Safety, Pharmacokinetics, and Mosquito‐Lethal Effects of Ivermectin in Combination With Dihydroartemisinin‐Piperaquine and Primaquine in Healthy Adult Thai Subjects

Mass administration of antimalarial drugs and ivermectin are being considered as potential accelerators of malaria elimination. The safety, tolerability, pharmacokinetics, and mosquito‐lethal effects of combinations of ivermectin, dihydroartemisinin‐piperaquine, and primaquine were evaluated. Coadministration of ivermectin and dihydroartemisinin‐piperaquine resulted in increased ivermectin concentrations with corresponding increases in mosquito‐lethal effect across all subjects. Exposure to piperaquine was also increased when coadministered with ivermectin, but electrocardiograph QT‐interval prolongation was not increased. One subject had transiently impaired liver function. Ivermectin mosquito‐lethal effect was greater than predicted previously against the major Southeast Asian malaria vectors. Both Anopheles dirus and Anopheles minimus mosquito mortality was increased substantially (20‐fold and 35‐fold increase, respectively) when feeding on volunteer blood after ivermectin administration compared with in vitro ivermectin‐spiked blood. This suggests the presence of ivermectin metabolites that impart mosquito‐lethal effects. Further studies of this combined approach to accelerate malaria elimination are warranted.

. Adverse events summary, stratified by treatment regimen. 12 61 Data are shown as number of adverse events (AEs) for each organ classification, stratified by treatment regimen. IVM is ivermectin, DHA-PQP is dihydroartemisinin-piperaquine, and PQ is primaquine. a Female subject with AST grade IV which was considered a SAE. b Male subject who was hospitalized due to dengue hemorrhagic fever.   Table S3 illustrates the pharmacokinetic parameters for each compound separated by drug regimen. IVM represents ivermectin, PQ represents primaquine and DHA-PQP represents dihydroartemisinin-piperaquine. Values are presented as median (minimal valuemaximal value). AUCT is the total exposure, measured as area under the concentration-time curve, up until the last observation, Cmax is the maximum concentration, and Tmax is the time to reach the maximum concentration. It is well known that these are not always optimal for a particular data set and an optimal correction factor was calculated using all available QT and associated heart rate data (Eq. 3).

ln( ) = × ln( ) + Equation 3
Uncorrected and corrected QT-intervals (QTcF, QTcB and QTcS) were plotted against individual heart rates to assess the appropriateness of the evaluated correction factor.
Any correction factor that did not result in a significant residual trend was assumed to appropriately correct this data. Corrected QT-intervals (QTc) were used to evaluate the potential electrocardiographic impact of evaluated drugs and combinations. Individually calculated differences between baseline QTc and observed QTc after drug administration (∆QTc) was used to evaluate the QT-interval prolonging properties of drug combinations. A paired ANOVA-test was used to evaluate statistical differences between drug regimens. Furthermore, individual ∆QTc were also plotted against corresponding drug concentrations and ordinary linear regression was used to quantify the magnitude of potential QT-interval prolongations. All QT data were analyzed and visualized using GraphPad Prism. Mosquitoes were maintained in an incubator at 25 ± 1°C and 80 ± 10% humidity, and offered 10% sucrose ad libitum. Mosquito survival was monitored daily for ten days and any dead mosquitoes were removed by aspiration and recorded. At day 10 post blood meal any remaining mosquitoes were frozen and recorded as alive.

Mosquitoes
Piperaquine compound was dissolved in 0.5% lactic acid to 10 mg/ml and serially diluted in distilled water, then 10 μl was added to 990 μl of whole blood to achieve a range of concentrations from 1 -100,000 ng/ml. Controls consisted of 0.5% lactic acid diluted in distilled water to match the highest concentration of piperaquine fed to mosquitoes. Blood meals were then fed to mosquitoes via membrane feeders.
Mosquitoes were maintained in the same incubator as trial mosquitoes and their mortality was observed daily for ten days, any remaining mosquitoes at day 10 were frozen and counted as alive. Two replicates with An. dirus (n = 567) were performed.
Survival curves at each time point were compared to baseline within each treatment regimen using Log-Rank survival curve analysis (Mantel-Cox method).
Cumulative mosquito mortality at day 10 between treatment groups were assessed at each time point using a Z-test for proportions. The lethal concentration that kills 50% of mosquitoes (LC50) were estimated using a normalized concentration-response analysis (IC50 and Hill). All mosquito survival analyses performed with GraphPad Prism. Hazard ratios for mosquito mortality, calculated at each day post-blood meal using Poisson regression analysis using STATA. There were several instances when no mosquitoes died in the control group at several days post-feeding within a regimen, therefore, hazard ratios could only be calculated using data from all four drug regimens combined.
Additional References: