TYROSINE KINASE INHIBITORS

Toceranib phosphate

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

ANTIVIRAL DRUGS

Imiquimod

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

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