Baseline data of parasite clearance in patients with falciparum malaria treated with an artemisinin derivative: an individual patient data meta-analysis.

BACKGROUND: Artemisinin resistance in Plasmodium falciparum manifests as slow parasite clearance but this measure is also influenced by host immunity, initial parasite biomass and partner drug efficacy. This study collated data from clinical trials of artemisinin derivatives in falciparum malaria with frequent parasite counts to provide reference parasite clearance estimates stratified by location, treatment and time, to examine host factors affecting parasite clearance, and to assess the relationships between parasite clearance and risk of recrudescence during follow-up. METHODS: Data from 24 studies, conducted from 1996 to 2013, with frequent parasite counts were pooled. Parasite clearance half-life (PC1/2) was estimated using the WWARN Parasite Clearance Estimator. Random effects regression models accounting for study and site heterogeneity were used to explore factors affecting PC1/2 and risk of recrudescence within areas with reported delayed parasite clearance (western Cambodia, western Thailand after 2000, southern Vietnam, southern Myanmar) and in all other areas where parasite populations are artemisinin sensitive. RESULTS: PC1/2 was estimated in 6975 patients, 3288 of whom also had treatment outcomes evaluate d during 28-63 days follow-up, with 93 (2.8 %) PCR-confirmed recrudescences. In areas with artemisinin-sensitive parasites, the median PC1/2 following three-day artesunate treatment (4 mg/kg/day) ranged from 1.8 to 3.0 h and the proportion of patients with PC1/2 >5 h from 0 to 10 %. Artesunate doses of 4 mg/kg/day decreased PC1/2 by 8.1 % (95 % CI 3.2-12.6) compared to 2 mg/kg/day, except in populations with delayed parasite clearance. PC1/2 was longer in children and in patients with fever or anaemia at enrolment. Long PC1/2 (HR = 2.91, 95 % CI 1.95-4.34 for twofold increase, p < 0.001) and high initial parasitaemia (HR = 2.23, 95 % CI 1.44-3.45 for tenfold increase, p < 0.001) were associated independently with an increased risk of recrudescence. In western Cambodia, the region with the highest prevalence of artemisinin resistance, there was no evidence for increasing PC1/2 since 2007. CONCLUSIONS: Several factors affect PC1/2. As substantial heterogeneity in parasite clearance exists between locations, early detection of artemisinin resistance requires reference PC1/2 data. Studies with frequent parasite count measurements to characterize PC1/2 should be encouraged. In western Cambodia, where PC1/2 values are longest, there is no evidence for recent emergence of higher levels of artemisinin resistance.

Chlorproguanil-dapsone-artesunate versus chlorproguanil-dapsone: a randomized, double-blind, phase III trial in African children, adolescents, and adults with uncomplicated Plasmodium falciparum malaria.

This multi-center, randomized, parallel-group, double-blind, double-dummy study compared the efficacy and safety of chlorproguanil-dapsone-artesunate (CDA) and chlorproguanil-dapsone (CPG-DDS) in the treatment of falciparum malaria in Africa (Burkina Faso, Ghana, Mali, Nigeria). Six hundred patients (>or= 1 year of age) received CDA 2.0/2.5/4.0 mg/kg, and 292 CPG-DDS 2.0/2.5 mg/kg, once daily for 3 days. Day 28 parasitologic cure rate (polymerase chain reaction [PCR]-corrected, per-protocol population) was 89.1% (416/467) for CDA, non-inferior but also superior to CPG-DDS, 83.0% (176/212) (treatment difference 6.1%; 95% confidence interval [CI] 0.3, 11.9). Glucose-6-phosphate dehydrogenase (G6PD) genotype was available for 844/892 (95%) patients. Occurrences of a composite hemoglobin safety endpoint (hemoglobin drop >or= 40 g/L or >or= 40% versus baseline, hemoglobin < 50 g/L, or blood transfusion) were CDA 13/44 (30%), CPG-DDS 7/24 (29%) in G6PD-deficient patients versus CDA 4/448 (< 1%), CPG-DDS 6/221 (3%) in G6PD-normal patients. No deaths occurred. CDA was more efficacious than CPG-DDS. However, the hemolytic potential in G6PD-deficient patients does not support further development of CDA.

