* Palladia approved for canine mast cell tumors
* Pfizer to begin selling drug in early 2010
* First cancer treatment specifically designed for dogs (Adds therapy details, no comment on price)
By Bill Berkrot
NEW YORK, June 3 (Reuters) - Pfizer Inc's (PFE.N) efforts to develop new cancer drugs have yielded a breakthrough -- for dogs.
The U.S. Food and Drug Administration has approved the first cancer treatment specifically designed to treat dogs, Pfizer and the agency announced on Wednesday.
The drug Palladia was approved to treat canine mast cell tumors, a potentially serious type of cancer that accounts for about 20 percent of canine skin tumors, and one that can spread to other parts of the body, including lymph nodes, if not treated.
All cancer drugs now used in veterinary medicine originally were developed for use in humans and are not specifically approved for use in animals, the FDA said.
"This cancer drug approval for dogs is an important step forward for veterinary medicine," Bernadette Dunham, director of FDA's Center for Veterinary Medicine, said in a statement.
"Prior to this approval, veterinarians had to rely on human oncology drugs without knowledge of how safe or effective they would be for dogs," she said.
Pfizer said it would begin selling Palladia in early 2010, but will make the oral drug available to certain veterinary oncology specialists prior to that.
Palladia works by killing tumor cells and by cutting off the blood supply to the tumor.
The pill must be taken every other day and the dog will likely have to be on the therapy for several months or longer, depending on tumor response, Pfizer said.
Pfizer declined to divulge the cost of the treatment or to forecast what annual Palladia sales might be. The world's biggest drugmaker said it will likely announce the price of the drug sometime this summer.
Treatment with new cancer drugs for humans tends to cost tens of thousands of dollars per patient, and the majority of pet owners do not have health insurance for their dogs.
In clinical trials, some 60 percent of dogs treated with Palladia, known chemically as toceranib, had their tumors disappear, shrink or stop growing, Pfizer said.
Pfizer Animal Health estimates 1.2 million new canine cancer cases are reported in the United States every year.
Pfizer shares fell 14 cents, or 0.9 percent, to $14.84 in afternoon trading on the New York Stock Exchange. (Reporting by Bill Berkrot, editing by Matthew Lewis, Richard Chang)