A Phase 2 interventional study of Rett-T and Placebo in Rett Syndrome, sponsored by Holland Bloorview Kids Rehabilitation Hospital. Recruiting at 1 site in Canada. Open to female participants aged 2 Years to 21 Years. Per ClinicalTrials.gov, last updated 2026-09-02.
Sponsored by Holland Bloorview Kids Rehabilitation Hospital · Phase 2, Interventional, and Treatment
This study will examine the potential efficacy and safety of Rett-T for core motor deficits of Rett syndrome, and will explore biological markers of safety and treatment response.
There are currently no available medicines shown to be effective for Rett syndrome. Numerous studies implicate mitochondrial dysfunction and oxidative stresses in the pathophysiology of Rett syndrome. Mitochondrial dysfunction has been reported in Rett patients, Rett mouse models and MECP2-deficient cells.
Collaborators have tested a combination of specific antioxidants known to enhance mitochondrial function in a cell and mouse model of Rett syndrome. The formulation normalized mitochondrial membrane potential in MECP2 neurons, and MECP2-deficient mice displayed improved exploratory, locomotor and social behavior compared to MECP2-deficient mice. These results support testing anti-oxidative strategies for benefit in individuals with Rett syndrome.In this study, the formulation has been adjusted and optimized based on current guidelines for human use, with the goal of translating a potential new treatment from the animal model to use in humans. Results of this study could lead to the first approved medication treatment for the disorder.
96 studies on the registry are indexed under Rett Syndrome; 19 are open to participants now.
This study's planned enrollment of 35 is above the median of 30 across 64 interventional studies indexed under Rett Syndrome.
Browse Rett Syndrome studies →Holland Bloorview Kids Rehabilitation Hospital is the lead sponsor of 64 studies on the registry; 13 are open to participants now.
Counted across the registry records on this site, refreshed daily.
Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
If already receiving stable interventions must meet the following criteria:
Exclusion Criteria:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Ways of preventing pregnancy. “Highly effective” methods fail less than 1% of the time a year when used correctly — for example an IUD or an implant.
Criteria usually say which methods count and how long to keep using them after the last dose, sometimes for male participants too. Some studies accept a partner’s vasectomy if it was confirmed successful and that person is the participant’s only sexual partner.
Malignancy means cancer. Criteria about another or earlier malignancy ask whether you have had a different cancer, usually within a set number of years.
Some are commonly allowed, such as treated skin cancers other than melanoma and early cancers removed completely — check the exceptions this study lists.
An allergy, or another reaction of the immune system, to a substance. “Hypersensitivity to the study drug” means a known allergic reaction to it — not every side effect a medicine can have.
The human immunodeficiency virus, which weakens the immune system.
Many studies now accept people whose HIV is controlled on treatment, judged by the viral load and the CD4 count. Check the limits this study sets.
Hepatitis B is a virus that infects the liver. These are separate tests: HBsAg positive usually means a current infection (a recent vaccination can briefly cause it too); total anti-HBc (HBcAb) positive means an infection now or in the past; HBV DNA measures how much virus is in the blood.
Some studies accept a past infection if HBV DNA is undetectable, sometimes with antiviral medicine during the study. Check what this study allows.
Hepatitis C is a virus that infects the liver. An HCV antibody test can stay positive after an infection has cleared (and is occasionally positive without one); an HCV RNA test shows whether the virus is there now.
After treatment, hepatitis C counts as cured when HCV RNA is still undetectable 12 weeks or more after the treatment ended. Studies often accept people cured this way.
Informed consent
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Contraception
Ways of preventing pregnancy. “Highly effective” methods fail less than 1% of the time a year when used correctly — for example an IUD or an implant.
Criteria usually say which methods count and how long to keep using them after the last dose, sometimes for male participants too. Some studies accept a partner’s vasectomy if it was confirmed successful and that person is the participant’s only sexual partner.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Cancer (malignancy)
Malignancy means cancer. Criteria about another or earlier malignancy ask whether you have had a different cancer, usually within a set number of years.
