0001579881 2026-10-09 2026-10-09 0001579881 ck0001579881:doc_Calamos_Bitcoin_80_Series_Structured_Alt_Protection_ETF_JanuaryMember ck0001579881:S000090058Member 2026-10-09 2026-10-09 0001579881 ck0001579881:doc_Calamos_Bitcoin_80_Series_Structured_Alt_Protection_ETF_JulyMember ck0001579881:S000090060Member 2026-10-09 2026-10-09 0001579881 ck0001579881:doc_Calamos_Bitcoin_80_Series_Structured_Alt_Protection_ETF_OctoberMember ck0001579881:S000090061Member 2026-10-09 2026-10-09 <p style="font: 11pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: center"><span style="font-family: Times New Roman, Times, Serif"><b>CALAMOS ETF TRUST</b></span><br/> (the “Trust”)</p><p style="font: 11pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: center"> </p><p style="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0"> </p> <p style="font: 11pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: center">Supplement dated October 9, 2026 to the Prospectuses and Summary Prospectuses dated November 28, 2025, as amended, with respect to:</p><p style="font: 11pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: center"> </p><p style="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0"> </p> <p style="font: 11pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: center">Calamos Bitcoin 80 Series Structured Alt Protection ETF® – January (CBTJ), Calamos Bitcoin 80 Series Structured Alt Protection ETF® – April (CBTA), Calamos Bitcoin 80 Series Structured Alt Protection ETF® – July (CBTY), and Calamos Bitcoin 80 Series Structured Alt Protection ETF® – October (CBTO), and Calamos Bitcoin Structured Alt Protection ETF® – October (CBOO)</p><p style="font: 11pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: center"> </p><p style="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0"> </p> <p style="font: 11pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: justify"><i>This supplement updates certain information contained in each of the Prospectuses and Summary Prospectuses noted above and should be attached to the Prospectuses and Summary Prospectuses and retained for future reference.</i></p><p style="font: 11pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: justify"> </p> <p style="font: 11pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: justify"><i>Capitalized terms and certain other terms used in this supplement, unless otherwise defined in this supplement, have the meanings assigned to them in the Prospectuses and Summary Prospectuses.</i></p><p style="font: 11pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: justify"> </p><p style="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0"> </p> <p style="font: 11pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: justify">Effective immediately, the following changes are made to the Prospectuses (and Summary Prospectuses, where noted below):</p> <p style="font: 11pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: center"><span style="font-family: Times New Roman, Times, Serif"><b>CALAMOS ETF TRUST</b></span><br/> (the “Trust”)</p><p style="font: 11pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: center"> </p><p style="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0"> </p> <p style="font: 11pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: center">Supplement dated October 9, 2026 to the Prospectuses and Summary Prospectuses dated November 28, 2025, as amended, with respect to:</p><p style="font: 11pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: center"> </p><p style="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0"> </p> <p style="font: 11pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: center">Calamos Bitcoin 80 Series Structured Alt Protection ETF® – January (CBTJ), Calamos Bitcoin 80 Series Structured Alt Protection ETF® – April (CBTA), Calamos Bitcoin 80 Series Structured Alt Protection ETF® – July (CBTY), and Calamos Bitcoin 80 Series Structured Alt Protection ETF® – October (CBTO), and Calamos Bitcoin Structured Alt Protection ETF® – October (CBOO)</p><p style="font: 11pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: center"> </p><p style="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0"> </p> <p style="font: 11pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: justify"><i>This supplement updates certain information contained in each of the Prospectuses and Summary Prospectuses noted above and should be attached to the Prospectuses and Summary Prospectuses and retained for future reference.</i></p><p style="font: 11pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: justify"> </p> <p style="font: 11pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: justify"><i>Capitalized terms and certain other terms used in this supplement, unless otherwise defined in this supplement, have the meanings assigned to them in the Prospectuses and Summary Prospectuses.</i></p><p style="font: 11pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: justify"> </p><p style="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0"> </p> <p style="font: 11pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: justify">Effective immediately, the following changes are made to the Prospectuses (and Summary Prospectuses, where noted below):</p> <p style="font: 11pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: center"><span style="font-family: Times New Roman, Times, Serif"><b>CALAMOS ETF TRUST</b></span><br/> (the “Trust”)</p><p style="font: 11pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: center"> </p><p style="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0"> </p> <p style="font: 11pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: center">Supplement dated October 9, 2026 to the Prospectuses and Summary Prospectuses dated November 28, 2025, as amended, with respect to:</p><p style="font: 11pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: center"> </p><p style="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0"> </p> <p style="font: 11pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: center">Calamos Bitcoin 80 Series Structured Alt Protection ETF® – January (CBTJ), Calamos Bitcoin 80 Series Structured Alt Protection ETF® – April (CBTA), Calamos Bitcoin 80 Series Structured Alt Protection ETF® – July (CBTY), and Calamos Bitcoin 80 Series Structured Alt Protection ETF® – October (CBTO), and Calamos Bitcoin Structured Alt Protection ETF® – October (CBOO)</p><p style="font: 11pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: center"> </p><p style="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0"> </p> <p style="font: 11pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: justify"><i>This supplement updates certain information contained in each of the Prospectuses and Summary Prospectuses noted above and should be attached to the Prospectuses and Summary Prospectuses and retained for future reference.