Chloroquine efficacy for Plasmodium vivax in Myanmar in populations with high genetic diversity and moderate parasite gene flow.

BACKGROUND: Plasmodium vivax malaria remains a major public health burden in Myanmar. Resistance to chloroquine (CQ), the first-line treatment for P. vivax, has been reported in the country and has potential to undermine local control efforts. METHODS: Patients over 6 years of age with uncomplicated P. vivax mono-infection were enrolled into clinical efficacy studies in Myawaddy in 2014 and Kawthoung in 2012. Study participants received a standard dose of CQ (25 mg/kg over 3 days) followed by weekly review until day 28. Pvmdr1 copy number (CN) and microsatellite diversity were assessed on samples from the patients enrolled in the clinical study and additional cross-sectional surveys undertaken in Myawaddy and Shwegyin in 2012. RESULTS: A total of 85 patients were enrolled in the CQ clinical studies, 25 in Myawaddy and 60 in Kawthoung. One patient in Myawaddy (1.2%) had an early treatment failure and two patients (2.3%) in Kawthoung presented with late treatment failures on day 28. The day 28 efficacy was 92.0% (95% CI 71.6-97.9) in Myawaddy and 98.3% (95% CI 88.7-99.8) in Kawthoung. By day 2, 92.2% (23/25) in Myawaddy and 85.0% (51/60) in Kawthoung were aparasitaemic. Genotyping and pvmdr1 CN assessment was undertaken on 43, 52 and 46 clinical isolates from Myawaddy, Kawthoung and Shwegyin respectively. Pvmdr1 amplification was observed in 3.2% (1/31) of isolates in Myawaddy, 0% (0/49) in Kawthoung and 2.5% (1/40) in Shwegyin. Diversity was high in all sites (H E 0.855-0.876), with low inter-population differentiation (F ST 0.016-0.026, P < 0.05). CONCLUSIONS: Treatment failures after chloroquine were observed following chloroquine monotherapy, with pvmdr1 amplification present in both Myawaddy and Shwegyin. The results emphasize the importance of ongoing P. vivax drug resistance surveillance in Myanmar, particularly given the potential connectivity between parasite population at different sites.

Therapeutic efficacy and artemisinin resistance in northern Myanmar: evidence from in vivo and molecular marker studies.

BACKGROUND: In Myanmar, three types of artemisinin-based combination therapy (ACT) are recommended as first-line treatment of uncomplicated falciparum malaria: artemether-lumefantrine (AL), artesunate-mefloquine (AS + MQ), and dihydroartemisinin-piperaquine (DP). Resistance to both artemisinins and ACT partner drugs has been reported from the Greater Mekong Sub-region, and regular efficacy monitoring of the recommended ACT is conducted in Myanmar. This paper reports on results from studies to monitor the efficacy of the three forms of ACT in sentinel sites in northern Myanmar, and investigations of mutations in the Kelch13 (k13) propeller domain. METHODS: Seven therapeutic efficacy studies were conducted in 2011-12 and 2014 in three sentinel sites in Myanmar (Tamu, Muse, Tabeikkyin). Three studies were done for the evaluation of AL (204 patients), two studies for AS + MQ (119 patients) and two studies for DP (147 patients). These studies were done according to 2009 standard WHO protocol. Polymorphisms in the k13 propeller domain were examined in dried blood spots collected on day 0. The primary endpoint was adequate clinical and parasitological response (ACPR) on day 28 for AL and on day 42 for DP and AS + MQ, corrected to exclude re-infection using polymerase chain reaction (PCR) genotyping. Safety data were collected through self-reporting. RESULTS: PCR-corrected ACPR was 97.2-100% for AL, 98.6-100% for AS + MQ and 100% for DP across the study sites and years. All studies found a prevalence of k13 mutations (>440) above 23% in the day-0 samples. The F446I mutation was the most common mutation, making up 66.0% of the mutations found. Seven out of nine day-3 positive patients were infected with k13 wild type parasites. The remaining two cases with day-3 parasitaemia had the P574L mutation. CONCLUSIONS: The efficacy of AL, AS + MQ and DP remains high in northern Myanmar despite widespread evidence of k13 mutations associated with delayed parasite clearance. This study showed that already in 2012 there was a high frequency of k13 mutations in Myanmar on the border with India. The high efficacy of the recommended ACT gives confidence in the continued recommendation of the use of these treatments in Myanmar. Trial registration numbers ACTRN12611001245987 (registered 06-12-2011) and ACTRN12614000216617 (registered 28-02-2014).

Treatment Failure of Dihydroartemisinin/Piperaquine for Plasmodium falciparum Malaria, Vietnam.

We conducted a study in Binh Phuoc, Vietnam, in 2015 on the therapeutic efficacy of dihydroartemisinin/piperaquine for Plasmodium falciparum malaria. A high number of treatment failures (14/40) was found, and piperaquine resistance in Vietnam was confirmed. A change in the malaria treatment policy for Vietnam is in process.

Trends in malaria research in 11 Asian Pacific countries: an analysis of peer-reviewed publications over two decades.

