Anti-infective agents have been one of the greatest accomplishments of
modern medicine, which has led to a decrease in the number of deaths caused by
various infectious diseases. The anti-infective agents are a broad family consisting of
antimicrobials, antifungals, antimalarials, antiprotozoal, antituberculosis, and antiviral
agents. Viral infections have caused millions of casualties worldwide, leading to the
need for the development of effective antiviral agents. Although the replication
mechanism differs significantly between the viruses, all viruses undergo steps like
attachment, entry, genome replication, gene expression, and assembly for the release of
the virions into the body of the host. Treatment with antiviral agents is essential for
blocking the replication of the virus, and the currently available antiviral therapies are
directed according to the disease. Furthermore, the treatment with antiviral agents aims
to eradicate the viral pathogen from the host and prevent the clinical manifestation.
Infectious diseases, such as human immunodeficiency virus (HIV), hepatitis B, and
hepatitis C virus (HBV and HCV), and influenza, are of significant global concern. On
the contrary, the outbreak of newer strains of influenza virus and Zika virus, Ebola
virus, strains of coronavirus (CoV) like severe acute respiratory syndrome (SARS –
CoV), Middle East respiratory syndrome (MERS – CoV) and novel Coronavirus
(2019-nCoV) are life-threatening viral infections that exhibit major challenges to the
humanity. As of date, multiple effective virostatics that target specific viral replication
steps are approved for the treatment of viral infections. However, the use of such
agents is restricted given the rapid emergence of antiviral resistance, which remains a
major concern of current antiviral therapy. In this chapter, we summarize recent
antiviral agents that show promising clinical benefits in various phases of clinical trials
and also consider them as potential therapeutic agents in the future. Besides, we
highlight and analyze the development of novel inhibitors targeting various stages of
the viral life cycle that act by distinct mechanisms against current and emerging viral
infections. Many antiviral drugs currently available are based on the concept of
traditional chemotherapy. Nevertheless, new developments and advances in molecular
biology have opened up possibilities to alternate treatment approaches. Clinical trials to
evaluate gene silencing mediated by small interfering RNA (siRNA) and antisense
RNAs expression against infection with a respiratory syncytial virus (RSV) have
recently been initiated. Moreover, in–vitro studies of antisense RNA or siRNA technology have shown promising results in various virus strains. Despite the recent
advancements, the development of targeted delivery of antiviral RNA molecules
remains a major challenge since DNA viruses and retroviruses can incorporate their
genomes into human genomes. To emphasize, antiviral drugs against particular target
proteins have been effective in the treatment of prevalent infectious diseases such as
HIV and HCV. Thereupon, broad-spectrum antiviral drugs instead of antivirals against
specific virus infections need to be designed. With the rapid development of in-silico
tools and gene modification strategies, antiviral drugs with better therapeutic index and
safety profile will be developed against infectious diseases in the future. In fact, the
effective design of newer antiviral drugs will reduce the possibility of emerging
antiviral resistance.
Keywords: Antivirals, Clinical trials, Coronavirus, Human immunodeficiency
virus, Middle East respiratory syndrome, Pharmacotherapy, Respiratory syncytial
virus.
