FDA approves Numelvi for itch associated with allergic dermatitis

Numelvi, a new once-daily oral JAK inhibitor from Merck Animal Health, has won FDA approval for the control of pruritus associated with allergic dermatitis in dogs 6 months of age and older. The product, atinvicitinib tablets, was approved on February 25, 2026, and FDA’s recent animal drug approvals listing confirms the indication and age threshold. Merck is positioning Numelvi as the first and only second-generation, JAK1-selective inhibitor in this category, with U.S. availability expected in spring 2026. (fda.gov)

Why it matters: For veterinarians, the approval adds another systemic anti-pruritic option in a crowded but evolving canine dermatology market, and one that can be used in younger dogs than some competing JAK products. In the FDA Freedom of Information summary, the pivotal field study enrolled 289 client-owned dogs with allergic dermatitis, and the primary effectiveness analysis found a higher Day 7 treatment-success rate with Numelvi than placebo, based on owner-assessed itch reduction. The same FDA summary says adverse reactions related to treatment included gastrointestinal signs such as vomiting or upset stomach, along with hematology and serum chemistry abnormalities, underscoring the need for case selection and monitoring. (animaldrugsatfda.fda.gov)

What to watch: Watch for launch timing this spring, real-world uptake in general practice and dermatology, and how clinicians position Numelvi alongside existing JAK inhibitors and biologics. (merck-animal-health.com)