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      A Randomised Controlled Trial of Artemether-Lumefantrine Versus Artesunate for Uncomplicated Plasmodium falciparum Treatment in Pregnancy

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          Abstract

          Background

          To date no comparative trials have been done, to our knowledge, of fixed-dose artemisinin combination therapies (ACTs) for the treatment of Plasmodium falciparum malaria in pregnancy. Evidence on the safety and efficacy of ACTs in pregnancy is needed as these drugs are being used increasingly throughout the malaria-affected world. The objective of this study was to compare the efficacy, tolerability, and safety of artemether-lumefantrine, the most widely used fixed ACT, with 7 d artesunate monotherapy in the second and third trimesters of pregnancy.

          Methods and Findings

          An open-label randomised controlled trial comparing directly observed treatment with artemether-lumefantrine 3 d (AL) or artesunate monotherapy 7 d (AS7) was conducted in Karen women in the border area of northwestern Thailand who had uncomplicated P. falciparum malaria in the second and third trimesters of pregnancy. The primary endpoint was efficacy defined as the P. falciparum PCR-adjusted cure rates assessed at delivery or by day 42 if this occurred later than delivery, as estimated by Kaplan-Meier survival analysis. Infants were assessed at birth and followed until 1 y of life. Blood sampling was performed to characterise the pharmacokinetics of lumefantrine in pregnancy. Both regimens were very well tolerated. The cure rates (95% confidence interval) for the intention to treat (ITT) population were: AS7 89.2% (82.3%–96.1%) and AL 82.0% (74.8%–89.3%), p = 0.054 (ITT); and AS7 89.7% (82.6%–96.8%) and AL 81.2% (73.6%–88.8%), p = 0.031 (per-protocol population). One-third of the PCR-confirmed recrudescent cases occurred after 42 d of follow-up. Birth outcomes and infant (up to age 1 y) outcomes did not differ significantly between the two groups. The pharmacokinetic study indicated that low concentrations of artemether and lumefantrine were the main contributors to the poor efficacy of AL.

          Conclusion

          The current standard six-dose artemether-lumefantrine regimen was well tolerated and safe in pregnant Karen women with uncomplicated falciparum malaria, but efficacy was inferior to 7 d artesunate monotherapy and was unsatisfactory for general deployment in this geographic area. Reduced efficacy probably results from low drug concentrations in later pregnancy. A longer or more frequent AL dose regimen may be needed to treat pregnant women effectively and should now be evaluated. Parasitological endpoints in clinical trials of any antimalarial drug treatment in pregnancy should be extended to delivery or day 42 if it comes later.

          Trial Registration: Current Controlled Trials ISRCTN86353884

          Abstract

          Rose McGready and colleagues show that an artemether-lumefantrine regimen is well tolerated and safe in pregnant Karen women with uncomplicated falciparum malaria, but efficacy is inferior to artesunate, probably because of low drug concentrations in later pregnancy.

          Abstract

          Editors' Summary
          Background.

          Plasmodium falciparum, a mosquito-borne parasite that causes malaria, kills nearly one million people every year. Although most deaths occur among young children, malaria during pregnancy is also an important public-health problem. In areas where malaria transmission is high (stable transmission), women acquire a degree of immunity. Although less symptomatic than women who lack natural protection, their babies are often small and sickly because malaria-related anemia (lack of red blood cells) and parasites in the placenta limit the nutrients supplied to the baby before birth. By contrast, in areas where malaria transmission is low (unstable transmission or sporadic outbreaks), women have little immunity to P. falciparum. If these women become infected during pregnancy, “uncomplicated” malaria (fever, chills, and anemia) can rapidly progress to “severe” malaria (in which vital organs are damaged), which can be fatal to the mother and/or her unborn child unless prompt and effective treatment is given.

          Why Was This Study Done?

          Malaria parasites are now resistant to many of the older antimalarial drugs (for example, quinine). So, since 2006, the World Health Organization (WHO) has recommended that uncomplicated malaria during the second and third trimester of pregnancy is treated with short course (3 d) fixed-dose artemisinin combination therapy (ACT; quinine is still used in early pregnancy because it is not known whether ACT damages fetal development, which mainly occurs during the first 3 mo of pregnancy). Artemisinin derivatives are fast-acting antimalarial agents that are used in combination with another antimalarial drug to reduce the chances of P. falciparum becoming resistant to either drug. The most widely used fixed-dose ACT is artemether–lumefantrine (AL) but, although several trials have examined the safety and efficacy of this treatment in non-pregnant women, little is known about how well it works in pregnant women. In this study, the researchers compare the efficacy, tolerability, and safety of AL with a 7-d course of artesunate monotherapy (AS7; another artemisinin derivative) in the treatment of uncomplicated malaria in pregnancy in northwest Thailand, an area with unstable but highly drug resistant malaria transmission.

