| E.1 Medical condition or disease under investigation | 
| E.1.1 | Medical condition(s) being investigated  | 
| Glycogen storage disease type II | 
 
 
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| E.1.1.1 | Medical condition in easily understood language  | 
| Glycogen storage disease type II | 
 
 
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| E.1.1.2 | Therapeutic area  | Diseases [C] - Congenital, Hereditary, and Neonatal Diseases and Abnormalities [C16] | 
| MedDRA Classification | 
| E.1.2 Medical condition or disease under investigation | 
| E.1.2 | Version  | 20.1 | 
 
| E.1.2 | Level  | PT | 
 
| E.1.2 | Classification code  | 10053185 | 
 
| E.1.2 | Term  | Glycogen storage disease type II | 
 
| E.1.2 | System Organ Class  | 10010331 - Congenital, familial and genetic disorders | 
 
 
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| E.1.3 | Condition being studied is a rare disease  |  Yes  | 
| E.2 Objective of the trial | 
| E.2.1 | Main objective of the trial  | 
| To determine the effect of avalglucosidase alfa treatment on survival and invasive ventilator-free survival of IOPD participants less than or equal to 6 months of age after 52 weeks of treatment. | 
 
 
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| E.2.2 | Secondary objectives of the trial  | 
- To determine the effect of avalglucosidase alfa treatment on survival and invasive ventilator-free survival at 12 and 18 months of age, as well as the change in left ventricular mass Z-score (LVM Z-score); Alberta Infant Motor Scale (AIMS) score; body length, body weight, and head circumference Z scores; and urinary Hex4 at Week 52 in IOPD participants less than or equal to 6 months of age 
 - To determine safety, tolerability, and immunogenicity of avalglucosidase alfa 
 - To determine the PK profile at Week 12 and Week 52 | 
 
 
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| E.2.3 | Trial contains a sub-study  |  No  | 
| E.3 | Principal inclusion criteria  | 
- Participants must have confirmed diagnosis of infantile-onset Pompe disease defined as: the presence of 2 lysosomal acid α-glucosidase (GAA) pathogenic variants and a documented GAA deficiency from blood, skin, or muscle tissue; or the presence of 1 GAA pathogenic variant and a documented GAA deficiency from blood, skin and muscle tissue in 2 separate samples (from either 2 different tissues or from the same tissue but at 2 different sampling dates).  
 - Participants must have established cross-reactive immunological material (CRIM) status available prior to enrollment. 
 - Participants must have cardiomyopathy at the time of diagnosis: ie, left ventricular mass index (LVMI) equivalent to mean age specific LVMI        +1 standard deviation for participants diagnosed by newborn screening or sibling screening;        +2 standard deviation for participants diagnosed by clinical evaluation. 
 - Parents or legally authorized representative(s) must be capable of giving signed informed consent 
 | 
 
 
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| E.4 | Principal exclusion criteria | 
Participants are excluded from the study if any of the following criteria apply: - Participants with symptoms of respiratory insufficiency, including any ventilation use (invasive or noninvasive) at the time of enrollment. - Participants with major congenital abnormality. - Participants with clinically significant organic disease (with the exception of symptoms relating to Pompe disease). - Participant received any Pompe disease specific treatment, eg ERT gene therapy. - Participant who has previously been treated in any clinical trial of avalglucosidase alfa. - Participant not suitable for participation, whatever the reason, as judged by the Investigator, including medical or clinical conditions, or participants potentially at risk of noncompliance to study procedures. | 
 
 
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| E.5 End points | 
| E.5.1 | Primary end point(s) | 
| Proportion of participants who are alive and free of invasive ventilation at Week 52 | 
 
 
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| E.5.1.1 | Timepoint(s) of evaluation of this end point | 
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| E.5.2 | Secondary end point(s) | 
1/ Proportion of participants who are alive and free of invasive ventilation at 12 and 18 months of age 
 2/ Proportion of participants who are alive at Week 52  
 3/ Proportion of participants who are alive at 12 and 18 months of age 
 4/ Proportion of participants who are free of ventilator use (invasive and non-invasive separate and combined) at Week 52 
 5/ Proportion of participants who are free of supplemental oxygen use at Week 52 
 6/ Change from baseline to Week 52 in left ventricular mass (LVM)-Z score 
 7/ Change from baseline to Week 52 in Alberta Infant Motor Scale (AIMS) score 
 8/ Change from baseline to Week 52 in body length Z-scores 
 9/ Change from baseline to Week 52 in body weight Z-scores 
 10/ Change from baseline to Week 52 in head circumference Z-scores 
 11/ Change from baseline to Week 52 in body length percentiles 
 12/ Change from baseline to Week 52 in body weight percentiles 
 13/ Change from baseline to Week 52 in head circumference percentiles 
 14/ Change from baseline to Week 52 in urinary Hex4 
 15/ Assessment of treatment-emergent adverse events (TEAE) including infusion-associated reactions (IAR) 
 16/ Physical examination 
 17/ Clinical laboratory evaluations 
 18/ Vital signs measurements 
 19/ 12-lead electrocardiogram (ECG) 
 20/ Immunogenicity assessments 
 21/ Plasma concentration of avalglucosidase alfa | 
 
