Dual Molecules as New Antimalarials

Xavier   J.   Salom-Roig; Abdallah      Hamze; Michele      Calas; Henri   J.   Vial

doi:10.2174/1386207053328219

Abstract

A new antimalarial pharmacological approach based on inhibition of the plasmodial phospholipid metabolism has been developed. The drugs mimic choline structure and inhibit de novo phosphatidylcholine biosynthesis. Three generations of compounds were rationally designed. Bisquaternary ammonium salts showed powerful antimalarial activity, with IC50 in the nanomolar range. To remedy their low per os absorption, bioisosteric analogues (bis-amidines) were designed and exhibited similar powerful activities. Finally, the third generation compounds are bis-thiazolium salts and their non-ionic precursors: prodrugs, which in vivo can lead to thiazolium drugs after enzymatic transformation. The compounds are equally effective against multiresistant Plasmodium falciparum malaria. These molecules exert a very rapid cytotoxic effect against malarial parasites in the very low nanomolar range and are active in vivo against P. vinckei-infected mice, with ED50 lower than 0.2 mg / kg. They are able to cure highly infected mice and, retain full activity after a single injection. They also retain full activity against P. falciparum and P. cynomolgi in primate models with no recrudescence and at lower doses. Compounds are accumulated in P.falciparum-infected erythrocyte, which ensures their potency and specificity. Recently, we discovered that compounds also interact with malarial pigment enhancing the antimalarial effect. It is quite likely that they are dual molecules, exerting their antimalarial activity via two simultaneous toxic effects on the intracellular intraerythrocytic parasites. The current leader compounds are accessible in few steps from commercial products. These crystalline molecules present a remarkable biological activity and low toxicity which is promising for the development of a new antimalarial drug.

Keywords: antimalarials, plasmodium falciparum, phospholipid, phosphatidylcholine, choline analogues, malarial pigment, hemozoin, bisquaternary ammonium salts, bis-amidines, bis-thiazolium salts