ABSTRACT
Among the microorganisms, viruses have the simplest of structures. Despite this, they are the cause of a number of diseases, wherein the discovery of new antivirals is one of the most difficult tasks in medicinal chemistry. There are several approved drugs for numerous pathological conditions caused by viral agents. At the same time, there is a significant lack of effective treatments. Furthermore, many diseases remain without any specific treatment, due to several factors that make it difficult. In this context, this chapter addresses the main difficulties encountered in the discovery of antiviral agents, as well as some analogs that could overcome such limitations, which can be useful against herpes, influenza, coronavirus, human immunodeficiency virus, hepatitis B, dengue, Ebola, and Lassa. In fact, one of the main limitations for designing new antivirals is related to the rapid emergence of virus resistance to drugs. Thus, there is considerable need for new scaffolds that can overcome this enormous challenge. Furthermore, low bioavailability of nucleoside analogs and low quality in vitro assays are among the major limitations found currently. Finally, we hope that this chapter encourages medicinal chemists around the world to find possibilities to overcome these limitations by developing new methodologies for testing compounds and designing new chemical agents that could represent future treatments for these diseases.