Synthesis and characterization of heparosan-granulocyte-colony stimulating factor conjugates: a natural sugar-based drug delivery system to treat neutropenia

Glycobiology. 2017 Nov 1;27(11):1052-1061. doi: 10.1093/glycob/cwx072.


Many injectable drugs require delivery strategies for enhancing their pharmacokinetics due to rapid loss via renal filtration if possess low molecular weight (<60-70 kDa) and/or clearance by the body's components (e.g., proteases, antibodies, high-efficiency receptors) in their native form. FDA-approved polyethylene glycol (PEG) is a vehicle for improving therapeutics, but artificial polymers have potential biocompatibility and immunogenicity liabilities. Here, we utilized a natural vertebrate carbohydrate, heparosan (HEP), the biosynthetic precursor of heparan sulfate and heparin, to enhance performance of a biologic drug. The HEP polysaccharide was stable with a long half-life (~8 days for 99-kDa chain) in the nonhuman primate bloodstream, but was efficiently degraded to very short oligosaccharides when internalized by cells, and then excreted into urine and feces. Several HEP-modified human granulocyte-colony stimulating factor (G-CSF) conjugates were synthesized with defined quasi-monodisperse HEP polysaccharide chains. Single dosing of 55- or 99-kDa HEP-G-CSF in rats increased blood neutrophil levels comparable to PEG-G-CSF conjugates. Repeated dosing of HEP-G-CSF or HEP alone for 2 weeks did not cause HEP-specific toxic effects in rats. HEP did not possess the anticoagulant behavior of its daughter, heparin, based on testing in rats or clinical diagnostic assays with human plasma. Neither anti-HEP IgG nor IgM antibodies were detected in a long-term (9 doses over 7 months) immunogenicity study of the HEP-drug conjugate with rats. These proof-of-concept experiments with HEP-G-CSF indicate that it is a valid drug candidate for neutropenia and suggest the potential of this HEP-based platform as a safe alternative delivery vehicle for other therapeutics.

Keywords: chemoenzymatic synthesis; glycosaminoglycans; heparosan/heparan sulfate; pharmacokinetics; polyethylene glycol.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Blood Cells / drug effects
  • Disaccharides / adverse effects
  • Disaccharides / chemistry
  • Disaccharides / pharmacokinetics*
  • Drug Carriers / adverse effects
  • Drug Carriers / chemistry
  • Drug Carriers / pharmacokinetics*
  • Granulocyte Colony-Stimulating Factor / administration & dosage
  • Granulocyte Colony-Stimulating Factor / chemistry
  • Granulocyte Colony-Stimulating Factor / pharmacokinetics*
  • Humans
  • Macaca
  • Male
  • Neutropenia / drug therapy*
  • Rats


  • Disaccharides
  • Drug Carriers
  • heparosan
  • Granulocyte Colony-Stimulating Factor