Artemether-Lumefantrine Pharmacokinetics and Clinical Response Are Minimally Altered in Pregnant Ugandan Women Treated for Uncomplicated Falciparum Malaria

Therapeutic efficacy of generic artemether-lumefantrine in the treatment of uncomplicated malaria in Ghana: assessing anti-malarial efficacy amidst pharmacogenetic variations

BACKGROUND

Despite efforts made to reduce morbidity and mortality associated with malaria, especially in sub-Saharan Africa, malaria continues to be a public health concern that requires innovative efforts to reach the WHO-set zero malaria agenda. Among the innovations is the use of artemisinin-based combination therapy (ACT) that is effective against Plasmodium falciparum. Generic artemether-lumefantrine (AL) is used to treat uncomplicated malaria after appropriate diagnosis. AL is metabolized by the cytochrome P450 family of enzymes, such as CYP2B6, CYP3A4 and CYP3A5, which can be under pharmacogenetic influence. Pharmacogenetics affecting AL metabolism, significantly influence the overall anti-malarial activity leading to variable therapeutic efficacy. This study focused on generic AL drugs used in malarial treatment as prescribed at health facilities and evaluated pharmacogenomic influences on their efficacy.

METHODS

Patients who have been diagnosed with malaria and confirmed through RDT and microscopy were recruited in this study. Blood samples were taken on days 1, 2, 3 and 7 for parasite count and blood levels of lumefantrine, artemisinin, desbutyl-lumefantrine (DBL), and dihydroartemisinin (DHA), the active metabolites of lumefantrine and artemether, respectively, were analysed using established methods. Pharmacogene variation analysis was undertaken using iPLEX microarray and PCR-RFLP.

RESULTS

A total of 52 patients completed the study. Median parasite density from day 1 to 7 ranged from 0-2666/μL of blood, with days 3 and 7 recording 0 parasite density. Highest median plasma concentration for lumefantrine and desbutyl lumefantrine, which are the long-acting components of artemisinin-based combinations, was 4123.75 ng/mL and 35.87 ng/mL, respectively. Day 7 plasma lumefantrine concentration across all generic ACT brands was ≥ 200 ng/mL which potentially accounted for the parasitaemia profile observed. Monomorphism was observed for CYP3A4 variants, while there were observed variations in CYP2B6 and CYP3A5 alleles. Among the CYP3A5 genotypes, significant differences in genotypes and plasma concentration for DBL were seen on day 3 between 1/*1 versus *1/*6 (p = 0.002), *1/*3 versus *1/*6 (p = 0.006) and *1/*7 versus *1/*6 (p = 0.008). Day 7 plasma DBL concentrations showed a significant difference between *1/*6 and *1/*3 (p = 0.026) expressors.

CONCLUSIONS

The study findings show that CYP2B6 and CYP3A5 pharmacogenetic variations may lead to higher plasma exposure of AL metabolites.

Optimizing Therapeutic Drug Monitoring in Pregnant Women: A Critical Literature Review

BACKGROUND

More than 90% of pregnant women take at least one drug during pregnancy. Drug dose adjustments during pregnancy are sometimes necessary due to various pregnancy-induced physiological alterations frequently associated with lower plasma concentrations. However, the clinical relevance or benefits of therapeutic drug monitoring (TDM) in pregnant women have not been specifically studied. Clinical pharmacokinetic studies in pregnant women are incredibly challenging for many reasons. Despite this, regulatory agencies have made efforts to encourage the inclusion of this population in clinical trials to achieve more information on the pharmacotherapy of pregnant women. This review aims to provide support for TDM recommendations and dose adjustments in pregnant women.

METHODS

The search was conducted after a predetermined strategy on PubMed and Scopus databases using the MeSH term "pregnancy" alongside other terms such as "Pregnancy and dose adjustment," "Pregnancy and therapeutic drug monitoring," "Pregnancy and PBPK," "Pregnancy and pharmacokinetics," and "Pregnancy and physiological changes."

RESULTS

The main information on TDM in pregnant women is available for antiepileptics, antipsychotics, antidepressants, antibiotics, antimalarials, and oncologic and immunosuppressive drugs.

CONCLUSIONS

More data are needed to support informed benefit-risk decision making for the administration of drugs to pregnant women. TDM and/or pharmacokinetic studies could ensure that pregnant women receive an adequate dosage of an active drug. Mechanistic modeling approaches potentially could increase our knowledge about the pharmacotherapy of this special population, and they could be used to better design dosage regimens.

Derivatives of Amaryllidaceae Alkaloid Ambelline as Selective Inhibitors of Hepatic Stage of Plasmodium berghei Infection In Vitro

The incidence rate of malaria and the ensuing mortality prompts the development of novel antimalarial drugs. In this work, the activity of twenty-eight Amaryllidaceae alkaloids (1-28) belonging to seven different structural types was assessed, as well as twenty semisynthetic derivatives of the β-crinane alkaloid ambelline (28a-28t) and eleven derivatives of the α-crinane alkaloid haemanthamine (29a-29k) against the hepatic stage of Plasmodium infection. Six of these derivatives (28h, 28m, 28n and 28r-28t) were newly synthesized and structurally identified. The most active compounds, 11-O-(3,5-dimethoxybenzoyl)ambelline (28m) and 11-O-(3,4,5-trimethoxybenzoyl)ambelline (28n), displayed IC₅₀ values in the nanomolar range of 48 and 47 nM, respectively. Strikingly, the derivatives of haemanthamine (29) with analogous substituents did not display any significant activity, even though their structures are quite similar. Interestingly, all active derivatives were strictly selective against the hepatic stage of infection, as they did not demonstrate any activity against the blood stage of Plasmodium infection. As the hepatic stage is a bottleneck of the plasmodial infection, liver-selective compounds can be considered crucial for further development of the malaria prophylactics.

