Background: Olaparib (Lynparza) is an oral PARP inhibitor indicated in the EU for the maintenance treatment of patients (pts) with platinum-sensitive relapsed BRCA-mutated high grade serous ovarian cancer (HGSOC). Bevacizumab is an anti-VEGF monoclonal antibody indicated in the EU in first line or relapse for the treatment of OC in combination with specific chemotherapeutic agents. Bevacizumab treatment is associated with increasing hypoxia-induced homologous recombination repair deficiencies in tumor cells, and is hypothesized to increase ovarian tumor sensitivity to olaparib. Methods: PAOLA-1 (ENGOT-ov25) is a randomized, placebo-controlled trial evaluating the efficacy and safety of olaparib (tablet formulation) in pts with advanced HGSOC receiving bevacizumab maintenance therapy. Eligible pts must be in complete or partial response following first-line platinum chemotherapy plus bevacizumab, and for whom bevacizumab maintenance therapy is planned. All pts will undergo tumor BRCAtesting prior to randomization. Approximately 612 European and 24 Japanese pts will be randomized 2:1 to olaparib 300 mg twice daily or placebo for up to 24 months. All pts will receive standard maintenance care of bevacizumab (15 mg/kg every three weeks) for up to 15 months. PFS will be evaluated using a log-rank test stratified by response to first-line treatment and BRCA mutation status. Central BRCA testing (tumor) for all pts will be identified among five screening platforms in France. Tumor BRCA test results have to be available within two months of sample provision. Final analyses will be performed after 372 PFS events. The first pt from eight ENGOT groups plus Japan (10 participating countries) was randomized in July 2015. As of 31 December 2015, 44 pts have been randomized and the average period between the provision of a tumor sample and returned BRCA test result is 37 days (range). Last pt treatment completion is expected Q3 2018, with last pt follow up in Q3 2021. Clinical trial information: NCT02477644