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Fragile X SyndromePhase 2NCT06334419

Placebo-Controlled, Single-Dose Challenge Study of Gaboxadol in Adult Males With Fragile X Syndrome (FXS)

A Phase 2 study testing Gaboxadol in people with Fragile X Syndrome, run by Craig Erickson at 1 site in United States.

Completed

Finished. The study has ended and is not enrolling. Results may be posted on the official record.

Official record
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Trial summary

This is a single dose, placebo-controlled study. Male subjects aged 18 to 40 years (inclusive) with a diagnosis of FXS. Eligible subjects may enroll in this study comprised of two in home and two in clinic visits each 14 days apart, for a total of four visits. Read more about this study

Who is it for?
Ages 18 to 40 years, men only
Conditions the study is for
Fragile X Syndrome
What is being tested?
Gaboxadol
Type of treatment
Pill or oral medicine
Could I receive a placebo?
Yes, some participants may receive a placebo
How many people
10 participants
Where
1 siteUnited States
Study dates
29 Jan 2024to 24 Jun 2025
Phase
Phase 2
Are there results?
Yes, posted in the registrySummary in the doctors' view

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 18 to 40 years
  • Men only
  • No healthy volunteers
  • Adult

Who may be able to join

  • Subject consents to participate, or if they are not their own legal guardian, offers assent supported by legally authorized representative consent
  • Subject is willing and able to comply with the study procedures as specified in the protocol and to comply with the study drug administration. Caregiver also commits to the study requirements prior to any study-related procedures
  • Subject and caregiver are both able to understand the spoken national language clearly and caregiver can read and write to complete study assessments
  • Males age 18 to 40 years (inclusive)
  • Has FXS with molecular genetic confirmation of the full FMR1 mutation (>200 cysteine-guanine-guanine [CGG] repeats). May have been confirmed historically or at Screening
  • Is in general good health as deemed by the Investigator, determined by physical examination, medical history, and laboratory tests
  • If receiving serotonin-selective reuptake inhibitor (SSRI), serotonin-norepinephrine reuptake inhibitor (SNRI), or serotonin antagonist and reuptake inhibitor (SARI), is on a stable, well-tolerated dose for the previous 3 months with no further changes anticipated
  • Is not sexually active or can confirm at least one form of contraceptive

Who cannot join

  • Any chronic major medical comorbid condition deemed by the Investigator as presenting added risk to the subject, including but not limited to, refractory hypertension, kidney disease, or liver disease
  • Diagnosed with diabetes (Type 1 or II) or receiving any anti-diabetic medication
  • Unstable seizure disorder, defined by any seizure within 6 months prior to baseline visit and/or a change in any anti-convulsant drug dosing in the 60 days prior to study consent
  • Changes in psychotropic or anti-convulsant (where taken for reasons other than seizure control) drug treatment within 30 days prior to Screening
  • Significant changes in any educational, behavioral, and/or dietary interventions the month prior to Screening
  • Planned initiation of new, or modification of ongoing, interventions during the study
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  • Unable or unwilling to take oral medication (whole capsule, despite assistance with a spoonful of applesauce, yoghurt, or equivalent liquid food)
  • Consumption of liver enzyme inducers or inhibitors including and not limited to foods, medicines, herbal remedies and supplements three days prior to any Visit. Foods or beverages containing CYP3A4/5 inhibitors (e.g., grapefruit, pomegranate, pomelo, and star fruit) should be avoided before taking study medication and for up to 1 hour post dose throughout the study
  • Has abnormal baseline laboratory assessments including, but not limited to, alanine aminotransferase (ALT) or aspartate aminotransferase (AST) or total bilirubin >1.5 × the upper limit of normal (ULN), serum creatinine >1.5 x ULN or other clinically relevant laboratory abnormality
  • Has a clinically significant heart rate or blood pressure (BP) at Screening as judged by the Investigator
  • Has received an investigational drug in any prior clinical study within 30 days or 5 half-lives (whichever is longer) prior to Screening

Trial locations and contacts

1 site in 1 country.

