First-In-Human Study to Evaluate Safety, Tolerability, and PK of Intravenous ATB200 Alone and When Co-Administered With Oral AT2221

Adults with Diagnosis of Pompe disease Cohort 1: Enzyme Replacement Therapy (ERT)-experienced subject (ambulatory): * Male and female subjects between 18 and 65 years of age, inclusive * Received ERT with alglucosidase alfa (Myozyme/Lumizyme) for the previous 2-6 years, inclusive * Was receiving alglucosidase alfa at a frequency of once every other week * Must have been able to walk 200-500 meters on the 6-Minute Walk Test (6MWT) * Had upright Forced Vial Capacity (FVC) 30-80% of predicted normal value Cohort 2: ERT-experienced subjects (non-ambulatory): * Male and female subjects between 18 and 65 years of age, inclusive * Had been receiving ERT with alglucosidase alfa for ≥2 years at a regular or set frequency * Was wheelchair-bound Cohort 3: ERT-naïve subjects (ambulatory): * Male and female subjects between 18 and 65 years of age, inclusive * Must have been able to walk 200-500 meters on the 6MWT * Had upright FVC 30-80% of predicted normal value Cohort 4: ERT-experienced subject (ambulatory): * Male and female subjects between 18 and 75 years of age, inclusive * Had been receiving ERT with alglucosidase alfa for ≥7 years, inclusive * Was receiving alglucosidase alfa at a frequency of once every other week * Must have been able to walk 75-600 meters on the 6MWT * Had upright FVC 30-85% of predicted normal value Exclusion Criteria: * Received treatment with prohibited medications within 30 days of Baseline Visit * Subject, if female, was pregnant or breastfeeding at screening * Subject, whether male or female, planned to conceive a child during the study * Had a medical or any other extenuating condition or circumstance that may, in opinion of investigator, pose an undue safety risk to the subject or compromise his/her ability to comply with protocol requirements * Had a history of allergy or sensitivity to alglucosidase alfa, miglustat or other iminosugars (Cohorts 1, 2, and 4) * Required invasive ventilatory support, or used noninvasive ventilatory support ≥ 6 hours a day while awake (Cohorts 1, 3, and 4) * Had active systemic autoimmune disease such as lupus, scleroderma, or rheumatoid arthritis; subjects with autoimmune disease must have been discussed with the Amicus Medical Monitor * Had active bronchial asthma; subjects with bronchial asthma must have been discussed with the Amicus Medical Monitor