Selective high-performance liquid chromatographic determination of artesunate and alpha- and beta-dihydroartemisinin in patients with falciparum malaria

An albumin-binding dimeric prodrug nanoparticle with long blood circulation and light-triggered drug release for chemo-photodynamic combination therapy against hypoxia-induced metastasis of lung cancer

Photodynamic therapy (PDT) has been widely used in cancer therapy, but its therapeutic effect is reduced by the aggravating hypoxic microenvironment via upregulating hypoxia-associated proteins and promoting tumor metastasis. To mitigate these issues, we designed an albumin-binding and light-triggered core-shell dimeric prodrug nanoparticle to inhibit hypoxia-induced tumor metastasis and enhance the PDT efficacy. The prodrug nanoparticles, Ce6&DHA-S-DHA@CMN NPs (CDC NPs), were prepared using a single thioether-linked dihydroartemisinin (DHA) dimer co-encapsulated with Chlorin e6 (Ce6) and stabilized by albumin-capturing maleimide- and hypoxia-sensitive 2-nitroimidazole-modified carboxymethyl chitosan (CMCTS-MAL&NI, CMN for short). Upon laser irradiation, Ce6 could generate reactive oxygen species (ROS), which not only exerted the effect of the PDT but also broke the ROS-sensitive single thioether bridge in the dimeric prodrug DHA-S-DHA, thus accelerating the disassembly of the nanoparticles. DHA-S-DHA served as both an ROS-responsive carrier for Ce6 and a chemotherapeutic drug, synergizing with PDT and inhibiting tumor metastasis by downregulating hypoxia-inducible factor-1α (HIF-1α)/vascular endothelial growth factor (VEGF). Polyethylene glycol (PEG) modification has been widely used to stabilize hydrophobic prodrug nanoparticles and prolong the circulation time, but the PEGylated nanoparticles always suffer from accelerated blood clearance (ABC), a phenomenon which restricts their application severely. In this study, PEG was replaced by an amphipathic micelle, CMN, which could specifically capture albumin in the blood, conferring the nanoparticles long circulation and no ABC phenomenon. Under the aggravating hypoxic condition during PDT, the conversion of 2-nitroimidazole groups to 2-aminoimidazole groups in CMN could destabilize the structure of the shell and accelerate drug release. Results showed that the novel CDC NPs exhibited unique advantages in chemo-photodynamic combination therapy, such as long systemic circulation, high tumor accumulation, light-triggered drug release, HIF-1α/VEGF downregulation, and anti-metastasis efficacy, which provided a new route to overcome the ABC phenomenon of the PEGylated prodrug nanoparticles and reverse the hypoxia-induced metastasis simultaneously.

Rapid quantification of artemisinin derivatives in antimalarial drugs with dipstick immunoassays

Substandard antimalarial drugs will result in unsatisfied therapeutic efficacy and increase the risk of resistance development. The point-of-care, qualitative, or semi-quantitative dipstick immunoassays cannot differentiate the substandard drugs with confidence. A rapid and quantitative analytical method that can be used under field conditions is needed. Here, three lateral flow immunoassays (LFIAs) based on colloidal gold nanobeads (CGN) as labels were developed for quantification of artemether, dihydroartemisinin and artesunate contents in antimalarial drugs with the aid of a portable optical scanner. Also, time-resolved fluorescent nanobeads (TRFN)-LFIA, coupled with a portable fluorescent lateral flow reader, was developed for quantification of artesunate. Commercial antimalarial drugs were used to validate these LFIAs with comparison to the gold standard high-performance liquid chromatography (HPLC) method. The drug contents estimated with these CGN-LFIAs were in the range of 85.5-109.3% of the contents determined by HPLC with a coefficient of variation (CV) of 4.5-13.0%. The TRFN-LFIA results were in the range of 93.7-108.4% of contents determined by HPLC with a CV of 5.2-8.9%. There were no significant differences between the results of CGN-LFIA and TRFN-LIFA (P = 0.5277, t-test). Both types of LFIAs with portable readers may be used for quantitation of active ingredients in antimalarial drugs and for screening substandard antimalarial drugs in resource-limiting settings.

Artemisia annua, a Traditional Plant Brought to Light

Traditional remedies have been used for thousand years for the prevention and treatment of infectious diseases, particularly in developing countries. Of growing interest, the plant Artemisia annua, known for its malarial properties, has been studied for its numerous biological activities including metabolic, anti-tumor, anti-microbial and immunomodulatory properties. Artemisia annua is very rich in secondary metabolites such as monoterpenes, sesquiterpenes and phenolic compounds, of which the biological properties have been extensively studied. The purpose of this review is to gather and describe the data concerning the main chemical components produced by Artemisia annua and to describe the state of the art about the biological activities reported for this plant and its compounds beyond malaria.

