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1.  Effect of High-Dose or Split-Dose Artesunate on Parasite Clearance in Artemisinin-Resistant Falciparum Malaria 
New treatment strategies are needed for artemisinin-resistant falciparum malaria. This randomized trial shows that neither increasing nor splitting the standard once-daily artesunate dose reverses the markedly reduced parasite clearance rate in patients with artemisinin-resistant falciparum malaria.
Background. The emergence of Plasmodium falciparum resistance to artemisinins on the Cambodian and Myanmar-Thai borders poses severe threats to malaria control. We investigated whether increasing or splitting the dose of the short-half-life drug artesunate improves parasite clearance in falciparum malaria in the 2 regions.
Methods. In Pailin, western Cambodia (from 2008 to 2010), and Wang Pha, northwestern Thailand (2009–2010), patients with uncomplicated falciparum malaria were randomized to oral artesunate 6 mg/kg/d as a once-daily or twice-daily dose for 7 days, or artesunate 8 mg/kg/d as a once-daily or twice-daily dose for 3 days, followed by mefloquine. Parasite clearance and recrudescence for up to 63 days of follow-up were assessed.
Results. A total of 159 patients were enrolled. Overall median (interquartile range [IQR]) parasitemia half-life (half-life) was 6.03 (4.89–7.28) hours in Pailin versus 3.42 (2.20–4.85) hours in Wang Pha (P = .0001). Splitting or increasing the artesunate dose did not shorten half-life in either site. Pharmacokinetic profiles of artesunate and dihydroartemisinin were similar between sites and did not correlate with half-life. Recrudescent infections occurred in 4 of 79 patients in Pailin and 5 of 80 in Wang Pha and was not different between treatment arms (P = .68).
Conclusions. Increasing the artesunate treatment dose up to 8 mg/kg/d or splitting the dose does not improve parasite clearance in either artemisinin resistant or more sensitive infections with P. falciparum.
Clinical Trials Registration. ISRCTN15351875.
doi:10.1093/cid/cis958
PMCID: PMC3563392  PMID: 23175556
artemisinins; drug resistance; Plasmodium falciparum; neutropenia; reticulocytopenia
2.  A Randomised Controlled Trial of Artemether-Lumefantrine Versus Artesunate for Uncomplicated Plasmodium falciparum Treatment in Pregnancy 
PLoS Medicine  2008;5(12):e253.
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
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.
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.
The MedlinePlus encyclopedia contains a page on malaria (in English and Spanish)
Information is available from the World Health Organization on malaria (in several languages), and their 2006 Guidelines for the Treatment of Malaria includes specific recommendations for the treatment of pregnant women
The US Centers for Disease Control and Prevention provide information on malaria and on malaria during pregnancy (in English and Spanish)
Information is available from the Roll Back Malaria Partnership on malaria during pregnancy, on artemisinin-based combination therapies, and on malaria in Thailand
doi:10.1371/journal.pmed.0050253
PMCID: PMC2605900  PMID: 19265453
3.  Artemisinin-resistant Plasmodium falciparum in Pursat province, western Cambodia: a parasite clearance rate study 
The Lancet infectious diseases  2012;12(11):851-858.
Summary
Background
Artemisinin-resistant Plasmodium falciparum has been reported in Pailin, western Cambodia, detected as a slow parasite clearance rate in vivo. Emergence of this phenotype in western Thailand and possibly elsewhere threatens to compromise the effectiveness of all artemisinin-based combination therapies. Parasite genetics is associated with parasite clearance rate but does not account for all variation. We investigated contributions of both parasite genetics and host factors to the artemisinin-resistance phenotype in Pursat, western Cambodia.
Methods
Between June 19 and Nov 28, 2009, and June 26 and Dec 6, 2010, we enrolled patients aged 10 years or older with uncomplicated falciparum malaria, a density of asexual parasites of at least 10 000 per μL of whole blood, no symptoms or signs of severe malaria, no other cause of febrile illness, and no chronic illness. We gave participants 4 mg/kg artesunate at 0, 24, and 48 h, 15 mg/kg mefloquine at 72 h, and 10 mg/kg mefloquine at 96 h. We assessed parasite density on thick blood films every 6 h until undetectable. The parasite clearance half-life was calculated from the parasite clearance curve. We genotyped parasites with 18 microsatellite markers and patients for haemoglobin E, α-thalassaemia, and a mutation of G6PD, which encodes glucose-6-phosphate dehydrogenase. To account for the possible effects of acquired immunity on half-life, we used three surrogates for increased likelihood of exposure to P falciparum: age, sex, and place of residence. This study is registered with ClinicalTrials.gov, number NCT00341003.
Findings
We assessed 3504 individuals from all six districts of Pursat province seeking treatment for malaria symptoms. We enrolled 168 patients with falciparum malaria who met inclusion criteria. The geometric mean half-life was 5.85 h (95% CI 5.54–6.18) in Pursat, similar to that reported in Pailin (p=0.109). We identified two genetically different parasite clone groups: parasite group 1 (PG1) and parasite group 2 (PG2). Non-significant increases in parasite clearance half-life were seen in patients with haemoglobin E (0.55 h; p=0.078), those of male sex (0.96 h; p=0.064), and in 2010 (0.68 h; p=0.068); PG1 was associated with a significant increase (0.79 h; p=0.033). The mean parasite heritability of half-life was 0.40 (SD 0.17).
Interpretation
Heritable artemisinin resistance is established in a second Cambodian province. To accurately identify parasites that are intrinsically susceptible or resistant to artemisinins, future studies should explore the effect of erythrocyte polymorphisms and specific immune responses on half-life variation.
Funding
Division of Intramural Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health.
doi:10.1016/S1473-3099(12)70181-0
PMCID: PMC3786328  PMID: 22940027
4.  Malaria Burden and Artemisinin Resistance in the Mobile and Migrant Population on the Thai–Myanmar Border, 1999–2011: An Observational Study 
PLoS Medicine  2013;10(3):e1001398.
Francois Nosten and colleagues evaluate malaria prevalence and incidence in the mobile population on the Myanmar side of the border with Thailand between 1999 and 2011, and also assess resistance to artemisinin.
Background
The Shoklo Malaria Research Unit has been working on the Thai–Myanmar border for 25 y providing early diagnosis and treatment (EDT) of malaria. Transmission of Plasmodium falciparum has declined, but resistance to artesunate has emerged. We expanded malaria activities through EDT and evaluated the impact over a 12-y period.
Methods and Findings
Between 1 October 1999 and 30 September 2011, the Shoklo Malaria Research Unit increased the number of cross-border (Myanmar side) health facilities from two to 11 and recorded the number of malaria consultations. Changes in malaria incidence were estimated from a cohort of pregnant women, and prevalence from cross-sectional surveys. In vivo and in vitro antimalarial drug efficacy were monitored. Over this period, the number of malaria cases detected increased initially, but then declined rapidly. In children under 5 y, the percentage of consultations due to malaria declined from 78% (95% CI 76–80) (1,048/1,344 consultations) to 7% (95% CI 6.2–7.1) (767/11,542 consultations), p<0.001. The ratio of P. falciparum/P. vivax declined from 1.4 (95% CI 1.3–1.4) to 0.7 (95% CI 0.7–0.8). The case fatality rate was low (39/75,126; 0.05% [95% CI 0.04–0.07]). The incidence of malaria declined from 1.1 to 0.1 episodes per pregnant women-year. The cumulative proportion of P. falciparum decreased significantly from 24.3% (95% CI 21.0–28.0) (143/588 pregnant women) to 3.4% (95% CI 2.8–4.3) (76/2,207 pregnant women), p<0.001. The in vivo efficacy of mefloquine-artesunate declined steadily, with a sharp drop in 2011 (day-42 PCR-adjusted cure rate 42% [95% CI 20–62]). The proportion of patients still slide positive for malaria at day 3 rose from 0% in 2000 to reach 28% (95% CI 13–45) (8/29 patients) in 2011.
Conclusions
Despite the emergence of resistance to artesunate in P. falciparum, the strategy of EDT with artemisinin-based combination treatments has been associated with a reduction in malaria in the migrant population living on the Thai–Myanmar border. Although limited by its observational nature, this study provides useful data on malaria burden in a strategically crucial geographical area. Alternative fixed combination treatments are needed urgently to replace the failing first-line regimen of mefloquine and artesunate.
Please see later in the article for the Editors' Summary
Editors' Summary
Background
According to latest figures, the World Health Organization estimates that there are over 200 million cases of malaria each year, with over three-quarters of a million deaths. Several Plasmodium parasites cause malaria (the most serious being Plasmodium falciparum) and are transmitted to people through the bites of infected night-flying mosquitoes. Malaria transmission can be prevented by using insecticides to control the mosquitoes and by sleeping under insecticide-treated bed nets. However, in Southeast Asia the effectiveness of these measures is limited. Treating infected people with antimalarial drugs, particularly with artemisinin-based combination treatments (ACTs), is a key strategy in reducing the deaths and disability caused by malaria. However, progress is now threatened by the emergence in Southeast Asia of P. falciparum isolates that are resistant to artesunate (a common component of ACT). This development is concerning, as resistance to the artemisinin family of drugs, of which artesunate is a member, could trigger a resurgence in malaria in many parts of the world and compromise the progress made in the treatment of severe malaria.
Why Was This Study Done?
P. falciparum resistance to artemisinin has been confirmed in the area around the border between Thailand and Myanmar. Malaria control in this border area is particularly challenging, as there is a reservoir of malaria in Myanmar (where the disease burden is higher than in Thailand), frequent population movement, and differences in adequate control measures on the two sides of the border. In this study the authors evaluated malaria prevalence and incidence in the mobile population on the Myanmar side of the border between 1 October 1999 and 30 September 2011 to assess whether increasing access to early diagnosis and treatment with ACT was associated with a decline in the malaria burden.
What Did the Researchers Do and Find?
