ClinicalTrials.gov record NCT07181837

A Phase 1/2 Study of the Safety and Efficacy of MVX-220 in Angelman Syndrome

Record copied from ClinicalTrials.gov: Oct 10, 2026AI summaries generated: Aug 22, 2026

A Multi-Center, Open-label, Phase 1/2 Trial of the Safety and Efficacy of MVX-220 Gene Therapy Administered by Intra-Cisterna Magna Injection to Participants With Angelman Syndrome

StatusRecruitingThe study is currently enrolling participants. Only the study team can say whether a particular person can join.
Study typeInterventionalA study in which researchers assign participants to one or more interventions, such as a drug, procedure, device, behavioural programme or other approach, to measure their effects.
PhasePhase 1/2A study that combines safety and dose-finding (phase 1) with a first look at whether the treatment has an effect (phase 2).
Age4 years old to 50 years old
SexAll
LocationUnited States
AI summaryWhat this study is about, in plain languageShow ▾Hide ▴

AI-written from the registry record, not the study's own wording. May contain errors or omissions. Check the registry text on this page and the original record ↗ before acting on it.

This Phase 1/2 study evaluates the safety, tolerability, and efficacy of MVX-220 gene therapy in people with Angelman syndrome who have UBE3A deletion, uniparental disomy, or imprinting center defects. People are enrolled first, followed by children after a safety review; all participants receive a single dose given into the cisterna magna. Participants take steroids briefly around dosing and are followed for safety and outcomes for two years, then less frequent visits up to five years total.

What it is studying. The study is testing MVX-220, an investigational gene replacement intended to provide a functional UBE3A gene. It will collect safety information and measure effects on communication, development, adaptive behaviors, behavior problems, sleep, ambulatory ability, EEG features, and viral DNA levels in body fluids.

What the researchers hope to learn. To evaluate the safety and tolerability of MVX-220 and gather data on its effects over time. To measure changes in communication, developmental milestones, adaptive behavior, problem behaviors, sleep, ambulatory function, EEG parameters, and viral DNA shedding. To collect long-term safety and outcome data up to five years after dosing.

What this study is about

The study's own summary, as published on ClinicalTrials.gov. Underlined terms have a short explanation.

The purpose of this study is to evaluate the safety and efficacy of MVX-220 gene therapy in children and adults with Angelman syndrome with UBE3A gene deletion, uniparental disomy, or imprinting center defect genotypes.

Interventions being studied

Being studied in this trial does not mean the treatment or procedure is approved or available for this condition.

Genetic
  • MVX-220

Eligibility

The criteria exactly as listed on ClinicalTrials.gov. Only the study team can say whether they apply to you.

Inclusion criteria

  • The participant's parent/legal guardian must provide written informed consent.
  • Symptoms consistent with AS and documented genetic confirmation of one of the following genotypes resulting in a diagnosis of AS:
  • Full maternal UBE3A gene deletion causing AS in the region of 15q11.2-q13
  • Uniparental disomy
  • Imprinting center defect
  • The participant must be 18 to 50 years of age, inclusive (for adult participants), or 4 to 8 years of age, inclusive (for pediatric participants), at Screening.
  • The participant must have the ability to ambulate independently.
  • The participant must be on stable antiepileptic medications (with no changes within 1 month prior to the Screening visit, except for weight associated dose adjustments).
  • Key

