A Novel Small-Molecule TLR7 Agonist AXC-715 Stabilizes TLR7 Dimerization and Exhibits Broad-Spectrum Antiviral Activity

Toll-like receptor 7 (TLR7) agonism offers a promising avenue for antiviral intervention. This study characterizes AXC-715, a novel small-molecule agonist that selectively targets TLR7 to elicit broad-spectrum antiviral effects. Structural analysis of the AXC-715-hTLR7 complex (PDB ID: 5GMH) elucidates the molecular basis of receptor activation. AXC-715 occupies the interface of TLR7 monomers, establishing critical hydrogen bonds with D555 and T586, alongside π-π and π-alkyl interactions with F408, V381, and L557. These interactions effectively promote and stabilize the active TLR7 dimeric conformation. Functionally, AXC-715 activates NF-κB signaling in a P65-dependent manner without inducing cytotoxicity in PK-15 or THP-1 cells. In vitro assays demonstrated that AXC-715 potently inhibits the replication of both pseudorabies virus (PRV) and vesicular stomatitis virus (VSV) by specifically impairing viral replication, distinct from adsorption, entry, assembly, or release processes. The antiviral effect was abolished in TLR7-knockout PK-15 cells, confirming the strict dependence of AXC-715 on on-target TLR7 signaling. These findings highlight AXC-715 as a potent TLR7 agonist that stabilizes receptor dimerization to inhibit viral replication, providing a valuable framework for developing TLR7-based antiviral therapeutics.