A Study to Assess the Tolerability of a Single Dose of STX107 in Adults With Fragile X Syndrome

A Randomized, Double-Blind, Placebo-Controlled Study to Assess the Safety, Tolerability, Pharmacokinetics and Pharmacodynamics of a Single Dose of STX107 in Adults With Fragile X Syndrome

The study will consist of a Screening period (up to 14 days), a Treatment period, and a Follow-Up period. Sixteen subjects will be enrolled into two sequential dose cohorts - 10 or 30 mg (or matching placebo) across four study centers.

Inclusion Criteria:

• Male subjects 18 to 50 years of age, inclusive.
• Molecular documentation of the full fragile X mutation.

Exclusion Criteria:

• Subjects with a history of seizure disorder who are, in the opinion of the Investigator and Medical Monitor, not currently considered to be well controlled.
• Subjects currently being treated with psychoactive medications (including stimulants and anxiolytics).
• Subjects with any condition, including alcohol and drug abuse, which might interfere with the conduct of the study, confound interpretation of the study results, or endanger their own well-being. 4. Subjects who plan to initiate or change pharmacologic or non-pharmacologic interventions during the course of the study.
• Subjects who, in the Investigator's opinion, might not be suitable for the study