Phase 3 Efficacy and Safety Study of GTX-102 in Pediatric Subjects With Angelman Syndrome (AS) (Aspire)

November 2, 2026 updated by: Ultragenyx Pharmaceutical Inc

A Phase 3, Randomized, Double-blind, Sham-controlled Study Investigating the Efficacy and Safety of GTX-102 in Pediatric Subjects With Angelman Syndrome

The primary objective of this study is to evaluate the effect of GTX-102 in cognitive function in participants with deletion-type Angelman Syndrome (AS).

Study Overview

Status

Status

Indicates the current recruitment status or the expanded access status.
Terminated

Conditions

Conditions

The disease, disorder, syndrome, illness, or injury that is being studied. On ClinicalTrials.gov, conditions may also include other health-related issues, such as lifespan, quality of life, and health risks.

Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.

Study Type

Study Type

Describes the nature of a clinical study. Study types include interventional studies (also called clinical trials), observational studies (including patient registries), and expanded access.
Interventional

Enrollment (Actual)

Enrollment

The number of participants in a clinical study. The "anticipated" enrollment is the target number of participants that the researchers need for the study.
129

Phase

Phase

The stage of a clinical trial studying a drug or biological product, based on definitions developed by the U.S. Food and Drug Administration (FDA). The phase is based on the study's objective, the number of participants, and other characteristics. There are five phases: Early Phase 1 (formerly listed as Phase 0), Phase 1, Phase 2, Phase 3, and Phase 4. Not Applicable is used to describe trials without FDA-defined phases, including trials of devices or behavioral interventions.
  • Phase 3

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Locations

  • Canada
      • Vancouver, Canada, V6H 3V4
        • British Columbia Children's Hospital
    • Quebec
      • Montreal, Quebec, Canada, H4A3J1
        • McGill University Health Centre
  • Germany
      • Hamburg, Germany, 20251
        • Universitaetsklinikum Hamburg-Eppendorf
      • Leipzig, Germany, 04155
        • University of Leipzig
      • Munich, Germany, 80336
        • Haunersche Kinderklinik
  • Japan
      • Osaka, Japan, 543-0021
        • Osaka City General Hospital
      • Sapporo, Japan, 060-8648
        • Hokkaido University Hospital
    • Aichi-ken
      • Nagoya, Aichi-ken, Japan, 467-0001
        • Nagoya City University Graduate School of Medical Sciences
  • Poland
      • Gdansk, Poland, 80211
        • Medical University of Gdańsk
      • Lodz, Poland, 93-338
        • Polish Mothers Memorial Institute
  • Spain
      • Barcelona, Spain, 08950
        • Hospital Sant Joan de Deu
      • Barcelona, Spain, 08208
        • Hospital Universitario Parc Tauli
      • Madrid, Spain, 28222
        • Hospital Universitario Puerta de Hierro
      • Seville, Spain, 41013
        • Hospital Universitario Virgen del Rocio
  • United States
    • California
      • Los Angeles, California, United States, 90048
        • Cedars Sinai
      • San Diego, California, United States, 92123
        • UCSD, Rady Children's Hospital
      • San Francisco, California, United States, 94143
        • UCSF
    • Colorado
      • Aurora, Colorado, United States, 80045
        • Children's Hospital Colorado
    • Florida
      • Miami, Florida, United States, 33155
        • Nicklaus Children's Hospital
    • Georgia
      • Atlanta, Georgia, United States, 30329
        • Rare Disease Research
    • Illinois
      • Chicago, Illinois, United States, 60612
        • Rush University
    • Massachusetts
      • Boston, Massachusetts, United States, 02115
        • Boston Children's Hospital
    • Missouri
      • Kansas City, Missouri, United States, 64108
        • Children's Mercy
    • New York
      • New York, New York, United States, 10032
        • Columbia University Medical Center
    • North Carolina
      • Chapel Hill, North Carolina, United States, 27599
        • UNC Chapel Hill Pediatrics
      • Hillsborough, North Carolina, United States, 27278
        • Rare Disease Research
    • Texas
      • Austin, Texas, United States, 78723
        • The University of Texas
      • Dallas, Texas, United States, 75243
        • Carum Research Inc

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Eligibility Criteria

The key requirements that people who want to participate in a clinical study must meet or the characteristics they must have. Eligibility criteria consist of both inclusion criteria (which are required for a person to participate in the study) and exclusion criteria (which prevent a person from participating). Types of eligibility criteria include whether a study accepts healthy volunteers, has age or age group requirements, or is limited by sex.

