A Phase 2 Trial of Abiraterone Acetate in Japanese Men with Metastatic Castration-resistant Prostate Cancer and without Prior

Objective: Abiraterone acetate has been approved in.70 countries for chemotherapy-naı̈ve metastatic castration-resistant prostate cancer patients. Efficacy and safety of abiraterone acetate (1000 mg/once daily) with prednisolone (5 mg/twice daily) in chemotherapy-naı̈ve Japanese patients with metastatic castration-resistant prostate cancer was evaluated. Methods: Men, 20 years, with prostate-specific antigen levels of 5 ng/ml and evidence of progression were enrolled in this Phase 2, multicenter, open-label study. Primary efficacy end-point was proportion of patients achieving a prostate-specific antigen decline of 50 % from baseline (prostate-specific antigen response) after 12 week of treatment. Secondary efficacy endpoints and safety were assessed. Results: A confirmed prostate-specific antigen response was observed in 29/48 (60.4%) patients by week 12; lower limit of two-sided 90 % confidence interval was.35 % (threshold re-sponse rate), demonstrating efficacy of abiraterone acetate. Secondary efficacy endpoints