Repurposing old drugs for a new cause
Drug repurposing has emerged as an attractive alternative to the conventional approach of drug discovery which is often exhaustive and arduous (Ashburn & Thor, 2004). It is a process of identifying new therapeutic roles for a drug that has already been established for the treatment of another condition. The discovery of a new drug and its journey to the market is a process fraught with risks involving toxicity and lack of efficacy, costing billions of dollars and requiring a long timeline. Repurposing therefore offers several advantages over de novo drug development, such as reduced development timelines, reduced costs and substantially lower risks, as the safety and pharmacokinetic profile of the drug is already established (Pushpakom et al., 2019). The risk of failure is lower because the repurposed drug has been shown to be safe in pre-clinical models and humans, provided early‐stage trials have been completed. As a result, the timeframe for drug development is significantly shorter (Breckenridge & Jacob, 2019).
Historically, drug repurposing has been mostly serendipitous, usually after a drug was found to have a newly recognized on‐target effect (Nosengo, 2016). However, recent successes have encouraged the development of more systematic approaches (Hurle et al., 2013). These approaches have resulted in the identification of a number of promising candidate drugs. In more recent years, drug repurposing screens have emerged as an attractive strategy to respond swiftly to emerging infectious diseases (Ashburn & Thor, 2004). Food and Drug Administration (FDA) approved drugs which can achieve a modest antimicrobial activity are a safe and increasingly popular response mechanism to emerging infections. The drugs concerned can become immediately available for use in clinical trials as they have known safety profiles at the licensed doses and this has had a huge impact during the COVID-19 pandemic.