TYROSINE KINASE INHIBITORS
Toceranib phosphate (Palladia—Pfizer Animal Health), a receptor tyrosine kinase inhibitor, has direct antitumor and antiangiogenic
activity. It is the first FDA-approved veterinary cancer therapy and is indicated for treating grade II or III mast cell tumors
in dogs. Side effects include diarrhea, neutropenia, and weight loss.
Masitinib (Kinavet-CA1—AB Science) is another tyrosine kinase inhibitor useful for treating mast cell tumors in dogs that
is currently available in the United States and conditionally approved by the FDA. Masitinib may also be useful in treating
atopic dermatitis. A study looking at this application demonstrated a significant reduction in clinical signs.10
Imiquimod (Aldara 5% cream—3M Pharmaceuticals) is an immune response modifier designed to stimulate a patient's own immune
system to release cytokines. This drug is expensive, which can be an impediment to wider use. While considered an antiviral,
antitumor drug, it does not have a direct antiviral effect. It has been used to treat papilloma and sarcoids in horses with
some success. In small animals, it has been used to treat feline herpesvirus dermatitis, actinic keratosis, and squamous cell
carcinoma. Inform owners that it can produce local irritation, pruritus, and oozing. Imiquimod is applied in very small amounts
once weekly to every other day to the affected area until the lesion resolves.
Interferon alfa-2b (Schering; consult your local distributor) is known to increase cytokine production and is used to treat
viral infections and for immunomodulatory purposes. It can be used to treat canine papillomavirus infection and recurrent
pyodermas in dogs and indolent ulcers, idiopathic facial dermatitis, dermatitis secondary to feline herpesvirus infection,
and atopy in cats. There is a huge dose range for use in dogs (30 to 20,000 IU orally once a day11) and cats (60 to 120 IU/day orally), and it comes highly concentrated (10 million IU/vial), necessitating dilution before
use. It can be diluted and stored (frozen) for several months.
Patrick Hensel, Dr.med.vet., DACVD
Department of Small Animal Medicine & Surgery
College of Veterinary Medicine
University of Georgia
Athens, GA 30602