The Shoklo Malaria Research Unit (SMRU) has been working on the Thai–Myanmar border for 25 years providing early diagnosis and treatment of malaria and has extended its services from two to 11 health care facilities (health posts) on the Myanmar side of the border over the past few years. In order to evaluate any changes in the malaria burden since the expansion of services, the researchers recorded the number of consultations in all SMRU clinics and health posts with confirmed malaria diagnosis and tracked changes in the prevalence of malaria in the population on the Myanmar side of the border (via cross-sectional surveys in villages). The researchers also assessed the incidence of malaria in a cohort of pregnant women living on both sides of the border and monitored antimalarial drug efficacy over this time period.
The researchers found that although the mobile population on the Thai side of the border remained constant, the population in villages covered by the clinics and health posts in the border area increased four-fold. Over the time period, the researchers found that the number of confirmed malaria cases (P. falciparum) increased initially, rising from just over 5,000 in 2000 to a peak of 13,764 in 2006, and then declined to just over 3,500 in 2011. A striking finding was the predominance of infections in young adult males (50,316/90,321; 55.7%). Encouragingly, the percentage of consultations due to malaria in children under five years fell from 78% to 7%, and the incidence of malaria declined from 1.1 to 0.1 episodes per pregnant woman-year. In addition, the proportion of patients admitted to hospital with severe disease was stable, and the number of deaths from malaria remained extremely low, with an overall case fatality rate of 0.05%. The researchers also found that the ratio of P. falciparum to P. vivax infections declined from 1.4 to 0.7, and the prevalence of P. falciparum decreased from 24.3% to 3.4%. However, worryingly, in the small number of patients undertaking drug efficacy tests, the drug efficacy of artesunate declined steadily, with the proportion of patients still infected with malaria at day 3 of treatment increasing from 0% in 2000 to 28% in 2011.
What Do These Findings Mean?
These findings indicate that despite the emergence of resistance to artesunate in P. falciparum, and the decline in the efficacy of ACT, the strategy of early diagnosis and treatment with ACTs has been associated with a reduction in malaria in the population living on the Thai–Myanmar border. Furthermore, these findings suggest that an aggressive strategy based on early detection and treatment of cases, combined with vector control and information, could be the way forward to eliminate malaria. Although there were only a small number of patients involved in drug efficacy tests in 2011, this study shows that alternative fixed combination treatments are needed urgently to replace the failing first-line regimen of mefloquine and artesunate.
Additional Information
Please access these websites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.1001398.
More information about the Shoklo Malaria Research Unit is available
The World Health Organization website has more information about antimalarial drug efficacy and drug resistance
The Bill & Melinda Gates Foundation website tells the malaria resistance story
doi:10.1371/journal.pmed.1001398
PMCID: PMC3589269  PMID: 23472056
5.  A Collaborative Epidemiological Investigation into the Criminal Fake Artesunate Trade in South East Asia  
PLoS Medicine  2008;5(2):e32.
Background
Since 1998 the serious public health problem in South East Asia of counterfeit artesunate, containing no or subtherapeutic amounts of the active antimalarial ingredient, has led to deaths from untreated malaria, reduced confidence in this vital drug, large economic losses for the legitimate manufacturers, and concerns that artemisinin resistance might be engendered.
Methods and Findings
With evidence of a deteriorating situation, a group of police, criminal analysts, chemists, palynologists, and health workers collaborated to determine the source of these counterfeits under the auspices of the International Criminal Police Organization (INTERPOL) and the Western Pacific World Health Organization Regional Office. A total of 391 samples of genuine and counterfeit artesunate collected in Vietnam (75), Cambodia (48), Lao PDR (115), Myanmar (Burma) (137) and the Thai/Myanmar border (16), were available for analysis. Sixteen different fake hologram types were identified. High-performance liquid chromatography and/or mass spectrometry confirmed that all specimens thought to be counterfeit (195/391, 49.9%) on the basis of packaging contained no or small quantities of artesunate (up to 12 mg per tablet as opposed to ∼ 50 mg per genuine tablet). Chemical analysis demonstrated a wide diversity of wrong active ingredients, including banned pharmaceuticals, such as metamizole, and safrole, a carcinogen, and raw material for manufacture of methylenedioxymethamphetamine (‘ecstasy'). Evidence from chemical, mineralogical, biological, and packaging analysis suggested that at least some of the counterfeits were manufactured in southeast People's Republic of China. This evidence prompted the Chinese Government to act quickly against the criminal traders with arrests and seizures.
Conclusions
An international multi-disciplinary group obtained evidence that some of the counterfeit artesunate was manufactured in China, and this prompted a criminal investigation. International cross-disciplinary collaborations may be appropriate in the investigation of other serious counterfeit medicine public health problems elsewhere, but strengthening of international collaborations and forensic and drug regulatory authority capacity will be required.
Paul Newton and colleagues' international, collaborative study found evidence that counterfeit artesunate was being manufactured in China, which prompted a criminal investigation.
Editors' Summary
Background
Malaria is one of the world's largest public health problems, causing around 500 million cases of illness and at least one million deaths per year (the estimates vary widely). The most serious form of malaria is caused by the parasite Plasmodium falciparum, which has become resistant to multiple drugs that had previously been the cornerstones of antimalarial regimens. One group of drugs for treating malaria, the artemisinin therapies including artesunate, are based upon a Chinese herb called qinghaosu; these have now become vital to the treatment of P. falciparum malaria. But counterfeit artesunate, containing none or too little (“subtherapeutic levels”) of the active ingredient, is a growing problem especially in South and East Asia. Fake artesunate is devastating for malaria control: it causes avoidable death, reduces confidence in the drug, and takes away profit from legitimate manufacturers. Of major concern also is the potential for subtherapeutic counterfeit artesunate to fuel the parasite's resistance to the artemisinin group of drugs.
Previous estimates have suggested that between 33% and 53% of artesunate tablets in mainland South East Asia are counterfeit. In this paper the authors report on an unprecedented international collaboration and criminal investigation that attempted to quantify and source counterfeit artesunate among some of the most malarious countries in Asia.
Why Was This Study Done?
Previous reports have identified the problem of fake artesunate, but as of yet there have been few reports on the potential solutions. Concerned health workers and scientists, the regional World Health Organization (WHO) office and the International Criminal Police Organization (INTERPOL) got together to discuss what could be done in May 2005 when it became clear the counterfeit artesunate situation was worsening in the Greater Mekong Sub-Region of South East Asia (comprising Cambodia, Lao People's Democratic Republic, Myanmar, Thailand, Vietnam, and Yunnan Province in the People's Republic of China). Their subsequent investigation combined the goals and methods of a range of concerned parties—police, scientists, and health workers—to identify the source of counterfeit artesunate in South East Asia and to supply the evidence to help arrest and prosecute the perpetrators.
What Did the Researchers Do and Find?
The researchers conducted forensic analyses of samples of genuine and counterfeit artesunate. They selected these samples from larger surveys and investigations that had been conducted in the region beginning in the year 2000. Genuine samples were supplied by a manufacturer to provide a comparator. The authors examined the physical appearance of the packages and subjected the tablets to a wide range of chemical and biological tests that allowed an analysis of the components contained in the tablets.
When comparing the collected packages and tablets against the genuine samples, the researchers found considerable diversity of fake artesunate in SE Asia. Sixteen different fake hologram types (the stickers contained on packages meant to identify them as genuine) were found. Chemical analysis revealed that all tablets thought to be fake contained no or very small quantities of artesunate. Other ingredients found in the artesunate counterfeit tablets included paracetamol, antibiotics, older antimalarial drugs, and a range of minerals, and there were a variety of gases surrounding the tablets inside the packaging. Biological analyses of pollen grains inside the packaging suggested that the packages originated in the parts of South East Asia along the Chinese border.
What Do these Findings Mean?
The results were crucial in helping the authorities establish the origin of the fake artesunate. For example, the authors identified two regional clusters where the counterfeit tablets appeared to be coming from, thus flagging a potential manufacturing site or distribution network. The presence of wrong active pharmaceutical ingredients (such as the older antimalarial drugs) suggested the counterfeiters had access to a variety of active pharmaceutical ingredients. The presence of safrole, a precursor to the illicit drug ecstasy, suggested the counterfeits may be coming from factories that manufacture ecstasy. And the identification of minerals indigenous to certain regions also helped identify the counterfeits' origin. The researchers concluded that at least some of the counterfeit artesunate was coming from southern China. The Secretary General of INTERPOL presented the findings to the Chinese government, which then carried out a criminal investigation and arrested individuals alleged to have produced and distributed the counterfeit artesunate.
The collaboration between police, public health workers and scientists on combating fake artesunate is unique, and provides a model for others to follow. However, the authors note that substantial capacity in forensic analysis and the infrastructure to support collaborations between these different disciplines are needed.
Additional Information.
Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.0050032.
The World Health Organization in 2006 created IMPACT—International Medical Products Anti-Counterfeiting Taskforce—with the aim of forging international collaboration to seek global solutions to this global challenge and in raising awareness of the dangers of counterfeit medical products. The task force membership includes international organizations, nongovernmental organizations, enforcement agencies, pharmaceutical manufacturers' associations, and drug and regulatory authorities. IMPACT's Web site notes that trade in counterfeit medicines is widespread and affects both developed and developing countries but is more prevalent in countries that have weak drug regulatory systems, poor supply of basic medicines, unregulated markets, high drug prices and/or significant price differentials. IMPACT holds international conferences and maintains a rapid alert system for counterfeit drugs.
The drug industry's anticounterfeit organization, Pharmaceutical Security Institute, works to develop improved systems to identify the extent of the counterfeiting problem and to assist in coordinating international inquiries. Its membership includes 21 large pharmaceutical companies.
