Design, synthesis, and biological evaluation of novel 2′-methyl-2′-fluoro-6-methyl-7-alkynyl-7-deazapurine nucleoside analogs as anti-Zika virus agents

Zika virus (ZIKV) is a mosquito-borne flavivirus and outbreaks of ZIKV have been reported in Africa, Americas and other parts of the world lately. The ZIKV epidemic has received extensive attention due to its ability to cause serious medical consequences and complications such as microcephaly and Guillain-Barre syndrome in recent years. Up to now, there are no specific treatments or vaccines available for ZIKV infection, which highlights the urgent need for developing new therapies. In this work, we designed and synthesized a series of novel 6-methyl-7-acetylenenyl-7-deazapurine nucleoside analogs as potential inhibitors of ZIKV replication. The biological activities against ZIKV replication were evaluated and the structure-activity relationship (SAR) was also studied. Among the compounds evaluated, nucleoside analog 38 (EC50 = 2.8 ± 0.8 μM, EC90 = 6.8 ± 2.3 μM) showed the most potent anti-ZIKV activity with low cytotoxicity (CC50 = 54.1 ± 6.9 μM) in an A549 based cellular model. The inhibitory activity of 38 was about 5 times more potent than the positive control NITD008. Notably, 38 showed similar inhibition potency against different ZIKV strains (ZG-01 and MR766) in a variety of host cell types including SNB19, A549, Huh7, Vero. In addition, 38 (Kd = 1.87 μM) has a stronger affinity to ZIKV RNA-dependent RNA polymerase (RdRp) protein than NITD008 (Kd = 3.43 μM) in the non-phosphorylation assay. These results indicated that compound 38 may serve as a promising candidate in future anti-ZIKV drug discovery.