Fragile X syndrome is the most common monogenetic form of autism. It results from an inherited mutation in the X chromosome that causes silencing of the fragile X mental retardation 1 (FMR1) gene and loss of FMR1 protein expression, which significantly disrupts neuronal function.  Fragile X syndrome is typically diagnosed at 2 to 3 years based on symptoms and confirmed by genetic analysis—well after significant neuronal impairment has occurred. In addition to core Fragile X symptoms such as repetitive stereotypical behaviors, deficits in social functioning, anxiety and cognitive impairment; there may be additional symptoms appearing in Fragile X patients related to attention deficits, hyperactivity or psychosis. Hypersensitivity to sensory stimuli and increased seizure potential also may be evident.

An array of symptoms can appear:
There are currently no approved drugs for treating the core Fragile X symptoms. Depending on the patient, anti-anxiety agents or SSRIs can mitigate some of the behaviors that accompany Fragile X syndrome; however, limited efficacy may be achieved and side effects are a frequent issue.

Drugs that effectively treat Fragile X syndrome represent a major unmet need for afflicted children and older patients.