A Phase 3 interventional study of obudanersen and Placebo in Angelman Syndrome, sponsored by Ionis Pharmaceuticals, Inc.. Active, not recruiting at 41 sites in 12 countries. Open to participants aged 2 Years to 50 Years. Per ClinicalTrials.gov, last updated 2026-09-29.
Sponsored by Ionis Pharmaceuticals, Inc. · Phase 3, Interventional, and Treatment
The purpose of this study is to evaluate the efficacy and safety of obudanersen in children and adults with Angelman syndrome caused by a deletion or mutation of the UBE3A gene.
This is a Phase 3, randomized, double-blind, placebo-controlled study in people with Angelman syndrome. The study will consist of 4 periods: a screening period of up to 28 days, an approximate 60-week double blind, placebo-controlled treatment period, followed by an approximate 25-month Long-Term Extension (LTE) treatment period, and an approximate 8-month Post-LTE follow-up period. The study will be comprised of 2 cohorts. Cohort 1 will include pediatric participants, aged 2 to less than (\<)18 years old and serve as the population for evaluation of primary and secondary outcome measures; Cohort 2 will include adult participants, aged 18 to ≤50 years old. Participants will be randomized 1:1 to 80 mg obudanersen or placebo during the double-blind placebo-controlled treatment period. Participants from both cohorts completing the placebo-controlled treatment period will be eligible to transition into the LTE Treatment Period wherein all trial participants will receive obudanersen. Participant, Caregiver, Investigator and Sponsor will remain blinded to the obudanersen dose administered to participants during the LTE.
The study initiated in 2024 with three dosing groups (40 mg obudanersen, 80 mg obudanersen, and placebo). Following additional review of data from the ongoing Phase 1/2 trial of obudanersen (HALOS), REVEAL was amended in December 2025 to its current form as a two-arm study: 80 mg obudanersen and placebo. Following the amendment, participants who were randomized to receive 40 mg obudanersen will be transitioned to receive 80 mg obudanersen.
52 studies on the registry are indexed under Angelman Syndrome; 16 are open to participants now.
This study's enrollment of 156 is above the median of 66 across 29 interventional studies indexed under Angelman Syndrome.
Browse Angelman Syndrome studies →Ionis Pharmaceuticals, Inc. is the lead sponsor of 118 studies on the registry; 10 are open to participants now.
Of its 49 completed or terminated interventional studies of FDA-regulated products, 22 (45%) have results posted.
Counted across the registry records on this site, refreshed daily.
Key Inclusion Criteria:
Key Exclusion Criteria:
Other inclusion/exclusion criteria may apply.
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.
Judged by the study doctor to matter for your health or for the study. It is a doctor’s decision, so ask the study team if you are unsure whether something counts.
A reason a treatment, test or procedure should not be given to a particular person, such as an allergy, another illness or a medicine they take.
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.
Clinically significant
Judged by the study doctor to matter for your health or for the study. It is a doctor’s decision, so ask the study team if you are unsure whether something counts.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Contraindication
A reason a treatment, test or procedure should not be given to a particular person, such as an allergy, another illness or a medicine they take.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Participants (aged 2 to \<18 years old) will be administered obudanersen 80 mg via intrathecal (IT) injection every 12 weeks during the double blind and LTE treatment periods.
Drug: obudanersen
Participants (aged 2 to \<18 years old) will be administered obudanersen matching placebo via IT injection every 12 weeks during the double-blind treatment period and then administered obudanersen 40 mg or 80 mg every 12 weeks during the LTE treatment period.
Drug: Placebo
Participants (aged 18 to ≤50 years old) will be administered obudanersen 80 mg via IT injection every 12 weeks during the double blind and LTE treatment periods.
Drug: obudanersen
Participants (aged 18 to ≤50 years old) will be administered obudanersen matching placebo via IT injection every 12 weeks during the double-blind treatment period and then randomized to obudanersen 40 mg or 80 mg every 12 weeks during the LTE treatment period.
Drug: Placebo
obudanersen will be administered by IT injection.
Also known as: ION582
obudanersen matching placebo will be administered by IT injection.
Change in Performance on the Expressive Communication Subdomain Raw Score of the Bayley Scales for Infant and Toddler Development-4 (Bayley-4) Without Caregiver Input in Cohort 1
The Bayley-4 is a performance-based assessment of developmental functioning across communication, cognition, and motor skills. The expressive communication subdomain of communication measures preverbal and verbal communication. The total raw score reflects the sum of all the item scores within the expressive communication subdomain, with higher scores reflecting greater expressive communication ability.
