Intermittent Preventive Treatment for Malaria in Pregnancy: Optimization of Target Concentrations of Dihydroartemisinin-Piperaquine

Drug-Drug Interaction Between Dihydroartemisinin-Piperaquine and Sulfadoxine-Pyrimethamine During Malaria Chemoprevention in Pregnant Women

Co-administration of dihydroartemisinin-piperaquine (DP) and sulfadoxine-pyrimethamine (SP) for intermittent preventive treatment of malaria in pregnancy (IPTp) may be superior in preventing adverse birth outcomes compared with either therapy alone, but potential drug-drug interactions require investigation. We conducted intensive and sparse pharmacokinetic (PK) studies in a subset of Ugandan women participating in a randomized controlled trial of monthly IPTp with SP vs. DP vs. DP + SP. Intensive PK sampling was performed from day 0 to 23 after dosing at 28 weeks gestation in 87 participants across treatment arms. Sparse sampling was performed on day 28 (trough) after dosing at 20 and 28 gestational weeks in additional 196 participants receiving SP vs. DP + SP. Intensive PK analysis demonstrated that compared with SP alone, co-administration of DP + SP was associated with lower maximal concentrations, the area under the concentration-time curves (AUC), and day 23 concentrations of sulfadoxine (25%, 25%, and 27%) and pyrimethamine (26%, 34%, and 32%) (P < 0.05 for all comparisons). Sparse PK results demonstrated participants co-administered DP + SP had lower trough concentrations after dosing at 20 and 28 gestational weeks for sulfadoxine (6%, P = 0.68 and 31%, P = 0.023, respectively) and pyrimethamine (18%, P = 0.032 and 33%, P < 0.001, respectively) compared with SP alone. Co-administration of DP + SP was associated with a 19% reduction in piperaquine AUC (P = 0.046), but no significant difference in other PK parameters compared with DP alone. In summary, co-administration of DP + SP was associated with significantly reduced SP exposure, with a greater magnitude during the third vs. second trimester. The clinical consequences of this interaction are yet unknown.

Dihydroartemisinin-Piperaquine Combination in the Treatment of Uncomplicated Plasmodium falciparum Malaria: Update on Clinical Failures in Africa and Tools for Surveillance

Dihydroartemisinin (or artenimol)-piperaquine is one of the six artemisinin-based combination therapies recommended in uncomplicated malaria treatment. However, artemisinin partial resistance has been reported in Cambodia, Laos, Vietnam, India, and, recently, in Africa. Polymorphisms in the Pfk13 gene have been described as molecular markers of artemisinin resistance and the amplification of the plasmepsine II/III (Pfpmp2/Pfpmp3) gene has been associated with piperaquine resistance. However, some therapeutic failures with this combination remain unexplained by strains' characterization. We provide an overview on the use of dihydroartemisinin-piperaquine in malaria treatment and discuss tools available to monitor its efficacy.

Evolution of Pfdhps and Pfdhfr mutations before and after adopting seasonal malaria chemoprevention in Nanoro, Burkina Faso

Seasonal Malaria Chemoprevention consisting of monthly administration of amodiaquine/sulfadoxine-pyrimethamine to children aged 3-59 months during the transmission season could promote SP-resistance. Mutations in dihydrofolate reductase (Pfdhfr) and dihydropteroate synthase (Pfdhps) genes were assessed before and after SMC adoption in Burkina Faso. A total of 769 dried blood spots were selected from studies conducted in Nanoro, Burkina Faso, between 2010 and 2020. Of those, 299 were pre-SMC (2010-2012) and 470 were post-SMC-samples. Pfdhps and Pfdhfr genes were PCR-amplified and sequenced. A systematic review/meta-analysis of published studies conducted in Burkina Faso (2009-2023) was additionally performed. In Nanoro, the prevalence of Pfdhfr triple mutations (CIRNI) rose from 43.6% pre-SMC to 89.4% post-SMC (p < 0.0001). There was no mutation in Pfdhfr 164 and Pfdhps 540; Pfdhps A437G mutation increased from 63.9% (2010-2012) to 84.7% (2020) (p < 0.0001). The VAGKGS haplotype was 2.8% (2020). Pfdhfr/Pfdhps quintuple mutant IRN-436A437G rose from 18.6% (2010-2012) to 58.3% (2020) (p < 0.0001). Meta-analysis results from Burkina Faso showed an increase in mutations at Pfdhfr N51I, C59R, S108N, and Pfdhps A437G after SMC adoption. Post-SMC, the pyrimethamine-resistance marker prevalence increased, while the sulfadoxine-resistance marker prevalence remained stable. Detection of emerging PfdhpsVAGKGS haplotypes in 2020 underscores the importance of continuous SP-resistance monitoring.

