In vitro and in vivo potentiation of artemisinin and synthetic endoperoxide antimalarial drugs by metalloporphyrins.

The in vitro potentiation of artemisinin by synthetic manganese porphyrin complexes has been recently reported (F. Benoit-Vical, A. Robert, and B. Meunier, Antimicrob. Agents Chemother. 43:2555-2558, 1999). Since the activity of artemisinin and synthetic antimalarial endoperoxides is related to their interaction with heme (S. R. Meshnick, A. Thomas, A. Ranz, C. M. Xu, and H. Z. Pan, Mol. Biochem. Parasitol. 49:181-190, 1991), an improvement of their efficiency may be expected in the presence of a synthetic metalloporphyrin having the same activating role as endogenous heme. With the aim to boost the activity of antimalarial endoperoxide drugs, we were thus led to evaluate the in vitro and in vivo potentiation of natural and synthetic drugs of this family by a nontoxic and cheap metalloporphyrin. The potentiation of artemisinin, beta-artemether, and arteflene (Ro 42-1611) by synthetic heme models is reported. In vitro studies on the chloroquine-resistant Plasmodium falciparum FcB1-Columbia strain indicate a synergistic effect of the manganese complex of meso-tetrakis(4-sulfonatophenylporphyrin) (Mn-TPPS) on the activity of artemisinin or beta-artemether, whereas this heme model has no influence on the activity of arteflene. A significant synergistic effect on rodent malaria was also observed in vivo between artemisinin and Mn-TPPS using Plasmodium vinckei petteri strain.