This book reviews the current landscape of antiviral drug discovery with a strong focus on viral enzymes as therapeutic targets. It presents a timely, mechanism‑driven overview of approved drugs, clinical candidates, and emerging inhibitor classes developed against major human pathogens, including HIV‑1, SARS‑CoV‑2, West Nile virus, Crimean‑Congo hemorrhagic fever virus, and other hemorrhagic fever viruses. By integrating historical perspectives with recent breakthroughs, the volume highlights both the progress achieved and the challenges that remain in antiviral therapeutics.

The chapters cover key viral targets such as integrase, polymerase, helicase, RNase H, and viral proteases, discussing their structure, function, and role in viral replication. Several contributions focus on SARS‑CoV‑2, addressing polymerase, helicase, and protease inhibitors, while others examine antiviral strategies for flaviviruses and emerging hemorrhagic fever viruses that still lack effective treatments. Together, the chapters provide a coherent overview of target‑based antiviral research across diverse virus families.

This book appeals to researchers, advanced students, and professionals in medicinal chemistry, virology, pharmacology, and drug discovery, as well as to clinicians and translational scientists seeking an up‑to‑date reference on antiviral targets and inhibitor development for both established and emerging viral infections.

Erik De Clercq is Emeritus Professor of KU Leuven (Belgium), and has, since 2007 been teaching the course of “Chemistry at the Service of Medicine” at the Faculty of Sciences at the University of South Bohemia (Cěske Budéjovice, Czech Republic) in a joint program with Keppler University (Linz, Austria). He received the Dr. Paul Janssen Award for Biomedical Research in 2010 jointly with Dr. Anthony S. Fauci. He has (co)discovered a number of antiviral drugs currently used in the treatment of HSV (valaciclovir), VZV (brivudin), CMV (cidofovir), HBV [adefovir dipivoxil, tenofovir disoproxil fumarate (TDF) and tenofovir alafenamide (TAF)], and HIV infections (TDF, TAF). The combination of TDF with emtricitabine (Truvada) has been approved worldwide for the prophylaxis of HIV infections.