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.