United States1 site
  • Cincinnati Children's Hospital Medical Center

    Cincinnati, Ohio, 45229

Other trials in United States

About this study

This is a single dose, placebo-controlled study. Male subjects aged 18 to 40 years (inclusive) with a diagnosis of FXS. Eligible subjects may enroll in this study comprised of two in home and two in clinic visits each 14 days apart, for a total of four visits. Subjects will be given single dose gaboxadol (10 mg) or matched placebo at each of these visits to take orally. Thus, all enrolled subjects will receive placebo at home and in clinic and receive gaboxadol at home and in clinic in a blinded fashion.

Being tested
Gaboxadol, Placebo
Keywords
Fragile X, Fragile X Syndrome, FXS
Medical subject headings
Fragile X Syndrome

What participants receive

What participants receive. In a randomised study each person is assigned to one group by chance.

  • GaboxadolDrug

    Drug: Gaboxadol 10 mg as a single dose (two 5mg capsules)

  • PlaceboDrug

    Two placebo capsules

Study groups in NCT06334419
Study groupRoleWhat they receive
Placebo in lab, Gaboxadol in home, Gaboxadol in lab, Placebo in homeExperimentalIndividuals in this condition received Placebo in lab, Gaboxadol in home, Gaboxadol in lab, then Placebo in home.
Receives: Drug: Gaboxadol; Drug: Placebo
Gaboxadol in lab, Gaboxadol in home, Placebo in lab, Placebo in homeExperimentalIndividuals in this condition received Gaboxadol in lab, Gaboxadol in home, Placebo in lab, then Placebo in home.
Receives: Drug: Gaboxadol; Drug: Placebo
Placebo in lab, Placebo in home, Gaboxadol in lab, Gaboxadol in homeExperimentalIndividuals in this condition received Placebo in lab, Placebo in home, Gaboxadol in lab, then Gaboxadol in home.
Receives: Drug: Gaboxadol; Drug: Placebo
Gaboxadol in lab, Placebo in home, Placebo in lab, Gaboxadol in homeExperimentalIndividuals in this condition received Gaboxadol in lab, Placebo in home, Placebo in lab, then Gaboxadol in home.
Receives: Drug: Gaboxadol; Drug: Placebo

What is being measured

The primary outcome is the main question the study is designed to answer.

  1. Target Engagement of Gaboxadol Treatment on EEG Power

    Changes in EEG recordings with gaboxadol treatment (assessed at pre-dose, 60 minutes post-dose, average response across home and lab reported). compared with pre-dose on resting theta, alpha and gamma band absolute power. Absolute power measures reflect the median power averaged across 129 electrodes in μV²/Hz. Means are presented using the average of home and lab values.

    Measured: Pre-dose compared to 60 minutes post-dose on 4 study visits, up to day 42

  2. Target Engagement of Gaboxadol Treatment on Auditory Chirp

    Changes in EEG recordings with gaboxadol treatment (60-90 minutes post-dose compared with pre-dose on brain response to auditory chirp stimuli), as measured by intertrial phase coherence (ITC). Means are presented using the average of home and lab values.

    Measured: Pre-dose compared to 60 minutes post-dose on 4 study visits, up to day 42

Secondary outcomes (7)
  1. To Investigate the Feasibility of Home Research Visits and Procedures in Adult Males With FXS

    Quality and test-retest reliability of assessments performed at home compared with the hospital setting. This includes blood testing for Fragile X messenger ribonucleoprotein (FMRP: range of 0-40 picomolar) and eye-tracking of eye gaze to eye regions when viewing faces (range of value from 0 percent to 100 percent; higher values are associated with a neurotypical phenotype).

    Measured: Pre-dose, 60 minutes post-dose

  2. To Investigate the Feasibility of High Density EEG Recording at Home in Adult Males With FXS

    This endpoint examined the reliability of pre-dose resting-state EEG absolute power estimates between in-lab and in-home assessments using intraclass correlation (ICC). ICCs were calculated separately for 129 electrodes using absolute power estimates (μV²/Hz). The reported ICC represents the mean ICC across electrodes, with the standard deviation reflecting variability in ICC values across electrodes. whole-head, pre-dose resting state EEG power estimates from data collected in-lab vs in-home using intraclass correlation (ICC).

