An Efficacy and Safety Study of Niraparib in Men With Metastatic Castration-Resistant Prostate Cancer and DNA-Repair Anomalies

Inclusion Criteria:

* Histologically confirmed prostate cancer (mixed histology is acceptable, with the exception of the small cell pure phenotype, which is excluded)
* Received a taxane-based chemotherapy for the treatment of metastatic prostate cancer with evidence of disease progression on or after treatment, or discontinued from a taxane-based chemotherapy due to an adverse event
* Received a second-generation or later androgen receptor (AR)-targeted therapy (for example, abiraterone acetate plus prednisone, enzalutamide, apalutamide) for the treatment of metastatic prostate cancer with evidence of disease progression or non-metastatic castration-resistant prostate cancer with evidence of subsequent metastasis
* Biomarker-positive by at least one of the following criteria: (a) Biallelic deoxyribonucleic acid (DNA)-repair anomaly based on a sponsor validated blood or tissue assay; (b) Germline pathogenic Breast Cancer gene (BRCA) 1 or BRCA2 by any test (somatic local results must be confirmed as positive by the sponsor-validated assay before dosing)
* Progression of metastatic prostate cancer in the setting of castrate levels of testosterone or history of bilateral orchiectomy at study entry

Exclusion Criteria:

* Prior treatment with a poly (adenosine diphosphate \[ADP\] ribose) polymerase (PARP) inhibitor
* Prior platinum-based chemotherapy for the treatment of prostate cancer
* Known history or current diagnosis of myelodysplastic syndrome (MDS)/acute myeloid leukemia (AML)
* Symptomatic or impending cord compression
* Symptomatic brain metastases