A Study of Comparative Formulations of Niraparib and Abiraterone Acetate (AA) in Men With Prostate Cancer

Inclusion Criteria: * Histologically or cytologically confirmed adenocarcinoma of the prostate * Diagnosed with metastatic castration-resistant prostate cancer (mCRPC), who in the opinion of the investigator may benefit from treatment in this study * Able to continue gonadotropin-releasing hormone analogues (GnRHa) therapy during the study if not surgically castrate (that is, participants who have not undergone bilateral orchiectomy) * Eastern Cooperative Oncology Group Performance Status (ECOG PS) of less than or equal to (\<=) 1 * Willing to provide a tumor sample (archival) for determination of homologous recombination repair (HRR) gene alteration status Exclusion Criteria: * Symptomatic brain metastases * Prior disease progression during treatment with abiraterone acetate (AA) alone or when combined with a poly adenosine diphosphate (ADP)-ribose polymerase inhibitor (PARPi). Prior discontinuation of treatment with AA or PARPi due to AA- or PARPi related toxicity. * History or current diagnosis of myelodysplastic syndrome (MDS)/ acute myeloid leukemia (AML) * Known allergies, hypersensitivity, or intolerance to niraparib or AA or the corresponding excipients of niraparib/AA * Any medical condition that would make prednisone/prednisolone use contraindicated