The Web site of David Pizzanelli, a world expert on security holography, contains a PowerPoint presentation co-authored by Paul Newton that illustrates the different types of fake holograms found on fake artesunate packages, and their implications for artemisinin resistance (http://www.pizzanelli.co.uk/content/artesunate.html).
doi:10.1371/journal.pmed.0050032
PMCID: PMC2235893  PMID: 18271620
6.  Effectiveness of five artemisinin combination regimens with or without primaquine in uncomplicated falciparum malaria: an open-label randomised trial 
The Lancet Infectious Diseases  2010;10(10):673-681.
Summary
Background
Artemisinin-combination therapy (ACT) is recommended as first-line treatment of falciparum malaria throughout the world, and fixed-dose combinations are preferred by WHO; whether a single gametocytocidal dose of primaquine should be added is unknown. We aimed to compare effectiveness of four fixed-dose ACTs and a loose tablet combination of artesunate and mefloquine, and assess the addition of a single gametocytocidal dose of primaquine.
Methods
In an open-label randomised trial in clinics in Rakhine state, Kachin state, and Shan state in Myanmar (Burma) between Dec 30, 2008, and March 20, 2009, we compared the effectiveness of all four WHO-recommended fixed-dose ACTs (artesunate–mefloquine, artesunate–amodiaquine, dihydroartemisinin–piperaquine, artemether–lumefantrine) and loose artesunate–mefloquine in Burmese adults and children. Eligible patients were those who presented to the clinics with acute uncomplicated Plasmodium falciparum malaria or mixed infection, who were older than 6 months, and who weighed more than 5 kg. Treatments were randomised in equal numbers within blocks of 50 and allocation was in sealed envelopes. All patients were also randomly assigned to receive either a single dose of primaquine 0·75 mg base/kg or not. Patients were followed up for 63 days. Treatment groups were compared by analysis of variance and multiple logistic regression. The primary outcome was the 63 day recrudescence rate. This study is registered with clinicaltrials.gov, number NCT00902811.
Findings
155 patients received artesunate–amodiaquine, 162 artemether–lumefantrine, 169 artesunate–mefloquine, 161 loose artesunate–mefloquine, and 161 dihydroartemisinin–piperaquine. By day 63 of follow-up, 14 patients (9·4%; 95% CI 5·7–15·3%) on artesunate–amodiaquine had recrudescent P falciparum infections, a rate significantly higher than for artemether–lumefantrine (two patients; 1·4%; 0·3–5·3; p=0·0013), fixed-dose artesunate–mefloquine (0 patients; 0–2·3; p<0·0001), loose artesunate–mefloquine (two patients; 1·3%; 0·3–5·3; p=0·0018), and dihydroartemisinin–piperaquine (two patients 1·3%; 0·3–5·2%; p=0·0012). Hazard ratios for re-infection (95% CI) after artesunate–amodiaquine were 3·2 (1·3–8·0) compared with the two artesunate–mefloquine groups (p=0·01), 2·6 (1·0–6–0) compared with artemether–lumefantrine (p=0·04), and 2·3 (0·9–6·0) compared with dihydroartemisinin–piperaquine (p=0·08). Mixed falciparum and vivax infections were common: 129 (16%) had a mixed infection at presentation and 330 (41%) patients had one or more episodes of Plasmodium vivax infection during follow-up. The addition of a single dose of primaquine (0·75 mg/kg) reduced P falciparum gametocyte carriage substantially: rate ratio 11·9 (95% CI 7·4–20·5). All regimens were well tolerated. Adverse events were reported by 599 patients, most commonly vomiting and dizziness. Other side-effects were less common and were not related to a specific treatment.
Interpretation
Artesunate–amodiaquine should not be used in Myanmar, because the other ACTs are substantially more effective. Artesunate–mefloquine provided the greatest post-treatment suppression of malaria. Adding a single dose of primaquine would substantially reduce transmission potential. Vivax malaria, not recurrent falciparum malaria, is the main complication after treatment of P falciparum infections in this region.
Funding
Médecins sans Frontières (Holland) and the Wellcome Trust Mahidol University Oxford Tropical Medicine Research Programme.
doi:10.1016/S1473-3099(10)70187-0
PMCID: PMC2947715  PMID: 20832366
7.  Pharmacokinetics and Pharmacodynamics of Oral Artesunate Monotherapy in Patients with Uncomplicated Plasmodium falciparum Malaria in Western Cambodia 
Antimicrobial Agents and Chemotherapy  2012;56(11):5484-5493.
Artemisinin-resistant malaria along the Thailand-Cambodian border is an important public health concern, yet mechanisms of drug action and their contributions to the development of resistance are poorly understood. The pharmacokinetics and pharmacodynamics of oral artesunate monotherapy were explored in a dose-ranging trial in an area of emerging artesunate resistance in western Cambodia. We enrolled 143 evaluable subjects with uncomplicated Plasmodium falciparum malaria in an open label study of directly observed artesunate monotherapy at 3 dose levels (2, 4, and 6 mg/kg of body weight/day) for 7 days at Tasanh Health Center, Tasanh, Cambodia. Clinical outcomes were similar among the 3 groups. Wide variability in artesunate and dihydroartemisinin concentrations in plasma was observed. No significant dose-effect or concentration-effect relationships between pharmacokinetic (PK) and parasite clearance parameters were observed, though baseline parasitemia was modestly correlated with increased parasite clearance times. The overall parasite clearance times were prolonged compared with the clearance times in a previous study at this site in 2006 to 2007, but this did not persist when the evaluation was limited to subjects with a comparable artesunate dose (4 mg/kg/day) and baseline parasitemia from the two studies. Reduced plasma drug levels with higher presentation parasitemias, previously hypothesized to result from partitioning into infected red blood cells, was not observed in this population with uncomplicated malaria. Neither in vitro parasite susceptibility nor plasma drug concentrations appeared to have a direct relationship with the pharmacodynamic (PD) effects of oral artesunate on malaria parasites. While direct concentration-effect relationships were not found, it remains possible that a population PK modeling approach that allows modeling of greater dose separation might discern more-subtle relationships.
doi:10.1128/AAC.00044-12
PMCID: PMC3486599  PMID: 22869581
8.  Identification of resistance of Plasmodium falciparum to artesunate-mefloquine combination in an area along the Thai-Myanmar border: integration of clinico-parasitological response, systemic drug exposure, and in vitro parasite sensitivity 
Malaria Journal  2013;12:263.
Background
A markedly high failure rate of three-day artesunate-mefloquine was observed in the area along the Thai-Myanmar border.
Methods
Identification of Plasmodium falciparum isolates with intrinsic resistance to each component of the artesunate-mefloquine combination was analysed with integrated information on clinico-parasitological response, together with systemic drug exposure (area under blood/plasma concentration-time curves (AUC)) of dihydroartemisinin and mefloquine, and in vitro sensitivity of P. falciparum in a total of 17 out of 29 P. falciparum isolates from patients with acute uncomplicated falciparum malaria. Analysis of the contribution of in vitro parasite sensitivity and systemic drug exposure and relationship with pfmdr1 copy number in the group with sensitive response was performed in 21 of 69 cases.
Results
Identification of resistance and/or reduced intrinsic parasitocidal activity of artesunate and/or mefloquine without pharmacokinetic or other host-related factors were confirmed in six cases: one with reduced sensitivity to artesunate alone, two with resistance to mefloquine alone, and three with reduced sensitivity to artesunate combined with resistance to mefloquine. Resistance and/or reduced intrinsic parasitocidal activity of mefloquine/artesunate, together with contribution of pharmacokinetic factor of mefloquine and/or artesunate were identified in seven cases: two with resistance to mefloquine alone, and five with resistance to mefloquine combined with reduced sensitivity to artesunate. Pharmacokinetic factor alone contributed to recrudescence in three cases, all of which had inadequate whole blood mefloquine levels (AUC0-7days). Other host-related factors contributed to recrudescence in one case. Amplification of pfmdr1 (increasing of pfmdr1 copy number) is a related molecular marker of artesunate-mefloquine resistance and seems to be a suitable molecular marker to predict occurrence of recrudescence.
Conclusions
Despite the evidence of a low level of a decline in sensitivity of P. falciparum isolates to artemisinins in areas along the Thai-Myanmar border, artemisinin-based combination therapy (ACT) would be expected to remain the key anti-malarial drug for treatment of multidrug resistance P. falciparum. Continued monitoring and active surveillance of clinical efficacy of ACT, including identification of true artemisinin resistant parasites, is required for appropriate implementation of malaria control policy in this area.
doi:10.1186/1475-2875-12-263
PMCID: PMC3737112  PMID: 23898808
Plasmodium falciparum; Drug resistance; Artesunate; Mefloquine; pfmdr1 copy number; in vitro sensitivity
9.  A Head-to-Head Comparison of Four Artemisinin-Based Combinations for Treating Uncomplicated Malaria in African Children: A Randomized Trial 
PLoS Medicine  2011;8(11):e1001119.
The Four Artemisinin-Based Combinations (4ABC) Study Group reports a randomized, non-inferiority trial comparing the efficacy and safety of four ACTs in children with mild Plasmodium falciparum malaria from seven sub-Saharan African countries.
Background
Artemisinin-based combination therapies (ACTs) are the mainstay for the management of uncomplicated malaria cases. However, up-to-date data able to assist sub-Saharan African countries formulating appropriate antimalarial drug policies are scarce.
