About Us


Amunix was founded in 2006 by Willem 'Pim' Stemmer and Volker Schellenberger. It has now grown to encompass 30 employees, a dedicated in-house patent attorney, and over 12,000 square feet of research labs. Our primary focus continues to be the design and preclinical development of protein pharmaceuticals with extended serum half-lives through the application of our XTEN technology platform. Central to our platform, XTEN is a hydrophilic, unstructured polypeptide which imparts a number of favorable properties to the molecules to which it has been fused. By conjugating existing, clinically tested drugs to XTEN through a process called XTENylation, we are able to generate improved versions of these products, or "biosuperiors". Besides the advantages of a lower dosing frequency, XTENylation stabilizes plasma drug concentrations, minimizing side effects which include toxicity and reduced efficacy.



Create and develop novel versions of clinically proven pharmaceutical products that offer better efficacy, safety, and dosing frequency by extension of the serum half-life. Partner with leading companies to facilitate the broad application of XTENylation to a wide range of therapeutics.

Our employees are essential for the success of the company.  Amunix offers excellent opportunities for our employees to grow within the organization while building a thriving enterprise.



Volker Schellenberger, Ph.D., CEO

Volker has 18 years of industry experience in protein engineering and drug discovery. He headed Genencor’s Protein Engineering department, where he invented combinatorial consensus mutagenesis, selection by micro-compartmentalization as well as mutator technology. In addition, he initiated and led a collaboration with Seattle Genetics, that focused on antibody-enzyme fusion proteins. Prior to his work on biotherapeutics, Volker led projects optimizing enzymes for industrial applications as well as microbes for metabolic pathway engineering. Volker received his Ph.D. from Leipzig University in 1986 for studies on protease catalyzed peptide synthesis. After postdoctoral studies at the Institute for Protein Research in Pushchino (Russia), he moved to the University of Göttingen where he developed a novel method for the production of peptides from recombinant peptide-multimers. After a postdoc with Bill Rutter at the University of California, San Francisco he joined Genencor in 1994. Volker is the author of over 40 scientific papers and inventor of more than 70 issued or pending patent applications. He is also the recipient of the Karl Lohman award of the German Society of Biochemists.



Amunix has no external investors.

Amunix has created separate companies with focus on the clinical development of its XTEN products. Investors in Diartis Inc. (www.diartispharma.com), which has completed a Phase I trial of Exenatide-XTEN, are Index Ventures and Amunix. Investors in Versartis Inc. (www.versartis.com), which has completed a Phase I trial of human growth hormone-XTEN, are Advent Venture Partners, Index Ventures, and New Leaf Venture Partners.