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

An Open-label, Randomized Study to Assess the Relative Bioavailability (BA) and Bioequivalence (BE) of Comparative Formulations of Niraparib and Abiraterone Acetate (AA) in Men With Prostate Cancer

The purpose of this study is to determine the relative bioavailability (rBA; Period 1) and bioequivalence (BE; Period 2 and 3) of various strengths and formulations of niraparib and abiraterone acetate (AA) at steady state under modified fasted conditions in participants with metastatic castration-resistant prostate cancer (mCRPC).

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.

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