Avalglucosidase Alfa Extension Study

The planned duration of the study for each participant was initially 6 years. Each participant continued with the study until the participant withdrew, the Investigator withdrew the participant, or the Sponsor terminated the study. An additional follow-up phase began after the participant has completed the 6-year study period, and lasted until avalglucosidase alfa was approved in the participant's country, except in the United Kingdom (UK), Germany and Denmark, where the duration of the additional follow-up phase was up to the approval in the country or limited to a maximum of 2 years, whichever occurred first (ie, for participants in the UK, Germany and Denmark, the total study duration per participant was 8 years at the maximum including the initial 6-year period and the additional 2-year follow-up).