Activity of a trisubstituted pyrrole in inhibiting sporozoite invasion and blocking malaria infection.

Malaria infection is initiated by Plasmodium sporozoites infecting the liver. Preventing sporozoite infection would block the obligatory first step of the infection and perhaps reduce disease severity. In addition, such an approach would decrease Plasmodium vivax hypnozoite formation and therefore disease relapses. Here we describe the activity of a trisubstituted pyrrole, 4-[2-(4-fluorophenyl)-5-(1-methylpiperidine-4-yl)-1H-pyrrol-3-yl] pyridine, in inhibiting motility, invasion, and consequently infection by P. berghei sporozoites. In tissue culture, the compound was effective within the first 3 h of sporozoite addition to HepG2 cells. In vivo, intraperitoneal administration of the compound significantly inhibited liver-stage parasitemia in P. yoelii sporozoite-infected mice and prevented the appearance of blood-stage parasites. P. berghei sporozoites lacking the parasite cGMP-dependent protein kinase, the primary target of the compound in erythrocyte-stage parasites, remained infectious to HepG2 cells and sensitive to the drug. These results suggest that the drug has an additional target(s) in sporozoites. We propose that drugs that inhibit sporozoite infection offer a feasible approach to malaria prophylaxis.