Numelvi™ (atinvicitinib tablets)

Immunomodulator
253661 R1

For oral use in dogs only

CAUTION: Federal law restricts this drug to use by or on the order of a licensed veterinarian.

DESCRIPTION:

The active ingredient in NUMELVI is atinvicitinib. Atinvicitinib is a synthetic selective Janus kinase (JAK) 1 inhibitor. The chemical (IUPAC) name of atinvicitinib is 1-[(3R,4S)-4-cyanooxan-3-yl]-3-[(2-fluoro-6-methoxypyridin-4-yl)amino]-1H-pyrazole-4-carboxamide.

INDICATIONS:

NUMELVI is indicated for the control of pruritus associated with allergic dermatitis in dogs 6 months of age and older.

DOSAGE AND ADMINISTRATION:

NUMELVI should be administered orally, once daily, at a dose of 0.36 to 0.54 mg atinvicitinib/lb (0.8 to 1.2 mg atinvicitinib/kg) body weight according to the Dosing Table below.

NUMELVI should be administered with food.

Dosing Table

The effectiveness and safety of NUMELVI have not been evaluated in a field study beyond 28 days (see Adverse Reactions and Effectiveness).

The safe use of NUMELVI has not been evaluated in breeding, pregnant, or lactating dogs. Decreased mean testes weight was observed in a laboratory safety study (see Target Animal Safety).

The safe use of NUMELVI has not been evaluated in combination with glucocorticoids, cyclosporine, or other systemic immunosuppressive agents.

In a masked field study assessing effectiveness and safety of NUMELVI for the control of pruritus associated with allergic dermatitis in dogs, 144 NUMELVI-treated dogs and 144 placebo-treated dogs were evaluated for safety for up to 28 days. Adverse reactions seen during the field study are summarized in Table 1 below.

Abnormal hematology results likely related to NUMELVI administration included leukopenia, neutropenia, eosinopenia, monocytopenia, and lymphocytosis.

Abnormal serum chemistry results likely related to NUMELVI administration included increased alanine aminotransferase (ALT), aspartate aminotransferase (AST), and symmetric dimethylarginine (SDMA), and hypercholesterolemia.

Three NUMELVI-treated dogs withdrew from the study early due to an adverse reaction, two of which were considered likely related to NUMELVI treatment (i.e., diarrhea). Two placebo-treated dogs also withdrew from the study early due to an adverse reaction (i.e., diarrhea).

For technical information or to report a suspected adverse event, please contact Merck Animal Health at 1-800-224-5318 or www.merck-animal-health-usa.com. Safety Data Sheets (SDSs) can be found at www.merck.com/products/safety-data-sheets/#.

For additional information about reporting adverse drug experiences for animal drugs, contact FDA at 1-888-FDA-VETS or www.fda.gov/reportanimalae.

EFFECTIVENESS:

A masked, 28-day, placebo-controlled study was conducted at 26 veterinary clinics in the US, enrolling 288 client-owned dogs diagnosed with allergic dermatitis and having at least moderate pruritus. The allergic dermatitis was attributed to one or more of the following conditions (in the order of frequency): atopic dermatitis, unspecified allergic dermatitis, food hypersensitivity, flea allergy dermatitis, and contact dermatitis. Dogs were randomized to once daily treatment with NUMELVI at 0.8 - 1.2 mg/kg or placebo, at a ratio of 1:1 respectively. Other medications that could affect the evaluation of effectiveness were not allowed during the study, such as corticosteroids, antihistamines, and cyclosporine. Treatment success for each dog was defined as a ≥ 50% reduction from baseline in owner-assessed pruritus scores on the Pruritus Visual Analog Scale (PVAS) on at least 5 out of the first 7 days of treatment. The proportion of dogs in the NUMELVI group that were treatment successes was greater than and significantly different compared to the placebo group on Day 7 (Table 2, below).

Mean owner-assessed PVAS scores were lower in the NUMELVI group after Day 0 (Figure 1, below).

Figure 1: Mean owner-assessed PVAS Scores by Treatment for Days 0-7

Veterinarians used a Dermatitis Visual Analog Scale (DVAS) to assess each dog's dermatitis. Veterinarian-assessed DVAS scores were lower for the NUMELVI group compared to the placebo group at all time points through Day 28.

NUMELVI tablets should be stored at 15 to 30°C (59 to 86°F).

NUMELVI (atinvicitinib tablets) is available in scored tablets in four strengths: 4.8 mg, 7.2 mg, 21.6 mg, and 31.6 mg per tablet. Each tablet strength is available in 30 and 90 count bottles. Each tablet is marked with an S, M, L, or XL that correspond to the different tablet strengths.

Approved by FDA under NADA # 141-596

Distributed by Intervet Inc. (d/b/a Merck Animal Health), Rahway, NJ 07065.
Copyright © 2026 Merck & Co., Inc., Rahway, NJ, USA and its affiliates.
All rights reserved.
Rev. 06/2026

MERCK
Animal Health

Numelvi™
(atinvicitinib tablets)

4.8 mg

FOR ORAL USE IN DOGS ONLY

Caution: Federal law restricts
this drug to use by or on the order
of a licensed veterinarian.

Approved by FDA under
NADA # 141-596

90 Tablets

MERCK
Animal Health

Numelvi™
(atinvicitinib tablets)

7.2 mg

FOR ORAL USE IN DOGS ONLY

Caution: Federal law restricts
this drug to use by or on the order
of a licensed veterinarian.

Approved by FDA under
NADA # 141-596

90 Tablets

MERCK
Animal Health

Numelvi™
(atinvicitinib tablets)

21.6 mg

FOR ORAL USE IN DOGS ONLY

Caution: Federal law restricts this drug to use
by or on the order of a licensed veterinarian.

Approved by FDA under NADA # 141-596

90 Tablets

MERCK
Animal Health

Numelvi™
(atinvicitinib tablets)

31.6 mg

FOR ORAL USE IN DOGS ONLY

Caution: Federal law restricts this drug to use
by or on the order of a licensed veterinarian.

Approved by FDA under NADA # 141-596

90 Tablets

MERCK
Animal Health