DRUG REPURPOSING: A PHARMACEUTICAL CHEMISTRY APPROACH FOR THE DISCOVERY OF NEW THERAPEUTIC APPLICATIONS

Drug discovery is a lengthy, expensive, and complex process involving target identification, lead optimization, preclinical evaluation, clinical trials, and regulatory approval. Drug repurposing, also known as drug repositioning, provides an alternative strategy in which an existing drug or previously investigated compound is developed for a new therapeutic indication. Because repurposed drugs have already undergone substantial pharmacological and toxicological evaluation, the approach can potentially reduce the time, cost, and risk associated with conventional drug development. Pharmaceutical chemistry plays an important role in drug repurposing through the investigation of molecular structure, structure–activity relationships, drug–target interactions, molecular docking, pharmacophore modelling, quantitative structure–activity relationship studies, and absorption, distribution, metabolism, excretion and toxicity prediction. Computational approaches have further expanded the ability to identify new targets and therapeutic applications for existing drugs. This review discusses the principles of drug repurposing, its pharmaceutical chemistry perspective, major computational approaches, advantages, limitations, and representative examples. The integration of pharmaceutical chemistry with computational drug discovery, artificial intelligence, and systems biology may provide an efficient strategy for identifying new therapeutic applications of established medicines.