Discovery of host-targeted covalent inhibitors of dengue virus

Abstract

We report here on an approach targeting the host reactive cysteinome to identify inhibitors of host factors required for the infectious cycle of Flaviviruses and other viruses. We used two parallel cellular phenotypic screens to identify a series of covalent inhibitors, exemplified by QL-XII-47, that are active against dengue virus. We show that the compounds effectively block viral protein expression and that this inhibition is associated with repression of downstream processes of the infectious cycle, and thus significantly contributes to the potent antiviral activity of these compounds. We demonstrate that QL-XII-47’s antiviral activity requires selective, covalent modification of a host target by showing that the compound's antiviral activity is recapitulated when cells are preincubated with QL-XII-47 and then washed prior to viral infection and by showing that QL-XII-47R, a non-reactive analog, lacks antiviral activity at concentrations more than 20-fold higher than QL-XII-47's IC90. QL-XII-47’s inhibition of Zika virus, West Nile virus, hepatitis C virus, and poliovirus further suggests that it acts via a target mediating inhibition of these other medically relevant viruses. These results demonstrate the utility of screens targeting the host reactive cysteinome for rapid identification of compounds with potent antiviral activity.

A broad-spectrum antiviral molecule, QL47, selectively inhibits eukaryotic translation

“…We demonstrated that QL47 inhibits not only flaviviruses but also several unrelated, medically relevant viruses, including poliovirus, Ebola virus, and human orthopneumovirus (6,9,10), consistent with a host-rather than virus-targeting mode of action. Subsequent structure-activity relationship (SAR) studies revealed that QL47's antiviral activity is closely associated with inhibition of steady-state viral protein expression (6,9). We demonstrated that TEC-family kinases such as BMX or BTK, the previously characterized targets of QL47 (8), are not responsible for antiviral activity (9).…”

“…We demonstrated that covalent modification of QL47 targets is essential, as replacement of the cysteine-reactive acrylamide moiety with a nonreactive propyl amide yields an inactive compound, QL47R ( Fig. 1A) (6,9). We also identified acrylamide-containing derivatives, such as YKL-04-085 ( Fig.…”

“…This effort led to the discovery of multiple antiviral compounds (6), including QL47, a cysteine-reactive small molecule that inhibits the proliferation of Bruton's tyrosine kinase (BTK)-dependent cancer cell lines (8). We demonstrated that QL47 inhibits not only flaviviruses but also several unrelated, medically relevant viruses, including poliovirus, Ebola virus, and human orthopneumovirus (6,9,10), consistent with a host-rather than virus-targeting mode of action. Subsequent structure-activity relationship (SAR) studies revealed that QL47's antiviral activity is closely associated with inhibition of steady-state viral protein expression (6,9).…”

“…We previously reported an approach to target the cellular reactive cysteinome (6) to identify inhibitors of host factors required for the infectious cycle of dengue virus (DV), 4 a mosquito-borne flavivirus that is a significant pathogen in tropical regions (7). This effort led to the discovery of multiple antiviral compounds (6), including QL47, a cysteine-reactive small molecule that inhibits the proliferation of Bruton's tyrosine kinase (BTK)-dependent cancer cell lines (8).…”

“…We previously reported an approach to target the cellular reactive cysteinome (6) to identify inhibitors of host factors required for the infectious cycle of dengue virus (DV), 4 a mosquito-borne flavivirus that is a significant pathogen in tropical regions (7). This effort led to the discovery of multiple antiviral compounds (6), including QL47, a cysteine-reactive small molecule that inhibits the proliferation of Bruton's tyrosine kinase (BTK)-dependent cancer cell lines (8). We demonstrated that QL47 inhibits not only flaviviruses but also several unrelated, medically relevant viruses, including poliovirus, Ebola virus, and human orthopneumovirus (6,9,10), consistent with a host-rather than virus-targeting mode of action.…”