Time of Day of Biological Treatment Administration and Outcomes in Atopic Dermatitis: Results from a Preliminary Retrospective Study

<u><b><i></i></b></u> <u><b><i>Background:</i></b></u> Growing evidence on chronotherapy supports administering treatments according to endogenous biological rhythms. <u><b><i>Objectives:</i></b></u> To evaluate whether the administration time of dupilumab affects its effectiveness in patients with atopic dermatitis (AD), by virtue of the circadian oscillations of immune system activity. <u><b><i>Methods:</i></b></u> This retrospective study included all adult patients with AD treated with dupilumab from January 2020 to January 2024 at our unit. Data recorded at baseline (T0) and at the 16-week-treatment visit (T16) included itch severity, sleep disturbance, Eczema Area and Severity Index, Patient-Oriented Eczema Measure, Dermatology Life Quality Index, and immunoglobulin E levels. Therapeutic response was compared between two groups, based on injection time, that is, between 12:00 a.m. and 12:00 p.m. versus between 12:00 p.m. and 12:00 a.m. <u><b><i>Results:</i></b></u> Fifty-three patients were included, of whom 21 took dupilumab between 12:00 a.m. and 12:00 p.m. and 32 between 12:00 p.m. and 12:00 a.m. All clinical parameters improved from T0 to T16, without significant differences between groups. However, there was a greater improvement in these parameters in subjects taking dupilumab between 12:00 a.m. and 12:00 p.m., compared with the others. <u><b><i>Conclusions:</i></b></u> These preliminary results suggest a difference in therapeutic response to dupilumab based on the administration time, leading to potential optimization of its efficacy. Further studies on larger samples are needed.