NCT07417137 · Massachusetts General Hospital
A Natural History Study of Angelman Syndrome
(GLOW-AS)
What this study is about
The goal of this observational study is to learn about the natural progression of Angelman syndrome (AS) in children and adults with a confirmed genetic diagnosis of AS.
View original scientific description
The goal of this observational study is to learn about the natural progression of Angelman syndrome (AS) in children and adults with a confirmed genetic diagnosis of AS. The main questions it aims to answer are: * How do developmental skills, such as communication, motor abilities, and adaptive behaviors, change over a 1-year period in people with AS? * Are there specific patterns in brain activity or sleep that are associated with changes in AS symptoms over time? Participants will: * Visit the study site 5 times over 1 year (approximately every 3 months) for assessments. * Complete tests and questionnaires about development, behaviors, and sleep with the help of their caregivers. * Undergo electroencephalograms (EEGs) to measure brain activity and wear a sleep-monitoring device at home (to collect actigraphy data).
Primary outcome measures
Change from Baseline in Bayley Scale of Infant Development, Fourth Edition (Bayley-4) Cognitive Growth Score Equivalent at 12 Months
Time frame: Baseline, 3 months, 6 months, 9 months, and 12 months
The Bayley-4 Cognitive subscale assesses cognitive development in children. Growth score equivalents are derived from developmental growth scale values (GSVs) that provide an equal-interval scale for measuring developmental change over time. Higher scores indicate greater cognitive development.
Change from Baseline in Bayley Scale of Infant Development, Fourth Edition (Bayley-4) Receptive Communication Growth Score Equivalent at 12 Months
Time frame: Baseline, 3 months, 6 months, 9 months, and 12 months
The Bayley-4 Receptive Communication subscale assesses receptive language skills. Growth score equivalents are derived from developmental GSVs that provide an equal-interval scale for measuring developmental change over time. Higher scores indicate more advanced receptive communication abilities.
Change from Baseline in Bayley Scale of Infant Development, Fourth Edition (Bayley-4) Expressive Communication Growth Score Equivalent at 12 Months
Time frame: Baseline, 3 months, 6 months, 9 months, and 12 months
The Bayley-4 Expressive Communication subscale assesses expressive language skills. Growth score equivalents are derived from developmental GSVs that provide an equal-interval scale for measuring developmental change over time. Higher scores indicate more developed expressive communication abilities.
Change from Baseline in Bayley Scale of Infant Development, Fourth Edition (Bayley-4) Fine Motor Growth Score Equivalent at 12 Months
Time frame: Baseline, 3 months, 6 months, 9 months, and 12 months
The Bayley-4 Fine Motor subscale assesses fine motor skill development. Growth score equivalents are derived from developmental GSVs that provide an equal-interval scale for measuring developmental change over time. Higher scores indicate more developed fine motor skills.
Change from Baseline in Bayley Scale of Infant Development, Fourth Edition (Bayley-4) Gross Motor Growth Score Equivalent at 12 Months
Time frame: Baseline, 3 months, 6 months, 9 months, and 12 months
The Bayley-4 Gross Motor subscale assesses gross motor skill development. Growth score equivalents are derived from developmental GSVs that provide an equal-interval scale for measuring developmental change over time. Higher scores indicate more developed gross motor skills.
Who can participate
This study lists these criteria on ClinicalTrials.gov. A study coordinator reviews eligibility during screening — this page does not determine whether you qualify.
Inclusion criteria
- The participant has a primary clinical diagnosis of Angelman syndrome with documented genetic variation(s) affecting the function of the UBE3A gene within the human 15q11.2-q13.3 locus. Co-occurring conditions (e.g., autism spectrum disorder, cerebral palsy, intellectual disability) are permitted; however, Angelman syndrome must be the primary clinical diagnosis.
- The participant is male or female (assigned sex at birth) and aged ≥1 year at the initial study visit.
- The participant has a study partner who meets the study partner criteria below.
- The participant, if unable to provide informed consent, has an appropriate surrogate who is at least 18 years of age and willing and able to provide informed consent on behalf of the participant in accordance with current International Council for Harmonisation (ICH) guidelines and applicable institutional regulations. Individuals must satisfy the following criteria to be enrolled as study partners:
- The study partner is a parent or primary caregiver who is at least 18 years of age.
