1st Canine Cancer Drug OKd

By Marissa Heflin, Senior News Editor
Veterinary Practice News, July, 2009
www.VeterinaryPracticeNews.com

Pfizer Animal Health of New York had reason to celebrate during the American College of Veterinary Internal Medicine Forum.
The company’s Palladia (toceranib phosphate) became the first drug approved by the U.S. Food and Drug Administration specifically for the treatment of cancer in dogs.  Pfizer made the announcement in June during the Forum in Montreal.

The prescription tablet, under development for about 10 years, is approved to treat canine cutaneous mast cell cancer, which is responsible for about one in five cases of canine skin tumors.

All cancer drugs now used in veterinary medicine were developed for use in humans and are used off-label in animals. “What we wanted to do was provide something that specifically had safety and efficacy information just for dogs,” said Amy Trettien, DVM, of Pfizer’s veterinary operations. “Pfizer Corporate has picked oncology as one of the areas of excellence that they want to pursue,” Dr. Trettien said.  “If you look at the Morris Animal Foundation statistics, about half the dogs over the age of 10 die of cancer.  One in two dogs will get cancer in their life and one in four dogs will die of cancer.” Palladia is an oral therapy indicated to treat Patnaik grade II or III recurrent cutaneous mast cell tumors with or without regional lymph node involvement. The drug belongs to the tyrosine kinase inhibitor class of compounds and blocks the activity of key receptors important for the development of blood vessels that supply tumors, as well as receptors critical for tumor survival, according to the company.

The clinical study, published in Clinical Cancer Research, comprised a six-week masked phase followed by the open-label phase, and evaluated the safety and effectiveness of Palladia in 151 client-owned dogs. 

In the blinded phase, the dogs were randomized to receive Palladia 3.25 mg/kg or a placebo every other day for six weeks.
Thereafter, 145 eligible dogs received open-label Palladia and were treated for about six months.  “From that study, we found that the drug did work and that it was manageable in terms of safety,” Trettien said.

Tumors disappeared, shrank or stopped growing in 60 percent of the dogs at the completion of the study, said Cheryl London, DVM, Ph.D., Dipl. ACVIM (oncology), an associate professor at Ohio State University’s College of Veterinary Medicine.  Dr. London has helped the company develop the drug since 2000.
Dogs whose tumors responded to Palladia experienced an improved quality of life, London said. 
Trettien said quality of life is one of the most important things veterinary medicine can offer.
“If a dog’s tumor does better but the dog is horribly sick, that’s certainly not a very good alternative,” she said.  “But if we can offer a drug where the dog does respond and feels good during that time, I think that’s the really important thing.”

The most common side effects with Palladia involve the gastrointestinal tract.  Signs include diarrhea, decreased appetite, lethargy and vomiting.
Pfizer Animal Health is working with veterinary oncologists, internists and dermatologists to see how the drug works in multimodal protocol.  In human medicine, combination treatments frequently generate a better response than any one drug used alone, Trettien noted.

“{The company has proved to the FDA} that this drug works all on its own, that it has efficacy by itself,” she said.  “That is what the clinical trial was for.”  “Now, through the end of the year, we want to work with specialists who are used to managing normal chemotherapy protocols and say, ‘OK, where does Palladia fit in?  What does it look like if you add it or put it after other chemotherapeutics?  Does it change the safety?  Is there anything particular we need to know?’ “. 
The answers will help the company support veterinarians when the product goes on sale in 2010, she says. 
Pfizer continues to look for new therapeutics.

“Our goal is to being innovation, cutting-edge medications to veterinarians with data to support the use in dogs and cats and the animals they see, rather than have to take drugs that are available on the human side and try to figure out what the safe and efficacious dose is,” Trettien said.