Phase 2, randomized, double‐blind, placebo‐controlled, 4‐week study to evaluate the safety and efficacy of OPA‐ 15406 (difamilast), a new topical selective phosphodiesterase type‐4 inhibitor, in Japanese pediatric patients aged 2–14 years with atopic dermatitis

The safety and efficacy of OPA‐15406 (international non‐proprietary name, difamilast; also referred to as MM36), a new topical, selective phosphodiesterase type‐4 inhibitor, in Japanese pediatric patients with atopic dermatitis aged 2–14 years were evaluated in a phase 2, randomized, double‐blind, vehicle‐controlled, 4‐week study. Seventy‐three patients were randomized 1:1:1 to receive OPA‐15406 0.3%, OPA‐15406 1% or vehicle ointment twice daily for 4 weeks. The mean age of patients was similar across treatment groups. No deaths or serious treatment‐emergent adverse events were reported; all treatment‐emergent adverse events were mild or moderate in severity. The incidence of treatment‐emergent adverse events leading to treatment discontinuation was 4.2% (1/24) in the OPA‐15406 0.3% group, 4.0% (1/25) in the OPA‐15406 1% group and 16.7% (4/24) in the vehicle group, all of which were worsening of atopic dermatitis. Both OPA‐15406 groups demonstrated a higher incidence of success in the Investigator Global Assessment score compared with the vehicle group over the 4‐week study. The OPA‐15406 groups also showed greater improvements from baseline compared with the vehicle group in the Investigator Global Assessment score, Eczema Area and Severity Index overall score and subscale (erythema, induration/papulation, excoriation and lichenification) scores, Visual Analog Scale pruritus score, Patient‐Oriented Eczema Measure score, and percentage of affected body surface area over the 4‐week study. Topical OPA‐15406 twice daily for 4 weeks was considered a safe and effective treatment option in this phase 2 study in pediatric patients with atopic dermatitis, and phase 3 development is currently ongoing.