The pharmacokinetic properties of artemether and lumefantrine in Malaysian patients with Plasmodium knowlesi malaria

AIMS

The aim of this study was to assess the pharmacokinetic properties of artemether, lumefantrine and their active metabolites in Plasmodium knowlesi malaria.

METHODS

Malaysian adults presenting with uncomplicated P. knowlesi infections received six doses of artemether (1.7 mg/kg) plus lumefantrine (10 mg/kg) over 3 days. Venous blood and dried blood spot (DBS) samples were taken at predetermined time-points over 28 days. Plasma and DBS artemether, dihydroartemisinin, lumefantrine and desbutyl-lumefantrine were measured using liquid chromatography-mass spectrometry. Multi-compartmental population pharmacokinetic models were developed using plasma with or without DBS drug concentrations.

RESULTS

Forty-one participants (mean age 45 years, 66% males) were recruited. Artemether-lumefantrine treatment was well tolerated and parasite clearance was prompt. Plasma and DBS lumefantrine concentrations were in close agreement and were used together in pharmacokinetic modelling, but only plasma concentrations of the other analytes were used because of poor correlation with DBS levels. The areas under the concentration-time curve (AUC_0-∞ ) for artemether, dihydroartemisinin and lumefantrine (medians 1626, 1881 and 625 098 μg.h/L, respectively) were similar to those reported in previous pharmacokinetic studies in adults and children. There was evidence of auto-induction of artemether metabolism (mean increase in clearance relative to bioavailability 25.2% for each subsequent dose). The lumefantrine terminal elimination half-life (median 9.5 days) was longer than reported in healthy volunteers and adults with falciparum malaria.

CONCLUSION

The disposition of artemether, dihydroartemisinin and lumefantrine in knowlesi malaria largely parallels that in other human malarias. DBS lumefantrine concentrations can be used in pharmacokinetic studies but DBS technology is currently unreliable for the other analytes.

Malaria PK/PD and the Role Pharmacometrics Can Play in the Global Health Arena: Malaria Treatment Regimens for Vulnerable Populations

Malaria is an infectious disease which disproportionately effects children and pregnant women. These vulnerable populations are often excluded from clinical trials resulting in one‐size‐fits‐all treatment regimens based on those established for a nonpregnant adult population. Pharmacokinetic/pharmacodynamic (PK/PD) models can be used to optimize dose selection as they define the drug exposure‐response relationship. Additionally, these models are able to identify patient characteristics that cause alterations in the expected PK/PD profiles and through simulations can recommend changes to dosing which compensate for the differences. In this review, we examine how PK/PD models have been applied to optimize antimalarial dosing recommendations for young children, including those who are malnourished, pregnant women, and individuals receiving concomitant therapies such as those for HIV treatment. The malaria field has had great success in utilizing PK/PD models as a foundation to update treatment guidelines and propose the next generation of dosing regimens to investigate in clinical trials. We propose how the malaria field can continue to use modeling to improve therapies by further integrating PK data into clinical studies and including data on drug resistance and host immunity in PK/PD models. Finally, we suggest that other disease areas can achieve similar success in applying pharmacometrics to improve outcomes by implementing three key principals.

Anti-Infective Dosing in Special Populations: Pregnancy

Substantial anatomical and physiological changes occur during pregnancy and labor, which impact on drug absorption, distribution, metabolism, and elimination. Reduced maternal concentrations may have a clinically important impact on the efficacy of anti-infectives for mother, fetus, and neonate, with potential dosing implications. However, there is a paucity of pregnancy-specific data examining this. Existing data on the pharmacokinetics of anti-infectives in pregnancy are summarized and evaluated, with emphasis on agents that are used in treatment of HIV, tuberculosis, malaria, and common bacterial infections. Limitations and challenges in achieving ideal study designs in pregnant populations are highlighted, and key quality considerations for the generation of the highest quality evidence are outlined. PubMed was searched for each chosen anti-infective. Pharmacokinetic studies which either compared pharmacokinetics from pregnant women against nonpregnant controls, or which assessed concentrations against a known minimum inhibitory concentration were included. Two independent reviewers extracted data from each study and appraised them using the 24-point ClinPK Checklist. The main finding was that there is a lack of published data for anti-infectives in pregnancy, despite their clinical importance. Of the studies identified, only those investigating cobicistat-boosted antiretroviral regimens firmly concluded that these should not be used in pregnancy. Most studies concluded either that further research was needed, or that there were significant pharmacokinetic differences between pregnant and nonpregnant participants which had uncertain clinical significance. Challenges in applying existing quality grading systems to these studies were noted, suggesting a development of a refined system for appraisal of pharmacokinetic studies in "special populations" may be warranted.

