Calamos Nasdaq-100 Structured Alt Protection ETF - September (CPNS) is an exchange-traded fund that offers investors structured exposure to the Nasdaq-100 Index with downside protection mechanisms targeting zero to negative performance through the September outcome period. The ETF employs a data-driven options strategy involving FLEX options to provide predetermined levels of upside participation in Nasdaq-100 gains while buffering against principal losses up to a specified threshold, typically 10-20%, over the defined term; it resets quarterly or semi-annually with new outcome periods aligned to calendar months like September. Calamos Investments LLC, the fund's sponsor and investment adviser founded in 1970 and headquartered in Naperville, Illinois, manages CPNS as part of its broader suite of structured outcome ETFs, including similar products for other indices and expiration dates such as CPNL (December) and CPNO (October), targeting retail and institutional investors seeking tax-efficient, defined-risk equity alternatives in the U.S. financial markets. Geographically, the fund operates primarily in the United States, listing on the Cboe BZX Exchange and distributing through major broker-dealers nationwide. In recent developments, Calamos Investments expanded its structured protection ETF lineup in 2024-2025 with launches of additional tickers offering varying buffer levels and cap rates, including enhancements to CPNS for improved upside potential amid volatile market conditions; the firm also announced strategic partnerships with platforms like Schwab and Fidelity to broaden distribution and reported strong inflows exceeding $500 million across the series in late 2025, reflecting heightened demand for buffered Nasdaq-100 strategies following tech sector rallies.