Toll-like receptor 7 and 8 imidazoquinoline-based agonist/antagonist pairs

Mu Yang, Peter G. Larson, Lincoln Brown, John Schultz, Tamara A Kucaba, Thomas S. Griffith, David M Ferguson

Research output: Contribution to journalArticlepeer-review

4 Scopus citations


Toll-like receptors (TLRs) 7 and 8 are key targets in the development of immunomodulatory drugs for treating infectious disease, cancer, and autoimmune disorders. These receptors can adopt both agonist and antagonist binding conformations that switch the receptor signal on or off to the downstream production of cytokines. In this study, we examined the effect of simple isomeric substitutions to the C2-butyl group of two imidazoquinoline agonists and evaluated the activity of these analogs using both TLR7 and TLR8 reporter cells and cytokine induction assays. Results are presented showing the C2-isobutyl and C2-cyclopropylmethyl isomers are both mixed TLR7/8 competitive antagonists of the parent agonist [4-Amino-1-(4-(aminomethyl)benzyl)-2-butyl-7-methoxycarbonyl-1H-imidazo[4,5-c]quinoline], indicating the conformation of the dimeric receptor complex is highly sensitive to steric perturbations to the ligand binding pocket. This observation is consistent with prior work demonstrating TLR7 and TLR8 activity is directly correlated to C2-alkyl substitutions that project into a hydrophobic pocket at the dimer interface of the receptor. The close structural relationship of the agonist/antagonist pairs identified here highlights the importance of this pocket in tipping the balance between the agonist and antagonist binding states of the receptor which may have significant ramifications to the design of imidazoquinoline-based immunomodulatory agents.

Original languageEnglish (US)
Article number128548
JournalBioorganic and Medicinal Chemistry Letters
StatePublished - Mar 1 2022

Bibliographical note

Funding Information:
This work was supported by a research grant from Seagen, Inc. Bothell, WA to D.M.F. We are also grateful to the Minnesota NMR Center for providing NMR instrumentation and the Minnesota Supercomputing Institute for computational resources.

Publisher Copyright:
© 2022 Elsevier Ltd


  • Antagonist
  • Drug design
  • Imidazoquinoline
  • Immunomodulator
  • Structure activity relationship
  • Synthesis
  • TLR7
  • TLR8
  • Toll-like receptor


Dive into the research topics of 'Toll-like receptor 7 and 8 imidazoquinoline-based agonist/antagonist pairs'. Together they form a unique fingerprint.

Cite this