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

Niraparib is an orally available, highly selective poly (adenosine diphosphate \[ADP\]-ribose) polymerase (PARP) inhibitor, with potent activity against PARP-1 and PARP-2 deoxyribonucleic acid (DNA)-repair polymerases. AA is a pro-drug of abiraterone which selectively inhibits the enzyme 17 alpha-hydroxylase/C17,20-lyase (CYP17), that is found in the testes and adrenals (leading to systemic inhibition of testosterone production), as well as in prostate tissues and tumors. The rationale of the study is to investigate the various strengths and formulations of niraparib and AA plus prednisone or prednisolone (P) in metastatic castration resistant prostate cancer (mCRPC) participants with and without homologous recombination repair (HRR) gene alterations. In participants with metastatic prostate cancer, DNA-repair anomalies are found in approximately 15 percent (%) to 20% of tumors. This study consists 4 periods: screening phase (up to 21 days); treatment phase (up to 22 days); extension and long-term extension phases (from day 23 until discontinuation); and post-treatment follow up phase (end of treatment \[EoT\] visit within 30 days after the last dose of study treatment). Total duration of study is up to 1.4 years. Efficacy, safety, pharmacokinetics (PK), and biomarkers will be assessed at specified time points during this study. Participants safety will be monitored throughout the study.