Objective. To evaluate secondary efficacy endpoints and safety for the ENGOT-OV16/NOVA (NCT01847274) trial of niraparib maintenance therapy after extended follow-up and vital-status-data retrieval. Previously reported analyses (data cutoff, October 1, 2020) indicated benefit of niraparib maintenance therapy beyond first progression, but overall survival (OS) analyses were limited by missing data. Methods. Patients were randomized 2:1 to niraparib (300 mg once daily) or placebo. A vital status check was extended to retrieve last-known-alive status for patients with missing survival data. Prespecified secondary efficacy outcomes (OS, chemotherapy-free interval [CFI], time to first subsequent therapy [TFST], PFS2, time to second subsequent therapy [TSST]) and safety are reported based on the extended data cutoff (March 31, 2021). Results. Survival status was available for 97.6% (540/553) of randomized patients (germline BRCA [gBRCA]mutated, 203; non-gBRCA-mutated, 350). Median OS with niraparib and placebo was 40.9 and 38.1 months, respectively, in the gBRCA-mutated cohort (hazard ratio [HR], 0.85; 95% confidence interval [CI], 0.61-1.20) and 31.0 and 34.8 months, respectively, in the non-gBRCA-mutated cohort (HR, 1.06; 95% CI, 0.81-1.37). Medians for CFI, TFST, PFS2, and TSST numerically favored niraparib in both cohorts. No new safety signals were detected. Conclusions. OS did not significantly differ between treatment arms. Prespecified secondary efficacy endpoints numerically favored niraparib. Long-term safety remained consistent with the established niraparib safety profile. Taken together with the significant improvements in PFS observed in the primary analysis, these data support a favorable overall benefit-risk profile for niraparib in the recurrent OC maintenance setting. (c) 2025 Published by Elsevier Inc.