Comparative in vitro antimalarial activities against P. falciparum (Nigerian strain) of the bisthiazolium compound (T3), its bioprecursor (TE3), and chloroquine (CQ). The parasites were incubated with T3, TE3, or chloroquine for 48 h before the addition of [3H]hypoxanthine to determine cell viability. Values are the means ± SEMs of three independent experiments, each performed in duplicate.