Willem P. C. "Pim" Stemmer (12 March 1957 – 2 April 2013)[2] was a Dutch scientist and entrepreneur who invented numerous biotechnologies.
He was the founder and CEO of Amunix Inc., a company that creates "pharmaceutical proteins with extended dosing frequency".
He received a PhD from the University of Wisconsin for his work on bacterial pili and fimbriae involved in host-pathogen interactions.
Afterwards, he conducted postdoctoral research with Professor Fred Blattner on phage display of random peptide libraries and antibody fragment expression in E. coli bacteria.
[citation needed] He co-founded Amunix in 2006 together with Volker Schellenberger;[citation needed] its products comprise a "clinically proven pharmaceutical payload, typically a human protein, genetically fused to ‘XTEN’, a long, unstructured, hydrophilic protein chain", which prolongs serum half-life by "increasing the hydrodynamic radius, thus reducing kidney filtration".