Across pivotal global trials, including ATTRACTION-4, KEYNOTE-859, RATIONALE-305, and CheckMate 649, PD-1 blockade combined with chemotherapy improved outcomes in HER2-negative gastric and GEJ adenocarcinoma, with the greatest benefit observed in tumors with higher PD-L1 expression. The gene discussed is CD274; the disease is gastroesophageal junction adenocarcinoma.