Exclusion criteria

  • Clinically significant medical finding other than AS, that, in the judgment of the Investigator would make the participant unsuitable for participation.
  • Laboratory abnormalities including but not limited to:
  • Alanine aminotransferase (ALT) or aspartate aminotransferase (AST) > upper limit of normal (ULN)
  • Total and/or fractionated bilirubin (direct and/or indirect) > ULN
  • Gamma-glutamyl transferase (GGT) > ULN
  • Estimated glomerular filtration rate (eGFR) below the lower limit of normal (LLN) for age
  • Hemoglobin < 8 g/dL
  • White blood cell (WBC) count outside the normal range for age
  • Platelet count < LLN
  • Partial thromboplastin time (PTT) outside the reference range
  • PT/International normalized ratio (INR) outside the reference range
  • Any known history and/or family history of hemophagocytic lymphohistiocytosis (HLH)/macrophage activation syndrome (MAS) or multisystem inflammatory syndrome (MIS).
  • Any known history and/or family history of disordered complement function and/or complement gene mutation(s).
  • History of systemic lupus erythematous, Still's disease, rheumatoid arthritis, and/or other severe autoimmune conditions per judgment of the Investigator.
  • Any known history of thrombotic microangiopathy (TMA)/microangiopathic hemolytic anemia, or hypercoagulable conditions including, but not limited to, disseminated intravascular coagulation (DIC), deep venous thrombosis, and pulmonary embolism.
  • Current therapy with high dose immunosuppressants.
  • Prior or current treatment with an investigational drug within 6 months or 5-half-lives of the hospital admission whichever is longer.
  • Prior treatment with an antisense oligonucleotide within 1 year of hospital admission.
  • A history of gene therapy administration.
  • Any contraindication to ICM administration procedure, including contraindications to imaging, contrast use, anesthesia, or any condition that would increase the risk of adverse outcomes from the ICM procedure.
  • Any contraindication to glucocorticoid use

Study description and what participation involves

The study's detailed description, as published on ClinicalTrials.gov.

Detailed description from the registry

MVX-220 is an investigational gene replacement therapy intended to provide a functional copy of the UBE3A gene to individuals with Angelman syndrome. This study is designed to evaluate the safety, tolerability and efficacy of MVX-220 in participants with Angelman syndrome who have deletion, uniparental disomy, or imprinting center disorder genotypes. The study has 2 primary cohorts: Cohort 1 that includes adults followed by Cohort 2 that includes children. All patients will receive a single dose of MVX-220 administered by injection into the cisterna magna. There is no control group and all individuals will receive the gene therapy. An independent data safety monitoring board will review the safety information from Cohort 1 before individuals can be enrolled in Cohort 2. An optional cohort of adults and/or children (Cohort 3) may be enrolled based on a review of data from Cohorts 1 and 2. All patients will be required to take steroids before and for a brief period during the study to help mitigate the risk of immune response to the gene therapy. Patients will be followed for safety and efficacy for an initial 2-year period post-treatment and then transition to less frequent monitoring schedule for an additional 3 years. The total duration of follow up in the study is 5 years.

AI summaryWhat participation may involve, in plain languageShow ▾Hide ▴

AI-written from the registry record, not the study's own wording. May contain errors or omissions. Check the registry text on this page and the original record ↗ before acting on it.

Participants receive a single dose of the investigational gene therapy MVX-220 given by an injection into the cisterna magna (an invasive procedure into the fluid space around the base of the brain). All participants will take steroids before and for a short time during the study. Study visits include safety checks (physical exams, vital signs, laboratory tests, and ECG), EEGs, developmental testing (Bayley-4), a clinician interview about adaptive behavior (VABS-3), caregiver questionnaires (for example ORCA, ABC-C, QI‑Disability, and a sleep diary), continuous ambulatory monitoring with a Syde® wearable device, and collection of samples to measure viral DNA in CSF, blood, urine, and feces. Participants are followed closely for safety and efficacy for 2 years after treatment, then monitored less frequently for an additional 3 years (total follow-up 5 years).

How the study is structured. This is an open-label, non-randomized Phase 1/2 interventional study with a single treatment group (no control). There are separate cohorts: adults first (Cohort 1), then children (Cohort 2), and a possible optional Cohort 3. Everyone receives a single dose of MVX-220 delivered by injection into the cisterna magna. An independent safety board reviews adult data before children are enrolled. Short steroid treatment is given around dosing to reduce immune risk. Participants are followed closely for about 2 years and then less frequently for a total of 5 years.

Questions you could ask

These questions are suggestions for a conversation with the study team or your own clinician, not advice.

  • This is an early-phase study, mainly about safety and dose. What is already known about this treatment?
  • The listed sites are in United States. Is any of them reachable for me, and does the study help with travel?
  • Which of the eligibility criteria would need to be checked with tests before I could join?

