Mechanism of action of the ribopyranoside benzimidazole GW275175X against human cytomegalovirus

Abstract

New human cytomegalovirus (HCMV) therapies with novel mechanisms of action are needed to treat drug-resistant HCMV that arises during therapy with currently approved agents. 2-Bromo-5,6-dichloro-1-beta-D-ribofuranosyl-1H-benzimidazole (BDCRB) is an effective anti-HCMV agent with a novel mechanism of action, but problems with in vivo stability preclude clinical development. A D-ribopyranosyl derivative of BDCRB, GW275175X, displays similar antiviral activity without the in vivo stability problems. We present an initial description of the activity of GW275175X against HCMV, other herpesviruses, and selected nonherpesviruses. In addition, we show that it acts as a DNA maturation inhibitor like the parent compound, BDCRB, rather than via the mechanisms of action of 1263W94 or any anti-HCMV drugs approved for marketing. GW275175X is a promising candidate for clinical development as an anti-HCMV agent.

FIG. 1.

Time-of-addition study with benzimidazole nucleosides and control compounds. At time zero, cells in a 96-well plate were infected with HCMV. Antiviral compounds were added once to separate wells at time zero or at 8-h intervals until 88 h postinfection. Incubation was stopped at 96 h, and virus titers were determined by plaque assay. The time of compound addition is shown on the x axis, and the HCMV titer at 96 h is shown on the y axis.

FIG. 2.

Analysis of HCMV DNA maturation using CHEF electrophoresis. Lambda concatemeric molecular weight markers are shown in the far left lane. The remaining lanes show HCMV DNA from infected cells incubated in the presence of increasing concentrations of BDCRB or GW275175X. The white lines in the lower right corner indicate the location of monomeric viral DNA of ∼230 kb near the bottom of the gel and of a ∼270-kb viral form that appears during treatment with partially inhibitory concentrations of BDCRB.