Drug repurposing, or repositioning, is the development of existing drugs for new uses: given that 9 in 10 drugs that enter drug development are never marketed and therefore represent wasted effort, it is an attractive as well as inherently more efficient process. Three repurposed drugs can be brought to market for the same cost as one new chemical entity, and they can also be identified more quickly, an important benefit for patients whose diseases are progressing faster than therapeutic innovation. But repurposing also requires a fresh look at configuring pharmaceutical R&D, , considering clinical, regulatory and patent issues much earlier than would otherwise be the case. In addition to new ways of thinking, the discovery of repurposing opportunities can take advantage of artificial intelligence techniques to match the perfect new use for an existing drug. This book provides an ideal introduction to the field of drug repurposing with contributions from world-renowned experts culminating in an excellent resource for any drug discovery or medicinal chemist.