Methods and Findings
Between 9 July 2007 and 19 June 2009, a randomized, non-inferiority (10% difference threshold in efficacy at day 28) clinical trial was carried out at 12 sites in seven sub-Saharan African countries. Each site compared three of four ACTs, namely amodiaquine-artesunate (ASAQ), dihydroartemisinin-piperaquine (DHAPQ), artemether-lumefantrine (AL), or chlorproguanil-dapsone-artesunate (CD+A). Overall, 4,116 children 6–59 mo old with uncomplicated Plasmodium falciparum malaria were treated (1,226 with AL, 1,002 with ASAQ, 413 with CD+A, and 1,475 with DHAPQ), actively followed up until day 28, and then passively followed up for the next 6 mo. At day 28, for the PCR-adjusted efficacy, non-inferiority was established for three pair-wise comparisons: DHAPQ (97.3%) versus AL (95.5%) (odds ratio [OR]: 0.59, 95% CI: 0.37–0.94); DHAPQ (97.6%) versus ASAQ (96.8%) (OR: 0.74, 95% CI: 0.41–1.34), and ASAQ (97.1%) versus AL (94.4%) (OR: 0.50, 95% CI: 0.28–0.92). For the PCR-unadjusted efficacy, AL was significantly less efficacious than DHAPQ (72.7% versus 89.5%) (OR: 0.27, 95% CI: 0.21–0.34) and ASAQ (66.2% versus 80.4%) (OR: 0.40, 95% CI: 0.30–0.53), while DHAPQ (92.2%) had higher efficacy than ASAQ (80.8%) but non-inferiority could not be excluded (OR: 0.35, 95% CI: 0.26–0.48). CD+A was significantly less efficacious than the other three treatments. Day 63 results were similar to those observed at day 28.
Conclusions
This large head-to-head comparison of most currently available ACTs in sub-Saharan Africa showed that AL, ASAQ, and DHAPQ had excellent efficacy, up to day 63 post-treatment. The risk of recurrent infections was significantly lower for DHAPQ, followed by ASAQ and then AL, supporting the recent recommendation of considering DHAPQ as a valid option for the treatment of uncomplicated P. falciparum malaria.
Trial Registration
ClinicalTrials.gov NCT00393679; Pan African Clinical Trials Registry PACTR2009010000911750
Please see later in the article for the Editors' Summary
Editors' Summary
Background
Malaria is a global public-health problem. Half the world's population is at risk of this mosquito-borne parasitic disease, which kills a million people (mainly children living in sub-Saharan Africa) every year. Although several parasites cause malaria, Plasmodium falciparum is responsible for most of these deaths. During the second half of the 20th century, the main treatments for malaria were inexpensive “monotherapies” such as chloroquine and sulfadoxine-pyrimethamine. Unfortunately, the malaria parasite quickly developed resistance to many of these monotherapies, and in the 1990 s, there was a widespread upsurge in P. falciparum malaria. To combat this increase, the World Health Organization (WHO) now recommends artemisinin-based combination therapy (ACT) for first-line treatment of P. falciparum malaria in all regions where there is drug-resistant malaria. In ACT, artemisinin derivatives (new, fast-acting antimalarial drugs) are used in combination with another antimalarial drug (a partner drug) to reduce the chances of P. falciparum becoming resistant to either drug.
Why Was This Study Done?
WHO currently recommends five ACTs—amodiaquine-artesunate (ASAQ), dihydroartemisinin-piperaquine (DHAPQ), artemether-lumefantrine (AL), artesunate-mefloquine, and artesunate-sulfadoxine-pyrimethamine—for the treatment of malaria. Its treatment guidelines state that the choice of ACT in a country or region should be based on the local level of resistance to the non-artemisinin-based partner drug in the combination. However, data on resistance levels to these partner drugs are scarce or unavailable for many sub-Saharan African countries. To help these countries make an informed choice about their national antimalarial treatment policies, in this randomized, non-inferiority trial, the researchers compare the efficacy and safety of four ACTs in African children with uncomplicated (mild) P. falciparum malaria. In a randomized trial, groups of randomly chosen patients with a specific disease are given different treatments and then followed to compare the outcomes of these interventions. A non-inferiority trial investigates whether one treatment is not worse than another treatment.
What Did the Researchers Do and Find?
Each of twelve sites in seven sub-Saharan African countries compared three ACTs out of ASAQ, DHAPQ, AL, and chlorproguanil-dapsone-artesunate (CD+A). Overall, 4,116 young children with uncomplicated malaria were treated with ACT, actively followed up for 28 days (their parents brought them back to the site for pre-arranged check-ups), and passively followed up for six months (parents brought their children back if they developed any illnesses). At each visit, blood samples were examined for the presence of parasites, and a technique called PCR was used to determine which cases of malaria were new infections and which were recurrences of the original infection. The researchers then calculated the percentage of patients with no infection or with a new infection (the PCR-adjusted adequate clinical and parasitological response [ACPR]) and the percentage of patients with no infection (the PCR-unadjusted ACPR). For the PCR-adjusted efficacy, three pair-wise comparisons (DHAPQ versus AL, DHAPQ versus ASAQ, and ASAQ versus AL) showed non-inferiority at 28 days. That is, for example, similar percentages of patients given DHAPQ or AL (97.3% and 95.5%, respectively) had either no infection or a new infection. CD+A was less efficacious than the other three treatments. For the PCR-unadjusted efficacy, AL was significantly less efficacious than DHAPQ and ASAQ; DHAPQ had a higher efficacy than ASAQ, but non-inferiority could not be excluded. That is, the difference in efficacy of these two drugs might have happened by chance.
What Do These Findings Mean?
These findings suggest that AL, ASAQ, and DHAPQ are all efficacious for the treatment of uncomplicated malaria in children; CD+A was withdrawn partway through the trial because of side effects, but these findings also suggest that it was less efficacious than the other ACTs. Importantly, the PCR-unadjusted results indicate that the risk of children becoming re-infected with malaria parasites soon after treatment was lowest for DHAPQ, followed by ASAQ, and then AL. Because these findings are based on pooled results from seven sub-Saharan African countries, they are likely to be generalizable and thus of use in setting national antimalarial drug policies throughout the region. AL and ASAQ are already included in the antimalarial drug policies of many sub-Saharan African countries, note the researchers, but these findings support the WHO recommendation that DHAPQ should also be considered for the treatment for uncomplicated P. falciparum malaria.
Additional Information
Please access these websites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.1001119.
Information is available from WHO on malaria (in several languages); the 2010 World Malaria Report provides details of the current global malaria situation; the WHO Guidelines for the Treatment of Malaria and the report Assessment and Monitoring of Antimalarial Drug Efficacy for the Treatment of Uncomplicated Malaria are available
The US Centers for Disease Control and Prevention provide information on malaria (in English and Spanish), including a selection of personal stories about malaria
Information is available from the Roll Back Malaria Partnership on the global control of malaria including fact sheets about ACTs and about malaria in Africa
MedlinePlus provides links to additional information on malaria (in English and Spanish)
doi:10.1371/journal.pmed.1001119
PMCID: PMC3210754  PMID: 22087077
10.  Population Pharmacokinetics of Artesunate and Dihydroartemisinin following Intra-Rectal Dosing of Artesunate in Malaria Patients 
PLoS Medicine  2006;3(11):e444.
Background
Intra-rectal artesunate has been developed as a potentially life-saving treatment of severe malaria in rural village settings where administration of parenteral antimalarial drugs is not possible. We studied the population pharmacokinetics of intra-rectal artesunate and the relationship with parasitological responses in patients with moderately severe falciparum malaria.
Methods and Findings
Adults and children in Africa and Southeast Asia with moderately severe malaria were recruited in two Phase II studies (12 adults from Southeast Asia and 11 children from Africa) with intensive sampling protocols, and three Phase III studies (44 children from Southeast Asia, and 86 children and 26 adults from Africa) with sparse sampling. All patients received 10 mg/kg artesunate as a single intra-rectal dose of suppositories. Venous blood samples were taken during a period of 24 h following dosing. Plasma artesunate and dihydroartemisinin (DHA, the main biologically active metabolite) concentrations were measured by high-performance liquid chromatography with electrochemical detection. The pharmacokinetic properties of DHA were determined using nonlinear mixed-effects modelling. Artesunate is rapidly hydrolysed in vivo to DHA, and this contributes the majority of antimalarial activity. For DHA, a one-compartment model assuming complete conversion from artesunate and first-order appearance and elimination kinetics gave the best fit to the data. The mean population estimate of apparent clearance (CL/F) was 2.64 (l/kg/h) with 66% inter-individual variability. The apparent volume of distribution (V/F) was 2.75 (l/kg) with 96% inter-individual variability. The estimated DHA population mean elimination half-life was 43 min. Gender was associated with increased mean CL/F by 1.14 (95% CI: 0.36–1.92) (l/kg/h) for a male compared with a female, and weight was positively associated with V/F. Larger V/Fs were observed for the patients requiring early rescue treatment compared with the remainder, independent of any confounders. No associations between the parasitological responses and the posterior individual estimates of V/F, CL/F, and AUC0–6h were observed.
Conclusions
The pharmacokinetic properties of DHA were affected only by gender and body weight. Patients with the lowest area under the DHA concentration curve did not have slower parasite clearance, suggesting that rectal artesunate is well absorbed in most patients with moderately severe malaria. However, a number of modelling assumptions were required due to the large intra- and inter-individual variability of the DHA concentrations.
A study of the population pharmacokinetics of intra-rectal artesunate in patients with moderately severe falciparum malaria found the pharmacokinetic properties of dihydroartemisinin were affected only by gender and body weight.
Editors' Summary
Background.
More than 40% of the world's population is at risk of malaria, a tropical parasitic disease that is transmitted between people by infected mosquitoes. Malaria parasites cause a 'flu-like illness that includes chills, fevers, headaches, and sometimes nausea and vomiting. If untreated, people with malaria can rapidly become anemic—the parasite destroys their red blood cells—or can develop complications that damage the brain and other organs. Severe malaria can be fatal and must be treated quickly. It has become a matter of great concern that the parasite has developed resistance to most of the drugs used to treat or prevent malaria. In the past few years, artemisinin derivatives have been shown to be an effective new form of treatment. Artemisinin derivatives are effective, rapid-acting antimalarial drugs—wormwood, the plant source of artemisinin, is an ancient Chinese cure for malaria. Artesunate, a water-soluble derivative of artemisinin, can be given as tablets or as injections. However, people with severe malaria often cannot take oral medicines, and in rural settings in the developing world, artesunate injections are usually impracticable. Consequently, rectal artesunate suppositories have been developed to provide first-line treatment of severe malaria in these settings. This simple dosing method can “buy” patients valuable time during which they can be moved to a hospital for further treatment.
