A significant advantage of drug repositioning over traditional drug development is that since the repositioned drug has already passed a significant number of toxicity and other tests, its safety is known and the risk of failure for reasons of adverse toxicology are reduced. More than 90% of drugs fail during development,^[2] and this is the most significant reason for the high costs of pharmaceutical R&D. In addition, repurposed drugs can bypass much of the early cost and time needed to bring a drug to market. It significantly reduces the transition of bench research work to treatment at bedside. On the other hand, drug repositioning faces some challenges itself since the intellectual property issues surrounding the original drug may be complex and from a commercial point of view it may not always make sense to take such a drug to market.

Drug repositioning has been growing in importance in the last few years as an increasing number of drug development and pharmaceutical companies see their drug pipelines drying up and realize that many previously promising technologies have failed to deliver ‘as advertised’. Computational approaches based on virtual screening of comprehensive libraries of approved and other human use compounds against large numbers of protein targets simultaneously have been developed to enhance the efficiency and success rates of drug repositioning, particularly in terms of high-throughput shotgun repurposing.^[3][4][5]