Evaluation of In Vitro Inhibition of β-Hematin Formation: A Step Towards a Comprehensive Understanding of the Mechanism of Action of New Arylamino Alcohols

Currently, artemisinin-based combination therapy is recommended as first-line treatment of uncomplicated <i>falciparum</i> malaria. Arylamino alcohols (AAAs) such as mefloquine (MQ) are the preferred partner drugs due to their longer half-life, reliable absorption and strong antimalarial activity. However, the mode of action of MQ remains poorly understood and its neurotoxicity limits its use. Furthermore, the emergence of drug-resistant parasites requires development of new antimalarial drugs. The aim of this study was to evaluate the <i>β</i>-hematin inhibition capacity of three pairs of enantiopure AAAs <b>1-3</b> (<b><i>a</i>/<i>S</i></b> and <b><i>b</i>/<i>R</i></b>) derived from MQ or enpiroline (ENP), a pyridine-based MQ analog with strong antimalarial activity. Inhibition of <i>β</i>-hematin-the synthetic counterpart of hemozoin formation-was determined for each compound. Antimalarial activity against W2 and 3D7 <i>Plasmodium falciparum</i> strains as well as percentages of inhibition of <i>β</i>-hematin formation were compared to those of reference molecules, i.e., chloroquine (CQ), MQ and ENP. Furthermore, a cytotoxicity study on the human-derived hepatocarcinoma cell line HepG2 was performed. With high antimalarial activity, stronger ability to inhibit <i>β</i>-hematin formation and low cytotoxicity, AAAs <b>1a-b</b> and <b>2a</b> are the most promising. These findings provide a better understanding of their potential mechanisms of action and may pave the way toward developing new lead compounds.