Gene Therapy Study of ASP2957 in Boys Up to 3 Years Old With Severe Ventilator-Dependent X-linked Myotubular Myopathy

What this Trial Is About

X-linked myotubular myopathy XLMTM is a rare and serious genetic condition present at birth that affects muscle function, especially in boys up to 3 years old who require ventilator support. The disease is caused by mutations in the MTM1 gene, leading to low or no production of the protein myotubularin, which is essential for muscle development and breathing. Currently, there are no approved treatments for XLMTM, prompting research into gene therapy as a potential option. Researchers are studying ASP2957, a gene therapy designed to deliver a healthy copy of the MTM1 gene using a harmless virus to improve muscle function. This study is conducted in two phases Phase 1 involves small groups of boys receiving escalating doses of a single infusion of ASP2957 along with medicines to suppress the immune system Phase 2 uses the best dose identified in Phase 1, given as a single infusion with the same immune-suppressing medicines. Boys who may have pre-existing antibodies to the virus also receive immunosuppression to help the therapy work safely. Participants will be monitored for up to one year after their single infusion through various assessments including physical exams, muscle biopsies, imaging, laboratory tests, and heart evaluations to track safety and effects. Researchers will record any side effects and measure changes in ventilator support needs. After this period, families may choose to continue long-term follow-up in another study to observe ongoing effects and safety.

Study of ASP2957 in Male Participants With X-linked Myotubular Myopathy Who Need Ventilators