Cardiac Arrhythmia in a Patient with Sickle Cell Anemia and Falciparum Malaria Treated with Intravenous Artesunate

Treatment of severe malaria with artemisinin derivatives in patients with comorbid conditions such as sickle cell anemia must be considered with precaution. We report here a case of possibly undocumented ventricular arrhythmia in a sickle cell anemia patient diagnosed with Plasmodium falciparum malaria and treated with intravenous artesunate. The patient suffered from wide complex tachycardia after treatment with artesunate 170 mg (2.4 mg/kg) i.v. bolus, tachycardia was managed with amiodarone (150 mg i.v. for 10 minutes). Electrocardiographic abnormalities, including QT prolongation, are common in patients with sickle cell anemia. The mortality rate in sickle cell anemia patients due to cardiovascular and pulmonary complications remains high. The probability of precipitation of ventricular arrhythmias may increase in patients with sickle cell anemia, diagnosed with malaria and treated with artemisinin derivatives.

Development of monoclonal antibody-based immunoassays for quantification and rapid assessment of dihydroartemisinin contents in antimalarial drugs

Dihydroartemisinin (DHA) is one of the artemisinin derivatives widely used in artemisinin-based combination therapies (ACTs) for malaria treatment. The availability of a point-of-care device for estimation of DHA quantity would allow a quick quality assessment of the DHA-containing drugs. In this study, 9-O-succinylartemisinin was obtained from microbial fermentation of artemisinin, which was hydrogenated to 9-O-succinyldihydroartemisinin as the hapten for DHA. A monoclonal antibody (mAb), designated as 2G₁1G₄, was identified after screening the hybridoma library, which showed 52.3% cross reactivity to artemisinin, but low or no cross reactivity to artesunate, artemether, and several ACTs partner drugs. Based on this mAb, a highly-sensitive, indirect competitive enzyme-linked immunosorbent assay was designed, which showed 50% inhibition concentration of DHA at 1.16 ng/mL, a working range of 0.26-4.87 ng/mL, and limit of detection of 0.18 ng/mL. In addition, a colloidal gold-based lateral flow immunoassay (dipstick) was developed with an indicator range (indicating sensitivity) of 50-100 ng/mL. This dipstick was evaluated for determination of DHA contents in commercial drugs and the results were highly agreeable with those determined by high-performance liquid chromatography.

Artemisinin and its derivatives can significantly inhibit lung tumorigenesis and tumor metastasis through Wnt/β-catenin signaling

Non-small-cell lung cancer (NSCLC) is the most prevalent malignancy worldwide given its high incidence, considerable mortality, and poor prognosis. The anti-malaria compounds artemisinin (ART), dihydroartemisinin (DHA), and artesunate (ARTS) reportedly have anti-cancer potential, although the underlying mechanisms remain unclear. In this work, we used flow cytometry to show that ART, DHA, and ARTS could inhibit the proliferation of A549 and H1299 cells by arresting cell cycle in G1 phase. Meanwhile, tumor malignancy including migration, invasion, cancer stem cells, and epithelial-mesenchymal transition were also significantly suppressed by these compounds. Furthermore, ART, DHA, and ARTS remarkably decreased tumor growth in vivo. By using IWP-2, the inhibitor of Wnt/β-catenin pathway, and Wnt5a siRNA, we found that ART, DHA, and ARTS could render tumor inhibition partially dependent on Wnt/β-catenin inactivation. These compounds could strikingly decrease the protein level of Wnt5-a/b and simultaneously increase those of NKD2 and Axin2, ultimately resulting in β-catenin downregulation. In summary, our findings revealed that ART, DHA, and ARTS could suppress lung-tumor progression by inhibiting Wnt/β-catenin pathway, thereby suggesting a novel target for ART, DHA, and ARTS in cancer treatment.

Quality Testing of Artemisinin-Based Antimalarial Drugs in Myanmar

Artemisinin-based combination therapies are the frontline treatment of Plasmodium falciparum malaria. The circulation of falsified and substandard artemisinin-based antimalarials in Southeast Asia has been a major predicament for the malaria elimination campaign. To provide an update of this situation, we purchased 153 artemisinin-containing antimalarials, as convenience samples, in private drug stores from different regions of Myanmar. The quality of these drugs in terms of their artemisinin derivative content was tested using specific dipsticks for these artemisinin derivatives, as point-of-care devices. A subset of these samples was further tested by high-performance liquid chromatography (HPLC). This survey identified that > 35% of the collected drugs were oral artesunate and artemether monotherapies. When tested with the dipsticks, all but one sample passed the assays, indicating that the detected artemisinin derivative content corresponded approximately to the labeled contents. However, one artesunate injection sample was found to contain no active ingredient at all by the dipstick assay and subsequent HPLC analysis. The continued circulation of oral monotherapies and the description, for the first time, of falsified parenteral artesunate provides a worrisome picture of the antimalarial drug quality in Myanmar during the malaria elimination phase, a situation that deserves more oversight from regulatory authorities.

