Inclusion Criteria:

• Male patients, ≥ 18 years of age.
• Diagnosis of prostate adenocarcinoma.
• Willing to provide an archival tumor tissue sample or a fresh tumor tissue sample. If  germline positive for deleterious germline or somatic homologous recombination repair  (HRR) gene mutations, an archived or fresh tumor tissue sample is not required.
• Metastatic disease documented by ≥ 1 bone lesion(s) on Technetium-99m (99mTc) bone scan. Participants with a single bone lesion must have  confirmation of bone metastasis by computed tomography (CT) or magnetic resonance imaging (MRI).
• Androgen deprivation therapy (either medical or surgical castration) must have been started ≥ 14 days prior to randomization and willing to continue through the treatment  phase. Participants who start a gonadotropin-releasing hormone (GnRH) agonist less  than or equal to (≤) 28 days prior to randomization will be required to take a  first-generation anti-androgen for ≥ 14 days prior to randomization. The anti-androgen  must be discontinued prior to randomization.
• Other allowed prior therapy for metastatic castration-sensitive prostate cancer (mCSPC):
  • maximum of 1 course of radiation or surgical intervention to manage  symptoms of prostate cancer. Radiation with curative intent is not allowed. Radiation  must be completed prior to randomization;
  • ≤ 6 months of androgen deprivation  therapy (ADT) prior to randomization; and
  • 30 days of abiraterone acetate + prednisone (AA-P) allowed if required.

Exclusion Criteria:

• Patients < 18 years of age.
• Pathological finding consistent with small cell ductal or neuroendocrine carcinoma of  the prostate.
• Prior treatment with a poly (adenosine diphosphate-ribose) polymerase (inhibitor)  (PARP) inhibitor.
• History of adrenal dysfunction.
• Long-term use of systemically administered corticosteroids (greater than [>] 5  milligrams [mg] of prednisone or the equivalent) during the study is not allowed.  Short-term use (≤ 4 weeks, including taper) and locally administered steroids (for example, inhaled, topical, ophthalmic, and intra-articular) are allowed, if clinically indicated.
• History or current diagnosis of myelodysplastic syndrome (MDS)/ acute myeloid leukemia (AML).