Chlorproguanil-dapsone-artesunate versus artemether-lumefantrine: a randomized, double-blind phase III trial in African children and adolescents with uncomplicated Plasmodium falciparum malaria.

BACKGROUND: Chlorproguanil-dapsone-artesunate (CDA) was developed as an affordable, simple, fixed-dose artemisinin-based combination therapy for use in Africa. This trial was a randomized parallel-group, double-blind, double-dummy study to compare CDA and artemether-lumefantrine (AL) efficacy in uncomplicated Plasmodium falciparum malaria and further define the CDA safety profile, particularly its hematological safety in glucose-6-phosphate dehydrogenase (G6PD) -deficient patients. METHODS AND FINDINGS: The trial was conducted at medical centers at 11 sites in five African countries between June 2006 and August 2007. 1372 patients (> or =1 to <15 years old, median age 3 years) with acute uncomplicated P. falciparum malaria were randomized (2:1) to receive CDA 2/2.5/4 mg/kg once daily for three days (N = 914) or six-doses of AL over three days (N = 458). Non-inferiority of CDA versus AL for efficacy was evaluated in the Day 28 per-protocol (PP) population using parasitological cure (polymerase chain reaction [PCR]-corrected). Cure rates were 94.1% (703/747) for CDA and 97.4% (369/379) for AL (treatment difference -3.3%, 95%CI -5.6, -0.9). CDA was non-inferior to AL, but there was simultaneous superiority of AL (upper 95%CI limit <0). Adequate clinical and parasitological response at Day 28 (uncorrected for reinfection) was 79% (604/765) with CDA and 83% (315/381) with AL. In patients with a G6PD-deficient genotype (94/603 [16%] hemizygous males, 22/598 [4%] homozygous females), CDA had the propensity to cause severe and clinically concerning hemoglobin decreases: the mean hemoglobin nadir was 75 g/L (95%CI 71, 79) at Day 7 versus 97 g/L (95%CI 91, 102) for AL. There were three deaths, unrelated to study medication (two with CDA, one with AL). CONCLUSIONS: Although parasitologically effective at Day 28, the hemolytic potential of CDA in G6PD-deficient patients makes it unsuitable for use in a public health setting in Africa. TRIAL REGISTRATION: ClinicalTrials.Gov NCT00344006.

Measurement of adherence, drug concentrations and the effectiveness of artemether-lumefantrine, chlorproguanil-dapsone or sulphadoxine-pyrimethamine in the treatment of uncomplicated malaria in Malawi.

