FDA Approves New Treatment for Allergic Skin Conditions in Dogs

Today, the U.S. Food and Drug Administration approved Zenrelia (ilunocitinib tablets), a new animal drug used to control pruritus (itching) associated with allergic dermatitis and to control atopic dermatitis (environmental allergies) in dogs at least 1 year of age. 

Zenrelia is an immunosuppressant that is administered orally, once daily, with or without food. The active ingredient, ilunocitinib, is a non-selective Janus kinase (JAK) inhibitor and is the second JAK inhibitor the FDA has approved for this indication.

Zenrelia is safe and effective when used according to the label. However, the product labeling carries a boxed warning stating that dogs should not be vaccinated at least 28 days before and after treatment with Zenrelia, due to the risk of fatal vaccine-induced disease and inadequate immune response to vaccines.

In a vaccine response study where dogs received both vaccinations and Zenrelia, treated dogs experienced drug-induced suppression of the immune system, which resulted in fatal vaccine-induced adenoviral hepatitis (liver inflammation) and pancreatitis (inflammation of the pancreas) in one dog; and infectious enteritis (inflammation of the intestines) in one dog. 

Additionally, because Zenrelia works in part by suppressing the immune system, treated dogs who receive vaccines at the same time may not mount an adequate immune response to the vaccine. In the study, four (of six) treated dogs failed to mount an adequate immune response to the rabies vaccine and one dog failed to mount an adequate response to the canine distemper vaccine. This is especially problematic for the rabies vaccine, because rabies is an almost always fatal zoonotic (can infect animal species and people) disease. These animal and public health concerns can be addressed by withholding Zenrelia for at least 28 days to 3 months before vaccination and for at least 28 days afterward, and by making sure a dog is up-to-date on vaccinations before starting treatment. 

Zenrelia is only available by prescription from a licensed veterinarian because veterinary expertise is needed to determine whether Zenrelia is an appropriate treatment for your pet and to monitor the animal patient for the possible development of infections or other potential side effects while on the drug.