Discovery of Imidazo[1,2-a]pyridine Ethers and Squaramides as Selective and Potent Inhibitors of Mycobacterial Adenosine Triphosphate (ATP) Synthesis

J Med Chem. 2017 Feb 23;60(4):1379-1399. doi: 10.1021/acs.jmedchem.6b01358. Epub 2017 Feb 3.


The approval of bedaquiline to treat tuberculosis has validated adenosine triphosphate (ATP) synthase as an attractive target to kill Mycobacterium tuberculosis (Mtb). Herein, we report the discovery of two diverse lead series imidazo[1,2-a]pyridine ethers (IPE) and squaramides (SQA) as inhibitors of mycobacterial ATP synthesis. Through medicinal chemistry exploration, we established a robust structure-activity relationship of these two scaffolds, resulting in nanomolar potencies in an ATP synthesis inhibition assay. A biochemical deconvolution cascade suggested cytochrome c oxidase as the potential target of IPE class of molecules, whereas characterization of spontaneous resistant mutants of SQAs unambiguously identified ATP synthase as its molecular target. Absence of cross resistance against bedaquiline resistant mutants suggested a different binding site for SQAs on ATP synthase. Furthermore, SQAs were found to be noncytotoxic and demonstrated efficacy in a mouse model of tuberculosis infection.

MeSH terms

  • Adenosine Triphosphate / metabolism*
  • Animals
  • Antitubercular Agents / chemistry
  • Antitubercular Agents / pharmacokinetics
  • Antitubercular Agents / pharmacology
  • Antitubercular Agents / therapeutic use*
  • Ethers / chemistry
  • Ethers / pharmacokinetics
  • Ethers / pharmacology
  • Ethers / therapeutic use
  • Humans
  • Mice
  • Mice, Inbred BALB C
  • Models, Molecular
  • Mycobacterium tuberculosis / drug effects*
  • Pyridines / chemistry
  • Pyridines / pharmacokinetics
  • Pyridines / pharmacology
  • Pyridines / therapeutic use*
  • Quinine / analogs & derivatives*
  • Quinine / chemistry
  • Quinine / pharmacokinetics
  • Quinine / pharmacology
  • Quinine / therapeutic use
  • Tuberculosis / drug therapy*
  • Tuberculosis / metabolism


  • Antitubercular Agents
  • Ethers
  • Pyridines
  • squaramide
  • Adenosine Triphosphate
  • Quinine