# EDGAR Filing Document

**Accession Number:** 0001579881
**File Stem:** 0001104659-25-090293
**Filing Date:** 2025-9
**Character Count:** 2976
**Document Hash:** 43d62fbdaef3981f5c31009d4dc32697
**Contains OCR:** False
**Source Format:** 

## Filing Content

## Filing Summary
**0001104659-25-090293.hdr.sgml**: 20250916

**ACCESSION NUMBER**: 0001104659-25-090293

**CONFORMED SUBMISSION TYPE**: 497

**PUBLIC DOCUMENT COUNT**: 1

**FILED AS OF DATE**: 20250916

**DATE AS OF CHANGE**: 20250916

**EFFECTIVENESS DATE**: 20250916

**FILER**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** Calamos ETF Trust
- **CENTRAL INDEX KEY:** 0001579881

**ORGANIZATION NAME:**
- **EIN:** 000000000
- **STATE OF INCORPORATION:** DE

**FILING VALUES:**
- **FORM TYPE:** 497
- **SEC ACT:** 1933 Act
- **SEC FILE NUMBER:** 333-191151
- **FILM NUMBER:** 251316242

**BUSINESS ADDRESS:**
- **STREET 1:** 2020 CALAMOS COURT
- **CITY:** NAPERVILLE
- **STATE:** IL
- **ZIP:** 60563
- **BUSINESS PHONE:** 630-245-8394

**MAIL ADDRESS:**
- **STREET 1:** 2020 CALAMOS COURT
- **CITY:** NAPERVILLE
- **STATE:** IL
- **ZIP:** 60563

## Series and Classes Contracts Data

### Calamos S&P 500 Structured Alt Protection ETF - October (Series ID: S000086986)

---

|  |  |
|:---|:---|
| Class Name                                              | Class ID   |
| Calamos S&P 500 Structured Alt Protection ETF - October | C000252656 |

---

## Series and Classes Contracts Data

### Calamos S&P 500 Structured Alt Protection ETF - October (Series ID: S000086986)

| Class ID   | Class Name                                              | Ticker Symbol   |
|:---|:---|:---|
| C000252656 | Calamos S&P 500 Structured Alt Protection ETF - October |  |

Rule 497(e)

File No. 333-191151

**CALAMOS ETF TRUST**

(the "Trust")

**Calamos S&P 500® Structured Alt Protection ETF® – October**

(the "Fund")

Supplement dated September 16, 2025

to the Fund's Prospectus dated October 1, 2024

*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 current Outcome Period ends on September 30, 2025. The next Outcome Period will begin on October 1, 2025 and end on September 30, 2026 (the "Upcoming Outcome Period"). The Fund's anticipated Cap range for the Upcoming Outcome Period beginning on October 1, 2025 is set forth below.

5.70% - 6.70%

(5.01% - 6.01% 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.

On September 30, 2025, the Fund's prospectus will be amended to update all references to the Cap to reflect the Cap for the Upcoming Outcome Period, as described above.