Rett SyndromePhase 3NCT07503444
A Phase 3 Study of Fenfluramine Hydrochloride in Rett Syndrome
A Phase 3 study testing fenfluramine hydrochloride in people with Rett Syndrome, run by UCB BIOSCIENCES, Inc. at 40 sites in 12 countries.
Trial summary
The purpose of this study is to investigate the efficacy of fenfluramine hydrochloride (HCl) versus placebo in study participants with Rett syndrome (RTT). Read more about this study
- Who is it for?
- Ages 5 to 35 years
- Conditions the study is for
- Rett Syndrome
- What is being tested?
- fenfluramine hydrochloride
- Type of treatment
- Pill or oral medicine
- Could I receive a placebo?
- Yes, some participants may receive a placebo
- How many people
- 200 participants
- Where
- 40 sitesin 12 countries
- Study dates
- 14 Jul 2026to 29 Aug 2031
- Phase
- Phase 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 5 to 35 years
- All sexes
- No healthy volunteers
- Child, Adult
Who may be able to join
- 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)
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- 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.
Who cannot join
- 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:
- Greater than trace aortic valve regurgitation.
- Greater than mild mitral valve regurgitation.
- Possible signs of pulmonary arterial hypertension (PAH) with abnormal pulmonary artery systolic pressure (PASP) or PASP ≥35 mmHg.
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- Evidence of left ventricular dysfunction (systolic or diastolic).
- Clinically significant structural cardiac abnormality, including but not limited to mitral valve prolapse, atrial or ventricular septal defects, or patent ductus arteriosus with reversal of shunt (right to left shunt). Note: Patent foramen ovale without a reversal of shunt or a bicuspid aortic valve is not considered exclusionary
- 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
Trial locations and contacts
40 sites in 12 countries. Contact the study team or a site near you to ask about taking part.
40 sites in 12 countries
United States8 sites, 8 recruiting
- Recruiting
Ep0247 21007
Atlanta, Georgia, 30322
- Recruiting
Ep0247 21005
Houston, Texas, 77030
- Recruiting
Ep0247 21013
Irving, Texas, 75062
- Recruiting
Ep0247 21010
Little Rock, Arkansas, 72202
- Recruiting
Ep0247 21009
Miami, Florida, 33155
- Recruiting
Ep0247 21011
Orlando, Florida, 32806
- Recruiting
Ep0247 21003
Philadelphia, Pennsylvania, 19104-4318
- Recruiting
Ep0247 21004
Seattle, Washington, 98105
Japan6 sites, 6 recruiting
- Recruiting
Ep0247 43005
Chiyoda-ku
- Recruiting
Ep0247 43004
Kodaira
- Recruiting
Ep0247 43001
Kurume
- Recruiting
Ep0247 43006
Musashimurayama-shi
- Recruiting
Ep0247 43002
Osaka
- Recruiting
Ep0247 43003
Setagaya-ku
France5 sites, 5 recruiting
- Recruiting
Ep0247 12005
Brest
- Recruiting
Ep0247 12003
Bron
- Recruiting
Ep0247 12004
Marseille
- Recruiting
Ep0247 12001
Paris
- Recruiting
Ep0247 12006
Paris
Italy5 sites, 5 recruiting
- Recruiting
Ep0247 17003
Genova
- Recruiting
Ep0247 17001
Milan
- Recruiting
Ep0247 17008
Naples
- Recruiting
Ep0247 17002
Pisa
- Recruiting
Ep0247 17006
Troina
Spain4 sites, 4 recruiting
- Recruiting
Ep0247 11101
Madrid
- Recruiting
Ep0247 11105
Madrid
- Recruiting
Ep0247 11103
Málaga
- Recruiting
Ep0247 11102
Seville
Belgium2 sites, 2 recruiting
- Recruiting
Ep0247 11001
Brussels
- Recruiting
Ep0247 11002
Edegem
Georgia2 sites, 2 recruiting
- Recruiting
Ep0247 13001
Tbilisi
- Recruiting
Ep0247 13002
Tbilisi
Hungary2 sites, 2 recruiting
- Recruiting
Ep0247 15001
Budapest
- Recruiting
Ep0247 15002
Debrecen
Poland2 sites, 2 recruiting
- Recruiting
Ep0247 19003
Gdansk
- Recruiting
Ep0247 19002
Krakow
United Kingdom2 sites, 2 recruiting
- Recruiting
Ep0247 11303
Manchester
- Recruiting
Ep0247 11304
Nottingham
About this study
Official title: A Phase 3 Randomized, Double-Blind, Placebo Controlled, Parallel Group, Multicenter Study With Open-Label Extension to Evaluate the Efficacy And Safety of Fenfluramine Hydrochloride in Study Participants With Rett Syndrome
The purpose of this study is to investigate the efficacy of fenfluramine hydrochloride (HCl) versus placebo in study participants with Rett syndrome (RTT).