    Measured: Pre-dose, across four sessions (2 in-lab, 2 in-home), up to day 42

  3. To Potentially Explore the Pharmacokinetics of Gaboxadol Treatment in Single-dose Trial Design

    PK profile (the level of gaboxadol in human plasma) will be obtained at 60 +/- 10 minutes post-dose only).

    Measured: Sixty minutes post-dose on 4 study visits, up to day 42

  4. To Investigate the Effect of Gaboxadol Treatment on Neuropsychological Assessments

    Changes in cognitive and neuropsychological assessment measures with gaboxadol treatment (RBANS List Learning). During the RBANS List Learning subtests, participants listen to a list of 10 words and repeat back as many as they can remember four times, for a maximum score of 40. Change scores were calculated by subtracting pre-dose words remembered from post-dose words remembered, with positive scores meaning an improvement in memory.

    Measured: Pre-dose compared to 60 minutes post-dose on 4 study visits, up to day 42

  5. To Investigate the Effect of Gaboxadol Treatment on Eye Tracking Assessments

    Change in eye tracking outcomes (60-90 minutes post-dose compared to pre-dose on percent viewing of social versus geometric scene

    Measured: Baseline compared to 60 minutes post-dose on 4 study visits, up to day 42

  6. To Investigate the Effect of Gaboxadol Treatment on Clinician-rated Measures

    Score on the Clinical Global Impressions - Improvement (CGI-I) scale, a clinician rating scale with "1" anchored to "very much improved" and "7" anchored to "very much worse."

    Measured: Post-dose on 4 study visits, up to day 42

  7. To Determine Whether FMRP Levels Predict Treatment Response

    Relationship between FMRP (Fragile X messenger ribonucleoprotein) level and degree of change (baseline/screen to post-dose) across measures

    Measured: Baseline compared to 60 minutes post-dose on 4 study visits, up to day 42

Timeline

From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.

  1. First posted28 Mar 2024
  2. Study start29 Jan 2024
  3. Primary completion13 May 2025
  4. Study completion24 Jun 2025

Resources

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
Primary purpose
Basic science
Allocation
Randomised
Intervention model
Crossover
Model description
This study was designed as a 2-intervention crossover, with all study participants receiving all possible interventions. These are placebo and Gaboxadol. Participants received a single dose of gaboxadol and a single dose of placebo in each of two locations (in-lab and in-home), for a total of four dosing occasions, with the first visit always occurring in-lab.
Masking
Quadruple blind
Who is masked
Participant, Care provider, Investigator, Outcomes assessor
Enrolment
10 participants (actual)
IDs, dates and publications
ClinicalTrials.gov ID
NCT06334419
Sponsor's protocol ID
2023-0795
Status last verified
Jul 2026
First submitted
8 Mar 2024
Last updated
30 Sep 2026
Data monitoring committee
Yes
FDA-regulated drug
Yes
FDA-regulated device
No

Publications

  • De Stefano LA, Kim H, Erickson CA, Schmitt LM, Dominick KC, Pedapati EV, Huckle R, Wilson R, McKinney WS, Reisinger DL, Nelson MN, Dapore AE, Horn PS, Miyakoshi M. Gaboxadol increases resting theta and alpha power without affecting evoked responses in fragile X syndrome in a home-based setting. J Neurodev Disord. 2026 May 8;18(1):36. doi: 10.1186/s11689-026-09700-5.

    PubMed 42104256

Questions about this trial

What is this clinical trial studying?

A Phase 2 study testing Gaboxadol in people with Fragile X Syndrome, run by Craig Erickson 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 8 inclusion and 11 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: finished, as of the sponsor's last update on 30 Sep 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. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.

What does this 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.

Not every study follows the same path, and some studies (observational studies, device studies) have no phase.

Are results available for this study?

Yes. Results are posted in the registry (first posted 30 Sep 2026). A summary is in the For doctors view, and the full results are on ClinicalTrials.gov.

How can a doctor refer a patient or contact the research team?

The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.

What does the primary outcome measure?

Target Engagement of Gaboxadol Treatment on EEG Power (time frame: Pre-dose compared to 60 minutes post-dose on 4 study visits, up to day 42). 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?

On the ClinicalTrials.gov record for NCT06334419, which also lists 1 linked publication.

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 30 Sep 2026; AzTrials last refreshed its copy on 8 Nov 2026.

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