What You Should Know About Merial’s Melanoma Vaccine
Posted on October 1, 2009
In 2007, the USDA issued a conditional U.S. Veterinary Biological Product License for Merial’s canine melanoma vaccine. This is the first time the U.S. government has approved the use of a vaccine for the treatment of cancer (in animals or people). The research and production of the vaccine has been through a collaboration between The Animal Medical Center in New York City, Memorial Sloan Kettering Cancer Center, and Merial.
How does the vaccine work? The melanoma vaccine is not a prophylactic vaccine to prevent development of the disease as we would normally think for traditional vaccines for infectious diseases. Instead, it is used as a mode of therapy after diagnosis of malignant melanoma and meant to be used in conjunction with other modes of therapy like surgery and radiation. The vaccine is made from a non-canine tyrosinase gene that is inserted into a plasmid vector. The vaccine is then injected into the patient via a Bioject transdermal injector. Tyrosinase is an enzyme found in melanoma and pigmented cells. In theory, the dog’s immune system is supposed to mount a response to the non-canine, foreign tyrosinase. Because tyrosinase across various species is similar to each other, cross-reactivity of the immune response occurs with the melanoma’s tyrosinase in the dog. This would allow the dog’s immune response to target the melanoma cells[1].
So far, the few studies that have been published on the melanoma vaccine have shown increased survivals for dogs with advanced disease that received the vaccine when compared to historical controls. Older studies with traditional treatments with surgery, radiation, and chemotherapy have been associated with survival times of about 6 months for dogs with advanced disease. Survival times with vaccine therapy incorporated into the treatment regimen have been over a year for those with advanced disease[2]. The problem with comparing new treatment modalities with older, historical controls is the possibility of introducing bias to either of the two groups, raising the question of whether or not the comparison is appropriate.
The melanoma vaccine is currently available through veterinary oncologists while it is under conditional licensure. See this month’s PowerPage for more on canine malignant melanoma.
[1] Bergman PJ, et al. Development of a xenogeneic DNA vaccine program for canine malignant melanoma at the Animal Medical Center. Vaccine 2006;24:4582-4585.
[2] Bergman PJ, et al. Long-Term Survival of Dogs with Advanced Malignant Melanoma after DNA Vaccination with Xenogeneic Human Tyrosinase: A Phase I Trial. Clinical Cancer Research 2003;9:1284-1290.
