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GTX-102 treatment for people with Angelman syndrome

A Phase 2, Open-label, Basket Study Investigating the Safety and Efficacy of GTX-102 in Adult and Pediatric Subjects With Deletion- or Nondeletion-type Angelman Syndrome

Phase 2 Interventional Ultragenyx Pharmaceutical Inc · NCT07157254

This trial will test whether GTX-102 is safe and helpful for people with Angelman syndrome across different age groups and genetic types.

Quick facts

PhasePhase 2
Study typeInterventional
Enrollment60 (estimated)
Ages1 Year to 64 Years
SexAll
SponsorUltragenyx Pharmaceutical Inc Industry-sponsored
Locations22 sites (Los Angeles, California and 21 other locations)
Trial IDNCT07157254 on ClinicalTrials.gov

What this trial studies

This Phase 2 basket trial tests GTX-102 in participants with Angelman syndrome across multiple genotypes and age ranges using four subprotocols (A–D). Subprotocols A, B, and C are open-label single-arm cohorts, while subprotocol D randomizes participants 2:1 to GTX-102 or a No Treatment group; all arms follow Screening, Loading, and Maintenance periods. Key eligibility includes genetically confirmed Angelman syndrome with specific age and genotype windows per subprotocol, weight ≥8 kg, and acceptable platelet and clotting laboratory values. Participants who complete the assigned subprotocol may opt to continue treatment in a long-term extension study.

Who should consider this trial

Good fit: People with genetically confirmed Angelman syndrome who meet the age and genotype criteria for one of the subprotocols, weigh at least 8 kg, have acceptable platelet and clotting tests, and whose parent or guardian provides consent.

Not a fit: Patients outside the specified age or genotype groups, those with low platelets or significant clotting abnormalities, or those unable to comply with scheduled visits and procedures are unlikely to qualify or benefit.

Why it matters

Potential benefit: If successful, GTX-102 could provide a targeted therapy that improves neurological symptoms and daily functioning for people with Angelman syndrome.

How similar studies have performed: Related genetic- or antisense-based approaches for Angelman syndrome have shown promise in preclinical models, but confirmed clinical benefit in humans remains limited and is still being established.

Eligibility criteria

Show full inclusion / exclusion criteria 
Inclusion Criteria:

1. Signed informed consent from parent(s) or legal guardian(s)
2. Males and females of the following ages and genotypes at time of informed consent:

   1. Subprotocol A: ≥ 1 to \< 4 years of age with a genetically confirmed diagnosis of deletion-type Angelman syndrome
   2. Subprotocol B: ≥ 4 to \< 18 years of age with a genetically confirmed diagnosis of UPD/ICD Angelman syndrome
   3. Subprotocol C: ≥ 18 to \< 65 years of age with a genetically confirmed diagnosis of Angelman syndrome, any genotype
   4. Subprotocol D: ≥ 4 to \< 18 years of age with a genetically confirmed diagnosis of mutation-type Angelman syndrome
3. Weight ≥ 8 kg at Screening Visit
4. Platelet count, prothrombin time / international normalized ratio, and partial thromboplastin time \< 1.5x the upper limit of normal and platelets \> 75,000 cells/mm3 at the Screening Visit
5. Willing and able to comply with scheduled visits, drug administration plan, laboratory tests, and all study procedures, including lumbar puncture (LP) procedure, magnetic resonance imaging (MRI) and tolerating anesthesia without intubation
6. From the time of informed consent through to at least 6 months after the final dose of GTX-102, females of childbearing potential who are sexually active must use highly effective contraception or abstinence. Males are able to participate if they agree to remain abstinent (refrain from heterosexual intercourse) or use acceptable contraceptive methods during the study and for at least 3 months after the final dose of GTX-102

Exclusion Criteria:

1. Any change in medications or diet/supplements intended to treat symptoms of Angelman Syndrome (eg, sleeping aids, antiseizure medications, supplements, dietary change including ketogenic or low-glycemic index diet, other) within the month prior to the Screening Visit (excluding weight-based adjustments)
2. Any condition that creates an increased risk of unsuccessful lumbar puncture
3. Current or expected concomitant use of drugs that increase the risk of bleeding (eg, heparin, low molecular weight heparin, platelet inhibitors)
4. Known hypersensitivity to GTX-102 or its excipients or required premedication that, in the judgment of the Investigator, places the subject at increased risk for adverse effects
5. Presence or history of any condition, lab abnormality, or infection that, in the judgment of the Investigator, would interfere with study participation, pose undue safety risk, or would confound interpretation of results
6. Pregnant or breastfeeding or planning to become pregnant (self or partner) at any time during the study
7. Use of any investigational product or investigational medical device within 6 months or 5 half-lives prior to the Screening Visit, or any prior use of gene therapy or an ASO regardless of length of time since last use
8. Concurrent participation in any interventional study

Where this trial is running

Los Angeles, California and 21 other locations

Study contacts

How to participate

  1. Review the eligibility criteria above with your treating physician.
  2. Visit the official trial page on ClinicalTrials.gov for the most current contact information and recruitment status.
  3. Contact the listed study coordinator or principal investigator to request pre-screening. Pre-screening is free and never obligates you to enroll.
View on ClinicalTrials.gov → Find more trials like this →
Conditions Angelman Syndrome
Last reviewed 2026-06-13 by the Find a Trial editorial team. Information on this page is for educational purposes and is not medical advice. Always consult qualified healthcare professionals about clinical trial participation.