Methodologies Adopted in Drug Repurposing

Drug repurposing is using an existing medicine for a new therapeutic purpose. This drug discovery approach is cost-effective and time-saving, increasing the likelihood of a drug being approved. Additionally, it has the potential to expedite the discovery and development of new treatments, which could benefit patients by providing more treatment options and reducing the time and costs associated with bringing new drugs to market. Any medicine, whether it has been approved or not, can be repurposed, including those that have been withdrawn from the market. From sildenafil, the oldest repurposed medication, to tocilizumab for treating COVID-19, there is an extensive list of repurposed medicines. Identifying a potential drug candidate through computational or experimental methods, accessible internet drug databases, primary and translational research, clinical trial outcomes, off-label usage anecdotes, and other relevant human data is a crucial step. In this process, Artificial Intelligence (AI), bioinformatics, genetic data, clinical analysis, molecular docking, pathways, signatures, targets, phenotypes, and binding tests can help understand drug–protein interactions. The current chapter explores drug repurposing methods, repurposed medicines in the market and their indications, the obstacles faced by the community, and possible solutions for maximizing the potential of this approach.