Obudanersen
An investigational treatment for Angelman Syndrome.
Drug facts
The same compound appears under different names depending on the context. Here is how to identify Obudanersen wherever you encounter it, plus the key facts at a glance.
- Generic name
- Obudanersen
- Development code
- ION582
- Drug class
- Antisense oligonucleotide (ASO)
- Manufacturer
- Ionis Pharmaceuticals
- How it's taken
- Lumbar puncture (spinal injection) every 12 weeks, in trials only
An investigational antisense medicine from Ionis, given by spinal injection every 12 weeks, that aims to restore the UBE3A protein missing in Angelman syndrome.
It is in 2 Phase 3 trials: REVEAL, for people whose Angelman syndrome comes from a UBE3A deletion or mutation, and CHAMPION, for people with uniparental disomy or an imprinting defect [6] [7]. It is not FDA approved.
We'll email you when the FDA acts on Obudanersen and when new trials for Angelman Syndrome open. Unsubscribe anytime.
- Trial Alerts, when a new trial opens or a trial changes
- Disease Updates, FDA decisions and condition news, usually 1 or 2 emails a month
We never share your email. Unsubscribe anytime. Privacy policy · Check any health site
How Obudanersen works
Brain cells normally use only the mother's copy of the UBE3A gene, because a long RNA strand called the UBE3A antisense transcript keeps the father's copy switched off. In Angelman syndrome the mother's copy is missing or does not work, so brain cells make too little UBE3A protein [9]. Obudanersen is a short strand of genetic material designed to block that antisense transcript, so the father's copy can switch on and the cells can make UBE3A again [1] [9]. It is designed to target the cause of the disease rather than a single symptom such as seizures.
Clinical trial results
REVEAL (NCT06914609) is a randomized, placebo-controlled Phase 3 trial in people aged 2 to 50 with a UBE3A deletion or mutation. Its main measure is the change in expressive communication, how well a child gets ideas across, on the Bayley-4, a standard test of child development, after 52 weeks in children aged 2 to under 18 [6]. Ionis said on July 6, 2026 that the children's group had finished enrolling with 136 participants, and that first results are expected in the second half of 2027 [1].
ClinicalTrials.gov lists 156 people enrolled and the trial as no longer recruiting [6].
CHAMPION (NCT07782827) is an open-label Phase 3 trial, with no placebo, for about 30 people aged 2 to 50 whose Angelman syndrome comes from paternal uniparental disomy or an imprinting defect, the genetic types REVEAL leaves out. ClinicalTrials.gov lists it as recruiting at UNC Chapel Hill, with a start date of September 30, 2026 [7].
The earlier Phase 1/2 HALOS study (NCT05127226) was open-label, meaning everyone knew they were getting the drug, with no placebo group. Ionis reported that 97% of people in the medium and high dose groups improved on a clinician-rated scale of overall Angelman symptoms [3]. Without a placebo group, that result cannot show how much of the change came from the drug. HALOS is still running its long-term extension and is not recruiting [8].
Main registered trial: NCT06914609 on ClinicalTrials.gov. Check it for the current status, sites and contacts before asking about enrollment.
Side effects and safety
Ionis has said ION582 showed favorable safety and tolerability at all dose levels in the completed first part of its Phase 1/2 HALOS study [2]. Ionis has not published counts of side effects or serious side effects, and no peer-reviewed safety paper exists yet. The injection is a lumbar puncture, and the trials require that a person can be sedated or given general anesthesia for it without a breathing tube [6]. No clinical hold has been reported.
This is not a complete list of side effects. Talk to your doctor or pharmacist about what to expect and when to seek medical attention.
Taking Obudanersen
Given by intrathecal injection, a lumbar puncture into the fluid around the spinal cord, every 12 weeks. The Phase 3 dose is 80mg [6] [5]. REVEAL first tested 40mg and 80mg and was changed in December 2025 to compare 80mg with placebo, with people on 40mg moved to 80mg [6].
Development history
Ionis developed ION582 and began the HALOS study in December 2021 [8]. The FDA granted orphan drug, rare pediatric disease and Fast Track designations [5] [1], and Ionis announced FDA Breakthrough Therapy designation on September 9, 2025 [4]. The European Medicines Agency also granted orphan designation [1]. The first person in REVEAL was dosed in June 2025 [2]. Ionis now uses the name obudanersen in its releases and on ClinicalTrials.gov [1].
Explore Angelman Syndrome trials
Other Angelman Syndrome treatments
Common questions about Obudanersen
▸What is Obudanersen?
An investigational antisense medicine from Ionis, given by spinal injection every 12 weeks, that aims to restore the UBE3A protein missing in Angelman syndrome. It is in 2 Phase 3 trials: REVEAL, for people whose Angelman syndrome comes from a UBE3A deletion or mutation, and CHAMPION, for people with uniparental disomy or an imprinting defect [6] [7]. It is not FDA approved.
▸How does Obudanersen work?
Brain cells normally use only the mother's copy of the UBE3A gene, because a long RNA strand called the UBE3A antisense transcript keeps the father's copy switched off. In Angelman syndrome the mother's copy is missing or does not work, so brain cells make too little UBE3A protein [9]. Obudanersen is a short strand of genetic material designed to block that antisense transcript, so the father's copy can switch on and the cells can make UBE3A again [1] [9]. It is designed to target the cause of the disease rather than a single symptom such as seizures.
