Elaprase, a large molecular protein, is not expected to cross the blood brain barrier when administered intravenously. A revised formulation of idursulfase, idursulfase-IT, that differs from that of the intravenous (IV) formulation, Elaprase, has been developed to be suitable for delivery into the cerebrospinal fluid (CSF) via intrathecal administration.~Mucopolysaccharidosis II (MPS II) is a rare, X-linked, inherited disease that affects males nearly exclusively. The disease is caused by the absence of, or deficiency in, the activity of the lysosomal enzyme, iduronate-2-sulfatase (I2S) which acts to cleave O-linked sulfate moieties from the glycosaminoglycan (GAG) molecules dermatan sulfate and heparan sulfate.~Study HGT-HIT-094 is a controlled, randomized, two-arm, open-label, assessor-blinded, multicenter study to determine the effect on clinical parameters of neurodevelopmental status of monthly IT administration of idursulfase-IT 10 mg for 12 months in pediatric patients with Hunter syndrome and cognitive impairment who have previously received and tolerated a minimum of 4 months of therapy with Elaprase.~Pediatric patients under 3 years of age will be enrolled into a separate substudy to evaluate the safety and efficacy of idursulfase-IT. The separate substudy is open label and single arm. Patients who are enrolled in the substudy will receive idursulfase-IT treatment and follow the same schedule of study visits.
Study HGT-HIT-094 is a multicenter study designed to determine the effect on clinical parameters of neurodevelopmental status of monthly IT administration of idursulfase-IT 10 mg for 12 months in pediatric patients with Hunter syndrome and cognitive impairment who have previously received and tolerated a minimum of 4 months of therapy with Elaprase.