BACKGROUND: Sulphadoxine-pyrimethamine (SP) is the only single dose therapy for uncomplicated malaria, but there is widespread resistance. At the time of this study, artemether-lumefantrine (AL) and chlorproguanil-dapsone (CPD), both multi-dose regimes, were considered possible alternatives to SP in Malawi. The aim of this study was to investigate the impact of poor adherence on the effectiveness of AL and CPD. METHODS: Children > or =12 months and adults with uncomplicated malaria were randomized to receive AL, CPD or SP. Adherence was measured using a questionnaire and electronic monitoring devices, MEMS, pill bottles that recorded the date and time of opening. Day-7 plasma dapsone or lumefantrine concentrations were measured to examine their relationship with adherence and clinical response. RESULTS: 841 patients were recruited. The day-28 adequate clinical and parasitological response (ACPR) rates, using intention to treat analysis (missing data treated as failure), were AL 85.2%, CPD 63.7% and SP 50%. ACPR rates for AL were higher than CPD or SP on days 28 and 42 (p < or = 0.002 for all comparisons). CPD was more effective than SP on day-28 (p = 0.01), but not day-42.Very high adherence was reported using the questionnaire, 100% for AL treated patients and 99.2% for the CPD group. Only three CPD participants admitted missing any doses. 164/181 (90.6%) of CPD treated patients took all their doses out of the MEMS container and they were more likely to have a day-28 ACPR than those who did not take all their medication out of the container, p = 0.024. Only 7/87 (8%) AL treated patients did not take all of their doses out of their MEMS container and none had treatment failure.Median day-7 dapsone concentrations were higher in CPD treated patients with ACPR than in treatment failures, p = 0.012. There were no differences in day-7 dapsone or lumefantrine concentrations between those who took all their doses from the MEMS container and those who did not. A day-7 lumefantrine concentration reported to be predictive of AL treatment failure in Thailand was not useful in this population; only one of 16 participants with a concentration below this threshold (175 ng/ml) had treatment failure. CONCLUSION: This study provides reassurance of the effectiveness of AL, even with unsupervised dosing, as it is rolled out across sub-Saharan Africa. Self-reported adherence appears to be an unreliable measure of adherence in this population.

Pharmacokinetics of chlorproguanil, dapsone, artesunate and their major metabolites in patients during treatment of acute uncomplicated Plasmodium falciparum malaria.

OBJECTIVE: Chlorproguanil (CPG)-dapsone (DDS)-artesunate was in development for the treatment of uncomplicated Plasmodium falciparum malaria. The pharmacokinetics of CPG, DDS, artesunate and their metabolites chlorcycloguanil (CCG), monoacetyl dapsone (MADDS) and dihydroartemisinin (DHA) were investigated in patients with P. falciparum given CPG-DDS alone or plus artesunate. METHODS: Adult patients from Malawi and The Gambia taking part in a phase II clinical trial were randomised to receive a 3-day treatment of CPG-DDS alone (2/2.5 mg/kg/day) or plus 1, 2 or 4 mg/kg/day artesunate. Blood samples for pharmacokinetic analysis were collected up to 24 h post-first dose. RESULTS: The pharmacokinetic analysis included 115 patients. For CPG, there was no significant effect of artesunate on C(max) or AUC(0-24), except the 90% confidence interval (CI) for AUC(0-24) for the 4 mg/kg artesunate dose was slightly below that for the standard bioequivalence range (90% CI 0.78, 1.11); this was not considered clinically relevant. Artesunate increased the CCG AUC(0-24) by 6-17% and C(max) by 0-16%. Artesunate had no significant effect on the rate or extent of absorption of DDS. For MADDS, artesunate increased the AUC(0-24) by 13-47% and C(max) by 8-45%. For 1, 2 and 4 mg/kg artesunate dosing, artesunate AUC(0-infinity) was 64.6, 151 and 400 ng.h/ml and C(max) 48.9, 106 and 224 ng/ml respectively; DHA AUC(0-infinity) was 538, 1,445 and 3,837 ng.h/ml and C(max) 228, 581 and 1,414 ng/ml respectively. Using a power model, the point estimates of slope were greater than 1 for artesunate AUC(0-t) by 16% and C(max) by 5% and for DHA by 39 and 21% respectively. CONCLUSION: Artesunate did not significantly affect CPG or DDS pharmacokinetics. For CCG and MADDS, small to moderate increases in exposure with artesunate dosing were observed. There was a greater than proportional increase in artesunate and DHA exposure with increasing artesunate dose. These effects are not considered to be clinically relevant. It should be noted that the CPG-DDS-artesunate programme has now been stopped following unacceptable haematological toxicity in patients with glucose-6-phosphate dehydrogenase deficiency during a phase III trial. In addition, the CPG-DDS combination has been withdrawn from clinical use.

Synthesis, antimalarial activity, and preclinical pharmacology of a novel series of 4'-fluoro and 4'-chloro analogues of amodiaquine. Identification of a suitable "back-up" compound for N-tert-butyl isoquine.

