Discovery of Imidazole-Based Inhibitors of Plasmodium falciparum cGMP-Dependent Protein Kinase

The discovery of new targets for the treatment of malaria, in particular those aimed at the pre-erythrocytic stage in the life cycle, advanced with the demonstration that orally administered inhibitors of Plasmodium falciparum cGMP-dependent protein kinase (PfPKG) could clear infection in a murine model. This enthusiasm was tempered by unsatisfactory safety and/or pharmacokinetic issues found with these chemotypes. To address the urgent need for new scaffolds, this paper presents initial structure-activity relationships in an imidazole scaffold at four positions, representative in vitro ADME, hERG characterization, and cell-based antiparasitic activity. This series of PfPKG inhibitors has good in vitro PfPKG potency, low hERG activity, and cell-based antiparasitic activity against multiple Plasmodium species that appears to be correlated with the in vitro potency.