"This is the first time we have evaluated peptide-derived melanoma vaccine results from a multicenter cooperative group trial," said John Kirkwood, M.D., principal investigator of the study, and professor of medicine at the University of Pittsburgh and director of the Melanoma Center at the University of Pittsburgh Cancer Institute (UPCI). "While these results are preliminary, we have found evidence that the vaccine stimulates an immune response and that there is a resultant benefit for patients who receive the vaccine."
The phase II study evaluated a multiepitope CD8 T-cell vaccine comprised of three peptides derived from tumor-associated antigens of melanoma. The vaccine was evaluated alone, in combination with granulocyte macrophage-colony stimulating factor (GM-CSF), in combination with interferon and in combination with both GM-CSF and interferon.
The study included 120 patients with metastatic melanoma. Immune response data was evaluated for the first 60 patients. Final analysis of the data will take several more months to be evaluated.
Patients received the vaccine by injection once every two weeks for 12 weeks. Immune response was induced in 32 percent of the patients and response to vaccination correlated significantly with non-progression of disease and longer survival.
The study found that disease progressed in only 37 percent of those patients who had an immune response to the vaccine, compared to disease progression in 60 percent of those patients who did not have any evidence of immune response to the vaccination. Disease remained stable in 56 percent of the patients who had an immune response to the vaccine, compared to 28 percent who did not have evidence of an immune response. There were objective responses in several patients treated with the triple peptide vaccine, including one complete and two partial responses, but these did not appear to correlate with ELISPOT assays for immune response.
According to Dr. Kirkwood, the vaccine was fairly well tolerated by most patients with typical side effects that included vaccine site discomfort and expected toxicity to interferon and GM-CSF.
Malignant melanoma is one of the deadliest forms of skin cancer. An estimated 54,200 new cases of melanoma are expected in 2003 and 7,600 deaths are expected to occur.
The study includes more than 30 institutions across the country and is funded by a grant from the National Institutes of Health and awards to ECOG from the Schering Plough and Immunex Corporations.