The increasing prevalence of influenza viruses with resistance to approved
antivirals highlights the need for new anti-
influenza therapeutics. Here we describe the functional properties of
hexamethylene amiloride (HMA)-derived compounds that inhibit the wild-type and
adamantane-resistant forms of the
influenza A M2
ion channel. For example, 6-(azepan-1-yl)-N-carbamimidoylnicotinamide ( 9: ) inhibits
amantadine-sensitive M2 currents with 3- to 6-fold greater potency than
amantadine or HMA (IC50 = 0.2 vs. 0.6 and 1.3 µM, respectively). Compound 9: competes with
amantadine for M2 inhibition, and molecular docking simulations suggest that 9: binds at site(s) that overlap with
amantadine binding. In addition, tert-butyl 4'-(carbamimidoylcarbamoyl)-2',3-dinitro-[1,1'-
biphenyl]-4-carboxylate ( 27: ) acts both on
adamantane-sensitive and a resistant M2 variant encoding a
serine to
asparagine 31 mutation (S31N) with improved efficacy over
amantadine and HMA (IC50 = 0.6 µM and 4.4 µM, respectively). Whereas 9: inhibited in vitro replication of influenza virus encoding wild-type M2 (EC50 = 2.3 µM), both 27: and tert-butyl 4'-(carbamimidoylcarbamoyl)-2',3-dinitro-[1,1'-
biphenyl]-4-carboxylate ( 26: ) preferentially inhibited viruses encoding M2(S31N) (respective EC50 = 18.0 and 1.5 µM). This finding indicates that HMA derivatives can be designed to inhibit viruses with resistance to
amantadine. Our study highlights the potential of HMA derivatives as inhibitors of
drug-resistant
influenza M2
ion channels.