Structure-activity relationship studies and Plasmodium life cycle profiling identifies pan-active N-aryl-3-trifluoromethyl pyrido[1,2-a]benzimidazoles which are efficacious in an in vivo mouse model of malaria

Structure-activity relationship studies involving N-aryl-3-trifluoromethyl pyrido[1,2-a] benzimidazoles (PBI) identified several compounds possessing potent in vitro activities against the asexual blood, liver and gametocyte stages of the Plasmodium parasite with no cross-resistance to chloroquine. Frontrunner lead compounds with good in vitro absorption, distribution, metabolism and excretion (ADME) profiles were subjected to in vivo proof-of-concept studies in NMRI mice harboring the rodent P. berghei infection. This led to the identification of compounds 10 and 49, effecting 98% and 99.93% reduction in parasitemia with mean survival days of 12 and 14, respectively, at an oral dose of 4x50 mg/kg. In vivo pharmacokinetics studies on 10 revealed slow absorption, low volume of distribution and low clearance profiles. Furthermore, this series displayed low propensity to inhibit the human ether-a-go-go-related gene (hERG) potassium ion channel whose inhibition is associated with cardiotoxicity.