Veterinary Medicines Directorate Approves NUMELVI® (atinvicitinib) Tablets for Dogs

  • NUMELVI from MSD Animal Health is the Only Second-Generation Janus Kinase (JAK) Inhibitor for the Treatment of Pruritus Associated with Allergic Dermatitis, Including Atopic Dermatitis and Treatment of Clinical Manifestations of Atopic Dermatitis in Dogs
  • It is the only JAK inhibitor approved for use in dogs as young as six months of age (and 3kg).1

Milton Keynes, 26th March 2026 – MSD Animal Health, a division of Merck & Co., Inc., Rahway, N.J., USA (NYSE:MRK), today announced that the Veterinary Medicines Directorate (VMD) has approved NUMELVI ® (atinvicitinib) Tablets for Dogs.

NUMELVI is the first and only second‑generation Janus kinase (JAK) inhibitor indicated from six months of age (and 3kg) for the treatment of pruritus associated with allergic dermatitis, including atopic dermatitis, as well as the clinical manifestations of atopic dermatitis in dogs. With a once-daily treatment regimen, NUMELVI is clinically effective after the first dose, making it an ideal first-line treatment.

“Allergic dermatitis is a common condition that causes distress and discomfort for so many dogs. By combining targeted JAK1 selectivity with clinically-proven efficacy in a once‑daily regimen, NUMELVI helps make itch relief simple for dogs, pet owners and the veterinarians treating them,” said Victoria Miles, Companion Animal Director – Great Britain, MSD Animal Health.

NUMELVI is at least 10 times more selective for JAK1*1 compared to other JAK family members (JAK2, JAK3, and tyrosine kinase (TYK) 2). Thus, NUMELVI has very little to no effect on cytokines involved in haematopoiesis or immune function that are dependent on JAK2 or the other JAK family members. This selectivity contributes to NUMELVI’s favourable safety profile1 meaning it is approved as the only JAK inhibitor licensed for use in dogs as young as six months of age (and 3kg)1. It can also be used concurrently with vaccines (including rabies) and other common treatments such as ectoparasiticides. Additionally, there is no requirement for routine blood and urine monitoring.  Clinically, NUMELVI offers a rapid onset of action, beginning to relieve itch within 2–4 hours** and provides simple dosing of one tablet a day from day one.1

Reflecting on the clinical value of this innovation, Dr Debbie Gow BVM&S PhD DipECVD MBA FHEA FRCVS commented: “The high selectivity for JAK 1 contributes to the favourable safety profile of NUMELVI.”

Further highlighting the importance of selecting the right product for each dermatological case, Dr Sue Paterson MA VetMB DVD DipECVD FRCVS added: “Treating canine allergic dermatitis means offering treatment which relieves itch and inflammation.”

Miles added: “With this authorisation of NUMELVI, MSD Animal Health is proud to offer veterinarians and pet owners an innovative next generation JAK inhibitor that delivers meaningful benefits over current standard of care.”

            To mark the introduction of this new innovation to the UK veterinary community, MSD Animal Health will host the UK’s biggest lunch‑and‑learn digital launch event in partnership with The Webinar Vet on Thursday 26th March (registration link here). Recognising the significance of this therapeutic advancement, the event aims to set a Guinness World Record for a veterinary educational launch event.

This VMD market authorisation follows EU approval of the product in autumn 2025 for use in its member states.

### ENDS###

Notes to editors

*Over the other JAK enzymes in in vitro assays

**Based on a canine interleukin-31 induced pruritus model

1. NUMELVI® Summary of product characteristics

NUMELVI® (atinvicitinib) is a prescription medicine (POM-V) indicated for the treatment of pruritus associated with allergic dermatitis including atopic dermatitis, or for the treatment of clinical manifestations of atopic dermatitis, in dogs.

Further information is available from the SPC, datasheet or package leaflet.

Advice should be sought from the medicine prescriber.

Prescription decisions are for the person issuing the prescription alone.

Use medicines responsibly.

© 2026 Merck & Co., Inc., Rahway, NJ, USA and its affiliates. All rights reserved

About MSD Animal Health

MSD Animal Health, a division of Merck & Co., Inc., Rahway, N.J., USA, is a global animal health business committed to The Science of Healthier Animals™. For more than 130 years, we have pioneered groundbreaking science. Today, we are driven by continuous innovation to develop breakthrough medicines, vaccines and technology. Rooted in direct experience on the farm and in the clinic, we work hand in hand with our customers every step of the way. Our singular focus is to empower those who care for animals, helping them manage their vital responsibility with confidence. Because when it comes to animal health, no one sees it like we do.  For more information, visit www.msd-animal-health.com and connect with us on LinkedIn and X (formerly Twitter).

Forward-Looking Statement of Merck & Co., Inc., Rahway, N.J., USA

This news release of Merck & Co., Inc., Rahway, N.J., USA (the “company”) includes “forward-looking statements” within the meaning of the safe harbor provisions of the U.S. Private Securities Litigation Reform Act of 1995. These statements are based upon the current beliefs and expectations of the company’s management and are subject to significant risks and uncertainties. There can be no guarantees with respect to pipeline candidates that the candidates will receive the necessary regulatory approvals or that they will prove to be commercially successful. If underlying assumptions prove inaccurate or risks or uncertainties materialize, actual results may differ materially from those set forth in the forward-looking statements.

Risks and uncertainties include but are not limited to, general industry conditions and competition; general economic factors, including interest rate and currency exchange rate fluctuations; the impact of pharmaceutical industry regulation and health care legislation in the United States and internationally; global trends toward health care cost containment; technological advances, new products and patents attained by competitors; challenges inherent in new product development, including obtaining regulatory approval; the company’s ability to accurately predict future market conditions; manufacturing difficulties or delays; financial instability of international economies and sovereign risk; dependence on the effectiveness of the company’s patents and other protections for innovative products; and the exposure to litigation, including patent litigation, and/or regulatory actions.

The company undertakes no obligation to publicly update any forward-looking statement, whether as a result of new information, future events or otherwise. Additional factors that could cause results to differ materially from those described in the forward-looking statements can be found in the company’s Annual Report on Form 10-K for the year ended December 31, 2025 and the company’s other filings with the Securities and Exchange Commission (SEC) available at the SEC’s Internet site (www.sec.gov).