Why Was This Study Done?
When treating severe malaria, it is important that every patient absorbs the antimalarial drug rapidly and efficiently into their blood. If even a small proportion of patients malabsorb the drug, many people could die. How the body processes a drug is known as pharmacokinetics, and although some pharmacokinetic studies have investigated how the body processes artesunate given in rectal suppositories, relatively little is know about the population pharmacokinetics of artesunate given this way. That is, the patient characteristics that affect the processing of intra-rectal artesunate are not known, and it is unclear whether a small proportion of the population might fail to absorb the drug given via this route. In this study, the researchers have developed and tested a population pharmacokinetic model for artesunate given rectally to children and adults with moderately severe malaria.
What Did the Researchers Do and Find?
The researchers took serial blood samples from nearly 200 patients with moderately severe malaria in Africa and Southeast Asia for the first 24 hours after they received a rectal artesunate suppository. They measured the levels of artesunate and dihydroartemisinin (DHA; the body rapidly converts artesunate to DHA, which kills the malaria parasites) in these samples and used these data to build a pharmacokinetic model for how the body processes. Averaged out across the patients, they calculated, for example, that half of the drug present absorbed was eliminated within 43 minutes. To find out whether any patient characteristics affected the pharmacokinetics of intra-rectal artesunate, the researchers used their model to estimate the clearance of DHA from the body and the ability of DHA to spread through the body (so-called apparent volume of distribution) for the study patients. This analysis showed that only gender and weight affected DHA pharmacokinetics. Finally, the researchers showed that how well the parasite was cleared from the patients was not related to these pharmacokinetic parameters, although the need for earlier rescue treatment was associated with a larger volume of distribution for DHA. Importantly, the parasitological response was not affected by the estimated cumulative amount of DHA absorbed into the blood during the first six hours after treatment.
What Do These Findings Mean?
The data presented in this study indicate that individual patients processed artesunate very differently in terms of how they absorbed the drug and how it spread around the body. Even so, the maximal effects of artesunate on the malaria parasite were achieved rapidly in nearly all the patients. This and other pharmacokinetic findings must be interpreted with caution, warn the researchers, because their model included many assumptions to allow, for example, for the variability of DHA concentrations both within individual patients and between patients. Nevertheless, the findings provide important clues about which patient characteristics might cause early treatment failure, and indicate that artesunate is sufficiently well absorbed via the rectal route in most patients to make artesunate suppositories a promising first-line treatment for moderately severe malaria.
Additional Information.
Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.0030444.
• World Health Organization links to general information on malaria plus specific information on rectal artesunate
• MedlinePlus encyclopedia entry on malaria
• US Centers for Disease Control and Prevention information on malaria for patients and professionals
• Wikipedia pages on malaria and artemisinin (note that Wikipedia is a free online encyclopedia that anyone can edit)
doi:10.1371/journal.pmed.0030444
PMCID: PMC1664603  PMID: 17132053
11.  Failure of artesunate-mefloquine combination therapy for uncomplicated Plasmodium falciparum malaria in southern Cambodia 
Malaria Journal  2009;8:10.
Background
Resistance to anti-malarial drugs hampers control efforts and increases the risk of morbidity and mortality from malaria. The efficacy of standard therapies for uncomplicated Plasmodium falciparum and Plasmodium vivax malaria was assessed in Chumkiri, Kampot Province, Cambodia.
Methods
One hundred fifty-one subjects with uncomplicated falciparum malaria received directly observed therapy with 12 mg/kg artesunate (over three days) and 25 mg/kg mefloquine, up to a maximum dose of 600 mg artesunate/1,000 mg mefloquine. One hundred nine subjects with uncomplicated vivax malaria received a total of 25 mg/kg chloroquine, up to a maximum dose of 1,500 mg, over three days. Subjects were followed for 42 days or until recurrent parasitaemia was observed. For P. falciparum infected subjects, PCR genotyping of msp1, msp2, and glurp was used to distinguish treatment failures from new infections. Treatment failure rates at days 28 and 42 were analyzed using both per protocol and Kaplan-Meier survival analysis. Real Time PCR was used to measure the copy number of the pfmdr1 gene and standard 48-hour isotopic hypoxanthine incorporation assays were used to measure IC50 for anti-malarial drugs.
Results
Among P. falciparum infected subjects, 47.0% were still parasitemic on day 2 and 11.3% on day 3. The PCR corrected treatment failure rates determined by survival analysis at 28 and 42 days were 13.1% and 18.8%, respectively. Treatment failure was associated with increased pfmdr1 copy number, higher initial parasitaemia, higher mefloquine IC50, and longer time to parasite clearance. One P. falciparum isolate, from a treatment failure, had markedly elevated IC50 for both mefloquine (130 nM) and artesunate (6.7 nM). Among P. vivax infected subjects, 42.1% suffered recurrent P. vivax parasitaemia. None acquired new P. falciparum infection.
Conclusion
The results suggest that artesunate-mefloquine combination therapy is beginning to fail in southern Cambodia and that resistance is not confined to the provinces at the Thai-Cambodian border. It is unclear whether the treatment failures are due solely to mefloquine resistance or to artesunate resistance as well. The findings of delayed clearance times and elevated artesunate IC50 suggest that artesunate resistance may be emerging on a background of mefloquine resistance.
doi:10.1186/1475-2875-8-10
PMCID: PMC2628668  PMID: 19138388
12.  Declining in efficacy of a three-day combination regimen of mefloquine-artesunate in a multi-drug resistance area along the Thai-Myanmar border 
Malaria Journal  2010;9:273.
Background
Declining in clinical efficacy of artesunate-mefloquine combination has been documented in areas along the eastern border (Thai-Cambodian) of Thailand. In the present study, the clinical efficacy of the three-day combination regimen of artesunate-mefloquine as first-line treatment for acute uncomplicated falciparum malaria in Thailand was monitored in an area along the western border (Thai-Myanmar) of the country.
Methods
A total of 150 Burmese patients (85 males and 65 females) aged between 16 and 50 years who were attending the Mae Tao clinic, Mae-Sot, Tak Province, and presenting with symptomatic acute uncomplicated Plasmodium falciparum malaria were included into the study. Patients were treated initially (day 0) with 4 mg/kg body weight artesunate and 15 mg/kg body weight mefloquine. The dose regimen on day 2 was 4 mg/kg body weight artesunate and 10 mg/kg body weight mefloquine. On day 3, artesunate at the dose of 4 mg/kg body weight was given with 0.6 mg/kg body weight primaquine. Whole blood mefloquine and plasma artesunate and dihydroartemisinin (active plasma metabolite of artesunate) concentrations following treatment were determined by high performance liquid chromatography (HPLC) and liquid chromatography-mass spectrometry (LCMS), respectively.
Results
Thirty-four cases had recrudescence during days 7 and 42. Five and 5 cases, respectively had reinfection with P. falciparum and reappearance of Plasmodium vivax in their peripheral blood during follow-up. The Kaplan-Meier estimate of the 42-and 28-day efficacy rates of this combination regimen were 72.58% (95% CI: 63.20-79.07%) and 83.06 (95% CI 76.14-94.40%), respectively. Parasite clearance time (PCT) and fever clearance time (FCT) were significantly prolonged in patients with treatment failure compared with those with sensitive response [median (95% CI) values for PCT 32.0 (20.0-48.0) vs 24.0 (14.0-32.0) hr and FCT 30.0 (22.0-42.0) vs 26.0 (18.0-36.0) hr; p < 0.005]. Whole blood mefloquine concentrations on days 1, 7 and 14 in patients with sensitive and recrudescence response were comparable. Although plasma concentration of dihydroartemisinin at 1 hour of treatment was significantly lower in patients with recrudescence compared with sensitive response [mean (95% CI) 456 (215-875) vs 525 (452-599) ng/ml; p < 0.001], the proportion of patients with recrudescence who had relatively low (compared with the lower limit of 95% CI defined in the sensitive group) was significantly smaller than that of the sensitive group.
Conclusions
Although pharmacokinetic (ethnic-related) factors including resistance of P. falciparum to mefloquine contribute to some treatment failure following treatment with a three-day combination regimen of artesunate-mefloquine, results suggest that artesunate resistance may be emerging at the Thai-Myanmar border.
doi:10.1186/1475-2875-9-273
PMCID: PMC2959072  PMID: 20929590
13.  Malaria: uncomplicated, caused by Plasmodium falciparum  
Clinical Evidence  2008;2008:0919.
Introduction
Malaria is a major health problem in the tropics, with 300 to 500 million new clinical cases annually, most of them cases of uncomplicated malaria. An estimated 1.1 to 2.7 million deaths occur annually as a result of severe falciparum malaria. Uncomplicated malaria can progress to severe malaria, become chronic, or resolve, depending on host immunity and prompt access to appropriate treatment.
Methods and outcomes
We conducted a systematic review and aimed to answer the following clinical questions: Are artemisinin combination treatments more effective than non-artemisinin combination treatments in people living in endemic areas (excluding South-East Asia)? Which artemisinin combination treatment is most effective in people living in endemic areas? We searched: Medline, Embase, The Cochrane Library, and other important databases up to December 2007 (Clinical Evidence reviews are updated periodically; please check our website for the most up-to-date version of this review). We included harms alerts from relevant organisations such as the US Food and Drug Administration (FDA) and the UK Medicines and Healthcare products Regulatory Agency (MHRA).
Results
We found 25 systematic reviews, RCTs, or observational studies that met our inclusion criteria.
Conclusions
In this systematic review, we present information relating to the effectiveness and safety of the following interventions: amodiaquine plus sulfadoxine-pyrimethamine; artemether-lumefantrine; artesunate plus mefloquine; artesunate plus amodiaquine; and artesunate plus sulfadoxine-pyrimethamine.
