The study will have 5 periods: prescreening, screening, double-blind treatment, safety follow-up, and long-term follow-up.~Approximately 550 men with mCSPC will be randomized. Eligible participants will be randomly assigned to either of 2 treatment groups as follows:~Talazoparib in combination with enzalutamide.~Placebo capsules identical in appearance to talazoparib capsules in combination with enzalutamide.~Talazoparib or identical placebo treatment will be blinded. Enzalutamide (160 mg/day) will be open label. The dose of talazoparib/placebo to be given in combination with enzalutamide is 0.5 mg once daily. Participants with moderate renal impairment (eGFR 30-59 mL/min/1.73 m2 by the MDRD equation) at screening may be enrolled and the talazoparib/placebo dose will be 0.35 mg once daily.
The purpose of the study is to evaluate the safety and efficacy of talazoparib in combination with enzalutamide compared with placebo in combination with enzalutamide in participants with DDR-deficient mCSPC.