</i></p><p style="font: 11pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: justify"> </p> <p style="font: 11pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: justify"><i>Capitalized terms and certain other terms used in this supplement, unless otherwise defined in this supplement, have the meanings assigned to them in the Prospectuses and Summary Prospectuses.</i></p><p style="font: 11pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: justify"> </p><p style="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0"> </p> <p style="font: 11pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: justify">Effective immediately, the following changes are made to the Prospectuses (and Summary Prospectuses, where noted below):</p> 2025-11-28 Calamos Bitcoin 80 Series Structured Alt Protection ETF® – January Calamos Bitcoin 80 Series Structured Alt Protection ETF® – July Calamos Bitcoin 80 Series Structured Alt Protection ETF® – October <p style="font: 11pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: justify"><span style="font-family: Times New Roman, Times, Serif"><b>1. <span style="text-decoration:underline">Principal Investment Strategies – Floor Threshold (CBTJ, CBTY and CBTO)</span>. </b></span>For each of the Calamos Bitcoin 80 Series Structured Alt Protection ETF® – January (CBTJ), Calamos Bitcoin 80 Series Structured Alt Protection ETF® – July (CBTY), and Calamos Bitcoin 80 Series Structured Alt Protection ETF® – October (CBTO), the first sentence in the second paragraph under the “Principal Investment Strategies” section on page 2 of the Fund’s summary prospectus and prospectus is removed and replaced with the following:</p><p style="font: 11pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: justify"> </p> <p style="font: 11pt Times New Roman, Times, Serif; margin: 0pt 0.5in; text-align: justify">The Fund seeks to provide protection against a loss exceeding 20% (by providing a Floor against the negative price return of Spot bitcoin exceeding 20%) prior to taking into account any fees or expenses charged to the Fund.</p><p style="font: 11pt Times New Roman, Times, Serif; margin: 0pt 0.5in; text-align: justify"> </p><p style="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0"> </p><p style="font: 11pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: center"><b>Please retain this supplement for future reference</b></p> <p style="font: 11pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: justify"><span style="font-family: Times New Roman, Times, Serif"><b>1. <span style="text-decoration:underline">Principal Investment Strategies – Floor Threshold (CBTJ, CBTY and CBTO)</span>. </b></span>For each of the Calamos Bitcoin 80 Series Structured Alt Protection ETF® – January (CBTJ), Calamos Bitcoin 80 Series Structured Alt Protection ETF® – July (CBTY), and Calamos Bitcoin 80 Series Structured Alt Protection ETF® – October (CBTO), the first sentence in the second paragraph under the “Principal Investment Strategies” section on page 2 of the Fund’s summary prospectus and prospectus is removed and replaced with the following:</p><p style="font: 11pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: justify"> </p> <p style="font: 11pt Times New Roman, Times, Serif; margin: 0pt 0.5in; text-align: justify">The Fund seeks to provide protection against a loss exceeding 20% (by providing a Floor against the negative price return of Spot bitcoin exceeding 20%) prior to taking into account any fees or expenses charged to the Fund.</p><p style="font: 11pt Times New Roman, Times, Serif; margin: 0pt 0.5in; text-align: justify"> </p><p style="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0"> </p><p style="font: 11pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: center"><b>Please retain this supplement for future reference</b></p> <p style="font: 11pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: justify"><span style="font-family: Times New Roman, Times, Serif"><b>1. <span style="text-decoration:underline">Principal Investment Strategies – Floor Threshold (CBTJ, CBTY and CBTO)</span>. </b></span>For each of the Calamos Bitcoin 80 Series Structured Alt Protection ETF® – January (CBTJ), Calamos Bitcoin 80 Series Structured Alt Protection ETF® – July (CBTY), and Calamos Bitcoin 80 Series Structured Alt Protection ETF® – October (CBTO), the first sentence in the second paragraph under the “Principal Investment Strategies” section on page 2 of the Fund’s summary prospectus and prospectus is removed and replaced with the following:</p><p style="font: 11pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: justify"> </p> <p style="font: 11pt Times New Roman, Times, Serif; margin: 0pt 0.5in; text-align: justify">The Fund seeks to provide protection against a loss exceeding 20% (by providing a Floor against the negative price return of Spot bitcoin exceeding 20%) prior to taking into account any fees or expenses charged to the Fund.</p><p style="font: 11pt Times New Roman, Times, Serif; margin: 0pt 0.5in; text-align: justify"> </p><p style="font: 10pt Times New Roman, Times, Serif; margin: 0pt 0"> </p><p style="font: 11pt Times New Roman, Times, Serif; margin: 0pt 0; text-align: center"><b>Please retain this supplement for future reference</b></p> 497 N-1A 0001579881 false 2026-10-09 Calamos ETF Trust