- Conditions
- Rett Syndrome
- Being tested
- fenfluramine hydrochloride, Placebo
- Keywords
- Fenfluramine HCl, RTT
- Medical subject headings
- Rett Syndrome
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
fenfluramine hydrochlorideDrug
Also called Fintepla, ZX008
Oral solution
PlaceboOther
Oral solution
| Study group | Role | What they receive |
|---|---|---|
| fenfluramine hydrochloride | Experimental | Participants will receive fenfluramine hydrochloride for 14 weeks in a double-blind period (including titration and maintenance), followed by a 2-week double-blind transition period. This is followed by a 52-week open-label treatment period. Participants may continue treatment until alternative access is available. Those who discontinue without continued access will undergo an 8-day taper and a 26-week follow-up. Receives: Drug: fenfluramine hydrochloride |
| Placebo | Placebo comparator | Participants will receive a matching placebo for 14 weeks in a double-blind period (including titration and maintenance). After this period, they transition into a 2-week double-blind period with fenfluramine hydrochloride, followed by a 52-week open-label treatment period. Participants may continue treatment until alternative access is available. Those who discontinue without continued access will undergo an 8-day taper and a 26-week follow-up. Receives: Other: Placebo |
What is being measured
The primary outcome is the main question the study is designed to answer.
Change from Baseline to Week 14 in Rett Syndrome Behaviour Questionnaire (RSBQ) Total Score
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.
Measured: From Baseline (Day 1) to Week 14
Clinical Global Impression of Change (CGIC) Score at 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".
Measured: At Week 14
Secondary outcomes (17)
Change from Baseline to Week 14 in Patient-Reported Outcomes Measurement Information System-Sleep Disturbance (PROMIS-SD) score
Sleep disturbances will be assessed by the PROMIS-SD parent proxy 8a version. Caregivers are asked to rate 8 items over the past 7 days on a 5-point scale: "1: Never", "2: Almost never", "3: Sometimes", "4: Almost always", and "5: Always", with higher scores indicating more severe sleep disturbances.
Measured: From Baseline (Day 1) to Week 14
Change from Baseline to Week 14 in Observer-Reported Communication Ability (ORCA) score
The ORCA is an 84-item, observer-reported measure of communication ability over the past 30 days. The majority of the items included in the ORCA measure have 3 response options: "No or only once," "Sometimes," and "Yes, almost all the time", which enable derivation of an overall communication score and scores for each form of communication (expressive, receptive, and pragmatic), with higher scores indicating greater communication ability.
Measured: From Baseline (Day 1) to Week 14
Caregiver Global Impression of Change - Seizure (CaGIC-Seizure) score at Week 14
The CaGIC-Seizure is a caregiver-reported item assessing the change from Baseline in the participant's seizure status. The CaGIC-Seizure 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".
Measured: At Week 14
Incidence of treatment-emergent adverse events (TEAEs) during the double-blind intervention period
An AE is any untoward medical occurrence in a clinical study participant temporally associated with the use of study intervention, whether or not considered related to the study intervention. Treatment emergent adverse events (TEAEs) are adverse events that are not present prior to the pharmaceutical product administration or an already present event that worsens either in intensity or frequency.
