FDA Approves NUMELVI™ (atinvicitinib tablets) for Dogs from Merck Animal Health – The First and Only Second-Generation Janus Kinase (JAK) Inhibitor for the Control of Pruritus Associated with Allergic Dermatitis
28 February 2026, Rahway: Merck Animal Health, known as MSD Animal Health outside of the United States and Canada, a division of Merck & Co., Inc., Rahway, N.J., USA (NYSE:MRK), announced today the U.S. Food and Drug Administration (FDA) approval of NUMELVI™ (atinvicitinib tablets) – the first and only second-generation Janus kinase (JAK) inhibitor indicated for the control of pruritus associated with allergic dermatitis in dogs six months of age and older. The product is expected to be available at veterinary clinics and hospitals nationwide in spring 2026.
“Merck Animal Health is proud to introduce NUMELVI, our latest advancement geared at rapidly controlling pruritus associated with allergic dermatitis, a common condition that causes distress for so many pets and pet owners,” said Christine McKinney, DVM, DACVD and Senior Professional Services Veterinarian, Merck Animal Health.
“With more than 70 years of innovation and commitment to animal health, we are confident that NUMELVI will offer veterinary professionals a groundbreaking, first-of-its-kind solution aimed at improving the health and well-being of dogs – from as young as six months to mature dogs – and ultimately providing peace of mind for the people who care for them,” added McKinney. “NUMELVI also offers added convenience for veterinary clinics; most dogs, starting at weights as low as 4.4 pounds, require only one or half of a tablet, and there is no need to adjust vaccination schedules. Plus, NUMELVI comes in easy‑to‑dispense bottles and can be stored under standard conditions. Its active ingredient is intrinsically stable, providing the longest shelf life among JAK inhibitor tablets in veterinary medicine.”
Key Information:
Why NUMELVI is needed: Skin conditions are common in dogs and can account for up to 20% of cases seen in general veterinary practice1. As allergic dermatitis progresses, quality of life in dogs and the human-animal bond can be significantly impacted due to physical discomfort, emotional distress, and interruptions in sleep and routines due to itchiness and skin lesions2.
How NUMELVI works: NUMELVI is a once-daily, first-line treatment that leads to a significant reduction in itch from the first dose. It is at least 10 times more selective for JAK1 than for JAK2, JAK3 and TYK2 in in vitro assays3 and inhibits the effect of JAK1-dependent cytokines involved in itch and inflammation in allergic dermatitis including atopic dermatitis. High selectivity for JAK1 can minimize interference with the beneficial immune functions of the other JAKs4, resulting in a compelling safety profile with proven efficacy. Moreover, NUMELVI (atinvicitinib tablets) is the only JAK inhibitor approved for use in dogs as young as six months of age.
“Merck Animal Health is continuously working to expand its portfolio to include innovative veterinary medicinal products that meet the needs of dogs and their owners,” said Tim Kowalski Distinguished Scientist, Discovery Research, Merck Animal Health. “NUMELVI, a second-generation JAK inhibitor, is the first of its kind to enter the market in veterinary medicine, giving it a unique profile compared with other JAK inhibitors. Second-generation JAK inhibitors are already considered the standard of care in human health, and NUMELVI brings that same advanced approach to veterinary medicine.”
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