An M2-V27A channel blocker demonstrates potent in vitro and in vivo antiviral activities against amantadine-sensitive and -resistant influenza A viruses

Abstract

Adamantanes such as amantadine (1) and rimantadine (2) are FDA-approved anti-influenza drugs that act by inhibiting the wild-type M2 proton channel from influenza A viruses, thereby inhibiting the uncoating of the virus. Although adamantanes have been successfully used for more than four decades, their efficacy was curtailed by emerging drug resistance. Among the limited number of M2 mutants that confer amantadine resistance, the M2-V27A mutant was found to be the predominant mutant under drug selection pressure, thereby representing a high profile antiviral drug target. Guided by molecular dynamics simulations, we previously designed first-in-class M2-V27A inhibitors. One of the potent lead compounds, spiroadamantane amine (3), inhibits both the M2-WT and M2-V27A mutant with IC50 values of 18.7 and 0.3 μM, respectively, in in vitro electrophysiological assays. Encouraged by these findings, in this study we further examine the in vitro and in vivo antiviral activity of compound 3 in inhibiting both amantadine-sensitive and -resistant influenza A viruses. Compound 3 not only had single to submicromolar EC50 values against M2-WT- and M2-V27A-containing influenza A viruses in antiviral assays, but also rescued mice from lethal viral infection by either M2-WT- or M2-V27A-containing influenza A viruses. In addition, we report the design of two analogs of compound 3, and one was found to have improved in vitro antiviral activity over compound 3. Collectively, this study represents the first report demonstrating the in vivo antiviral efficacy of inhibitors targeting M2 mutants. The results suggest that inhibitors targeting drug-resistant M2 mutants are promising antiviral drug candidates worthy of further development.

Slow but Steady Wins the Race: Dissimilarities among New Dual Inhibitors of the Wild-Type and the V27A Mutant M2 Channels of Influenza A Virus

“…31–36 Taking into account the poor inhibitory activity displayed by the first series (see discussion of inhibitory activity of 3 and 13 below), a second group of piperidine derivatives was envisaged from 2-adamantanone, 9 . The second series featured an increased length thanks to the introduction of an additional carbon atom between the piperidine and the adamantyl group.…”

Put a cork in it: Plugging the M2 viral ion channel to sink influenza

“…Furthermore, injection of mice with the dual-inhibitor compound 9 at up to 100 mg/kg/day resulted in no changes in body weight. Importantly, at up to 100 mg/kg/day, compound 9 also rescued mice from lethal infection of viruses containing either WT M2 or M2 Val27Ala, thereby demonstrating in vivo efficacy (Hu et al, 2017a). While initial results are encouraging, in vivo results for most adamantane derivatives remain limited and await further study.…”

“…The preclinical and in vivo potential of M2 Ser31Asn-inhibiting adamantane derivatives are now beginning to be elucidated. For example, Compounds 5, 8, 10, and 16 have been reported to inhibited virus strains with resistance to the licensed neuramindase inhibitor oseltamivir (Hu et al, 2017a;Ma et al, 2016;Wang et al, 2018). In oseltamivir-sensitive viruses, 5 and 16 also synergized with oseltamivir, raising the possibility of combination therapies where lower doses of drugs can be used to minimize the risk of toxicities without sacrificing antiviral efficacy (Ma et al, 2016;Wang et al, 2018).…”

Discovery of dapivirine, a nonnucleoside HIV-1 reverse transcriptase inhibitor, as a broad-spectrum antiviral against both influenza A and B viruses

“…1A) was identified as a potent antiviral against the A/California/07/2009 (H1N1) virus in the plaque assay (Hu et al, 2017). In the plaque assay, MDCK cells were infected with A/California/07/2009 (H1N1) at 100 PFU/well in the presence of increasing concentrations of dapivirine.…”

“…The titers of harvested viruses were determined by plaque assay. The dapivirine sensitivity after passages 3, 6, 9, and 12 was determined via plaque assay as described previously (Hu et al, 2017). The second set of serial passage experiment was performed with the A/Switzerland/9715293/2013 (H3N2) virus.…”