Design, synthesis, and biological evaluation of new 1-(aryl-1H-pyrrolyl)(phenyl)methyl-1H-imidazole derivatives as antiprotozoal agents

We have designed and synthesized a series of new imidazole-based compounds structurally related to an antiprotozoal agent with nanomolar activity which we identified recently. The new analogs possess micromolar activities against T. b. rhodesiense and L. donovani and nanomolar potency against P. falciparum. Most of the analogs displayed the IC50 within the low nanomolar range against T. cruzi, with very high selectivity towards the parasite. Discussion of structure-activity relationships and in vitro biological data for the new compounds are provided against a number of different protozoa. The mechanism of action for the most potent derivatives (5i, 6a-c, 8b) was assessed by a target-based assays using recombinant T. cruzi CYP51. Bioavailability and efficacy of selected hits was assessed in a T. cruzi mouse model, where 6a and 6b reduced parasitemia in animals >99% following intraperitoneal administration of 25 mg/kg/day dose for four consecutive days.