Pharmacokinetics of piperaquine and its association with intermittent malaria preventive therapy outcomes during pregnancy

BACKGROUND

Dihydroartemisinin-piperaquine (DHP) recently showed superior effectiveness over sulfadoxine-pyrimethamine for malaria intermittent preventive treatment in pregnancy (IPTp). We investigated day 7 piperaquine pharmacokinetics and its therapeutic efficacy in preventing malaria during pregnancy.

METHODS

Malaria-free (mRDT) pregnant women (n = 400) who received monthly IPTp-DHP were enrolled and followed till delivery. Day 7 Plasma piperaquine concentrations were determined after each IPTp dose using UPLC/MS/MS. IPTp outcomes (symptomatic malaria and parasitemia during pregnancy, placental malaria, and maternal malaria at delivery) were monitored. Linear mixed model and Cox regression were used to assess predictors of day 7 piperaquine concentration and treatment outcome, respectively.

RESULTS

The incidences of symptomatic malaria and parasitemia during pregnancy per 100 person-year at risk were 2 and 33, respectively. The prevalence of histopathologically confirmed placental malaria and maternal malaria at delivery were 3% and 9.8%, respectively. Repeated monthly IPTp-DHP resulted in significantly increased day 7 plasma piperaquine concentration (p < 0.001). Following the 1st, 2nd, and 3rd monthly IPTp-DHP doses, the proportions of women with day 7 piperaquine concentration below the therapeutic threshold (< 30 ng/mL) were 6.1%, 4.1% and 3.6%, respectively. Factors such as maternal age, body weight and trimester were not significant predictors of day 7 piperaquine concentration. However, having a low day 7 piperaquine plasma concentration (< 30 ng/mL) was significantly associated with a higher risk of parasitemia during pregnancy (p = 0.004).

CONCLUSION

Lower day 7 piperaquine plasma concentration is a risk factor for parasitemia during pregnancy. Single plasma sampling at day 7 can be used to monitor piperaquine effectiveness during IPTp-DHP.

TRIAL REGISTRATION

Registered 09/12/2016, PACTR201612001901313.

Chemoprevention for malaria with monthly intermittent preventive treatment with dihydroartemisinin-piperaquine in pregnant women living with HIV on daily co-trimoxazole in Kenya and Malawi: a randomised, double-blind, placebo-controlled trial

BACKGROUND

The efficacy of daily co-trimoxazole, an antifolate used for malaria chemoprevention in pregnant women living with HIV, is threatened by cross-resistance of Plasmodium falciparum to the antifolate sulfadoxine-pyrimethamine. We assessed whether addition of monthly dihydroartemisinin-piperaquine to daily co-trimoxazole is more effective at preventing malaria infection than monthly placebo plus daily co-trimoxazole in pregnant women living with HIV.

METHODS

We did an individually randomised, two-arm, placebo-controlled trial in areas with high-grade sulfadoxine-pyrimethamine resistance in Kenya and Malawi. Pregnant women living with HIV on dolutegravir-based combination antiretroviral therapy (cART) who had singleton pregnancies between 16 weeks' and 28 weeks' gestation were randomly assigned (1:1) by computer-generated block randomisation, stratified by site and HIV status (known positive vs newly diagnosed), to daily co-trimoxazole plus monthly dihydroartemisinin-piperaquine (three tablets of 40 mg dihydroartemisinin and 320 mg piperaquine given daily for 3 days) or daily co-trimoxazole plus monthly placebo. Daily co-trimoxazole consisted of one tablet of 160 mg sulfamethoxazole and 800 mg trimethoprim. The primary endpoint was the incidence of Plasmodium infection detected in the peripheral (maternal) or placental (maternal) blood or tissue by PCR, microscopy, rapid diagnostic test, or placental histology (active infection) from 2 weeks after the first dose of dihydroartemisinin-piperaquine or placebo to delivery. Log-binomial regression was used for binary outcomes, and Poisson regression for count outcomes. The primary analysis was by modified intention to treat, consisting of all randomised eligible participants with primary endpoint data. The safety analysis included all women who received at least one dose of study drug. All investigators, laboratory staff, data analysts, and participants were masked to treatment assignment. This trial is registered with ClinicalTrials.gov, NCT04158713.

