In vitro cardiovascular effects of dihydroartemisin-piperaquine combination compared with other antimalarials

Abstract

The in vitro cardiac properties of dihydroartemisinin (DHA) plus piperaquine phosphate (PQP) were compared with those of other antimalarial compounds. Results with antimalarial drugs, chosen on the basis of their free therapeutic maximum concentration in plasma (C(max)), were expressed as the fold of that particular effect with respect to their C(max). The following tests were used at 37 °C: hERG (human ether-à-go-go-related gene) blockade and trafficking, rabbit heart ventricular preparations, and sodium and slow potassium ion current interference (I(Na) and I(Ks), respectively). Chloroquine, halofantrine, mefloquine, and lumefantrine were tested in the hERG studies, but only chloroquine, dofetilide, lumefantrine, and the combination of artemether-lumefantrine were used in the rabbit heart ventricular preparations, hERG trafficking studies, and I(Na) and I(Ks) analyses. A proper reference was used in each test. In hERG studies, the high 50% inhibitory concentration (IC(50)) of halofantrine, which was lower than its C(max), was confirmed. All the other compounds blocked hERG, with IC(50)s ranging from 3- to 30-fold their C(max)s. In hERG trafficking studies, the facilitative effects of chloroquine at about 30-fold its C(max) were confirmed and DHA blocked it at a concentration about 300-fold its C(max). In rabbit heart ventricular preparations, dofetilide, used as a positive control, revealed a high risk of torsades de pointes, whereas chloroquine showed a medium risk. Neither DHA-PQP nor artemether-lumefantrine displayed an in vitro signal for a significant proarrhythmic risk. Only chloroquine blocked the I(Na) ion current and did so at about 30-fold its C(max). No effect on I(Ks) was detected. In conclusion, despite significant hERG blockade, DHA-PQP and artemether-lumefantrine do not appear to induce potential torsadogenic effects in vitro, affect hERG trafficking, or block sodium and slow potassium ion currents.

Fig 1

Experimental protocol used to study the test article in the isolated arterially perfused rabbit ventricular preparations. The data recording (R) is made 30 to 60 s before the end of each stimulation period. Control, control perfusion.

Fig 2

Effects of various antimalarial drugs on hERG current at 0.1 Hz. Five concentrations of drugs were used, and concentrations ranged from 0.003 to 0.3 nM for halofantrine, from 0.058 to 5.8 μM for PQP, and from 0.3 to 30 μM for lumefantrine (LUM) and DHA. Six concentrations were used for chloroquine and mefloquine, and concentrations ranged from 0.1 to 30 μM. Five different cells were used for each concentration. The actual IC₅₀s are reported in the inset. Values represent mean ± SEM of five different cells.

Fig 3

Effects of various antimalarial drugs on hERG trafficking. Five concentrations of drugs were used, and concentrations ranged from 0.003 to 3 μM for PQP (with or without 2.4 or 7.2 μM DHA), from 1 to 100 μM for DHA, from 0.1 to 10 μM for chloroquine, from 0.3 to 30 μM for lumefantrine (LUM; with 0.18 μM artemether [ART]), and from 0.1 to 10 nM for dofetilide. Geldanamycin was given at 1 μM (black spot). Values represent mean ± SEM of five different cells.

Fig 4

Effects of various antimalarial drugs on TdP risk score in comparison with those of dofetilide. Values represent mean ± SEM of five preparations. Concentrations of drugs ranged from 0.003/0.1 to 3/10 μM for PQP without or with 2.4 or 7.2 μM DHA, from 1 to 100 μM for DHA, from 0.1 to 10 μM for chloroquine, from 0.3 to 30 μM for lumefantrine (LUM; without or with 0.18 μM artemether [ART]), and from 0.3 to 30 nM for dofetilide. Horizontal dashed lines represent scores of 1 and 7.25, which are considered to be associated with moderate and marked risks of torsades de pointes, respectively, when they are reached at concentrations less than 100× the free therapeutic plasma C_max (32).

Fig 5

Effects of various antimalarial drugs on I_Na ion current. Values represent mean ± SEM of five preparations. Five or six concentrations of drugs were used, and the concentrations ranged from 0.003/0.1 to 3/10 μM for PQP without or with 2.4 or 7.2 μM DHA, from 1 to 100 μM for DHA, from 0.1 to 10 μM for chloroquine, from 0.3 to 30 μM for lumefantrine (LUM; with 0.18 μM artemether [ART]), and from 0.1 to 10 nM for dofetilide.

Fig 6

Effects of various antimalarial drugs on I_Ks ion current. Values represent mean ± SEM of five preparations. Five or six concentrations of drugs were used, and the concentrations ranged from 0.003/0.1 to 3/10 μM for PQP without or with 2.4 or 7.2 μM DHA, from 1 to 100 μM for DHA, from 0.1 to 10 μM for chloroquine, from 0.3 to 30 μM for lumefantrine (LUM; with 0.18 μM artemether [ART]), and from 0.1 to 10 nM for dofetilide.