          What Did the Researchers Do and Find?

          The researchers enrolled 253 women with uncomplicated malaria during the second and third trimesters of pregnancy into their open-label trial (a trial in which the patients and their health-care workers know who is receiving which drug regimen). Half the women received each type of treatment. The trial's main outcome was the “PCR-adjusted cure rate” at delivery or 42 d after treatment if this occurred after delivery. This cure rate was assessed by examining blood smears for parasites and then using a technique called PCR to determine which cases of malaria were new infections (classified as treatment successes along with negative blood smears) and which were recurrences of an old infection (classified as treatment failures). The PCR-adjusted cure rates were 89.7% and 81.2% for AS7 and AL, respectively. Both treatments were well tolerated, few side effects were seen with either treatment, and infant health and development at birth and up to 1 y old were similar with both regimens. Finally, an analysis of blood samples taken 7 d after treatment with AL showed that blood levels of lumefantrine were below those previously associated with treatment failure in about a third of the women tested.

          What Do These Findings Mean?

          Although these findings indicate that the AL regimen is a well tolerated and safe treatment for uncomplicated malaria in pregnant women living in northwest Thailand, the efficacy of this treatment was lower than that of artesunate monotherapy. In fact, neither treatment reached the 90% cure rate recommended by WHO for ACTs and it is likely that cure rates in a more realistic situation (that is, not in a trial where efforts are made to make sure everyone completes their treatment) would be even lower. The findings also suggest that the reduced efficacy of the AL regimen in pregnant women compared to the efficacy previously seen in non-pregnant women may be caused by lower drug blood levels during pregnancy. Thus, a higher-dose AL regimen (or an alternative ACT) may be needed to successfully treat uncomplicated malaria during pregnancy.

          Additional Information.

          Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.0050253.

          Related collections

          Most cited references 48

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          Mefloquine resistance in Plasmodium falciparum and increased pfmdr1 gene copy number.

          The borders of Thailand harbour the world's most multidrug resistant Plasmodium falciparum parasites. In 1984 mefloquine was introduced as treatment for uncomplicated falciparum malaria, but substantial resistance developed within 6 years. A combination of artesunate with mefloquine now cures more than 95% of acute infections. For both treatment regimens, the underlying mechanisms of resistance are not known. The relation between polymorphisms in the P falciparum multidrug resistant gene 1 (pfmdr1) and the in-vitro and in-vivo responses to mefloquine were assessed in 618 samples from patients with falciparum malaria studied prospectively over 12 years. pfmdr1 copy number was assessed by a robust real-time PCR assay. Single nucleotide polymorphisms of pfmdr1, P falciparum chloroquine resistance transporter gene (pfcrt) and P falciparum Ca2+ ATPase gene (pfATP6) were assessed by PCR-restriction fragment length polymorphism. Increased copy number of pfmdr1 was the most important determinant of in-vitro and in-vivo resistance to mefloquine, and also to reduced artesunate sensitivity in vitro. In a Cox regression model with control for known confounders, increased pfmdr1 copy number was associated with an attributable hazard ratio (AHR) for treatment failure of 6.3 (95% CI 2.9-13.8, p<0.001) after mefloquine monotherapy and 5.4 (2.0-14.6, p=0.001) after artesunate-mefloquine therapy. Single nucleotide polymorphisms in pfmdr1 were associated with increased mefloquine susceptibility in vitro, but not in vivo. Amplification in pfmdr1 is the main cause of resistance to mefloquine in falciparum malaria. Multidrug resistant P falciparum malaria is common in southeast Asia, but difficult to identify and treat. Genes that encode parasite transport proteins maybe involved in export of drugs and so cause resistance. In this study we show that increase in copy number of pfmdr1, a gene encoding a parasite transport protein, is the best overall predictor of treatment failure with mefloquine. Increase in pfmdr1 copy number predicts failure even after chemotherapy with the highly effective combination of mefloquine and 3 days' artesunate. Monitoring of pfmdr1 copy number will be useful in epidemiological surveys of drug resistance in P falciparum, and potentially for predicting treatment failure in individual patients.
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            Molecular and pharmacological determinants of the therapeutic response to artemether-lumefantrine in multidrug-resistant Plasmodium falciparum malaria.