FINDINGS

From Nov 11, 2019, to Aug 3, 2021, 904 women were enrolled and randomly assigned to co-trimoxazole plus dihydroartemisinin-piperaquine (n=448) or co-trimoxazole plus placebo (n=456), of whom 895 (99%) contributed to the primary analysis (co-trimoxazole plus dihydroartemisinin-piperaquine, n=443; co-trimoxazole plus placebo, n=452). The cumulative risk of any malaria infection during pregnancy or delivery was lower in the co-trimoxazole plus dihydroartemisinin-piperaquine group than in the co-trimoxazole plus placebo group (31 [7%] of 443 women vs 70 [15%] of 452 women, risk ratio 0·45, 95% CI 0·30-0·67; p=0·0001). The incidence of any malaria infection during pregnancy or delivery was 25·4 per 100 person-years in the co-trimoxazole plus dihydroartemisinin-piperaquine group versus 77·3 per 100 person-years in the co-trimoxazole plus placebo group (incidence rate ratio 0·32, 95% CI 0·22-0·47, p<0·0001). The number needed to treat to avert one malaria infection per pregnancy was 7 (95% CI 5-10). The incidence of serious adverse events was similar between groups in mothers (17·7 per 100 person-years in the co-trimoxazole plus dihydroartemisinin-piperaquine group [23 events] vs 17·8 per 100 person-years in the co-trimoxazole group [25 events]) and infants (45·4 per 100 person-years [23 events] vs 40·2 per 100 person-years [21 events]). Nausea within the first 4 days after the start of treatment was reported by 29 (7%) of 446 women in the co-trimoxazole plus dihydroartemisinin-piperaquine group versus 12 (3%) of 445 women in the co-trimoxazole plus placebo group. The risk of adverse pregnancy outcomes did not differ between groups.

INTERPRETATION

Addition of monthly intermittent preventive treatment with dihydroartemisinin-piperaquine to the standard of care with daily unsupervised co-trimoxazole in areas of high antifolate resistance substantially improves malaria chemoprevention in pregnant women living with HIV on dolutegravir-based cART and should be considered for policy.

FUNDING

European and Developing Countries Clinical Trials Partnership 2; UK Joint Global Health Trials Scheme (UK Foreign, Commonwealth and Development Office; Medical Research Council; National Institute for Health Research; Wellcome); and Swedish International Development Cooperation Agency.

Therapeutical Utilization and Repurposing of Artemisinin and Its Derivatives: A Narrative Review

Artemisinin (ART) and its derivatives have great therapeutical utility as antimalarials and can be repurposed for other indications, such as viral infections, autoimmune diseases, and cancer. This review presents a comprehensive overview of the therapeutic effects of ART-based drugs, beyond their antimalarial effects. This review also summarizes the information on their repurposing in other pathologies, with the hope that it will guide the future optimization of the use of ART-based drugs and of the treatment strategies for the listed diseases. By reviewing related literature, ART extraction and structure as well as the synthesis and structure of its derivatives are presented. Subsequently, the traditional roles of ART and its derivatives against malaria are reviewed, including antimalarial mechanism and occurrence of antimalarial resistance. Finally, the potential of ART and its derivatives to be repurposed for the treatment of other diseases are summarized. The great repurposing potential of ART and its derivatives may be useful for the control of emerging diseases with corresponding pathologies, and future research should be directed toward the synthesis of more effective derivatives or better combinations.

Efavirenz-Based Antiretroviral Therapy but Not Pregnancy Increased Unbound Piperaquine Exposure in Women during Malaria Chemoprevention

Dihydroartemisinin-piperaquine (DP) is highly effective for malaria chemoprevention during pregnancy, but the standard dosing of DP that is used for nonpregnant adults may not be optimal for pregnant women. We previously reported that the pharmacokinetic exposure of total piperaquine (PQ; both bound and unbound to plasma proteins) is reduced significantly in the context of pregnancy or efavirenz (EFV)-based antiretroviral therapy (ART). However, as PQ is >99% protein-bound, reduced protein binding during pregnancy may lead to an increase in the pharmacologically active unbound drug fraction (fu), relative to the total PQ. We investigated the impact of pregnancy and EFV use on the fu of PQ to inform the interpretation of pharmacokinetics. Plasma samples from 0 to 24 h after the third (final) DP dose were collected from pregnant women at 28 weeks gestation who were receiving or not receiving EFV-based ART as well as from women 34 to 54 weeks postpartum who were not receiving EFV-based ART, who served as controls. Unbound PQ was quantified via ultrafiltration and liquid chromatography-tandem mass spectrometry, with fu being calculated as PQunbound/PQtotal. The geometric mean fu did not differ between pregnant and postpartum women (P = 0.66), but it was 23% (P < 0.01) greater in pregnant women receiving EFV-based ART, compared to that in postpartum women who were not receiving EFV-based ART. The altered drug-protein binding, potentially due to the displacement of PQ from plasma proteins by EFV, resulted in only a 14% lower unbound PQ exposure (P = 0.13) in the presence of a 31% lower total PQ exposure (P < 0.01), as estimated by the area under the concentration time curve from 0 to 24 h post-last dose in pregnant women who were receiving EFV-based ART. The results suggest that the impact of pregnancy and EFV-based ART on the exposure and, in turn, the efficacy of PQ for malaria prevention may not be as significant as was suggested by the changes in the total PQ exposure. Further study during the terminal elimination phase (e.g., on day 28 post-dose) would help better characterize the unbound PQ exposure during the full dosing interval and, thus, the overall efficacy of PQ for malaria chemoprevention in this special population.

