An investigational vaccine for melanoma has shown promise in a clinical trial conducted with 9 dogs that had advanced disease, according to an article in the April issue of Clinical Cancer Research. The DNA-based vaccine was developed and underwent preclinical testing at Memorial Sloane-Kettering Cancer Center and had its first clinical trial at the nearby Animal Medical Center.

Median survival for the 9 dogs more than tripled with the vaccine treatment: It increased from the expected 90 days to an average of 389 days. A clinical trial has begun at the cancer center for people at high risk for recurrence of their melanoma.

"Most medicines that we use to treat animals are the same as those given to humans," explained Philip J. Bergman DVM, MS, PhD, lead author of the study. "This vaccine was first tested in the laboratory [at Memorial Sloane-Kettering] and then given to dogs with melanoma after receiving approval from the United States Department of Agriculture and the Animal Medical Center’s own Institutional Review Board. We felt it was useful to see if immunotherapy might help these very sick dogs with advanced melanoma since the response rates for standard chemotherapy were extremely poor with no evidence of improved survival."

In the current study, 9 dogs with advanced melanoma were given 4 bi-weekly injections of human tyrosinase DNA vaccine that was constructed at the cancer center’s Gene Transfer and Somatic Cell Engineering Facility. The dogs were injected with the vaccine using the Biojector-2000, a needle-less delivery device. They showed no significant side effects or toxicity, only a mild inflammatory reaction observed at the injection site.

After completion of the vaccine regimen, 2 dogs showed no evidence of disease; 4 of the dogs survived more than 400 days, with the longest survivor still alive after 615 days.

"Like humans, dogs develop melanoma spontaneously through an interaction of their genes with the environment," said Jedd D. Wolchok, MD, PhD, of the Clinical Immunology Service at Memorial Sloan-Kettering and senior author of the study. "By conducting trials in humans and large animals that live in the same surroundings as humans and spontaneously develop cancers, there can be a synergy that we hope will result in improved cancer treatment for all."