Novel and Selective TLR7 Antagonists among the Imidazo[1,2- a]pyrazines, Imidazo[1,5- a]quinoxalines, and Pyrazolo[1,5- a]quinoxalines Series

J Med Chem. 2019 Aug 8;62(15):7015-7031. doi: 10.1021/acs.jmedchem.9b00411. Epub 2019 Jul 19.

Abstract

The Toll-like receptors (TLRs) 7 and 8 play an important role in the immune system activation, and their agonists may therefore serve as promising candidate vaccine adjuvants. However, the chronic immune activation by excessive TLR stimulation is a hallmark of several clinically important infectious and autoimmune diseases, which warrants the search for TLR antagonists. In this study, we have synthesized and characterized a variety of compounds belonging to three heterocyclic chemical series: imidazo[1,2-a]pyrazine, imidazo[1,5-a]quinoxaline, and pyrazolo[1,5-a]quinoxaline. These compounds have been tested for their TLR7 or TLR8 agonistic and antagonistic activities. Several of them are shown to be selective TLR7 antagonists without any TLR7 or TLR8 agonistic activity. The selectivity was confirmed by a comparative ligand-docking study in TLR7 antagonist pocket. Two compounds of the pyrazolo[1,5-a]quinoxaline series (10a and 10b) are potent selective TLR7 antagonists and may be considered as promising starting points for the development of new therapeutic agents.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cell Line
  • Dose-Response Relationship, Drug
  • Humans
  • Imidazoles / chemistry*
  • Imidazoles / pharmacology
  • Protein Structure, Secondary
  • Pyrazines / chemistry*
  • Pyrazines / pharmacology
  • Quinoxalines / chemistry*
  • Quinoxalines / pharmacology
  • Toll-Like Receptor 7 / antagonists & inhibitors*
  • Toll-Like Receptor 7 / chemistry*

Substances

  • Imidazoles
  • Pyrazines
  • Quinoxalines
  • TLR7 protein, human
  • Toll-Like Receptor 7