Allergic Disease Onset Prevention Study

This is a Phase 1b/2, randomized, double-blind, multi-center study to evaluate the safety, tolerability, and preliminary clinical efficacy of STMC-103H in neonates and infants at risk for developing allergic disease (Type 1 hypersensitivity). Subjects will be enrolled in a three-part sequential approach. Participants in the safety-run portion of the study (Part A1: 1 year to \<6 years of age and A2: 1 month to \<12 months of age) will receive 28 days of treatment with STMC-103H or placebo, followed by 28 days of follow-up. A Data and Safety Monitoring Committee (DSMC) will review safety data after all patients in each part complete 28 days of therapy prior to enrolling the next part. After A2, Part B will enroll 224 patients for 336 days of treatment with STMC-103H or placebo, followed by 336 days of follow-up. Stool, blood, and optional samples will be collected in Parts A2 and part B. Primary safety endpoints are frequency, type and severity of Adverse Events (AEs) and Serious Adverse Events (SAEs), as well as findings on physical exams, vitals, and safety laboratories. The primary efficacy endpoint is incidence of physician-diagnosed atopic dermatitis at day 336.