PD0084430: a non-nucleoside inhibitor of human cytomegalovirus replicationin vitro

Human cytomegalovirus (HCMV) is a major opportunistic pathogen in immunocom promised individuals. Current therapies target viral DNA replication and ac cumulate mutations that yield cross-resistance among the approved drugs. A novel, non-nucleoside inhibitor of HCMV replication, PD0084430, was identif ied in a screening assay using the HCMV beta -galactosidase recombinant RC2 56. The EC50 for PD0084430 by inhibition of beta -galactosidase production is 1 +/- 0.7 muM. This antiviral activity was confirmed by yield reduction and plaque reduction assays using HCMV strain AD169. The TC50 of PD0084430 as measured by C-14-thymidine incorporation is similar to 30 muM and by XTT is similar to 90 muM. The TC50 for inhibition of cellular proliferation is similar to 20 muM. Time of addition experiments displayed a similar drop i n efficacy for both PD0084430 and GCV when added after the onset of viral D NA replication. The transcomplementation assay for viral DNA replication, u sing a transfected ori(Lyt) containing plasmid, confirmed that viral DNA sy nthesis was inhibited at the same concentrations that showed antiviral acti vity. Western blots showed no apparent block of immediate early or early ge ne expression. Two ganciclovir (GCV) resistant isolates of HCMV tested show ed no cross-resistance to PD0084430. These data suggested a potentially pro mising novel compound that inhibited HCMV at or before viral DNA replicatio n. However, in vivo testing in mice dosed either orally or intraperitoneall y showed rapid glucuronidation on the -OH group. SAR studies on this backbo ne showed that the -OH group was essential for the antiviral activity in vi tro. (C) 2001 Elsevier Science B.V. All rights reserved.