Pharmacokinetics of Artesunate following Oral and Rectal Administration in Healthy Sudanese Volunteers

The aims of this study were to determine the pharmacokinetic parameters of a single dose of 200 mg oral and rectal artesunate in healthy volunteers, and to suggest a rational dosage regimen for rectal administration. The study design was a randomized open cross- over study of 12 healthy volunteers; the analytical method used was a reversed phase high performance liquid chromatography with post column derivatization and subsequent ultraviolet detection.

Pharmacokinetic parameters were derived from the main metabolite α-dihydroartemisinin data due to the rapid disappearance of artesunate from the plasma.

Dihydroartemisinin following oral administration of artesunate had a significantly higher AUC0-∞ ( P<0.05 95% confidence interval (Cl) −1168.73, −667.61 ng.h/mL−1) and Cmax( P<0.05;95%Cl −419.73, −171.44 ng/mL− 1, and had shorter tmax ( P<0.05; 95% Cl −0.97, −0.10 h) than that following rectal artesunate. There was no statistically significant difference in the elimination halflife between both routes of administration ( P> 0.05; 95% Cl −0.14, 0.53 h). The relative bioavailability of rectal artesunate was [mean (coefficient of variation%)54.9(24.8%)%]. On the basis of these data an 8 hourly dosing regimen per day with rectal artesunate is proposed.

Cysteamine broadly improves the anti-plasmodial activity of artemisinins against murine blood stage and cerebral malaria

BACKGROUND

The potential emergence and spread of resistance to artemisinins in the Plasmodium falciparum malaria parasite constitutes a major global health threat. Hence, improving the efficacy of artemisinins and of artemisinin-based combination therapy (ACT) represents a major short-term goal in the global fight against malaria. Mice defective in the enzyme pantetheinase (Vnn3) show increased susceptibility to blood-stage malaria (increased parasitaemia, reduced survival), and supplementation of Vnn3 mutants with the reaction product of pantetheinase, cysteamine, corrects in part the malaria-susceptibility phenotype of the mutants. Cysteamine (Cys) is a small, naturally occurring amino-thiol that has very low toxicity in vivo and is approved for clinical use in the life-long treatment of the kidney disorder nephropathic cystinosis.

METHODS

The ability of Cys to improve the anti-plasmodial activity of different clinically used artemisinins was tested. The effect of different CYS/ART combinations on malarial phenotypes (parasite blood-stage replication, overall and survival from lethal infection) was assessed in a series of in vivo experiments using Plasmodium strains that induce either blood-stage (Plasmodium chabaudi AS) or cerebral disease (Plasmodium berghei ANKA). This was also evaluated in an ex vivo experimental protocol that directly assesses the effect of such drug combinations on the viability of Plasmodium parasites, as measured by the ability of tested parasites to induce a productive infection in vivo in otherwise naïve animals.

RESULTS

Cys is found to potentiate the anti-plasmodial activity of artesunate, artemether, and arteether, towards the blood-stage malaria parasite P. chabaudi AS. Ex vivo experiments, indicate that potentiation of the anti-plasmodial activity of artemisinins by Cys is direct and does not require the presence of host factors. In addition, potentiation occurs at sub-optimal concentrations of artemisinins and Cys that on their own have little or no effect on parasite growth. Cys also dramatically enhances the efficacy and protective effect of artemisinins against cerebral malaria induced by infection with the P. berghei ANKA parasite.

CONCLUSION

These findings indicate that inclusion of Cys in current formulations of ACT, or its use as adjunct therapy could improve the anti-plasmodial activity of artemisinin, decrease mortality in cerebral malaria patients, and prevent or delay the development and spread of artemisinin resistance.

Rapid evaluation of artesunate quality with a specific monoclonal antibody-based lateral flow dipstick

Artesunate is a frontline antimalarial drug for treating Plasmodium falciparum malaria. To produce specific antibodies to artesunate, the carboxyl group of artesunate was directly conjugated to carrier protein as the immunogen. A specific monoclonal antibody (mAb) 3D82G6 against artesunate was obtained by high-throughput screening of positive hybridoma clones. This monoclonal antibody had 4.0, 0.5, and 0.9 % cross reactivities with artemisinin, dihydroartemisinin, and artemether, respectively. A dipstick immunoassay was developed, and the indicator range for artesunate was 1000-2000 ng mL(-1). No interference was observed with artemisinin, dihydroartemisinin, artemether, and other commonly used antimalarial drugs for up to 20,000 ng mL(-1). The dipsticks were used for determination of artesunate contents in commercial drugs, and the results were agreeable with those determined by high-performance liquid chromatography. This dipstick, with its specificity and sensitivity for artesunate and simplicity to use, makes it a potential point-of-care device for rapid quality evaluation of artesunate-containing antimalarial drugs. Graphical Abstract Specific monoclonal antibody-based lateral flow dipstick for artesunate.

