Discovery of Novel Isoxazole-Based Small-Molecule Toll-Like Receptor 8 Antagonists

Toll-like receptor 8 (TLR8) recognizes viral and bacterial
RNA,
initiating inflammatory responses that are crucial for innate immunity.
Dysregulated TLR8 signaling contributes to autoimmune diseases, including
systemic lupus erythematosus and rheumatoid arthritis, driving chronic
inflammation and tissue damage. Therefore, targeting TLR8 has gained
attention as a promising therapeutic strategy. We report a novel selective
TLR8 antagonist scaffold identified through computational modeling
and simulation. In silico-guided rational drug design and synthesis
led to potent isoxazole-based compounds that were characterized by
structure–activity relationships. The most active compounds
inhibited TLR8-mediated signaling in cell lines and primary cells,
reduced MyD88 recruitment, suppressed NF-κB- and IRF-dependent
signaling, and decreased inflammatory responses. In silico and pharmacological
analyses demonstrated competitive binding to the pocket of chemical
ligands within the TLR8 dimerization interface. These highly selective
and potent TLR8 antagonists possess favorable physicochemical properties,
representing potential clinical candidates for TLR8-targeted therapy.

Toll样受体8（Toll-like receptor 8，TLR8）可识别病毒与细菌RNA，启动对固有免疫至关重要的炎症应答。TLR8信号通路失调可引发包括系统性红斑狼疮、类风湿关节炎在内的自身免疫疾病，推动慢性炎症与组织损伤的发生。因此，靶向TLR8已成为颇具前景的治疗策略，受到广泛关注。本研究报道了一种通过计算建模与模拟筛选得到的新型选择性TLR8拮抗剂骨架。通过计算机模拟指导的理性药物设计与合成，研究人员获得了活性较强的异恶唑（isoxazole）类化合物，并对其构效关系（structure–activity relationship）进行了系统表征。活性最强的化合物可在细胞系与原代细胞中抑制TLR8介导的信号通路，减少髓样分化蛋白88（Myeloid differentiation primary response 88，MyD88）的招募，抑制核因子κB（Nuclear factor kappa-light-chain-enhancer of activated B cells，NF-κB）与干扰素调节因子（Interferon regulatory factor，IRF）依赖的信号通路，并降低炎症应答。计算机模拟与药理学分析表明，这类化合物可竞争性结合TLR8二聚化界面内的化学配体结合口袋。这些兼具高选择性与强效性的TLR8拮抗剂拥有良好的理化性质，有望成为靶向TLR8治疗的潜在临床候选药物。