fund's investment in that Underlying ETF. See Capital Protection Risk and Capped Upside Risk above. As a shareholder in other ETFs, the Fund bears its proportionate share of each ETF's expenses, subjecting Fund shareholders to duplicative expenses. The Fund does not itself pursue a target outcome strategy and does not provide any downside protection against Underlying ETF losses.

• Underlying ETF Risk - The Fund's investment in shares of the Underlying ETFs subjects it to the risks of owning the securities held by the Underlying the ETF, as well as the same structural risks faced by an investor purchasing shares of the Fund, including absence of an active market risk, premium/discount risk and trading issues risk. As a shareholder in another ETF, the Fund bears its proportionate share of the ETF's expenses, subjecting Fund shareholders to duplicative expenses.

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

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

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.

You can find the Fund's statutory prospectus and statement of additional information online at https://www.calamos.com/resources/.

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

2020 Calamos Court
Naperville, IL 60563-2787
866.363.9219
www.calamos.com
811-22887

CPSLSUMPRO 090924