Sintilimab Plus Gossypol Acetate in Advanced Colorectal Cancer

This is a single-center, open-label, single-arm, exploratory phase II clinical trial designed to evaluate the preliminary efficacy and safety of sintilimab in combination with oral gossypol acetate in patients with advanced pMMR/MSS colorectal cancer after failure of at least two prior lines of standard therapy. Eligible participants will have histologically or cytologically confirmed advanced colorectal adenocarcinoma, measurable disease according to RECIST version 1.1, ECOG performance status of 0 or 1, and adequate organ function. Participants will receive oral gossypol acetate once daily, followed by sintilimab administered intravenously every 3 weeks after a gossypol acetate lead-in period. The primary outcome is objective response rate assessed by RECIST version 1.1. Secondary outcomes include disease control rate, progression-free survival, overall survival, duration of response, and safety.