Identification, synthesis and pharmacological evaluation of novel anti-EV71 agents via cyclophilin A inhibition

In this work, the relationship between cyclophilin A (CypA) and EV71 prompted us to screen a series of small molecular CypA inhibitors which were previously reported by our group. Among them, compounds 1 and 2 were discovered as non-immunosuppressive anti-EV71 agents with an EC50 values of 1.07 ± 0.17 μM and 3.36 ± 0.45 μM in virus assay, respectively, which were desirably for the further study. The subsequent chemical modifications derived a novel class of molecules, and the structure-activity relationship of these derivatives in the virus assays demonstrated that the 2,6-dihydroxy-benzoylurea moiety and the planar fluorene ring were crucial for the anti-EV71 ability. Furthermore, the results of the modification on the fluorene ring indicated that the substitution at 3′ site of the fluorene ring was better than 1′ site and fluorine was the best substituent. Eventually, among these compounds, 11 demonstrated the most potent anti-EV71 activity in virus assay (EC50 = 0.37 ± 0.17 μM), and low cytotoxicity (CC50 > 25 μM). The following CypA enzyme inhibition studies indicated that there was not only the enzyme inhibition activity, undoubtedly important, functioning in the antiviral process, but also some unknown mechanisms worked in combination, and the further study is underway in our laboratory. Nevertheless, to the best of our knowledge, compound 11 was probably the most potent small molecular anti-EV71 agent via CypA inhibitory mechanism to date. Consequently, our study provided a new potential small molecule for curing EV71 infection.