8512 Background: Ipilimumab (IPI), a fully human monoclonal antibody, blocks cytotoxic T-lymphocyte antigen-4 to potentiate an antitumor T-cell response. In a phase 3 study (CA184-024) of previously untreated pts with stage III or IV melanoma, IPI + dacarbazine (DTIC) significantly improved overall survival (OS) vs. DTIC alone (Robert et al. NEJM 2011). We now report safety data of IPI in pts from this study alive > 2 yrs from study initiation. Methods: Pts with untreated advanced melanoma, were randomized to IPI (10 mg/kg) + DTIC (850 mg/m2) or placebo + DTIC (850 mg/m2) given at Wks 1, 4, 7, 10 followed by DTIC q 3 wks through Wk 22. Eligible pts (stable disease or better) received IPI or placebo q 12 wks as maintenance. In the population of subjects alive >2 yrs, the appearance of immune-related adverse events (irAEs) occurring after 2 yrs was evaluated. Within this group was a subset of subjects still receiving IPI dosing after 2 yrs; safety for these pts was evaluated to assess the impact of prolonged IPI exposure. Results: In the IPI + DTIC group 68 (28%) pts survived > 2 yrs compared to 44 (18%) in the DTIC alone group; 11 of the 68 continued IPI dosing for ≥ 2 yrs. Safety assessment beyond 2 yrs showed 3 of the 11 pts had any grade irAEs; 1 pt had grade 3/4 rash, pruritus while low grade events included rash, pruritus (n=2) and elevated ALT / AST (n=1). Overall among all 68 pts in the Ipi + DTIC group, there were 5 pts (7.4%) with any grade irAEs including grade 3/4 rash, pruritus (n=1) and low grade rash (n=3), pruritus (n=2), skin hypopigmentation, and elevated ALT / AST (n=1). No gastrointestinal or endocrine events (any grade) were observed. Conclusions: In Study 024, IPI + DTIC treatment improved OS pts with untreated, advanced melanoma with higher survival rates in the IPI + DTIC group at 1 yr (47.3% vs. 36.3%), 2 yrs (28.5% vs. 17.9%), and 3 yrs (20.8% vs. 12.2%) (HR 0.72, p<0.001). The safety profile of pts alive after 2 yrs suggests that treatment with IPI + DTIC is associated with low rates of irAEs in these pts. Furthermore, in pts still receiving active IPI treatment beyond ≥ 2 yrs, the safety profile appears to be consistent and medically manageable using established safety guidelines (Weber, Oncologist 2007).