Dual-acting diamine antiplasmodial and chloroquine resistance modulating agents.

On the basis of structural features known to be critical for the antimalarial activity, accumulation and uptake of chloroquine (CQ), as well as chemosensitization of CQ resistant Plasmodium falciparum, an exploratory novel series of potential dual acting antiplasmodial and chemosensitizing agents was designed and synthesized for biological evaluation. All four compounds contain a common alkyl side chain with two amino groups and differ only in the chemical nature of the hydrophobic aromatic moieties. Among them, N'-[4-(biphenyl-2-ylmethoxy)-benzyl]-N,N-dimethyl-propane-1,3-diamine (P7) displayed the greatest potential as a dual-acting antiplasmodial agent against CQ-resistant strains (IC50K1/RSA11<0.6 microM) and chemosensitizer (RMIK1=0.67; RMIRSA11=0.82) while displaying low in vitro cytotoxicity against a mammalian cell line (CHO). At 1 microM, P7 caused a 8.5 and 4-fold potentiation in CQ accumulation in resistant P. falciparum K1 and RSA11 strains, respectively. In a parallel experiment, 1 microM verapamil showed a 6.5 (K1) and 2 (RSA11)-fold increase in CQ accumulation. The preliminary studies point to structural features that may determine antiplasmodial and/or CQ resistance modulating activity in this new series of compounds. An additive effect was observed against both CQS (D10) and CQR (RSA11) strains when CQ and P7 were used at their corresponding IC50 concentrations in isobologram analysis.