Interim analysis (IA) results of COU-AA-302, a randomized, phase III study of abiraterone acetate (AA) in chemotherapy-naive patients (pts) with metastatic castration-resistant prostate cancer (mCRPC).

LBA4518 Background: AA is an androgen biosynthesis inhibitor that inhibits CYP17 and improves overall survival (OS) in post-docetaxel mCRPC. The primary objective of COU-AA-302 was to compare clinical benefit of AA + prednisone (P) vs placebo (PL) + P in chemo-naive, asymptomatic/mildly symptomatic mCRPC pts. Methods: 1088 pts (151 centers; 12 countries) were randomized 1:1 to AA (1 g) + P (5 mg BID) or PL + P. Co-primary endpoints: radiographic progression-free survival (rPFS) and OS. Median times estimated using K-M method including LR statistic for inference. The Lan-DeMets α-spending function was used for OS. Results:The Independent Data Monitoring Committee concluded that the OS, rPFS and secondary endpoints (Table) all favored the AA arm and unanimously recommended unblinding the study and crossing pts from PL to AA at IA (43% of total events). Median follow up = 22.2 mos. Grade 3/4 AEs (AA + P, PL + P) (%): hypertension 3.9 vs 3.0; hypokalemia 2.4 vs 1.9; ALT↑ 5.4 vs 0.7; AST↑ 3.0 vs 0.9. Conclusio...