Antimalarial N1,N3-Dialkyldioxonaphthoimidazoliums: Synthesis, Biological Activity, and Structure-activity Relationships

Here we report the nanomolar potencies of N 1,N 3-dialkyldioxonaphthoimidazoliums against asexual forms of sensitive and resistant Plasmodium falciparum. Activity was dependent on the presence of the fused quinone-imidazolium entity and lipophilicity imparted by the N1/N3 alkyl residues on the scaffold. Gametocytocidal activity was also detected, with most members active at IC50 < 1 μM. A representative analog with good solubility, limited PAMPA permeability, and microsomal stability demonstrated oral efficacy on a humanized mouse model of P. falciparum.