Some are commonly allowed, such as treated skin cancers other than melanoma and early cancers removed completely — check the exceptions this study lists.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Hypersensitivity
An allergy, or another reaction of the immune system, to a substance. “Hypersensitivity to the study drug” means a known allergic reaction to it — not every side effect a medicine can have.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
HIV
The human immunodeficiency virus, which weakens the immune system.
Many studies now accept people whose HIV is controlled on treatment, judged by the viral load and the CD4 count. Check the limits this study sets.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Hepatitis B tests
Hepatitis B is a virus that infects the liver. These are separate tests: HBsAg positive usually means a current infection (a recent vaccination can briefly cause it too); total anti-HBc (HBcAb) positive means an infection now or in the past; HBV DNA measures how much virus is in the blood.
Some studies accept a past infection if HBV DNA is undetectable, sometimes with antiviral medicine during the study. Check what this study allows.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Hepatitis C tests
Hepatitis C is a virus that infects the liver. An HCV antibody test can stay positive after an infection has cleared (and is occasionally positive without one); an HCV RNA test shows whether the virus is there now.
After treatment, hepatitis C counts as cured when HCV RNA is still undetectable 12 weeks or more after the treatment ended. Studies often accept people cured this way.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Rett T is a powder for oral suspension. Dosage is dependent on weight. For participants weighing \<30 kg, a 4 g dose (i.e., one 4 g sachet) is intended to be administered orally once a day after dissolving in approximately 125 mL of water. For participants weighing ≥30 kg, a 8 g dose (i.e., two 4 g sachets) is intended to be administered orally once a day after dissolving in approximately 250 mL of water.
Drug: Rett-T
Placebo is a powder for oral suspension. Dosage is dependent on weight. For participants weighing \<30 kg, a 4 g dose (i.e., one 4 g sachet) is intended to be administered orally once a day after dissolving in approximately 125 mL of water. For participants weighing ≥30 kg, a 8 g dose (i.e., two 4 g sachets) is intended to be administered orally once a day after dissolving in approximately 250 mL of water.
Other: Placebo
antioxidant cocktail
Placebo
Rett Syndrome Natural History Motor Behavior Assessment (MBA)
To examine the effect of Rett-T vs. placebo on measures of motor function. The Rett Syndrome MBA consists of 37 items grouped into three subscales (Behavioral/Social Assessment, Orofacial Respiratory Assessment, and Motor Assessment/Physical Signs). Items are captured on a 0-4 point Likert scale. Total and subscale scores are calculated (subscales are summed for a total score). The scale range for Total score is 0-136; for Behavioral/Social subscale, 0-60; for Orofacial/Respiratory subscale, 0-28; for Motor Assesment/Physical Signs, 0-48. For both total and subscale scores, higher values represent a worse outcome.
Time frame: 18 weeks total: 8 weeks on Rett-T, 8 weeks on placebo, 2 week washout in interim
Rett Syndrome Gross Motor Scale (RSGMS)
To examine the effect of Rett-T vs. placebo on measures of motor function. The RSGMS consists of 15 gross motor items grouped into three subscales (Sitting, Standing and Walking, and Challenge). Items are captured on a 0-3 Likert Scale rating regarding level of assistance needed (0=maximal, 3 = none). Total and subscale scores are calculated (subscales are summed for a total score). The scale range for Total score is 0-45; for Sitting, 0-9; for Walking, 0-27; for Challenge, 0-9. For both total and subscale scores, higher values represent a better outcome.
Time frame: 18 weeks total: 8 weeks on Rett-T, 8 weeks on placebo, 2 week washout in interim
Safety Monitoring Uniform Report Form (SMURF)
To examine the safety and tolerability of Rett- T in children and youth with Rett syndrome; To explore the effect Rett-T vs. placebo on maladaptive behaviors, anxiety, sleep, seizure
Time frame: 18 weeks total: 8 weeks on Rett-T, 8 weeks on placebo, 2 week washout in interim
Clinical Global Impressions - Improvement Scale - Global (CGI-I)
To explore the effect of Rett-T vs. placebo on global improvement. The CGI-I measures global clinical improvement in response to treatment. A single score is assigned on a 1-7 Likert scale, with 1= very much improved-7=very much worse. Higher values represent a worse outcome.
