This clinical trial is focused on studying the long-term safety and effectiveness of a treatment for Pompe disease, also known as Glycogen storage disease type II. The treatment being tested is called avalglucosidase alfa, which is also known by the code name GZ402666. This medication is given as a solution through an intravenous infusion, which means it is administered directly into the bloodstream through a vein.

The purpose of the study is to assess the long-term safety of avalglucosidase alfa in patients who have previously participated in other studies related to this treatment. Participants in this study will receive the medication over a period of time, and their health will be monitored to identify any adverse events, which are any unwanted effects that might occur during the treatment. The study will also evaluate the participants’ ability to walk a certain distance in six minutes, their lung function, and their overall quality of life. For those with late-onset Pompe disease, additional assessments will include motor function tests and specific quality of life evaluations. For those with infantile-onset Pompe disease, evaluations will include a pediatric disability inventory and a heart function test.

This study is an extension of previous research and will continue until the medication is reimbursed in France or until December 2025, whichever comes first. Participants will be closely monitored throughout the study to ensure their safety and to gather important data on the effectiveness of avalglucosidase alfa in managing Pompe disease.