Extension of Study TKT024 Evaluating Long-Term Safety and Clinical Outcomes in MPS II Patients Receiving Idursulfase

Study TKT024EXT was conducted in 2 phases. The first phase ("Phase I") was 2 years (104
weeks) in duration and consisted of weekly infusions of IV idursulfase (0.5 mg/kg), and the
collection of patients' safety and clinical outcomes. Week 105 defined the beginning of the
second phase of the study. The second phase ("Phase II") consisted of weekly infusions of IV
idursulfase (0.5 mg/kg) and the monitoring of patients for safety (via collection of adverse
events, concomitant medications, and vital signs). Study completion was defined as the time
a patient either transitioned to commercially available idursulfase or discontinued this
study.

Idursulfase was administered to patients as a continuous IV infusion at a dose of 0.5 mg of
protein per kg of body weight (0.5 mg/kg). Final evaluations from Study TKT024, the one-year
predecessor Phase 2/Phase 3 registration study, served as the baseline assessments for the
TKT024EXT study. Forced vital capacity (FVC) and the 6-minute walk test (6MWT) continued to
be the primary clinical outcomes of TKT024EXT study. Efficacy outcomes were evaluated over
the course of 2 years and were determined at 4-month intervals during the first year (ie,
Weeks 18, 36, and 53) and at 6-month intervals in the second year (ie, Weeks 79 and 105).
Safety outcomes were assessed throughout the duration of the study. The safety and clinical
testing performed in the TKT024EXT study were identical to those performed in the
double-blind phase of Study TKT024.

Inclusion Criteria:

- Patient must have completed the double-blind phase of Study TKT024, defined as
completing the Week 53 final evaluations.

- Patient, patient's parent(s), or legally authorized representative must have
voluntarily signed an Institutional Review Board (IRB)/Independent Ethics Committee
(IEC)-approved informed consent form after all relevant aspects of the study have
been explained and discussed with the patient.

Exclusion Criteria:

- Patient has received treatment with an investigational therapy other than
iduronate-2-sulfatase in Study TKT024 within the past 60 days.

- Patient is unable to comply with the protocol (e.g., due to a medical condition such
as cervical cord compression or uncooperative attitude) or is unlikely to complete
the study, as determined by the investigator.

- Patient has experienced an adverse reaction to study drug in Study TKT024, which
contraindicates further treatment with idursulfase.

- Patient with known hypersensitivity to any of the components of idursulfase.