Researchers at three veterinary schools are working together to test a new cancer vaccine on dogs in the largest clinical trial ever conducted for canine cancer. And if it works on dogs, it could potentially lead to a vaccine to prevent cancer in humans.

The Vaccination Against Canine Cancer Study (VACCS trial) hopes to enroll 800 healthy, middle-aged pet dogs to test the effectiveness of the new vaccine. In the double-blind study, some dogs will receive the real vaccine, and some a placebo vaccine. The dogs will live at home and be checked 2 to 3 times a year for 5 years after enrollment. If any of the dogs develop cancer during the study, whether on the real vaccine or the placebo, their owners will receive a hospital credit to defray the cost of diagnostics and treatment

Patients who receive the placebo vaccine are expected to develop cancer at normal rates. Cancer is the leading cause of death in dogs, accounting for approximately 30% of all deaths. Certain breeds have much higher likelihoods of cancer than others. Researchers hope the trial will show whether the vaccine can delay or prevent cancer development in the vaccinated group.

Leading the clinical trials is Douglas Thamm, DVM, a professor of oncology at Colorado State University’s  (CSU) veterinary teaching hospital. Researchers at the University of Wisconsin-Madison and the University of California, Davis are sharing the research load with CSU.

Thamm told NEWStat that the new vaccine is unique in several ways: “It’s being used in an attempt to prevent, rather than treat cancer,” Thamm said. “It has the potential to target multiple tumor types simultaneously, rather than a single tumor type. [And] it targets neoantigens, or novel proteins, that occur in the RNA rather than in the DNA.”

In laboratory experiments on mice, the vaccine delayed or prevented multiple types of cancer without side effects.

This is significant because for decades, many scientists believed that a universal, preventive cancer vaccine wasn’t possible because all cancers are unique. That belief was challenged when researchers at Arizona State University were able to identify commonalities among different cancerous tumors and used the information to develop what they believe is a potential universal preventive cancer vaccine.

Called a multivalent frameshift peptide vaccine, it’s been shown to be safe for use in companion animals. But if it shows such promise, why not go directly to clinical trials on people?

“Making a jump from showing efficacy in mice right to a big study in humans is very daunting, owing to the expense and time required for an appropriate human study,” Thamm said. “We think that, given the high incidence of cancer in dogs and their significantly shortened life span, we can answer a question about efficacy in 5 years rather than the 15-20 years it might take in people.  Dogs get cancer that is very similar to human cancer, and importantly, both dogs and humans share these RNA-derived neoantigens.”

Thamm said if the study is successful, a commercially available cancer vaccine for dogs could conceivably be available with a couple of years of the study’s conclusion, although a second clinical trial in dogs would need to be done, first.

 “The current vaccine we’re using is a bit complicated and a little harder than a typical vaccine to produce and administer,” Thamm said, and the researchers would like to develop a simpler version of the vaccine for dogs. “If a similar immune response developed in dogs receiving this simplified vaccine, it’s likely that this would make a better product.”

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