This is a multi-center, open label, study conducted to evaluate the safety of laronidase administered by intravenous drip infusion in Japanese patients with MPS I disease.

Following baseline evaluation, patients will receive weekly infusions of JC0498 at an intravenous dose of 100 units/kg. Patient safety will be monitored continuously throughout the trial. In addition, the effects of JC0498 treatment in this patient population will be assessed by periodically evaluating aspects of MPS I disease in patients at scheduled intervals over the duration of the trial.

Since patients may be eligible for the trial if they have received JC0498, a portion of the data may be captured retrospectively and recorded onto the case report forms (CRFs).

This study represents the first good clinical practice (GCP) effort to characterize MPS I in the Japanese population and evaluate the effects of JC0498 on disease manifestations.

Inclusion Criteria:

• Written informed consent/assent of the patient or written informed consent of the parent(s) or the legal guardian(s), depending on the age of the patient, is required prior to any protocol-related procedures being performed; this includes information regarding hematopoietic stem cell transplantation (HSCT) in order to assure that the guardian(s) is fully informed regarding the risks and benefits of this alternative treatment for patients eligible for the trial and who have severe manifestations of MPS I with neurodegeneration.
• Have a clinical diagnosis of MPS, confirmed by measurable clinical signs and symptoms of MPS I.
• Have confirmed iduronidase deficiency with a leukocyte alpha-L-iduronidase enzyme activity level of less than 10.0% of the lower limit of the normal range of the measuring laboratory (SRL)

Exclusion Criteria:

• The patient is under consideration for or has previously undergone hematopoietic stem cell transplantation.
• The patient has acute hydrocephalus at the time of enrollment.
• The patient has a clinically significant organic disease (with the exception of symptoms relating to MPS I) including: cardiovascular, hepatic, pulmonary, neurologic, or renal disease, other serious intercurrent illness, or extenuating circumstances that, in the opinion of the Investigator, would preclude participation in the trial or potentially decrease survival.
• The patient has received any investigational product within 30 days prior to trial enrollment (exception: JC0498).
• The patient has known severe hypersensitivity to JC0498 or components of the delivery solution.

In multi-site studies, PI can publish after Genzyme publishes or 18 months after study completion. PI gives Genzyme a draft 60 days before publication. Genzyme can ask that confidential information be removed, and can defer publication another 60 days upon notifying PI that it will file a patent application on inventions contained in the draft.