Measured: From Baseline (Day 1) up to Week 14
Incidence of serious TEAEs during the double-blind intervention period
An SAE is defined as any untoward medical occurrence that, at any dose, meets 1 or more of the criteria listed:
- Results in death
- Is life-threatening
- Requires inpatient hospitalization or prolongation of existing hospitalization
- Results in persistent or significant disability/incapacity
- Is a congenital anomaly/birth defect
- Other important medical events which based on medical or scientific judgement may jeopardize the patients or may require medical or surgical intervention to prevent any of the above.
Measured: From Baseline (Day 1) up to Week 14
Incidence of TEAEs leading to discontinuation during the double-blind intervention period
An AE is any untoward medical occurrence in a clinical study participant temporally associated with the use of study intervention, whether or not considered related to the study intervention. Treatment emergent adverse events (TEAEs) are adverse events that are not present prior to the pharmaceutical product administration or an already present event that worsens either in intensity or frequency. TEAEs leading to discontinuation will be reported.
Measured: From Baseline (Day 1) up to Week 14
Incidence of related TEAEs during the double-blind intervention period
An AE is any untoward medical occurrence in a clinical study participant temporally associated with the use of study intervention, whether or not considered related to the study intervention. Treatment emergent adverse events (TEAEs) are adverse events that are not present prior to the pharmaceutical product administration or an already present event that worsens either in intensity or frequency. Related TEAEs will be reported.
Measured: From Baseline (Day 1) up to Week 14
Change from Baseline in QT interval corrected using Fridericia's formula (QTcF) interval on 12-lead ECG by visit during the double-blind intervention period
Change from Baseline in QTcF interval as measured by 12-lead ECG up to Week 14 by visit will be reported
Measured: From Baseline (Day 1) up to Week 14
Incidence of treatment-emergent Doppler Echocardiogram (ECHO) results meeting the Food and Drug Administration (FDA) case definition of drug-associated valvular heart disease (VHD) during the double-blind intervention period
The FDA case definition of drug-associated VHD is aortic regurgitation ≥mild and/or mitral regurgitation ≥moderate with restricted valve motion, valve thickening, and/or physical signs or symptoms attributable to valve diseases. ECHO readings related to VHD on any of the 4 valves (aortic, mitral, pulmonary, tricuspid) will be reported with grades of absent, trace, mild, moderate, or severe.
Measured: From Baseline (Day 1) up to Week 14
Incidence of treatment-emergent Doppler ECHO results meeting the FDA case definition of PAH (defined as a PASP >35mmHg) during the double-blind intervention period
ECHO readings related to pulmonary arterial hypertenstion (PAH) will be reported based on Pulmonary artery systolic pressure (PASP).
Measured: From Baseline (Day 1) up to Week 14
Incidence of treatment-emergent adverse events (TEAEs) from baseline to end of safety follow up
An AE is any untoward medical occurrence in a clinical study participant temporally associated with the use of study intervention, whether or not considered related to the study intervention. Treatment emergent adverse events (TEAEs) are adverse events that are not present prior to the pharmaceutical product administration or an already present event that worsens either in intensity or frequency.
Measured: From Baseline (Day1) to the End of Safety Follow Up (up to 3 years and 10 months)
Incidence of serious TEAEs from baseline to end of safety follow up
An SAE is defined as any untoward medical occurrence that, at any dose, meets 1 or more of the criteria listed:
- Results in death
- Is life-threatening
- Requires inpatient hospitalization or prolongation of existing hospitalization
- Results in persistent or significant disability/incapacity
- Is a congenital anomaly/birth defect
- Other important medical events which based on medical or scientific judgement may jeopardize the patients or may require medical or surgical intervention to prevent any of the above.
