Bioisosteric transformations and permutations in the triazolopyrimidine scaffold to identify the minimum pharmacophore required for inhibitory activity against Plasmodium falciparum dihydroorotate dehydrogenase

J Med Chem. 2012 Sep 13;55(17):7425-36. doi: 10.1021/jm300351w. Epub 2012 Aug 21.


Plasmodium falciparum causes approximately 1 million deaths annually. However, increasing resistance imposes a continuous threat to existing drug therapies. We previously reported a number of potent and selective triazolopyrimidine-based inhibitors of P. falciparum dihydroorotate dehydrogenase that inhibit parasite in vitro growth with similar activity. Lead optimization of this series led to the recent identification of a preclinical candidate, showing good activity against P. falciparum in mice. As part of a backup program around this scaffold, we explored heteroatom rearrangement and substitution in the triazolopyrimidine ring and have identified several other ring configurations that are active as PfDHODH inhibitors. The imidazo[1,2-a]pyrimidines were shown to bind somewhat more potently than the triazolopyrimidines depending on the nature of the amino aniline substitution. DSM151, the best candidate in this series, binds with 4-fold better affinity (PfDHODH IC(50) = 0.077 μM) than the equivalent triazolopyrimidine and suppresses parasites in vivo in the Plasmodium berghei model.

Publication types

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

MeSH terms

  • Animals
  • Dihydroorotate Dehydrogenase
  • Enzyme Inhibitors / chemistry
  • Enzyme Inhibitors / pharmacology*
  • Mice
  • Molecular Mimicry
  • Oxidoreductases Acting on CH-CH Group Donors / antagonists & inhibitors*
  • Plasmodium berghei / drug effects
  • Plasmodium falciparum / enzymology*
  • Pyrimidines / chemistry
  • Pyrimidines / pharmacology*
  • Structure-Activity Relationship


  • Dihydroorotate Dehydrogenase
  • Enzyme Inhibitors
  • Pyrimidines
  • Oxidoreductases Acting on CH-CH Group Donors