Exploring Heteroaromatic Rings as a Replacement for the Labile Amide of Antiplasmodial Pantothenamides
Jinming Guan, Christina Spry, Erick T. Tjhin, Penghui Yang, Tanakorn Kittikool, Vanessa M. Howieson, Harriet Ling, Lora Starrs, Dustin Duncan, Gaétan Burgio, Kevin J. Saliba, Karine Auclair
Abstract
Malaria-causing Plasmodium parasites are developing resistance to antimalarial drugs, providing the impetus for new antiplasmodials. Although pantothenamides show potent antiplasmodial activity, hydrolysis by pantetheinases/vanins present in blood rapidly inactivates them. We herein report the facile synthesis and biological activity of a small library of pantothenamide analogues in which the labile amide group is replaced with a heteroaromatic ring. Several of these analogues display nanomolar antiplasmodial activity against Plasmodium falciparum and/or Plasmodium knowlesi, and are stable in the presence of pantetheinase. Both a known triazole and a novel isoxazole derivative were further characterized and found to possess high selectivity indices, medium or high Caco-2 permeability, and medium or low microsomal clearance in vitro. Although they fail to suppress Plasmodium berghei proliferation in vivo, the pharmacokinetic and contact time data presented provide a benchmark for the compound profile likely required to achieve antiplasmodial activity in mice and should facilitate lead optimization.