Drug Repositioning as an Antiviral Strategy Against Emerging Viruses

Throughout history, the world has faced various pathogens that have wreaked significant havoc on human and animal health. Among those pathogens, viruses have generated the highest lethality. Latin America has faced not only the viruses that afflict the entire world but also those infections transmitted by vectors present in the continent, given its climate and fauna. In this sense, in recent years, the emerging viruses that have caused large epidemics or pandemics with significant public health, economic, and social impact are RNA viruses, most of them zoonotic and arthropod-borne viruses. Drug repositioning is the use of existing drugs to treat diseases different from the initial indication of the drug. Currently, repositioning drugs already approved for use in humans is a helpful tool to search for new therapeutic options, particularly in emerging viral diseases for which no vaccine or effective antiviral treatments exist. Many studies have shown that FDA-approved drugs have antiviral activity against some of the emerging RNA viruses. Hence, this chapter aims to discuss the current findings about the different FDA-approved drugs with activity against important emerging viruses in Latin America. For example, for dengue and other related flaviviruses, drugs used to treat parasitic diseases, such as ivermectin, that alter cellular nucleocytoplasmic transport and the nuclear import of viral proteins inhibit the viral infection; furthermore, drugs used to reduce lipid levels, such as statins, can alter the disposition of receptors in lipid rafts or arrest the synthesis of cellular cholesterol, inhibiting viral entry and viral particle morphogenesis, respectively. Thus, repositioning drugs with antiviral activity can be a first line for treating emerging viral diseases.