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Background: Herpes simplex virus 1 (HSV-1) affects a large part of the adult population. Anti-HSV-1 drugs, such as acyclovir, target thymidine kinase and viral DNA polymerase. However, the emerging of resistance of HSV-1 alerts for the urgency in developing new antivirals with other therapeutic targets. Thus, this study evaluated a series of 1,4-disubstituted-1,2,3-triazole derivatives against HSV-1 acute infection and provided deeper insights into the possible mechanisms of action. Methods: Human fibroblast cells (HFL-1) were infected with HSV-1 17syn+ and treated with the triazole compounds at 50 mM for 24 h. The 50% effective drug concentration (EC 50 ) was determined for the active compounds. Their cytotoxicity was also evaluated in HFL-1 with the 50% cytotoxic concentration (CC 50 ) determined using CellTiter-Glo ® solution. The most promising compounds were evaluated by virucidal activity and influence on virus egress, DNA replication and transcription, and effect on an acyclovir-resistant HSV-1 strain. Results: Compounds 3 ((E)-4-methyl-N'-(2-(4-(phenoxymethyl)-1H-1,2,3-triazol1yl)benzylidene)benzenesulfonohydrazide) and 4 (2,2'-(4,4'-((1,3-phenylen ebis(oxy))bis(methylene))bis(1H-1,2,3-triazole-4,1 diyl))dibenzaldehyde) were the most promising, with an EC 50 of 16 and 21 mM and CC 50 of 285 and 2,593 mM, respectively. Compound 3 was able to inhibit acyclovir-resistant strain replication and to interfere with virus egress. Both compounds did not affect viral DNA replication, but inhibited significantly the expression of ICP0, ICP4 and gC. Compound 4 also affected the transcription of UL30 and ICP34.5. Conclusions: Our findings demonstrated that these compounds are promising antiviral candidates with different mechanisms of action from acyclovir and further studies are merited.

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