 
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| E.5.2.1 | Timepoint(s) of evaluation of this end point | 
1/, 3/: at 12 and 18 months of age 
 2/ and from 4/ to 14/ : Week 52 
 15/: week 52, week 212 
 From 16/ to 20/:  Week 52, Week 208 
 21/ : at Day 1, Week 12, and Week 52 | 
 
 
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| E.6 and E.7 Scope of the trial | 
| E.6 | Scope of the trial | 
| E.6.1 | Diagnosis |  No  | 
| E.6.2 | Prophylaxis |  No  | 
| E.6.3 | Therapy |  No  | 
| E.6.4 | Safety |  Yes  | 
| E.6.5 | Efficacy |  Yes  | 
| E.6.6 | Pharmacokinetic |  Yes  | 
| E.6.7 | Pharmacodynamic |  Yes  | 
| E.6.8 | Bioequivalence |  No  | 
| E.6.9 | Dose response |  No  | 
| E.6.10 | Pharmacogenetic |  No  | 
| E.6.11 | Pharmacogenomic |  No  | 
| E.6.12 | Pharmacoeconomic |  No  | 
| E.6.13 | Others |  No  | 
| E.7 | Trial type and phase | 
| E.7.1 | Human pharmacology (Phase I) |  No  | 
| E.7.1.1 | First administration to humans |  No  | 
| E.7.1.2 | Bioequivalence study |  No  | 
| E.7.1.3 | Other |  No  | 
| E.7.1.3.1 | Other trial type description |  | 
| E.7.2 | Therapeutic exploratory (Phase II) |  No  | 
| E.7.3 | Therapeutic confirmatory (Phase III) |  Yes  | 
| E.7.4 | Therapeutic use (Phase IV) |  No  | 
| E.8 Design of the trial | 
| E.8.1 | Controlled |  No  | 
| E.8.1.1 | Randomised |  No  | 
| E.8.1.2 | Open |  No  | 
| E.8.1.3 | Single blind |  No  | 
| E.8.1.4 | Double blind  |  No  | 
| E.8.1.5 | Parallel group |  No  | 
| E.8.1.6 | Cross over  |  No  | 
| E.8.1.7 | Other |  No  | 
| E.8.2 |  Comparator of controlled trial | 
| E.8.2.1 | Other medicinal product(s) |  No  | 
| E.8.2.2 | Placebo  |  No  | 
| E.8.2.3 | Other |  No  | 
| E.8.2.4 | Number of treatment arms in the trial | 1 | 
| E.8.3 | 
                                The trial involves single site in the Member State concerned
                             |  Yes  | 
| E.8.4 |  The trial involves multiple sites in the Member State concerned  |  No  | 
| E.8.5 | The trial involves multiple Member States |  Yes  | 
| E.8.5.1 | Number of sites anticipated in the EEA | 9 | 
| E.8.6 Trial involving sites outside the EEA | 
| E.8.6.1 | Trial being conducted both within and outside the EEA |  Yes  | 
| E.8.6.2 | Trial being conducted completely outside of the EEA |  No  | 
| E.8.6.3 | If E.8.6.1 or E.8.6.2 are Yes, specify the regions in which trial sites are planned | 
| Taiwan | 
 
| China | 
 
| United Kingdom | 
 
| United States | 
 
| Belgium | 
 
| France | 
 
| Germany | 
 
| Italy | 
 
| Netherlands | 
 
 
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| E.8.7 | Trial has a data monitoring committee |  Yes  | 
| E.8.8 | 
                        Definition of the end of the trial and justification where it is not the last
                        visit of the last subject undergoing the trial
                     | 
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| E.8.9 Initial estimate of the duration of the trial | 
| E.8.9.1 | In the Member State concerned years | 5 | 
| E.8.9.1 | In the Member State concerned months | 4 | 
| E.8.9.1 | In the Member State concerned days |  | 
| E.8.9.2 | In all countries concerned by the trial years | 5 | 
| E.8.9.2 | In all countries concerned by the trial months | 4 |