Effect of CYP3A5*3 genotypes on lumefantrine plasma concentrations among malaria-HIV-infected women

Aim: We aimed to assess the effect of a functional polymorphism of CYP3A5 on lumefantrine pharmacokinetics. Patients & methods: Sixty-nine women diagnosed with malaria received standard doses of artemether-lumefantrine. Concentration-time data for lumefantrine and genotyping data were obtained for each participant. Pharmacokinetic-genotype associative relationships were assessed using linear regressions, Mann-Whitney U-test or Kruskal-Wallis statistics. Results: Average age and weight (standard deviation) of the patients were 33 (6.8) years and 59.5 (11.6) kg, respectively. CYP3A5*3 genotype associated with the log-transformed maximum concentration with the median (interquartile range) values of 8279 (6516-13,420) and 6331 (4093-8631) ng/ml (p = 0.032) among the carriers and noncarriers of CYP3A5*3, respectively. Besides, the NR1I3 c.152-1089T>C genotypes had an associative trend with the lumefantrine area under the curve (AUC_0-96h) and clearance. Conclusion: CYP3A5*3 genetic variant is associated with a high maximum plasma concentration of lumefantrine. This warrants further investigations on the association between CYP3A5*3 gene variants, lumefantrine pharmacokinetics and electrophysiological effect.

Updated pharmacokinetic considerations for the use of antimalarial drugs in pregnant women

INTRODUCTION

The association between pregnancy and altered drug pharmacokinetic (PK) properties is acknowledged, as is its impact on drug plasma concentrations and thus therapeutic efficacy. However, there have been few robust PK studies of antimalarial use in pregnancy. Given that inadequate dosing for prevention or treatment of malaria in pregnancy can result in negative maternal/infant outcomes, along with the potential to select for parasite drug resistance, it is imperative that reliable pregnancy-specific dosing recommendations are established.

AREAS COVERED

PK studies of antimalarial drugs in pregnancy. The present review summarizes the efficacy and PK properties of WHO-recommended therapies used in pregnancy, with a focus on PK studies published since 2014.

EXPERT OPINION

Changes in antimalarial drug disposition in pregnancy are well described, yet pregnant women continue to receive treatment regimens optimized for non-pregnant adults. Contemporary in silico modeling has recently identified a series of alternative dosing regimens that are predicted to provide optimal therapeutic efficacy for pregnant women.

Efficacy and tolerability of artemisinin-based and quinine-based treatments for uncomplicated falciparum malaria in pregnancy: a systematic review and individual patient data meta-analysis

BACKGROUND

Malaria in pregnancy affects both the mother and the fetus. However, evidence supporting treatment guidelines for uncomplicated (including asymptomatic) falciparum malaria in pregnant women is scarce and assessed in varied ways. We did a systematic literature review and individual patient data (IPD) meta-analysis to compare the efficacy and tolerability of different artemisinin-based or quinine-based treatments for malaria in pregnant women.

METHODS

We did a systematic review of interventional or observational cohort studies assessing the efficacy of artemisinin-based or quinine-based treatments in pregnancy. Seven databases (MEDLINE, Embase, Global Health, Cochrane Library, Scopus, Web of Science, and Literatura Latino Americana em Ciencias da Saude) and two clinical trial registries (International Clinical Trials Registry Platform and ClinicalTrials.gov) were searched. The final search was done on April 26, 2019. Studies that assessed PCR-corrected treatment efficacy in pregnancy with follow-up of 28 days or more were included. Investigators of identified studies were invited to share data from individual patients. The outcomes assessed included PCR-corrected efficacy, PCR-uncorrected efficacy, parasite clearance, fever clearance, gametocyte development, and acute adverse events. One-stage IPD meta-analysis using Cox and logistic regression with random-effects was done to estimate the risk factors associated with PCR-corrected treatment failure, using artemether-lumefantrine as the reference. This study is registered with PROSPERO, CRD42018104013.

FINDINGS

Of the 30 studies assessed, 19 were included, representing 92% of patients in the literature (4968 of 5360 episodes). Risk of PCR-corrected treatment failure was higher for the quinine monotherapy (n=244, adjusted hazard ratio [aHR] 6·11, 95% CI 2·57-14·54, p<0·0001) but lower for artesunate-amodiaquine (n=840, 0·27, 95% 0·14-0·52, p<0·0001), artesunate-mefloquine (n=1028, 0·56, 95% 0·34-0·94, p=0·03), and dihydroartemisinin-piperaquine (n=872, 0·35, 95% CI 0·18-0·68, p=0·002) than artemether-lumefantrine (n=1278) after adjustment for baseline asexual parasitaemia and parity. The risk of gametocyte carriage on day 7 was higher after quinine-based therapy than artemisinin-based treatment (adjusted odds ratio [OR] 7·38, 95% CI 2·29-23·82).

INTERPRETATION

Efficacy and tolerability of artemisinin-based combination therapies (ACTs) in pregnant women are better than quinine. The lower efficacy of artemether-lumefantrine compared with other ACTs might require dose optimisation.

FUNDING

The Bill & Melinda Gates Foundation, ExxonMobil Foundation, and the University of Oxford Clarendon Fund.

Efavirenz-Based Antiretroviral Therapy Reduces Artemether-Lumefantrine Exposure for Malaria Treatment in HIV-Infected Pregnant Women

BACKGROUND

The choice of malaria treatment for HIV-infected pregnant women receiving efavirenz-based antiretroviral therapy must consider the potential impact of drug interactions on antimalarial exposure and clinical response. The aim of this study was to investigate the effects of efavirenz on artemether-lumefantrine (AL) because no studies have isolated the impact of efavirenz for HIV-infected pregnant women.

METHODS

A prospective clinical pharmacokinetic (PK) study compared HIV-infected, efavirenz-treated pregnant women with HIV-uninfected pregnant women in Tororo, Uganda. All women received the standard 6-dose AL treatment regimen for Plasmodium falciparum malaria with intensive PK samples collected over 21 days and 42-days of clinical follow-up. PK exposure parameters were calculated for artemether, its active metabolite dihydroartemisinin (DHA), and lumefantrine to determine the impact of efavirenz.

