Pharmacokinetics, Safety, Tolerability, and Exploratory Efficacy of Upadacitinib in Children with Severe Atopic Dermatitis.

Purpose: This study aims to characterize the pharmacokinetics, safety, tolerability, and exploratory efficacy of upadacitinib, an oral Janus kinase inhibitor approved for treating moderate to severe atopic dermatitis (AD) in adults and adolescents, in children with severe AD.

Methods: In an open-label, multiple-dose, Phase 1 study, pediatric patients with severe AD from two age groups (2 to <6 years and 6 to <12 years) received bodyweight-based dosing regimens of upadacitinib using either twice-daily immediate-release (IR) oral solution or once-daily extended-release (ER) tablets. A pharmacokinetic assessment was conducted on Day 7 of the study, which was followed by a long-term safety and exploratory efficacy evaluation for up to 108 weeks. The results reported here are based on an interim analysis when the study had completed enrollment and pharmacokinetic assessment.

Findings: A total of 35 patients were enrolled and received upadacitinib. The maximum upadacitinib plasma concentration was attained within a median time of 0.5 to 2 hours and 2 to 2.5 hours for the IR oral solution and ER tablet formulations, respectively. Upadacitinib functional half-life was generally shorter with IR oral solution relative to ER tablets. Upadacitinib apparent oral clearance decreased with decreasing body weight in the pediatric patients enrolled in this study. Upadacitinib was generally safe and well tolerated. The most common (≥3 patients) adverse events were upper respiratory tract infection, COVID-19 infection, headache, abdominal discomfort, vomiting, asthma, and cough. No new safety risks were identified compared to the known safety profile for upadacitinib in adults and adolescents. In the 30 patients with available exploratory efficacy data at Week 12, 36.7% achieved validated Investigator's Global Assessment scale for AD score of 0 or 1 (Validated Investigator Global Assessment for AD 0/1), and 70.0% had Eczema Area and Severity Index (EASI) improvement of at least 75% (EASI 75).

Implications: The characterized pharmacokinetic profiles in this study, together with the observed safety and exploratory efficacy results, support further investigation of the current upadacitinib dosing regimen in future confirmatory Phase 3 clinical trials in children with AD.

Clinical Trial Number: NCT03646604, registered 2018-08-23.