Efficacy of repurposed antiviral drugs: Lessons from COVID-19.

The clinical, social, and economic impacts of the coronavirus disease 2019 (COVID-19) pandemic, originated by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), have motivated a massive search and investment to find treatments for this new disease. Repurposing drugs has been an appealing strategy for the rapid translation of in vitro and ex vivo drug discovery to the clinic. Several repurposed drugs have been assessed clinically, but no effective repurposed antiviral has been identified so far. Of note, no effective treatments for COVID-19 or for any other viral disease have been found by repurposing drugs identified through hypothesis-free screens. Here, I discuss whether drug repurposing is the best strategy for developing effective therapies to eradicate COVID-19 and other viral human infections.