RESULTS

Nine HIV-infected and 30 HIV-uninfected pregnant women completed intensive PK evaluations. Relative to controls, concomitant efavirenz therapy lowered the 8-hour artemether concentration by 76% (P = 0.013), DHA peak concentration by 46% (P = 0.033), and day 7 and 14 lumefantrine concentration by 61% and 81% (P = 0.046 and 0.023), respectively. In addition, there were nonsignificant reductions in DHA area under the concentration-time curve0-8hr (35%, P = 0.057) and lumefantrine area under the concentration-time curve0-∞ (34%, P = 0.063) with efavirenz therapy.

CONCLUSIONS

Pregnant HIV-infected women receiving efavirenz-based antiretroviral therapy during malaria treatment with AL showed reduced exposure to both the artemisinin and lumefantrine. These data suggest that malaria and HIV coinfected pregnant women may require adjustments in AL dosage or treatment duration to achieve exposure comparable with HIV-uninfected pregnant women.

A Randomized Controlled Trial of Three- versus Five-Day Artemether-Lumefantrine Regimens for Treatment of Uncomplicated Plasmodium falciparum Malaria in Pregnancy in Africa

Artemether-lumefantrine antimalarial efficacy in pregnancy could be compromised by reduced drug exposure. Population-based simulations suggested that therapeutic efficacy would be improved if the treatment duration was increased.

Artemether-lumefantrine antimalarial efficacy in pregnancy could be compromised by reduced drug exposure. Population-based simulations suggested that therapeutic efficacy would be improved if the treatment duration was increased. We assessed the efficacy, tolerability, and pharmacokinetics of an extended 5-day regimen of artemether-lumefantrine compared to the standard 3-day treatment in 48 pregnant women and 48 nonpregnant women with uncomplicated falciparum malaria in an open-label, randomized clinical trial. Babies were assessed at birth and 1, 3, 6, and 12 months. Nonlinear mixed-effects modeling was used to characterize the plasma concentration-time profiles of artemether and lumefantrine and their metabolites. Both regimens were highly efficacious (100% PCR-corrected cure rates) and well tolerated. Babies followed up to 1 year had normal development. Parasite clearance half-lives were longer in pregnant women (median [range], 3.30 h [1.39 to 7.83 h]) than in nonpregnant women (2.43 h [1.05 to 6.00 h]) (P=0.005). Pregnant women had lower exposures to artemether and dihydroartemisinin than nonpregnant women, resulting in 1.2% decreased exposure for each additional week of gestational age. By term, these exposures were reduced by 48% compared to nonpregnant patients. The overall exposure to lumefantrine was improved with the extended regimen, with no significant differences in exposures to lumefantrine or desbutyl-lumefantrine between pregnant and nonpregnant women. The extended artemether-lumefantrine regimen was well tolerated and safe and increased the overall antimalarial drug exposure and so could be a promising treatment option in pregnancy in areas with lower rates of malaria transmission and/or emerging drug resistance. (This study has been registered at ClinicalTrials.gov under identifier NCT01916954.)

Usefulness of day 7 lumefantrine plasma concentration as a predictor of malaria treatment outcome in under-fives children treated with artemether-lumefantrine in Tanzania

Background

Day 7 plasma lumefantrine concentration is suggested as a predictor for malaria treatment outcomes and a cut-off of ≥ 200 ng/ml is associated with day 28 cure rate in the general population. However, day 7 lumefantrine plasma concentration can be affected by age, the extent of fever, baseline parasitaemia, and bodyweight. Therefore, this study assessed the usefulness of day 7 lumefantrine plasma concentration as a predictor of malaria treatment outcome in under-fives children treated with generic or innovator drug-containing artemether-lumefantrine (ALu) in Tanzania.

Methods

This study was nested in an equivalence prospective study that aimed at determining the effectiveness of a generic ALu (Artefan^®) in comparison with the innovator’s product (Coartem^®). Children with uncomplicated malaria aged 6–59 months were recruited and randomized to receive either generic or innovator’s product. Children were treated with ALu as per World Health Organization recommendations. The clinical and parasitological outcomes were assessed after 28 days of follow up. PCR was performed to distinguish recrudescence and re-infections among children with recurrent malaria. Analysis of day 7 lumefantrine plasma concentration was carried out using a high-performance liquid chromatographic method with UV detection.

Results

The PCR corrected cure rates were 98.7% for children treated with generic and 98.6% for those treated with the innovator product (p = 1.00). The geometric mean (± SD) of day 7 plasma lumefantrine concentration was 159.3 (± 2.4) ng/ml for the generic and 164 (± 2.5) ng/ml for the innovator groups, p = 0.87. Geometric mean (± SD) day 7 lumefantrine plasma concentration between cured and recurrent malaria was not statistically different in both treatment arms [158.5 (± 2.4) vs 100.0 (± 1.5) ng/ml, (p = 0.28) for generic arm and 158.5 (± 2.3) vs 251.2 (± 4.2) ng/ml, (p = 0.24) for innovator arm]. Nutritional status was found to be a determinant of recurrent malaria (adjusted hazardous ratio (95% confidence interval) = 3(1.1–8.2), p = 0.029.

Conclusion

Using the recommended cut-off point of ≥ 200 ng/ml, day 7 plasma lumefantrine concentration failed to predict malaria treatment outcome in children treated with ALu in Tanzania. Further studies are recommended to establish the day 7 plasma lumefantrine concentration cut-off point to predict malaria treatment outcome in children.