On the basis of a mechanistic understanding of the toxicity of the 4-aminoquinoline amodiaquine (1b), three series of amodiaquine analogues have been prepared where the 4-aminophenol "metabolic alert" has been modified by replacement of the 4'-hydroxy group with a hydrogen, fluorine, or chlorine atom. Following antimalarial assessment and studies on mechanism of action, two candidates were selected for detailed ADME studies and in vitro and in vivo toxicological assessment. 4'-Fluoro-N-tert-butylamodiaquine (2k) was subsequently identified as a candidate for further development studies based on potent activity versus chloroquine-sensitive and resistant parasites, moderate to excellent oral bioavailability, low toxicity in in vitro studies, and an acceptable safety profile.

Candidate selection and preclinical evaluation of N-tert-butyl isoquine (GSK369796), an affordable and effective 4-aminoquinoline antimalarial for the 21st century.

N-tert-Butyl isoquine (4) (GSK369796) is a 4-aminoquinoline drug candidate selected and developed as part of a public-private partnership between academics at Liverpool, MMV, and GSK pharmaceuticals. This molecule was rationally designed based on chemical, toxicological, pharmacokinetic, and pharmacodynamic considerations and was selected based on excellent activity against Plasmodium falciparum in vitro and rodent malaria parasites in vivo. The optimized chemistry delivered this novel synthetic quinoline in a two-step procedure from cheap and readily available starting materials. The molecule has a full industry standard preclinical development program allowing first into humans to proceed. Employing chloroquine (1) and amodiaquine (2) as comparator molecules in the preclinical plan, the first preclinical dossier of pharmacokinetic, toxicity, and safety pharmacology has also been established for the 4-aminoquinoline antimalarial class. These studies have revealed preclinical liabilities that have never translated into the human experience. This has resulted in the availability of critical information to other drug development teams interested in developing antimalarials within this class.

Plasmodium falciparum strains harboring dihydrofolate reductase with the I164L mutation are absent in Malawi and Zambia even under antifolate drug pressure.

The Plasmodium falciparum dihydrofolate reductase (PfDHFR) enzyme is the target of pyrimethamine, a component of the antimalarial pyrimethamine-sulfadoxine. Resistance to this drug is associated primarily with mutations in the Pfdhfr gene. The I164L mutant allele is of particular interest, because strains possessing this mutation are highly resistant to pyrimethamine and to chlorproguanil, a component of chlorproguanil-dapsone. A recent study from Malawi reported this mutation at a prevalence of 4.7% in parasites from human immunodeficiency virus-positive pregnant women by using a real-time PCR method. These observations have huge implications for the use of pyrimethamine-sulfadoxine, chlorproguanil-dapsone, and future antifolate-artemisinin combinations in Africa. It was imperative that this finding be rigorously tested. We identified a number of critical limitations in the original genotyping strategy. Using a refined and validated real-time PCR strategy, we report here that this mutation was absent in 158 isolates from Malawi and 42 isolates from Zambia collected between 2003 and 2005.

Open-label comparative clinical study of chlorproguanil-dapsone fixed dose combination (Lapdap) alone or with three different doses of artesunate for uncomplicated Plasmodium falciparum malaria.