Dihydroartemisinin-piperaquine or sulphadoxine-pyrimethamine for the chemoprevention of malaria in children with sickle cell anaemia in eastern and southern Africa (CHEMCHA): a protocol for a multi-centre, two-arm, double-blind, randomised, placebo-controlled superiority trial

BACKGROUND

An estimated 300,000 babies are born with sickle cell anaemia (SCA) annually. Affected children have chronic ill health and suffer premature death. Febrile illnesses such as malaria commonly precipitate acute crises in children with SCA. Thus, chemoprophylaxis for malaria is an important preventive strategy, but current regimes are either sub-optimally effective (e.g. monthly sulphadoxine-pyrimethamine, SP) or difficult to adhere to (e.g. daily proguanil). We propose dihydroartemisinin-piperaquine (DP) as the agent with the most potential to be used across Africa.

METHODS

This will be a randomised, double-blind, parallel-group superiority trial of weekly single-day courses of DP compared to monthly single-day courses of SP in children with SCA. The study will be conducted in eastern (Uganda) and southern (Malawi) Africa using randomisation stratified by body weight and study centre. Participants will be randomised using an allocation of 1:1 to DP or SP. We will investigate the efficacy, safety, acceptability and uptake and cost-effectiveness of malaria chemoprevention with weekly courses of DP vs monthly SP in 548 to 824 children with SCA followed up for 12-18 months. We will also assess toxicity from cumulative DP dosing and the development of resistance. Participant recruitment commenced on 30 April 2021; follow-up is ongoing.

DISCUSSION

At the end of this study, findings will be used to inform regional health policy. This manuscript is prepared from protocol version 2.1 dated 1 January 2022.

TRIAL REGISTRATION

The trial was registered at ClinicalTrials.gov, NCT04844099 . Registered on 08 April 2021.

Interplay among malnutrition, chemoprevention, and the risk of malaria in young Ugandan children: Longitudinal pharmacodynamic and growth analysis

African children are at risk of malaria and malnutrition. We quantified relationships between malaria and malnutrition among young Ugandan children in a high malaria transmission region. Data were used from a randomized controlled trial where Ugandan HIV-unexposed (n = 393) and HIV-exposed (n = 186) children were randomized to receive no malaria chemoprevention, monthly sulfadoxine-pyrimethamine, daily trimethoprim-sulfamethoxazole, or monthly dihydroartemisinin-piperaquine (DP) from age 6-24 months, and then were followed off chemoprevention until age 36 months. Monthly height and weight, and time of incident malaria episodes were obtained; 89 children who received DP contributed piperaquine (PQ) concentrations. Malaria hazard was modeled using parametric survival analysis adjusted for repeated events, and height and weight were modeled using a Brody growth model. Among 579 children, stunting (height-for-age z-score [ZHA] < -2) was associated with a 17% increased malaria hazard (95% confidence interval [CI] 10-23%) compared with children with a ZHA of zero. DP was associated with a 35% lower malaria hazard (hazard ratio [HR] [95% CI], 0.65 [0.41-0.97]), compared to no chemoprevention. After accounting for PQ levels, stunted children who received DP had 2.1 times the hazard of malaria (HR [95% CI] 2.1 [1.6-3.0]) compared with children with a ZHA of zero who received DP. Each additional malaria episode was associated with a 0.4% reduced growth rate for height. Better dosing regimens are needed to optimize malaria prevention in malnourished populations, but, importantly, malaria chemoprevention may reduce the burden of malnutrition in early childhood.

Impact of Dolutegravir-Based Antiretroviral Therapy on Piperaquine Exposure following Dihydroartemisinin-Piperaquine Intermittent Preventive Treatment of Malaria in Pregnant Women Living with HIV

Dihydroartemisinin-piperaquine, an artemisinin-based combination therapy, has been identified as a promising agent for intermittent preventive treatment of malaria in pregnancy. However, in pregnant women living with HIV (PLWH), efavirenz-based antiretroviral therapy (ART) significantly reduces the plasma exposure of piperaquine. In an open-label, nonrandomized, fixed-sequence, pharmacokinetic study, we compared piperaquine plasma concentrations in 13 pregnant women during a 3-day treatment course of dihydroartemisinin-piperaquine when coadministered with efavirenz-based versus dolutegravir-based ART in the second or third trimester of pregnancy. Piperaquine concentrations were measured over a 28-day period, while on efavirenz-based ART and after switching to dolutegravir-based ART. Noncompartmental analysis was performed, and geometric mean ratios (GMRs) and 90% confidence intervals (CIs) were generated to compare piperaquine pharmacokinetic parameters between these two treatment periods. Compared with efavirenz-based ART, coadministration of dihydroartemisinin-piperaquine and dolutegravir-based ART resulted in a 57% higher overall piperaquine exposure (area under the concentration-time curve from 0 to 672 h [AUC_{0-672 h}]) (GMR, 1.57; 90% CI, 1.28 to 1.93). Piperaquine's day 7 concentrations were also 63% higher (GMR, 1.63; 90% CI, 1.29 to 2.11), while day 28 concentrations were nearly three times higher (GMR, 2.96; 90% CI, 2.25 to 4.07). However, the maximum piperaquine concentration (C_max) remained similar (GMR, 1.09; 90% CI, 0.79 to 1.49). Dihydroartemisinin-piperaquine was well tolerated, with no medication-related serious adverse events observed in this small study. Compared with efavirenz-based ART, a known inducer of piperaquine metabolism, dolutegravir-based ART resulted in increased overall piperaquine exposure with pharmacokinetic parameter values that were similar to those published previously for pregnant and nonpregnant women. Our findings suggest that the efficacy of dihydroartemisinin-piperaquine will be retained in pregnant women on dolutegravir. (The study was registered on PACTR.samrc.ac.za [PACTR201910580840196].).

