Efficacy and safety of retifanlimab in gastrointestinal malignancies: A systematic review of clinical trials.

841 Background: Retifanlimab is a humanized anti–PD-1 monoclonal antibody, recently approved in May 2025, for advanced squamous cell carcinoma of the anal canal (SCAC) as monotherapy or in combination with carboplatin and paclitaxel. We conducted a systematic review to evaluate the available evidence on its efficacy and safety in gastrointestinal (GI) malignancies. This review summarizes published Phase I–III clinical trials focusing on objective response rate (ORR), progression-free survival (PFS), overall survival (OS), duration of response (DOR), adverse events (AEs), and immune-related adverse events (irAEs). Methods: A comprehensive literature search of peer-reviewed publications was conducted on PubMed, Cochrane, Embase, Scopus and major conference proceedings through August 2025, to identify interventional trials of retifanlimab in GI cancers, including anal, gastric/gastroesophageal, colorectal, and pancreatic malignancies. Studies reporting efficacy and safety outcomes were included. Results: Three clinical trials evaluating retifanlimab in GI cancers met the inclusion criteria. Two trials in locally recurrent or metastatic SCAC demonstrated meaningful clinical activity. In the Phase II POD1UM-202 trial (n=94), retifanlimab monotherapy achieved an ORR of 13.8% with a median DOR of 9.5 months in platinum-refractory SCAC. Median PFS and OS were 2.3 and 10.1 months, respectively. In the Phase III POD1UM-303/InterAACT 2 trial (n=308), adding retifanlimab to carboplatin-paclitaxel significantly improved median PFS (9.3 vs 7.4 months, hazard ratio [HR] 0.63, P