atinvicitinib

Atinvicitinib is a second-generation selective Janus kinase 1 (JAK1) inhibitor developed by Merck Animal Health for veterinary use. Marketed under the brand name NUMELVI, it is a small molecule formulated as an oral tablet. It exhibits high selectivity for JAK1, being at least 10 times more selective for JAK1 compared to JAK2, JAK3, and TYK2. This selectivity allows the drug to effectively inhibit JAK1-dependent cytokines involved in the signaling pathways of itch and inflammation while minimizing off-target effects associated with other JAK family members. Atinvicitinib is indicated for the control of pruritus associated with allergic dermatitis, including atopic dermatitis, in dogs six months of age and older. It received FDA approval in the United States in February 2026 and European approval in 2025.

Brand names

NUMELVI