An Open-Label, Fixed-Sequence, Ascending-Dose, First-in-Human Study to Assess the Safety, Tolerability, Pharmacokinetics, Pharmacodynamics, and Efficacy of Intravenous Infusions of ATB200 Co-Administered With Oral AT2221 in Adult Subjects With Pompe Disease

• Male and female subjects between 18 and 75years of age, inclusive

• Diagnosis of Pompe disease

⁃ Enzyme Replacement Therapy (ERT)-experienced subject (ambulatory):

• Has received ERT with alglucosidase alfa for the previous 2-6 years, inclusive

• Subject is currently receiving alglucosidase alfa (Myozyme/Lumizyme), at a frequency of once every other week

• Must be able to walk 200-500 meters on the 6-Minute Walk Test (6MWT )

• Has upright Forced Vial Capacity (FVC) 30% to 80% of predicted normal value

⁃ ERT-experienced subjects (non-ambulatory):

• Has received ERT with alglucosidase alfa (Myozyme/Lumizyme) for ≥2 years

• Is wheelchair-bound

⁃ ERT-naïve subjects (ambulatory):

• Must be able to walk 200-500 meters on the 6MWT

• Has upright FVC must be 30% to 80% of predicted normal value

• Subject has never received alglucosidase alfa

⁃ Enzyme Replacement Therapy (ERT)-experienced subject (ambulatory):

• Has received ERT with alglucosidase alfa for \>7years, inclusive

• Subject is currently receiving alglucosidase alfa (Myozyme/Lumizyme), at a frequency of once every other week

• Must be able to walk 200-500 meters on the 6-Minute Walk Test (6MWT )

• Has upright Forced Vial Capacity (FVC) 30% to 80% of predicted normal value