Artesunate, an anti-malarial drug, has a potential to inhibit HCV replication

Hepatitis C virus (HCV) infection is a major global health issue. Although the search for HCV treatments has resulted in great achievements, the current treatment methods have limitations, and new methods and drugs for hepatitis C treatment are still required. The aim of the present study was to investigate the effects of artesunate (ART) on HCV replication and compared these effects with those of ribavirin (RBV) and interferon-2b (IFN). The study was performed in HCV-infection cell models (JFH1-infected Huh7.5.1 and OR6 cell lines). Our results showed that the antimalarial drug ART inhibited HCV replicon replication in a dose- and time-dependent manner at a concentration that had no effect on the proliferation of exponentially growing host cells, and the inhibitory effect on HCV replication was stronger than RBV but weaker than IFN, as determined by qPCR, luciferase assays, and Western blot analysis. Furthermore, the combination of ART and IFN resulted in a greater inhibition of HCV replication. These findings demonstrated that ART had an inhibitive effect on HCV replication and may be a novel supplemental co-therapy with IFN and RBV for HCV and as an alternative strategy to combat resistance mechanisms that have emerged in the presence of DAA agents.

Reprint of "Pharmacokinetic modelling of the anti-malarial drug artesunate and its active metabolite dihydroartemisinin"

A four compartment mechanistic mathematical model is developed for the pharmacokinetics of the commonly used anti-malarial drug artesunate and its principle metabolite dihydroartemisinin following oral administration of artesunate. The model is structurally unidentifiable unless additional constraints are imposed. Combinations of mechanistically derived constraints are considered to assess their effects on structural identifiability and on model fits. Certain combinations of the constraints give rise to locally or globally identifiable model structures. Initial validation of the model under various combinations of the constraints leading to identifiable model structures was performed against a dataset of artesunate and dihydroartemisinin concentration-time profiles of 19 malaria patients. When all the discussed constraints were imposed on the model, the resulting globally identifiable model structure was found to fit reasonably well to those patients with normal drug absorption profiles. However, there is wide variability in the fitted parameters and further investigation is warranted.

Pharmacokinetics of artesunate alone and in combination with sulfadoxine/pyrimethamine in healthy Sudanese volunteers

Artesunate (AS) in combination with sulfadoxine/pyrimethamine (SP) is the first-line therapy for management of uncomplicated Plasmodium falciparum malaria in Sudan. The objective of this study was to assess the potential impact of SP on the pharmacokinetics of AS and its active metabolite, dihydroartemisinin (DHA), in healthy adults. A single-dose, randomized, open-label, crossover study design with a washout period of three weeks was performed with 16 volunteers. After oral administration of AS alone or in combination with SP, Tmax values of AS and DHA were significantly prolonged in the combination group (P < 0.05). However, there was no significant effect on the other pharmacokinetic parameters (P > 0.05). The t1/2 values of AS and DHA were significantly higher in females than in males (P < 0.05). The present findings suggest that co-administration of SP with AS has no clinically relevant impact on the pharmacokinetics of AS or DHA in healthy persons.

Nanocapsules based on mPEGylated artesunate prodrug and its cytotoxicity

mPEGylated artesunate prodrug was synthesized via esterification between poly(ethylene glycol) monomethyl ether (mPEG) and artesunate (ART). The product was inclined to form nanocapsules in aqueous media due to its amphiphilic nature. These nanocapsules showed narrow size distribution, with an average particle size of 88.7 nm measured by dynamic laser scattering (DLS). Their vesical morphology was further confirmed by transmission electron microscopy (TEM). We found that the release of ART from the nanocapsules was controllable, which was contributed to the easily hydrolyzed property of the ester bond. In addition, the cytotoxicity of the prodrug against L1210 and MCF7 cell lines showed an essential decrease compared with the free ART. These results present a new strategy in designing anti-tumor ART nanocapsules for targeting tumor cells.

Pharmacokinetic modelling of the anti-malarial drug artesunate and its active metabolite dihydroartemisinin

A four compartment mechanistic mathematical model is developed for the pharmacokinetics of the commonly used anti-malarial drug artesunate and its principle metabolite dihydroartemisinin following oral administration of artesunate. The model is structurally unidentifiable unless additional constraints are imposed. Combinations of mechanistically derived constraints are considered to assess their effects on structural identifiability and on model fits. Certain combinations of the constraints give rise to locally or globally identifiable model structures. Initial validation of the model under various combinations of the constraints leading to identifiable model structures was performed against a dataset of artesunate and dihydroartemisinin concentration-time profiles of 19 malaria patients. When all the discussed constraints were imposed on the model, the resulting globally identifiable model structure was found to fit reasonably well to those patients with normal drug absorption profiles. However, there is wide variability in the fitted parameters and further investigation is warranted.

