Atezolizumab Combined With Platinum and Maintenance Niraparib for Recurrent Ovarian Cancer With a Platinum-Free Interval >6 Months: ENGOT-OV41/GEICO 69-O/ANITA Phase III Trial

PURPOSE To evaluate atezolizumab combined with platinum-based chemotherapy (CT) followed by maintenance niraparib for late-relapsing recurrent ovarian cancer. METHODS The multicenter placebo-controlled double-blind randomized phase III ENGOT-OV41/GEICO 69-O/ANITA trial (ClinicalTrials.gov identifier: NCT03598270 ) enrolled patients with measurable high-grade serous, endometrioid, or undifferentiated recurrent ovarian cancer who had received one or two previous CT lines (most recent including platinum) and had a treatment-free interval since last platinum (TFIp) of >6 months. Patients were stratified by investigator-selected carboplatin doublet, TFIp, BRCA status, and PD-L1 status in de novo biopsy and randomly assigned 1:1 to receive either atezolizumab or placebo throughout standard therapy comprising six cycles of a carboplatin doublet followed (in patients with response/stable disease) by maintenance niraparib until progression. The primary end point was investigator-assessed progression-free survival (PFS) per RECIST v1.1. RESULTS Between November 2018 and January 2022, 417 patients were randomly assigned (15% BRCA- mutated, 36% PD-L1–positive, 66% TFIp >12 months, 11% previous poly [ADP-ribose] polymerase inhibitor after frontline CT, and 53% previous bevacizumab). Median follow-up was 28.6 months (95% CI, 26.6 to 30.5 months). Atezolizumab did not significantly improve PFS (hazard ratio, 0.89 [95% CI, 0.71 to 1.10]; P = .28). Median PFS was 11.2 months (95% CI, 10.1 to 12.1 months) with atezolizumab versus 10.1 months (95% CI, 9.2 to 11.2 months) with standard therapy. Subgroup analyses generally showed consistent results, including analyses by PD-L1 status. The objective response rate (ORR) was 45% (95% CI, 39 to 52) with atezolizumab and 43% (95% CI, 36 to 49) with standard therapy. The safety profile was as expected from previous experience of these drugs. CONCLUSION Combining atezolizumab with CT and maintenance niraparib for late-relapsing recurrent ovarian cancer did not significantly improve PFS or the ORR.