#$%^&*AU2016202625A120160519.pdf#####ABSTRACT Provided herein are methods and compositions for treating a subject suffering from a deficiency in a-L-Iduronidase in the CNS. The methods include systemic administration of a bifunctional fusion antibody comprising an antibody to a human insulin receptor and an a-L-Iduronidase. A therapeutically effective systemic dose is based on the specific CNS uptake characteristics of human insulin receptor antibody-at-LIduronidase fusion antibodies as described herein. 7671816_1 (GHMatters) P83171.AU.2