Zika virus (ZIKV) infection is associated with the birth defect microcephaly and Guillain–Barré syndrome in adults. There is no approved vaccine or specific antiviral agent against ZIKV. ZFD-10, a novel structural skeleton of 1H-pyridazino[4,5-b]indol-4(5H)-one, was firstly synthesized and discovered to be a potent anti-ZIKV inhibitor with very low cytotoxicity. ZFD-10's anti-ZIKV potency is independent of cell lines and ZFD-10 mainly targets the post-entry stages of ZIKV life cycle. Time-of-addition and time-of-withdrawal assays showed that 10 μM ZFD-10 displayed the ability to decrease mainly at the RNA level and weakly the viral progeny particle load. Furthermore, ZFD-10 could protect ZIKV NS5 from thermal unfolding and aggregation and increase the Tagg value of ZIKV NS5 protein from 44.6 to 49.3 °C, while ZFD-10 dose-dependently inhibits ZIKV NS5 RdRp activity using in vitro RNA polymerase assays. Molecular docking study suggests that ZFD-10 affects RdRp enzymatic function through interfering with the fingers and thumb subdomains. These results supported that ZFD-10's cell-based anti-ZIKV activity is related to its anti-RdRp activity of ZIKV NS5. The in vivo anti-ZIKV study shows that the middle-dose (4.77 mg/kg/d) of ZFD-10 protected mice from ZIKV infection and the viral loads of the blood, liver, kidney and brain in the middle-dose and high-dose (9.54 mg/kg/d) were significantly reduced compared to those of the ZIKV control. These results confirm that ZFD-10 has a certain antiviral effect against ZIKV infection in vivo.

寨卡病毒 （ZIKV） 感染与成人出生缺陷小头症和格林-巴利综合征有关。目前尚无批准的针对 ZIKV 的疫苗或特异性抗病毒药物。ZFD-10 是 1H-吡哒傔基[4,5-b]吲哚-4（5H）-酮的新型结构骨架，首次合成并发现是一种有效的抗 ZIKV 抑制剂，具有极低的细胞毒性。ZFD-10 的抗 ZIKV 效力独立于细胞系，ZFD-10 主要针对 ZIKV 生命周期的进入后阶段。添加时间和撤出时间测定表明，10 μM ZFD-10 主要在 RNA 水平上表现出降低的能力，而病毒后代颗粒载量较弱。此外，ZFD-10 可以保护 ZIKV NS5 免受热去折叠和聚集，并将 ZIKV NS5 蛋白的 Tagg 值从 44.6 °C 增加到 49.3 °C，而 ZFD-10 使用体外 RNA 聚合酶测定剂量依赖性地抑制 ZIKV NS5 RdRp 活性。分子对接研究表明，ZFD-10 通过干扰手指和拇指亚结构域影响 RdRp 酶功能。这些结果支持 ZFD-10 基于细胞的抗 ZIKV 活性与其对 ZIKV NS5 的抗 RdRp 活性有关。体内抗 ZIKV 研究表明，中剂量 （4.77 mg/kg/d） 的 ZFD-10 保护小鼠免受 ZIKV 感染，中剂量和高剂量 （9.54 mg/kg/d） 的血液、肝脏、肾脏和大脑的病毒载量与 ZIKV 对照相比显着降低。这些结果证实了 ZFD-10 在体内对 ZIKV 感染具有一定的抗病毒作用。