1. Body weight greater than or equal to 40 kg
2. Diagnosis of LOPD
3. Upright FVC greater than or equal to 30% of predicted normal value
4. Able to ambulate greater than or equal to 40 meters (use of assistive devices is acceptable)
5. [Cohorts A1-A4 only] Have received avalglucosidase alfa or cipaglucosidase alfa at a dose of 20 mg/kg every 2 weeks for at least 12 months prior to screening
6. [Cohorts B1-B2 only] Must not have received any enzyme-replacement therapy for Pompe disease in the 12 months prior to screening

Key

1. Any ongoing, clinically significant, unstable, or poorly controlled neurological, psychiatric, endocrine, pulmonary, cardiovascular, gastrointestinal, hepatic, pancreatic, renal, metabolic, hematological, immunological, allergic, or ophthalmic disease not related to Pompe disease, or other major disorders. Well-controlled conditions are permitted if investigator and Sponsor agree.
2. Wheelchair-dependent
3. Require noninvasive ventilation for an average of more than 6 hours per day while awake or any invasive ventilation. Use of noninvasive ventilation during sleep is acceptable.
4. Received an experimental gene therapy at any time or participation in any other investigational drug trial or use of investigational drug within 60 days or 5 half-lives, whichever is longer, before screening