Phase II trial of oral pamiparib in recurrent ovarian cancer after prior PARPi exposure

AIM: To evaluate the efficacy and safety of pamiparib monotherapy in recurrent ovarian cancer (rOC) after prior PARPi exposure. METHODS: This was a prospective clinical trial. Fifteen patients were enrolled between August 2022 and December 2023. Oral pamiparib 60 mg twice daily was administered until conditions specified in the protocol. Primary endpoint was clinical benefit rate ≥ 4 months (CBR4m; percentage of patients who sustained complete response, partial response [PR], and stable disease for at least 4 months). Secondary endpoints included progression-free survival (PFS), overall response rate (ORR), overall survival (OS), and safety. RESULTS: Median number of previous treatment line was 3 (range, 2-6). CBR4m was 26.7% and the study was halted in the first stage according to the pre-set statistical criteria. Two patients achieved PR for an ORR of 13.3%. With a median follow-up of 16.1 months, median PFS and OS were respectively 2.8 (95% confidence interval [CI], 1.6-NR) and 15.6 (95% CI, 8.4-NR) months. Subgroup analyses showed CBR4m of 37.5% (3/8) in BRCAmut and 14.3% (1/7) in BRCAwt cohorts. CA-125 response according to GCIG criteria was observed in 26.7% of patients. There were no treatment-related serious adverse events or deaths. CONCLUSIONS: Pamiparib monotherapy preliminarily showed limited efficacy and acceptable safety profiles in heavily pretreated rOC after prior PARPi exposure. The results suggested that single-agent pamiparib retreatment may not be an effective treatment for this patient population; further investigation of combining PARPi with agents with different mechanisms may be warranted.