Clinical Trials on Repurposed Drugs: An Overview

The de novo drug development process for a new chemical entity is expensive and time-consuming, failing to meet the demand for more effective therapies for emerging diseases in the current era. Drug repurposing has become more popular as an effective technique to discover novel treatment strategies for a plethora of disorders, intending to reduce both the time and expense involved with the process of drug development. Drug repurposing is the approach of utilizing existing medications for novel indications. According to the US FDA, repurposed drugs that might be able to circumvent the necessity for preclinical and phase 1 trials can be approved through an approach outlined under Section 505 (b) (2) of the Federal Food, Drug, and Cosmetic Act. Even though the repurposed pharmaceuticals may directly enter phase 2 trials, it was observed that many trials were initiated from phase 1. Most successful and old examples of drug repurposing mentioned in literature include sildenafil, aspirin, and zidovudine. The approval by the Food and Drug Administration (FDA) for the use of several repurposed drugs for COVID-19 treatment on an emergency basis has brought attention to the practice of drug repurposing. This book chapter presents comprehensive data regarding clinical trials of repurposed drugs targeting a range of conditions, including different types of malignancies, viral infections, cardiovascular disorders, and inflammatory diseases. For all disorders, the data is primarily from ClinicalTrials.gov, with assistance from the Redo Trials Database for cancer-related trials.