PolyXen for Protein Drug Delivery

PolyXen is an enabling platform technology for protein drug delivery. It uses the biological polymer polysialic acid (PSA) to prolong the drug's half-life and potentially improve the stability of therapeutic peptides and proteins. Both the site of attachment and the length of the PSA chain can influence the properties of the therapeutic by changing the apparent hydrodynamic radius of the molecule, which in turn, can enhance a number of the biological characteristics of the therapeutic. It can also be used for small molecule drugs.

Benefits of PolyXen

Preclinical proof-of-concept studies and multiple clinical studies in humans have shown that the key benefits of PolyXen for protein drug delivery may include:

  • Preservation of drug functionality on conjugation
  • Improved stability in vivo
  • Prolonged pharmacological action
  • Prolonged active life of the drug in the blood circulation
  • Reduced frequency and amount of dosage
  • Reduced immunogenicity and antigenicity

PolyXen has been demonstrated in human clinical trials to confer extended half-life to biotherapeutics such as recombinant human erythropoietin (rhEPO) and recombinant Factor VIII (rFVIII).

Xenetic is leveraging PolyXen™ by partnering with biotechnology and pharmaceutical companies. The Company has an exclusive license agreement with Takeda Pharmaceuticals Co. Ltd. in the field of coagulation disorders and expects to earn royalty payments under this agreement.

What is polysialic acid?

Polysialic acid (PSA) is a polymer chain comprised of sialic acids linked together. Sialic acid is found on the external membrane of a number of cell types in the body. In addition, it is a natural component expressed on the external membrane on a number of bacterial types. When used for therapeutic protein and peptide drug delivery, PSA provides a protective microenvironment following conjugation to the active drug. This increases the active half-life of the therapeutic drug in the body and allows it to exist largely undetected by the immune system.

How does PSA work?


The PSA polymer is naturally found in the human body. However, PSA evolved initially as part of the coat on the external walls of certain bacteria, which are able to remain largely undetected by the immune system. Our partners are producing PSA from these bacteria in large quantities and with predetermined physical characteristics. Bacterial PSA is an ideal polymer for drug conjugation as it is biodegradable and non-immunogenic, even when coupled to proteins. This is particularly important when a polymer is being used to deliver therapeutics chronically or in large dosages.

How does PolyXen technology use PSA?

PolyXen uses proprietary techniques to conjugate PSA molecules of appropriate length to specific sites of the therapeutic molecule. The PSA molecules form a glycocalyx (a carbohydrate shield) around the therapeutic molecule, rendering it less exposed to the body's immune system, as well as less exposed to serum proteases and other clearance mechanisms, including renal clearance.

Learn more about PolyXen™

PolyXen™ Publications

Review our key scientific publications/presentations featuring our PolyXen technology.

Our Publications