Experimental vaccine offers promise for canine melanoma

MADISON, WIS. — Some dogs, albeit few, experience total remission following an experimental melanoma vaccine therapy.

Oncologists' demand for the therapy for oral and digital melanoma has prompted the University of Wisconsin-Madison School of Veterinary Medicine to add a technician to help produce it.

About 30 patients each year since 1999 have been treated by administering irradiated lines of melanoma that have "all the markers for melanoma that we were able to identify on the cells' surface," says Ilene Kurzman, EdD, a researcher at the veterinary school's oncology section. "It's gone through a few different modifications, mostly in how we make or prepare the vaccine so that we can do it more efficiently and get better incorporation of the DNA that we are putting in and also streamline it so we can increase our production."

Kurzman ships the vaccine throughout the country to oncologists, who then help measure the results. The most success has been with oral tumors.

"In dogs that have measurable tumors (24 total) 40 percent have had some type of response, and 10 of the 24 have been stable anywhere from two to 26 months," she says. "What's exciting for us is that three of those dogs had complete responses, meaning that the tumor disappeared and didn't come back. So that's what keeps them going."

Other results for digital melanoma include prolonging the life of the patient and disease-free survival days that outnumber other modalities.

"This is a viable option given that melanoma is not very responsive to chemotherapy or radiation therapy given that we are getting about the same efficacy that has been reported with chemotherapy, but there are no side effects. So this is a very viable therapeutic option," Kurzman says. "Now, we're hoping to move it forward to the next phase."

The center is currently using two different types of vaccines that produce similar results, but researchers have expansion plans.

"The dogs are being injected with live melanoma cells; these live cells have had DNA inserted into them and the DNA, in one of the lines, produces a growth factor that stimulates the immune system to attack melanoma cells," Kurzman explains. "The other vaccine is a human DNA that causes a cell surface marker that is normally present on melanoma cancer cells in humans and in dogs to over-express. So it gives a signal to the immune system to come and attack the tumor cells."

The two vaccines separately show promise, but it's not panacea, Kurzman says. The goal is to combine the two vaccines to boost efficacy. The donation-based operation (asking less than $2,000 per patient) currently is courting funding from the Morris Animal Foundation to develop the vaccine further.

"We are going to continue this trial because the demand is so great, and we are able to collect a lot of great information. And the more information we have, the better we can design the next trial. But our goal is to move forward with this double vaccine," she says. "We've seen similar efficacy from the two different vaccines, now we want to see that if we put them together if we are going to get increased efficacy. That's our hope."