How do I qualify? Study participant must meet all of the inclusion criteria and none of the exclusion criteria to participate in the study.

Subjects will be enrolled in 1 of 2 cohorts:

• Cohort 1 will be treated with cipaglucosidase alfa/miglustat and will include at least 10 subjects (ERT-experienced and ERT-naïve) aged 12 to < 18 years at the time of enrollment.
• Cohort 2 will be treated with cipaglucosidase alfa/miglustat and will include at least 12 subjects (ERT-experienced and ERT-naïve) aged 0 to < 12 years at the time of enrollment, with at least 4 subjects aged 6 to < 12 years and at least 4 subjects aged 0 to < 6 years.

Inclusion Criteria:

Inclusion Criteria for Cohort 1

1. Male or female subjects (ERT-naïve [have never received a dose of rhGAA] or ERT-experienced [have received rhGAA for at least 6 months immediately before enrollment, and if ERT dosage has been modified, must have been on the modified dosage for at least 3 months before enrollment]) diagnosed with LOPD who are aged 12 to < 18 years at screening
2. Subject weighs ≤ 115 kg.
3. Subject’s parent or legally authorized representative is willing and able to provide written informed consent and authorization for use and disclosure of personal health information or research-related health information, and subject provides assent, if applicable, based on site and local regulations
4. Subject must have a diagnosis of LOPD based on documentation of at least one of the following: 
   1. Deficiency of GAA enzyme b.gene encoding human acid α-glucosidase (GAA) genotyping
   2. If of reproductive potential and if sexually active, female and male subjects agree to use a highly effective method of contraception throughout the duration of the study and for up to 90 days after their last dose of cipaglucosidase alfa/miglustat
5. Subject has a sitting forced vital capacity (FVC) ≥ 30% of the predicted value for healthy adolescents (Global Lung Function Initiative) at screening
6. Subject performs one 6-Minute Walk Test (6MWT) (≥ 75 meters) at screening that is valid, as determined by the clinical evaluator

Inclusion Criteria for Cohort 2

1. Male or female subjects (ERT-naïve [have never received a dose of rhGAA] or ERT-experienced [have received rhGAA for at least 6 months immediately before enrollment, and if ERT dosage has been modified, must have been on the modified dosage for at least 3 months before enrollment]) diagnosed with LOPD who are aged 0 months to < 12 years at screening
2. Subject’s parent or legally authorized representative is willing and able to provide written informed consent and authorization for use and disclosure of personal health information or research-related health information
3. Subject must have a diagnosis of LOPD based on documentation of one of the following:

1. deficiency of GAA enzyme
2. GAA genotyping

4. If of reproductive potential and if sexually active, female and male subjects agree to use a highly effective method of contraception throughout the duration of the study and for up to 90 days after their last dose of cipaglucosidase alfa/miglustat
5. Subjects aged ≥ 5 to <12 years who perform one 6MWT (≥ 40 meters) at screening that is valid, as determined by the clinical evaluator

Exclusion Criteria:

Exclusion Criteria for Cohort 1

1. Subject has received any investigational/experimental drug, oral anabolic steroid or derivative, biologic, or device within 30 days or 5 half-lives of the therapy or treatment, whichever is longer, before screening
2. Subject has received treatment with prohibited medications within 30 days of screening
3. Subject has received any gene therapy at any time
4. Subject has any intercurrent illness or condition at screening or baseline that may preclude the subject from fulfilling the protocol requirements or suggests to the investigator and/or the medical monitor that the potential subject may have an unacceptable risk by participating in this study
5. Subject has a hypersensitivity to any of the excipients in cipaglucosidase alfa, approved rhGAA, or miglustat
6. Female subject is pregnant or breast-feeding at screening
7. Subject requires the use of ventilation support for > 6 hours per day while awake
8. Subject has evidence of moderate to severe hypertrophic cardiomyopathy aligning with classic IOPD
9. In the opinion of the investigator, the parent or legally authorized representative is unlikely or unable to comply with the study requirements
10. Subject has any prior history of illness or condition known to affect motor function, such as, but not limited to, Guillain-Barre syndrome, cerebral palsy, etc.

Exclusion Criteria for Cohort 2

1. Subject has received any investigational/experimental drug, oral anabolic steroid or derivative, biologic, or device within 30 days or 5 half-lives of the therapy or treatment, whichever is longer, before screening
2. Subject has received treatment with prohibited medications within 30 days of screening
3. Subject has received any gene therapy at any time
4. Subject has any intercurrent illness or condition at screening or baseline that may preclude the subject from fulfilling the protocol requirements or suggests to the investigator and/or the medical monitor that the potential subject may have an unacceptable risk by participating in this study
5. Subject has a hypersensitivity to any of the excipients in cipaglucosidase alfa, approved rhGAA, or miglustat
6. Female subject is pregnant or breast-feeding at screening
7. Subject requires the use of ventilation support for > 6 hours per day while awake
8. Subject has moderate to severe hypertrophic cardiomyopathy aligning with classic IOPD
9. In the opinion of the investigator, the parent or legally authorized representative is unlikely or unable to comply with the study requirements
10. Subject has any prior history of illness or condition known to affect motor function, such as, but not limited to, Guillain-Barre syndrome, cerebral palsy, etc.
11. Subject who is diagnosed with Pompe disease via newborn screening and is asymptomatic (i.e., showing no signs and symptoms of Pompe disease [Kronn 2017])