Comparison on simultaneous caillary and venous parasite density and genotyping results from children and adults with uncomplicated malaria: a prospective observational study in Uganda

BACKGROUND

Blood smear microscopy remains the gold-standard method to diagnose and quantify malaria parasite density. In addition, parasite genotyping of select loci is the most utilized method for distinguishing recrudescent and new infections and to determine the number of strains per sample. In research settings, blood may be obtained from capillary or venous compartments, and results from these matrices have been used interchangeably. Our aim was to compare quantitative results for parasite density and strain complexity from both compartments.

METHODS

In a prospective observational study, children and adults presenting with uncomplicated Plasmodium falciparum malaria, simultaneous capillary and venous blood smears and dried blood spots were collected over 42-days following treatment with artemether-lumefantrine. Blood smears were read by two microscopists, any discrepancies resolved by a third reader. Parasite DNA fingerprinting was conducted using six microsatellites. Bland Altman analysis and paired t-test/McNemar's test were used to assess the difference in density readings and measurements.

RESULTS

Two hundred twenty-three participants were included in the analysis (177 children (35 HIV-infected/142 HIV-uninfected), 21 HIV-uninfected pregnant women, and 25 HIV-uninfected non-pregnant adults). Parasite density measurements did not statistically differ between capillary and venous blood smears at the time of presentation, nor over the course of 42-day follow-up. Characterization of merozoite surface protein-2 (MSP-2) genetic polymorphism demonstrated a higher level of strain diversity at the time of presentation in venous samples, as compared with capillary specimens (p = 0.02). There was a high degree of variability in genotype-corrected outcomes when pairs of samples from each compartment were compared using MSP-2 alone, although the variability was reduced with the use of multiple markers.

CONCLUSIONS

Parasite density measurements do not statistically differ between capillary and venous compartments in all studied demographic groups at the time of presentation with malaria, or over the course of follow-up. More strains were detected by MSP-2 genotyping in venous samples than in capillary samples at the time of malaria diagnosis. The use of multiple polymorphic markers reduces the impact of variability in strain detection on genotype-corrected outcomes. This study confirms that both capillary and venous compartments can be used for sampling with confidence in the clinical research setting.

TRIAL REGISTRATION

The trial was registered at ClinicalTrials.gov under registration no. NCT01717885 .

Antimalarial drugs for treating and preventing malaria in pregnant and lactating women

INTRODUCTION

Malaria in pregnancy and postpartum cause maternal mortality and adverse fetal outcomes. Efficacious and safe antimalarials are needed to treat and prevent such serious consequences. However, because of the lack of evidence on fetal safety, quinine, an old and less efficacious drug has long been recommended for pregnant women. Uncertainty about safety in relation to breastfeeding leads to withholding of efficacious treatments postpartum or cessation of breastfeeding. Areas covered: A search identified literature on humans in three databases (MEDLINE, Embase and Global health) using pregnancy or lactation, and the names of antimalarial drugs as search terms. Adverse reactions to the mother, fetus or breastfed infant were summarized together with efficacies. Expert opinion: Artemisinins are more efficacious and well-tolerated than quinine in pregnancy. Furthermore, the risks of miscarriage, stillbirth or congenital abnormality were not higher in pregnancies exposed to artemisinin derivatives for treatment of malaria than in pregnancies exposed to quinine or in the comparable background population unexposed to any antimalarials, and this was true for treatment in any trimester. Assessment of safety and efficacy of antimalarials including dose optimization for pregnant women is incomplete. Resistance to sulfadoxine-pyrimethamine in Plasmodium falciparum and long unprotected intervals between intermittent treatment doses begs reconsideration of current preventative recommendations in pregnancy. Data remain limited on antimalarials during breastfeeding; while most first-line drugs appear safe, further research is needed.

Population Pharmacokinetics of Artemether, Dihydroartemisinin, and Lumefantrine in Rwandese Pregnant Women Treated for Uncomplicated Plasmodium falciparum Malaria

The artemisinin-based combination therapy artemether-lumefantrine is commonly used in pregnant malaria patients. However, the effect of pregnancy-related changes on exposure is unclear, and pregnancy has been associated with decreased efficacy in previous studies. This study aimed to characterize the population pharmacokinetics of artemether, its active metabolite dihydroartemisinin, and lumefantrine in 22 Rwandese pregnant women in their second (n = 11) or third (n = 11) trimester with uncomplicated Plasmodium falciparum malaria. These patients were enrolled from Rwamagana district hospital and received the standard fixed oral dose combination of 80 mg of artemether and 480 mg of lumefantrine twice daily for 3 days. Venous plasma concentrations were quantified for all three analytes using liquid chromatography coupled with tandem mass spectroscopy, and data were analyzed using nonlinear mixed-effects modeling. Lumefantrine pharmacokinetics was described by a flexible but highly variable absorption, with a mean absorption time of 4.04 h, followed by a biphasic disposition model. The median area under the concentration-time curve from 0 h to infinity (AUC_0-∞) for lumefantrine was 641 h · mg/liter. Model-based simulations indicated that 11.7% of the study population did not attain the target day 7 plasma concentration (280 ng/ml), a threshold associated with increased risk of recrudescence. The pharmacokinetics of artemether was time dependent, and the autoinduction of its clearance was described using an enzyme turnover model. The turnover half-life was predicted to be 30.4 h. The typical oral clearance, which started at 467 liters/h, increased 1.43-fold at the end of treatment. Simulations suggested that lumefantrine pharmacokinetic target attainment appeared to be reassuring in Rwandese pregnant women, particularly compared to target attainment in Southeast Asia. Larger cohorts will be required to confirm this finding.

