LBA37 Atezolizumab (atezo) combined with platinum-based chemotherapy (CT) and maintenance niraparib for recurrent ovarian cancer (rOC) with a platinum-free interval (TFIp) >6 months: Primary analysis of the double-blind placebo (pbo)-controlled ENGOT-Ov41/GEICO 69-O/ANITA phase III trial

Standard therapy for late-relapsing (TFIp >6 mo) rOC includes PARPi maintenance if disease responds to platinum-based CT. ANITA (NCT03598270) is the first-reported phase 3 trial evaluating atezo with platinum-based CT and maintenance PARPi in late-relapsing rOC. Eligible pts had measurable high-grade serous, endometrioid or undifferentiated rOC, ≤2 prior CT lines (most recent including platinum) and TFIp >6 mo. Prior PARPi for rOC and/or prior immune checkpoint inhibitor were prohibited. Pts were stratified by carboplatin (carbo) doublet (paclitaxel, gemcitabine or pegylated liposomal doxorubicin [PLD]), TFIp (6–12 vs >12 mo), BRCA status (mutated vs non-mutated) and PD-L1 status (PD-L1-expressing immune cells on <1% vs ≥1% tumour area vs non-informative by SP142). Pts were randomised 1:1 to a carbo doublet + atezo or pbo for 6 cycles followed (in pts without progression on CT) by maintenance niraparib at an individualised starting dose + atezo or pbo until disease progression. The atezo dose was 1200 mg q3w or 840 mg q2w depending on the CT regimen. The primary endpoint was investigator-assessed progression-free survival (PFS) per RECIST v1.1. Between Nov 2018 and Jan 2022, 417 pts were randomised (14% BRCAm, 36% PD-L1+, 66% TFIp >12 mo, 11% prior PARPi after front-line CT, 54% prior bevacizumab); most (71%) received carbo–PLD and 74% began maintenance. At the data cut-off (15 Apr 2023), median follow-up was 36 mo. PFS results (Table) were consistent in key subgroups. Overall response to CT was 43% (95% CI 36–49%) and 45% (95% CI 39–52%) in the pbo and atezo arms, respectively. The safety profile was as expected from prior experience of these drugs.Table: LBA37PFSPbo + CT → pbo + niraparib (n=209)Atezo + CT → atezo + niraparib (n=208)All ptsEvents, n (%)174 (83)170 (82)Hazard ratio (95% CI)0.89 (0.71–1.10); p=0.28Median, mo (95% CI)10.1 (9.2–11.2)11.2 (10.1–12.1)PD-L1-positive subgroupEvents, n/N (%)60/73 (82)61/76 (80)Hazard ratio (95% CI)0.87 (0.61–1.25)aMedian, mo (95% CI)11.1 (9.7–12.7)12.8 (10.2–15.4)PD-L1-negative subgroupEvents, n/N (%)92/112 (82)97/117 (83)Hazard ratio (95% CI)0.93 (0.70–1.24)aMedian, mo (95% CI)9.2 (8.3–11.1)10.5 (9.2–11.8)aUnadjusted estimate. Open table in a new tab aUnadjusted estimate. Combining atezo with CT and maintenance niraparib for late-relapsing rOC did not significantly improve PFS or ORR.