This protocol amendment includes 2 major changes that substantially affect the inclusion criteria for participation in this study. The upper limit of age at the time of the first study infusion was increased from 6 months to 12 months. In addition, the requirement that a subject must have an left ventricular mass index Z-score (LVMI-Z) of greater than 2 was removed. Protocol Synopsis and Abbreviations: Updated to reflect overall changes in protocol. Number of Subjects: expanded the subject population to include subjects without cardiac hypertrophy who met the inclusion criteria. Revised secondary objectives to reflect addition of Alberta Infant Motor Scale (AIMS) for evaluation of changes in motor function in response to enzyme replacement therapy (ERT) over time. Revised tertiary efficacy endpoints to include AIMS as the most appropriate endpoint to assess subjects without cardiac hypertrophy. Assessment was moved from Demographic and Screening Assessments to Efficacy Assessments. Respiratory Function: Updated for clarification. If the subject required mechanical ventilatory support during the study, the start date, stop date, and reasons for each episode of continuous ventilator support would be recorded on the electronic case report form (eCRF) by authorized site personnel. Determination of Sample Size: Updated for clarity. Secondary Efficacy Analyses: Updated for clarity. Schedule of Study Events: Added assessment of AIMS at Week 12, Week 26, and Week 52 as AIMS was the most appropriate endpoint to assess subjects without cardiac hypertrophy.

This protocol amendment includes 1 major change to the planned analysis of this study. The primary endpoint of this study was change from baseline in cardiac function as measured by left ventricular mass Z-score (LVM-Z) assessed at the end of the 52-week treatment period. - Changed protocol descriptor and protocol title. - Added date of Protocol Amendment 2. - Added Genzyme Europe BV as Sponsor. - Updated Medical Monitor information. - Changed “Global Patient Safety and Risk Management” to “Global Pharmacovigilance and Epidemiology” to reflect recent department name change.- Changed primary objective to indicate that the primary efficacy endpoint was change in left ventricular mass Z-score (LVM-Z) from baseline to Week 52.- Changed all instances of "LVMI-Z" to "LVM-Z" to reflect change in primary efficacy endpoint. - Updated Abbreviations section to add "confidence interval", "Global Pharmacovigilance and Epidemiology" and "noninferiority" and to remove "Global Patient Safety and Risk Management".- Added text to describe Phase 3 or Phase 4 protocol dependent upon country registration status.- Added text to indicate blood testing for cross-reactive immunologic material (CRIM) status was optional and did not had to be repeated if written results were available for testing performed prior to study enrollment.- Amended text to indicate R voltage V6 and S voltage V1 were not required assessments.- Added Sections to provide definitions for "Anaphylactic / Hypersensitivity Reactions" and "Immune Mediated Reactions", respectively. - Revised statistical parameters to correspond with LVM values from Genzyme study AGLU01602/2403.- Revised text to indicate change in analysis planned for clinical laboratory assessments.- Removed stipulation that Data Monitoring Committee be comprised of 4 physicians. Removed Sponsor contact information for Europe as all product handling is now provided by North America office.