Systemic Pharmacokinetics, Safety, and Preliminary Efficacy of Topical AhR Agonist Tapinarof: Results of a Phase 1 Study

Tapinarof cream is a novel topical nonsteroidal agent that represents a unique class of anti-inflammatory molecules targeting the aryl hydrocarbon receptor. Study 201851 was an open-label, 2-cohort sequential study that assessed the systemic pharmacokinetics, safety, and efficacy of tapinarof in adults with moderate to severe atopic dermatitis. A total of 11 participants were enrolled: 5 received 2% cream, and 6 received 1% cream. Tapinarof was systemically absorbed, and measurable amounts were detected in both cohorts. Generally, plasma exposure was greater with the 2% cream and decreased from day 1 to day 21. Median T_max ranged from 1 to 4 hours. Preliminary efficacy results were similar between the 1% and 2% concentrations, with the 1% cream showing better tolerability based on 3 subjects in the 2% cohort who discontinued treatment because of systemic AEs. The efficacy and safety of 1% tapinarof support results of previous positive studies that used a different formulation. However, conclusions in the present study are limited because of the open-label design and small number of participants. The 1% cream was selected as the concentration for use in future studies because of its lower AE incidence and efficacy comparable to the 2% cream.