Abstract
PURPOSE: This multicenter randomized trial was designed to evaluate whether melanoma helper peptides augment cytotoxic T lymphocyte (CTL) responses to a melanoma vaccine and improve clinical outcome in patients with advanced melanoma. EXPERIMENTAL DESIGN: One hundred seventy-five patients with measurable stage IV melanoma were enrolled into 4 treatment groups, vaccinated with 12 MHC class I-restricted melanoma peptides to stimulate CTL (12 MP, group A), plus a tetanus peptide (group B), or a mixture of 6 melanoma helper peptides (6 MHP, group C) to stimulate helper T lymphocytes (HTL), or with 6 melanoma helper peptide (6 MHP) alone (group D), in incomplete Freund's adjuvant plus granulocyte macrophage colony-stimulating factor. CTL responses were assessed using an in vitro-stimulated IFN-γ ELIspot assay, and HTL responses were assessed using a proliferation assay. RESULTS: In groups A to D, respectively, CTL response rates to 12 melanoma peptides were 43%, 47%, 28%, and 5%, and HTL response rates to 6 MHP were in 3%, 0%, 40%, and 41%. Best clinical response was partial response in 7 of 148 evaluable patients (4.7%) without significant difference among study arms. Median overall survival (OS) was 11.8 months. Immune response to 6 MHP was significantly associated with both clinical response (P = 0.036) and OS (P = 0.004). CONCLUSION: Each vaccine regimen was immunogenic, but MHPs did not augment CTL responses to 12 melanoma peptides. The association of survival and immune response to 6 MHP supports further investigation of helper peptide vaccines. For patients with advanced melanoma, multipeptide vaccines should be studied in combination with other potentially synergistic active therapies.