Animal & Veterinary

Kinavet-CA1 (mastinib mesylate)

December 15, 2015

Dear Veterinarian:

The U.S. Food and Drug Administration (FDA) wants to inform you that the conditional approval for Kinavet-CA1 (mastinib mesylate) terminated as of December 15, 2015. The drug, marketed by AB Science, was conditionally approved on December 15, 2010, to treat mast cell tumors in dogs. Now that the conditional approval is no longer in effect, Kinavet-CA1 is an unapproved animal drug with no legal marketing status. You will no longer be able to legally obtain the drug.

To receive a conditional approval, a drug company must prove, among other things, that the animal drug is safe and has “a reasonable expectation of effectiveness” when used according to the label for the conditionally-approved use. Conditional approval allows the drug company to legally sell the animal drug for up to five years. During this period, the company develops and submits to the FDA—and the agency reviews—the necessary data to prove that the drug meets the “substantial evidence” standard of effectiveness for full approval.

Conditional approval does not always lead to full approval. Under the Federal Food, Drug, and Cosmetic Act, a conditional approval is no longer in effect if the FDA does not approve the drug before the conditional approval period terminates. The conditional approval period for Kinavet-CA1 terminated today—five years after the drug’s initial conditional approval date. The FDA did not approve Kinavet-CA1 by December 15, 2015, and therefore, the drug’s conditional approval is no longer in effect as of that date.

AB Science must cease marketing Kinavet-CA1 and distributors must cease distributing the drug to veterinary clinics. You should contact AB Science about what to do with remaining Kinavet-CA1 stock in your inventory.

For dogs currently on Kinavet-CA1, you may want to consider other available approved treatments. For example, the drug Palladia (toceranib phosphate, NADA 141-295), which is FDA-approved for the treatment of mast cell tumors in dogs, may be appropriate in some cases. Also, other FDA-approved animal and human drugs may potentially be used legally in an extralabel manner in dogs with mast cell tumors.

The FDA’s Center for Veterinary Medicine (CVM) is committed to promoting and protecting animal health by ensuring safe and effective drugs are available for animals. For more information, please contact the CVM Education & Outreach Staff at 240-402-7002 or


FDA’s Center for Veterinary Medicine

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