Previously, we reported our experience treating 14 patients with metastatic melanoma using a fully human antibody to cytotoxic T-lymphocyte antigen-4 (anti–CTLA-4) in conjunction with peptide vaccination. We have now treated 56 patients to evaluate two different dose schedules of anti–CTLA-4 and to explore the relationship between autoimmunity and tumor regression.

A total of 56 patients with progressive stage IV melanoma were enrolled onto the study. All had Karnofsky performance status ≥ 60% with no prior history of autoimmunity. Twenty-nine patients received 3 mg/kg anti–CTLA-4 every 3 weeks, whereas 27 received 3 mg/kg as their initial dose with subsequent doses reduced to 1 mg/kg every 3 weeks. In both cohorts patients received concomitant vaccination with two modified HLA-A*0201-restricted peptides from the gp100 melanoma-associated antigen, gp100:209-217(210M) and gp100:280-288(288V).

Two patients achieved a complete response (ongoing at 30 and 31 months, respectively) and five patients achieved a partial response (durations of 4, 6, 25+, 26+, and 34+ months, respectively), for an overall objective response rate of 13%. Tumor regression was seen in lung, liver, brain, lymph nodes, and subcutaneous sites. Of 14 patients with grade 3/4 autoimmune toxicity, five (36%) experienced a clinical response compared with only two responses in the 42 patients (5%) with no autoimmune toxicity (P = .008). There were no significant differences in response rate or toxicity between the two dose schedules.

Administration of anti–CTLA-4 monoclonal antibody plus peptide vaccination can cause durable objective responses, which correlate with the induction of autoimmunity, in patients with metastatic melanoma.