Rationally derived inhibitors of hepatitis C virus (HCV) p7 channel activity reveal prospect for bimodal antiviral therapy

Abstract

Since the 1960s, a single class of agent has been licensed targeting virus-encoded ion channels, or ‘viroporins’, contrasting the success of channel blocking drugs in other areas of medicine. Although resistance arose to these prototypic adamantane inhibitors of the influenza A virus (IAV) M2 proton channel, a growing number of clinically and economically important viruses are now recognised to encode essential viroporins providing potential targets for modern drug discovery. We describe the first rationally designed viroporin inhibitor with a comprehensive structure-activity relationship (SAR). This step-change in understanding not only revealed a second biological function for the p7 viroporin from hepatitis C virus (HCV) during virus entry, but also enabled the synthesis of a labelled tool compound that retained biological activity. Hence, p7 inhibitors (p7i) represent a unique class of HCV antiviral targeting both the spread and establishment of infection, as well as a precedent for future viroporin-targeted drug discovery.

Inhibitors of the Small Membrane (M) Protein Viroporin Prevent Zika Virus Infection

“…Finally, we tested whether M channel activity was sensitive to inhibitory small molecules, indicative of the formation of structurally ordered complexes. Moreover, prototypic channel blockers can identify druggable sites within viroporin complexes, amenable to the further identification of improved small molecules( 46, 48, 49 ). Rimantadine (1 μM) caused a significant reduction in M channel activity (Figure 1g), consistent with the presence of a viable binding site within a soluble, folded M channel complex.…”

“…This work supports that the mature M protein residing within the mature ZIKV virion acts as an ion channel with a critical function during virus entry. This is reminiscent of the IAV M2 protein, which responds to endosomal pH to allow protonation of the virion core, expediting virion uncoating( 56 ); we have recently demonstrated that HCV p7 plays a similar role( 49 ). Moreover, like M2, the activity of M is sensitive to both prototypic small molecules and rationally designed ligands, preventing infection both in cell culture and in vivo .…”

“…Importantly, rimantadine sensitivity supports that dye release was mediated by interactions with a folded protein complex rather than via aggregates disrupting membrane integrity, and increased activity at acidic pH is consistent with activation within acidifying endosomes during virus entry. Other pH-gated channels including IAV M2, HCV p7 (genotype and polymorphism-dependent) and HPV E5, are similarly activated within the same assay system( 44, 48, 49, 52 ).…”

Inhibitor Development against p7 Channel in Hepatitis C Virus

“…MD simulation-based studies also showed that the aromatic rings are important to improve the binding affinities to p7 channel, which provides a direction to further optimize the compounds in the further drug design. Interestingly, a recently published paper from Shaw et al also reported a stronger inhibitor-JK3/32, which contained aromatic groups and exerted irreversible blockade on p7 channel [ 36 ].…”

“…Several dimeric compounds showed better potency than that of amantadine in some genotypes [ 33 , 34 , 35 ]. A recent rational designed compound with an oxindole scaffold displayed strong anti-HCV activity [ 36 ]. These studies achieved some improvements on the inhibition of p7; however, the inhibitory effects on the p7 channel are still at relatively low drug efficacies.…”