Drug repurposing ("old drugs, new uses") is currently a high-profile R&D strategy, which involves applying existing drugs to new indications, focusing on marketed drugs or clinical-stage drugs. Since there is already considerable understanding of the tolerance, human delivery characteristics, and kinetics of these drugs, they can be used more effectively and safely. More importantly, compared to de novo drug R&D, the time and economic costs required for drug repurposing are relatively much smaller. With the development of big data analysis, computer models, and large-scale screening systems, drug repurposing will become even more attractive.