Efficacy and Field Safety of Ilunocitinib for the Control of Allergic Dermatitis in Client-Owned Dogs: A Multicenter, Double-Masked, Randomised, Placebo-Controlled Clinical Trial.

Background: Inhibition of the Janus kinase pathway is an established treatment for allergic dermatitis.

Objective: To evaluate the efficacy and safety of ilunocitinib for control of pruritus in dogs with allergic dermatitis in a randomised, double-masked clinical trial.

Animals: Three-hundred-and-six dogs at 15 veterinary clinics.

Materials and methods: Enrolled client-owned dogs with severe pruritus and a presumptive diagnosis of allergic dermatitis were randomised to receive either ilunocitinib (n = 206; 0.6-0.8 mg/kg) or placebo (n = 100; 0 mg/kg) once daily for 28 days. Pruritus was assessed by owners using a pruritus Visual Analog Scale (PVAS). Treatment success was defined as ≥ 50% reduction from baseline PVAS on at least five of seven initial treatment days. Clinical remission from pruritus was considered achieved when PVAS < 2. Safety assessments were conducted over 112 days.

Results: On Day (D)7, 25.4% of ilunocitinib-treated dogs achieved treatment success compared to 7.7% of placebo dogs (p = 0.006). Starting on D3, the proportion of dogs with a ≥ 50% reduction from baseline PVAS was significantly higher in the ilunocitinib group (p < 0.01) and by D28, a significantly higher percentage of ilunocitinib-treated dogs (51.8%) achieved clinical remission compared to placebo dogs (12.7%; p < 0.05). Signs of dermatitis improved within 7 days. The 112-day ilunocitinib treatment was well-tolerated.

Conclusions and clinical relevance: Ilunocitinib administered once a day was well tolerated and effective at rapidly reducing pruritus, with steady and continuous improvement over time. Clinical remission of pruritus was achieved by 51.8% of ilunocitinib-treated dogs by D28, regardless of allergic aetiology.