Q63, a novel DENV2 RdRp non-nucleoside inhibitor, inhibited DENV2 replication and infection

Dengue virus (DENV) annually infects 400 million people worldwide. Unfortunately, there is lack of widely protective vaccine or drugs against DENV. The viral RNA-dependent RNA polymerase (RdRp) of NS5 protein is highly conserved among different DENV subtypes, thus presenting itself as an attractive target for drug design. In the current research, SPRi was performed to screen compounds against DENV2 RdRp and 5(1H)-Quinazolinone,2-(4-bromophenyl)-2,3,4,6,7,8-hexahydro-7,7-dimethyl-1,3-diphenyl (Q63) was successfully screened out with a KD of 0.9 μM. Then, ITC and molecular docking assay was performed to access the binding mechanism between Q63 and DENV2 RdRp. Meanwhile, Q63 also decreased the intermediate dsRNA production, which was the product of RdRp. Further the antiviral effects of Q63 were evaluated on mosquito C6/36 cells and mammalian BHK-21 cells. Q63 reduced CPE and cell toxicity effect after DENV2 infection on C6/36 and BHK-21 cells, with an EC₅₀ of 2.08 μM. Time of addition assay revealed that Q63 affected the early genome RNA replication stage, including genome RNA replication. In addition, Q63 down-regulated STAT1 phosphorylation, ISG15 and ISG54 after DENV2 infection. In summary, Q63 was found to be a novel RdRp non-nucleoside inhibitor and a potential lead compound for coping with DENV infectious disease in the future.