Inclusion Criteria:

          -  Be 18 years old at the time the informed consent form is signed

          -  Have a histologically or cytologically confirmed adenocarcinoma or poorly
             differentiated carcinoma of the prostate

          -  Be surgically or medically castrated, with serum testosterone levels of ≤ 50 ng/dL
             (1.73 nM)

          -  Experienced disease progression after having received at least 1 but no more than 2
             prior next-generation androgen receptor-targeted therapies, and 1 prior taxane-based
             chemotherapy, for castration-resistant disease

          -  Have a deleterious mutation in BRCA1/2 or ATM, or molecular evidence of other
             homologous recombination deficiency

        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, mitoxantrone, cyclophosphamide or any
             platinum-based chemotherapy

          -  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 rucaparib