Background: There is a significant unmet need to develop new regimens for BRCA1/2-nonmutated advanced ovarian cancer (OC). The PARP inhibitor olaparib is approved for women with platinum-sensitive, recurrent OC regardless of BRCA1/2 status and, more recently, for newly diagnosed women with BRCA-mutated OC. In the TOPACIO/KEYNOTE-162 study, the combination of the PD-1–blocking antibody pembrolizumab (pembro) and niraparib demonstrated efficacy in platinum-resistant relapsed OCirrespective of BRCA1/2 status. ENGOT-OV43/KEYLYNK-001 (ClinicalTrials.gov, NCT03740165) is a phase 3, randomized, double-blind, active- and placebo-controlled study of pembro plus paclitaxel-carboplatin chemotherapy (CT) followed by olaparib maintenance for first-line treatment of patients with BRCA1/2-nonmutated advanced epithelial OC (EOC). Methods: Patients with stage III or IV BRCA-nonmutated EOC, primary peritoneal cancer, or fallopian tube cancer will be stratified by surgery status (no residual tumor after primary debulking surgery [PDS], residual tumor after PDS, or planned interval debulking), bevacizumab use, and PD-L1 status (combined positive score < 10 or ≥10). After one lead-in cycle of CT, patients will be randomized 1:1:1 to receive: CT + pembro followed by olaparib maintenance; CT + pembro followed by placebo; or CT + placebo followed by placebo. The CT regimen will be administered for 5 cycles, and pembro 200 mg Q3W will be administered for 35 infusions. Olaparib 300 mg BID maintenance therapy will start after the end of CT as concomitant treatment with pembro until discontinuation or for 2 years if the patient has a complete response. Bevacizumab use is permitted at investigator’s discretion and determined prerandomization. Primary endpoints are investigator-assessed progression-free survival (PFS) per RECIST 1.1 criteria and overall survival. Key secondary endpoints are PFS per RECIST 1.1 assessed by blinded independent central review, PFS after next-line treatment, and safety. Enrollment is currently ongoing. Clinical trial information: NCT03740165