1348 Translational biomarkers of response to triplet maintenance in BRCA wildtype recurrent ovarian cancer: OPEB-01/APGOT-OV4

Introduction/Background OPEB-01/APGOT-OV4 was a phase II clinical trial that investigated the efficacy and safety of triplet maintenance (olaparib, pembrolizumab, and bevacizumab) in BRCA wildtype, platinum-sensitive recurrent ovarian cancer. Here, we report the impact of biomarker status (PD-L1 and HRD status) on therapeutic outcomes. Methodology Patients showing a complete or partial response after second-line platinum-based chemotherapy were eligible. The primary endpoint was the 6 months progression-free survival (PFS) rate, with secondary endpoints including PFS, overall survival (OS), and safety. As pre-specified exploratory analysis, biomarkers such as PD-L1 and HRD were investigated. Results The primary endpoint was met, with 6 months PFS rate of 88.6% (95% CI 69.3–92.0). The median PFS was 22.4 months (20.4–∞), and the 12-months PFS rate of 84.0% (95% CI 69.3–92.0), indicating durable responses. Patient demographics were not different with respect to PD-L1 or HRD status. Out of 43 patients with available PD-L1 status, 28 patients had PD-L1 positive tumors (combined positive score CPS ≥ 1), while 15 had PD-L1 negative tumors (CPS Conclusion PD-L1 positive and HRD positive status were each associated with a superior response to triplet maintenance therapy. Disclosures None.