Structure–activity relationships in Toll-like receptor 7 agonistic 1H-imidazo[4,5-c]pyridines
作者:Euna Yoo、Breanna M. Crall、Rajalakshmi Balakrishna、Subbalakshmi S. Malladi、Lauren M. Fox、Alec R. Hermanson、Sunil A. David
DOI:10.1039/c3ob40816g
日期:——
Engagement of TLR7 in plasmacytoid dendritic cells leads to the induction of IFN-α/β which plays essential functions in the control of adaptive immunity. We had previously examined structureâactivity relationships (SAR) in TLR7/8-agonistic imidazoquinolines with a focus on substituents at the N1, C2, N3 and N4 positions, and we now report SAR on 1H-imidazo[4,5-c]pyridines. 1-Benzyl-2-butyl-1H-imidazo[4,5-c]pyridin-4-amine was found to be a pure TLR7-agonist with negligible activity on TLR8. Increase in potency was observed in N6-substituted analogues, especially in those compounds with electron-rich substituents. Direct arylâaryl connections at C6 abrogated activity, but TLR7 agonism was reinstated in 6-benzyl and 6-phenethyl analogues. Consistent with the pure TLR7-agonistic behavior, prominent IFN-α induction in human PBMCs was observed with minimal proinflammatory cytokine induction. A benzologue of imidazoquinoline was also synthesized which showed substantial improvements in potency over the parent imidazopyridine. Distinct differences in N6-substituted analogues were observed with respect to IFN-α induction in human PBMCs on the one hand, and CD69 upregulation in lymphocytic subsets, on the other.
TLR7在浆细胞样树突细胞中的激活导致IFN-α/β的诱导,这在调控适应性免疫中发挥了关键作用。我们之前已研究了TLR7/8激动剂咪唑喹啉的结构-活性关系(SAR),重点关注N1、C2、N3和N4位置的取代基,现在我们报告1H-咪唑[4,5-c]吡啶的SAR。发现1-苄基-2-丁基-1H-咪唑[4,5-c]吡啶-4-胺为纯TLR7激动剂,且对TLR8的活性微乎其微。在N6取代的类似物中观察到活性增加,特别是在那些具有富电子取代基的化合物中。C6的直接芳基-芳基连接抑制了活性,但在6-苄基和6-苯乙基类似物中恢复了TLR7激动活性。与纯TLR7激动剂行为一致,在人PBMC中观察到显著的IFN-α诱导,同时引起的促炎细胞因子诱导很少。还合成了一种咪唑喹啉的苯类化合物,其在效能上显著优于母体咪唑吡啶。在N6取代的类似物中,关于人PBMC的IFN-α诱导和淋巴细胞亚群中CD69上调的差异明显。