A Study of Rucaparib Versus Physician's Choice of Therapy in Participants With Metastatic Castration-resistant Prostate Cancer and Homologous Recombination Gene Deficiency

Inclusion Criteria: * Be 18 years old at the time the informed consent is signed * Have a histologically or cytologically confirmed adenocarcinoma or poorly differentiated carcinoma of the prostate that is metastatic * Be surgically or medically castrated, with serum testosterone levels of ≤ 50 ng/dL (1.73 nM) * Be eligible for treatment with physician's choice of comparator treatment (abiraterone acetate, enzalutamide or docetaxel) * Experienced disease progression after having received 1 prior next generation androgen receptor-targeted therapy * Have a deleterious mutation in a BRCA1/2 or ATM gene Exclusion Criteria: * Active second malignancy, with the exception of curatively treated non melanoma skin cancer, carcinoma in situ, or superficial bladder cancer * Prior treatment with any PARP inhibitor * Prior treatment with chemotherapy for metastatic castration-resistant prostate cancer * Symptomatic and/or untreated central nervous system metastases * Pre-existing duodenal stent and/or any gastrointestinal disorder or defect that would, in the opinion of the investigator, interfere with absorption of study drug