Extension Study Evaluating Long Term Safety and Activity of AGT-181 in Children With MPS I

Inclusion Criteria: * 2 years of age or older (and less than 18) * Must have been previously enrolled in study AGT-181-101 * Written consent and assent as required * Female patients must not be pregnant, willing to utilize appropriate birth control methods and undergo pregnancy testing during the study Exclusion Criteria: * Refusal to complete all assessments * Pregnant or Lactating * Received investigational drug within 1 year prior to study enrollment * Medical condition or extenuating circumstance that, in the opinion of the investigator, may interfere with study compliance * Clinically significant spinal cord compression or evidence of cervical instability (i.e. expected to require intervention during study participation) * Has developed clinically relevant hypersensitivity/anaphylactoid reactions to AGT-181