CCR Perspectives in Drug Approval Abiraterone Acetate in Combination with Prednisone for the Treatment of Patients with Metastatic Castration-Resistant Prostate Cancer: U.S. Food and Drug Administration Drug Approval Summary

On December 10, 2012, the U.S. Food and Drug Administration granted full approval for a modified indication for abiraterone acetate (Zytiga tablets; Janssen Biotech, Inc.) in combinationwith prednisone for the treatment of patients with metastatic castration-resistant prostate cancer (mCRPC). The approval was based on clinical trial COU-AA-302, which randomly allocated asymptomatic or mildly symptomatic patients with chemotherapy-na€ ve mCRPC and no visceral metastases to either abiraterone acetate plus prednisone (N1⁄4 546) or placebo plus prednisone (N1⁄4 542). The coprimary endpoints were radiographic progression-free survival (rPFS) and overall survival (OS). The median rPFS was 8.3 months in the placebo arm and had not yet been reached in the abiraterone acetate arm {HR, 0.43 [95% confidence interval (CI) 0.35–0.52]; P < 0.0001}. A prespecified interim analysis demonstrated an improvement in OS favoring the abiraterone acetate arm [HR, 0.79 (95%CI, 0.66–0.96)] but did not cross theO’Brien-Fleming boundary for statistical significance. Safety data confirmed the known adverse reaction profile of abiraterone acetate. Full approvalwas grantedon the basis of a largemagnitudeof effect on rPFS, a favorable trend inOS, and internal consistency acrossmultiple secondary endpoints and exploratory patient-reported pain data. This is the first drug approval formCRPC to use rPFS as the primary endpoint. Importantly, this approvalwas granted in the context of a prior statistically significant OS benefit that formed the basis of the original April 28, 2011, approval of abiraterone acetate for patients with mCRPC who had received prior chemotherapy containing docetaxel. Clin Cancer Res; 19(24); 6650–6. 2013 AACR.