Time frame: Baseline and Week 52
Change in Bayley Scales for Infant and Toddler Development-4 (Bayley-4): Cognition Subdomain Raw Score Without Caregiver Input
The Bayley-4 is a performance-based assessment of developmental functioning across communication, cognition, and motor skills. The cognitive subdomain measures learning, memory and concept formation. The total raw score reflects the sum of all the item scores within the expressive communication subdomain, with higher scores reflecting greater cognitive ability.
Time frame: Baseline and Week 52
Change in Symptoms of Angelman Syndrome -Clinician Global Impression of Change (SAS-CGI-C): Overall AS
The SAS-CGI-C for Overall AS is a disease-specific clinician-reported outcome assessment measure for Angelman syndrome. The clinicians rate their overall impression of the change of the participant's Angelman syndrome symptoms utilizing a 7-point scale, ranging from "very much improved" (1) to "very much worse" (7).
Time frame: Baseline and Week 52
Change in Vineland Adaptive Behavior Scale-3 (Vineland-3): Receptive Communication Subdomain Raw Score
The Vineland-3 assesses adaptive behaviors across 4 domains via a semi-structured interview between a trained clinician and the caregiver of the participant with AS. The receptive communication subdomain of communication measures the participant's ability to attend, understand, and respond appropriately to information from others. The total raw score reflects the sum of all the item scores within the receptive communication subdomain, with higher scores reflecting greater receptive communication ability.
Time frame: Baseline and Week 52
Change in Vineland Adaptive Behavior Scale-3 (Vineland-3): Daily Living Skills, Personal Subdomain Raw Score
The Vineland-3 assesses adaptive behaviors across 4 domains via a semi-structured interview between a trained clinician and the caregiver of the participant with AS. The Personal subdomain of the Daily Living Skills domain measures the participant's self-sufficiency in such areas as eating, dressing, washing, hygiene, and health care. The total raw score reflects the sum of all the item scores within the Personal subdomain, with higher scores reflecting greater ability.
Time frame: Baseline and Week 52
Change in Symptoms of Angelman Syndrome - Clinician Global Impression of Change (SAS-CGI-C): Sleep Problems
The SAS-CGI-C for Sleep Problems is a disease-specific clinician-reported outcome assessment measure for Angelman syndrome. The clinicians rate their overall impression of the change in the participant's sleep problems utilizing a 7-point scale, ranging from "very much improved" (1) to "very much worse" (7).
Time frame: Baseline and Week 52
Change in Bayley Scales for Infant and Toddler Development-4 (Bayley-4): Fine Motor Subdomain Raw Score Without Caregiver Input
The Bayley-4 is a performance-based assessment of developmental functioning across communication, cognition, and motor skills. The Fine Motor subdomain of communication measures motor abilities such as reaching, object manipulation, and grasping. The total raw score reflects the sum of all the item scores within the fine motor subdomain, with higher scores reflecting greater fine motor ability.
Time frame: Baseline to Week 52
Change in Observer-Reported Communication Ability (ORCA): Overall Emerging T Score
The ORCA measure assesses, from the caregiver's perspective, the communication ability of individuals with neurodevelopmental disorders, like Angelman syndrome. This questionnaire assesses expressive, receptive, and pragmatic communication. The ORCA measure produces a single score that is an estimate of an individual's overall level of communication ability, with higher T-scores reflecting greater communication ability.
Time frame: Baseline and Week 52
Percentage of Participants with Treatment-emergent Adverse Events (TEAEs) and Serious Adverse Events (SAEs)
Time frame: Up to Week 52
Change in Vital Signs and Clinical Laboratory Results
Time frame: Baseline and Week 52
Plan to share: Yes — Ionis may share anonymized individual participant data, aggregated clinical data, and other types of data that support the results in this study. Data requests from qualified researchers will be considered once all three of the following criteria are met: (1) 12 months from marketing approval of the study drug in both the United States and European Union; (2) 18 months from conclusion of the study; and (3) 6 months from publication of study article. Access would be via a secure environment and is contingent upon approval of a research proposal and entry into an appropriate data use agreement. Requests to access data can be submitted via the website https://vivli.org/ourmember/ionis/.
Data sharing details ↗ · vivli.org
No publications or documents are linked to this record.
From the registry record's own update history. This site started tracking changes on Sep 25, 2026; for anything earlier, see the record history on ClinicalTrials.gov ↗
This study is active, not recruiting, as verified in Sep 2026. You cannot join it, but the record below documents what was studied.
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Studies of the drug tested here: Obudanersen