Applications for Activity-based Probes in Drug Discovery
The path to a new therapeutic drug is long and difficult and involves many stages including validation of a target, design and selection of a lead compound and finally development of the lead into a drug. This chapter will discuss a relatively new technology that makes use of small molecules termed activity based probes (ABPs). These probes bind in the active site of a target enzyme or class of enzymes in an activity dependent fashion. Thus probe labeling serves as an indirect readout of enzyme activity, allowing the dynamic regulation of the target enzyme to be monitored using a number of biochemical and cell biological methods. In addition, labeled targets can be directly isolated by affinity methods, thereby allowing identification of potentially valuable drug targets based solely on their ability to bind a small molecule. Finally, because of the high degree of selectivity of ABPs for a given target protein class, they can be used for studies of drug binding and efficacy in complex cellular mixtures, intact cells and even in whole animals. These attributes of ABPs make them extremely valuable reagents for use at multiple points in the drug discovery process.