arterolane and furamidine

Using synchronized cultures of Plasmodium falciparum, the time- and concentration-dependent growth changes of erythrocytic parasite stages to DB75, piperaquine, OZ277 and OZ401 were investigated in vitro over a concentration range of approximately 1-100x the IC(50) of piperaquine, OZ277 and OZ401 and approximately 10-1000x the IC(50) of DB75.. The effects of timed in vitro exposure (1, 6, 12 or 24 h) were monitored by the incorporation of [(3)H]hypoxanthine into the parasite nucleic acids.. After 1 h of exposure to the highest concentration of the compound followed by removal of the compound, the growth of all stages of P. falciparum was reduced to < 34% for DB75 and 15% for piperaquine, OZ277 and OZ401 compared with untreated control parasites. At this time point, no stage-specific effects were observed at any of the concentrations. Strong inhibition (< or = 10% growth) of all parasite stages was observed when the parasites were exposed to 10x or 100x the IC(50) of OZ277 and OZ401 for > or = 6 h. At the 6 h incubation time point, DB75 was more active against mature parasite stages, with the IC(50)s of young ring forms elevated up to 7-fold. This trend was observed up to 12 h, but was only statistically significant at the lowest concentration. Interestingly, the stage-specific effect of DB75 on ring forms was not detectable when washing procedures were omitted. This indicates a cytostatic action of DB75 on P. falciparum ring forms.. The current study suggests that P. falciparum ring stages are less susceptible to DB75. A milder and often statistically insignificant stage-specific trend was observed for piperaquine, whereas OZ277 and OZ401 were equally active against the erythrocytic parasite stages.

Topics: Animals; Antimalarials; Benzamidines; Heterocyclic Compounds; Heterocyclic Compounds, 1-Ring; Inhibitory Concentration 50; Peroxides; Plasmodium falciparum; Quinolines; Spiro Compounds; Time Factors

Plasmodium vivax is an important human pathogen causing malaria in more temperate climates of the world. Similar to Plasmodium falciparum, the causative agent for malaria tropica, drug resistance is beginning to emerge for this parasite species and this hampers adequate treatment of infection. We have used a short-term ex vivo drug assay to monitor activity of OZ277 (RBx-11160), a fully synthetic anti-malarial peroxide, and the diamidine DB75 against P. vivax. For both compounds as well as the anti-malarial reference compounds artesunate, artemether, and chloroquine, the in vitro IC(50) values were determined in one-cycle hypoxanthine incorporation assays. Results from such assays were found to be very similar compared to IC(50) values obtained from one-cycle P. falciparum hypoxanthine assays. We demonstrate the anti-parasite activity of OZ277 and the reference compounds to be faster than that of DB75. These data warrant clinical testing of OZ277 against P. vivax malaria and support recent data on clinical activity against P. vivax for DB75.

Topics: Animals; Antimalarials; Aotidae; Artemether; Artemisinins; Artesunate; Benzamidines; Chloroquine; Drug Resistance; Heterocyclic Compounds, 1-Ring; Inhibitory Concentration 50; Malaria, Vivax; Parasitemia; Peroxides; Plasmodium falciparum; Plasmodium vivax; Sesquiterpenes; Spiro Compounds; Time Factors