Why is Drug Repurposing Relevant?
The drug development process takes ten to fifteen years on average and costs anywhere from $113 million to upwards of $6 billion to produce a single drug.2,3 An NCE could be millions of dollars and several years into development before it fails in a clinical trial, putting companies out a considerable investment and leaving patients years away from relief. Given this fact, drug repurposing provides a possible avenue to help both researchers and patients. Finding new uses for pre-existing drugs is also an opportunity to further understand disease biology. Though drug repurposing can cut costs for pharmaceutical companies, there is still further investment and risk involved as trials can still fail down the line. In a perfect world, all drugs on the path to repurposing would have already passed safety and efficacy testing and be active in the same concentration range as the original intended use, 1 thus providing an excellent jumping-off point for researchers that would “bypass” many of the safety testing regulations necessary in the drug development process.
The Methods of Drug Repurposing
Drug repurposing methodologies make use of a range of available pathways, mechanisms, or -omics data. Some computational methods such as Blinded Search require little chemical data and utilize serendipitous identification or phenotypic screening to identify targets, whereas the Signature-Based method utilizes gene signatures from disease -omics data to identify previously unrecognized drug targets or mechanisms.4 Another methodology, Target-based Screening, consists of in vitro/in vivo high throughput screening (HTS) and in silico screening of drug compound libraries, allowing researchers to screen drugs with known chemical structures in record time.4 Targeted-mechanism-based Screening utilizes treatment -omics data, protein interaction data, and signaling pathway information to not only characterize unknown drug mechanisms but also identify new mechanisms related to diseases and drugs.4 Blinded Method is used for compounds where little to no mechanistic knowledge exists and can be applied to a wide variety of drugs and diseases. Finally, Knowledge- or Target-based methods utilize available data to construct new mechanisms and identify different pathways.4 In addition, individual methods from this array of options can be combined and tailored for specific drug screening processes depending on the data available for one’s study.