In vitro antimalarial activity and drug interactions of fenofibric acid.

Plasmodium falciparum has developed resistance to most available treatments, underscoring the need for novel antimalarial drugs. Fibrates are lipid-modifying agents used to reduce morbidity and mortality associated with cardiovascular disease. They may have antimalarial activity through modulation of P-glycoprotein and ATP-binding cassette subfamily A member (ABC-1)-mediated nutrient transport and/or via a putative peroxisome proliferator-activated receptor alpha-like protein. We therefore examined in vitro antimalarial activities of fibrates and their interactions with chloroquine and dihydroartemisinin in chloroquine-sensitive (3D7) and chloroquine-resistant (W2mef) strains of P. falciparum using the conventional isotopic assay microtechnique. A bioassay was used to assess inhibition activities of human plasma after therapeutic fenofibrate doses. Fenofibric acid, the main metabolite of fenofibrate, was the most potent of the fibrates tested, with mean 50% inhibitory concentrations of 152 nM and 1,120 nM for chloroquine-sensitive and -resistant strains, respectively. No synergistic interaction between fibrates and chloroquine or dihydroartemisinin was observed. Plasma fenofibric acid concentrations, quantified by high-performance liquid chromatography in seven healthy volunteers after treatment (mean, 15.3 mg/liter, or 48 μM), inhibited P. falciparum. BLAST analysis revealed the likely presence of an ABC-1 transporter homolog in P. falciparum. Our findings demonstrate that fenofibric acid has activity similar to the activities of conventional antimalarial drugs at concentrations well below those achieved after therapeutic doses. It may inhibit P. falciparum growth by inhibiting intracellular lipid transport.