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Fenfluramine Hydrochloride for Rett Syndrome

This study is testing fenfluramine hydrochloride to see if it can help people with Rett Syndrome. Researchers want to compare its effects to a placebo (an inactive substance that looks like the study drug). You might be able to join if you are between 5 and 35 years old, have typical or classic Rett Syndrome, and have a specific change in your MECP2 gene. The study will look at changes in a Rett Syndrome behavior questionnaire and a doctor's overall impression of your condition after 14 weeks. The study plans to enroll 200 participants, but its current status is unclear.

Study design
This is an interventional study comparing fenfluramine hydrochloride to a placebo in 200 participants with Rett Syndrome.
What's involved
Not specified in the trial record.
Compensation
Not stated in the trial record.
Follow-up
The primary endpoints are measured at Week 14.

AI-generated from the public study record. Only the study team can confirm whether you're eligible — confirm details with them before making decisions.

NCT07503444

A Phase 3 Study of Fenfluramine Hydrochloride in Rett Syndrome

Recruiting
PHASE3Ages 5–35InterventionalTreatment
UCB BIOSCIENCES, Inc.
~200 participants
Updated 2026-08-17 on ClinicalTrials.gov
What's tested:fenfluramine hydrochloridePlacebo

At a glance

Recruiting sites
18 of 18 listed sites are recruiting right now
RecruitingSuspended, closed, or not yet open
What they're measuring
Change from Baseline to Week 14 in Rett Syndrome Behaviour Questionnaire (RSBQ) Total Score
Measured over From Baseline (Day 1) to Week 14
+1 more outcome measured

Conditions

Rett Syndrome

Explore related trials

Rett SyndromeMECP2 Gene

Where it's being run

18 sites across 11 states
Japan4
Spain3
Texas2
Hungary2
Arkansas1
Florida1
Georgia1
Belgium1

Study leadership

  • UCB Cares · STUDY_DIRECTOR · 0018445992273

Who to contact

UCB Cares
[email protected]
+18445992273
Email the study team

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Do you actually qualify for this trial?

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Eligibility criteria

Inclusion

Participant has typical or classic Rett Syndrome (RTT) according to the RettSearch Consortium 2010 revised criteria
Participant has a documented disease-causing mutation or deletion in the methyl-CpG-binding protein 2 (MECP2) gene
Participant meets criteria for postregression for at least 6 months prior to Screening, defined as:
No loss or degradation of ambulation (including gait, coordination, or independence of walking/standing);
No loss or degradation of hand function; no loss or degradation of speech (including babbling, words, or previously developed communicative vocalizations);
No loss or degradation of nonverbal communicative or social skills (including eye gaze, using body to indicate communicative intent, or social attentiveness)
Participant has an Rett Syndrome Clinical Severity Scale (RTT-CSS) rating of 10 to 36 (inclusive)
Participant has a Clinical Global Impression-Severity (CGIS) score of ≥4
Participant has a legal representative capable of providing signed informed consent on behalf of the participant as described in the protocol, which includes compliance with the requirements and restrictions listed in the informed consent form (ICF) and in the protocol.
Participant is aged 5 to 35 years of age (inclusive) at the time of first administration of investigational intervention.
Male or female.
Participant has a consistent caregiver who is ≥18 years of age at the Screening Visit. The caregiver needs to be able to complete the caregiver assessments defined for the entire study. Every attempt should be made to have the same evaluator complete the assessments for the duration of the study.

Exclusion

Participant has a history of lymphoma, leukemia, or any malignancy within the past 5 years except for basal cell or squamous epithelial carcinomas of the skin that have been resected with no evidence of metastatic disease for 3 years.
Participant has clinically significant abnormality in vital signs according to the Investigator
Participant has an exclusionary cardiovascular or cardiopulmonary abnormality based on echocardiogram (ECHO), electrocardiogram (ECG), or physical examination, and is not approved for entry by the central cardiac reader. Exclusionary abnormalities include, but are not limited to:
Participant has a clinically significant medical condition, including chronic obstructive pulmonary disease, interstitial lung disease, portal hypertension, or need for invasive mechanical ventilation (eg, via tracheostomy), or has had clinically relevant symptoms or a clinically significant illness currently or in the 4 weeks prior to the Screening Visit that would negatively impact study participation, collection of study data, or pose a risk to the participant
Participant is taking \>4 concomitant antiseizure medications (ASMs). Rescue medications are not included in the count

What this trial measures

  • Change from Baseline to Week 14 in Rett Syndrome Behaviour Questionnaire (RSBQ) Total ScoreFrom Baseline (Day 1) to Week 14

    The RSBQ is a caregiver-completed, instrument assessing behavioral and emotional features in RTT. The RSBQ consists of 45 items, including 8 subscales: General mood (8 items); Breathing problems (5 items); Hand behavior (6 items); Face movements (4 items); Body rocking and expressionless face (6 items); Nighttime behaviors (3 items); Fear/anxiety (4 items); and Walking/standing (2 items). Caregivers are asked to evaluate each RTT feature based on the current status of the patients on a 3-point scale as 0 ("not true"), 1 ("somewhat or sometimes true"), or 2 ("often true"), with the total score ranging from 0 to 90. Higher scores indicate increased disease severity. Seven items that do not belong under any of the subscales are classed as "uncategorized" but contribute to the overall total score.

  • Clinical Global Impression of Change (CGIC) Score at Week 14At Week 14

    The CGIC is a clinician-rated single item evaluating the degree of improvement or worsening of a participant's condition from Baseline following treatment or intervention. The CGIC uses a 7-point response scale, with the following ratings: "1: Very Much improved", "2: Much improved", "3: Minimally improved", "4: No change", "5: Minimally worse", "6: Much worse", "7: Very Much Worse".