The purpose of this study is to assess the safety, tolerability and efficacy of oral OV101 (gaboxadol) in subjects with Fragile X syndrome.

Inclusion Criteria:

• Is male and 13 to 22 years old (inclusive) at the time of informed consent.
• Has a diagnosis of FXS with a confirmed FMR1 full mutation (≥200 CGG repeats).

Exclusion Criteria:

• Concomitant disease or condition that are clinically significant and would limit study participation
• Clinically significant lab abnormalities or vital signs at the time of screening
• History of uncontrollable seizure disorder or seizure episodes within 6 months of screening or change in the anticonvulsant pharmacotherapy in the past 3 months.
• Unable or does not have a caregiver able to comply with study requirements.
• Enrolled in any clinical trial within the 30 days before screening.

12 weeks

All adverse events collected as part of the study are reported in the Adverse Event module