Synthesis and antiviral activity of 5-substituted cytidine analogues: identification of a potent inhibitor of viral RNA-dependent RNA polymerases.

As part of our studies of lethal viral mutagens, a series of 5-substituted cytidine analogues were synthesized and evaluated for antiviral activity. Among the compounds examined, 5-nitrocytidine was effective against poliovirus (PV) and coxsackievirus B3 (CVB3) and exhibited greater activity than the clinically employed drug ribavirin. Instead of promoting viral mutagenesis, 5-nitrocytidine triphosphate inhibited PV RNA-dependent RNA polymerase (K(d) = 1.1 +/- 0.1 microM), and this inhibition is sufficient to explain the observed antiviral activity.