Mucopolysaccharidosis II (MPS II) or Hunter syndrome is an X-linked inherited lysosomal storage disease. This serious genetic disorder interferes with the body’s ability to break down and recycle specific mucopolysaccharides. It is caused by a defective or missing enzyme, iduronate-2-sulfatase (IDS). IDS is a large molecule unable to pass the brain-blood barrier (BBB), making enzyme replacement therapies impossible.

To solve this issue, William Pardridge, ArmaGen Technologies, Inc., Calabasas, CA, USA, and colleagues reengineered IDS by fusing it with a monoclonal antibody against the human insulin receptor (HIRMAb). HIRMAb has an innate ability to cross the BBB via receptor-mediated transport on the endogenous BBB insulin receptor, making it a perfect molecular Trojan horse to shuttle IDS from blood into brain.
The researchers conducted the first safety pharmacology and pharmacokinetics study of the HIRMAb-IDS fusion protein in juvenile male Rhesus monkeys by infusing them with it intravenously on a weekly basis for 26 days at 3–30 mg/kg doses.

Continuous monitoring of the plasma clearance, pharmacokinetic profile and immunogenicity of the HIRMaB-IDS in the tested animals demonstrated that the new drug is safe and efficient for use in primates. This makes it suitable for future clinical trials.

• Insulin receptor antibody-iduronate 2-sulfatase fusion protein: Pharmacokinetics, anti-drug antibody, and safety pharmacology in Rhesus monkeys,
  Ruben J. Boado, Eric Ka-Wai Hui, Jeff Zhiqiang Lu, William M. Pardridge,
  Biotechnol. Bioeng. 2014.
  DOI: 10.1002/bit.25289