On August 11, 2023, the Food and Drug Administration approved the fixed-dose combination (FDC) of niraparib and abiraterone acetate (AA), with prednisone (P), for treatment of adult patients with deleterious or suspected deleterious BRCA-mutated (BRCAm) metastatic castration resistant prostate cancer (mCRPC), as determined by an FDA-approved test. Substantial evidence of effectiveness was demonstrated by Cohort 1 of MAGNITUDE (NCT03748641), a multi-cohort study. Cohort 1 was a double-blind trial that randomly assigned 423 patients with mCRPC and homologous recombination repair mutations (HRRm) to receive niraparib 200 mg daily plus AA 1,000 mg daily and P versus placebo plus AAP. The presence of BRCAm was a stratification factor. There was a statistically significant improvement in the primary endpoint of radiographic progression-free survival (rPFS) by blinded independent central review (BICR) in the BRCAm subpopulation: the median rPFS was 16.6 months (95% CI: 13.9, NE) in the niraparib + AAP arm and 10.9 months (95% CI: 8.3, 13.8) in the placebo + AAP arm (HR 0.53; 95% CI: 0.36, 0.79; p=0.0014). There was also a statistically significant improvement in rPFS in the all-HRRm population (intention-to-treat population); however exploratory analyses conducted by the FDA indicated that this improvement was primarily attributed to the subgroup of patients with BRCAm, which supported limiting the indication to that population. Adding niraparib to AAP resulted in increased toxicity, including anemia requiring transfusion in 27% of patients. This article summarizes the data and the FDA's thought process supporting the traditional approval of niraparib plus AA FDC.