Time frame: 18 weeks total: 8 weeks on Rett-T, 8 weeks on placebo, 2 week washout in interim
The Top 3 Causes for Concern
To explore the effect Rett-T vs. placebo on maladaptive behaviors, anxiety, sleep, seizure frequency, and global improvement. Respondents are instructed to choose their top three concerns for the participant, and indicate Concern Number #1, 2 and 3 on the form. Respondents are next instructed to place a vertical mark along a visual analogue scale (a 10 centimetre horizontal line in which the leftmost point on the scale indicates the concern is completely absent, and the rightmost point on the scale indicates that the concern is very severe). For each concern, a measurement is taken from the leftmost point of the scale to the vertical mark, and the measurement in centimetres acts as the score. Higher scores represent a worse outcome.
Time frame: 18 weeks total: 8 weeks on Rett-T, 8 weeks on placebo, 2 week washout in interim
The Rett Syndrome Behaviour Questionnaire (RSBQ)
To explore the effect of Rett-T vs. placebo on maladaptive behaviors, anxiety, sleep, seizure frequency, and global improvement. The measure consists of 45 items which are grouped into 8 subscales (General Mood, Breathing Problems, Body Rocking and Expressionless Face, Hand Behaviors, Repetitive Face Movements, Night-time Behaviors, Fear/Anxiety, and Walking/Standing). Items are measured on a 0-2 Likert scale.Total and subscale scores are calculated (subscales are summed for a total score). The scale range for total score is 0-90; for General Mood, 0-16; for Breathing Problems, 0-10; for Body Rocking and Expressionless Face, 0-12; for Hand Behaviours, 0-12; for Repetitive Face Movements, 0-8; for Nighttime Behaviours, 0-6; for Fear/Anxiety; 0-8; for Walking/Standing, 0-4. Seven items are not included in the subscale scores but are included in the total score sum. For both total and subscale scores, higher values represent a worse outcome.
Time frame: 18 weeks total: 8 weeks on Rett-T, 8 weeks on placebo, 2 week washout in interim
Anxiety, Depression, and Mood Scale (ADAMS)
To explore the effect of Rett-T vs. placebo on anxiety. The ADAMS consists of 28 items grouped into five subscales (Manic/Hyperactive Behavior, Depressed Mood, Social Avoidance, General Anxiety, and Obsessive Behavior). Items are scored on a 0-3 Likert scale that combines frequency and severity ratings (where 0=behavior has not occurred or is not a problem, 3=behavior occurs a lot or is a severe problem). Each subscale score is calculated separately; the scale range for Manic/Hyperactive Behavior is 3-15; for Depressed Mood, 7-21; for Social Avoidance, 7-21; for General Anxiety, 7-21; for Obsessive Behavior, 3-9. For each subscale score, higher values represent a worse outcome.
Time frame: 18 weeks total: 8 weeks on Rett-T, 8 weeks on placebo, 2 week washout in interim
Children's Sleep Habits Questionnaire (CSHQ)
To explore the effect of Rett-T vs. placebo on sleep. The CSHQ is a tool designed to screen for the most common sleep problems in children. The CSHQ consists of 35 items for scoring and extra unscored items intended to provide administrators with other potentially useful information about respondents. The instrument evaluates sleep based on behavior within eight different subscales (Bedtime Resistance, Sleep-Onset Delay, Sleep Duration, Sleep Anxiety, Night Wakings, Parasomnias, Sleep-Disordered Breathing, and Daytime Sleepiness).Total and subscale scores are calculated (33 items are summed for a total score). The scale range for Total score is 33-99; for Bedtime Resistance subscale, 6-18; for Sleep Onset/Delay, 1-3; for Sleep Duration, 3-9; for Sleep Anxiety, 4-12; For Night Wakings, 3-9; for Parasomnias, 7-21; for Sleep-Disordered Breathing, 3-9; for Daytime Sleepiness, 8-24. For both total and subscale scores, higher values represent a worse outcome.
Time frame: 18 weeks total: 8 weeks on Rett-T, 8 weeks on placebo, 2 week washout in interim
Plan to share: No
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Start is estimated for Aug 2026; primary completion for Dec 2027, 16 months later.
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Holland Bloorview Kids Rehabilitation Hospital