Chapter Eleven - Fragment-Based Lead Discovery

Abstract Since its inception in the late 1990s, fragment-based lead discovery (FBLD) has developed into a robust and generic approach for drug discovery. Two clinically approved drugs have been developed using the FBLD approach, and at least 30 FBLD-derived compounds are in various stages of clinical development. Based on the principle of the identification of small (and hence typically low affinity) ligands which make well-defined interactions with the receptor, and the evolution of these initial fragment hits into larger, more potent ligands that maintain these key interactions, FBLD has proven to be a reliable technique which is applicable to wide range of targets. In this chapter, we will discuss the philosophy and rationale underpinning the FBLD approach, theoretical and practical considerations of fragment library design, fragment screening and characterization, and the evolution of initial low molecular weight fragment hits into larger, potent molecules suitable for lead optimization and preclinical development. We will also discuss informative case histories, showing the challenges, pitfalls, and successful approaches, which have been applied to a number of therapeutically relevant targets.