Discovery and Optimization of IRBM-Z-2, an Allosteric Zika Virus NS2B-NS3 Protease Inhibitor Exhibiting In Vivo Efficacy

Zika virus is an increasing medical and socio-economic burden in (sub)tropical regions, with no effective treatments available. Previously, we identified a novel series of N-carbamoylsydnone imine derivatives as potent ZIKV NS2B-NS3 protease inhibitors through phenotypic antiviral screening. Here, we report the optimization of this series, leading to IRBM-Z-2, a nanomolar inhibitor active in both biochemical and cellular assays, exhibiting no cytotoxicity. IRBM-Z-2 demonstrates favorable oral bioavailability, low clearance, and strong prophylactic efficacy in mouse models of ZIKV infection. These results highlight IRBM-Z-2 as a promising therapeutic candidate against ZIKV and a potential foundation for developing broad-spectrum orthoflavirus agents.