Autism Spectrum DisorderPhase 2/3NCT05664789
Targeting the Neurobiology of RRB in Autism Using N-acetylcysteine: Trial
A Phase 2/3 study testing N acetyl cysteine in people with Autism Spectrum Disorder, run by Stanford University at 1 site in United States.
Trial summary
The goal of this study is to target the neurobiology of restricted and repetitive behaviors in children with autism spectrum disorder using N-acetylcysteine (NAC), a well-tolerated nutritional supplement that has shown promise for reducing symptom severity in recent small-scale trials. Read more about this study
- Who is it for?
- Ages 3 to 12 years
- Conditions the study is for
- Autism Spectrum Disorder
- What is being tested?
- N acetyl cysteine
- Could I receive a placebo?
- Yes, some participants may receive a placebo
- How many people
- 144 participants
- Where
- 1 siteUnited States
- Study dates
- 26 Apr 2023to 31 Jul 2028
- Phase
- Phase 2/3
- Are there results?
- Not yet: the study is under way
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 3 to 12 years
- All sexes
- No healthy volunteers
- Child
Who may be able to join
- children between 3 years and 12 years 11 months
- diagnosis of autism spectrum disorder confirmed with the Autism Diagnostic Interview- Revised and the Autism Diagnostic Observation Schedule-2, Brief Observation of Symptoms of Autism, or Childhood Autism Rating Scale
- at least moderate severity of restricted and repetitive behaviors defined by a Children's Yale-Brown Obsessive Compulsive Scale for Autism Spectrum Disorder score ≥ 11
- physical development indicative of prepubescence as defined by criteria for Tanner Stage 1
- if home address is within 300 miles of the primary study site, participants must pass MR safety screening (e.g., no metal in the body) and attempt baseline neuroimaging (MRI or EEG), otherwise baseline neuroimaging is not required for participation
- have stable medication regimens (≥ 30 days) and psychosocial treatments (≥ 60 days) prior to randomization with no anticipated changes during the trial
Who cannot join
- presence of known genetic abnormalities associated with ASD (e.g. Fragile X)
- current or life-time diagnosis of severe psychiatric disorder (e.g., schizophrenia)
- presence of significant medical problems
- the inability of at least one caregiver to speak and read English to a sufficient level
- participants taking glutathione agents/prodrugs
- history of any adverse effects to glutathione agents/prodrugs
- the inability to drink a sample study compound dissolved in liquid
Trial locations and contacts
1 site in 1 country. Contact the study team or a site near you to ask about taking part.
United States1 site, 1 recruiting
- Recruiting
Department of Psychiatry and Behavioral Sciences
Palo Alto, California, 94304
Ramy Chebbo, (650)723-7845, autismresearch@stanford.edu
About this study
Official title: Targeting the Neurobiology of Restricted and Repetitive Behaviors in Children With Autism Using N-acetylcysteine: A Randomized, Controlled Trial
The goal of this study is to target the neurobiology of restricted and repetitive behaviors in children with autism spectrum disorder using N-acetylcysteine (NAC), a well-tolerated nutritional supplement that has shown promise for reducing symptom severity in recent small-scale trials. The findings from this research will shed light on the mechanisms of action underlying the clinical benefits of NAC and the effects of NAC on altering restricted and repetitive behavior symptom severity in children with autism spectrum disorder. This is a 12-week double-blind, randomized, placebo-controlled trial of NAC.
- Conditions
- Autism Spectrum Disorder
- Being tested
- N acetyl cysteine, Placebo
- Keywords
- Magnetic resonance imaging, N-acetyl cysteine, Restricted and repetitive behaviors, Electroencephalography
- Medical subject headings
- Autism Spectrum Disorder
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
N acetyl cysteineDrug
N-acetylcysteine (NAC) is an over-the-counter dietary supplement that is relatively well tolerated and exhibits minimal side effects, even at high dosages. N
PlaceboDrug
matched placebo
| Study group | Role | What they receive |
|---|---|---|
| N-acetylcysteine | Active comparator | 12 week administration of active study compound Receives: Drug: N acetyl cysteine |
| Placebo | Placebo comparator | 12 week administration of matched placebo Receives: Drug: Placebo |
What is being measured
The primary outcome is the main question the study is designed to answer.
