Identification of 2,4-Disubstituted Imidazopyridines as Hemozoin Formation Inhibitors with Fast-Killing Kinetics and In Vivo Efficacy in the Plasmodium falciparum NSG Mouse Model

J Med Chem. 2020 Nov 12;63(21):13013-13030. doi: 10.1021/acs.jmedchem.0c01411. Epub 2020 Oct 25.

Abstract

A series of 2,4-disubstituted imidazopyridines, originating from a SoftFocus Kinase library, was identified from a high throughput phenotypic screen against the human malaria parasite Plasmodium falciparum. Hit compounds showed moderate asexual blood stage activity. During lead optimization, several issues were flagged such as cross-resistance against the multidrug-resistant K1 strain, in vitro cytotoxicity, and cardiotoxicity and were addressed through structure-activity and structure-property relationship studies. Pharmacokinetic properties were assessed in mice for compounds showing desirable in vitro activity, a selectivity window over cytotoxicity, and microsomal metabolic stability. Frontrunner compound 37 showed good exposure in mice combined with good in vitro activity against the malaria parasite, which translated into in vivo efficacy in the P. falciparum NOD-scid IL-2Rγnull (NSG) mouse model. Preliminary mechanistic studies suggest inhibition of hemozoin formation as a contributing mode of action.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antimalarials / chemistry*
  • Antimalarials / metabolism
  • Antimalarials / pharmacology
  • Antimalarials / therapeutic use
  • Disease Models, Animal
  • Half-Life
  • Hemeproteins / antagonists & inhibitors*
  • Hemeproteins / metabolism
  • Imidazoles / chemistry*
  • Imidazoles / metabolism
  • Imidazoles / pharmacology
  • Imidazoles / therapeutic use
  • Life Cycle Stages / drug effects
  • Malaria / drug therapy
  • Malaria / pathology
  • Mice
  • Mice, Inbred BALB C
  • Mice, Inbred NOD
  • Mice, SCID
  • Microsomes, Liver / metabolism
  • Plasmodium falciparum / drug effects
  • Plasmodium falciparum / metabolism
  • Plasmodium falciparum / physiology*
  • Protozoan Proteins / antagonists & inhibitors*
  • Protozoan Proteins / metabolism
  • Pyridines / chemistry*
  • Pyridines / metabolism
  • Pyridines / pharmacology
  • Pyridines / therapeutic use
  • Structure-Activity Relationship

Substances

  • Antimalarials
  • Hemeproteins
  • Imidazoles
  • Protozoan Proteins
  • Pyridines
  • imidazopyridine
  • hemozoin