Discovery of Novel Dual Inhibitors of the Wild-Type and the Most Prevalent Drug-Resistant Mutant, S31N, of the M2 Proton Channel from Influenza A Virus

Abstract

Anti-influenza drugs, amantadine and rimantadine, targeting the M2 channel from influenza A virus are no longer effective because of widespread drug resistance. S31N is the predominant and amantadine-resistant M2 mutant, present in almost all of the circulating influenza A strains as well as in the pandemic 2009 H1N1 and the highly pathogenic H5N1 flu strains. Thus, there is an urgent need to develop second-generation M2 inhibitors targeting the S31N mutant. However, the S31N mutant presents a huge challenge to drug discovery, and it has been considered undruggable for several decades. Using structural information, classical medicinal chemistry approaches, and M2-specific biological testing, we discovered benzyl-substituted amantadine derivatives with activity against both S31N and WT, among which 4-(adamantan-1-ylaminomethyl)-benzene-1,3-diol (44) is the most potent dual inhibitor. These inhibitors demonstrate that S31N is a druggable target and provide a new starting point to design novel M2 inhibitors that address the problem of drug-resistant influenza A infections.

Viroporins: structure, function and potential as antiviral targets

“…However, recent functional and structural studies lend further support to lumenal adamantane binding, including those on chimeric influenza A/influenza B M2, where the lumenal domain originates from the drug-sensitive IAV M2 and the peripheral domain from the resistant BM2 Pielak et al, 2011). Adamantanes bound to the lumen in all cases where inhibition occurred and lumenal binding has also been documented for novel adamantane derivatives shown to inhibit amantadine-resistant Ser31Asn mutant M2 channels (Wang et al, 2013a, c;Williams et al, 2013;Wu et al, 2014).…”

“…The majority of novel inhibitors identified to date involve either derivatization of amantadine or another M2-inhibitory compound, BL-1743, which was identified from a yeast-based M2 screen (Duque et al, 2011;Kurtz et al, 1995;Rey-Carrizo et al, 2013, 2014Tu et al, 1996;Wang et al, 2009Wang et al, , 2011aWang et al, , b, 2013aWu et al, 2014). Effective inhibitors of several drug-resistant variants have been identified by this approach, although far fewer hits capable of blocking Asn31 channels have arisen.…”

Detection of Proton Movement Directly across Viral Membranes To Identify Novel Influenza Virus M2 Inhibitors

“…Using medicinal chemistry and computational predictions (although not highthroughput screening), 10 nonadamantane scaffolds active against influenza virus M2 have been reported in recent years, none of which inhibit the ubiquitous S31N amantadine-resistant mutant (29)(30)(31)(32)(33)(34). Recently, however, amantadine-based compounds have been further derivatized to create variants that can inhibit wild-type and S31N resistant strains (35,36). Our ion channel VLP technology complements these efforts, and our results suggest that future screening efforts using a resistant strain for primary screening should identify novel, non-adamantanebased compounds capable of inhibiting adamantane-resistant viruses.…”

On the role of water density fluctuations in the inhibition of a proton channel

“…In addition, positively charged fragment-like molecules, such as amantadine (44) and 2-guanidinobenzimidazole (2GBI) (30), are known to act as pore blockers of M2 and Hv1, respectively. Many groups, including ours, have successfully pursued drug discovery projects with M2 as a target (45)(46)(47)(48)(49)(50)(51)(52)(53). In particular, we have recently shown that scaffold replacement of hydrogen-bonded Significance Hv1, a voltage-gated proton channel, is an emerging pharmacological target implicated in many pathological conditions, including cancer and ischemic brain damage.…”