Synthetic Proteins Engineered for the Modulation of Cell Signaling

Abstract

Over the last decade, therapeutic monoclonal antibodies represent one of the major breakthroughs for the treatment of cancer and other diseases. To date, most therapeutic antibodies have been obtained by the humanization of rodent-derived antibodies, but in recent years, research in antibody engineering has given rise to a new wave of technologies that promise to transform the field. Phage-displayed libraries of “synthetic antibodies” use entirely man-made antigen-binding sites and thus circumvent the need for natural immune repertoires. Using in vitro selections, highly functional antibodies with fully human frameworks can be generated against virtually any antigen in a matter of weeks. Access to the encoding DNA allows for rapid affinity maturation, fine tuning of specificity and recasting into different molecular formats. We have developed particularly simple synthetic antibodies that use a single human framework and limited chemical diversity in restricted regions of the antigen-binding site. These structural simplifications enhance the performance of the libraries, which have yielded highly functional and stable antibodies against numerous diverse antigens. These libraries are capable of fulfilling all of the roles of natural antibodies, and furthermore, they extend the use of antibody technologies to many challenging problems, such as the recognition of conformational changes, post-translational modifications, structured nucleic acids and integral membrane proteins. Moreover, the recombinant nature of synthetic antibodies makes them ideal reagents that can be used as crystallization chaperones to aid the elucidation of structures for complex antigens. Extending the synthetic concept even further, we have developed novel binding scaffolds that enable applications beyond the range of antibodies, and these include the development of scaffolds that can be synthesized completely using peptide chemistry and scaffolds that fold and function inside cells.