The first therapeutic vaccine for the treatment of cancer in either humans or animals has just been approved by the USDA. The vaccine, produced by Merial, is indicated for the treatment of certain types of melanoma in the oral cavity of dogs.
In the dog, oral melanoma is often a malignant and aggressive type of cancer that can be difficult to treat. Dogs that develop malignant oral melanoma often have a life expectancy of less than six months, even following local removal and control of the tumor through surgery and/or radiation therapy. The dogs that received the therapeutic vaccine treatment showed increased survival time; according to one of the published studies, patients with advanced disease achieved a median survival time of 389 days.
Dr. J. Wolchok of the Memorial Sloan-Kettering Cancer Center in New York collaborated with Dr. Philip Bergman at the Animal Medical Center in New York to lay the initial groundwork for the development of the vaccine. Once the vaccine was developed, Dr. Bergman approached Merial for support, and the vaccine was further developed and refined. The actual vaccine is a plasmid DNA-based vaccine, and is directed against the melanoma tumor protein tyrosinase, using a gene that codes for human tyrosinase. The human tyrosinase is different enough from canine tyrosinase that it stimulates an immune response in the dog, yet similar enough to the canine tyrosinase that the immune response is directed against the canine melanoma cells.
Currently, the vaccine has only been tested and given conditional approval for use as a therapeutic vaccine. The approved protocol involves administration of a dose of the vaccine every two weeks for four treatments, followed by a booster dose every six months. Since the vaccine only has conditional approval from the USDA, Merial is limiting its use to veterinary oncologists in the United States during the conditional time period. The company anticipates that it will be available to a broader market over time.
Canine oral melanoma strikes only a small population of dogs, and at this time, it is difficult to predict which dogs it will target. Therefore, the use of this vaccine as a preventative treatment may be limited until further research has been conducted. However, Merial is continuing to work with the Memorial Sloan-Kettering Cancer Center and the Animal Medical Center to target other cancers for ongoing research.