UNLABELLED: The objective of this study was to determine the appropriate dose of artesunate for use in a fixed dose combination therapy with chlorproguanil-dapsone (CPG-DDS) for the treatment of uncomplicated falciparum malaria. METHODS: Open-label clinical trial comparing CPG-DDS alone or with artesunate 4, 2, or 1 mg/kg at medical centers in Blantyre, Malawi and Farafenni, The Gambia. The trial was conducted between June 2002 and February 2005, including 116 adults (median age 27 years) and 107 children (median age 38 months) with acute uncomplicated Plasmodium falciparum malaria. Subjects were randomized into 4 groups to receive CPG-DDS alone or plus 4, 2 or 1 mg/kg of artesunate once daily for 3 days. Assessments took place on Days 0-3 in hospital and follow-up on Days 7 and 14 as out-patients. Efficacy was evaluated in the Day 3 per-protocol (PP) population using mean time to reduce baseline parasitemia by 90% (PC90). A number of secondary outcomes were also included. Appropriate artesunate dose was determined using a pre-defined decision matrix based on primary and secondary outcomes. Treatment emergent adverse events were recorded from clinical assessments and blood parameters. Safety was evaluated in the intent to treat (ITT) population. RESULTS: In the Day 3 PP population for the adult group (N = 85), mean time to PC90 was 19.1 h in the CPG-DDS group, significantly longer than for the +artesunate 1 mg/kg (12.5 h; treatment difference -6.6 h [95%CI -11.8, -1.5]), 2 mg/kg (10.7 h; -8.4 h [95%CI -13.6, -3.2]) and 4 mg/kg (10.3 h; -8.7 h [95%CI -14.1, -3.2]) groups. For children in the Day 3 PP population (N = 92), mean time to PC90 was 21.1 h in the CPG-DDS group, similar to the +artesunate 1 mg/kg group (17.7 h; -3.3 h [95%CI -8.6, 2.0]), though the +artesunate 2 mg/kg and 4 mg/kg groups had significantly shorter mean times to PC90 versus CPG-DDS; 14.4 h (treatment difference -6.4 h [95%CI -11.7, -1.0]) and 12.8 h (-7.4 h [95%CI -12.9, -1.8]), respectively. An analysis of mean time to PC90 for the Day 14 PP and ITT populations was consistent with the primary analysis. Treatment emergent, drug-related adverse events were experienced in 35.3% (41/116) of adults and 70.1% (75/107) of children; mostly hematological and gastroenterological. The nature and incidence of adverse events was similar between the groups. No dose-related changes in laboratory parameters were observed. Nine serious adverse events due to any cause occurred in five subjects including two cases of hemolysis believed to be associated with drug treatment (one adult, one child). One adult died of anaphylactic shock, not associated with investigational therapy. CONCLUSIONS: CPG-DDS plus artesunate demonstrated advantages over CPG-DDS alone for the primary efficacy endpoint (mean time to PC90) except in children for the 1 mg/kg artesunate dose. Based on a pre-defined decision matrix, the primary endpoint in the child group supported an artesunate dose of 4 mg/kg. Secondary endpoints also supported a 4 mg/kg artesunate dose to take forward into the remainder of the development program. TRIAL REGISTRATION: ClinicalTrials.gov NCT00519467.

Sulfadoxine-pyrimethamine-based combinations for malaria: a randomised blinded trial to compare efficacy, safety and selection of resistance in Malawi.

BACKGROUND: In Malawi, there has been a return of Plasmodium falciparum sensitivity to chloroquine (CQ) since sulfadoxine-pyrimethamine (SP) replaced CQ as first line treatment for uncomplicated malaria. When used for prophylaxis, Amodiaquine (AQ) was associated with agranulocytosis but is considered safe for treatment and is increasingly being used in Africa. Here we compare the efficacy, safety and selection of resistance using SP or CQ+SP or artesunate (ART)+SP or AQ+SP for the treatment of uncomplicated falciparum malaria. METHODOLOGY AND FINDINGS: 455 children aged 1-5 years were recruited into a double-blinded randomised trial comparing SP to the three combination therapies. Using intention to treat analysis with missing outcomes treated as successes, and without adjustment to distinguish recrudescence from new infections, the day 28 adequate clinical and parasitological response (ACPR) rate for SP was 25%, inferior to each of the three combination therapies (p<0.001). AQ+SP had an ACPR rate of 97%, higher than CQ+SP (81%) and ART+SP (70%), p<0.001. Nineteen children developed a neutropenia of

Rare, highly pyrimethamine-resistant alleles of the Plasmodium falciparum dihydrofolate reductase gene from 5 African sites.

