Background: VD is a negative prognostic factor in mCRPC patients (pts) and may be less responsive to hormonal therapy. AA, a selective androgen biosynthesis inhibitor, inhibits androgen synthesis from adrenal and intratumoral sources. Improved overall survival (OS) with AA vs prednisone (P) was demonstrated in a randomized trial of pts with mCRPC post-docetaxel (D). Here we further assess the effect of AA on OS and other clinical outcomes in post-D mCRPC pts with VD (liver or lung, but not nodal-only metastases). Methods: In COU-AA-301, pts with mCRPC previously treated with D were randomized 2:1 to AA (1000 mg) + P (5 mg BID) (n=797) or placebo + P (n=398). The primary end point was OS. Data shown herein represent the updated analysis (775 events) of patients with (n=352) or without (n=843) VD. Results: The OS benefit of AA was similarly improved in patients with VD (4.6 m) and without VD (4.8 m) (Table). Treatment with AA led to significant 40% and 32% reductions in the risk of radiographic progression or death in patients with VD or without VD, respectively. Soft-tissue objective response rates were superior with AA in both groups. PSA response rates (50% reduction) were significantly improved by AA in both groups. Grade 3/4 adverse events (AEs) were similar in both groups. Hypertension, hypokalemia, and LFT abnormalities were observed with AA in pts with and without VD. Conclusions: AA has substantial anti-tumor activity and provides clinical benefit including improvements in OS and rPFS in post-D mCRPC pts with VD indicating it is a therapeutically active treatment option for CRPC pts. Safety/tolerability of AA in pts with VD was similar to that reported previously in mCRPC. Clinical trial information: NCT00638690.