Volker Schellenberger is President and CEO of Amunix Operating Inc., which he co-founded together with Willem Pim Stemmer in 2006. He initially served as Amunix’ Chief Scientific Officer and is the lead inventor of the company’s XTEN technology. He has over 20 years of industry experience in protein engineering and drug discovery. Prior to co-founding Amunix he served as head of Genencor’s protein engineering department where he invented combinatorial consensus mutagenesis, selection by micro-compartmentalization as well as mutator technology. He focused on the discovery and engineering of antibody-enzyme fusion proteins. Prior to his work on biotherapeutics, he led projects optimizing enzymes for industrial applications as well as microbes for metabolic pathway engineering. He received his PhD from Leipzig University(Germany) in 1986 for studies on protease catalyzed peptide synthesis. After Postdoctoral work 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. He is author of over 40 scientific papers and inventor of more than 70 issued or pending patent applications. He is a recipient of the Karl Lohmannprize of the German Society of Biochemists.


PEGylation is commonly used to generate long-acting biologics (Biobetters). However, there are increasing concerns about the safety of PEG resulting from its resistance to being metabolized resulting in the accumulation in various organs including the kidney and brain. PEG is further limited by its polydispersity as well as an increasing risk of pre-exposure caused by the use of PEG in many cosmetics. Amunix has developed XTEN, a protein-based polymer that mimics the biophysical properties of PEG. XTEN is easily metabolized, thereby eliminating the risk of tissue accumulation. Proteins and peptides can be genetically fused to XTEN in a precisely controlled locations to increase biological half-life. XTEN polymers can also be produced by large scale microbial fermentation enabling chemical conjugation similar to PEGylation. XTEN has been successfully applied to a wide range of biotherapeutics and the most advanced product, human growth hormone-XTEN, VRS-317, is currently in late stage clinical testing.