A phase I/II study of intrathecal idursulfase-IT in children with severe mucopolysaccharidosis II.

PURPOSE: Approximately two-thirds of patients with the lysosomal storage disease mucopolysaccharidosis II have progressive cognitive impairment. Intravenous (i.v.) enzyme replacement therapy does not affect cognitive impairment because recombinant iduronate-2-sulfatase (idursulfase) does not penetrate the blood-brain barrier at therapeutic concentrations. We examined the safety of idursulfase formulated for intrathecal administration (idursulfase-IT) via intrathecal drug delivery device (IDDD). A secondary endpoint was change in concentration of glycosaminoglycans in cerebrospinal fluid. METHODS: Sixteen cognitively impaired males with mucopolysaccharidosis II who were previously treated with weekly i.v. idursulfase 0.5 mg/kg for ≥6 months were enrolled. Patients were randomized to no treatment or 10-mg, 30-mg, or 1-mg idursulfase-IT monthly for 6 months (four patients per group) while continuing i.v. idursulfase weekly. RESULTS: No serious adverse events related to idursulfase-IT were observed. Surgical revision/removal of the IDDD was required in 6 of 12 patients. Twelve total doses were administrated by lumbar puncture. Mean cerebrospinal fluid glycosaminoglycan concentration was reduced by approximately 90% in the 10-mg and 30-mg groups and approximately 80% in the 1-mg group after 6 months. CONCLUSIONS: These preliminary data support further development of investigational idursulfase-IT in MPS II patients with the severe phenotype who have progressed only to a mild-to-moderate level of cognitive impairment.Genet Med 18 1, 73-81.

Pharmacokinetics and bioavailability of a therapeutic enzyme (idursulfase) in cynomolgus monkeys after intrathecal and intravenous administration.

Intravenous enzyme replacement therapy with iduronate-2-sulfatase is an approved treatment for Hunter syndrome, however, conventional intravenous delivery cannot treat the neurologic manifestations of the disease due to its limited central nervous system penetration. Intrathecal administration of iduronate-2-sulfatase for delivery to the central nervous system is currently under investigation. The objective of this study was to evaluate the pharmacokinetics of idursulfase in the central nervous system of cynomolgus monkeys (Macaca fasicularis) after intravenous and intrathecal administration. Twenty-seven monkeys, treatment-naïve to enzyme replacement therapy, were placed into 4 groups according to body weight: Group 1 was administered 0.5 mg/kg idursulfase intravenously, Groups 2-4 were administered an intrathecal formulation (1-, 10-, and 30-mg doses). Blood samples and cerebrospinal fluid (sampled at the cisterna magna or lumbar level) were collected at the same time points for 72 hours post dosing. Following intravenous administration, a high maximum serum concentration and rapid distribution of iduronate-2-sulfatase out of the central compartment were observed (elimination half-life: 4.3 hours). Iduronate-2-sulfatase exposure in the cerebrospinal fluid was limited, suggesting intravenous administration provided minimal penetration of the blood-brain barrier. Following intrathecal administration, a high maximum observed concentration was immediately noted and elimination half-life ranged between 7.8-10 hours and 5.9-6.7 hours (cisterna magna and lumbar sampling, respectively). Cerebrospinal fluid pharmacokinetic profiles at different doses of iduronate-2-sulfatase were similar and the dose/exposure relationship was proportional. After intrathecal administration, movement of iduronate-2-sulfatase from cerebrospinal fluid to serum was observed (systemic bioavailability was 40-83%). The clear penetration of iduronate-2-sulfatase into the cerebrospinal fluid and the dose response suggest that intrathecal delivery of iduronate-2-sulfatase may be suitable for treating the central nervous system manifestations associated with Hunter syndrome.

Safety evaluation of chronic intrathecal administration of idursulfase-IT in cynomolgus monkeys.

Recombinant human idursulfase, an intravenous enzyme replacement therapy indicated for treatment of somatic symptoms of mucopolysaccharidosis II (Hunter syndrome), is anticipated to have minimal benefit for the cognitive impairment associated with the severe phenotype. Because intrathecal (IT) administration of enzyme replacement therapy for other lysosomal enzyme disorders has shown efficacy in animal models, an IT formulation of idursulfase (idursulfase-IT) and a drug-delivery device (subcutaneous port connected to a lumbar IT catheter) were developed for treating central nervous system (CNS) involvement. In this chronic safety study, cynomolgus monkeys were dosed weekly with IV idursulfase (0.5 mg/kg) and every four weeks with idursulfase-IT (3, 30, and 100 mg) for six months, with device and vehicle controls treated similarly (n = 6, all groups). Necropsies were performed twenty-four hours post-final IT dose or after a recovery period (four weeks post-final dose in vehicle-control, 3 mg, and 100 mg IT groups: n = 6). No clinical signs or gross central nervous system lesions were observed. Compared to controls, more pronounced cellular infiltrates in brain and spinal cord meninges were noted, which largely resolved after the recovery period. Central nervous sytem levels of idursulfase-IT were dose dependent, as determined by enzyme activity and immunohistochemistry. The no-observed-adverse-effect level of idursulfase-IT was 100 mg.