Piperaquine-Induced QTc Prolongation Decreases With Repeated Monthly Dihydroartemisinin-Piperaquine Dosing in Pregnant Ugandan Women

BACKGROUND

Intermittent preventive treatment with monthly dihydroartemisinin-piperaquine (DHA-PQ) is highly effective at preventing both malaria during pregnancy and placental malaria. Piperaquine prolongs the corrected QT interval (QTc), and it is possible that repeated monthly dosing could lead to progressive QTc prolongation. Intensive characterization of the relationship between piperaquine concentration and QTc interval throughout pregnancy can inform effective, safe prevention guidelines.

METHODS

Data were collected from a randomized controlled trial, where pregnant Ugandan women received malaria chemoprevention with monthly DHA-PQ (120/960 mg DHA/PQ; n = 373) or sulfadoxine-pyrimethamine (SP; 1500/75 mg; n = 375) during the second and third trimesters of pregnancy. Monthly trough piperaquine samples were collected throughout pregnancy, and pre- and postdose electrocardiograms were recorded at 20, 28, and 36 weeks' gestation in each woman. The pharmacokinetics-QTc relationship for piperaquine and QTc for SP were assessed using nonlinear mixed-effects modeling.

RESULTS

A positive linear relationship between piperaquine concentration and Fridericia corrected QTc interval was identified. This relationship progressively decreased from a 4.42 to 3.28 to 2.13 millisecond increase per 100 ng/mL increase in piperaquine concentration at 20, 28, and 36 weeks' gestation, respectively. Furthermore, 61% (n = 183) of women had a smaller change in QTc at week 36 than week 20. Nine women given DHA-PQ had grade 3-4 cardiac adverse events. SP was not associated with any change in QTc.

CONCLUSIONS

Repeated DHA-PQ dosing did not result in increased risk of QTc prolongation and the postdose QTc intervals progressively decreased. Monthly dosing of DHA-PQ in pregnant women carries minimal risk of QTc prolongation.

CLINICAL TRIALS REGISTRATION

NCT02793622.

Piperaquine Pharmacokinetic and Pharmacodynamic Profiles in Healthy Volunteers of Papua New Guinea after Administration of Three-Monthly Doses of Dihydroartemisinin–Piperaquine

Mass drug administration (MDA) with monthly dihydroartemisinin-piperaquine (DHA-PQP) appears useful in malaria control and elimination strategies. Determining the relationship between consecutive piperaquine phosphate (PQP) exposure and its impact on QT interval prolongation is a key safety consideration for MDA campaigns.

Prevention of malaria in pregnancy: The threat of sulfadoxine-pyrimethamine resistance

Malaria infection in pregnancy can lead to adverse outcomes for both the pregnant person and fetus. The administration of intermittent preventative therapy (IPTp) with sulfadoxine-pyrimethamine (SP) during pregnancy (IPTp-SP) improves outcomes, including severe maternal anemia, placental malaria infection, and low infant birth weight. The WHO recommends IPTp-SP for pregnant individuals living in areas of moderate or high malaria transmission in Africa. The current regimen consists of two or more doses of SP starting as early as possible in the second trimester, at least 1 month apart. Unfortunately, rising Plasmodium falciparum SP resistance throughout Africa threatens to erode the benefits of SP. Recent studies have shown a decrease in IPTp-SP efficacy in areas with high SP resistance. Thus, there is an urgent need to identify new drug regimens that can be used for intermittent preventative therapy in pregnancy. In this review, we discuss recent data on P. falciparum SP resistance in Africa, the effect of resistance on IPTp-SP, and studies of alternative IPTp regimens. Finally, we present a framework for the ideal pharmacokinetic and pharmacodynamic properties for future IPTp regimens.

