Prospectus by Investment Company (Form 497)

Rule 497(e)

File No. 333-191151

CALAMOS ETF TRUST

(the "Trust")

Calamos Bitcoin Structured Alt Protection ETF® - October (the "Fund")

Supplement dated October 7, 2025

to the Fund's Prospectus dated October 1, 2025

This supplement updates certain information contained in the Fund's prospectus and should be attached to the prospectus and retained for future reference.

Capitalized terms not defined herein have the same meaning as in the Fund's prospectus.

As described in the Fund's prospectus, an investment in shares of the Fund is subject to an upside return cap (the "Cap") that represents the maximum percentage return an investor can achieve from an investment in the Fund for the Outcome Period of approximately one year. The Fund's initial Outcome Period begins on October 7, 2025 and ends on October 6, 2026. The Fund's Cap for the Outcome Period beginning on October 7, 2025 is set forth below.

8.47%

(7.78% after taking into account the Fund's management fees)

The Fund's return will be further reduced by brokerage commissions, trading fees, taxes and non-routine or extraordinary expenses not included in the Fund's management fee, as described in the prospectus.

The Fund's prospectus is amended to revise all references to the Cap to reflect the Cap for the initial Outcome Period, as set forth above.