Mechanism-based model of parasite growth and dihydroartemisinin pharmacodynamics in murine malaria

Murine models are used to study erythrocytic stages of malaria infection, because parasite morphology and development are comparable to those in human malaria infections. Mechanism-based pharmacokinetic-pharmacodynamic (PK-PD) models for antimalarials are scarce, despite their potential to optimize antimalarial combination therapy. The aim of this study was to develop a mechanism-based growth model (MBGM) for Plasmodium berghei and then characterize the parasiticidal effect of dihydroartemisinin (DHA) in murine malaria (MBGM-PK-PD). Stage-specific (ring, early trophozoite, late trophozoite, and schizont) parasite density data from Swiss mice inoculated with Plasmodium berghei were used for model development in S-ADAPT. A single dose of intraperitoneal DHA (10 to 100 mg/kg) or vehicle was administered 56 h postinoculation. The MBGM explicitly reflected all four erythrocytic stages of the 24-hour P. berghei life cycle. Merozoite invasion of erythrocytes was described by a first-order process that declined with increasing parasitemia. An efflux pathway with subsequent return was additionally required to describe the schizont data, thus representing parasite sequestration or trapping in the microvasculature, with a return to circulation. A 1-compartment model with zero-order absorption described the PK of DHA, with an estimated clearance and distribution volume of 1.95 liters h(-1) and 0.851 liter, respectively. Parasite killing was described by a turnover model, with DHA inhibiting the production of physiological intermediates (IC(50), 1.46 ng/ml). Overall, the MBGM-PK-PD described the rise in parasitemia, the nadir following DHA dosing, and subsequent parasite resurgence. This novel model is a promising tool for studying malaria infections, identifying the stage specificity of antimalarials, and providing insight into antimalarial treatment strategies.

Pharmacokinetics of oral artesunate in thai patients with uncomplicated falciparum malaria

The pharmacokinetics of artesunate and its major plasma metabolite, dihydroartemisinin, were investigated in 11 Thai male patients with acute uncomplicated falciparum malaria during the acute and recovery phases. Patients were given an oral dose of 200mg artesunate (Guilin Pharmaceutical) on the first day, followed by 100mg 12 hours later, then 100mg daily for another 4 days (total dose of 700mg). All the patients showed a rapid initial response with median (range) parasite and fever clearance times of 30 (18 to 60) and 24 (4 to 94) hours, respectively; no patients showed reappearance of parasites during the 28-day follow-up period. No significant clinical adverse effects were detected in any patient. Acute phase malaria infection significantly influenced the pharmacokinetics of artesunate and its active metabolite, dihydroartemisinin. Maximum plasma drug concentration (C(max)), absorption half-life (t((1/2)a)), area under the plasma concentration-time curve from zero to the last observed time (AUC) and terminal elimination half-life (t((1/2)z)) of artesunate were decreased, while apparent total body clearance (CL/f) was increased during the acute phase, compared with the recovery phase. In addition, a decrease in the C(max) and an increase in the AUC(DHA/ARS ) ratio were found. Optimisation of therapy with oral artesunate should therefore be based on the kinetics of the drug and dihydroartemisinin in malaria patients with acute phase infection.

Pharmacokinetic comparison of two piperaquine-containing artemisinin combination therapies in Papua New Guinean children with uncomplicated malaria

Pharmacokinetic differences between piperaquine (PQ) base and PQ tetraphosphate were investigated in 34 Papua New Guinean children aged 5 to 10 years treated for uncomplicated malaria with artemisinin-PQ (ART-PQ) base or dihydroartemisinin-PQ (DHA-PQ) tetraphosphate. Twelve children received ART-PQ base (two daily doses of 3 mg of ART and 18 mg of PQ base as granules/kg of body weight) as recommended by the manufacturer, with regular clinical assessment and blood sampling over 56 days. PQ concentrations in plasma samples collected from 22 children of similar ages with malaria in a previously published pharmacokinetic study of DHA-PQ tetraphosphate (three daily doses of 2.5 mg of ART and 20 mg of PQ tetraphosphate as tablets/kg of body weight) were available for comparison. The disposition of ART was also assessed in the 12 children who received ART-PQ base. Plasma PQ was assayed by high-performance liquid chromatography with UV detection, and ART was assayed using liquid chromatography-mass spectrometry. Multicompartment pharmacokinetic models for PQ and ART were developed using a population-based approach. ART-PQ base was well tolerated, and initial fever abatement and parasite clearance were prompt. There were no differences between the two treatments in the values for the PQ area under the concentration-time curve from time zero to infinity (AUC(0-∞)), with medians of 49,451 (n = 12) and 44,556 (n = 22) μg · h/liter for ART-PQ base and DHA-PQ tetraphosphate, respectively. Recurrent parasitemia was associated with lower PQ exposure. Using a two-compartment ART model, the median AUC(0-∞) was 1,652 μg · h/liter. There was evidence of autoinduction of ART metabolism (relative bioavailability for the second dose, 0.27). These and previously published data suggest that a 3-day ART-PQ base regimen should be further evaluated, in line with World Health Organization recommendations for all artemisinin combination therapies.

