Expression in CHO cells and pharmacokinetics and brain uptake in the Rhesus monkey of an IgG‐iduronate‐2‐sulfatase fusion protein

Abstract

Sulfatases are potential therapeutic biopharmaceuticals, as mutations in sulfatase genes leads to inherited disease. Mucopolysaccharidosis (MPS) Type II is caused by mutations in the lysosomal enzyme, iduronate-2-sulfatase (IDS). MPS-II affects the brain and enzyme replacement therapy is ineffective for the brain, because IDS does not cross the blood-brain barrier (BBB). To deliver IDS across the human BBB, the sulfatase has been re-engineered as an IgG-sulfatase fusion protein with a genetically engineered monoclonal antibody (MAb) against the human insulin receptor (HIR). The HIRMAb part of the HIRMAb-IDS fusion protein acts as a molecular Trojan horse to ferry the fused IDS across the BBB. Chinese hamster ovary (CHO) cells were stably transfected to produce the HIRMAb-IDS fusion protein. The fusion protein was triaged to the lysosomal compartment of MPS-II fibroblasts based on confocal microscopy, and 300 ng/mL medium concentrations normalized IDS enzyme activity in the cells. The HIRMAb-IDS fusion protein was tritiated and injected intravenously into the adult Rhesus monkey at a low dose of 0.1 mg/kg. The IDS enzyme activity in plasma was elevated 10-fold above the endogenous level, and therapeutic plasma concentrations were generated in vivo. The uptake of the HIRMAb-IDS fusion protein in the brain was sufficiently high to produce therapeutic concentrations of IDS in the brain following IV administration of the fusion protein.