Clinical Tailoring of Baricitinib 2 mg in Atopic Dermatitis: Baseline Body Surface Area and Rapid Onset of Action Identifies Response at Week 16

Introduction: Baricitinib, an oral Janus kinase (JAK)1/JAK2 inhibitor, is indicated in the European Union and Japan for treatment of moderate-to-severe atopic dermatitis (AD) in adults who are candidates for systemic therapy. In the ongoing, placebo-controlled, phase 3 trial BREEZE-AD5, once-daily oral baricitinib 2-mg monotherapy improved disease in moderate-to-severe AD patients who had an inadequate response or intolerance to topical corticosteroids. This post-hoc analysis aimed to identify responders to baricitinib 2 mg, using a proposed clinical tailoring approach based on baseline body surface area (BSA) affected and early clinical improvement, in BREEZE-AD5. Methods: Classification and regression tree method was used to evaluate baseline predictors for the proportion of patients achieving ≥ 75% improvement in Eczema Area and Severity Index (EASI75) at week 16 among baricitinib 2-mg-treated patients. Two-by-two contingency tables evaluated the association between early response, defined as ≥ 50% improvement in BSA or ≥ 3-point improvement in Itch Numeric Rating Scale from baseline at weeks 4 or 8, and response at week 16 for the proportion of patients achieving EASI75, validated Investigator Global Assessment for AD (vIGA-AD) score of 0 or 1, or ≥ 4-point improvement in Itch (Itch ≥ 4), respectively. Missing data were imputed as non-responder. Results: At week 16, EASI75 and vIGA-AD (0,1) were achieved by 37.5% and 31.7% of baricitinib 2-mg-treated patients with baseline BSA 10–50% compared with 9.5% and 4.8% with BSA > 50%. Early response in skin inflammation or itch at week 4 was associated with corresponding EASI75, vIGA-AD (0,1), and Itch ≥ 4 of 55.4%, 48.2%, and 39.3% at week 16, while early response at week 8 was associated with 66.7%, 56.1%, and 42.1% of patients achieving these endpoints. Conclusion: Baseline BSA of 10–50% and early clinical improvement after 4 or 8 weeks of baricitinib 2-mg treatment may identify patients most likely to benefit from long-term baricitinib 2-mg therapy. Clinical Trial Registration: NCT03435081.