Strong correlation of lumefantrine concentrations in capillary and venous plasma from malaria patients

Background

Lumefantrine is a long-acting antimalarial drug with an elimination half-life of over 3 days and protein binding of 99 percent. Correlation of lumefantrine concentrations from capillary plasma via fingerprick (C_c) versus venous plasma (C_v) remains to be defined.

Methods

Venous and capillary plasma samples were collected simultaneously from children, pregnant women, and non-pregnant adults at 2, 24, 120hr post last dose of a standard 3-day artemether-lumefantrine regimen they received for uncomplicated malaria. Some of the enrolled children and pregnant women were also HIV-infected. Samples were analyzed via liquid chromatography tandem mass spectrometry. Linear regression analysis was performed using the program Stata® SE12.1.

Results

In children, the linear regression equations for C_c vs C_v at 2, 24, and 120hr (day 7) post dose are [C_c] = 1.05*[C_v]+95.0 (n = 142, R² = 0.977), [C_c] = 0.995*[C_v]+56.7 (n = 147, R² = 0.990) and [C_c] = 0.958*[C_v]+18.6 (n = 139, R² = 0.994), respectively. For pregnant women, the equations are [C_c] = 1.04*[C_v]+68.1 (n = 43, R² = 0.990), [C_c] = 0.997*[C_v]+37.3 (n = 43, R² = 0.993) and [C_c] = 0.941*[C_v]+11.1 (n = 41, R² = 0.941), respectively. For non-pregnant adults, the equations are [C_c] = 1.05*[C_v]-117 (n = 32, R² = 0.958), [C_c] = 0.962*[C_v]+9.21 (n = 32, R² = 0.964) and [C_c] = 1.04*[C_v]-40.1 (n = 32, R² = 0.988), respectively. In summary, a linear relationship with a slope of ~1 was found for capillary and venous lumefantrine levels in children, pregnant women and non-pregnant adults at 2hr, 24hr and 120hr post last dose, representing absorption, distribution, and elimination phases.

Conclusions

Capillary and venous plasma concentration of lumefantrine can be used interchangeably at 1:1 ratio. Capillary sampling method via finger prick is a suitable alternative for sample collection in clinical studies.

Artemether-lumefantrine dosing for malaria treatment in young children and pregnant women: A pharmacokinetic-pharmacodynamic meta-analysis

BACKGROUND

The fixed dose combination of artemether-lumefantrine (AL) is the most widely used treatment for uncomplicated Plasmodium falciparum malaria. Relatively lower cure rates and lumefantrine levels have been reported in young children and in pregnant women during their second and third trimester. The aim of this study was to investigate the pharmacokinetic and pharmacodynamic properties of lumefantrine and the pharmacokinetic properties of its metabolite, desbutyl-lumefantrine, in order to inform optimal dosing regimens in all patient populations.

METHODS AND FINDINGS

A search in PubMed, Embase, ClinicalTrials.gov, Google Scholar, conference proceedings, and the WorldWide Antimalarial Resistance Network (WWARN) pharmacology database identified 31 relevant clinical studies published between 1 January 1990 and 31 December 2012, with 4,546 patients in whom lumefantrine concentrations were measured. Under the auspices of WWARN, relevant individual concentration-time data, clinical covariates, and outcome data from 4,122 patients were made available and pooled for the meta-analysis. The developed lumefantrine population pharmacokinetic model was used for dose optimisation through in silico simulations. Venous plasma lumefantrine concentrations 7 days after starting standard AL treatment were 24.2% and 13.4% lower in children weighing <15 kg and 15-25 kg, respectively, and 20.2% lower in pregnant women compared with non-pregnant adults. Lumefantrine exposure decreased with increasing pre-treatment parasitaemia, and the dose limitation on absorption of lumefantrine was substantial. Simulations using the lumefantrine pharmacokinetic model suggest that, in young children and pregnant women beyond the first trimester, lengthening the dose regimen (twice daily for 5 days) and, to a lesser extent, intensifying the frequency of dosing (3 times daily for 3 days) would be more efficacious than using higher individual doses in the current standard treatment regimen (twice daily for 3 days). The model was developed using venous plasma data from patients receiving intact tablets with fat, and evaluations of alternative dosing regimens were consequently only representative for venous plasma after administration of intact tablets with fat. The absence of artemether-dihydroartemisinin data limited the prediction of parasite killing rates and recrudescent infections. Thus, the suggested optimised dosing schedule was based on the pharmacokinetic endpoint of lumefantrine plasma exposure at day 7.

CONCLUSIONS

Our findings suggest that revised AL dosing regimens for young children and pregnant women would improve drug exposure but would require longer or more complex schedules. These dosing regimens should be evaluated in prospective clinical studies to determine whether they would improve cure rates, demonstrate adequate safety, and thereby prolong the useful therapeutic life of this valuable antimalarial treatment.

Updated CDC Recommendations for Using Artemether-Lumefantrine for the Treatment of Uncomplicated Malaria in Pregnant Women in the United States

Malaria infection during pregnancy is associated with an increased risk for maternal and fetal complications. In the United States, treatment options for uncomplicated, chloroquine-resistant Plasmodium falciparum and P. vivax malaria in pregnant women are limited to mefloquine or quinine plus clindamycin (1). However, limited availability of quinine and increasing resistance to mefloquine restrict these options. Strong evidence now demonstrates that artemether-lumefantrine (AL) (Coartem) is effective and safe in the treatment of malaria in pregnancy. The World Health Organization (WHO) has endorsed artemisinin-based combination therapies (ACTs), such as AL, for treatment of uncomplicated malaria during the second and third trimesters of pregnancy and is currently considering whether to add ACTs, including AL, as an option for malaria treatment during the first trimester (2,3). This policy note reviews the evidence and updates CDC recommendations to include AL as a treatment option for uncomplicated malaria during the second and third trimesters of pregnancy and during the first trimester of pregnancy when other treatment options are unavailable. These updated recommendations reflect current evidence and are consistent with WHO treatment guidelines.

