FDA approves Numelvi for itch associated with allergic dermatitis

Merck Animal Health has secured FDA approval for Numelvi (atinvicitinib tablets), a once-daily oral therapy for the control of pruritus associated with allergic dermatitis in dogs 6 months of age and older. The approval, dated February 25, 2026, gives U.S. veterinarians a new prescription option in canine dermatology and introduces what Merck describes as the first and only second-generation JAK inhibitor approved for this use in the U.S. (fda.gov)

The approval lands in a market where itch control in dogs is already a major part of small animal practice. Merck says skin conditions account for up to 20% of cases seen in general veterinary practice, and the company has been building toward this launch for some time with conference data and regulatory progress outside the U.S. In June 2025, the European Medicines Agency’s Committee for Veterinary Medicinal Products issued a positive opinion for Numelvi, and the European Commission later authorized it in July 2025 for pruritus associated with allergic dermatitis, including atopic dermatitis. (merck-animal-health.com)

FDA’s Freedom of Information summary adds more detail than the initial announcement. The agency says the approved indication is control of pruritus associated with allergic dermatitis in dogs 6 months and older, under NADA 141-596. In the pivotal masked, randomized, placebo-controlled, multisite field study, 289 client-owned dogs were enrolled, with 250 included in the effectiveness analysis. Treatment success was defined as at least a 50% reduction from baseline pruritus on at least 5 of the first 7 treatment days. By Day 7, the estimated success proportion was 0.23 for Numelvi versus 0.07 for placebo, a statistically significant difference. Owner-assessed pruritus scores were lower in the Numelvi group at every measured time point after baseline, and investigator-assessed dermatitis scores were also lower at Days 7 and 28. (animaldrugsatfda.fda.gov)

The same FDA summary outlines the early safety picture. Adverse reactions related to treatment included gastrointestinal signs, including vomiting or nausea, plus hematology and serum chemistry abnormalities. In the field study safety set, vomiting or nausea was reported in 10 of 144 Numelvi-treated dogs, compared with 6 of 144 placebo-treated dogs. FDA also notes that the product qualifies for five years of marketing exclusivity from the approval date. (animaldrugsatfda.fda.gov)

Merck’s messaging has centered on selectivity and age range. The company says atinvicitinib is highly selective for JAK1, the pathway most closely tied to itch and inflammation, and emphasizes that Numelvi is the only JAK inhibitor approved in the U.S. for dogs as young as 6 months. That younger age threshold may be especially relevant for general practitioners managing early-onset allergic disease in juvenile dogs, though clinicians will still need to weigh label specifics, comorbidities, and monitoring needs when comparing options. This is partly an inference based on the approved age indication and the current competitive landscape. (merck.com)

Industry reaction so far has been positive and focused on quality-of-life gains. In coverage following the approval, Christine McKinney, senior professional services veterinarian of dermatology at Merck Animal Health, said reducing chronic itching may help prevent the chewing, licking, and scratching that can lead to skin damage, infections, pain, and poor sleep in affected dogs. That framing is consistent with how many veterinarians approach allergic dermatitis: itch control is not just about comfort, but also about interrupting the cycle of self-trauma and secondary complications. (vettimes.com)

Why it matters: For veterinary professionals, Numelvi broadens the treatment toolkit at a time when dermatology caseloads remain high and pet parents increasingly expect fast, practical relief. The product’s once-daily dosing, oral formulation, and approval in dogs 6 months and older may make it a useful option for some patients who are too young for other JAK-based therapies or who need an alternative within a multimodal allergy plan. At the same time, the FDA data suggest this is not a plug-and-play switch for every itchy dog: veterinarians will still need to confirm allergic dermatitis, rule out other causes of pruritus, manage infections and ectoparasites, and counsel pet parents on monitoring and expectations. (animaldrugsatfda.fda.gov)

What to watch: The next key developments are the commercial rollout in spring 2026, any publication of fuller peer-reviewed clinical data, and how quickly Numelvi finds a place relative to established anti-itch drugs and biologics in first-line and step-up care. Real-world safety and adherence patterns will matter, too, especially as clinics decide which canine allergy patients are the best fit for this newer JAK1-selective option. (merck-animal-health.com)