A Study to Evaluate the Safety, Efficacy, Pharmacokinetics, Pharmacodynamics, and Immunogenicity of cipaglucosidase alfa/miglustat in both ERT-experienced and ERT-naïve children under 18 Years with Infantile-onset Pompe Disease

Prior treatment

• Cohort 2: 3. Subject received any investigational drug or any investigational biologic for Pompe disease within 30 days or 5 half-lives of the therapy or treatment, whichever is longer, before screening.
• Cohort 2: 4. Subject is CRIM-negative and will not be receiving prophylactic immunomodulation.
• Cohort 2: 5. Subject has received any gene therapy at any time.
• Cohort 1: 3. Subject received any investigational drug or any investigational biologic for Pompe disease within 30 days or 5 half-lives of the therapy or treatment, whichever is longer, before screening.
• Cohort 1: 4. Subject is CRIM-negative and has not received prophylactic immunomodulation.
• cohort 1: 5. Subject has received any gene therapy within the past 3 years.

Other illness

• Cohort 2: 2. Subject requires respiratory assistance for ≥ 16 hours per day (including noninvasive ventilator support) continuously for ≥ 14 days in the absence of an acute reversible illness, excluding perioperative ventilation.
• Cohort 2: 6. 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.
• Cohort 2: 7. 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.
• Cohort 2: 8. Subject has a history of life-threatening IARs/hypersensitivity (eg, anaphylaxis and severe cutaneous reactions) to ERT (eg, alglucosidase alfa, cipaglucosidase alfa), miglustat, or other iminosugars, or to any of the excipients, where rechallenge was unsuccessful.
• Cohort 1: 2. Subject requires respiratory assistance for ≥ 16 hours per day (including noninvasive ventilator support) continuously for ≥ 14 days in the absence of an acute reversible illness, excluding perioperative ventilation.
• Cohort 1: 6. 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.
• Cohort 1: 7. 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.
• Cohort 1: 8. Subject has a history of life-threatening infusion-associated reactions (IARs)/hypersensitivity (eg, anaphylaxis and severe cutaneous reactions) to ERT (eg, alglucosidase alfa, cipaglucosidase alfa), miglustat, or other iminosugars, or to any of the excipients, where rechallenge was unsuccessful.

Other

• Cohort 1: 1. Subject requires invasive ventilation (eg, tracheostomy).
• Cohort 1: 10. In the opinion of the investigator, the parent or legally authorized representative is unlikely or unable to comply with the study requirements.
• Cohort 2: 1. Subject requires invasive ventilation (eg, tracheostomy).
• Cohort 2: 9. In the opinion of the investigator, the parent or legally authorized representative is unlikely or unable to comply with the study requirements.
• Cohort 1: 9. Female subject is pregnant (or intends to get pregnant) or breastfeeding at screening.

• Cohort 1: 1. Male or female subjects who are aged 6 months to < 18 years on Day 1.
• Cohort 2: 2. Subject’s parent or legally authorized representative is willing and able to provide written informed consent and authorization for study participation and use and disclosure of personal health information or research-related health information.
• Cohort 2: 3. Subject must have documentation of bi-allelic gene encoding human acid α-glucosidase (GAA) variants prior to initiation of study drug.
• Cohort 2: 4. Subject must have had hypertrophic cardiomyopathy at the time of diagnosis defined as: • > 1 standard deviation above the mean age-specific LVMI for subjects diagnosed by newborn screening or sibling screening • > 2 standard deviations above the mean age-specific LVMI for subjects diagnosed by clinical evaluation
• Cohort 2: 5. Subject is ERT-naïve (having had no prior ERT-treatment).
• Long-term Extension (Cohort 1 or Cohort 2) Inclusion Criteria: 1. Subject must have, in the opinion of the investigator, benefitted from therapy with cipaglucosidase alfa/miglustat during the 104-week primary treatment period (Stage 1) with no significant safety concerns.
• Cohort 1: 2. Subject's parent or legally authorized representative is willing and able to provide written informed consent and authorization for study participation and use and disclosure of personal health information or research-related health information.
• Cohort 1: 3. Subject must have documentation of bi-allelic gene encoding human acid α-glucosidase (GAA) variants prior to initiation of study drug.
• Cohort 1: 4. Subject must have had hypertrophic cardiomyopathy at the time of diagnosis defined as: • > 1 standard deviation above the mean age-specific left ventricle mass index (LVMI) for subjects diagnosed by newborn screening or sibling screening • > 2 standard deviations above the mean age-specific LVMI for subjects diagnosed by clinical evaluation
• Cohort 1: 5. Subject must have received ERT for at least 6 months immediately before enrollment. For subjects whose ERT dosage has been modified, the subject must have been on the modified dosage and regimen for at least 3 months before enrollment.
• Cohort 1: 6. Subject must have experienced a clinical decline based on the protocol-specified criteria on their current rhGAA dose and frequency.
• Cohort 1: 7. If of reproductive potential and sexually active, female and male subjects must agree to use a highly effective method of contraception throughout the duration of the study and for at least 90 days after their last dose of cipaglucosidase alfa/miglustat.
• Cohort 1: 8. For subjects aged ≥ 12 to < 18 years, subject must perform one 6-minute walk test (6MWT) (≥ 75 meters) at screening that is valid, as determined by the clinical evaluator; for subjects aged ≥ 5 to < 12 years, subject must perform one 6MWT (≥ 40 meters) at screening that is valid, as determined by the clinical evaluator. Subjects aged 18 months to < 5 years must be ambulatory and in the opinion of the investigator assessed to be likely to be able to perform 6MWT (≥ 40 meters) when they turn 5 years old.
• Cohort 2: 1. Male or female subjects who are aged 0 to < 6 months at on Day 1.