Modification of N-hydroxycytidine yields a novel lead compound exhibiting activity against the Venezuelan equine encephalitis virus

Nucleoside and nucleobase analogs capable of interfering with nucleic acid synthesis have played essential roles in fighting infectious diseases. However, many of these agents are associated with important and potentially lethal off-target intracellular effects that limit their use. Based on the previous discovery of base-modified 2′-deoxyuridines, which showed high anticancer activity while exhibiting lower toxicity toward rapidly dividing normal human cells compared to antimetabolite chemotherapeutics, we hypothesized that a similar modification of the N4-hydroxycytidine (NHC) molecule would provide novel antiviral compounds with diminished side effects. This presumption is due to the substantial structural difference with natural cytidine leading to less recognizability by host cell enzymes. Among the 42 antimetabolite species that have been synthesized and screened against VEEV, one hit compound was identified. The structural features of the modifying moiety were similar to those of the anticancer lead 2′-deoxyuridine derivative reported previously, providing an opportunity to pursue further structure–activity relationship (SAR) studies directed to lead improvement, and obtain insight into the mechanism of action, which can lead to identifying drug candidates against a broad spectrum of RNA viral infections.