O9-1 Updated results of a phase 2 study of niraparib in heavily pretreated high-grade serous ovarian cancer patients in Japan

Niraparib is an orally available, potent, highly selective inhibitor of PARP1/2. The results of an overseas phase 2 study (QUADRA study) showed the efficacy of niraparib monotherapy in patients with advanced, relapsed epithelial ovarian cancer who received 3 or more prior lines of chemotherapy. A significant effect was reported in platinum-sensitive, homologous recombination (HR) deficient patients. To date, niraparib demonstrated efficacy for Japanese women and the efficacy was considered comparable to that in an equivalent population of non-Japanese women. We report an updated analysis of Japanese women with heavily pretreated ovarian cancer from NCT03759600. This phase 2 open-label, single-arm study enrolled Japanese women with platinum-sensitive, HR deficiency-positive advanced, relapsed, high-grade serous ovarian cancer who had completed 3-4 lines of chemotherapy. Niraparib was administered orally, 300mg once daily in continuous 28-day cycles until progressive disease or unacceptable toxicity. The primary endpoint was objective response rate (ORR) assessed by the investigator using RECIST version 1.1. Secondary endpoints included disease control rate, progression free survival (PFS) and incidence of treatment-emergent adverse events (TEAEs). Twenty women were enrolled from 17 sites between Jan 2019 and Apr 2019. The confirmed ORR was 60.0% (12/20), including 2 complete responses and 10 partial responses. Disease control rate was 90.0% (18/20). The median PFS was 8.3 months with a median follow-up of 10.9 months. Dose modification occurred in 80.0% (16/20) with relative dose intensity (RDI) of 67.0% (201.1 mg daily) for niraparib. The common TEAEs reported (>50%) were anemia (70.0%), nausea (60.0%), and platelet count decreased (55.0%). This updated analysis demonstrated both efficacy and acceptable safety with appropriate dose modification in this heavily pre-treated population.