X-linked Myotubular MyopathyPhase 1/2NCT07876804
A Long-term Follow-up Study in Male Participants With X-linked Myotubular Myopathy Treated With ASP2957
A Phase 1/2 study testing ASP2957 in people with X-linked Myotubular Myopathy, run by Astellas Gene Therapies.
Trial summary
X-linked myotubular myopathy (XLMTM) is a rare and serious condition present at birth where the muscles do not work properly. There are currently no approved therapies for XLMTM. The protein myotubularin is needed for muscle development, movement and breathing. A gene called MTM1 tells the body to make myotubularin. Read more about this study
- Who is it for?
- Ages Up to 36 months, men only
- Conditions the study is for
- X-linked Myotubular Myopathy
- What is being tested?
- ASP2957
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 9 participants
- Where
- No sites listed yet
- Study dates
- 31 Oct 2026to 31 Jul 2032
- Phase
- Phase 1/2
- Are there results?
- Not yet: the study is under way
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages Up to 36 months
- Men only
- No healthy volunteers
- Child
Who may be able to join
- Participant was treated with ASP2957 in a clinical study and has completed, discontinued or been lost to follow-up from that study.
Who cannot join
- There are no exclusion criteria.
Trial locations and contacts
No sites are listed yet. Contact the study team or a site near you to ask about taking part.
About this study
Official title: A Long-term Study of Young Boys With X-linked Myotubular Myopathy Who Had Previously Received ASP2957
X-linked myotubular myopathy (XLMTM) is a rare and serious condition present at birth where the muscles do not work properly. There are currently no approved therapies for XLMTM.
The protein myotubularin is needed for muscle development, movement and breathing. A gene called MTM1 tells the body to make myotubularin. XLMTM is caused by changes, or mutations, in the MTM1 gene. Changes in the MTM1 gene cause low or no levels of myotubularin to be made, so the muscles do not work properly.
Read more
Gene therapy is a way of getting a healthy copy of a gene into the body. This allows the body's cells to make a normal protein that may reduce disease symptoms. Researchers have developed ASP2957 to get a healthy MTM1 gene into the body. This could help improve muscle development and function in young children with XLMTM.
A single dose of ASP2957 has previously been given to young boys in an earlier study, but health authorities require up to a 5-year follow-up of the boys. This study is a long-term follow-up study of the young boys with XLMTM who previously received ASP2957 in an earlier study. They won't receive ASP2957 in this long-term study.
The main aims of the study is recording medical problems that happen during this study after receiving ASP2957 (in the earlier study), and whether they were caused by ASP2957 or not. This may include abnormal results from blood tests, medical examinations and imaging to check heart health.
They may continue to take medicines that lower their immune system from an earlier study. These help to avoid a reaction to ASP2957.
- Conditions
- X-linked Myotubular Myopathy
- Being tested
- ASP2957
- Keywords
- XLMTM, Recombinant Adeno-Associated Virus, ASP2957, Long-Term Follow-up
- Medical subject headings
- Myopathies, Structural, Congenital
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
ASP2957Drug
Also called MyoAAV3.8 engineered capsid - myosin heavy chain kinase 7 - human myotubularin (MyoAAV3.8-MHCK7-hMTM1)
Participants who have received ASP2957 in Astellas sponsored study.
| Study group | Role | What they receive |
|---|---|---|
| ASP2957 | Experimental | Male participants previously enrolled in Astellas sponsored study and received ASP2957. Receives: Drug: ASP2957 |
What is being measured
The primary outcome is the main question the study is designed to answer.
Number of participants with treatment-emergent adverse events (TEAEs)
An adverse event (AE) is any untoward medical occurrence in a patient or clinical study participant, temporally associated with the use of study intervention, whether or not considered related to the study intervention. An AE can therefore be any unfavorable and unintended sign (including an abnormal laboratory finding), symptom or disease (new or exacerbated) temporally associated with the use of study intervention. This includes events related to the comparator, if applicable, and events related to the (study) procedures. A TEAE is defined as an AE observed after administration of ASP2957.
Measured: Up to 5 years
Number of participants with serious adverse events (SAEs)
An SAE is defined as any untoward medical occurrence that, at any dose results in death. is life-threatening, requires inpatient hospitalization or prolongation of existing hospitalization, results in persistent or significant disability/incapacity, is a congenital anomaly/birth defect and other situations.
