ABSTRACT
Screening advanced compounds enables discovery of direct repurposing candidates, novel drug-like leads for optimization, and informative pharmacological probes. In this chapter, we describe different types of screening collections used in drug repurposing, discuss issues and considerations in preparing and executing a repurposing screen, and present examples of in vitro and in vivo repurposing assays. We further describe various data sources reporting information on de-risked compounds of different types and illustrate how data mining and chemoinformatic and chemogenomic searches can be used to access large numbers of advanced compounds and assemble collections most suitable for screening in a given disease model. We argue that a view of repurposing screening as a large-scale bet on finding candidates for clinical testing is narrow and incomplete. Rather, when thoughtfully executed, screening of re-risked compounds is informed by target pathobiology and offers a means to efficiently convert advances in the development of sophisticated non-clinical models and new insights in disease mechanisms into novel drug-like leads and candidates for development.