PASylation: a biological alternative to PEGylation for extending the plasma half-life of pharmaceutically active proteins

Protein Eng Des Sel. 2013 Aug;26(8):489-501. doi: 10.1093/protein/gzt023. Epub 2013 Jun 10.


A major limitation of biopharmaceutical proteins is their fast clearance from circulation via kidney filtration, which strongly hampers efficacy both in animal studies and in human therapy. We have developed conformationally disordered polypeptide chains with expanded hydrodynamic volume comprising the small residues Pro, Ala and Ser (PAS). PAS sequences are hydrophilic, uncharged biological polymers with biophysical properties very similar to poly-ethylene glycol (PEG), whose chemical conjugation to drugs is an established method for plasma half-life extension. In contrast, PAS polypeptides offer fusion to a therapeutic protein on the genetic level, permitting Escherichia coli production of fully active proteins and obviating in vitro coupling or modification steps. Furthermore, they are biodegradable, thus avoiding organ accumulation, while showing stability in serum and lacking toxicity or immunogenicity in mice. We demonstrate that PASylation bestows typical biologics, such as interferon, growth hormone or Fab fragments, with considerably prolonged circulation and boosts bioactivity in vivo.

Keywords: biologic; dosing; kidney filtration; pharmacokinetics; therapeutic protein.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alanine / chemistry
  • Alanine / genetics
  • Amino Acid Sequence
  • Animals
  • Base Sequence
  • Cloning, Molecular
  • Escherichia coli / genetics
  • Growth Hormone / chemistry*
  • Growth Hormone / genetics
  • Growth Hormone / pharmacokinetics*
  • Half-Life
  • Humans
  • Immunoglobulin Fab Fragments / chemistry
  • Immunoglobulin Fab Fragments / genetics
  • Mice
  • Models, Molecular
  • Molecular Sequence Data
  • Peptides / chemistry*
  • Peptides / genetics
  • Polyethylene Glycols / chemistry*
  • Proline / chemistry
  • Proline / genetics
  • Protein Structure, Secondary
  • Recombinant Fusion Proteins / chemistry*
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / pharmacokinetics*
  • Serine / chemistry
  • Serine / genetics


  • Immunoglobulin Fab Fragments
  • Peptides
  • Recombinant Fusion Proteins
  • Polyethylene Glycols
  • Serine
  • Growth Hormone
  • Proline
  • Alanine