More on Angelman syndrome

Clinical trials11 trials listed for Angelman syndromeEvery trial the registry lists for Angelman syndrome, with recruitment status, phase and sites, updated from ClinicalTrials.gov.See all trials →Research updatesWhat changed in Angelman syndrome researchLatest monthly update: September 2026. Includes: Seizure frequency. New research summarized each month in plain language, with links to every source paper.Read the latest update →

Important dates

Study start
Oct 29, 2025
Primary completion
Mar 31, 2028 (estimated)
Study completion
May 31, 2031 (estimated)
Target enrollment
12 participants (estimated)
Last updated on registry
Jul 24, 2026
Data verified
Oct 10, 2026

Sponsor and research team

The lead sponsor funds and oversees the trial. A pharmaceutical or biotech company sponsor typically means the study is testing that company's drug or device; a hospital, university, or government agency usually indicates investigator-initiated or publicly funded research.

Lead sponsor
MavriX Bio, LLC

Central study contact

If you're interested in participating, the central contact can answer general questions about the study — including eligibility requirements and how to find a recruiting site near you. Actual eligibility is determined by the site's medical team.

Participating sites (3)

Terms used on this page · explanations by MedicalUpdates.ai

legal guardian
A person who is legally allowed to make decisions, including consent to research, on behalf of someone who cannot consent for themselves.
written informed consent
The process of explaining a study, including its risks and what participation involves, so that a person can decide freely whether to take part. Consent is usually documented in writing, and a participant can choose to leave the study later.
at Screening
The checks done before enrolment to see whether a person qualifies, such as tests, scans or a review of medical history.
upper limit of normal
The highest value of a blood test that a laboratory considers normal. Criteria such as '≤ 3 × ULN' mean the result must be no more than three times that value.
Estimated glomerular filtration rate
A blood-test estimate of how well the kidneys are filtering. Lower numbers mean reduced kidney function; many studies set a minimum value.
immunosuppressants
A medicine that reduces the activity of the immune system. Studies of autoimmune conditions often require a stable dose, a prior failure, or a washout of such medicines.
investigational drug
A treatment that is being tested and has not been approved for this use. It may be approved for a different condition. Being studied does not mean it works or is available outside the study.
half-lives
The time it takes for the amount of a drug in the body to fall by half. 'Five half-lives' is often used as the point at which a previous drug has essentially left the body.
Prior treatment
Treatment a person has already had for the condition. A 'line of therapy' is one course of treatment; studies often require, or limit, the number of prior lines.
contraindication
A reason a particular test or treatment should not be used for a person, for example a metal implant that rules out an MRI scan.
glucocorticoid
Steroid medicines, such as prednisone, that reduce inflammation. Studies often require a stable dose at entry or measure whether the study treatment allows the dose to be reduced.
Key Inclusion Criteria
The conditions a person must meet to be considered for the study, for example a confirmed diagnosis, an age range or a test result.
Key Exclusion Criteria
The conditions that rule a person out even if they meet the inclusion criteria, for example other illnesses, certain medicines or pregnancy.
Cohort
A group of people who share a characteristic, such as a diagnosis, and are studied together. 'Prospective' means they are followed forward from enrolment; 'retrospective' means existing records are reviewed.
control group
The group the study treatment is compared with. It may receive a placebo, an existing treatment (active comparator), a sham procedure, or no intervention.
follow up
The period after treatment or enrolment during which participants are observed or contacted, for example to record side effects or outcomes.

The study record on this page is reproduced from ClinicalTrials.gov, a database of the U.S. National Library of Medicine, where it was submitted by the study sponsor. MedicalUpdates.ai does not own this content, is not affiliated with or endorsed by ClinicalTrials.gov, NIH, or the U.S. Government, and does not verify the record. Plain-language notes, the glossary and the questions above are added by this site; text in the boxes marked "AI summary" was written by an AI model and may contain errors. Registry records change over time. Check the original record for the current version and discuss eligibility or participation with a qualified healthcare professional.

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