In vitro protein display in drug discovery

Nucleic acid-encoded libraries have been used at different stages of the drug discovery process for the identification of polypeptide ligands and for target identification. Traditionally, phage display screening systems have been used to explore large libraries of peptides and proteins. Lately, novel protein selection technologies have been developed that work entirely in vitro and use the polymerase chain reaction (PCR) rather than cells to amplify genetic material. The simplicity of the linkage between the protein and its encoding nucleic acid leads to several advantages, including the use of larger libraries without the biases of cell-based amplification, greater control over binding conditions and the ease with which PCR-based mutagenesis and recombination can be incorporated. This review focuses on the latest improvements in this new generation of in vitro protein display techniques and discusses their applications to the drug discovery process.