8524 Background: The fully human anti-CTLA4 mAb CP-675,206 has demonstrated clinical activity in pts with metastatic melanoma. Prolonged survival was observed in a prior single-dose phase I study, even in pts who did not achieve objective tumor responses. Methods: A multidose phase I/II trial was conducted in pts (N = 119) with histologically confirmed stage IIIc (unresectable) or stage IV recurrent metastatic melanoma and ECOG PS = 1. The study consisted of a phase I, open-label, multidose study (3, 6, and 10 mg/kg) and a phase I expansion cohort for HLA-A2.1+ pts (10 mg/kg monthly [Q1M]), followed by a phase II open-label study of 2 dosing regimens: 10 mg/kg Q1M and 15 mg/kg every 3 months (Q3M). The primary endpoint was safety in phase I, immune monitoring in the expansion cohort, and response in phase II. Survival was analyzed as a secondary endpoint. Results: In the phase I study, Kaplan-Meier estimates of median overall survival were 17.6 months for all dose groups combined (n = 28). In the phase II...