Drug Repurposing in Cancer Therapy

Cancer is the global burden of disease. Within the therapeutic arsenal, there are several evolutions, starting from chemotherapy and radiation therapy to the implementation of nanotechnology, photo-thermal therapy, immunotherapy, and gene therapy. However, most available standard and novel therapies face economic challenges, and some suffer from regulatory burdens. New clonal aberrations, multidrug resistance, cyclic occurrence of mutation, and highly resistant gene mutations are the bouncers to therapeutic molecules. Moreover, new molecules with favorable properties will take a long time to complete the journey from lab to market. Drug repurposing has gained considerable momentum in the pharmaceutical industry and cancer therapy. Several successful stories exist in the cancer domain where drugs from antimicrobial, antifungal, antihyperlipidemic, antidiabetic, antiepileptic, etc. classes have shown positive results. Even some anticancer agents confirmed their potential effects in other cancers. Here, data mining approaches have been found rationale to provide strength in the repurposing pipeline. Especially if dose compatibility of the repurposed candidate is found for anticancer therapy at the equal or lower strength used for the original indication, the development becomes much easier. However, the safety and efficacy of new indications in cancer must be evaluated carefully at clinical levels. The chapter will briefly cover the challenges and opportunities of drug repurposing in different types of cancer, including the application of nanotechnology, the emergence of new tools, and omics approaches. The chapter will also highlight the importance of clinical trials in the lifecycle of a repurposed drug, along with the clinically approved repurposed candidates.