Pharmacokinetics of abiraterone in healthy Japanese men: dose-proportionality and effect of food timing.

PURPOSE: Abiraterone acetate (AA) was recently approved for castration-resistant prostate cancer in Japan. Two phase 1 studies were conducted to assess the pharmacokinetics of abiraterone after single-dose administration in Japanese healthy men and to evaluate the effects of food timing on abiraterone pharmacokinetics after single-dose administration of AA in Japanese and Caucasian healthy men. METHODS: In the dose-proportionality study, subjects (n = 30 Japanese) were randomly assigned to receive single doses of 250, 500, and 1,000 mg AA, and in the food-timing study, subjects (n = 22 Japanese and n = 23 Caucasian) randomly received single doses of 1,000 mg AA under fasted (overnight) and three different modified fasting conditions. RESULTS: Mean C(max) and AUC(∞) for abiraterone increased dose-dependently in Japanese healthy men; however, 90 % confidential interval (CI) was outside the predefined dose-proportionality criteria. Based on geometric mean ratios and 90 % CIs (versus overnight fasting condition), abiraterone exposure (AUC) increased significantly with dosing 1 h premeal, 2 h postmeal, or in between two meals 4 h apart by 57 %, 595 %, and 649 %, respectively. CONCLUSION: No clinically meaningful difference was observed in the pharmacokinetics of abiraterone between Caucasian and Japanese subjects.