Change in Children's Yale Brown-Obsessive Compulsive Scale for Autism Spectrum Disorder (CYBOCS-ASD) at 12 weeks
Severity of restricted and repetitive behaviors, higher scores indicate more severe behaviors
Measured: Screening and week 12
Change in Glutamatergic neurometabolites at 12 weeks
Glu and Glx measured by magnetic resonance imaging
Measured: Baseline and week 12
Secondary outcomes (2)
Change in Restricted and Repetitive Behavior Scale Revised (RBS-R) at 12 weeks
Severity of restricted and repetitive behaviors, higher scores indicate more severe behaviors
Measured: Baseline and week 12
Change in Gamma band activity at 12 weeks
Electrical activity between 30-48 Hz measured by electroencephalography
Measured: Baseline and week 12
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted27 Dec 2022
- Study start26 Apr 2023
- Primary completion31 Jan 2028 (estimated)
- Study completion31 Jul 2028 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Autism Spectrum DisorderStudies of the same condition, open and under way.
- More trials run by Stanford UniversityThe sponsor's other registered studies.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase 2/3
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Model description
- Double-blind, randomized, placebo-controlled trial 2 arms, N-acetylcysteine and placebo
- Masking
- Quadruple blind
- Who is masked
- Participant, Care provider, Investigator, Outcomes assessor
- Enrolment
- 144 participants (estimated)
Sponsor and investigators
- Lead sponsor
- Stanford University
- Sponsor type
- University, hospital or other
- Collaborators
- Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD)
- Responsible party
- Principal investigator, John Patrick Hegarty, Stanford University
- Investigators
- John Hegarty, PhD, Principal investigator, Stanford University
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT05664789
- Sponsor's protocol ID
- IRB-68353
- Other IDs
- 4R00HD101702-03
- Status last verified
- May 2026
- First submitted
- 7 Dec 2022
- Last updated
- 15 May 2026
- Results posted
- No
- Data monitoring committee
- Yes
- FDA-regulated drug
- Yes
- FDA-regulated device
- No
- Individual data sharing
- Yes: De-Identified data will be shared with the National Database for Autism Research (NDAR)
Study at a glance
From the registry record, last updated by the sponsor on 15 May 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Targeting the Neurobiology of Restricted and Repetitive Behaviors in Children With Autism Using N-acetylcysteine: A Randomized, Controlled Trial
- ClinicalTrials.gov ID
- NCT05664789
- Acronym / sponsor ID
- IRB-68353
- Conditions
- Autism Spectrum Disorder
- Keywords
- Magnetic resonance imaging, N-acetyl cysteine, Restricted and repetitive behaviors, Electroencephalography
- Phase
- Phase 2/3
- Study type
- Interventional
- Recruitment status
- Recruiting
- Enrolment
- 144 participants (estimated)
- Lead sponsor
- Stanford UniversityUniversity, hospital or other
- Collaborators
- Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD)
- Study start
- 26 Apr 2023 (actual)
- Primary completion
- 31 Jan 2028 (estimated)
- Study completion
- 31 Jul 2028 (estimated)
- First posted
- 27 Dec 2022 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
The goal of this study is to target the neurobiology of restricted and repetitive behaviors in children with autism spectrum disorder using N-acetylcysteine (NAC), a well-tolerated nutritional supplement that has shown promise for reducing symptom severity in recent small-scale trials. The findings from this research will shed light on the mechanisms of action underlying the clinical benefits of NAC and the effects of NAC on altering restricted and repetitive behavior symptom severity in children with autism spectrum disorder. This is a 12-week double-blind, randomized, placebo-controlled trial of NAC.