Treatment of uncomplicated and severe malaria during pregnancy

Over the past 10 years, the available evidence on the treatment of malaria during pregnancy has increased substantially. Owing to their relative ease of use, good sensitivity and specificity, histidine rich protein 2 based rapid diagnostic tests are appropriate for symptomatic pregnant women; however, such tests are less appropriate for systematic screening because they will not detect an important proportion of infections among asymptomatic women. The effect of pregnancy on the pharmacokinetics of antimalarial drugs varies greatly between studies and class of antimalarial drugs, emphasising the need for prospective studies in pregnant and non-pregnant women. For the treatment of malaria during the first trimester, international guidelines are being reviewed by WHO. For the second and third trimester of pregnancy, results from several trials have confirmed that artemisinin-based combination treatments are safe and efficacious, although tolerability and efficacy might vary by treatment. It is now essential to translate such evidence into policies and clinical practice that benefit pregnant women in countries where malaria is endemic. Access to parasitological diagnosis or appropriate antimalarial treatment remains low in many countries and regions. Therefore, there is a pressing need for research to identify quality improvement interventions targeting pregnant women and health providers. In addition, efficient and practical systems for pharmacovigilance are needed to further expand knowledge on the safety of antimalarial drugs, particularly in the first trimester of pregnancy.

Methodology of assessment and reporting of safety in anti-malarial treatment efficacy studies of uncomplicated falciparum malaria in pregnancy: a systematic literature review

Background

Considering the uncertainty of safety of anti-malarial drugs in pregnancy, efficacy studies are one of the few sources of clinical safety data. Complete safety evaluation is not usually incorporated in efficacy studies due to financial and human resource constraints. This review reports the methods used for the assessment of safety of artemisinin-based and quinine-based treatments in efficacy studies in pregnancy.

Methods

Methodology of assessment and reporting of safety in efficacy studies of artemisinin-based and quinine-based treatment in pregnancy was reviewed using seven databases and two clinical trial registries. The protocol was registered to PROSPERO (CRD42017054808).

Results

Of 48 eligible efficacy studies the method of estimation of gestational age was reported in only 32 studies (67%, 32/48) and ultrasound was used in 18 studies (38%, 18/48). Seventeen studies (35%, 17/48) reported parity, 9 (19%, 9/48) reported gravidity and 13 (27%, 13/48) reported both. Thirty-eight studies (79%, 38/48) followed participants through to pregnancy outcome. Fetal loss was assessed in 34 studies (89%, 34/38), but the definition of miscarriage and stillbirth were defined only in 11 (32%, 11/34) and 7 (21%, 7/34) studies, respectively. Preterm birth was assessed in 26 studies (68%, 26/38) but was defined in 16 studies (62%, 16/26). Newborn weight was assessed in 30 studies (79%, 30/38) and length in 10 studies (26%, 10/38). Assessment of birth weight took gestational age into account in four studies (13%, 4/30). Congenital abnormalities were reported in 32 studies (84%, 32/38). Other common risk factors for adverse pregnancy outcomes were not well-reported.

Conclusion

Incomplete reporting and varied methodological assessment of pregnancy outcomes in anti-malarial drug efficacy studies limits comparison across studies. A standard list of minimal necessary parameters to assess and report the safety component of efficacy studies of anti-malarials in pregnancy is proposed.

Electronic supplementary material

The online version of this article (10.1186/s12936-017-2136-x) contains supplementary material, which is available to authorized users.

Systematic literature review and meta-analysis of the efficacy of artemisinin-based and quinine-based treatments for uncomplicated falciparum malaria in pregnancy: methodological challenges

Background

There is no agreed standard method to assess the efficacy of anti-malarials for uncomplicated falciparum in pregnancy despite an increased risk of adverse outcomes for the mother and the fetus. The aim of this review is to present the currently available evidence from both observational and interventional cohort studies on anti-malarial efficacy in pregnancy and summarize the variability of assessment and reporting found in the review process.

Methods

Efficacy methodology and assessment of artemisinin-based treatments (ABT) and quinine-based treatments (QBT) were reviewed systematically using seven databases and two clinical trial registries (protocol registration—PROSPERO: CRD42017054808). Pregnant women in all trimesters with parasitologically confirmed uncomplicated falciparum malaria were included irrespective of symptoms. This review attempted to re-calculate proportions of treatment success applying the same definition as the standard WHO methodology for non-pregnant populations. Aggregated data meta-analyses using data from randomized control trials (RCTs) comparing different treatments were performed by random effects model.

Results

A total of 48 eligible efficacy studies were identified including 7279 treated Plasmodium falciparum episodes. While polymerase chain reaction (PCR) was used in 24 studies for differentiating recurrence, the assessment and reporting of treatment efficacy was heterogeneous. When the same definition could be applied, PCR-corrected treatment failure of ≥ 10% at any time points was observed in 3/30 ABT and 3/7 QBT arms. Ten RCTs compared different combinations of ABT but there was a maximum of two published RCTs with PCR-corrected outcomes for each comparison. Five RCTs compared ABT and QBT. Overall, the risk of treatment failure was significantly lower in ABT than in QBT (risk ratio 0.22, 95% confidence interval 0.07–0.63), although the actual drug combinations and outcome endpoints were different. First trimester women were included in 12 studies none of which were RCTs of ABT.