- The study partner has consistent contact with the participant and, in the opinion of the investigator, is sufficiently knowledgeable about the participant's ongoing condition to provide accurate and current information.
- The study partner has sufficient English-language proficiency to complete study partner assessments.
- The study partner is willing and able to provide informed consent on their own behalf in accordance with ICH guidelines and applicable institutional regulations.
- The study partner is, in the opinion of the investigator, reliable and competent; willing and able to accompany the participant to all study visits and comply with study procedures; reachable by telephone or email as needed; and sufficiently knowledgeable about the participant's ongoing condition(s) to provide accurate and current information regarding the participant's health and well-being.
Exclusion criteria
- The participant has at least one additional known genetic abnormality outside the human 15q11.2-q13.3 locus causing a probable or known developmental disability.
- At least one standard-of-care treatment (medication or adjunctive therapy) used by the participant was changed during the 28 days (4 weeks) prior to the first study visit. Treatments include, but are not limited to, doses of anti-epileptic medications, behavioral management medications, sleep medications, gabapentin, cannabidiol, special diets, supplements, speech therapy, occupational therapy, applied behavioral analysis (ABA), psychosocial interventions, physical therapy, or nutritional support.
- The participant has unstable epilepsy, defined as having an emergency department visit or hospitalization for seizure-related concerns within the 28 days (4 weeks) preceding the initial study visit.
- The participant is of childbearing potential and is either pregnant, breastfeeding, or not using an adequate method of contraception; abstinence is acceptable.
- The participant has a clinically relevant history of malignancy; clinically significant abnormal test results; clinically significant cardiovascular, hematologic, hepatic, muscular, neurologic, or renal disease; or has experienced other clinical events which, in the opinion of the investigator, render participation unsuitable.
- The participant has a lifetime history of treatment with any cell- or gene-based therapy, including antisense oligonucleotides or gene-editing therapies.
- The participant has received any investigational therapy other than a cell- or gene-based therapy within 28 days or 5 half-lives (whichever is longer) preceding the initial study visit.
- The participant is currently enrolled or plans to enroll in an interventional study involving an investigational agent or device during the planned observation period.
- The participant has a known contraindication to electroencephalography, actigraphy, or any other study procedure described in the schedule of assessments.
- The participant or study partner is, in the opinion of the investigator, unsuitable for participation in any other way, including an inability to fulfill study requirements.
Where
- Lexington, Massachusetts
Collaborators
Astellas Pharma Global Development, Inc.
Related conditions & keywords
Frequently asked questions
What is a clinical trial?
A clinical trial is a research study that tests new medical treatments, drugs, devices, or procedures to determine their safety and effectiveness. Trials are carefully designed and monitored to protect participants while advancing medical knowledge.
Is it safe to participate?
Clinical trials follow strict safety guidelines and ethical standards. Trials must be reviewed and approved, and participants are closely monitored by medical professionals throughout the study. You can withdraw at any time if you choose.
Will I be compensated?
Many clinical trials offer compensation for your time, travel expenses, and inconvenience. The specific compensation varies by study and will be discussed during the screening process. All study-related medical care is typically provided at no cost to participants.
Will I receive a placebo instead of treatment?
When effective treatment exists, participants typically receive either the standard treatment plus the study intervention, or the standard treatment plus placebo. You would not be denied effective care. Placebos are primarily used when no proven treatment is available, or in addition to standard care. Your trial consent form will clearly explain what treatments you may receive.
Can I leave a trial if I change my mind?
Absolutely. Participation in clinical trials is completely voluntary. You have the right to withdraw from the study at any time, for any reason, without penalty or loss of benefits to which you are otherwise entitled.
How long does a clinical trial last?
Trial duration varies widely depending on the study design and purpose. Some trials last just a few weeks, while others may continue for months or years. The study coordinator will provide specific timeline information during your screening call.
Data: ClinicalTrials.gov · synced May 18, 2026 · Source of record for eligibility and locations