AB-2004 in Treatment of Irritability Associated With Autism Spectrum Disorder (ASD)

Key Inclusion Criteria: * Clinically diagnosed, documented ASD (Diagnostic and Statistical Manual of Mental Disorders \[DSM-5\] criteria) * Aberrant Behavior Checklist - Irritability (ABC-I) score ≥18 at the Screening Period * Clinical Global Impression - Severity (CGI-S) scale score ≥4 at the Screening Period Key Exclusion Criteria: * Use of an oral, injected, or inhaled antibiotic within 30 days prior to screening. Prophylactic oral antibiotic use of no more than 1 dose will be permitted * Current use of an oral controlled or extended-release medication * Have a comorbid major psychiatric condition (eg, schizophrenia or bipolar disorder) at screening that in the opinion of the Investigator may interfere with the subject's ability to complete study procedures/comply with study requirements * Current use of antipsychotics (eg, aripiprazole or risperidone)