Abstract
Primary Objective: To determine the effect of avalglucosidase alfa treatment on respiratory muscle strength measured by percent (%) predicted forced vital capacity (FVC) in the upright position, as compared to alglucosidase alfa. Secondary Objective: To determine the safety and effect of avalglucosidase alfa treatment on functional endurance (6-minute walk test, inspiratory muscle strength (maximum inspiratory pressure), expiratory muscle strength (maximum expiratory pressure), lower extremity muscle strength (hand-held dynamometry), motor function (Quick Motor Function Test), and health-related quality of life (Short Form-12).