PolyXen is a patent-protected enabling platform technology designed for protein or peptide therapeutics. It uses the natural polymer polysialic acid (PSA) to prolong a drug's circulating half-life and potentially improve other pharmacological properties. PolyXen has been demonstrated in human clinical trials to confer extended half-life to biotherapeutics such as recombinant human erythropoietin and recombinant Factor VIII (rFVIII).