Numelvi®: Guide to Janus Kinase Inhibitors​ in Dogs with Allergic Skin Disease

JAK inhibitors (Janus Kinase inhibitor) help treat allergic skin disease in dogs. With the release of a new drug to the market we’re taking a closer look at what this means for veterinary dermatologists in the UK.

We’ll discuss:

• The Launch of Numelvi®

• What are Janus Kinase (Jak) Inhibitors and How Do They Work?

• The Different Types of Janus Kinase Inhibitors

• How Janus Kinase Inhibitors are Used in Dermatology

• Side Effects of Janus Kinase (JAK) Inhibitors​

• Offering Numelvi® as a Treatment

The Launch of Numelvi®

Numelvi® is a brand new anti-allergy, anti-itch drug for dogs launching in the UK early in 2026. Most vets do not know about it yet but it will be available to all UK vets very soon to help alleviate itch and the symptoms of allergy and atopic dermatitis in their allergic patients.

The Advanced Veterinary Dermatology team was invited by MSD to look at this new drug back in June 2025, alongside other eminent UK veterinary dermatologists. We have seen all the trial data showing how effective it is and safe. We’ve also been invited to help other vets through online education in relation to canine allergic skin disease and Numelvi®.

What are Janus Kinase (Jak) Inhibitors and How Do They Work?

A JAK inhibitor (Janus Kinase inhibitor) is a type of oral medication that helps calm an overactive immune system. It works by blocking specific enzymes called JAKs, which play a key role in the body’s immune response.

By targeting these enzymes, JAK inhibitors can reduce inflammation and help manage autoimmune and inflammatory conditions in people such as:

• Rheumatoid arthritis

• Psoriasis

• Eczema

• Ulcerative colitis

These medications provide a targeted approach to controlling symptoms and improving quality of life for people with immune-related conditions.

What are the Different Types of Janus Kinase Inhibitors?

In DOGS there are two, and with Numelvi® three JAK inhibitors. They ALL treat:

• Allergy - allergic and atopic dermatitis

However, Numelvi® is slightly different to the other two drugs, Apoquel® and Zenrelia®:

• Numelvi® can be used in dogs and pups from 6 months of age.

• Apoquel® and Zenrelia® can only be used from 12 months old.

• Numelvi® and Zenrelia® are ONCE daily dosing.

• Apoquel® typically is given TWICE daily for TWO weeks and then ONCE daily.

• Apoquel® and Zenrelia® will require monitoring of blood and occasionally urine.

• Numelvi® is a second generation JAK inhibitor and will NOT require monitoring.

Apoquel has been available for use for over 10 years and trialled by experts around the world. It’s been used for different immune-mediated and auto-immune conditions. The other drugs may be beneficial for other conditions too but it is too soon to say. Zenrelia® was released in the UK in August 2025, so it is also a new drug.

These drugs can ONLY be used in dogs and it is not currently considered safe to use in cats.

How are Janus Kinase Inhibitors Used in Dermatology?

JAK inhibitors in dogs are primarily used to treat the itch associated with allergy and atopic dermatitis in dogs. They are tablet medications and are only available as a prescription medication from your vet.

JAK inhibitors are quick to act, getting to work in less than 24 hours for instance Numelvi® acts in 2 to 4 hours to treat symptoms.

Are There any Side Effects of Janus Kinase (JAK) Inhibitors​?

Numelvi® is safe and side effects are often mild. The product data sheet lists mild effects in 1-10 dogs out of every 100:

• Vomiting

• Diarrhoea

• Lethargy

• Reduced appetite

There is NO effect on the blood cells, as is sometimes seen with other JAK inhibitors. Therefore there is no need to monitor blood and urine when using Numelvi®.

You can view the databases and statements for more information:

• European Union Product Database

• MSD Numelvi Statement

  
  

Which Janus Kinase Inhibitor​ is right for my dog?

They all have a place and some of the drugs may offer benefits over others. Your dog may respond to one over another. Your vet will be able to advise on which type is best for your dog and their allergy symptoms.

Do you Offer Numelvi® as a Treatment?

Numelvi® will be available in the UK soon as an allergy treatment. It’s availability is imminent and it’s already being used by vets in Europe and even further abroad.

ALL vets in the UK will have access to it at the same time but it often takes time for a new drug to gain traction with veterinary professionals. However, it will be available from Advanced Veterinary Dermatology my practice as soon as it is with our suppliers.

“I shall certainly be prescribing Numelvi® to my patients and I am looking forward to seeing its benefits, especially in our younger pups.” Dr Simon Want BVM&S CertVD MRCVS

Numelvi® and Advanced Veterinary Dermatology

Numelvi® is a new JAK inhibitor to treat the symptoms of allergic skin disease and atopic dermatitis in dogs from as young as 6 months of age. It will be available in the UK very soon and should be priced cheaper than alternative JAK inhibitors, making it more available to some clients and their pets.

Advanced Veterinary Dermatology will be using this drug as soon as it is launched in the UK and we have been invited to help other vets through online education in relation to canine allergic skin disease and Numelvi®.

If you wish to discuss this drug as part of an overall strategy to treat your allergic dog please contact our team who will be happy to make an appointment to see one of our veterinary dermatologists.

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Sources and References:

• The Veterinary Times: Article on the launch of Numelvi®

Written and Approved by:

Dr Simon Want BVM&S CertVD MRCVS

RCVS Advanced Practitioner in Veterinary Dermatology

Director of Advanced Veterinary Dermatology Ltd