Ages Eligible for Study

4 years to 17 years (Child)

Accepts Healthy Volunteers

No

Genders Eligible for Study

All

Description

Key Inclusion Criteria:

  • Signed informed consent from parent(s) or legal guardian(s)
  • Confirmed diagnosis of AS with genetic confirmation of full maternal ubiquitin-protein ligase E3A (UBE3A) gene deletion causing AS in the region of 15q11.2 q13
  • Able to ambulate independently, or with assistance at the Screening Visit (note, a child whose primary means of mobility is by wheelchair is excluded from the study)
  • Platelet count, prothrombin time / international normalized ratio, and partial thromboplastin time within 1.5x the normal limits at the Screening Visit
  • Willing and able to comply with scheduled visits, drug administration plan, laboratory tests, and all study procedures, including LP procedure, MRI, and tolerating anesthesia without intubation
  • 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

Key Exclusion Criteria:

  • Any change in medications or diet/supplements intended to treat symptoms of AS (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)
  • Any condition that creates an increased risk of unsuccessful LP
  • Current or expected concomitant use of drugs that increase the risk of bleeding (eg, heparin, low molecular weight heparin, platelet inhibitors)
  • Known hypersensitivity to GTX-102 or its excipients that, in the judgment of the Investigator, places the subject at increased risk for adverse effects
  • Presence or history of any condition, lab abnormality, or infection, that, in the judgement of the Investigator, would interfere with participation, pose undue safety risk, or would confound interpretation of results
  • Pregnant or breastfeeding or planning to become pregnant (self or partner) at any time during the study
  • 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 ASO regardless of duration since last administration
  • Concurrent participation in any interventional study

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Treatment
  • Allocation: Randomized
  • Interventional Model: Parallel Assignment
  • Masking: Quadruple

Arms and Interventions

Participant Group / Arm

Participant Group / Arm

A group or subgroup of participants in a clinical trial that receives a specific intervention/treatment, or no intervention, according to the trial's protocol.
Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.
Experimental: GTX-102

Participants will receive GTX-102 via lumbar puncture (LP) during both the double-blind and open-label period
Drug: GTX-102

antisense oligonucleotide

Other Names:
  • apazunersen
Sham Comparator: Sham-LP then GTX-102

Participants will receive sham procedure during the double-blind period and then will receive GTX-102 via LP during the open-label period
Drug: GTX-102

antisense oligonucleotide

Other Names:
  • apazunersen
Procedure: Sham-LP

Small needle prick on the lower back at the location where the LP injection is normally made

What is the study measuring?

Primary Outcome Measures

Primary Outcome Measures

In a clinical study's protocol, the planned outcome measure that is the most important for evaluating the effect of an intervention/treatment. Most clinical studies have one primary outcome measure, but some have more than one.
Outcome Measure
Time Frame
Change from Baseline in Bayley-4 Cognitive Raw Score Without Caregiver Input at Day 338
Time Frame: Baseline, Day 338
Baseline, Day 338

Secondary Outcome Measures

Secondary Outcome Measures

In a clinical study's protocol, a planned outcome measure that is not as important as the primary outcome measure for evaluating the effect of an intervention but is still of interest. Most clinical studies have more than one secondary outcome measure.
Outcome Measure
Time Frame
Net Response in Multidomain Responder Index (MDRI)
Time Frame: Day 338
Day 338
Change from Baseline in ABC-C Hyperactivity/Noncompliance Subscale Score at Day 338
Time Frame: Baseline, Day 338
Baseline, Day 338
Change from Baseline in Bayley-4 Receptive Communication Raw Score at Day 338
Time Frame: Baseline, Day 338
Baseline, Day 338
Number of Participants with Treatment Emergent Adverse Events (AEs) and Serious Adverse Events (SAEs), Severity of AEs and Relationship to Investigational Drug, Procedure, and Premedication
Time Frame: 2 Years
2 Years
Change from Baseline in Angelman Severity Assessment (ASA) Sleep Rating Raw Score at Day 338
Time Frame: Baseline, Day 338
Baseline, Day 338
Change from Baseline in Vineland Adaptive Behavior Scales-3 (Vineland-3) Receptive Communication Raw Score at Day 338
Time Frame: Baseline, Day 338
Baseline, Day 338
Change from Baseline in Vineland-3 Expressive Communication Raw Score at Day 338
Time Frame: Baseline, Day 338
Baseline, Day 338
Change from Baseline in Bayley-4 Gross Motor Raw Score at Day 338
Time Frame: Baseline, Day 338
Baseline, Day 338
Change from Baseline in ASA Gross Motor Rating at Day 338
Time Frame: Baseline, Day 338
Baseline, Day 338

