This is a global, Phase 2, open-label study of pamiparib in approximately 100 participants with metastatic castration-resistant prostate cancer (mCRPC) positive for circulating tumor cells (CTC) with homologous recombination deficiency (CTC-HRD). Participants in Cohort 1 will include 50 mCRPC participants with CTC-HRD-positive, measurable metastatic disease (soft tissue with/without bone lesions), and positive BRCA1/2 mutation or negative/unknown BRCA1/2 mutation. Cohort 2 will include 30 mCRPC CTC-HRD positive participants with bone metastasis only and positive or negative/unknown BRCA1/2. Cohort 3 and 4 will include 20 mCRPC CTC-HRD negative/unknown participants with BRCA1/2 positive mutations, metastatic disease (measurable soft tissue with/without bone), and bone only. Participants will undergo PSA level assessments approximately every 4 weeks as well as tumor assessments every 8 weeks for 24 weeks and the every 12 weeks, or as clinically indicated. Administration of pamiparib will continue until disease progression, unacceptable toxicity, death or another discontinuation criterion is met.
This study is designed to evaluate the efficacy of pamiparib in participants with metastatic castration-resistant prostate cancer (mCRPC) positive for circulating tumor cells (CTC) with homologous recombination deficiency (CTC-HRD). All participants will receive pamiparib. The purpose of this study is to demonstrate that pamiparib will improve Objective Response Rate (ORR) and Prostate-Specific Antigen (PSA) response rate