A Study to Assess Safety and Efficacy of Avalglucosidase Alfa Administered Every Other Week in Pediatric Patients With Infantile-onset Pompe Disease Previously Treated With Alglucosidase Alfa

The duration of the study per patient will be up to 3 years that will consist of a 14-day
screening period, that may be extended to up to 4 weeks in pre-specified situations, a
25-week treatment period, a 120-week extension period, and a 4-week post-treatment
observation period.

Inclusion criteria:

- The patient has confirmed acid alpha-glucosidase (GAA) enzyme deficiency from any
tissue source.

- The patient who has reached legal age of majority as defined by local regulation, or
the patient's legal guardian(s) must provide signed informed consent prior to
performing any study-related procedures. If the patient is legally minor per local
regulations, assent shall be obtained from patients, if applicable.

- The patient (and patient's legal guardian if patient is legally minor as defined by
local regulation) must have the ability to comply with the clinical protocol.

- The patient is <18 years old.

- The patient, if female and of childbearing potential, must have a negative serum
pregnancy test (beta-human chorionic gonadotropin) and must not be breastfeeding at
screening/baseline.

- The patient has cardiomyopathy at the time of diagnosis: i.e, left ventricular mass
index (LVMI) equivalent to mean age specific LVMI plus 2 standard deviations.

- The patient has been receiving a stable dose of alglucosidase alfa regularly for a
minimum of 6 months immediately prior to study entry.

- For participants in Stage 1: The patient has documented evidence of clinical decline
in at least 1 of the following parameters related to Pompe Disease and NOT related to
intercurrent illness as assessed by the Investigator: respiratory function, motor
skills, and/or cardiac parameters.

- For participants in Stage 2: The patient has documented evidence of suboptimal
clinical response in at least 1 of the following parameters related to Pompe Disease
and NOT related to intercurrent illness as assessed by the Investigator: respiratory
function, motor skills, and/or new onset of ptosis.

Exclusion criteria:

- The patient has high antibody titer to alglucosidase alfa.

- The patient has a high risk for a severe allergic reaction to neoGAA.

- The patient requires any prohibited concomitant medications (e.g., immune modulatory
treatment) for the duration of the study.

- The patient has previously participated in any ACT14132 study cohort.

- Female patient of childbearing potential not protected by highly effective
contraceptive method of birth control and/or who is unwilling or unable to be tested
for pregnancy

The above information is not intended to contain all considerations relevant to a patient's
potential participation in a clinical trial.