Exquisite selectivity for human toll-like receptor 8 in substituted furo[2,3-c]quinolines

Hari Prasad Kokatla, Diptesh Sil, Subbalakshmi S. Malladi, Rajalakshmi Balakrishna, Alec R. Hermanson, Lauren M. Fox, Xinkun Wang, Anshuman Dixit, Sunil A. David

Research output: Contribution to journalArticlepeer-review

48 Scopus citations


Toll-like receptor (TLR)-8 agonists activate adaptive immune responses by inducing robust production of T helper 1-polarizing cytokines, suggesting that TLR8-active compounds may be promising candidate adjuvants. We synthesized and evaluated hitherto unexplored furo[2,3-c]quinolines and regioisomeric furo[3,2-c]quinolines derived via a tandem, one-pot Sonogashira coupling and intramolecular 5-endo-dig cyclization strategy in a panel of primary screens. We observed a pure TLR8-agonistic activity profile in select furo[2,3-c] quinolines, with maximal potency conferred by a C2-butyl group (EC50 = 1.6 μM); shorter, longer, or substituted homologues as well as compounds bearing C1 substitutions were inactive, which was rationalized by docking studies using the recently described crystal structure of human TLR8. The best-in-class compound displayed prominent proinflammatory cytokine induction (including interleukin-12 and interleukin-18), but was bereft of interferon-α inducing properties, confirming its high selectivity for human TLR8.

Original languageEnglish (US)
Pages (from-to)6871-6885
Number of pages15
JournalJournal of medicinal chemistry
Issue number17
StatePublished - Sep 12 2013


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