One challenge facing anti-influenza drug development is the heterogeneity of the circulating influenza A viruses, which comprise several strains with variable susceptibility to antiviral drugs. Viruses bearing the S31N mutant of the M2, such as the pandemic 2009 H1N1 and seasonal H3N2, as well as other mutants (L26F, V27A, A30T, G34E) are resistant to amantadine class of drugs. Here, we synthesized and tested many of the second generation amantadine - aryl conjugates, against the WT M2 and all the M2 amantadine resistant strains, i.e. L26F, V27A, S31N, A30T, G34E generated from WSN/33 (S31N) virus. We identified many compounds that are dual in vitro M2 WT and L26F virus inhibitors. Furthermore, few of them (21, 32, 33), having a rimantadine or diamantadine or 4-(1-adamantyl)aniline instead of amantadine in the conjugate, were in vitro inhibitors against M2 WT, L26F and S31N while one of them inhibited also the A30T virus. The electrophysiology (EP) experiments showed that these compounds blocked significantly M2 WT, L26F or even M2 V27A channels but not the M2 S31N. The observation that adamantane variants and derivatives inhibit multiple M2 mutant virus replication in cell culture, without blocking M2 channel-mediated proton current in EP is not uncommon, underlying a mechanism of antiviral activity that has not been identified.
In Vitro Pharmacokinetic Optimizations of AM2-S31N Channel Blockers Led to the Discovery of Slow-Binding Inhibitors with Potent Antiviral Activity against Drug-Resistant Influenza A Viruses
