XTEN® is a proprietary recombinant polypeptide that extends the in vivo half-life of therapeutic payloads. XTEN consists of naturally-occurring hydrophilic amino acids and is biodegradable. Pharmaceuticals such as proteins, peptides, and synthetic compounds can be XTENylated via chemical conjugation or genetic fusion.

Overview of XTEN®

Short half-life and rapid degradation cause many therapeutics to fail in clinical trials.  Most natural peptides and proteins are rapidly cleared from circulation, requiring impracticably large and/or frequent doses for therapeutic activity. Maintaining drug concentration within the therapeutic window is critical, thus avoiding excessive toxicity or insufficient efficacy.

Amunix has developed a half-life extension technology based on XTEN, a hydrophilic polymer comprised of natural amino acids that can be attached to therapeutic peptides, proteins or small molecules through either chemical conjugation or genetic fusion. XTEN greatly increases the size of therapeutic molecules and prolongs their presence in serum. Compared with other half-life extension technologies, XTENylated products offer numerous benefits:


  • Exceptionally long half-lives
  • Precisely controlled sequence and length
  • Biodegradable
  • No toxic metabolites
  • Minimized immunogenicity
  • Chemical conjugation or genetic fusion attachment to therapeutics