Pharmacokinetic (PK) subgroup results from the phase 2 pharmacodynamic and bioequivalence study of abiraterone acetate fine particle formulation (AAFP) in patients with metastatic castration-resistant prostate cancer (mCRPC): The STAAR study.

176Background: AAFP, a novel formulation, showed therapeutic equivalence to originator abiraterone acetate (OAA) in the Phase 2 STAAR study (Stein et al. Urologic Oncol). A patient-subgroup analysis compared steady-state PK parameters between AAFP and OAA. Methods: This multicenter, open-label, active-controlled study enrolled men with progressive mCRPC treated 1:1 with 500 mg AAFP tablets QD + 4 mg methylprednisolone BID, or 1000 mg OAA tablets QD + 5 mg prednisone BID for 9 days. Study drug was taken 2 hours post morning meal. On day 9, plasma abiraterone blood samples were collected at predose, 0.25, 0.5, 1, 2, 4, 6, 8, 10, and 24 hr time points. Results: PK samples were evaluable for 13 of 14 patients (n=5, AAFP; n=8, OAA). Mean age was 67.4 and 73.3 years, respectively. Twelve patients completed the 12-week study without clinical disease progression. One OAA patient died from MI in week 4. PK parameters (AUC, Cmax, Cmin), were numerically lower but not statistically significantly different for those ...