Favipiravir (T-705) is a nucleoside analog that was recently approved as an anti-influenza drug in Japan, and is in Phase 3 clinical trials in the USA for the same indication. It is active against a growing list of virulent RNA viruses including Ebola virus, and the author studies show that it is highly protective in rodent models of Argentine hemorrhagic fever (AHF), caused by Junin virus (JUNV). Favipiravir appears to act by directly inhibiting the viral RNA-dependent RNA polymerase (RdRP), with minimal effect on cellular nucleoside metabolism or intracellular nucleic acid pools. There is little evidence that resistant viruses are selected during the course of therapy, indicating that the drug's target site is essential for efficient virus replication.
