Relationship between Antimalarial Drug Activity, Accumulation, and Inhibition of Heme Polymerization in Plasmodium falciparum In Vitro

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Abstract
We have investigated the contribution of drug accumulation and inhibition of heme polymerization to the in vitro activities of a series of antimalarial drugs. Only those compounds exhibiting structural relatedness to the quinolines inhibited heme polymerization. We could find no direct correlation between in vitro activity against chloroquine-susceptible or chloroquine-resistant isolates and either inhibition of heme polymerization or cellular drug accumulation for the drugs studied. However, in vitro activity against a chloroquine-susceptible isolate but not a chloroquine-resistant isolate showed a significant correlation with inhibition of heme polymerization when the activity was normalized for the extent of drug accumulation. The importance of these observations to the rational design of new quinoline-type drugs and the level of agreement of these conclusions with current views on quinoline drug action and resistance are discussed.