16043 Background: Antiapoptotic Bcl-2 family proteins are overexpressed in HRPC and contribute to resistance to therapy. The oral pan-Bcl-2 inhibitor AT-101 (Bcl-2, Bcl-XL, Bcl-W, Mcl-1) is active as a single agent and in combination in in vitro and in vivo tumor models and as a single agent in HRPC. The Phase 1 portion of the study determined the recommended dose for Phase 2 was D (75mg/m2 q 3 weeks) in combination with P (5mg/BID on days 1–21), and AT-101 at 40mg/BID on days 1–3 of each cycle, and was previously reported. Methods: Men ≥18 years of age with HRPC were eligible. Two cohorts of subjects were treated; Cohort A consists of men with chemotherapy-naive HRPC (N=12) and Cohort B consists of men who received and progressed during treatment with a D regimen (N=1). Safety (NCI CTCAE v. 3.0) and efficacy (Bubley Criteria for PSA) were assessed at 3-wk intervals. Radiological assessments were performed at 6-wk intervals. Results: 25 of 65 planned subjects have been enrolled in the study, of which 13 P...