Measured: Up to 5 years
Number of participants with adverse events of special interest (AESIs)
AESIs include myocardial-associated events, muscle abnormalities, hepatobiliary disorders, thrombocytopenia, thrombotic microangiopathy (TMA) and life-threatening infections.
Measured: Up to 5 years
Secondary outcomes (1)
Change from baseline in hours per day of ventilation support
Time of ventilator support will be collected.
Measured: Baseline, Months 18, 24, 30, 36, 42, 48, 54 and 60
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted15 Oct 2026
- Study start31 Oct 2026 (estimated)
- Primary completion31 Jul 2032 (estimated)
- Study completion31 Jul 2032 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for X-linked Myotubular MyopathyStudies of the same condition, open and under way.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase 1/2
- Primary purpose
- Treatment
- Allocation
- Not applicable
- Intervention model
- Single group
- Masking
- None (open label)
- Enrolment
- 9 participants (estimated)
Sponsor and investigators
- Lead sponsor
- Astellas Gene Therapies
- Sponsor type
- Industry (pharma, biotech, devices)
- Responsible party
- Sponsor
- Investigators
- Medical Director, Study director, Astellas Gene Therapies, Inc.
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT07876804
- Sponsor's protocol ID
- 2957-CL-4001
- Other IDs
- 2025-524467-21-00, 2025
- Status last verified
- Oct 2026
- First submitted
- 9 Oct 2026
- Last updated
- 15 Oct 2026
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- Yes
- FDA-regulated device
- No
- Individual data sharing
- No: Access to anonymized individual participant level data will not be provided for this trial. Further details on Astellas' data sharing policy can be found at https://www.clinicaltrials.astellas.com/transparency/.
Study at a glance
From the registry record, last updated by the sponsor on 15 Oct 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- A Long-term Study of Young Boys With X-linked Myotubular Myopathy Who Had Previously Received ASP2957
- ClinicalTrials.gov ID
- NCT07876804
- Acronym / sponsor ID
- 2957-CL-4001
- Conditions
- X-linked Myotubular Myopathy
- Keywords
- XLMTM, Recombinant Adeno-Associated Virus, ASP2957, Long-Term Follow-up
- Phase
- Phase 1/2
- Study type
- Interventional
- Recruitment status
- Not yet recruiting
- Enrolment
- 9 participants (estimated)
- Lead sponsor
- Astellas Gene TherapiesIndustry (pharma, biotech, devices)
- Study start
- 31 Oct 2026 (estimated)
- Primary completion
- 31 Jul 2032 (estimated)
- Study completion
- 31 Jul 2032 (estimated)
- First posted
- 15 Oct 2026 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
X-linked myotubular myopathy (XLMTM) is a rare and serious condition present at birth where the muscles do not work properly. There are currently no approved therapies for XLMTM.
The protein myotubularin is needed for muscle development, movement and breathing. A gene called MTM1 tells the body to make myotubularin. XLMTM is caused by changes, or mutations, in the MTM1 gene. Changes in the MTM1 gene cause low or no levels of myotubularin to be made, so the muscles do not work properly.
Gene therapy is a way of getting a healthy copy of a gene into the body. This allows the body's cells to make a normal protein that may reduce disease symptoms. Researchers have developed ASP2957 to get a healthy MTM1 gene into the body. This could help improve muscle development and function in young children with XLMTM.
A single dose of ASP2957 has previously been given to young boys in an earlier study, but health authorities require up to a 5-year follow-up of the boys. This study is a long-term follow-up study of the young boys with XLMTM who previously received ASP2957 in an earlier study. They won't receive ASP2957 in this long-term study.
The main aims of the study is recording medical problems that happen during this study after receiving ASP2957 (in the earlier study), and whether they were caused by ASP2957 or not. This may include abnormal results from blood tests, medical examinations and imaging to check heart health.
They may continue to take medicines that lower their immune system from an earlier study. These help to avoid a reaction to ASP2957.
