Plasmodium falciparum and Plasmodium berghei: effects of ornithine decarboxylase inhibitors on erythrocytic schizogony

Five ornithine decarboxylase inhibitors: alpha-difluoromethylornithine (DFMO) (eflornithine); alpha-monofluoromethyl-3,4-dehydroornithine; alpha-monofluoromethyl-3,4-dehydroornithine methyl ester; alpha-monofluoromethyl-3,4-dehydroornithine ethyl ester; and (2R,5R)-delta-methyl-alpha-acetylenic putrescine were shown to inhibit erythrocytic schizogony of Plasmodium falciparum in vitro and reduced spermidine levels in infected erthrocytes. Only DFMO was effective at limiting erythrocytic schizogony of P. berghei in vivo. Administration of DFMO as a 2% solution in the drinking water for 4 days reduced parasitemia in mice by 50% in a 4-day suppression test but did not increase survival time of infected mice. This is the first demonstration of an effect of DFMO on plasmodial erythrocytic schizogony in vivo and suggests that interference with polyamine biosynthesis may, in fact, be a viable chemotherapeutic target in erythrocytic malaria.