A Phase 1/2 interventional study of ASP2957 in X-linked Myotubular Myopathy, sponsored by Astellas Gene Therapies. Not yet recruiting. Open to male participants aged Up to 36 Months. Per ClinicalTrials.gov, last updated 2026-10-15.
Sponsored by Astellas Gene Therapies (part of Astellas Pharma Inc) · Phase 1/2, Interventional, and Treatment
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.
24 studies on the registry are indexed under Myopathies, Structural, Congenital; 11 are open to participants now.
This study's planned enrollment of 9 is below the median of 23 across 10 interventional studies indexed under Myopathies, Structural, Congenital.
Browse Myopathies, Structural, Congenital studies →Astellas Gene Therapies is the lead sponsor of 9 studies on the registry; 3 are open to participants now.
First submitted after Astellas Gene Therapies became part of Astellas Pharma Inc.
Counted across the registry records on this site, refreshed daily.
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Exclusion Criteria:
Male participants previously enrolled in Astellas sponsored study and received ASP2957.
Drug: ASP2957
Participants who have received ASP2957 in Astellas sponsored study.
Also known as: MyoAAV3.8 engineered capsid - myosin heavy chain kinase 7 - human myotubularin (MyoAAV3.8-MHCK7-hMTM1)
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.
Time frame: 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.
Time frame: 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.
Time frame: Up to 5 years
Change from baseline in hours per day of ventilation support
Time of ventilator support will be collected.
Time frame: Baseline, Months 18, 24, 30, 36, 42, 48, 54 and 60
No study locations are listed for this record.
Plan to share: 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/.
No publications or documents are linked to this record.
Start is estimated for Oct 2026; primary completion for Jul 2032, 69 months later.
How these figures are worked out, and which studies are left out of them.
From the registry record's own update history. This site started tracking changes on Sep 25, 2026; for anything earlier, see the record history on ClinicalTrials.gov ↗
This study is not yet recruiting, as verified in Oct 2026. You cannot join it, but the record below documents what was studied.
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Myopathies, Structural, Congenital →