Talazoparib + Enzalutamide vs. Enzalutamide Monotherapy in mCRPC

Inclusion Criteria: Histologically or cytologically confirmed adenocarcinoma of the prostate without small cell or signet cell features Asymptomatic or mildly symptomatic metastatic castration resistant prostate cancer (mCRPC) (score on BPI-SF Question #3 must be \< 4). For enrollment into Part 2 only (optional in Part 1): assessment of DDR mutation status Consent to a saliva sample collection for a germline comparator unless prohibited by local regulations or ethics committee decision (optional for patients in Part 1). Surgically or medically castrated, with serum testosterone ≤ 50 ng/dL (≤ 1.73 nmol/L) at screening. Metastatic disease in bone documented on bone scan or in soft tissue documented on CT/MRI scan. Progressive disease at study entry in the setting of medical or surgical castration as defined by 1 or more of the following 3 criteria: * Prostate specific antigen (PSA) progression defined by a minimum of 2 rising PSA values from 3 consecutive assessments with an interval of at least 7 days between assessments.. * Soft tissue disease progression as defined by RECIST 1.1. * Bone disease progression defined by Prostate Cancer Working Group 3 (PCWG3) with 2 or more new metastatic bone lesions on a whole body radionuclide bone scan. Ongoing bisphosphonate or denosumab use prior to Day 1 (Part 1) or randomization (Part 2) is allowed but not mandatory. Eastern Cooperative Oncology Group (ECOG) performance status ≤ 1. Life expectancy ≥ 12 months as assessed by t…