Targeting the Neurobiology of RRB in Autism Using N-acetylcysteine: Single-dose

Inclusion Criteria:

• children between 3 years and 12 years 11 months at the time of consent

• diagnosis of Autism Spectrum Disorder confirmed with the Autism DiagnosticInterview-Revised (ADI-R) and the Autism Diagnostic Observation Schedule-2 (ADOS-2),or Brief Observation of Symptoms of Autism (BOSA), or Childhood Autism Rating Scale-Second Edition (CARS-2).

• at least moderate Restricted and Repetitive Behaviors severity defined by aChildren's Yale-Brown Obsessive Compulsive Scale for children with autism spectrumdisorder score ≥ 11,

• physical development indicative of prepubescence as defined by the criteria forTanner Stage 1,

• medically stable,

• passes MR safety screening (e.g., no metal in the body).

Exclusion Criteria:

• presence of known genetic abnormalities associated with Autism Spectrum Disorder (e.g. Fragile X),

• current or life-time diagnosis of severe psychiatric disorder (e.g., schizophrenia),

• presence of significant medical problems that would interfere with participation,

• the inability of at least one caregiver to speak/read English to a sufficient levelto complete study requirements and materials,

• individuals taking antioxidant agents and glutathione prodrugs, or

• the inability/unwillingness to swallow an agent during the screening visit.