Background: Ovarian cancer (OC) is the leading cause of death from gynecologic cancers in US women. Despite high response rates to first-line treatment, ~70% of patients (pts) relapse within 3 years and then remain largely incurable. First-line treatment needs to be improved to achieve long-term remission in pts and improve the cure rate. The Phase III SOLO1 trial showed a meaningful clinical benefit for olap maintenance therapy in newly diagnosed OC pts with a BRCA mutation (Moore et al N Engl J Med 2018). Preliminary data suggest that combining a PD-L1 inhibitor, anti-angiogenic and PARP inhibitor (triplet therapy) may achieve a synergistic antitumor effect. The DUO-O study (NCT03737643) evaluates the efficacy and safety of treatment combinations involving standard-of-care platinum-based chemotherapy (chemo), VEGF inhibitor bev, anti-PD-L1 antibody durva and PARP inhibitor olap, in women with newly diagnosed advanced OC. Methods: Eligible pts for this double-blind, randomized, Phase III study must have newly diagnosed, advanced, high-grade epithelial OC and either have completed primary surgery or plan to have interval debulking surgery. Depending on their tumor BRCA mutation (tBRCAm) status (determined by central test), pts will join one of two independent cohorts. Pts in the non-tBRCAm cohort (n~906) will be randomized (1:1:1) before cycle 2 to: a) chemo + bev + placebo (for 6 cycles) followed by bev (15 mg/kg [total 15 months]) + placebo maintenance treatment (IV and tablets); b) chemo + bev + durva (6 cycles) followed by bev + durva (1120 mg q3w [total 15 months]) + placebo (tablets) maintenance treatment; or c) chemo + bev + durva (6 cycles) followed by bev + durva + olap (300 mg bd tablets [24 months]) maintenance treatment. Pts in the open-label tBRCAm cohort (n~150) will receive 6 cycles of chemo + durva followed by durva + olap maintenance therapy, with optional use of bev. The primary endpoint of progression-free survival will be assessed by modified RECIST 1.1. Key secondary endpoints include overall survival, overall response rate and duration of response. Enrollment began in January 2019. Clinical trial information: NCT03737643