In vitro activity of the enantiomers of N-desbutyl derivative of halofantrine.

The in vitro activity of the enantiomers of N-desbutylhalofantrine, the major human metabolite of halofantrine, was compared using the semi-microtest against the multidrug-resistant Plasmodium falciparum FCM 29/Cameroon clone. The mean 50% inhibitory concentration (IC50) values (+/- standard deviation) of the enantiomers were equivalent (2.07 +/- 0.41 and 1.70 +/- 0.33 nmol/L). The enantiomers of the metabolite of halofantrine, as well as those of the parent compound, have the same antimalarial activity. Since (+)-halofantrine and enantiomer-1 of the metabolite attain higher plasma concentrations in man, our study suggests that these enantiomers may be more active in vivo.