Safety and Dose Ranging Study of Insulin Receptor MoAb-IDS Fusion Protein in Patients With Hunter Syndrome

Inclusion Criteria: * Male age 18 years or older * Diagnosis of Hunter Syndrome (documented fibroblast or leukocyte IDS enzyme activity level of less than 10% of the lower limit of the normal range of the measuring laboratory - or any level of enzyme deficiency together with the presence of a pathogenic mutation in the IDS gene - and documentation of normal enzymatic activity of at least 1 other sulfatase.) * Must fall into one of the following groups: * currently receiving standard enzyme replacement therapy (ERT) and be willing to discontinue it for the study duration, taking AGT-182 instead * have not received standard ERT for at least 3 months and have elevated uGAGs of at least 3.5 fold above age-related normals at study screening * have never received ERT * Voluntary written consent * Sexually mature males must be advised to use a medically accepted method of contraception throughout the study. Exclusion Criteria: * Refusal to complete screening/baseline evaluations * Receipt of an investigational drug within the prior 90 days * Any medical condition or other circumstances that may significantly interfere with study compliance * Clinically significant spinal cord compression, evidence of cervical instability * Known hypersensitivity to idursulfase or any of the components of AGT-182 * Known to be nonresponsive to standard ERT treatment (i.e., high uGAG values despite taking full dose standard ERT) * History of diabetes mellitus or hypoglycemia * Contraindication to lumbar puncture, if the patient agrees to this optional assessment