This study will investigate whether CX516 can improve attention, memory, language, or behavior in adults with Fragile X Syndrome and/or Autism.

CX516 is an AMPAKINE® compound. AMPAKINE compounds enhance synaptic strength. There is evidence to suggest that the synapses in the brain of an individual with fragile X syndrome are immature and abnormal. It is possible CX516 may partially correct this synaptic transmission defect and lead to improvement in cognitive and behavioral functioning.

There is also reason to believe that these changes caused by CX516 could be helpful in managing cognitive and behavioral symptoms in patients with autistic disorder.

Involvement for each participant will last 28 days. Participants will be given study medication, a physical exam, and a variety of cognitive assessment tests to study potential drug effectiveness at improving disease symptoms.

Inclusion criteria:

Fragile X group

• DNA-based diagnosis of Fragile X syndrome

Autism group

• Documented diagnosis with ADOS; ADI-R; CARS and GARS

Both groups

• 18-50 years
• Measured IQ below 85
• Measured IQ >20
• Mental age >30 months
• Stable medication regimen for past 8 weeks
• Normal hearing
• Vision corrected to at least 20/50
• All females of childbearing age must have a negative pregnancy test at enrollment

Exclusion criteria:

• Recent history of seizure, epilepsy, or blackouts
• Unresolved medical issue impacting performance
• Behavioral dysfunction to the point that subject cannot cooperate for testing
• History of drug-induced neutropenia
• Uncontrolled hypertension