Re-induction with ipilimumab, gp100 peptide vaccine, or a combination of both from a phase III, randomized, double-blind, multicenter study of previously treated patients with unresectable stage III or IV melanoma.

8509 Background: Ipilimumab, a fully human monoclonal antibody against cytotoxic T-lymphocyte antigen-4, has demonstrated clinical activity against advanced melanoma. In prior studies, gp100 vaccine showed immunological and clinical responses, and enhanced clinical activity when combined with other immunotherapy. Safety and efficacy of ipilimumab, ipilimumab + gp100 vaccine, and gp100 vaccine were evaluated in this study. Methods: Eligible patients were randomized 1:3:1, respectively, to receive an induction course of 4 doses of study drug: ipilimumab (3 mg/kg q3w × 4 doses) + placebo; ipilimumab + gp100 (peptides 209-217 210M and 280-288 288V); or gp100 (1 mg q3w × 4 doses) + placebo. Re-induction was allowed within 28 days of documented progression, provided the response to the initial cycle of therapy was SD lasting ≥3 months from week 12, CR, or PR. Patients were re-induced with 1 to 3 additional courses of the originally assigned regimen. Results: Of 643 patients initially treated, 32 were re-induced per protocol (8 with ipilimumab, 23 with combination therapy and 1 with gp100 6.1%, 7.3%, and 0.8%, respectively, of the total who received initial therapy with each) and their responses reassessed. Efficacy results are presented below. An acceptable safety profile was demonstrated in all 3 treatment arms and was similar to that of the initial induction treatment. Conclusions: In patients who progressed following an initial response to the induction course of therapy, the disease control rate in the ipilimumab arms was 65%-75% compared to 0% in the gp100 arm upon re-induction. These findings may have implications for the use of ipilimumab therapy in the long-term management of advanced melanoma. Induction, n Best overall response Ipilimumab + gp100 (n = 23*) Ipilimumab (n = 8) gp100 (n = 1) Total (n = 32) CR 0 0 0 0 PR 7 2 1 10 SD 15 6 0 21 Unknown 1 0 0 1 Re-induction, n (%) CR 0 1 (12.5) 0 1 (3.1) PR 4 (17.4) 2 (25.0) 0 6 (18.8) SD 11 (47.8) 3 (37.5) 0 14 (43.8) PD 8 (34.8) 2 (25.0) 1 (100.0) 11 (34.4) Unknown 0 0 0 0 * 5 additional pts were re-induced in error and are not part of the analysis. Author Disclosure Employment or Leadership Position Consultant or Advisory Role Stock Ownership Honoraria Research Funding Expert Testimony Other Remuneration Bristol-Myers Squibb, Medarex Bristol-Myers Squibb Bristol-Myers Squibb, Medarex Bristol-Myers Squibb Bristol-Myers Squibb, Medarex