Targeting Chikungunya Virus Replication by Benzoannulene Inhibitors

A benzo[6]­annulene, 4-(tert-butyl)-N-(3-methoxy-5,6,7,8-tetrahydronaphthalen-2-yl) benzamide (1a), was identified as an inhibitor against Chikungunya virus (CHIKV) with antiviral activity EC90 = 1.45 μM and viral titer reduction (VTR) of 2.5 log at 10 μM with no observed cytotoxicity (CC50 = 169 μM) in normal human dermal fibroblast cells. Chemistry efforts to improve potency, efficacy, and drug-like properties of 1a resulted in a novel lead compound 8q, which possessed excellent cellular antiviral activity (EC90 = 270 nM and VTR of 4.5 log at 10 μM) and improved liver microsomal stability. CHIKV resistance to an analog of 1a, compound 1c, tracked to a mutation in the nsP3 macrodomain. Further mechanism of action studies showed compounds working through inhibition of human dihydroorotate dehydrogenase in addition to CHIKV nsP3 macrodomain. Moderate efficacy was observed in an in vivo CHIKV challenge mouse model for compound 8q as viral replication was rescued from the pyrimidine salvage pathway.本研究鉴定出一种苯并[6]轮烯类化合物：4-(叔丁基)-N-(3-甲氧基-5,6,7,8-四氢萘-2-基)苯甲酰胺（1a），其可作为基孔肯雅病毒（Chikungunya virus, CHIKV）抑制剂。在正常人真皮成纤维细胞中，该化合物的抗病毒活性90%有效浓度（90% effective concentration, EC90）为1.45 μM，于10 μM浓度下病毒滴度降低（viral titer reduction, VTR）达2.5 log₁₀，且未观测到细胞毒性，其半数细胞毒性浓度（50% cytotoxic concentration, CC50）为169 μM。为优化化合物1a的活性效价、抗病毒效力与成药性，研究团队通过化学修饰手段获得了新型先导化合物8q。该化合物展现出优异的细胞内抗病毒活性：10 μM浓度下EC90为270 nM，VTR达4.5 log₁₀，同时肝微粒体稳定性得到显著提升。基孔肯雅病毒对化合物1a的类似物1c产生的耐药性，其耐药机制与nsP3宏结构域（nsP3 macrodomain）的突变相关。进一步的作用机制研究表明，此类化合物可通过双重靶点发挥抗病毒作用：同时抑制人类二氢乳清酸脱氢酶（human dihydroorotate dehydrogenase）与基孔肯雅病毒nsP3宏结构域。在体内基孔肯雅病毒攻击小鼠模型中，化合物8q仅展现出中等抗病毒疗效，究其原因，病毒复制可通过嘧啶补救途径得到挽救。