Heparosan, a promising 'naturally good' polymeric conjugating vehicle for delivery of injectable therapeutics.

Many therapeutics have issues with delivery due to nonoptimal pharmacokinetics and/or detrimental side effects due to their nonhuman nature. Injectable biologic drugs are one class that often needs assistance. The pharma industry has employed a variety of delivery strategies and this Editorial focuses on drug-polymer conjugates, in particular those utilizing a newly introduced system using a natural carbohydrate called heparosan. This molecule, the biosynthetic precursor to the well-known drug heparin, appears tolerated due to its 'self' nature as well as exhibits intrinsically favorable behavior in the bloodstream and tissues. The polysaccharide is stable in the extracellular spaces of mammals, but degraded by lysosomal enzymes following entry into the cell. Heparosan manufacture utilizes a novel synchronized, stoichiometrically controlled reaction employing a sugar-polymerizing enzyme in an aqueous buffer system that results in a quasi-monodisperse product. Heparosan is predicted to serve as a conjugating vehicle to extend the plasma half-life of biologics without liabilities of polydispersity, immunogenicity and/or unwanted accumulation in the body that are observed for other types of polymer such as PEG, hydroxyethyl starch, or poly(sialic acid).