Identifying an optimal dihydroartemisinin-piperaquine dosing regimen for malaria prevention in young Ugandan children

Intermittent preventive treatment (IPT) with dihydroartemisinin-piperaquine (DP) is highly protective against malaria in children, but is not standard in malaria-endemic countries. Optimal DP dosing regimens will maximize efficacy and reduce toxicity and resistance selection. We analyze piperaquine (PPQ) concentrations (n = 4573), malaria incidence data (n = 326), and P. falciparum drug resistance markers from a trial of children randomized to IPT with DP every 12 weeks (n = 184) or every 4 weeks (n = 96) from 2 to 24 months of age (NCT02163447). We use nonlinear mixed effects modeling to establish malaria protective PPQ levels and risk factors for suboptimal protection. Compared to DP every 12 weeks, DP every 4 weeks is associated with 95% protective efficacy (95% CI: 84-99%). A PPQ level of 15.4 ng/mL reduces the malaria hazard by 95%. Malnutrition reduces PPQ exposure. In simulations, we show that DP every 4 weeks is optimal across a range of transmission intensities, and age-based dosing improves malaria protection in young or malnourished children.

Piperaquine Pharmacokinetics during Intermittent Preventive Treatment for Malaria in Pregnancy

Dihydroartemisinin-piperaquine (DP) is a long-acting artemisinin combination treatment that provides effective chemoprevention and has been proposed as an alternative antimalarial drug for intermittent preventive therapy in pregnancy (IPTp). Several pharmacokinetic studies have shown that dose adjustment may not be needed for the treatment of malaria in pregnancy with DP.

Dihydroartemisinin-piperaquine (DP) is a long-acting artemisinin combination treatment that provides effective chemoprevention and has been proposed as an alternative antimalarial drug for intermittent preventive therapy in pregnancy (IPTp). Several pharmacokinetic studies have shown that dose adjustment may not be needed for the treatment of malaria in pregnancy with DP. However, there are limited data on the optimal dosing for IPTp. This study aimed to evaluate the population pharmacokinetics of piperaquine given as IPTp in pregnant women. Pregnant women were enrolled in clinical trials conducted in Kenya and Indonesia and treated with standard 3-day courses of DP, administered in 4- to 8-week intervals from the second trimester until delivery. Pharmacokinetic blood samples were collected for piperaquine drug measurements before each treatment round, at the time of breakthrough symptomatic malaria, and at delivery. Piperaquine population pharmacokinetic properties were investigated using nonlinear mixed-effects modeling with a prior approach. In total, data from 366 Kenyan and 101 Indonesian women were analyzed. The pharmacokinetic properties of piperaquine were adequately described using a flexible transit absorption (n = 5) followed by a three-compartment disposition model. Gestational age did not affect the pharmacokinetic parameters of piperaquine. After three rounds of monthly IPTp, 9.45% (95% confidence interval [CI], 1.8 to 26.5%) of pregnant women had trough piperaquine concentrations below the suggested target concentration (10.3 ng/ml). Translational simulations suggest that providing the full treatment course of DP at monthly intervals provides sufficient protection to prevent malaria infection. Monthly administration of DP has the potential to offer optimal prevention of malaria during pregnancy. (This study has been registered at ClinicalTrials.gov under identifier NCT01669941 and in the ISRCTN under number ISRCTN34010937.)

Piperaquine Exposure Is Altered by Pregnancy, HIV, and Nutritional Status in Ugandan Women

Dihydroartemisinin-piperaquine (DHA-PQ) provides highly effective therapy and chemoprevention for malaria in pregnant African women. PQ concentrations of >10.3 ng/ml have been associated with reduced maternal parasitemia, placental malaria, and improved birth outcomes. We characterized the population pharmacokinetics (PK) of PQ in a post hoc analysis of human immunodeficiency virus (HIV)-infected and -uninfected pregnant women receiving DHA-PQ as chemoprevention every 4 or 8 weeks. The effects of covariates such as pregnancy, nutritional status (body mass index [BMI]), and efavirenz (EFV)-based antiretroviral therapy were investigated. PQ concentrations from two chemoprevention trials were pooled to create a population PK database from 274 women and 2,218 PK observations. A three-compartment model with an absorption lag best fit the data. Consistent with our prior intensive PK evaluation, pregnancy and EFV use resulted in a 72% and 61% increased PQ clearance, compared to postpartum and HIV-uninfected pregnant women, respectively. Low BMI at 28 weeks of gestation was associated with increased clearance (2% increase per unit decrease in BMI). Low-BMI women given DHA-PQ every 8 weeks had a higher prevalence of parasitemia, malaria infection, and placental malaria compared to women with higher BMIs. The reduced piperaquine exposure in women with low BMI as well as during EFV coadministration, compared to pregnant women with higher BMIs and not taking EFV, suggests that these populations could benefit from weekly instead of monthly dosing for prevention of malaria parasitemia. Simulations indicated that because of the BMI-clearance relationship, weight-based regimens would not improve protection compared to a 2,880 mg fixed-dose regimen when provided monthly. (The clinical trials described in this paper have been registered at ClinicalTrials.gov under identifiers NCT02163447 and NCT02282293.).