Key Points
Uncomplicated malaria is where the person has symptomatic infection with malaria parasites, but no signs of vital organ disturbance. Uncomplicated malaria can progress to severe malaria, become chronic, or resolve, depending on host immunity and prompt access to appropriate treatment.Severe malaria is more likely to develop in people with no prior immunity, and accounts for over one million deaths worldwide each year.The choice between treatment regimens depends partly on background drug-resistance patterns in the relevant country or region.
In most RCTs, artemether-lumefantrine was more effective than amodiaquine plus sulfadoxine-pyrimethamine. However, it was not more effective in all RCTs.
Artesunate plus amodiaquine is more effective at curing a current infection than amodiaquine plus sulfadoxine-pyrimethamine, but, in terms of people being parasite free at day 28, there is little to choose between them, since the risk of new infections appears greater with artesunate plus amodiaquine.
Amodiaquine plus sulfadoxine-pyrimethamine achieved higher cure rates than artesunate plus sulfadoxine-pyrimethamine. Gametocyte clearance was better with artesunate plus sulfadoxine-pyrimethamine.
Evidence suggests that a six-dose regimen of artemether-lumefantrine is more effective than a four-dose regimen.
Both artemether-lumefantrine (6 doses) and artesunate plus amodiaquine were effective, but artemether-lumefantrine (6 doses) was superior in some trials.
Artesunate plus mefloquine performs better than artemether-lumefantrine in terms of cure in some areas where this has been studied.
The choice between artesunate plus amodiaquine and artesunate plus sulfadoxine-pyrimethamine depends on background drug-resistance patterns in the relevant country or region.
We found insufficient evidence on the effects of artemer-lumefantrine (6 doses) versus artesunate plus sulfadoxine-pyrimethamine, artesunate plus mefloquine versus artesunate plus amodiaquine, or artesunate plus mefloquine versus artesunate plus sulfadoxine-pyrimethamine.
PMCID: PMC2907983  PMID: 19450360
14.  Spread of Artemisinin Resistance in Plasmodium falciparum Malaria 
The New England journal of medicine  2014;371(5):411-423.
BACKGROUND
Artemisinin resistance in Plasmodium falciparum has emerged in Southeast Asia and now poses a threat to the control and elimination of malaria. Mapping the geographic extent of resistance is essential for planning containment and elimination strategies.
METHODS
Between May 2011 and April 2013, we enrolled 1241 adults and children with acute, uncomplicated falciparum malaria in an open-label trial at 15 sites in 10 countries (7 in Asia and 3 in Africa). Patients received artesunate, administered orally at a daily dose of either 2 mg per kilogram of body weight per day or 4 mg per kilogram, for 3 days, followed by a standard 3-day course of artemisinin-based combination therapy. Parasite counts in peripheral-blood samples were measured every 6 hours, and the parasite clearance half-lives were determined.
RESULTS
The median parasite clearance half-lives ranged from 1.9 hours in the Democratic Republic of Congo to 7.0 hours at the Thailand–Cambodia border. Slowly clearing in fections (parasite clearance half-life >5 hours), strongly associated with single point mutations in the “propeller” region of the P. falciparum kelch protein gene on chromosome 13 (kelch13), were detected throughout mainland Southeast Asia from southern Vietnam to central Myanmar. The incidence of pretreatment and post-treatment gametocytemia was higher among patients with slow parasite clearance, suggesting greater potential for transmission. In western Cambodia, where artemisinin-based combination therapies are failing, the 6-day course of antimalarial therapy was associated with a cure rate of 97.7% (95% confidence interval, 90.9 to 99.4) at 42 days.
CONCLUSIONS
Artemisinin resistance to P. falciparum, which is now prevalent across mainland Southeast Asia, is associated with mutations in kelch13. Prolonged courses of artemisinin-based combination therapies are currently efficacious in areas where standard 3-day treatments are failing. (Funded by the U.K. Department of International Development and others; ClinicalTrials.gov number, NCT01350856.)
doi:10.1056/NEJMoa1314981
PMCID: PMC4143591  PMID: 25075834
15.  Compliance with a three-day course of artesunate-mefloquine combination and baseline anti-malarial treatment in an area of Thailand with highly multidrug resistant falciparum malaria 
Malaria Journal  2010;9:43.
Background
Artemisinin-based combination therapy (ACT) is presently recommended by the World Health Organization as first-line treatment for uncomplicated Plasmodium falciparum malaria in several countries, as a mean of prolonging the effectiveness of first-line malaria treatment regimens. A three-day course of artesunate-mefloquine (4 mg/kg body weight once daily for three consecutive days, plus 15 and 10 mg/kg body weight mefloquine on the first and second days) has been adopted by Malaria Control Programme of Thailand as first-line treatment for uncomplicated falciparum malaria all over the country since 2008. The gametocytocydal anti-malarial drug primaquine is administered at the dose of 30 mg (0.6 mg/kg) on the last day. The aim of the present study was to assess patient compliance of this combination regimen when applied to field condition.
Methods
A total of 240 patients (196 males and 44 females) who were attending the malaria clinics in Mae-Sot, Tak Province and presenting with symptomatic acute uncomplicated falciparum malaria, with no reappearance of Plasmodium vivax parasitaemia during follow-up were included into the study. The first dose of the treatment was given to the patients under direct supervision. All patients were given the medication for self-treatment at home and were requested to come back for follow-up on day 3 of the initial treatment. Baseline (day 0) and day 3 whole blood mefloquine and plasma primaquine concentrations were determined by high performance liquid chromatography.
Results
Two patients had recrudescence on days 28 and 35. The Kaplan-Meier estimate of the 42-day efficacy rate of this combination regimen was 99.2% (238/240). Based on whole blood mefloquine and plasma primaquine concentrations on day 3 of the initial treatment, compliance with mefloquine and primaquine in this three-day artesunate-mefloquine combination regimen were 96.3% (207/215), and 98.5% (197/200), respectively. Baseline mefloquine and primaquine levels were observed in 24 and 16% of the patients.
Conclusion
The current first-line treatment and a three-day combination regimen of artesunate-mefloquine provides excellent patient compliance with good efficacy and tolerability in the treatment of highly multidrug resistance falciparum malaria. Previous treatment with mefloquine and primaquine were common in this area.
doi:10.1186/1475-2875-9-43
PMCID: PMC2829592  PMID: 20132537
16.  Pfmdr1 copy number and arteminisin derivatives combination therapy failure in falciparum malaria in Cambodia 
Malaria Journal  2009;8:11.
Background
The combination of artesunate and mefloquine was introduced as the national first-line treatment for Plasmodium falciparum malaria in Cambodia in 2000. However, recent clinical trials performed at the Thai-Cambodian border have pointed to the declining efficacy of both artesunate-mefloquine and artemether-lumefantrine. Since pfmdr1 modulates susceptibility to mefloquine and artemisinin derivatives, the aim of this study was to assess the link between pfmdr1 copy number, in vitro susceptibility to individual drugs and treatment failure to combination therapy.
Methods
Blood samples were collected from P. falciparum-infected patients enrolled in two in vivo efficacy studies in north-western Cambodia: 135 patients were treated with artemether-lumefantrine (AL group) in Sampovloun in 2002 and 2003, and 140 patients with artesunate-mefloquine (AM group) in Sampovloun and Veal Veng in 2003 and 2004. At enrollment, the in vitro IC50 was tested and the strains were genotyped for pfmdr1 copy number by real-time PCR.
Results
The pfmdr1 copy number was analysed for 115 isolates in the AM group, and for 109 isolates in the AL group. Parasites with increased pfmdr1 copy number had significantly reduced in vitro susceptibility to mefloquine, lumefantrine and artesunate. There was no association between pfmdr1 polymorphisms and in vitro susceptibilities. In the patients treated with AM, the mean pfmdr1copy number was lower in subjects with adequate clinical and parasitological response compared to those who experienced late treatment failure (n = 112, p < 0.001). This was not observed in the patients treated with AL (n = 96, p = 0.364). The presence of three or more copies of pfmdr1 were associated with recrudescence in artesunate-mefloquine treated patients (hazard ratio (HR) = 7.80 [95%CI: 2.09–29.10], N = 115), p = 0.002) but not with recrudescence in artemether-lumefantrine treated patients (HR = 1.03 [95%CI: 0.24–4.44], N = 109, p = 0.969).
Conclusion
This study shows that pfmdr1 copy number is a molecular marker of AM treatment failure in falciparum malaria on the Thai-Cambodian border. However, while it is associated with increased IC50 for lumefantrine, pfmdr1 copy number is not associated with AL treatment failure in the area, suggesting involvement of other molecular mechanisms in AL treatment failures in Cambodia.
doi:10.1186/1475-2875-8-11
PMCID: PMC2627910  PMID: 19138391
17.  Artemisinin Combination Therapies for Treatment of Uncomplicated Malaria in Uganda 
PLoS Clinical Trials  2006;1(1):e7.
Objectives:
To compare the efficacy and safety of artemisinin combination therapies for the treatment of uncomplicated falciparum malaria in Uganda.
Design:
Randomized single-blind controlled trial.
Setting:
Tororo, Uganda, an area of high-level malaria transmission.
Participants:
Children aged one to ten years with confirmed uncomplicated P. falciparum malaria.
Interventions:
Amodiaquine + artesunate or artemether–lumefantrine.
Outcome Measures:
Risks of recurrent symptomatic malaria and recurrent parasitemia at 28 days, unadjusted and adjusted by genotyping to distinguish recrudescences and new infections.
Results:
Of 408 participants enrolled, 403 with unadjusted efficacy outcomes were included in the per-protocol analysis. Both treatment regimens were highly efficacious; no recrudescences occurred in patients treated with amodiaquine + artesunate, and only two occurred in those treated with artemether–lumefantrine. However, recurrent malaria due to new infections was common. The unadjusted risk of recurrent symptomatic malaria was significantly lower for participants treated with artemether–lumefantrine than for those treated with amodiaquine + artesunate (27% versus 42%, risk difference 15%, 95% CI 5.9%–24.2%). Similar results were seen for the risk of recurrent parasitemia (51% artemether–lumefantrine versus 66% amodiaquine + artesunate, risk difference 16%, 95% CI 6.2%–25.2%). Amodiaquine + artesunate and artemether–lumefantrine were both well-tolerated. Serious adverse events were uncommon with both regimens.
