A 12-Week Placebo-Controlled Study to Investigate the Efficacy, Safety, and Tolerability of RO7017773 in Participants Aged 15-45 Years With Autism Spectrum Disorder (ASD)

Inclusion Criteria

1. Male and female participants with Autism Spectrum Disorder according to Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5)
2. Wechsler Abbreviated Scale of Intelligence (WASI-II) >/= 50 at screening or within the last 12 months prior to screening
3. ASD or Autism diagnosis confirmed by Autism Diagnostic Observation Schedule (ADOS-2)
4. Body mass index within the range of 18.5 to 40 kg/m2
5. Female Participants: is eligible if she is not pregnant, not breastfeeding, and women of childbearing potential (WOCBP), who agree to remain abstinent or use contraceptive methods that result in a failure rate of < 1% per year during the treatment period and for at least 28 days after the last dose of study drug
6. Language, hearing, and vision compatible with the study measurements as judged by the Investigator
7. Allowed existing treatment regimens should be stable for 8 weeks prior to screening. Investigator expects stability of these treatments and behavioral interventions for the duration of the study
8. In the Investigator's opinion, able to participate and deemed appropriate for participation in the study, capable of following the study SoA and able to comply with the study restrictions
9. In the Investigator's opinion, participation in the study or discontinuation of prohibited medication will not pose undue risks

Exclusion Criteria

Neurologic/Psychiatric Conditions:

1. Non-verbal individuals
2. Presence of chromosome 15q11.2 q13.1 duplication syndrome (Dup15q syndrome), known "syndromic" forms of ASD (confirmed per genetic results available at screening): fragile X syndrome, Prader Willi syndrome, Rett's syndrome, tuberous sclerosis, and Angelman syndrome, as well as genetic alterations strongly associated with ASD per genetic results available at screening affecting the following genes: CHD8, ANDP, SHANK3
3. Medical history of alcohol and/or substance abuse/dependence in the last 12 months or positive test for drugs of abuse at screening
4. Initiation of a major change in psychosocial intervention within 6 weeks prior to screening. Minor changes in ongoing treatment are not considered major changes
5. Clinically significant psychiatric and/or neurological disorder that may interfere with the safety or efficacy endpoints
6. Risk of suicidal behavior in the opinion of a certified clinician or as evidenced by a "yes" to questions 4 and/or 5 of Columbia-Suicide-Severity Rating Scale (C-SSRS) taken at screening and baseline with respect to the last 12 months, or any suicide attempt in the past 5 years
7. Unstable epilepsy/seizure disorder within the past 6 months or changes in anticonvulsive therapy within the last 6 months

Other Conditions:

1. Medical history of malignancy if not considered cured or if occurred within the last 3 years with the exception of fully excised non-melanoma skin cancers or in-situ carcinoma of the cervix that has been successfully treated
2. Concomitant disease, condition or treatment which would either interfere with the conduct of the study or pose an unacceptable risk to the participant in the opinion of the Investigator Prior/Concomitant Therapy
3. Use of prohibited medications or herbal remedies within 6 weeks or 5 half-lives (t1/2) prior to randomization

Prior/Concurrent Clinical Study Experience:

1. Donation or loss of blood over 500 mL in adults and 250 mL in adolescents within 3 months prior to randomization
2. Participation in an investigational drug study within 1 month or 5 times the t1/2 of the investigational molecule prior to randomization or participation in a study testing an investigational medical device within 1 month prior to randomization or if the device is still active Diagnostic Assessments
3. Confirmed clinically significant abnormality in hematological, chemistry or coagulation laboratory parameters
4. Positive test result at screening for hepatitis B surface antigen, hepatitis C virus (HCV, untreated), or human immunodeficiency virus (HIV)-1 and -2. HCV participants who have been successfully treated and who test negative for HCV RNA, may be considered eligible for entry into the study

Other Exculsions:

Uncorrected hypokalemia or hypomagnesaemia