Artemisinin-naphthoquine combination therapy for uncomplicated pediatric malaria: a pharmacokinetic study

Artemisinin-naphthoquine (ART-NQ) is a coformulated antimalarial therapy marketed as a single-dose treatment in Papua New Guinea and other tropical countries. To build on limited knowledge of the pharmacokinetic properties of the components, especially the tetra-aminoquinoline NQ, we studied ART-NQ disposition in Papua New Guinea children aged 5 to 12 years with uncomplicated malaria, comparing a single dose (15 and 6 mg/kg of body weight) administered with water (group 1; n = 13), a single dose (22 and 9 mg/kg) with milk (group 2) (n = 17), and two daily doses of 22 and 9 mg/kg with water (group 3; n = 16). The plasma NQ concentration was assayed by high-performance liquid chromatography, and the plasma ART concentration was assayed using liquid chromatography-mass spectrometry. Population-based multicompartment pharmacokinetic models for NQ and ART were developed. NQ disposition was best characterized by a three-compartment model with a mean absorption half-life (t(1/2)) of 1.0 h and predicted median maximum plasma concentrations that ranged as high as 57 μg/liter after the second dose in group 3. The mean NQ elimination t(1/2) was 22.8 days; clearance relative to bioavailability (CL/F) was 1.1 liters/h/kg; and volume at steady state relative to bioavailability (V(ss)/F) was 710 liters/kg. Administration of NQ with fat (8.5 g; 615 kJ) versus water was associated with 25% increased bioavailability. ART disposition was best characterized by a two-compartment model with a mean CL/F (4.1 liters/h/kg) and V/F (21 liters/kg) similar to those of previous studies. There was a 77% reduction in the bioavailability of the second ART dose (group 3). NQ has pharmacokinetic properties that confirm its potential as an artemisinin partner drug for treatment of uncomplicated pediatric malaria.

Quantification of dihydroartemisinin, artesunate and artemisinin in human blood: overcoming the technical challenge of protecting the peroxide bridge

BACKGROUND

Quantification of artemisinin (ARN) and its derivatives in whole blood has hitherto been thought impossible.

RESULTS

A LC-MS/MS method for the analysis of artesunate (ARS), its metabolite dihydroartemisinin (DHA) and artemisinin in human whole blood has been developed and successfully validated. The method includes stabilization of the blood matrix at the time of collection and at the time of analysis. Addition of potassium dichromate to the blood samples deactivated the Fe(2+) core in hemoglobin, while deferoxamine chelated Fe(3+) and prevented back conversion into Fe(2+). A pilot study showed that the blood:plasma ratio for ARS and DHA is approximately 0.75, indicating a significantly lower uptake in red blood cells than had previously been estimated using radiolabeled drug methodology.

CONCLUSIONS

The developed LC-MS/MS assay is the first method available for quantification of ARN and its derivatives in blood and opens up new possibilities of studying these drugs inside infected red blood cells.

Monitoring of artemisinin, dihydroartemisinin, and artemether in environmental matrices using high-performance liquid chromatography-tandem mass spectrometry (LC-MS/MS)

The area cultivated with Artemisia annua for the extraction of the antimalarial compound artemisinin is increasing, but the environmental impact of this cultivation has not yet been studied. A sensitive and robust method using liquid chromatography-tandem mass spectrometry (LC-MS/MS) was developed for the determination of artemisinin in soil. Dihydroartemisinin and artemether were included in the method, and performance on analytical columns of both traditional C(18) phenyl-hexyl and porous shell particles-based Kinetex types was characterized. The versatility of the method was demonstrated on surface water and groundwater samples and plant extracts. The limit of detection was 55, 30 (25 ng/g soil), and 4 ng/mL for dihydroartemisinin, artemisinin, and artemether, respectively. Method performance was demonstrated using naturally contaminated soil samples from A. annua fields in Kenya. The highest observed concentrations were above EC(10) for lettuce growth. Monitoring of artemisinin in soil with A. annua crop production seems necessary to further understand the impact in the environment.

