Safety and Dose Ranging Study of Insulin Receptor MAb-IDUA Fusion Protein in Patients With MPS I

Inclusion Criteria: * Male age 18 years or older * Diagnosis of MPS I (documented fibroblast or leukocyte IDUA enzyme activity level of less than 10% of the lower limit of the normal range of the measuring laboratory) * Voluntary written consent by patient or legally responsible representative * All women of childbearing potential and sexually mature males must be advised to use a medically accepted method of contraception throughout the study. * Negative pregnancy test (females) * Must not have received ERT for at least 6 weeks prior to AGT-181 treatment * Must have elevated urinary GAGs if no ERT has been received in the prior 3 months Exclusion Criteria: * Refusal to complete baseline evaluations. * Any medical condition or other circumstances that may significantly interfere with study compliance * Receipt of an investigational drug within the prior 90 days * History of diabetes mellitus or hypoglycemia * Clinically significant spinal cord compression, evidence of cervical instability. * Known hypersensitivity to alpha-L-iduronidase or any of the components of AGT-181. * Known to be nonresponsive to standard ERT treatment. * Previously successful (engrafted) hematopoietic stem cell transplantation that resulted in normalization of urinary GAGs. * Contraindication for lumbar puncture