A Study to Investigate the Efficacy and Safety of Balovaptan (RO5285119) in Participants With Autism Spectrum Disorder (ASD)

Inclusion Criteria:

- Fluent in English

- Diagnostic and Statistical Manual of Mental Disorders, 5th Edition (DSM-5) criteria
for ASD or International Statistical Classification of Diseases and Related Health
Problems, 10th revision (ICD10) criteria for Autism diagnosis confirmed by Autism
Diagnostic Observational Schedule (ADOS-2) criteria

- Social Responsiveness Scale, second edition (SRS-2) (T-score) >= 66

- Clinical Global Impressions of Severity (CGI-S) >= 4 (moderately ill) at screening

- IQ >= 70 as assessed by Wechsler Abbreviated Scale of Intelligence Scale: Second
Edition (WASI-II) or Wechsler Preschool and Primary Scale of Intelligence: Fourth
Edition (WPPSI-IV) intelligence test

- Language, hearing, and vision compatible with the study measurements as judged by the
investigator

Inclusion Criteria for the OLE:

- Have completed the blinded treatment phase of the study OR were required to stop
dosing at or before Week 8

- Have no adverse events that would prohibit starting the OLE

Exclusion Criteria:

- Initiation of a major change in psychosocial intervention (including investigational)
within 4 weeks prior to screening

- Unstable or uncontrolled clinically significant psychiatric and/or neurological
disorder that may interfere with the safety or efficacy endpoints

- Known personal or family history of cerebral aneurysm

- Risk of suicidal behavior

- Seizure within the past 6 months

- Medical history of alcohol or substance abuse/dependence

- Concurrent cardio-vascular disease not considered well controlled by the Investigator

- Clinically significant abnormality on electrocardiogram at screening

- Concomitant disease or condition (pulmonary, gastro-intestinal, hepatic, renal,
metabolic, immunological system, or obesity that could interfere with the conduct of
the study

- Evidence for current gastro-intestinal bleeding, e.g., active stomach ulcer disease

- History of coagulopathies, bleeding disorders, or blood dyscrasias

- Positive serology for hepatitis B (HBV), hepatitis C (HCV), human immunodeficiency
virus (HIV) 1, or HIV 2

- Confirmed clinically significant abnormality in parameters of hematology, clinical
chemistry, coagulation, or urinalysis

- Medical history of malignancy if not considered cured

- Participation in an investigational drug study within 90 days or 5 times the half-life
of the investigational molecule (whichever is longer) prior to randomization

- Loss of blood over 250 milliliters within three months prior to screening

- Allowed medications have not been stable since 4 weeks before screening, and allowed
medications for treatment of epilepsy have not been stable since 3 months before
screening

- Use of prohibited medications within 2 weeks prior to screening visit or 5 times the
half-life prior to randomization (whichever is longer)