We live in an unprecedented era in the antiviral drug discovery. The first antiviral therapies became available about 50 years ago with the introduction of drugs such as idoxuridinefor the treatment of herpetic keratitis and methisazone for the treatment and prophylaxis of smallpox and variola infection. Almost two decades later, the discovery of ACV (acyclovir) ushered in a new era of antivirals. One of the subsequent big milestones was heralded by the discovery of AZT (zidovudine), approved in 1987 for use against HIV, followed by more than two decades of an intense antiretroviral drug discovery effort, which resulted in more than 20 new U.S. Food and Drug Administration (FDA)