Conclusions:
Amodiaquine + artesunate and artemether–lumefantrine were both highly efficacious for treatment of uncomplicated malaria. However, in this holoendemic area, despite the excellent performance of both regimens in terms of efficacy, many patients experienced recurrent parasitemia due to new infections. Artemether–lumefantrine was superior to amodiaquine + artesunate for prevention of new infections. To maximize the benefit of artemisinin combination therapy in Africa, treatment should be integrated with strategies to prevent malaria transmission. The impact of frequent repeated therapy on the efficacy, safety, and cost-effectiveness of new artemisinin regimens should be further investigated.
Editorial Commentary
Background: Malaria parasites have become resistant in much of Africa to many commonly used treatments, such as chloroquine and sulfadoxine–pyrimethamine. Newer drugs, such as artemisinin-based combination therapies (ACTs), have been used extensively in Southeast Asia. Artemether–lumefantrine (an ACT) has now been adopted as first-line malaria treatment in Uganda, with the combination of amodiaquine and artesunate as a backup treatment. There are two ways that successful treatment is measured; first by whether the treatment works in curing the infection; and second by whether it prevents the disease recurring—either the same infection (known as recrudescence), or a new infection. The researchers wanted to look at how artemether–lumefantrine compared with amodiaquine and artesunate for treating symptomatic malaria, and also at whether there were any differences in recurrence, either of clinical malaria, or of parasite infection without symptoms, for 28 days after treatment.
What this trial shows: This randomized trial in young children with confirmed malaria in Uganda showed that both treatments resulted in a similar initial response to therapy, as measured by the risk of early treatment failure (within three days). The researchers found that artemether–lumefantrine was more effective at reducing the risk and delayed the time to recurrence of malaria, compared with amodiaquine and artesunate. Additionally, treatment with artemether–lumefantrine resulted in a reduced rate of parasite infection without malaria symptoms, as compared with amodiaquine and artesunate. Nearly all cases of recurrent malaria after either treatment combination arose from new infections, rather than from recrudescences.
Strengths and limitations: The trial was correctly designed to test the questions of interest, and enough patients were recruited to properly examine the relative effects of the two treatment combinations. However, patients were only followed up for 28 days after treatment. A longer follow-up period might have revealed a higher rate of recurrence of malaria after treatment. In the trial, artemether–lumefantrine was not administered with food, and it's known that lumefantrine is absorbed better when it is taken with a small amount of fat. It's possible that the effect of artemether–lumefantrine seen in the trial could have been an underestimate of what might be achieved in ideal conditions.
Contribution to the evidence: This trial adds information on the efficacy of artemether–lumefantrine as compared with amodiaquine and artesunate in East Africa for treatment of uncomplicated (i.e., non-severe) symptomatic malaria. The results are consistent with those of other trials on the efficacy of ACTs that have been performed in the region. The study also adds data on the risk of recurrent infections in an area where malaria occurs very frequently. Even following treatment with either ACT, the risk of recurrence was very high.
doi:10.1371/journal.pctr.0010007
PMCID: PMC1488893  PMID: 16871329
18.  Focused Screening and Treatment (FSAT): A PCR-Based Strategy to Detect Malaria Parasite Carriers and Contain Drug Resistant P. falciparum, Pailin, Cambodia 
PLoS ONE  2012;7(10):e45797.
Recent studies have shown that Plasmodium falciparum malaria parasites in Pailin province, along the border between Thailand and Cambodia, have become resistant to artemisinin derivatives. To better define the epidemiology of P. falciparum populations and to assess the risk of the possible spread of these parasites outside Pailin, a new epidemiological tool named “Focused Screening and Treatment” (FSAT), based on active molecular detection of asymptomatic parasite carriers was introduced in 2010. Cross-sectional malariometric surveys using PCR were carried out in 20 out of 109 villages in Pailin province. Individuals detected as P. falciparum carriers were treated with atovaquone-proguanil combination plus a single dose of primaquine if the patient was non-G6PD deficient. Interviews were conducted to elicit history of cross-border travel that might contribute to the spread of artemisinin-resistant parasites. After directly observed treatment, patients were followed up and re-examined on day 7 and day 28. Among 6931 individuals screened, prevalence of P. falciparum carriers was less than 1%, of whom 96% were asymptomatic. Only 1.6% of the individuals had a travel history or plans to go outside Cambodia, with none of those tested being positive for P. falciparum. Retrospective analysis, using 2010 routine surveillance data, showed significant differences in the prevalence of asymptomatic carriers discovered by FSAT between villages classified as “high risk” and “low risk” based on malaria incidence data. All positive individuals treated and followed-up until day 28 were cured. No mutant-type allele related to atovaquone resistance was found. FSAT is a potentially useful tool to detect, treat and track clusters of asymptomatic carriers of P. falciparum along with providing valuable epidemiological information regarding cross-border movements of potential malaria parasite carriers and parasite gene flow.
doi:10.1371/journal.pone.0045797
PMCID: PMC3462177  PMID: 23049687
19.  Laboratory Detection of Artemisinin-Resistant Plasmodium falciparum 
Conventional 48-h in vitro susceptibility tests have low sensitivity in identifying artemisinin-resistant Plasmodium falciparum, defined phenotypically by low in vivo parasite clearance rates. We hypothesized originally that this discrepancy was explained by a loss of ring-stage susceptibility and so developed a simple field-adapted 24-h trophozoite maturation inhibition (TMI) assay focusing on the ring stage and compared it to the standard 48-h schizont maturation inhibition (WHO) test. In Pailin, western Cambodia, where artemisinin-resistant P. falciparum is prevalent, the TMI test mean (95% confidence interval) 50% inhibitory concentration (IC50) for artesunate was 6.8 (5.2 to 8.3) ng/ml compared with 1.5 (1.2 to 1.8) ng/ml for the standard 48-h WHO test (P = 0.001). TMI IC50s correlated significantly with the in vivo responses to artesunate (parasite clearance time [r = 0.44, P = 0.001] and parasite clearance half-life [r = 0.46, P = 0.001]), whereas the standard 48-h test values did not. On continuous culture of two resistant isolates, the artemisinin-resistant phenotype was lost after 6 weeks (IC50s fell from 10 and 12 ng/ml to 2.7 and 3 ng/ml, respectively). Slow parasite clearance in falciparum malaria in western Cambodia results from reduced ring-stage susceptibility.
doi:10.1128/AAC.01924-13
PMCID: PMC4068498  PMID: 24663013
20.  Ex Vivo Activity of Endoperoxide Antimalarials, Including Artemisone and Arterolane, against Multidrug-Resistant Plasmodium falciparum Isolates from Cambodia 
Antimicrobial Agents and Chemotherapy  2014;58(10):5831-5840.
Novel synthetic endoperoxides are being evaluated as new components of artemisinin combination therapies (ACTs) to treat artemisinin-resistant Plasmodium falciparum malaria. We conducted blinded ex vivo activity testing of fully synthetic (OZ78 and OZ277) and semisynthetic (artemisone, artemiside, artesunate, and dihydroartemisinin) endoperoxides in the histidine-rich protein 2 enzyme-linked immunosorbent assay against 200 P. falciparum isolates from areas of artemisinin-resistant malaria in western and northern Cambodia in 2009 and 2010. The order of potency and geometric mean (GM) 50% inhibitory concentrations (IC50s) were as follows: artemisone (2.40 nM) > artesunate (8.49 nM) > dihydroartemisinin (11.26 nM) > artemiside (15.28 nM) > OZ277 (31.25 nM) > OZ78 (755.27 nM). Ex vivo activities of test endoperoxides positively correlated with dihydroartemisinin and artesunate. The isolates were over 2-fold less susceptible to dihydroartemisinin than the artemisinin-sensitive P. falciparum W2 clone and showed sensitivity comparable to those with test endoperoxides and artesunate, with isolate/W2 IC50 susceptibility ratios of <2.0. All isolates had P. falciparum chloroquine resistance transporter mutations, with negative correlations in sensitivity to endoperoxides and chloroquine. The activities of endoperoxides (artesunate, dihydroartemisinin, OZ277, and artemisone) significantly correlated with that of the ACT partner drug, mefloquine. Isolates had mutations associated with clinical resistance to mefloquine, with 35% prevalence of P. falciparum multidrug resistance gene 1 (pfmdr1) amplification and 84.5% occurrence of the pfmdr1 Y184F mutation. GM IC50s for mefloquine, lumefantrine, and endoperoxides (artesunate, dihydroartemisinin, OZ277, OZ78, and artemisone) correlated with pfmdr1 copy number. Given that current ACTs are failing potentially from reduced sensitivity to artemisinins and partner drugs, newly identified mutations associated with artemisinin resistance reported in the literature and pfmdr1 mutations should be examined for their combined contributions to emerging ACT resistance.
doi:10.1128/AAC.02462-14
PMCID: PMC4187925  PMID: 25049252
21.  A randomized trial of artemether-lumefantrine versus mefloquine-artesunate for the treatment of uncomplicated multi-drug resistant Plasmodium falciparum on the western border of Thailand 
Malaria Journal  2005;4:46.
Background
The use of antimalarial drug combinations with artemisinin derivatives is recommended to overcome drug resistance in Plasmodium falciparum. The fixed combination of oral artemether-lumefantrine, an artemisinin combination therapy (ACT) is highly effective and well tolerated. It is the only registered fixed combination containing an artemisinin. The trial presented here was conducted to monitor the efficacy of the six-dose regimen of artemether-lumefantrine (ALN) in an area of multi-drug resistance, along the Thai-Myanmar border.