Placental Malaria

Purpose of Review

Placental malaria is the primary mechanism through which malaria in pregnancy causes adverse perinatal outcomes. This review summarizes recent work on the significance, pathogenesis, diagnosis, and prevention of placental malaria.

Recent Findings

Placental malaria, characterized by the accumulation of Plasmodium-infected red blood cells in the placental intervillous space, leads to adverse perinatal outcomes such as stillbirth, low birth weight, preterm birth, and small-for-gestational-age neonates. Placental inflammatory responses may be primary drivers of these complications. Associated factors contributing to adverse outcomes include maternal gravidity, timing of perinatal infection, and parasite burden.

Summary

Placental malaria is an important cause of adverse birth outcomes in endemic regions. The main strategy to combat this is intermittent preventative treatment in pregnancy; however, increasing drug resistance threatens the efficacy of this approach. There are studies dissecting the inflammatory response to placental malaria, alternative preventative treatments, and in developing a vaccine for placental malaria.

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.

Determination of piperaquine concentration in human plasma and the correlation of capillary versus venous plasma concentrations

Background

A considerable challenge in quantification of the antimalarial piperaquine in plasma is carryover of analyte signal between assays. Current intensive pharmacokinetic studies often rely on the merging of venous and capillary sampling. Drug levels in capillary plasma may be different from those in venous plasma, Thus, correlation between capillary and venous drug levels needs to be established.

Methods

Liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) was used to develop the method. Piperaquine was measured in 205 pairs of capillary and venous plasma samples collected simultaneously at ≥24hr post dose in children, pregnant women and non-pregnant women receiving dihydroartemisinin-piperaquine as malaria chemoprevention. Standard three-dose regimen over three days applied to all participants with three 40mg dihydroartemisinin/320mg PQ tablets per dose for adults and weight-based dose for children. Correlation analysis was performed using the program Stata® SE12.1. Linear regression models were built using concentrations or logarithm transformed concentrations and the final models were selected based on maximal coefficient of determination (R²) and visual check.

Results

An LC-MS/MS method was developed and validated, utilizing methanol as a protein precipitation agent, a Gemini C₁₈ column (50x2.0mm, 5μm) eluted with basic mobile phase solvents (ammonium hydroxide as the additive), and ESI⁺ as the ion source. This method had a calibration range of 10–1000 ng/mL and carryover was negligible. Correlation analysis revealed a linear relationship: C_cap = 1.04×C_ven+4.20 (R² = 0.832) without transformation of data, and lnC_cap = 1.01×lnC_ven+0.0125, (R² = 0.945) with natural logarithm transformation. The mean ratio (±SD) of C_cap/C_ven was 1.13±0.42, and median (IQR) was 1.08 (0.917, 1.33).

Conclusions

Capillary and venous plasma PQ measures are nearly identical overall, but not readily exchangeable due to large variation. Further correlation study accounting for disposition phases may be necessary.

A Randomized Open-Label Evaluation of the Antimalarial Prophylactic Efficacy of Azithromycin-Piperaquine versus Sulfadoxine-Pyrimethamine in Pregnant Papua New Guinean Women

Emerging malaria parasite sulfadoxine-pyrimethamine (SP) resistance has prompted assessment of alternatives for intermittent preventive treatment in pregnancy (IPTp). The objective was to evaluate the tolerability and prophylactic efficacy of azithromycin (AZ) plus piperaquine (PQ) in pregnant women in Papua New Guinea. The study was an open-label, randomized, parallel-group trial. A total of 122 women (median gestation, 26 weeks [range, 14 to 32 weeks]) were randomized 1:1 to three daily doses of 1 g AZ plus 960 mg PQ tetraphosphate or single-dose SP (4,500 mg sulfadoxine plus 225 mg pyrimethamine), based on computer-generated block randomization. Tolerability was assessed to day 7, and efficacy was assessed to day 42 (when participants were returned to usual care) and at delivery. Data for 119 participants (AZ-PQ, n = 61; SP, n = 58) were analyzed. Both regimens were well tolerated, but AZ-PQ was associated with more gastrointestinal side effects (31%) and dizziness (21%). Eight women (6.7%) were parasitemic at recruitment but all were aparasitemic by 72 h. There were no differences in blood smear positivity rates between AZ-PQ and SP up to day 42 (0% versus 5.2%; relative risk [RR], 0.14 [95% confidence interval [CI], 0.01 to 2.58] [P = 0.18]; absolute risk reduction [ARR], 5.2% [95% CI, -1.3 to 11.6%]) and at the time of delivery (0% versus 8.7%; RR, 0.11 [95% CI, 0.01 to 2.01] [P = 0.14]; ARR, 8.7% [95% CI, -0.2 to 17.6%]). Of 92 women who were monitored to parturition, 89 (97%) delivered healthy babies; there were 3 stillbirths (SP, n = 1; AZ-PQ, n = 2 [twins]). There was a higher live birth weight (mean ± standard deviation) in the AZ-PQ group (3.13 ± 0.42 versus 2.88 ± 0.55 kg [P = 0.016]; mean difference, 0.25 kg [95% CI, 0.02 to 0.48 kg]). AZ-PQ is a promising candidate for IPTp.

