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.