Chapter 17 - New targets for old drugs: drug repurposing approach for accelerating the drug discovery engine with minimum financial inputs

Abstract

Drug repositioning (DR) is the process of finding new clinical indications for existing drugs (Nosengo, 2016; Corsello et al., 2017). In the current “target rich-lead poor” scenario of drug discovery, the repurposing or repositioning is gaining increasing interest over the traditional de novo drug discovery, which is more time-consuming (13–15 years) and expensive (US$ 2–3 billion) (Nosengo, 2016). At present, there are over 20,000 drugs prescribed by medical practitioners and approved by the FDA. The majority of the FDA-approved drugs have been tailored against a specific target, but more than one molecular target can potentially be affected by most small inhibitor molecules (Nosengo, 2016; Corsello et al., 2017). Owing to the nonaffordable prices of anticancer drugs, the slow pace of anticancer drug discovery and development, and evolving drug resistance, there is a need to develop novel drug candidates against deadly human diseases through a strategic drug development process. The DR tackles two main problems in the pharmaceutical industry such as the cost and time required to develop new drugs. The safety and efficacy of FDA-approved drugs have been already accessed; therefore, repurposing accelerates the discovery and drug development process (Pushpakom et al., 2019). Furthermore, the risk of failure in clinical trials and the timeframe from discovery to approval of drugs decides the overall costs of drugs from bench to bedside and which is lower in the case of repurposed drugs as compared to new or previously untested drugs (Nosengo, 2016; Corsello et al., 2017). Therefore, repurposing is a suitable strategy to discover new indications for existing drugs to treat various human diseases within a short timeframe and cost-effective manner.