title: High frequency of spontaneous helicase-primase inhibitor (BAY 57-1293) drug-resistant variants in certain laboratory isolates of HSV-1.
abstract: Herpes simplex virus (HSV) helicase-primase is the target for a new group of potent antivirals that show great promise in vivo. A claimed advantage of this class of compounds is the low rate of drug resistance, which is reported to occur at a lesser rate than acyclovir (ACV)-resistance in cell culture. We confirmed that BAY 57-1293 is highly active against HSV-1 and superior to ACV when tested in Vero cells. Notably, drug resistance was detected in laboratory working stocks in two different strains of HSV at 10(-4) to 10(-5) and there was evidence that the resistant variants were present in the virus population before the selection was applied. Plaque-purified clones obtained from the parental viruses showed a lower level of resistance selection in the presence of drug (10-6) and this value is similar to published reports. In the case of HSV-1 SC16, no difference was observed between a working stock and a plaque-pure clone in the rate of resistance to the nucleoside analogue ACV. The working stocks were found to contain variants with resistance to BAY 57-1293 ranging from approximately 15-fold to 4,000-fold suggesting that these viruses have the potential to subvert effective therapy. Sequence analysis of HSV-1 helicase protein showed that most of the amino acid substitutions in the variants described in this study tallied with published results, with some interesting exceptions in the case of HSV-1 strain PDK. Resistant variants did not readily revert to a sensitive phenotype in the absence of the inhibitor and representative BAY 57-1293-resistant variants were cross-resistant to an alternative helicase-primase inhibitor, BILS 22 BS. Variants resistant to BAY 57-1293 retained sensitivity to the nucleoside analogue, ACV.
authors.affiliation: Centre for Veterinary Science, Cambridge University Veterinary School, Cambridge, UK.
authors.forename: Subhajit
authors.initials: S
authors.lastname: Biswas
authors.forename: Mihaiela
authors.initials: M
authors.lastname: Swift
authors.forename: Hugh J
authors.initials: HJ
authors.lastname: Field
mesh_terms: D000818:Animals; D000998:Antiviral Agents / Q000494:pharmacology*; D002522:Chlorocebus aethiops; D004265:DNA Helicases / Q000037:antagonists & inhibitors*; D019915:DNA Primase / Q000037:antagonists & inhibitors*; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D018259:Herpesvirus 1, Human / Q000187:drug effects*; D011725:Pyridines / Q000494:pharmacology*; D013449:Sulfonamides; D013844:Thiazoles / Q000494:pharmacology*; D014709:Vero Cells
chemical_list: D000998:Antiviral Agents; D004791:Enzyme Inhibitors; D011725:Pyridines; D013449:Sulfonamides; D013844:Thiazoles; C453221:pritelivir; D019915:DNA Primase; D004265:DNA Helicases