Desbutyl-benflumetol, a novel antimalarial compound:: In vitro activity in fresh isolates of Plasmodium falciparum from Thailand

Desbutyl-benflumetol (DBB) is a novel antimalarial compound closely related to benflumetol (lumefantrine), of which it is a putative metabolite. The in vitro response of Plasmodium falciparum Mae Hong Son and Mae Set, in northwest Thailand, in 1997 and 1998. In total, 155 fresh isolates were successfully tested using the World Health Organization standard in vitro microtest system (Mark II). The mean 50% effective concentration (EC50) and 90% effective concentration of DBB were 6.36 and 31.09 nmol/liter, respectively. The comparison of the activity of DBB and benflumetol yielded a highly significant potency ratio of 4.52, corresponding to a more than four times higher efficacy of DBB. A considerable potency difference was found between isolates from Mae Hong Son and those from Mae Set, reflecting lesser sensitivity in the area with marked resistance to mefloquine and quinine. This observation is also supported by a highly significant activity correlation,vith benflumetol (P < 0.001) and to a similar degree,vith mefloquine (P < 0.001), reflecting a close relationship of DBB with the class II aryl amino alcohol blood schizontocides. A less distinct association was also found with artemisinin, which was significant only at the EC50 level, and there was no correlation at all with chloroquine. DBB is a promising antimalarial compound that merits further investigation in order to define its practical therapeutic potential.