Study design
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- Quadruple blind (participant, care provider, investigator, outcomes assessor)
- Number of arms
- 2
- Model description
- Double-blind, randomized, placebo-controlled trial 2 arms, N-acetylcysteine and placebo
| Arm | Type | Receives |
|---|---|---|
| N-acetylcysteine | Active comparator | Drug: N acetyl cysteine12 week administration of active study compound |
| Placebo | Placebo comparator | Drug: Placebo12 week administration of matched placebo |
Who may qualify
- Ages
- 3 to 12 years
- Sex
- All
- Healthy volunteers
- Not accepted
- Age groups
- Child
Key inclusion criteria (6 listed)
- children between 3 years and 12 years 11 months
- diagnosis of autism spectrum disorder confirmed with the Autism Diagnostic Interview- Revised and the Autism Diagnostic Observation Schedule-2, Brief Observation of Symptoms of Autism, or Childhood Autism Rating Scale
- at least moderate severity of restricted and repetitive behaviors defined by a Children's Yale-Brown Obsessive Compulsive Scale for Autism Spectrum Disorder score ≥ 11
- physical development indicative of prepubescence as defined by criteria for Tanner Stage 1
- if home address is within 300 miles of the primary study site, participants must pass MR safety screening (e.g., no metal in the body) and attempt baseline neuroimaging (MRI or EEG), otherwise baseline neuroimaging is not required for participation
Key exclusion criteria (7 listed)
- presence of known genetic abnormalities associated with ASD (e.g. Fragile X)
- current or life-time diagnosis of severe psychiatric disorder (e.g., schizophrenia)
- presence of significant medical problems
- the inability of at least one caregiver to speak and read English to a sufficient level
- participants taking glutathione agents/prodrugs
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| N acetyl cysteineN-acetylcysteine (NAC) is an over-the-counter dietary supplement that is relatively well tolerated and exhibits minimal side effects, even at high dosages. N | Drug | N-acetylcysteine |
| Placebomatched placebo | Drug | Placebo |
Primary outcome
Change in Children's Yale Brown-Obsessive Compulsive Scale for Autism Spectrum Disorder (CYBOCS-ASD) at 12 weeks
Time frame: Screening and week 12
Severity of restricted and repetitive behaviors, higher scores indicate more severe behaviors
Change in Glutamatergic neurometabolites at 12 weeks
Time frame: Baseline and week 12
Glu and Glx measured by magnetic resonance imaging
2 secondary outcomes
Change in Restricted and Repetitive Behavior Scale Revised (RBS-R) at 12 weeks
Time frame: Baseline and week 12
Change in Gamma band activity at 12 weeks
Time frame: Baseline and week 12
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 15 May 2026.
- Individual participant dataSharing planned: Yes. De-Identified data will be shared with the National Database for Autism Research (NDAR)
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part.
John Hegarty, PhD principal investigator
Stanford University
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A Phase 2/3 study testing N acetyl cysteine in people with Autism Spectrum Disorder, run by Stanford University at 1 site in United States.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 6 inclusion and 7 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: looking for participants now, as of the sponsor's last update on 15 May 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in United States. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. Some participants in this study may receive a placebo. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
What does this combined phase mean?
Phase 2 studies give the treatment to a larger group to see whether it has the intended effect and to keep checking safety.
Phase 3 studies compare the treatment with the current standard treatment or a placebo in a large group, to confirm how well it works and watch for side effects.
Not every study follows the same path, and some studies (observational studies, device studies) have no phase.
Are results available for this study?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
Contact Ramy Chebbo ((650)723-7845, autismresearch@stanford.edu), or a site near the patient. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Change in Children's Yale Brown-Obsessive Compulsive Scale for Autism Spectrum Disorder (CYBOCS-ASD) at 12 weeks (time frame: Screening and week 12). The study lists 2 primary outcomes in all. It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 15 May 2026.