tetano
Editor, Senior Moderator
Proc Natl Acad Sci U S A
. 2025 Aug 19;122(33):e2503899122.
doi: 10.1073/pnas.2503899122. Epub 2025 Aug 13. Mechanistic insights into the small-molecule inhibition of influenza A virus entry
Yan Xu[SUP] #[/SUP][SUP] 1 [/SUP], Varada Anirudhan[SUP] #[/SUP][SUP] 2 [/SUP], Irina N Gaisina[SUP] 3 4 [/SUP], Haijuan Du[SUP] 5 [/SUP], Saad Alqarni[SUP] 6 [/SUP], Terry W Moore[SUP] 3 7 [/SUP], Michael Caffrey[SUP] 8 [/SUP], Balaji Manicassamy[SUP] 9 [/SUP], Tongqing Zhou[SUP] 5 [/SUP], Lijun Rong[SUP] 2 4 [/SUP], Kai Xu[SUP] 1 10 [/SUP]
Affiliations
Influenza A virus (IAV) is a zoonotic pathogen responsible for seasonal and pandemic flu. The extensive genetic and antigenic diversity within and between IAV phylogenetic groups presents major challenges for developing universal vaccines and broad-spectrum antiviral therapies. Current interventions provide limited protection due to the virus's high mutation rate and capacity for immune evasion. Recent advancements in viral hemagglutinin (HA)-targeting small-molecule entry inhibitors offer a promising avenue to overcome these limitations. Here, we present structural and functional analyses of two group 2 HA-specific small-molecule inhibitors recently identified by our team. Cryogenic electron microscopy (cryo-EM) structures revealed that these inhibitors bind a conserved pocket within the HA stalk, likely interfering with the conformational rearrangements necessary for membrane fusion and viral entry. Structure-guided mutagenesis confirmed the critical roles of key interacting residues and uncovered distinct resistance profiles between the two compounds, as well as in comparison to Arbidol, a previously reported HA inhibitor. Notably, our structural analysis highlights intrinsic barriers to achieving cross-group inhibition with current small-molecule designs. To address this, we propose an alternative strategy for broadening antiviral coverage. Together, these findings provide mechanistic insights into IAV entry inhibition and a foundation for the rational design of next-generation anti-influenza therapeutics.
Keywords: Influenza A virus; antiviral; cryo-electron microscopy; hemagglutinin; small molecule inhibitors.
. 2025 Aug 19;122(33):e2503899122.
doi: 10.1073/pnas.2503899122. Epub 2025 Aug 13. Mechanistic insights into the small-molecule inhibition of influenza A virus entry
Yan Xu[SUP] #[/SUP][SUP] 1 [/SUP], Varada Anirudhan[SUP] #[/SUP][SUP] 2 [/SUP], Irina N Gaisina[SUP] 3 4 [/SUP], Haijuan Du[SUP] 5 [/SUP], Saad Alqarni[SUP] 6 [/SUP], Terry W Moore[SUP] 3 7 [/SUP], Michael Caffrey[SUP] 8 [/SUP], Balaji Manicassamy[SUP] 9 [/SUP], Tongqing Zhou[SUP] 5 [/SUP], Lijun Rong[SUP] 2 4 [/SUP], Kai Xu[SUP] 1 10 [/SUP]
Affiliations
- PMID: 40802690
- DOI: 10.1073/pnas.2503899122
Influenza A virus (IAV) is a zoonotic pathogen responsible for seasonal and pandemic flu. The extensive genetic and antigenic diversity within and between IAV phylogenetic groups presents major challenges for developing universal vaccines and broad-spectrum antiviral therapies. Current interventions provide limited protection due to the virus's high mutation rate and capacity for immune evasion. Recent advancements in viral hemagglutinin (HA)-targeting small-molecule entry inhibitors offer a promising avenue to overcome these limitations. Here, we present structural and functional analyses of two group 2 HA-specific small-molecule inhibitors recently identified by our team. Cryogenic electron microscopy (cryo-EM) structures revealed that these inhibitors bind a conserved pocket within the HA stalk, likely interfering with the conformational rearrangements necessary for membrane fusion and viral entry. Structure-guided mutagenesis confirmed the critical roles of key interacting residues and uncovered distinct resistance profiles between the two compounds, as well as in comparison to Arbidol, a previously reported HA inhibitor. Notably, our structural analysis highlights intrinsic barriers to achieving cross-group inhibition with current small-molecule designs. To address this, we propose an alternative strategy for broadening antiviral coverage. Together, these findings provide mechanistic insights into IAV entry inhibition and a foundation for the rational design of next-generation anti-influenza therapeutics.
Keywords: Influenza A virus; antiviral; cryo-electron microscopy; hemagglutinin; small molecule inhibitors.