MVX-220
An investigational treatment for Angelman Syndrome.
Drug facts
The same compound appears under different names depending on the context. Here is how to identify MVX-220 wherever you encounter it, plus the key facts at a glance.
- Generic name
- MVX-220
- Development code
- MVX-220
- Drug class
- AAV gene therapy
- Manufacturer
- MavriX Bio
- How it's taken
- One-time injection at the base of the skull (cisterna magna), in a trial only
An investigational one-time gene therapy from MavriX Bio that delivers a working copy of the UBE3A gene to brain cells in Angelman syndrome.
It is in the Phase 1/2 ASCEND-AS trial, which is recruiting at 3 US hospitals and mainly measures safety [5]. It is not FDA approved, and no results have been published.
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How MVX-220 works
Angelman syndrome happens when brain cells cannot make enough UBE3A protein from the mother's copy of the UBE3A gene. MVX-220 uses a harmless virus shell, an adeno-associated virus called AAVhu68, to carry a new working copy of the human UBE3A gene into neurons [1] [4]. MavriX describes it as a one-time gene replacement approach [4]. It was developed at the University of Pennsylvania with funding from FAST, the Foundation for Angelman Syndrome Therapeutics [1].
Clinical trial results
ASCEND-AS (NCT07181837) is an open-label Phase 1/2 trial with no control group for about 12 people. Adults aged 18 to 50 are treated first, and children aged 4 to 8 follow only after a safety board reviews the adults; an optional third group covers ages 4 to 50. It enrolls people whose Angelman syndrome comes from a full maternal UBE3A deletion, uniparental disomy or an imprinting defect, who walk on their own and whose seizure medicines are stable; people whose Angelman syndrome comes from a UBE3A point mutation are not included.
People who had an antisense medicine in the past year or any earlier gene therapy are excluded, as are people with liver or blood test results outside the normal range, a personal or family history of HLH, a dangerous immune overreaction, or of complement disorders, or severe autoimmune disease. ClinicalTrials.gov lists it as recruiting at Cedars-Sinai in Los Angeles, Rush University Medical Center in Chicago and Boston Children's Hospital, with follow-up lasting 5 years [5]. MavriX announced on November 6, 2025 that the first patient had been dosed [3].
Main registered trial: NCT07181837 on ClinicalTrials.gov. Check it for the current status, sites and contacts before asking about enrollment.
Side effects and safety
No safety results have been published. AAV gene therapies can set off an immune response to the virus shell, and the trial gives steroids before and briefly during treatment to lower that risk [5]. The trial's main purpose is to count side effects, serious side effects and side effects of special interest over 104 weeks [5]. 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 MVX-220
Given once as an injection into the cisterna magna, a fluid-filled space at the base of the skull, with steroids before and briefly during the study [5]. The dose has not been disclosed.
Development history
The FDA cleared MavriX's application to start human testing in May 2025 [1] and granted Fast Track designation in September 2025 [2]. MavriX reported orphan drug designation in November 2025 [3] and FDA Rare Pediatric Disease designation on October 1, 2026 [4]. MavriX is a portfolio company of AS2Bio, FAST's accelerator, and licensed MVX-220 after a research collaboration with GEMMABio [3].
Explore Angelman Syndrome trials
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Common questions about MVX-220
▸What is MVX-220?
An investigational one-time gene therapy from MavriX Bio that delivers a working copy of the UBE3A gene to brain cells in Angelman syndrome. It is in the Phase 1/2 ASCEND-AS trial, which is recruiting at 3 US hospitals and mainly measures safety [5]. It is not FDA approved, and no results have been published.
▸How does MVX-220 work?
Angelman syndrome happens when brain cells cannot make enough UBE3A protein from the mother's copy of the UBE3A gene. MVX-220 uses a harmless virus shell, an adeno-associated virus called AAVhu68, to carry a new working copy of the human UBE3A gene into neurons [1] [4]. MavriX describes it as a one-time gene replacement approach [4]. It was developed at the University of Pennsylvania with funding from FAST, the Foundation for Angelman Syndrome Therapeutics [1].
▸What are the side effects of MVX-220?
No safety results have been published. AAV gene therapies can set off an immune response to the virus shell, and the trial gives steroids before and briefly during treatment to lower that risk [5]. The trial's main purpose is to count side effects, serious side effects and side effects of special interest over 104 weeks [5]. No clinical hold has been reported.
▸How is MVX-220 taken?
Given once as an injection into the cisterna magna, a fluid-filled space at the base of the skull, with steroids before and briefly during the study [5]. The dose has not been disclosed.
▸Is MVX-220 FDA approved?
MVX-220 is currently in phase 2 clinical trials for Angelman Syndrome. It has not yet received FDA approval.
▸Is MVX-220 a one-time treatment for Angelman syndrome?
It is designed as a single injection, and it is still investigational.
How: an injection into the cisterna magna at the base of the skull, with steroids around treatment.
Results: none published yet; the current trial mainly measures safety.
Source: ClinicalTrials.gov NCT07181837; MavriX Bio release, October 1, 2026.
▸Who can join the MVX-220 ASCEND-AS trial?
Adults 18 to 50 and children 4 to 8 with Angelman syndrome from a full maternal UBE3A deletion, uniparental disomy or an imprinting defect, not a UBE3A mutation.
Other requirements: walks independently, stable seizure medicines, no antisense medicine in the past year, no earlier gene therapy, and liver and blood tests in the normal range.
Where: Cedars-Sinai, Rush University Medical Center and Boston Children's Hospital, all listed as recruiting.
Source: ClinicalTrials.gov NCT07181837, updated July 24, 2026.
▸Has MVX-220 shown results?
Not yet. MavriX has not released any efficacy or safety data.
Status: MavriX announced the first dosing on November 6, 2025, and the trial's main results are estimated for March 2028.
Source: MavriX Bio release, November 6, 2025; ClinicalTrials.gov 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.
- MavriX Bio (PR Newswire) · 2025-05-12. MavriX Bio announces FDA clearance of IND application to initiate first-in-human study of gene therapy for Angelman syndrome. https://www.prnewswire.com/news-releases/mavrix-bio-announces-fda-clearance-of-ind-application-to-initiate-first-in-human-study-of-gene-therapy-for-angelman-syndrome-302451763.html
- MavriX Bio, issued by AS2 Bio (PR Newswire) · 2025-09-22. MavriX Bio receives FDA Fast Track designation for MVX-220 for treatment of Angelman syndrome. https://www.prnewswire.com/news-releases/mavrix-bio-receives-fda-fast-track-designation-for-mvx-220-for-treatment-of-angelman-syndrome-302562593.html
- MavriX Bio (BioSpace wire copy) · 2025-11-06. MavriX Bio Announces First Patient Dosed in ASCEND-AS Trial of MVX-220, Investigational Gene Therapy for Angelman Syndrome. https://www.biospace.com/press-releases/mavrix-bio-announces-first-patient-dosed-in-ascend-as-trial-of-mvx-220-investigational-gene-therapy-for-angelman-syndrome
- MavriX Bio (Newswise copy) · 2026-10-01. MavriX Bio announces FDA Rare Pediatric Disease designation for investigational MVX-220 for the treatment of Angelman syndrome. https://www.newswise.com/articles/mavrix-bio-announces-fda-rare-pediatric-disease-designation-for-investigational-mvx-220-for-the-treatment-of-angelman-syndrome
- ClinicalTrials.gov. A Phase 1/2 Study of the Safety and Efficacy of MVX-220 in Angelman Syndrome (ASCEND-AS). https://clinicaltrials.gov/study/NCT07181837