Study design
- Primary purpose
- Treatment
- Allocation
- Not applicable
- Intervention model
- Single group
- Masking
- None (open label)
- Number of arms
- 1
| Arm | Type | Receives |
|---|---|---|
| ASP2957 | Experimental | Drug: ASP2957Male participants previously enrolled in Astellas sponsored study and received ASP2957. |
Who may qualify
- Ages
- Up to 36 months
- Sex
- Male only
- Healthy volunteers
- Not accepted
- Age groups
- Child
Key inclusion criteria (1 listed)
- Participant was treated with ASP2957 in a clinical study and has completed, discontinued or been lost to follow-up from that study.
Key exclusion criteria (1 listed)
- There are no exclusion criteria.
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| ASP2957Also: MyoAAV3.8 engineered capsid - myosin heavy chain kinase 7 - human myotubularin (MyoAAV3.8-MHCK7-hMTM1)Participants who have received ASP2957 in Astellas sponsored study. | Drug | ASP2957 |
Primary outcome
Number of participants with treatment-emergent adverse events (TEAEs)
Time frame: Up to 5 years
An adverse event (AE) is any untoward medical occurrence in a patient or clinical study participant, temporally associated with the use of study intervention, whether or not considered related to the study intervention. An AE can therefore be any unfavorable and unintended sign (including an abnormal laboratory finding), symptom or disease (new or exacerbated) temporally associated with the use of study intervention. This includes events related to the comparator, if applicable, and events related to the (study) procedures. A TEAE is defined as an AE observed after administration of ASP2957.
Number of participants with serious adverse events (SAEs)
Time frame: Up to 5 years
An SAE is defined as any untoward medical occurrence that, at any dose results in death. is life-threatening, requires inpatient hospitalization or prolongation of existing hospitalization, results in persistent or significant disability/incapacity, is a congenital anomaly/birth defect and other situations.
Number of participants with adverse events of special interest (AESIs)
Time frame: Up to 5 years
AESIs include myocardial-associated events, muscle abnormalities, hepatobiliary disorders, thrombocytopenia, thrombotic microangiopathy (TMA) and life-threatening infections.
1 secondary outcome
Change from baseline in hours per day of ventilation support
Time frame: Baseline, Months 18, 24, 30, 36, 42, 48, 54 and 60
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 15 Oct 2026.
- Individual participant dataSharing planned: No. Access to anonymized individual participant level data will not be provided for this trial. Further details on Astellas' data sharing policy can be found at https://www.clinicaltrials.astellas.com/transparency/.
Related trials for X-linked Myotubular Myopathy
RecruitingObservational study
A Study to Check Liver Health in Boys With XLMTM, a Serious Genetic Muscle Condition
X-Linked Myotubular Myopathy
RecruitingPhase 1/2
Study of ASP2957 in Male Participants With X-linked Myotubular Myopathy Who Need Ventilators
X-Linked Myotubular Myopathy
Active, not recruitingPhase 2/3
A Study of AT132 in Young Children With X-Linked Myotubular Myopathy (XLMTM)
X-Linked Myotubular Myopathy
Recruiting
Assessments in Patients With Muscular Pathology and in Control Subjects : The ActiLiège Next Study
Duchenne Muscular Dystrophy, Fascioscapulohumeral Muscular Dystrophy
RecruitingObservational study
Myotubular and Centronuclear Myopathy Patient Registry
Myotubular Myopathy, Myotubular Myopathy 1
Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part.
Medical Director study director
Astellas Gene Therapies, Inc.
Questions about this trial
What is this clinical trial studying?
A Phase 1/2 study testing ASP2957 in people with X-linked Myotubular Myopathy, run by Astellas Gene Therapies.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 1 inclusion and 1 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: opening soon, as of the sponsor's last update on 15 Oct 2026. Status can change between updates, so confirm with the study contact before making plans.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
What does this combined phase mean?
Phase 1 studies test a treatment in a small group of people for the first time or in a new way, mainly to check safety and find the right dose.
Phase 2 studies give the treatment to a larger group to see whether it has the intended effect and to keep checking safety.
Not every study follows the same path, and some studies (observational studies, device studies) have no phase.
Are results available for this study?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
Contact Astellas Gene Therapies, Inc. (800-888-7704, Astellas.registration@astellas.com), or a site near the patient. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Number of participants with treatment-emergent adverse events (TEAEs) (time frame: Up to 5 years). The study lists 3 primary outcomes in all. It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 15 Oct 2026.