Background Baricitinib, an oral selective inhibitor of Janus kinase 1 and Janus kinase 2, modulates proinflammatory cytokine signaling.

Objectives The efficacy and safety of baricitinib were evaluated in patients with moderate-to-severe atopic dermatitis (AD).

Methods In this phase 2, randomized, double-blind, placebo-controlled study, 124 patients with moderate-to-severe AD applied topical corticosteroids (TCSs) for 4 weeks before randomization to once-daily placebo, 2 mg of baricitinib, or 4 mg of baricitinib for 16 weeks. Use of TCSs was permitted during the study. The primary outcome was the proportion of patients achieving at least a 50% reduction in the Eczema Area and Severity Index (EASI-50) compared with placebo.

Results Significantly more patients who received baricitinib, 4 mg, achieved EASI-50 than did patients receiving placebo (61% vs 37% [P = .027]) at 16 weeks. The difference between the proportion of patients receiving baricitinib, 2 or 4 mg, who achieved EASI-50 and the proportion of patients receiving placebo and achieving EASI-50 was significant as early as week 4. Baricitinib also improved pruritus and sleep loss. Treatment-emergent adverse events were reported in 24 of the patients receiving placebo (49%), 17 of those receiving 2 mg of baricitinib (46%), and 27 of those receiving 4 mg of baricitinib (71%).

Limitations A TCS standardization period before randomization reduced disease severity, limiting the ability to compare results with those of baricitinib monotherapy. Longer studies are required to confirm baricitinib's efficacy and safety in patients with AD.