Food Effect Study of Abiraterone Acetate for Treatment of Patients With Castration-Resistant Prostate Cancer

PRIMARY OBJECTIVES: I. To compare the pharmacodynamic effect of reduced dose (250mg daily) abiraterone acetate in the prandial state (250mg-Fed) to the full, standard 1000mg daily dose in the fasting state (1000mg-Fasting) as assessed by change in serum prostate-specific antigen (PSA). SECONDARY OBJECTIVES: I. To evaluate the effect of prandial states on plasma levels and the intra-patient pharmacokinetic variability of abiraterone acetate. II. To evaluate the safety profile of reduced dose abiraterone acetate taken in the prandial state. III. To evaluate the pharmacodynamic effect of reduced dose abiraterone acetate in the prandial state as assessed by reduction in the extra-gonadal androgen dihydroepiadrosterone sulfate (DHEA-S) and dihydroepiandrostenedione (DHEA). IV. To evaluate the effect of prandial state on time to disease progression (Working group criteria). OUTLINE: Patients are randomized to one of two treatment arms. ARM I: Patients receive abiraterone acetate orally (PO) daily first thing in morning after an overnight fast of at least 8 hours. ARM II: Patients receive abiraterone acetate PO daily within 30 minutes of a conventional low-fat breakfast. In both arms, courses repeat every 28 days in the absence of disease progression or unacceptable toxicity. Both arms will also be treated with prednisone 5mg twice daily. After completion of study treatment, patients are followed up within 30 days.