Reduced Exposure to Piperaquine, Compared to Adults, in Young Children Receiving Dihydroartemisinin-Piperaquine as Malaria Chemoprevention

Dihydroartemisinin (DHA)-piperaquine is being evaluated as intermittent preventive therapy for malaria, but dosing has not been optimized for children. We assessed exposure to DHA and piperaquine in Ugandan children at two ages during infancy. Intensive sampling was performed in 32 children at 32 weeks of age, 31 children at 104 weeks, and 30 female adult controls. Compared with adults, DHA area under the concentration-time curve (AUC_{0-8 hr} ) was 52% higher at 32 weeks and comparable at 104 weeks. Compared with adults, piperaquine AUC_{0-21 d} was 35% lower at 32 weeks and 53% lower at 104 weeks. Terminal piperaquine concentrations on days 7, 14, and 21 were lower in children compared with adults and lower at 104 compared with 32 weeks. Piperaquine exposure was lower in young children compared with adults, and lower at 104 compared with 32 weeks of age, suggesting a need for age-based DHA-piperaquine dose optimization for chemoprevention.

Modeling Prevention of Malaria and Selection of Drug Resistance with Different Dosing Schedules of Dihydroartemisinin-Piperaquine Preventive Therapy during Pregnancy in Uganda

Dihydroartemisinin-piperaquine (DHA-PQ) is under study for intermittent preventive treatment during pregnancy (IPTp), but it may accelerate selection for drug resistance. Understanding the relationships between piperaquine concentration, prevention of parasitemia, and selection for decreased drug sensitivity can inform control policies and optimization of DHA-PQ dosing. Piperaquine concentrations, measures of parasitemia, and Plasmodium falciparum genotypes associated with decreased aminoquinoline sensitivity in Africa (pfmdr1 86Y, pfcrt 76T) were obtained from pregnant Ugandan women randomized to IPTp with sulfadoxine-pyrimethamine (SP) or DHA-PQ. Joint pharmacokinetic/pharmacodynamic models described relationships between piperaquine concentration and the probability of genotypes of interest using nonlinear mixed effects modeling. An increase in the piperaquine plasma concentration was associated with a log-linear decrease in risk of parasitemia. Our models predicted that higher median piperaquine concentrations would be required to provide 99% protection against mutant infections than against wild-type infections (pfmdr1: N86, 9.6 ng/ml; 86Y, 19.6 ng/ml; pfcrt: K76, 6.5 ng/ml; 76T, 19.6 ng/ml). Comparing monthly, weekly, and daily dosing, daily low-dose DHA-PQ was predicted to result in the fewest infections and the fewest mutant infections per 1,000 pregnancies (predicted mutant infections for pfmdr1 86Y: SP monthly, 607; DHA-PQ monthly, 198; DHA-PQ daily, 1; for pfcrt 76T: SP monthly, 1,564; DHA-PQ monthly, 283; DHA-PQ daily, 1). Our models predict that higher piperaquine concentrations are needed to prevent infections with the pfmdr1/pfcrt mutant compared to those with wild-type parasites and that, despite selection for mutants by DHA-PQ, the overall burden of mutant infections is lower for IPTp with DHA-PQ than for IPTp with SP. (This study has been registered at ClinicalTrials.gov under identifier NCT02282293.).

Pharmacotherapy for the prevention of malaria in pregnant women: currently available drugs and challenges

INTRODUCTION

Malaria in pregnancy continues to be a significant public health burden globally, with over 100 million women at risk each year. Sulfadoxine-pyrimethamine (SP) is the only antimalarial recommended for intermittent preventive therapy in pregnancy (IPTp) but increasing parasite resistance threatens its viability. There are few other available antimalarial therapies that currently have sufficient evidence of tolerability, safety, and efficacy to replace SP.

AREAS COVERED

Novel antimalarial combinations are under investigation for potential use as chemoprophylaxis and in IPTp regimens. The present review summarizes currently available therapies, emerging candidate combination therapies, and the potential challenges to integrating these into mainstream policy.

EXPERT OPINION

Alternative drugs or combination therapies to SP for IPTp are desperately required. Dihydroartemisinin-piperaquine and azithromycin-based combinations are showing great promise as potential candidates for IPTp but pharmacokinetic data suggest that dose modification may be required to ensure adequate prophylactic efficacy. If a suitable candidate regimen is not identified in the near future, the success of chemopreventive strategies such as IPTp may be in jeopardy.