In adolescents and adults with atopic dermatitis, the use of 1.5% ruxolitinib cream was well-tolerated, with most adverse effects of mild or moderate severity. Furthermore, it displayed a high level of efficacy in people with atopic dermatitis involving ≥ 25% affected body surface area.

An open-label, maximum-use phase I study [maximum-use trial (MUsT)] was carried out to assess tolerability, safety, and bioavailability of ruxolitinib cream under maximum-use conditions in people with extensive atopic dermatitis lesions. Efficacy was evaluated as an exploratory objective.

In this study, patients (age ≥ 12-65 years) having atopic dermatitis, and an Investigator’s Global Assessment (IGA) score ≥ 2, and ≥ 25% affected body surface area were recruited. The participants applied 1.5% ruxolitinib cream twice daily to lesions detected at the baseline for the first twenty-eight days and continued use only on active lesions for an extra 28 days (extension period).

With the aid of duration, frequency, and severity of treatment-emergent adverse events, an assessment of safety was done. The plasma concentrations of ruxolitinib and pharmacokinetic parameters were evaluated as secondary outcomes.

In total, 41 people (51% men; median age 17 years) were recruited and 37 (90.2%) entered the extension period, all of whom finished the study. In 13 people (31.7%), treatment-emergent adverse events were witnessed while in 4 people (9.8%), treatment-related adverse events were reported.

The mean (standard deviation) steady-state plasma concentration was found to be 104 (309) nM during the initial 28 days. This concentration was well below the half-maximal inhibitory concentration of Janus kinase-mediated myelosuppression in bone marrow (281 nM), and reduced further during extension period.

The higher plasma concentrations were detected in a few people who were treated for a very high affected body surface area. On day 56, 94.6% of people attained ≥ 75% improvement in the Eczema Area and Severity Index (EASI).

Under maximum-use conditions, ruxolitinib cream (a topical formulation of ruxolitinib) showed good tolerability, with nearly one-third of people experiencing treatment-emergent adverse events and few treatment-linked adverse events. Ruxolitinib cream significantly decreased itch and inflammation in atopic dermatitis people with ≥ 25% affected body surface area.