Measured: From Baseline (Day1) to the End of Safety Follow Up (up to 3 years and 10 months)
Incidence of TEAEs leading to discontinuation from baseline to end of safety follow up
An AE is any untoward medical occurrence in a clinical study participant temporally associated with the use of study intervention, whether or not considered related to the study intervention. Treatment emergent adverse events (TEAEs) are adverse events that are not present prior to the pharmaceutical product administration or an already present event that worsens either in intensity or frequency. TEAEs leading to discontinuation will be reported.
Measured: From Baseline (Day1) to the End of Safety Follow Up (up to 3 years and 10 months)
Incidence of related TEAEs from baseline to end of safety follow up
An AE is any untoward medical occurrence in a clinical study participant temporally associated with the use of study intervention, whether or not considered related to the study intervention. Treatment emergent adverse events (TEAEs) are adverse events that are not present prior to the pharmaceutical product administration or an already present event that worsens either in intensity or frequency. Related TEAEs will be reported.
Measured: From Baseline (Day1) to the End of Safety Follow Up (up to 3 years and 10 months)
Change from Baseline in QT interval corrected using Fridericia's formula (QTcF) interval on 12-lead ECG by visit from baseline to end of safety follow up
Change from Baseline in QTcF interval as measured by 12-lead ECG up to Week 98 by visit will be reported
Measured: From Baseline (Day1) to the End of Safety Follow Up (up to 3 years and 10 months)
Incidence of treatment-emergent Doppler Echocardiogram (ECHO) results meeting the Food and Drug Administration (FDA) case definition of drug-associated valvular heart disease (VHD) from baseline to end of safety follow up
The FDA case definition of drug-associated VHD is aortic regurgitation ≥mild and/or mitral regurgitation ≥moderate with restricted valve motion, valve thickening, and/or physical signs or symptoms attributable to valve diseases. ECHO readings related to VHD on any of the 4 valves (aortic, mitral, pulmonary, tricuspid) will be reported with grades of absent, trace, mild, moderate, or severe.
Measured: From Baseline (Day1) to the End of Safety Follow Up (up to 3 years and 10 months)
Incidence of treatment-emergent Doppler ECHO results meeting the FDA case definition of PAH (defined as a PASP >35mmHg) from baseline to end of safety follow up
ECHO readings related to pulmonary arterial hypertenstion (PAH) will be reported based on Pulmonary artery systolic pressure (PASP).
Measured: From Baseline (Day1) to the End of Safety Follow Up (up to 3 years and 10 months)
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted31 Mar 2026
- Study start14 Jul 2026
- Primary completion6 Feb 2029 (estimated)
- Study completion29 Aug 2031 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Rett SyndromeStudies of the same condition, open and under way.
- 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 3
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- Triple blind
- Who is masked
- Participant, Care provider, Investigator
- Enrolment
- 200 participants (estimated)
Sponsor and investigators
- Lead sponsor
- UCB BIOSCIENCES, Inc.
- Sponsor type
- Industry (pharma, biotech, devices)
- Responsible party
- Sponsor
- Investigators
- UCB Cares, Study director, 0018445992273
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT07503444
- Sponsor's protocol ID
- EP0247
- Other IDs
- 2025-523157-34, 2025
- Status last verified
- Oct 2026
- First submitted
- 25 Mar 2026
- Last updated
- 2 Nov 2026
- Results posted
- No
- Data monitoring committee
- Yes
- FDA-regulated drug
- Yes
- FDA-regulated device
- No
- Individual data sharing
- Yes: Data from this trial may be requested by qualified researchers six months after product approval in the US and/or Europe, or global development is discontinued, and 18 months after trial completion. Investigators may request access to anonymized individual patient-level data and redacted trial documents which may include: analysis-ready datasets, study protocol, annotated case report form, statistical analysis plan, dataset specifications, and clinical study report. Prior to use of the data, proposals need to be approved by an independent review panel at www.Vivli.org and a signed data sharing agreement will need to be executed. All documents are available in English only, for a pre-specified time, typically 12 months, on a password protected portal. This plan may change if the risk of re-identifying trial participants is determined to be too high after the trial is completed; in this case and to protect participants, individual patient-level data would not be made available.
