Siolta Therapeutics Reports Positive Phase 2 Results from the ADORED Study

STMC-103H exhibited 64% reduction in the risk of atopic dermatitis in subjects who completed one year of treatment with strong and consistent effects across multiple efficacy endpoints and was safe and well-tolerated

SAN CARLOS, Calif., Nov. 17, 2025 /PRNewswire/ -- Siolta Therapeutics, a clinical-stage biotech company developing first-in-class live biotherapeutic products (LBPs), today announced positive top-line results from the Phase 2 ADORED study (Allergic Disease Onset pREvention stuDy) of STMC-103H, its lead investigational oral microbial therapy. STMC-103H is being developed for the prevention of atopic diseases (atopic dermatitis, food allergy, asthma, allergic rhinitis/ conjunctivitis) in infants with an immediate family history of atopic disease. The trial assessed safety and efficacy as measured by the ability of STMC-103H to reduce the incidence of atopic disease in at-risk infants compared with placebo over the two-year study period. Infants who completed the full year of treatment demonstrated a clinically meaningful reduction in the risk of developing atopic dermatitis and food allergy at the end of the one-year treatment period in the per protocol analysis, accompanied by consistent improvements across additional secondary measures. STMC-103H was safe and well tolerated in the study. These results suggest that STMC-103H may protect against atopic disease development in at-risk infants who complete the treatment as planned, supporting further development of this novel microbiome-targeted therapy.

"Type 1 allergic diseases such as atopic dermatitis, food allergy and asthma represent a growing global health concern" said Dr Michael O'Sullivan, Consultant Clinical Immunologist and Allergist at Fiona Stanley Hospital and principal investigator of the ADORED study. "These data provide compelling evidence that microbiome-based therapeutics like STMC-103H, may offer a novel and effective strategy for prevention of these allergic diseases."

Key Findings:

• The Phase 2 randomized, double-blind, placebo-controlled proof-of-concept trial enrolled 238 newborns across 30 sites in the United States and Australia. Following the one-year treatment, subjects were followed for an additional one year without treatment. P-values reported below were unadjusted for multiplicity.
• Subjects who completed the full year of treatment with STMC-103H demonstrated a 64% reduction in the risk of developing physician-diagnosed atopic dermatitis compared to placebo at one year after initiation of treatment (23.3% vs. 43.1%; OR = 0.36; 90% CI 0.20-0.66; n=158; p = 0.005). When all randomized infants, including those who received less than 1 year of treatment, were included in the end-of-treatment analysis, the results did not reach statistical significance.
• STMC-103H showed consistent and clinically meaningful improvements across additional secondary endpoints at one year, including a 77% reduction in the risk of developing physician-diagnosed food allergy (4.7 vs. 16.7%; OR = 0.23; 90% CI 0.09-0.63, p=0.02), prolonged time to development of atopic dermatitis (p=0.01) and reduced total serum IgE (p=0.03) compared to placebo, in those subjects who completed treatment as planned.
• Subjects who completed at least 6 months of treatment with STMC-103H demonstrated a 53% reduction in the risk of developing atopic dermatitis compared to placebo at one year after initiation of treatment (p=0.02).   
• STMC-103H was well-tolerated with no differences between STMC-103H-treated and placebo groups at the end of the treatment period in the development of serious adverse events or adverse events of special interest
• End of study (Year 2) clinical outcome data will be finalized and reported in Q1 of 2026

"We are very excited to see such encouraging results of this first-in-class microbiome-based therapy in addressing this important unmet need in an at-risk population of infants," said Richard Shames, MD, Chief Medical Officer of Siolta Therapeutics. "Based on these data, we look forward to further engagement with the FDA to advance the STMC-103H development program".

Atopic diseases affect more than 20% of infants and children in the U.S. with higher observed rates in at-risk individuals with a familial incidence of atopic disease. Development of atopic disease can result in chronic and long-standing symptoms, impaired quality-of-life, and potentially severe comorbidities and complications including hospitalization and death.  The rising incidence of atopic disease represents a rapidly growing public health concern. There are currently no approved therapies that can reduce the development of these chronic and burdensome conditions, only treatments that manage symptoms after the disease has developed.

Siolta's novel investigational therapy, STMC-103H, represents a fundamentally new approach that aims to support the infant microbiome in a manner that promotes a healthy immune system in early life. STMC-103H contains a defined set of beneficial bacterial strains naturally found in healthy infants that are intended to work synergistically over the first year of life to prevent the development of atopic disease. In infants and children, the development of atopic disease typically follows a progression termed the "atopic march" which often begins with atopic dermatitis and food allergy followed by asthma and allergic rhinitis. STMC-103H aims to reduce immune dysregulation before symptoms appear, a potentially transformative strategy to mitigate the development and progression of multiple atopic diseases.

"I would like to thank everyone who made this groundbreaking study possible, most importantly the families and investigators for their participation in the trial," said Nikole Kimes, PhD, Co-Founder and Chief Executive Officer of Siolta Therapeutics. "By targeting the microbiome early in life, we aim to reprogram immune development to prevent allergic disease in childhood and beyond. These promising Phase 2 results represent a critical milestone for all of us seeking safe and effective options for preventing allergic disease."

Siolta expects to present the results of the ADORED study at an upcoming medical meeting and in a peer-reviewed journal.

About the ADORED study

The Phase 1b/ 2 ADORED study is a randomized, double-blind, placebo-controlled multi-center study designed to evaluate the safety/ tolerability, and preliminary efficacy of STMC-103H in reducing the incidence of Type 1 allergic diseases (including atopic dermatitis, food allergy, asthma, allergic rhinitis/ conjunctivitis) in at-risk newborns compared to placebo. The study was conducted in 3 parts: Parts A1 and A2 enrolled at-risk children (aged 1 year to <6 years) and infants (aged 28 days to <12 months) to evaluate safety and tolerability following 28 days of treatment with study drug (STMC-103H or placebo) and 28 days of follow-up. Part B enrolled newborns aged 0-14 days who were at-risk for the development of atopic disease based on a positive family history of atopic disease in a biological parent and/ or full sibling. Part B subjects were treated with STMC-103H or placebo (1:1 randomization) orally once daily for approximately one year (336 days) followed by a 336-day observational period off treatment.

The primary endpoints were the incidence of physician-diagnosed atopic dermatitis at day 336 (end of treatment) and safety/ tolerability. Adverse events, serious adverse events, adverse events of special interest, vital signs and clinical safety laboratories were monitored. Secondary efficacy endpoints included the incidence of any physician-diagnosed atopic diseases, including food allergy, asthma and allergic rhinitis, time to atopic dermatitis and wheezing illness development, severity of atopic dermatitis and wheezing illness, total serum IgE and sensitization to environmental and food allergens at day 336 (end-of-treatment) and day 672 (end-of-study). The study can be found at clinicaltrials.gov under NCT05003804.

About STMC-103H

STMC-103H is Siolta's lead investigational LBP designed to restore immune-microbiome interactions in early life to mitigate the development of atopic disease. The product contains a defined consortium of commensal bacterial strains naturally found in healthy humans. STMC-103H is currently under clinical investigation, and its safety and efficacy have not been evaluated by any regulatory authority. Siolta has received Fast Track designation from the FDA for this program.

About Siolta Therapeutics

Siolta Therapeutics is a clinical-stage biotech company leveraging the human microbiome to prevent and treat immune-mediated diseases. Founded by leading scientists from the University of California, San Francisco, Siolta is advancing a pipeline of rationally designed LBPs with a focus on the maternal-infant axis. Learn more at www.sioltatherapeutics.com

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SOURCE Siolta Therapeutics