Dihydroquinazolinone inhibitors of proliferation of blood and liver stage malaria parasites.

Drugs that target both the liver and blood stages of malaria will be needed to reduce the disease's substantial worldwide morbidity and mortality. Evaluation of a 259-member library of compounds that block proliferation of the blood stage of malaria revealed several scaffolds--dihydroquinazolinones, phenyldiazenylpyridines, piperazinyl methyl quinolones, and bis-benzimidazoles--with promising activity against the liver stage. Focused structure-activity studies on the dihydroquinazolinone scaffold revealed several molecules with excellent potency against both blood and liver stages. One promising early lead with dual activity is 2-(p-bromophenyl)-3-(2-(diethylamino)ethyl)-2,3-dihydroquinazolin-4(1H)-one with 50% effective concentrations (EC50s) of 0.46 µM and 0.34 µM against liver stage Plasmodium berghei ANKA and blood stage Plasmodium falciparum 3D7 parasites, respectively. Structure-activity relationships revealed that liver stage activity for this compound class requires a 3-dialkyl amino ethyl group and is abolished by substitution at the ortho-position of the phenyl moiety. These compounds have minimal toxicity to mammalian cells and are thus attractive compounds for further development.