Serum thymus and activation-regulated chemokine dynamics by asthma comorbidity despite similar clinical improvement in children with severe atopic dermatitis treated with dupilumab: a 52-week prospective study

Background: Asthma comorbidity may reflect the heterogeneity of type 2 inflammation in children with severe atopic dermatitis (AD). However, its impact on long-term clinical and biomarker trajectories during dupilumab treatment remains unclear. Objective: To investigate whether asthma comorbidity influences 52-week clinical and biomarker trajectories in children with severe AD treated with dupilumab. Methods: In this 52-week prospective study, 16 children (6–11 years) with severe AD (Eczema Area and Severity Index [EASI] ≥ 21) were stratified by asthma status: AD + asthma (n = 7) and AD-only (n = 9). The primary endpoint was the longitudinal EASI trajectory assessed by linear mixed-effects models. Serum thymus and activation-regulated chemokine (TARC) dynamics were analyzed as a key secondary endpoint. Exploratory analyses evaluated associations between baseline TARC and early treatment response. Results: Both groups demonstrated marked and sustained clinical improvement. While the AD + asthma group showed numerically faster early EASI improvement (week 0–4), trajectories converged by week 8 and remained similar thereafter (group × time interaction P = 0.68). By week 52, median EASI scores were low in both groups (1.9 vs 3.1). In contrast, serum TARC showed differing observed temporal patterns, with lower postbaseline levels in the AD + asthma group (interaction nominal P = 0.041). Exploratory analyses suggested a possible association between higher baseline TARC and early clinical improvement, although estimates were imprecise and require validation in larger cohorts. Conclusion: Dupilumab provided sustained clinical benefit irrespective of asthma comorbidity. Apparent differences in serum TARC dynamics despite comparable clinical outcomes are consistent with potential heterogeneity in biomarker responses. These findings are exploratory and hypothesis-generating, warranting validation in larger, adequately powered studies.