Real-World Effectiveness, Treatment Course, and Safety of Tapinarof Cream 1% for Atopic Dermatitis and Plaque Psoriasis in Japan.

BACKGROUND: Tapinarof cream 1%, a non-steroidal topical aryl hydrocarbon receptor-modulating agent, is approved in Japan for atopic dermatitis (AD) and plaque psoriasis. Real-world data on longitudinal outcomes, treatment continuation, interruption and restart, and adverse-event timing are limited. METHODS: This single-center retrospective study included patients newly prescribed tapinarof cream 1% from November 2024 to July 24, 2025. The full analysis set comprised 37 AD and 58 plaque psoriasis patients. Primary endpoints were Eczema Area and Severity Index 50% improvement (EASI50) at week 8 for AD and Psoriasis Area and Severity Index 75% improvement (PASI75) at week 12 for psoriasis. Observed-case and non-responder imputation (NRI) analyses were reported. RESULTS: In AD, week-8 EASI50 was achieved by 12/24 evaluable patients (50.0%) and 12/37 under NRI (32.4%). Mean EASI decreased from 5.94 at baseline to 2.56 at week 8 and 0.83 at week 52. Week-52 EASI was available for 13/37 overall (13/27 with ascertainable status at the data cutoff). In psoriasis, week-12 PASI75 was achieved by 15/33 evaluable patients (45.5%) and 15/58 under NRI (25.9%). Mean PASI decreased from 2.95 at baseline to 1.18 at week 12 and 0.43 at week 52. Week-52 PASI was available for 25/58 overall (25/49 with ascertainable status at the data cutoff); long-term summaries were observed-case and potentially responder-enriched. Any adverse event was recorded in 11/37 AD patients and 12/58 psoriasis patients. Median headache onset was 8 h in AD and 1.8 days in psoriasis. No serious drug-related adverse event was recorded. No pigmentary change was documented; however, without standardized colorimetry or photography, its absence cannot be confirmed. CONCLUSION: Tapinarof-containing treatment was associated with clinically meaningful improvement in AD and plaque psoriasis in routine practice, although frequent concomitant therapy, observed-case long-term analyses, and retrospective ascertainment limit causal and safety inferences.