Subtype-Specific Efficacy of Topical Streptococcus Postbiotic Emollient in Adolescents and Adults With Atopic Dermatitis and Comorbid Allergies: A Post-hoc Analysis of a Randomized, Double-Blind, Vehicle-Controlled Trial.

Topical Streptococcus postbiotic emollient (Strain CX) has shown efficacy for mild-to-moderate atopic dermatitis (AD) in a previous study; however, treatment responses according to allergic comorbidity status have not yet been explored. We conducted a post hoc analysis to evaluate the differential therapeutic effects of Strain CX in patients with AD stratified by the presence or absence of allergic comorbidities. This post hoc analysis was derived from a randomized, double-blind, vehicle-controlled trial (Clinical Research Information Service of South Korea, KCT0007876). A total of 98 patients with mild-to-moderate AD were stratified into placebo (n = 33), AD without allergic comorbidities (n = 29), and AD with allergic comorbidities (n = 36) groups. The primary outcomes were the Investigator's Global Assessment (IGA) score and the proportions of participants achieving 25% or 50% improvement in the Eczema Area and Severity Index (EASI), assessed at weeks 4 and 8. The secondary outcomes included a range of skin-related clinical and molecular measures, along with additional evaluations of serum inflammatory and allergic biomarkers as laboratory measures in the per-protocol analysis set. At week 8, 55.2% (16/29) of participants in the AD without allergic comorbidities group achieved an IGA score of 0 or 1 with ≥ 1 point reduction, compared to 30.6% (11/36) in the AD with allergic comorbidities group (P = 0.0272). Both Strain CX intervention groups showed significant improvements in skin parameters, including EASI, skin moisture, and transepidermal water loss. Notably, the AD with allergic comorbidities group solely exhibited significant reductions in systemic inflammatory markers, including sIL-2R (mean, -231.19; 95% confidence interval [CI], -378.82 to -83.57 pg/mL), CCL17 (-127.05; 95% CI, -251.80 to -2.31 pg/mL), and CCL22 (-578.40; 95% CI, -939.31 to -217.49 pg/mL). Clinical skin responses improved more in patients with AD without allergic comorbidities, while immunomodulatory benefits were observed in those with allergic comorbidities. These findings support patient stratification based on allergic comorbidity status for personalized Strain CX treatment strategies. Trial Registration: Clinical Research Information Service Identifier: KCT0007876.