            Our study examined the relative contributions of host, pharmacokinetic, and parasitological factors in determining the therapeutic response to artemether-lumefantrine (AL). On the northwest border of Thailand, patients with uncomplicated Plasmodium falciparum malaria were enrolled in prospective studies of AL treatment (4- or 6-dose regimens) and followed up for 42 days. Plasma lumefantrine concentrations were measured by high performance liquid chromatography; malaria parasite pfmdr1 copy number was quantified using a real-time polymerase chain reaction assay (PCR), and in vitro drug susceptibility was tested. All treatments resulted in a rapid clinical response and were well tolerated. PCR-corrected failure rates at day 42 were 13% (95% confidence interval [CI], 9.6%-17%) for the 4-dose regimen and 3.2% (95% CI, 1.8%-4.6%) for the 6-dose regimen. Increased pfmdr1 copy number was associated with a 2-fold (95% CI, 1.8-2.4-fold) increase in lumefantrine inhibitory concentration(50) (P=.001) and an adjusted hazard ratio for risk of treatment failure following completion of a 4-dose regimen, but not a 6-dose regimen, of 4.0 (95% CI, 1.4-11; P=.008). Patients who had lumefantrine levels below 175 ng/mL on day 7 were more likely to experience recrudescence by day 42 (adjusted hazard ratio, 17; 95% CI, 5.5-53), allowing prediction of treatment failure with 75% sensitivity and 84% specificity. The 6-dose regimen ensured that therapeutic levels were achieved in 91% of treated patients. The lumefantrine plasma concentration profile is the main determinant of efficacy of artemether-lumefantrine. Amplification in pfmdr1 determines lumefantrine susceptibility and, therefore, treatment responses when plasma lumefantrine levels are subtherapeutic.
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              Clinical pharmacokinetics and pharmacodynamics and pharmacodynamics of artemether-lumefantrine.

              The combination of artemether and lumefantrine (benflumetol) is a new and very well tolerated oral antimalarial drug effective even against multidrug-resistant falciparum malaria. The artemether component is absorbed rapidly and biotransformed to dihydroartemisinin, and both are eliminated with terminal half-lives of around 1 hour. These are very active antimalarials which give a rapid reduction in parasite biomass and consequent rapid resolution of symptoms. The lumefantrine component is absorbed variably in malaria, and is eliminated more slowly (half-life of 3 to 6 days). Absorption is very dependent on coadministration with fat, and so improves markedly with recovery from malaria. Thus artemether clears most of the infection, and the lumefantrine concentrations that remain at the end of the 3- to 5-day treatment course are responsible for eliminating the residual 100 to 10 000 parasites. The area under the curve of plasma lumefantrine concentrations versus time, or its correlate the plasma concentration on day 7. has proved an important determinant of therapeutic response. Characterisation of these pharmacokinetic-pharmacodynamic relationships provided the basis for dosage optimisation, an approach that could be applied to other antimalarial drugs.
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                Author and article information

                Contributors
                Role: Academic Editor
                Journal
                PLoS Med
                pmed
                plme
                plosmed
                PLoS Medicine
                Public Library of Science (San Francisco, USA )
                1549-1277
                1549-1676
                December 2008
                23 December 2008
                : 5
                : 12
                Affiliations
                [1 ] Shoklo Malaria Research Unit (SMRU), Mae Sot, Tak, Thailand
                [2 ] Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
                [3 ] Centre for Clinical Vaccinology and Tropical Medicine, Churchill Hospital, Oxford, United Kingdom
                Royal Melbourne Hospital, Australia
                Author notes
                * To whom correspondence should be addressed. E-mail: rose@ 123456shoklo-unit.com
                Article
                08-PLME-RA-0186R3 plme-05-12-21
                10.1371/journal.pmed.0050253
                2605900
                19265453
                Copyright: © 2008 McGready et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
                Page count
                Pages: 17
                Categories
                Research Article
                Evidence-Based Healthcare
                Infectious Diseases
                Obstetrics
                Women's Health
                Malaria
                Obstetrics
                Pharmacology and Toxicology
                Custom metadata
                McGready R, Tan SO, Ashley EA, Pimanpanarak M, Viladpai-nguen J, et al. (2008) A randomised controlled trial of artemether-lumefantrine versus artesunate for uncomplicated Plasmodium falciparum treatment in pregnancy. PLoS Med 5(12): e253. doi: 10.1371/journal.pmed.0050253

                Medicine

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