LAUSR

Abstract Many flaviviruses, such as Zika virus (ZIKV), Dengue virus (DENV1‐4) and yellow fever virus (YFV), are significant human pathogens. Infection with ZIKV, an emerging mosquito‐borne flavivirus, is associated with increased risk of microcephaly in newborns and Guillain‐Barré syndrome and other complications in adults. Currently, specific therapy does not exist for any flavivirus infections. In this study, we found that erythrosin B, an FDA‐approved food additive, is a potent inhibitor for flaviviruses, including ZIKV and DENV2. Erythrosin B was found to inhibit the DENV2 and ZIKV NS2B‐NS3 proteases with IC50 in low micromolar range, via a non‐competitive mechanism. Erythrosin B can significantly reduce titers of representative flaviviruses, DENV2, ZIKV, YFV, JEV, and WNV, with micromolar potency and with excellent cytotoxicity profile. Erythrosin B can also inhibit ZIKV replication in ZIKV‐relevant human placental and neural progenitor cells. As a pregnancy category B food additive, erythrosin B may represent a promising and easily developed therapy for management of infections by ZIKV and other flaviviruses. HighlightsWe identified erythrosin B as a potent inhibitor for flavivirus protease.Erythrosin B inhibited the DENV2 protease via a non‐competitive mechanism.Erythrosin B interferes the interactions between viral NS3 and its co‐factor NS2B.Erythrosin B is a potent inhibitor for Zika virus and Dengue virus.