Treatment of Metastatic Castration-Resistant Prostate Cancer With Homologous Recombination Deficiency

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.