This open-label Phase 2 study will evaluate the safety and efficacy of weekly 2.0 mg/kg/wk infusions of BMN 110 in pediatric patients, less than 5 years of age at the time of administration of the first dose of study drug, diagnosed with MPS IVA (Morquio A Syndrome) for up to 208 weeks.

Inclusion Criteria:

• Less than 5 years of age at the time of the first study drug infusion
• Documented clinical diagnosis of MPS IVA based on clinical signs and symptoms of MPS IVA and documented reduced fibroblast or leukocyte GALNS enzyme activity or genetic testing confirming diagnosis of MPS IVA
• Written informed consent provided by parent or legally authorized representative after the nature of the study has been explained and prior to any research-related procedures.

Exclusion Criteria:

• Previous hematopoietic stem cell transplant (HSCT).
• Previous treatment with BMN 110.
• Known hypersensitivity to any of the components of BMN 110.
• Major surgery within 3 months prior to stuy entry or planned major surgery during the 52-week treatment period.
• Use of any investigational product or investigational medical device within 30 days prior to Screening, or requirement for any investigational agent prior to completion of all scheduled study assessments.
• Concurrent disease or condition, including but not limited to symptomatic cervical spine instability, clinically significant spinal cord compression, or severe cardiac disease that would interfere with study participation or safety as determined by the Investigator.
• Any condition that, in the view of the Investigator, places the subject at high risk of poor treatment compliance or of not completing the study.

52 weeks