Efficacy and Field Safety of the Second-Generation, Highly Selective JAK1 Inhibitor Atinvicitinib for the Treatment of Canine Atopic Dermatitis: A Multicentre, Blinded, Randomised, Placebo-Controlled Clinical Trial in Client-Owned Dogs

BACKGROUND: Janus kinase (JAK) inhibitors alleviate pruritus and clinical signs of canine atopic dermatitis (cAD). OBJECTIVE: To confirm the optimal dosing regimen of atinvicitinib, a second-generation highly selective inhibitor of JAK1 in dogs. ANIMALS: Sixty-one client-owned dogs, ≥ 12 months and ≥ 2 kg, with cAD. MATERIALS AND METHODS: In a randomised, masked, placebo-controlled clinical trial, dogs received atinvicitinib, with food, at 0.8-1.2 mg/kg, once daily for 28 days (q.d. group, n = 21) or 0.4-0.6 mg/kg twice daily for 14 days followed by once daily dosing for 14 days (b.i.d.-q.d. group, n = 21); or placebo b.i.d.-q.d. (control group, n = 19). Owners assessed pruritus (Day [D]0-7, D14, D28) using a Visual Analog Scale (PVAS); veterinary surgeons assessed skin lesions (D0, D28) using the cAD Extent and Severity Index, 4th iteration (CADESI-04). On D0, D14 and D28, blood and urine samples were collected. Treatment success was defined as a ≥ 50% reduction from baseline PVAS or CADESI-04 on D28. Proportions of dogs with ≥ 2 PVAS reduction, and reduction in PVAS and/or CADESI-04 from baseline, also were assessed. RESULTS: Treatment success was 87.5% for the q.d. group (p = 0.011) and 73.3% for the b.i.d.-q.d. group (p = 0.033) (23.1% control group). There was ≥ 2 decrease in PVAS in 80.0% of q.d. dogs. (16.7% controls, p = 0.042). Compared to controls, atinvicitinib-treated dogs had a significantly greater reduction in PVAS (q.d., p = 0.003, b.i.d.-q.d., p = 0.001) and CADESI-04 (q.d. group, p = 0.046). Mean results of clinical pathological values remained within reference ranges. Treatment was well-tolerated. CONCLUSIONS AND CLINICAL RELEVANCE: Once-daily atinvicitinib was safe, well-tolerated and effective at rapidly reducing pruritus and resolving cAD-associated skin lesions.

Authors: F. Jirjis, T. J. Kowalski, R. C. Lynn, L. Overbey, Q. Cao, M. Stock and I. Kuhlmann Title: Efficacy and Field Safety of the Second-Generation, Highly Selective JAK1 Inhibitor Atinvicitinib for the Treatment of Canine Atopic Dermatitis: A Multicentre, Blinded, Randomised, Placebo-Controlled Clinical Trial in Client-Owned Dogs Full source: Vet Dermatol, 2026,Vol Document type: Journal Article
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BACKGROUND: Janus kinase (JAK) inhibitors alleviate pruritus and clinical signs of canine atopic dermatitis (cAD). OBJECTIVE: To confirm the optimal dosing regimen of atinvicitinib, a second-generation highly selective inhibitor of JAK1 in dogs. ANIMALS: Sixty-one client-owned dogs, ≥ 12 months and ≥ 2 kg, with cAD. MATERIALS AND METHODS: In a randomised, masked, placebo-controlled clinical trial, dogs received atinvicitinib, with food, at 0.8-1.2 mg/kg, once daily for 28 days (q.d. group, n = 21) or 0.4-0.6 mg/kg twice daily for 14 days followed by once daily dosing for 14 days (b.i.d.-q.d. group, n = 21); or placebo b.i.d.-q.d. (control group, n = 19). Owners assessed pruritus (Day [D]0-7, D14, D28) using a Visual Analog Scale (PVAS); veterinary surgeons assessed skin lesions (D0, D28) using the cAD Extent and Severity Index, 4th iteration (CADESI-04). On D0, D14 and D28, blood and urine samples were collected. Treatment success was defined as a ≥ 50% reduction from baseline PVAS or CADESI-04 on D28. Proportions of dogs with ≥ 2 PVAS reduction, and reduction in PVAS and/or CADESI-04 from baseline, also were assessed. RESULTS: Treatment success was 87.5% for the q.d. group (p = 0.011) and 73.3% for the b.i.d.-q.d. group (p = 0.033) (23.1% control group). There was ≥ 2 decrease in PVAS in 80.0% of q.d. dogs. (16.7% controls, p = 0.042). Compared to controls, atinvicitinib-treated dogs had a significantly greater reduction in PVAS (q.d., p = 0.003, b.i.d.-q.d., p = 0.001) and CADESI-04 (q.d. group, p = 0.046). Mean results of clinical pathological values remained within reference ranges. Treatment was well-tolerated. CONCLUSIONS AND CLINICAL RELEVANCE: Once-daily atinvicitinib was safe, well-tolerated and effective at rapidly reducing pruritus and resolving cAD-associated skin lesions.