Olaparib (PARP inhibitor) + Abiraterone Shows BRCA2-Driven Benefit in 1L mCRPC

Olaparib is an oral PARP inhibitor combined here with abiraterone, a CYP17 androgen-biosynthesis inhibitor, plus prednisone/prednisolone in the randomized, double-blind Phase 3 PROpel trial (NCT03732820) in first-line metastatic castration-resistant prostate cancer (mCRPC). The new gene-level analysis sharpens the biomarker story: 28.4% of patients had an HRR mutation, most commonly BRCA2 (7.3%), ATM (6.2%), and CDK12 (5.0%). In BRCA2-mutant disease, olaparib + abiraterone produced striking rPFS (HR 0.20; 95% CI 0.08–0.44) and OS (HR 0.20; 95% CI 0.07–0.48) signals, while ATM (rPFS HR 0.55; OS HR 0.79) and CDK12 (rPFS HR 0.51; OS HR 0.57) estimates were less definitive, with confidence intervals crossing 1.0. In the overall biomarker-unselected PROpel population, rPFS favored the combination (HR 0.66), but final median OS was 42.1 vs 34.7 months (HR 0.81; p=0.054), which did not cross the prespecified significance boundary. Importantly, the U.S. approval is specifically for BRCA-mutated mCRPC; FDA’s retrospective analysis found much less convincing efficacy in patients without BRCA mutations, reinforcing that the broad PROpel benefit appears heavily BRCA-driven.