 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 mgkg. Final evaluations from Study TKT024, the one-year predecessor Phase 2Phase 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. 