The U.S. Food and Drug Administration has approved significant updates to the Zenrelia FDA approval label, removing critical safety warnings about fatal vaccine-induced disease from the revolutionary dog allergy medication. This important revision comes just one year after the drug’s initial approval in September 2024, following extensive review of supplemental scientific data by federal regulators.
Zenrelia, manufactured by Elanco Animal Health, represents a breakthrough treatment for dogs suffering from allergic dermatitis and atopic dermatitis. The once-daily oral medication uses ilunocitinib, a Janus kinase (JAK) inhibitor that works by blocking itch receptors under the skin and reducing inflammatory processes triggered by allergies. More than half a million dogs worldwide have already been treated with this innovative therapy.
Significant Safety Label Changes Remove Fatal Disease Warning
The most substantial change to the Zenrelia label involves the removal of language warning about the risk of fatal vaccine-induced disease from modified live virus vaccines. When originally approved, the label contained stern warnings based on laboratory study results where unvaccinated dogs received three times the recommended dose of Zenrelia. During that controversial study, an outbreak of concurrent diseases occurred, complicating the interpretation of results and leading to the death of two dogs from vaccine-related complications.
The FDA now concludes that “the totality of evidence supports removal of the risk of fatal vaccine-induced disease from modified live virus vaccines from the labeling.” This determination followed careful evaluation of additional scientific data submitted by Elanco, bringing the U.S. label closer to approved versions in the European Union, Great Britain, Brazil, and Japan. Despite this positive change, important vaccination-related precautions remain in place.
Veterinarians must still discontinue Zenrelia for at least 28 days to three months prior to vaccination and withhold the medication for at least 28 days after vaccination due to the continued risk of inadequate immune response to vaccines. Dogs should be current on all vaccinations before beginning Zenrelia treatment, as the medication works partly by suppressing the immune system.
Real-World Success Drives Regulatory Confidence
The label update reflects growing confidence in Zenrelia’s safety profile based on extensive real-world usage data. Veterinary dermatologists and general practice veterinarians across the United States have reported positive outcomes, with the medication effectively controlling pruritus and skin lesions in dogs with allergic conditions. Clinical trials demonstrated that Zenrelia showed similar efficacy to Apoquel, the current market-leading JAK inhibitor, at the primary endpoint of Day 28.
Dr. Ellen DeBrabander, Executive Vice President of Research and Development at Elanco, emphasized the company’s commitment to generating additional safety data. “We appreciate the FDA’s commitment to reviewing the latest submitted scientific data to ensure that the label is reflective of the totality of evidence,” she stated in the company announcement.
The medication remains indicated for dogs at least 12 months of age and should not be used in animals with serious infections. Common adverse reactions observed in clinical trials include vomiting, diarrhea, and lethargy. Pet owners interested in this treatment option should consult with their veterinarians to determine if Zenrelia is appropriate for their dogs, particularly those with histories of neurological issues or immune system concerns.
This regulatory update represents a significant milestone in veterinary dermatology, providing veterinarians and pet owners with increased confidence in using Zenrelia for managing chronic allergic skin conditions in dogs. The revised labeling is expected to improve treatment accessibility while maintaining essential safety protocols for vaccine administration.