Population pharmacokinetics of artemether, lumefantrine, and their respective metabolites in Papua New Guinean children with uncomplicated malaria

There are sparse published data relating to the pharmacokinetic properties of artemether, lumefantrine, and their active metabolites in children, especially desbutyl-lumefantrine. We studied 13 Papua New Guinean children aged 5 to 10 years with uncomplicated malaria who received the six recommended doses of artemether (1.7 mg/kg of body weight) plus lumefantrine (10 mg/kg), given with fat over 3 days. Intensive blood sampling was carried out over 42 days. Plasma artemether, dihydroartemisinin, lumefantrine, and desbutyl-lumefantrine were assayed using liquid chromatography-mass spectrometry or high-performance liquid chromatography. Multicompartmental pharmacokinetic models for a drug plus its metabolite were developed using a population approach that included plasma artemether and dihydroartemisinin concentrations below the limit of quantitation. Although artemether bioavailability was variable and its clearance increased by 67.8% with each dose, the median areas under the plasma concentration-time curve from 0 h to infinity (AUC(0-∞)s) for artemether and dihydroartemisinin (3,063 and 2,839 μg · h/liter, respectively) were similar to those reported previously in adults with malaria. For lumefantrine, the median AUC(0-∞) (459,980 μg · h/liter) was also similar to that in adults with malaria. These data support the higher dose recommended for children weighing 15 to 35 kg (35% higher than that for a 50-kg adult) but question the recommendation for a lower dose in children weighing 12.5 to 15 kg. The median desbutyl-lumefantrine/lumefantrine ratio in the children in our study was 1.13%, within the range reported for adults and higher at later time points because of the longer desbutyl-lumefantrine terminal elimination half-life. A combined desbutyl-lumefantrine and lumefantrine AUC(0-∞) weighted on in vitro antimalarial activity was inversely associated with recurrent parasitemia, suggesting that both the parent drug and the metabolite contribute to the treatment outcome of artemether-lumefantrine.

Meningeal inflammation increases artemether concentrations in cerebrospinal fluid in Papua New Guinean children treated with intramuscular artemether

Although the artemisinin-associated neurotoxicity identified in vitro and in animal studies has not been confirmed clinically, only one adult study has measured cerebrospinal fluid (CSF) concentrations after administration of conventional doses. Potential artemisinin neurotoxicity could be serious in children, especially those with meningitis and, consequently, a compromised blood-brain barrier. We measured CSF/plasma artemether and dihydroartemisinin (DHA) concentrations in 32 Papua New Guinean children with a mean age of 39 months with suspected or proven severe falciparum malaria who underwent a single lumbar puncture after intramuscular artemether administration. CSF artemether concentrations were 0 to 43.5 μg/liter and CSF concentration/plasma concentration ratios were 0 to 38.1%. DHA was measurable in CSF in only two children. The seven children with meningeal inflammation (CSF white cell count > 20/mm(3)) had higher CSF artemether concentration/plasma artemether concentration ratios than those without (median, 6.7% [interquartile ratio, 2.5 to 27.8%]% versus 0.0% [interquartile ratio, 0.0 to 2.5%]; P = 0.002). Meningeal inflammation was associated with a 4.6-fold increase in the CSF artemether concentration/plasma artemether concentration ratio in a population pharmacokinetic model. These data suggest that pharmacovigilance should be heightened when intramuscular artemether is given to severely ill children with evidence of meningeal inflammation.

Pharmacokinetics and ex vivo antimalarial activity of artesunate-azithromycin in healthy volunteers

In 18 male healthy subjects, artesunate (200 mg)-azithromycin (1,500 mg) daily for 3 days was found to be well tolerated, with only mild gastrointestinal disturbances reported. The pharmacokinetic properties of artesunate-azithromycin given in combination are comparable to those of the drugs given alone. Artesunate and its major active metabolite, dihydroartemisinin, are responsible for most of the ex vivo antimalarial activity, with a delayed contribution by azithromycin.

A liquid chromatographic-tandem mass spectrometric method for determination of artemether and its metabolite dihydroartemisinin in human plasma

BACKGROUND

Artemether-lumefantrine is the most widely recommended artemisinin-based combination treatment for falciparum malaria. Quantification of artemether and its metabolite dihydroartemisinin in biological matrices has traditionally been difficult, with sensitivity being an issue.

RESULTS

A high-throughput bioanalytical method for the analysis of artemether and its metabolite dihydroartemisinin in human plasma using solid-phase extraction in the 96-well plate format and liquid chromatography coupled to positive ion mode tandem mass spectroscopy has been developed and validated according to US FDA guidelines. The method uses 50 µl plasma and covers the calibration range 1.43-500 ng/ml with a limit of detection at 0.36 ng/ml.

CONCLUSIONS

The developed liquid chromatography-tandem mass spectrometry assay is more sensitive than all previous methods despite using a lower plasma volume (50 µl) and is highly suitable for clinical studies where plasma volumes are limited, such as pediatric trials.