Study at a glance
From the registry record, last updated by the sponsor on 2 Nov 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- A Phase 3 Randomized, Double-Blind, Placebo Controlled, Parallel Group, Multicenter Study With Open-Label Extension to Evaluate the Efficacy And Safety of Fenfluramine Hydrochloride in Study Participants With Rett Syndrome
- ClinicalTrials.gov ID
- NCT07503444
- Acronym / sponsor ID
- EP0247
- Conditions
- Rett Syndrome
- Keywords
- Fenfluramine HCl, RTT
- Phase
- Phase 3
- Study type
- Interventional
- Recruitment status
- Recruiting
- Enrolment
- 200 participants (estimated)
- Lead sponsor
- UCB BIOSCIENCES, Inc.Industry (pharma, biotech, devices)
- Study start
- 14 Jul 2026 (actual)
- Primary completion
- 6 Feb 2029 (estimated)
- Study completion
- 29 Aug 2031 (estimated)
- First posted
- 31 Mar 2026 (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 purpose of this study is to investigate the efficacy of fenfluramine hydrochloride (HCl) versus placebo in study participants with Rett syndrome (RTT).
Study design
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- Triple blind (participant, care provider, investigator)
- Number of arms
- 2
| Arm | Type | Receives |
|---|---|---|
| fenfluramine hydrochloride | Experimental | Drug: fenfluramine hydrochlorideParticipants will receive fenfluramine hydrochloride for 14 weeks in a double-blind period (including titration and maintenance), followed by a 2-week double-blind transition period. This is followed by a 52-week open-label treatment period. Participants may continue treatment until alternative access is available. Those who discontinue without continued access will undergo an 8-day taper and a 26-week follow-up. |
| Placebo | Placebo comparator | Other: PlaceboParticipants will receive a matching placebo for 14 weeks in a double-blind period (including titration and maintenance). After this period, they transition into a 2-week double-blind period with fenfluramine hydrochloride, followed by a 52-week open-label treatment period. Participants may continue treatment until alternative access is available. Those who discontinue without continued access will undergo an 8-day taper and a 26-week follow-up. |
Who may qualify
- Ages
- 5 to 35 years
- Sex
- All
- Healthy volunteers
- Not accepted
- Age groups
- Child, Adult
Key inclusion criteria (12 listed)
- 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);
Key exclusion criteria (10 listed)
- 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
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 |
|---|---|---|
| fenfluramine hydrochlorideAlso: Fintepla, ZX008Oral solution | Drug | fenfluramine hydrochloride |
| PlaceboOral solution | Other | Placebo |
Primary outcome
Change from Baseline to Week 14 in Rett Syndrome Behaviour Questionnaire (RSBQ) Total Score
Time frame: From 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 14
Time frame: At 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".
17 secondary outcomes
Change from Baseline to Week 14 in Patient-Reported Outcomes Measurement Information System-Sleep Disturbance (PROMIS-SD) score
Time frame: From Baseline (Day 1) to Week 14
Change from Baseline to Week 14 in Observer-Reported Communication Ability (ORCA) score
Time frame: From Baseline (Day 1) to Week 14
Caregiver Global Impression of Change - Seizure (CaGIC-Seizure) score at Week 14
Time frame: At Week 14
Incidence of treatment-emergent adverse events (TEAEs) during the double-blind intervention period
Time frame: From Baseline (Day 1) up to Week 14
Incidence of serious TEAEs during the double-blind intervention period
Time frame: From Baseline (Day 1) up to Week 14
Incidence of TEAEs leading to discontinuation during the double-blind intervention period
Time frame: From Baseline (Day 1) up to Week 14
Incidence of related TEAEs during the double-blind intervention period
Time frame: From Baseline (Day 1) up to Week 14
Change from Baseline in QT interval corrected using Fridericia's formula (QTcF) interval on 12-lead ECG by visit during the double-blind intervention period
Time frame: From Baseline (Day 1) up to Week 14
Incidence of treatment-emergent Doppler Echocardiogram (ECHO) results meeting the Food and Drug Administration (FDA) case definition of drug-associated valvular heart disease (VHD) during the double-blind intervention period
