The availability of adequate treatments for poxvirus infections would be valuable not only for human use but also for veterinary use. In the search for novel antiviral agents, a 1′-methyl-substituted 4′-thiothymidine nucleoside, designated KAY-2-41, emerged as an efficient inhibitor of poxviruses. In vitro, KAY-2-41 was active in the micromolar range against orthopoxviruses (OPVs) and against the parapoxvirus orf. The compound preserved its antiviral potency against OPVs resistant to the reference molecule cidofovir. KAY-2-41 had no noticeable toxicity on confluent monolayers, but a cytostatic effect was seen on growing cells. Genotyping of vaccinia virus (VACV), cowpox virus, and camelpox virus selected for resistance to KAY-2-41 revealed a nucleotide deletion(s) close to the ATP binding site or a nucleotide substitution close to the substrate binding site in the viral thymidine kinase (TK; J2R) gene. These mutations resulted in low levels of resistance to KAY-2-41 ranging from 2.7- to 6.0-fold and cross-resistance to 5-bromo-2′- deoxyuridine (5-BrdU) but not to cidofovir. The antiviral effect of KAY-2-41 relied, at least in part, on activation (phosphorylation) by the viral TK, as shown through enzymatic assays. The compound protected animals from disease and mortality after a lethal challenge with VACV, reduced viral loads in the serum, and abolished virus replication in tissues. In conclusion, KAY-2-41 is a promising nucleoside analogue for the treatment of poxvirus-induced diseases. Our findings warrant the evaluation of additional 1′-carbon-substituted 4′-thiothymidine derivatives as broad-spectrum antiviral agents, since this molecule also showed antiviral potency against herpes simplex virus 1 in earlier studies. © 2014, American Society for Microbiology.
CITATION STYLE
Duraffour, S., Drillien, R., Haraguchi, K., Balzarini, J., Topalis, D., Van Den Oord, J. J., … Snoeck, R. (2014). Kay-2-41, a novel nucleoside analogue inhibitor of orthopoxviruses in vitro and in vivo. Antimicrobial Agents and Chemotherapy, 58(1), 27–37. https://doi.org/10.1128/AAC.01601-13
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