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

Targeting the Neurobiology of Restricted and Repetitive Behaviors in Children With Autism Using N-acetylcysteine: A Randomized, Controlled Trial

Targeting the Neurobiology of RRB in Autism Using N-acetylcysteine: Trial (NCT05664789) is a Phase 2 / Phase 3 interventional studying Autism Spectrum Disorder, sponsored by Stanford University. RECRUITING as of the most recent ClinicalTrials.gov update. Talk to your doctor before contacting the trial site.

About This 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.

What Stage of Research Is This?

Phase 2 trials evaluate whether a treatment actually works against Autism Spectrum Disorder and continue monitoring side effects. Phase 2 enrolls larger groups (typically 100–300 patients) and produces the first real efficacy signal. A successful Phase 2 readout is what unlocks the much larger Phase 3 confirmatory trials needed for FDA approval.

This trial is currently recruiting participants. The sponsor has registered the study with ClinicalTrials.gov as actively enrolling, which means new applicants who meet the eligibility criteria can be considered for screening. Trial status can change between updates — confirm current recruiting status with the study contact before traveling for a screening visit.

Target enrollment of 144 participants puts this in the typical range for a Phase 2-style efficacy study or a moderate Phase 3 trial in a focused Autism Spectrum Disorder subpopulation. At this scale, the study has enough statistical power to detect a clear treatment effect but is not the largest cohort in the field.

Who May Be Eligible (Plain English)

Who May Qualify: - 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 Should NOT Join This Trial: - 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 Always talk to your doctor about whether this trial is right for you.

These are translations of the protocol\'s inclusion and exclusion criteria, simplified for patients and caregivers. The original clinical text appears below. Eligibility is ultimately confirmed by the trial site\'s screening process — this summary is a starting point for a conversation with your doctor, not a final determination.

Original Eligibility Criteria

View original clinical language

Inclusion Criteria: * 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 Exclusion Criteria: * 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

Treatments Being Tested

DRUG

N acetyl cysteine

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

DRUG

Placebo

matched placebo

Locations (1)

Trial sites listed on ClinicalTrials.gov for this study. Site activation status can vary — confirm with the specific site before traveling for a screening visit.

Department of Psychiatry and Behavioral Sciences

Palo Alto, California, United States

How to Talk to Your Doctor About This Trial

Bring the printable summary of this trial — including the NCT ID (NCT05664789), the sponsor (Stanford University), and the key eligibility criteria — to your next appointment. Your doctor can review the inclusion and exclusion criteria against your medical history, lab values, and current treatments to assess whether you are likely to qualify. They can also help you weigh whether trial participation makes sense alongside your existing care plan.

Useful questions to walk through together: What does the trial protocol require beyond standard care? How long is the active treatment phase, and how long is follow-up? Are there study visits at sites I can reach? Who pays for the trial-specific procedures, and who pays for standard-of-care portions? See our 25 questions to ask about clinical trials guide for a more complete checklist.

Authoritative Sources

The official record for this trial lives on ClinicalTrials.gov — the federal registry maintained by the National Library of Medicine at NIH. For background on how this trial fits into the FDA approval pathway, see the FDA drug approval process. For oncology-specific guidance for patients considering trials, the National Cancer Institute publishes patient-oriented overviews. International trial registries are aggregated by the WHO ICTRP.

Frequently Asked Questions

What is the NCT05664789 clinical trial studying?

Who can participate in NCT05664789?

Eligibility for this trial depends on the specific inclusion and exclusion criteria set by the sponsor. The plain-English summary above translates the most important criteria into accessible language; the official clinical text is preserved in the collapsible section underneath. Whether you fit any specific trial is a medical decision your doctor needs to confirm — bring the trial information to your treating physician for a full review against your medical history.

How do I contact the trial site for NCT05664789?

Contact information registered with ClinicalTrials.gov is shown in the sidebar of this page. Before reaching out, confirm with your treating physician that this trial is appropriate for your situation. The trial site will then walk you through the screening process to determine final eligibility.

Is participating in a clinical trial safe?

Clinical trials in the United States are regulated by the FDA and overseen by Institutional Review Boards (IRBs) that review the protocol for safety. Risk varies by trial — Phase 1 studies test new treatments in humans for the first time, while Phase 3 trials use treatments that have already passed earlier safety screening. The informed consent document for any specific trial details the known risks and what to expect. Discuss those risks with your physician before deciding whether to participate.

Where can I verify the data on this page?

Every detail on this page comes directly from the ClinicalTrials.gov API. Click "View on ClinicalTrials.gov" in the sidebar to see the official, unmodified record. The federal record is always authoritative; this page is a structured presentation with a plain-English eligibility translation. For background on how clinical trials are regulated, see the FDA drug approval process documentation.

How This Page Is Built

Every field on this page is pulled directly from the ClinicalTrials.gov API v2 — no estimates, no proxies. The plain-English eligibility translation is generated from the original protocol text and reviewed for fidelity to the underlying clinical criteria. The original clinical text remains visible in the collapsible section above so users and clinicians can verify the translation. Read the full methodology for the data pipeline and known limitations.

Source: ClinicalTrials.gov API v2 record for NCT05664789. Maintained by the National Library of Medicine at NIH. Public domain. Cite as: "TrialFinderData. NCT05664789. Data: ClinicalTrials.gov."

Medical disclaimer: This page is informational, not medical advice. Talk to your doctor about whether a clinical trial is right for you.

Last updated 2026-05-08 · Data from ClinicalTrials.gov.