In eastern and southern Africa, there has been a rapid increase in the prevalence of alleles with mutations in the Plasmodium falciparum dihydrofolate reductase gene (dhfr) associated with increased risk of clinical failure of sulfadoxine-pyrimethamine (S/P). Molecular methods for surveillance of these mutations are now widespread, but the usual analysis detects only the most prevalent allele in a polyclonal sample. We used a yeast-expression system to identify rare, highly pyrimethamine-resistant alleles of dhfr in isolates from 5 African countries--Kenya, Tanzania, Malawi, Gabon, and Nigeria. Only the isolates from Nigeria yielded significant numbers of novel resistant alleles, and only 1 of the alleles from any location showed a >3-fold increase in resistance to S/P or to chlorproguanil-dapsone. Overall, these results suggest that dhfr alleles that confer high levels of resistance to antifolates are rare, even in eastern and southern Africa, where pyrimethamine has been intensively used.

The difference between effectiveness and efficacy of antimalarial drugs in Kenya.

OBJECTIVE: To demonstrate the difference between effectiveness and efficacy of antimalarial (AM) drugs in Kenya. METHODS: We undertook a series of linked surveys in four districts of Kenya between 2001 and 2002 on (i) community usage of nationally recommended first- and second-line AM drugs; (ii) commonly stocked AM products in the retail and wholesale sectors; and (iii) quality of the most commonly available first- and second-line AM products. These were combined with estimates of adherence and clinical efficacy to derive overall drug effectiveness. RESULTS: The overall modelled effectiveness for sulphadoxine-pyrimethamine (SP) was estimated to be 62% compared with 85% for reported SP clinical efficacy. For amodiaquine the modelled effectiveness was 48% compared with 99% reported efficacy during the same time period. CONCLUSIONS: The quality of AM products and patient adherence to dosage regimens are important determinants of drug effectiveness, and should be measured alongside clinical efficacy. Post-registration measures to regulate drug quality and improve patient adherence would contribute significantly to AM drug performance.

Therapeutic potential of folate uptake inhibition in Plasmodium falciparum.

Plasmodium falciparum parasites resistant to the combination sulfadoxine-pyrimethamine are spreading in Africa, particularly in East Africa. This is a matter of concern because there are no other affordable drugs available. This article provides the evidence indicating that sulfadoxine-pyrimethamine resistance can be reversed in vitro and discusses how this information might be exploited to extend the therapeutic lifetime of sulfadoxine-pyrimethamine in vivo.

Isoquine and related amodiaquine analogues: a new generation of improved 4-aminoquinoline antimalarials.

Amodiaquine (AQ) (2) is a 4-aminoquinoline antimalarial that can cause adverse side effects including agranulocytosis and liver damage. The observed drug toxicity is believed to involve the formation of an electrophilic metabolite, amodiaquine quinoneimine (AQQI), which can bind to cellular macromolecules and initiate hypersensitivity reactions. We proposed that interchange of the 3' hydroxyl and the 4' Mannich side-chain function of amodiaquine would provide a new series of analogues that cannot form toxic quinoneimine metabolites via cytochrome P450-mediated metabolism. By a simple two-step procedure, 10 isomeric amodiaquine analogues were prepared and subsequently examined against the chloroquine resistant K1 and sensitive HB3 strains of Plasmodium falciparum in vitro. Several analogues displayed potent antimalarial activity against both strains. On the basis of the results of in vitro testing, isoquine (ISQ1 (3a)) (IC(50) = 6.01 nM +/- 8.0 versus K1 strain), the direct isomer of amodiaquine, was selected for in vivo antimalarial assessment. The potent in vitro antimalarial activity of isoquine was translated into excellent oral in vivo ED(50) activity of 1.6 and 3.7 mg/kg against the P. yoelii NS strain compared to 7.9 and 7.4 mg/kg for amodiaquine. Subsequent metabolism studies in the rat model demonstrated that isoquine does not undergo in vivo bioactivation, as evidenced by the complete lack of glutathione metabolites in bile. In sharp contrast to amodiaquine, isoquine (and Phase I metabolites) undergoes clearance by Phase II glucuronidation. On the basis of these promising initial studies, isoquine (ISQ1 (3a)) represents a new second generation lead worthy of further investigation as a cost-effective and potentially safer alternative to amodiaquine.