Time frame: From Baseline (Day 1) up to Week 14
Incidence of treatment-emergent Doppler ECHO results meeting the FDA case definition of PAH (defined as a PASP >35mmHg) during the double-blind intervention period
Time frame: From Baseline (Day 1) up to Week 14
Incidence of treatment-emergent adverse events (TEAEs) from baseline to end of safety follow up
Time frame: From Baseline (Day1) to the End of Safety Follow Up (up to 3 years and 10 months)
Incidence of serious TEAEs from baseline to end of safety follow up
Time frame: From Baseline (Day1) to the End of Safety Follow Up (up to 3 years and 10 months)
Incidence of TEAEs leading to discontinuation from baseline to end of safety follow up
Time frame: From Baseline (Day1) to the End of Safety Follow Up (up to 3 years and 10 months)
Incidence of related TEAEs from baseline to end of safety follow up
Time frame: From Baseline (Day1) to the End of Safety Follow Up (up to 3 years and 10 months)
Change from Baseline in QT interval corrected using Fridericia's formula (QTcF) interval on 12-lead ECG by visit from baseline to end of safety follow up
Time frame: From Baseline (Day1) to the End of Safety Follow Up (up to 3 years and 10 months)
Incidence of treatment-emergent Doppler Echocardiogram (ECHO) results meeting the Food and Drug Administration (FDA) case definition of drug-associated valvular heart disease (VHD) from baseline to end of safety follow up
Time frame: From Baseline (Day1) to the End of Safety Follow Up (up to 3 years and 10 months)
Incidence of treatment-emergent Doppler ECHO results meeting the FDA case definition of PAH (defined as a PASP >35mmHg) from baseline to end of safety follow up
Time frame: From Baseline (Day1) to the End of Safety Follow Up (up to 3 years and 10 months)
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 2 Nov 2026.
- Individual participant dataSharing planned: Yes. Data from this trial may be requested by qualified researchers six months after product approval in the US and/or Europe, or global development is discontinued, and 18 months after trial completion. Investigators may request access to anonymized individual patient-level data and redacted trial documents which may include: analysis-ready datasets, study protocol, annotated case report form, statistical analysis plan, dataset specifications, and clinical study report. Prior to use of the data, proposals need to be approved by an independent review panel at www.Vivli.org and a signed data sharing agreement will need to be executed. All documents are available in English only, for a pre-specified time, typically 12 months, on a password protected portal. This plan may change if the risk of re-identifying trial participants is determined to be too high after the trial is completed; in this case and to protect participants, individual patient-level data would not be made available.
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Rett Syndrome, RTT
RecruitingPhase 1/2
ATTUNE: A Study to Evaluate the Safety, Tolerability, Pharmacokinetics, and Pharmacodynamics of Intrathecally-Administered ION440 in Participants With Methyl CpG Binding Protein 2 (MECP2) Duplication Syndrome (MDS)
Methyl CpG Binding Protein 2 (MECP2) Duplication Syndrome
Active, not recruiting
Web Intervention for Parents of Youth With Genetic Syndromes (WINGS)
Telomeric 22Q13 Monosomy Syndrome, Tuberous Sclerosis
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.
UCB Cares study director
0018445992273
40 sites in 12 countries: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A Phase 3 study testing fenfluramine hydrochloride in people with Rett Syndrome, run by UCB BIOSCIENCES, Inc. at 40 sites in 12 countries.
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 12 inclusion and 10 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 2 Nov 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 40 sites in United States, Japan, France, Italy, Spain and 7 more countries. 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 phase mean?
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 UCB Cares (+18445992273, ucbcares@ucb.com), or a site near the patient. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Change from Baseline to Week 14 in Rett Syndrome Behaviour Questionnaire (RSBQ) Total Score (time frame: From Baseline (Day 1) to Week 14). 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 2 Nov 2026.