The role of the gut microbiome in Fragile X syndrome (FXS) remains largely unexplored. The relationship between FXS in humans and gut microbiota has not yet been assessed. However, there are several preclinical research which emphasize the role of dysbiosis and/or probiotics in FXS animal models.

The primary objective of this clinical trial is to evaluate efficacy of probiotic mixture which contains Lactobacillus casei, Lactobacillus salivarius and Bifidobacterium breve, in children with Fragile X aged 3-18 years. Specifically, links between microbiome modifications by probiotic mixture and behavioral manifestations and brain processing (eye tracker, EEG analysis) will be assessed. Exploratory objects of this trial are analyses of microbiome composition and assessment of its alterations and modifications (by probiotic mixture) that may lead to clinical improvement and prediction which patients with FXS may be likely to benefit from probiotics treatment.

This is open label trial without masking, where each participant receives probiotic for 3 months (12 weeks). It will be single group assignment. The study plans to enroll 15 participants with FXS, aged 3-18 years, both sexes, during 1-year period and complete all study-related activities by January 2025. During the 3-month study period, subjects will attend three visits (screening/baseline, 6-week, and 3-month visits) to the Fragile X Clinic at the Special Hospital for Cerebral Palsy and Developmental Neurology, Belgrade, Serbia. The primary outcome measures will be Vineland Adaptive Behavior Scales–Third Edition (VABS-III) and eye tracking measures (social gaze and pupillometry). Exploratory endpoint will be microbiome analyses. Secondary outcome measures will be: CGI-S and CGI-I scores, ABC-CFX score, quality of life, sleep habits and EEG analyses.

The project team includes researchers in different scientific and medical fields, PhD student, medical doctors, psychologist, etc. The team is leaded by Prof. Dr. Dragana Protic, MD, PhD.