Fragile X Syndrome (FXS) is one of the most common causes of intellectual disability. It is the result of the expansion of the trinucleotide CGG repeat (>200) in the fragile x messenger ribonucleoprotein 1 (FMR1) gene, leading to a deficiency or absence of the fragile X messenger ribonucleoprotein (FMRP). Many studies have found that there is a trend of IQdecline among FXS individuals around adolescent years. Recent studies also found that metformin rescues some of the cognitive deficits in FXS mouse models, and case reports show similar benefits in FXS individuals.

This suggests that metformin may have clinical value as a targeted treatment to slow IQ decline in FXS individuals. In this follow-up study, we are assessing pre- and post-metformin IQ scores among individuals with FXS after 1 year of treatment.