CD274 and peritoneum cancer: Three phase 3 randomized, double-blind, placebo-controlled multicenter studies have explored the effect of chemotherapy ± anti-PD-1/anti-PD-L1 followed by maintenance with anti-PD-L1 and olaparib/niraparib in newly diagnosed advanced ovarian cancer (NCT03737643/DUO-O), BRCA non-mutated advanced epithelial ovarian cancer (NCT03740165/KEYLYNK-001/ENGOT-ov43), and recurrent ovarian, tubal, or peritoneal cancer (NCT03598270).