A Study to Evaluate the Safety, Efficacy, PK, PD and Immunogenicity of Cipaglucosidase Alfa/Miglustat in IOPD Subjects Aged 0 to <18

Inclusion Criteria

Cohort 1:

• Male or female subjects who are aged 6 months to \< 18 years on Day 1
• Subject must have documentation of IOPD genotype
• Subject must have had hypertrophic cardiomyopathy at the time of diagnosis
• 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
• Subjects aged ≥ 12 to \< 18 years must perform one valid 6-minute walk test (6MWT) (≥ 75 meters) at screening; Subjects aged ≥ 5 to \< 12 years must perform one valid 6MWT (≥ 40 meters) at screening; Subjects aged 18 months to \< 5 years must be ambulatory and assessed to be likely to be able to perform 6MWT (≥ 40 meters) when they turn 5 years old
• Subjects must have experienced a clinical decline on their current rhGAA dose and frequency

Cohort 2:

• Male or female subjects who are aged 0 to \<6 months at Day 1
• Subject must have documentation of IOPD genotype
• Subject must have had hypertrophic cardiomyopathy at the time of diagnosis
• Subject is ERT-naïve

Long-term Extension (Cohort 1 or Cohort 2):

• Subject must have, in the opinion of the investigator, benefited from therapy with cipaglucosidase alfa/miglustat during the 104-week primary treatment period with no significant safety concerns.

Exclusion Criteria

Cohort 1 and Cohort 2, unless specified

• Subject requires invasive ventilation (eg, tracheostomy)
• Subject is CRIM negative and has not received prophylactic immunomodulation (Cohort 1); Subject is CRIM negative and will not be receiving prophylactic immunomodulation (Cohort 2)
• 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
• Subject has prior history of illness or condition known to affect motor function
• Female subject is pregnant (or intends to get pregnant) or breastfeeding at screening (Cohort 1)