The effect of quinine on the electroretinograms of children with pediatric cerebral malaria.

To investigate the effects of quinine on the electroretinograms (ERGs) of children with cerebral malaria (CM), we recruited subjects during a single malaria season in Blantyre, Malawi. Seventy ERG investigations were performed, on 34 children with CM. Time recorded from completion of the most recent quinine infusion was termed "quinine elapsed time" (QET). In a subgroup of 16 children, whole-blood quinine concentrations were estimated in a sample of capillary blood, for validation. A significant positive association was found between QET and both maximal-response A-wave amplitude (MRAWA; P=.03) and cone A-wave amplitude (P=.04). Longitudinal analysis demonstrated a significant trend of increasing MRAWA with increasing QET (P=.03). Parenteral quinine administered in therapeutic doses to a pediatric population appears to cause a transient depression in photoreceptor function. No evidence of ocular quinine toxicity was found at the therapeutic doses used.

Clinical status and implications of antimalarial drug resistance.

Africa carries the greatest burden of disease caused by Plasmodium falciparum, and we can expect this burden to rise in the near future, mainly because of drug resistance. Although effective drugs are available (such as artemether-lumefantrine, mefloquine, atovaquone-proguanil and halofantrine) they are uniformly too expensive for routine use. Affordable options include chloroquine plus sulfadoxine-pyrimethamine (SP), amodiaquine (alone or in combination with SP) and chlorproguanil-dapsone. Artemisinin combination therapy may offer considerable advantages over alternative therapies, but its introduction faces considerable logistic difficulty.

Molecular markers for failure of sulfadoxine-pyrimethamine and chlorproguanil-dapsone treatment of Plasmodium falciparum malaria.

Molecular assays for monitoring sulfadoxine-pyrimethamine-resistant Plasmodium falciparum have not been implemented because of the genetic and statistical complexity of the parasite mutations that confer resistance and their relation to treatment outcomes. This study analyzed pretreatment dihydrofolate reductase (DHFR) and dihydropteroate synthase (DHPS) genotypes and treatment outcomes in a double-blind, placebo-controlled trial of sulfadoxine-pyrimethamine and chlorproguanil-dapsone treatment for uncomplicated P. falciparum malaria. Multiple logistic regression was used to identify mutations that were predictive of treatment failure and to identify interactions and confounding factors. Infections caused by parasites with 3 DHFR mutations and 2 DHPS mutations (the "quintuple mutant") were associated with sulfadoxine-pyrimethamine treatment failure but not with chlorproguanil-dapsone treatment failure. The presence of a single DHFR mutation (Arg-59) with a single DHPS mutation (Glu-540) accurately predicted the presence of the quintuple mutant. If this model is validated in other populations, it will finally be possible to use molecular markers for surveillance of antifolate-resistant P. falciparum malaria in Africa.

Pharmacology of absorption and distribution: optimal use of antimalarial drugs in the treatment of severe falciparum malaria in Kenya.

Since 1989, a project at the KEMRI CRC Unit at Kilifi has focused on the design of appropriate and practicable regimens for the treatment of severe falciparum malaria. Initially, there was no data describing the absorption, distribution and elimination of quinine in Kenyan children, who constitute the great majority of patients. Pharmacokinetic studies were conducted to define these variables, which formed the basis for the design of appropriate and practicable treatment regimens. Even with optimal clinical management, the majority is high in cases of severe malaria treated with quinine at Kilifi. Alternative drugs have been studied in a search for a therapeutic regimen that will further reduce mortality.