▸What are the side effects of Obudanersen?
Ionis has said ION582 showed favorable safety and tolerability at all dose levels in the completed first part of its Phase 1/2 HALOS study [2]. Ionis has not published counts of side effects or serious side effects, and no peer-reviewed safety paper exists yet. The injection is a lumbar puncture, and the trials require that a person can be sedated or given general anesthesia for it without a breathing tube [6]. No clinical hold has been reported.
▸How is Obudanersen taken?
▸Is Obudanersen FDA approved?
Obudanersen is currently in phase 3 clinical trials for Angelman Syndrome. It has not yet received FDA approval.
▸Is obudanersen (ION582) FDA approved for Angelman syndrome?
No. Obudanersen is investigational and available only in clinical trials.
Phase: REVEAL and CHAMPION, both Phase 3 trials.
Next step: Ionis expects first REVEAL results in the second half of 2027.
Source: Ionis release, July 6, 2026; ClinicalTrials.gov NCT06914609 and NCT07782827.
▸How is ION582 given and how often?
By lumbar puncture, an injection into the fluid around the spinal cord, every 12 weeks.
Dose: the Phase 3 trials use 80mg.
Sedation: the trials require that a person can be sedated or anesthetized for the injection without a breathing tube.
Source: ClinicalTrials.gov NCT06914609; Ionis neurology pipeline page.
▸Can someone with UPD or an imprinting defect join an ION582 trial?
They may qualify for CHAMPION. REVEAL is only for people with a UBE3A deletion or mutation and excludes mosaic findings.
CHAMPION: open-label Phase 3 for paternal uniparental disomy or an imprinting defect, ages 2 to 50, about 30 people.
Not eligible: anyone who has had an antisense medicine or gene therapy.
Where: ClinicalTrials.gov lists UNC Chapel Hill as recruiting.
Source: ClinicalTrials.gov NCT07782827, updated October 20, 2026; NCT06914609.
▸How is obudanersen different from a gene therapy such as MVX-220?
Obudanersen switches on the father's own UBE3A gene and is given every 12 weeks; MVX-220 delivers a new copy of UBE3A once.
Obudanersen: an antisense medicine by lumbar puncture, in Phase 3.
MVX-220: an AAV gene therapy by a single injection at the base of the skull, in a Phase 1/2 safety trial.
Trials: joining one can rule a person out of the other; REVEAL and CHAMPION exclude anyone who has had gene therapy, and the MVX-220 trial excludes anyone who had an antisense medicine in the past year.
No trial has compared them.
Source: ClinicalTrials.gov NCT06914609, NCT07782827 and NCT07181837.
Sources and references
Every factual claim on this page is drawn from the public sources listed below. Click any reference to open the original document.
- Ionis Pharmaceuticals (BioSpace wire copy) · 2026-07-06. Ionis completes enrollment in pivotal cohort of the Phase 3 REVEAL study evaluating obudanersen in Angelman syndrome. https://www.biospace.com/press-releases/ionis-completes-enrollment-in-pivotal-cohort-of-the-phase-3-reveal-study-evaluating-obudanersen-in-angelman-syndrome
- Ionis Pharmaceuticals (BioSpace wire copy) · 2025-06-11. First patient dosed in pivotal Phase 3 REVEAL clinical study of ION582 in Angelman syndrome. https://www.biospace.com/press-releases/first-patient-dosed-in-pivotal-phase-3-reveal-clinical-study-of-ion582-in-angelman-syndrome
- Ionis Pharmaceuticals (BioSpace wire copy) · 2024-11-06. Ionis announces pivotal Phase 3 trial design for ION582 in Angelman syndrome. https://www.biospace.com/press-releases/ionis-announces-pivotal-phase-3-trial-design-for-ion582-in-angelman-syndrome
- Ionis Pharmaceuticals (Business Wire) · 2025-09-09. Ionis receives U.S. FDA Breakthrough Therapy designation for ION582 in Angelman syndrome. https://www.businesswire.com/news/home/20250909085802/en/Ionis-receives-U.S.-FDA-Breakthrough-Therapy-designation-for-ION582-in-Angelman-syndrome
- Ionis Pharmaceuticals. Investigational RNA-Targeted Drug Discovery Pipeline | IONIS. https://neurology.ionis.com/our-pipeline
- ClinicalTrials.gov. REVEAL: A Phase 3 Study of Obudanersen (ION582) in Angelman Syndrome. https://clinicaltrials.gov/study/NCT06914609
- ClinicalTrials.gov. CHAMPION: A Study to Evaluate the Efficacy and Safety of Obudanersen (ION582) in Children and Adults With Angelman Syndrome (AS). https://clinicaltrials.gov/study/NCT07782827
- ClinicalTrials.gov. HALOS: A Safety, Tolerability, Pharmacokinetics and Pharmacodynamics Study of Multiple Ascending Doses of ION582 in Participants With Angelman Syndrome. https://clinicaltrials.gov/study/NCT05127226
- GeneReviews, NCBI Bookshelf. Angelman Syndrome. https://www.ncbi.nlm.nih.gov/books/NBK1144/