Three phase II cytokine working group trials of gp100 (210M) peptide plus high-dose interleukin-2 in patients with HLA-A2-positive advanced melanoma

Purpose: High-dose interleukin-2 (IL-2) induces responses in 15% to 20% of patients with advanced melanoma; 5% to 8% are durable complete responses (CRs). The HLA-A2-restricted, modified gp100 peptide (210M) induces T-cell immunity in vivo and has little antitumor activity but, combined with high-dose IL-2, reportedly has a 42% (13 of 31 patients) response rate (RR). We evaluated 210M with one of three different IL-2 schedules to determine whether a basis exists for a phase III trial. Patients and Methods: In three separate phase II trials, patients with melanoma received 210M subcutaneously during weeks 1, 4, 7, and 10 and standard high-dose IL-2 during weeks 1 and 3 (trial 1), weeks 7 and 9 (trial 2), or weeks 1, 4, 7, and 10 (trial 3). Immune assays were performed on peripheral-blood mononuclear cells collected before and after treatment. Results: From 1998 to 2003, 131 patients with HLA-A2-positive were enrolled. With 60-month median follow-up time, the overall RR for 121 assessable patients was 16.5% (95% CI, 10% to 26%); the RRs were 23.8% in trial 1 (42 patients), 12.5% in trial 2 (40 patients), and 12.8% in trial 3 (39 patients). There were 11 CRs (9%) and nine partial responses (7%), with 11 patients (9%) progression free at ≥ 30 months. Immune studies including assays of CD3-ζ expression and numbers of CD4⁺/CD25⁺/FoxP3⁺ regulatory T cells, CD15⁺/CD11b⁺/CD14^- immature myeloid-derived cells, and CD8⁺gp100 tetramer-positive cells in the blood did not correlate with clinical benefit. Conclusion: The results again demonstrate efficacy of high-dose IL-2 in advanced melanoma but did not demonstrate the promising clinical activity reported with vaccine and high-dose IL-2 in any of three phase II trials.