Stereodynamic investigation of labile stereogenic centres in dihydroartemisinin

Since its identification in the early 1970s, artemisinin, as well as semi-synthetic derivatives and synthetic trioxanes, have been used in malaria therapy. Reduction of artemisinin by NaBH4 produced dihydroartemisinin (DHA), and yielded a new stereochemically labile centre at C-10, which, in turn, provided two interconverting lactol hemiacetal epimers (namely alpha and beta), whose rate of interconversion depends on buffer, pH, and solvent polarity. Since interconversion of the two epimers occurred on a chromatographic time-scale, this prompted a thorough investigation of the phenomenon as a crucial requisite of any analytical method aimed at quantitating this family of drugs. In this critical review we discuss the current importance of the on-column epimerization of DHA in the development of analytical methods aimed at quantifying the drug, with the purpose of identifying the optimal conditions to minimize on-column epimerization while achieving the best selectivity and efficiency of the overall separation.

Anti-cancer effects of artesunate in a panel of chemoresistant neuroblastoma cell lines

Artemisinin derivatives are well-tolerated anti-malaria drugs that also exert anti-cancer activity. Here, we investigated artemisinin and its derivatives dihydroartemisinin and artesunate in a panel of chemosensitive and chemoresistant human neuroblastoma cells as well as in primary neuroblastoma cultures. Only dihydroartemisinin and artesunate affected neuroblastoma cell viability with artesunate being more active. Artesunate-induced apoptosis and reactive oxygen species in neuroblastoma cells. Of 16 cell lines and two primary cultures, only UKF-NB-3(r)CDDP(1000) showed low sensitivity to artesunate. Characteristic gene expression signatures based on a previous analysis of artesunate resistance in the NCI60 cell line panel clearly separated UKF-NB-3(r)CDDP(1000) from the other cell lines. l-Buthionine-S,R-sulfoximine, an inhibitor of GCL (glutamate-cysteine ligase), resensitised in part UKF-NB-3(r)CDDP(1000) cells to artesunate. This finding together with bioinformatic analysis of expression of genes involved in glutathione metabolism showed that this pathway is involved in artesunate resistance. These data indicate that neuroblastoma represents an artesunate-sensitive cancer entity and that artesunate is also effective in chemoresistant neuroblastoma cells.

The antiviral activities of artemisinin and artesunate

Traditional Chinese medicine commands a unique position among all traditional medicines because of its 5000 years of history. Our own interest in natural products from traditional Chinese medicine was triggered in the 1990s, by artemisinin-type sesquiterpene lactones from Artemisia annua L. As demonstrated in recent years, this class of compounds has activity against malaria, cancer cells, and schistosomiasis. Interestingly, the bioactivity of artemisinin and its semisynthetic derivative artesunate is even broader and includes the inhibition of certain viruses, such as human cytomegalovirus and other members of the Herpesviridae family (e.g., herpes simplex virus type 1 and Epstein-Barr virus), hepatitis B virus, hepatitis C virus, and bovine viral diarrhea virus. Analysis of the complete profile of the pharmacological activities and molecular modes of action of artemisinin and artesunate and their performance in clinical trials will further elucidate the full antimicrobial potential of these versatile pharmacological tools from nature.

Gene expression profiling identifies novel key players involved in the cytotoxic effect of Artesunate on pancreatic cancer cells

Pancreatic cancer is one of the most aggressive human malignancies, with an extremely poor prognosis. The paucity of curative therapies has translated into an overall 5-year survival rate of less than 5%, underscoring a desperate need for new therapeutic options. Artesunate (ART), clinically used as anti-malarial agent, has recently revealed remarkable anti-tumor activity. However, the mechanisms underlying those activities in pancreatic cancer are not yet known. Here we evaluated the anti-tumor activity of Artesunate and the possible underlying mechanisms in pancreatic cancer. MiaPaCa-2 (poorly differentiated) and BxPC-3 (moderately differentiated) pancreatic cancer cell lines were treated with Artesunate and the effect was monitored by a tetrazolium-based assay (MTS) for evaluating cell viability and by flow cytometry and caspase 3/7 activation for apoptosis evaluation. In addition cDNA arrays were used to identify differentially expressed genes. The microarray data were then validated by RT-PCR and Western blotting. Moreover, pathways associated with these expression changes were identified using the Ingenuity Pathway Analysis. The expression analysis identified a common set of genes that were regulated by Artesunate in pancreatic cancer. Our results provide the first in vitro evidence for the therapeutic utility of Artesunate in pancreatic cancer. Moreover, we identified Artesunate as a novel topoisomerase IIalpha inhibitor that inhibits pancreatic cancer growth through modulation of multiple signaling pathways. The present analysis is a starting point for the generation of hypotheses on candidate genes and for a more detailed dissection of the functional role of individual genes for the activity of Artesunate in tumor cells.