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Sponsor

The organization or person who initiates the study and who has authority and control over the study.
Ultragenyx Pharmaceutical Inc

Investigators

Investigators

A researcher involved in a clinical study. Related terms include site principal investigator, site sub-investigator, study chair, study director, and study principal investigator.
  • Study Director: Medical Director, Ultragenyx Pharmaceuticals Inc.

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

Helpful Links

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

Study Start

The actual date on which the first participant was enrolled in a clinical study. The "anticipated" study start date is the date that the researchers think will be the study start date.
December 3, 2024

Primary Completion (Actual)

Primary Completion

The date on which the last participant in a clinical study was examined or received an intervention to collect final data for the primary outcome measure. Whether the clinical study ended according to the protocol or was terminated does not affect this date. For clinical studies with more than one primary outcome measure with different completion dates, this term refers to the date on which data collection is completed for all the primary outcome measures. The "anticipated" primary completion date is the date that the researchers think will be the primary completion date for the study.
July 10, 2026

Study Completion (Actual)

Study Completion

The date on which the last participant in a clinical study was examined or received an intervention/treatment to collect final data for the primary outcome measures, secondary outcome measures, and adverse events (that is, the last participant's last visit). The "anticipated" study completion date is the date that the researchers think will be the study completion date.
October 30, 2026

Study Registration Dates

First Submitted

First Submitted

The date on which the study sponsor or investigator first submitted a study record to ClinicalTrials.gov. There is typically a delay of a few days between the first submitted date and the record's availability on ClinicalTrials.gov (the first posted date).
September 24, 2024

First Submitted That Met QC Criteria

First Submitted That Met QC Criteria

The date on which the study sponsor or investigator first submits a study record that is consistent with National Library of Medicine (NLM) quality control (QC) review criteria. The sponsor or investigator may need to revise and submit a study record one or more times before NLM's QC review criteria are met. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
September 24, 2024

First Posted (Actual)

First Posted

The date on which the study record was first available on ClinicalTrials.gov after National Library of Medicine (NLM) quality control (QC) review has concluded. There is typically a delay of a few days between the date the study sponsor or investigator submitted the study record and the first posted date.
September 27, 2024

Study Record Updates

Last Update Posted (Actual)

Last Update Posted

The most recent date on which changes to a study record were made available on ClinicalTrials.gov. There may be a delay between when the changes were submitted to ClinicalTrials.gov by the study's sponsor or investigator (the last update submitted date) and the last update posted date.
November 3, 2026

Last Update Submitted That Met QC Criteria

Last Update Submitted That Met QC Criteria

The most recent date on which the study sponsor or investigator submitted changes to a study record that are consistent with National Library of Medicine (NLM) quality control (QC) review criteria. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
November 2, 2026

Last Verified

Last Verified

The most recent date on which the study sponsor or investigator confirmed the information about a clinical study on ClinicalTrials.gov as accurate and current. If a study with a recruitment status of recruiting; not yet recruiting; or active, not recruiting has not been confirmed within the past 2 years, the study's recruitment status is shown as unknown.
October 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

Other Study ID Numbers

Identifiers or ID numbers other than the NCT number that are assigned to a clinical study by the study's sponsor, funders, or others. These numbers may include unique identifiers from other trial registries and National Institutes of Health grant numbers.
  • GTX-102-CL301
  • 2024-512600-19-00 (Ctis)

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

Yes

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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