Conclusions

Efficacy studies in pregnancy are not only limited in number but use varied methodological assessments. In five RCTs with comparable methodology, ABT resulted in higher efficacy than QBT in the second and third trimester of pregnancy. Individual patient data meta-analysis can include data from observational cohort studies and could overcome some of the limitations of the current assessment given the paucity of data in this vulnerable group.

Electronic supplementary material

The online version of this article (10.1186/s12936-017-2135-y) contains supplementary material, which is available to authorized users.

Pharmacokinetic considerations for use of artemisinin-based combination therapies against falciparum malaria in different ethnic populations

INTRODUCTION

Artemisinin-based combination therapy (ACT) is used extensively as first-line treatment for uncomplicated falciparum malaria. There has been no rigorous assessment of the potential for racial/ethnic differences in the pharmacokinetic properties of ACTs that might influence their efficacy. Areas covered: A comprehensive literature search was performed that identified 72 publications in which the geographical origin of the patients could be ascertained and the key pharmacokinetic parameters maximum drug concentration (C_max), area under the plasma concentration-time curve (AUC) and elimination half-life (t_½β) were available for one or more of the five WHO-recommended ACTs (artemether-lumefantrine, artesunate-amodiaquine, artesunate-mefloquine, dihydroartemisinin-piperaquine and artesunate-sulfadoxine-pyrimethamine). Comparisons of each of the three pharmacokinetic parameters of interest were made by drug (artemisinin derivative and long half-life partner), race/ethnicity (African, Asian, Caucasian, Melanesian, South American) and patient categories based on age and pregnancy status. Expert opinion: The review identified no evidence of a clinically significant influence of race/ethnicity on the pharmacokinetic properties of the nine component drugs in the five ACTs currently recommended by WHO for first-line treatment of uncomplicated falciparum malaria. This provides reassurance for health workers in malaria-endemic regions that ACTs can be given in recommended doses with the expectation of adequate blood concentrations regardless of race/ethnicity.

Treatment regimens for pregnant women with falciparum malaria

INTRODUCTION

With increasing parasite drug resistance, the WHO has updated treatment recommendations for falciparum malaria including in pregnancy. This review assesses the evidence for choice of treatment for pregnant women.

AREAS COVERED

Relevant studies, primarily those published since 2010, were identified from reference databases and were used to identify secondary data sources. Expert commentary: WHO recommends use of intravenous artesunate for severe malaria, quinine-clindamycin for uncomplicated malaria in first trimester, and artemisinin combination therapy for uncomplicated malaria in second/third trimesters. Because fear of adverse outcomes has often excluded pregnant women from conventional drug development, available data for novel therapies are usually based on preclinical studies and cases of inadvertent exposure. Changes in antimalarial drug disposition in pregnancy have been observed but are yet to be translated into specific treatment recommendations. Such targeted regimens may become important as parasite resistance demands that drug exposure is optimized.

Malaria prevalence, severity and treatment outcome in relation to day 7 lumefantrine plasma concentration in pregnant women

Background

Day 7 plasma concentrations of lumefantrine (LF) can serve as a marker to predict malaria treatment outcome in different study populations. Two main cut-off points (175 and 280 ng/ml) are used to indicate plasma concentrations of LF, below which treatment failure is anticipated. However, there is limited data on the cumulative risk of recurrent parasitaemia (RP) in relation to day 7 LF plasma concentrations in pregnant women. This study describes the prevalence, severity, factors influencing treatment outcome of malaria in pregnancy and day 7 LF plasma concentration therapeutic cut-off points that predicts treatment outcome in pregnant women.

Methods

This was a one-arm prospective cohort study whereby 89 pregnant women with uncomplicated Plasmodium falciparum malaria receiving artemether-lumefantrine (ALu) participated in pharmacokinetics and pharmacodynamics study. Blood samples were collected on days 0, 2, 7, 14, 21 and 28 for malaria parasite quantification. LF plasma concentrations were determined on day 7. The primary outcome measure was an adequate clinical and parasitological response (ACPR) after treatment with ALu.

Results

The prevalence of malaria in pregnant women was 8.1 % (95 % CI 6.85–9.35) of whom 3.4 % (95 % CI 1.49–8.51) had severe malaria. The overall PCR-uncorrected treatment failure rate was 11.7 % (95 % CI 0.54–13.46 %). Low baseline hemoglobin (<10 g/dl) and day 7 LF concentration <600 ng/ml were significant predictors of RP. The median day 7 LF concentration was significantly lower in pregnant women with RP (270 ng/ml) than those with ACPR (705 ng/ml) (p = 0.016). The relative risk of RP was 4.8 folds higher (p = 0.034) when cut-off of <280 ng/ml was compared to ≥280 ng/ml and 7.8-folds higher (p = 0.022) when cut-off of <600 ng/ml was compared to ≥600 ng/ml. The cut-off value of 175 ng/ml was not associated with the risk of RP (p = 0.399).

Conclusions

Pregnant women with day 7 LF concentration <600 ng/ml are at high risk of RP than those with ≥600 ng/ml. To achieve effective therapeutic outcome, higher day 7 venous plasma LF concentration ≥600 ng/ml is required for pregnant patients than the previously suggested cut-off value of 175 or 280 ng/ml for non-pregnant adult patients.