Methods
The trial was an open-label, two-arm, randomized study comparing artemether-lumefantrine and mefloquine-artesunate for the treatment of uncomplicated falciparum malaria with 42 days of follow up. Parasite genotyping by polymerase chain reaction (PCR) was used to distinguish recrudescent from newly acquired P. falciparum infections. The PCR adjusted cure rates were evaluated by survival analysis.
Results
In 2001–2002 a total of 490 patients with slide confirmed uncomplicated P. falciparum malaria were randomly assigned to receive artemether-lumefantrine (n = 245) or artesunate and mefloquine (n = 245) and were followed for 42 days. All patients had rapid initial clinical and parasitological responses. In both groups, the PCR adjusted cure rates by day 42 were high: 98.8% (95% CI 96.4, 99.6%) for artemether-lumefantrine and 96.3% (95% CI 93.1, 98.0%) for artesunate-mefloquine. Both regimens were very well tolerated with no serious adverse events observed attributable to either combination.
Conclusion
Overall, this study confirms that these two artemisinin-based combinations remain highly effective and result in equivalent therapeutic responses in the treatment of highly drug-resistant falciparum malaria.
doi:10.1186/1475-2875-4-46
PMCID: PMC1261533  PMID: 16179089
22.  EFFICACY OF ARTEQUICK® VERSUS ARTESUNATE-MEFLOQUINE IN THE TREATMENT OF ACUTE UNCOMPLICATED FALCIPARUM MALARIA IN THAILAND 
To determine the efficacy, safety and tolerability of an alternative short-course, artemisinin-based combination therapy for acute uncomplicated Plasmodium falciparum malaria, we compared Artequick®–a fixed-dosed combination of artemisinin (80 mg), piperaquine (400 mg), and primaquine (4 mg), per tablet–with a standard regimen of artesunate-mefloquine. A total of 130 patients were randomly assigned to treatment with an orally administered, once-daily, 3-day regimen of either Artequick® (Group A: 3.2 mg/kg/day of artemisinin, 16 mg/kg/day of piperaquine, and 0.16 mg/kg/day of primaquine) or artesunate-mefloquine (Group B: artesunate, 4 mg/kg/day, with mefloquine, 8 mg/kg/day). Patients receiving each regimen had a rapid clinical and parasitological response. All treatments were well tolerated, and no serious adverse effects occurred. No significant differences were found in fever- and parasite-clearance times between the two study groups. The 28-day cure rates were similarly high, at 98.5% and 100%, in groups A and B, respectively. We conclude that Artequick® was as effective and well tolerated as artesunate-mefloquine and could be used as an alternative treatment for multidrug-resistant Plasmodium falciparum malaria in Southeast Asia.
PMCID: PMC3129605  PMID: 18567436
23.  Reduced Susceptibility of Plasmodium falciparum to Artesunate in Southern Myanmar 
PLoS ONE  2013;8(3):e57689.
Background
Plasmodium falciparum resistance to artemisinins, the first line treatment for malaria worldwide, has been reported in western Cambodia. Resistance is characterized by significantly delayed clearance of parasites following artemisinin treatment. Artemisinin resistance has not previously been reported in Myanmar, which has the highest falciparum malaria burden among Southeast Asian countries.
Methods
A non-randomized, single-arm, open-label clinical trial of artesunate monotherapy (4 mg/kg daily for seven days) was conducted in adults with acute blood-smear positive P. falciparum malaria in Kawthaung, southern Myanmar. Parasite density was measured every 12 hours until two consecutive negative smears were obtained. Participants were followed weekly at the study clinic for three additional weeks. Co-primary endpoints included parasite clearance time (the time required for complete clearance of initial parasitemia), parasite clearance half-life (the time required for parasitemia to decrease by 50% based on the linear portion of the parasite clearance slope), and detectable parasitemia 72 hours after commencement of artesunate treatment. Drug pharmacokinetics were measured to rule out delayed clearance due to suboptimal drug levels.
Results
The median (range) parasite clearance half-life and time were 4.8 (2.1–9.7) and 60 (24–96) hours, respectively. The frequency distributions of parasite clearance half-life and time were bimodal, with very slow parasite clearance characteristic of the slowest-clearing Cambodian parasites (half-life longer than 6.2 hours) in approximately 1/3 of infections. Fourteen of 52 participants (26.9%) had a measurable parasitemia 72 hours after initiating artesunate treatment. Parasite clearance was not associated with drug pharmacokinetics.
Conclusions
A subset of P. falciparum infections in southern Myanmar displayed markedly delayed clearance following artemisinin treatment, suggesting either emergence of artemisinin resistance in southern Myanmar or spread to this location from its site of origin in western Cambodia. Resistance containment efforts are underway in Myanmar.
Trial Registration
Australian New Zealand Clinical Trials Registry ACTRN12610000896077
doi:10.1371/journal.pone.0057689
PMCID: PMC3592920  PMID: 23520478
24.  Monitoring for Plasmodium falciparum drug resistance to artemisinin and artesunate in Binh Phuoc Province, Vietnam: 1998-2009 
Malaria Journal  2010;9:181.
Background
Artemisinin derivatives have been used for malaria treatment in Vietnam since 1989. Reported malaria cases have decreased from 1,672,000 with 4,650 deaths in 1991, to 91,635 with 43 deaths in 2006. Current national guidelines recommend artemisinin-based combination therapy (ACT), although artesunate is still available as monotherapy through the private sector. Recent reports suggest that effectiveness of ACT and artesunate monotherapy has declined in western Cambodia. This study examined Plasmodium falciparum resistance patterns over 10 years in southwest Vietnam in infected patients treated with artemisinin compounds.
Methods
The study was conducted in two communes in Phuoc Long district, Binh Phuoc province, 100 km west of the Cambodian border. This was chosen as a likely site for emerging artemisinin resistance because of the high prevalence of P. falciparum malaria, and the length of time that artemisinin had been in use. In vivo and in vitro monitoring of P. falciparum susceptibility to anti-malarial drugs was conducted in 1998, 2001, 2004/5, and 2008/9. Patients with confirmed P. falciparum malaria received therapy with 5 or 7 days of artemisinin (1998 and 2001 respectively) or 7 days of artesunate
Results
In the four surveys, 270 patients were recruited and treated. The mean parasite clearance times differed between 1998, 2001 and 2004/5 (1.8, 2.3 and 2.1 days, P < 0.01) but not between 1998 and 2008/2009. The mean parasite clearance times were correlated with parasite density at day 0 (r = 0.4; P < 0.001). Treatment failure rates after PCR adjustment were 13.8%, 2.9%, 1.2%, and 0% respectively. Susceptibility of P. falciparum to artemisinin in in vitro tests was stable during the period, except for a rise in EC90 and EC99 in 2001.
Conclusions
This study showed stable levels of P. falciparum sensitivity to artemisinin compounds in the two sites over a ten-year period. The introduction of ACT in this area in 2003 may have protected against the development of artemisinin resistance. Adherence to the latest WHO and Vietnamese guidelines, which recommend ACT as first-line therapy in all malarious areas, and continued monitoring along the Vietnam-Cambodia border will be essential to prevent the spread of artemisinin resistance in Vietnam.
doi:10.1186/1475-2875-9-181
PMCID: PMC2904787  PMID: 20573274
25.  Pyronaridine-Artesunate versus Chloroquine in Patients with Acute Plasmodium vivax Malaria: A Randomized, Double-Blind, Non-Inferiority Trial 
PLoS ONE  2011;6(1):e14501.
Background
New antimalarials are needed for P. vivax and P. falciparum malaria. This study compared the efficacy and safety of pyronaridine-artesunate with that of chloroquine for the treatment of uncomplicated P. vivax malaria.
Methods and Findings
This phase III randomized, double-blind, non-inferiority trial included five centers across Cambodia, Thailand, India, and Indonesia. In a double-dummy design, patients (aged >3–≤60 years) with microscopically confirmed P. vivax mono-infection were randomized (1∶1) to receive pyronaridine-artesunate (target dose 7.2∶2.4 mg/kg to 13.8∶4.6 mg/kg) or chloroquine (standard dose) once daily for three days. Each treatment group included 228 randomized patients. Outcomes for the primary endpoint, Day-14 cure rate in the per-protocol population, were 99.5%, (217/218; 95%CI 97.5, 100) with pyronaridine-artesunate and 100% (209/209; 95%CI 98.3, 100) with chloroquine. Pyronaridine was non-inferior to chloroquine: treatment difference −0.5% (95%CI −2.6, 1.4), i.e., the lower limit of the 2-sided 95%CI for the treatment difference was greater than −10%. Pyronaridine-artesunate cure rates were non-inferior to chloroquine for Days 21, 28, 35 and 42. Parasite clearance time was shorter with pyronaridine-artesunate (median 23.0 h) versus chloroquine (32.0 h; p<0.0001), as was fever clearance time (median 15.9 h and 23.8 h, respectively; p = 0.0017). Kaplan-Meier estimates of post-baseline P. falciparum infection incidence until Day 42 were 2.5% with pyronaridine-artesunate, 6.1% with chloroquine (p = 0.048, log-rank test). Post-baseline P. vivax or P. falciparum infection incidence until Day 42 was 6.8% and 12.4%, respectively (p = 0.022, log rank test). There were no deaths. Adverse events occurred in 92/228 (40.4%) patients with pyronaridine-artesunate and 72/228 (31.6%) with chloroquine. Mild and transient increases in hepatic enzymes were observed for pyronaridine-artesunate.
Conclusion
Pyronaridine-artesunate efficacy in acute uncomplicated P. vivax malaria was at least that of chloroquine. As pyronaridine-artesunate is also efficacious against P. falciparum malaria, this combination has potential utility as a global antimalarial drug.
Trial registration
Clinicaltrials.gov NCT00440999
doi:10.1371/journal.pone.0014501
PMCID: PMC3022577  PMID: 21267072

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