The purpose of this international, phase 2, open-label, 2-arm, response rate study of talazoparib is to assess the efficacy and safety of talazoparib in men with metastatic castration-resistant prostate cancer (CRPC) who previously received taxane-based chemotherapy and progressed on at least 1 novel hormonal agent (enzalutamide and/or abiraterone acetate/prednisone).