Ivarmacitinib for Moderate to Severe Atopic Dermatitis in Adults and Adolescents

Importance: Ivarmacitinib, a selective oral Janus kinase 1 (JAK1) inhibitor, has demonstrated efficacy for treating adults with moderate to severe atopic dermatitis (AD) in a phase 2 trial. Objective: To evaluate the efficacy and adverse events of ivarmacitinib in adolescents and adults with moderate to severe AD. Design, Setting, and Participants: This multicenter, double-blind, placebo-controlled phase 3 randomized clinical trial included patients aged 12 to 75 years with moderate to severe AD. Patients were enrolled from 53 sites in Canada and China from April 2021 to April 2022. Data were analyzed from July 11 to September 27, 2023. Interventions: Patients were randomized (1:1:1) to receive once-daily 4- or 8-mg ivarmacitinib or placebo for 16 weeks. Main Outcomes and Measures: Co-primary end points were the proportions of patients achieving an Investigator Global Assessment (IGA) score of 0 (clear) or 1 (almost clear) with at least a 2-grade improvement from baseline and an Eczema Area and Severity Index score improvement of 75% (EASI-75) at week 16. Results: Of 336 randomized patients (mean [SD] age, 31.1 [15.4] years; 213 [63.4%] male; 286 [85.1%] Asian), 113 received 4-mg ivarmacitinib, 112 received 8-mg ivarmacitinib, and 111 received placebo. At week 16, significantly more patients in the 4-mg ivarmacitinib group (41 of 113 [36.3%]; 95% CI, 27.5%-45.9%; P < .001) and the 8-mg ivarmacitinib group (47 of 112 [42.0%]; 95% CI, 32.7%-51.7%; P < .001) achieved an IGA score of 0 or 1 with at least a 2-grade improvement compared to the placebo group (10 of 111 [9.0%]; 95% CI, 4.4%-15.9%). EASI-75 responses were also significantly higher in the ivarmacitinib groups: 61 patients (54.0%; 95% CI, 44.4%-63.4%; P < .001) in the 4-mg group, and 74 (66.1%; 95% CI, 56.5%-74.8%; P < .001) in 8-mg group compared to 24 patients (21.6%; 95% CI, 14.4%-30.4%) in the placebo group. Treatment-emergent adverse events were reported by 78 patients (69.0%) in the 4-mg group, 74 (66.1%) in the 8-mg group, and 72 (64.9%) in the placebo group. Serious treatment-emergent adverse events occurred in 3 patients (2.7%) in the 4-mg group, 2 (1.8%) in the 8-mg group, and 3 (2.7%) in the placebo group. Conclusions and Relevance: This phase 3 randomized clinical trial determined that once-daily ivarmacitinib demonstrated significant efficacy and a favorable risk-benefit profile for treating moderate to severe AD in adults and adolescents. These results support the potential of ivarmacitinib as a new therapeutic option. Trial Registration: ClinicalTrials.gov Identifier: NCT04875169.