BACKGROUND: Quantitative data are lacking on published malaria research. The purpose of the study is to characterize trends in malaria-related literature from 1990 to 2009 in 11 Asian-Pacific countries that are committed to malaria elimination as a national goal. METHODS: A systematic search was conducted for articles published from January 1990 to December 2009 in PubMed/MEDLINE using terms for malaria and 11 target countries (Bhutan, China, North Korea, Indonesia, Malaysia, Philippines, Solomon Islands, South Korea, Sri Lanka, Thailand and Vanuatu). The references were collated and categorized according to subject, Plasmodium species, and whether they contained original or derivative data. RESULTS: 2,700 articles published between 1990 and 2009 related to malaria in the target countries. The annual output of malaria-related papers increased linearly whereas the overall biomedical output from these countries grew exponentially. The percentage of malaria-related publications was nearly 3% (111/3741) of all biomedical publications in 1992 and decreased to less than 1% (118/12171; p < 0.001) in 2009. Thailand had the highest absolute output of malaria-related papers (n = 1211), followed by China (n = 609) and Indonesia (n = 346). Solomon Islands and Vanuatu had lower absolute numbers of publications, but both countries had the highest number of publications per capita (1.3 and 2.5 papers/1,000 population). The largest percentage of papers concerned the epidemiology and control of malaria (53%) followed by studies of drugs and drug resistance (47%). There was an increase in the proportion of articles relating to epidemiology, entomology, biology, molecular biology, pathophysiology and diagnostics from the first to the second decade, whereas the percentage of papers on drugs, clinical aspects of malaria, immunology, and social sciences decreased. CONCLUSIONS: The proportion of malaria-related publications out of the overall biomedical output from the 11 target Asian-Pacific countries is decreasing. The discovery and evaluation of new, safe and effective drugs and vaccines is paramount. In addition the elimination of malaria will require operational research to implement and scale up interventions.

Adaptive differentiation of Plasmodium falciparum populations inferred from single-nucleotide polymorphisms (SNPs) conferring drug resistance and from neutral SNPs.

BACKGROUND: Theoretical and experimental data support the geographic differentiation strategy as a valuable tool for detecting loci under selection. In the context of Plasmodium falciparum malaria, few populations have been studied, with limited genomic coverage. METHODS: We examined geographic differentiation in P. falciparum populations on the basis of 12 single-nucleotide polymorphisms (SNPs) in 4 genes encoding drug resistance determinants, 5 SNPs in 2 genes encoding antigens, and a set of 17 putatively neutral SNPs dispersed on 13 chromosomes. We sampled 326 parasite isolates representing 7 P. falciparum populations from regions with varied levels of malaria transmission (Gabon, Kenya, Madagascar, Mali, Mayotte, Haiti, and the Philippines). RESULTS: Frequencies of drug resistance alleles varied considerably among populations (mean F(ST), 0.52). In contrast, allele frequencies varied significantly less for antigenic and neutral SNPs (mean F(ST), 0.16 and 0.24, respectively). This contrasting pattern was more pronounced when only the African populations were considered. Signature of selection was detected for most of the resistant SNPs but not for the antigenic SNPs. CONCLUSION: These data further validate the utility of geographic differentiation for identifying loci under strong positive selection, such as drug resistance loci. This study also provides frequencies of molecular makers of resistance in some overlooked populations.

Efficacy and safety of a fixed-dose oral combination of pyronaridine-artesunate compared with artemether-lumefantrine in children and adults with uncomplicated Plasmodium falciparum malaria: a randomised non-inferiority trial.

BACKGROUND: There is a need for new artemisinin-based combination therapies that are convenient, effective, and safe. We compared the efficacy and safety of pyronaridine-artesunate with that of artemether-lumefantrine for treatment of uncomplicated P falciparum malaria. METHODS: This phase 3, parallel-group, double-blind, randomised, non-inferiority trial was undertaken in seven sites in Africa and three sites in southeast Asia. In a double-dummy design, patients aged 3-60 years with uncomplicated P falciparum malaria were randomly assigned in a 2:1 ratio to receive pyronaridine-artesunate once a day or artemether-lumefantrine twice a day, orally for 3 days, plus respective placebo. Randomisation was done by computer-generated randomisation sequence in blocks of nine by study centre. Intervention tablets contained 180 mg pyronaridine and 60 mg artesunate; control tablets contained 20 mg artemether and 120 mg lumefantrine. Both treatments were given according to bodyweight. The primary efficacy outcome was PCR-corrected adequate clinical and parasitological response (ACPR) rate at day 28 in the per-protocol population. Non-inferiority was shown if the lower limit of the two-sided 95% CI for the difference between groups was greater than -5%. This study is registered with ClinicalTrials.gov, number NCT00422084. FINDINGS: 1272 patients were randomly assigned to treatment (pyronaridine-artesunate, n=849; artemether-lumefantrine, n=423). The per-protocol population consisted of 784 patients in the pyronaridine-artesunate group and 386 patients in the artemether-lumefantrine group. PCR-corrected ACPR rate at day 28 was 99.5% (780 patients; 95% CI 98.7-99.9) in the pyronaridine-artesunate group and 99.2% (383 patients; 95% CI 97.7-99.8) in the artemether-lumefantrine group (treatment difference 0.3%, 95% CI -0.7 to 1.8; p=0.578). There were 509 (60.0%) adverse events in 849 patients assigned to pyronaridine-artesunate and 241 (57.0%) in 423 patients assigned to artemether-lumefantrine. The most frequent drug-related adverse event was eosinophilia (pyronaridine-artesunate, 53 events [6.2%]; artemether-lumefantrine 24 events [5.7%]). 21 (2.5%) patients in the pyronaridine-artesunate group and seven (1.7%) in the artemether-lumefantrine group discontinued study drugs or were withdrawn from the study. Mild and transient increases in alanine aminotransferase and aspartate aminotransferase concentrations were seen in the pyronaridine-artesunate group but not in the artemether-lumefantrine group. INTERPRETATION: Efficacy of pyronaridine-artesunate was non-inferior to that of artemether-lumefantrine for treatment of uncomplicated falciparum malaria. Pyronaridine-artesunate should be considered for inclusion in malaria treatment programmes. FUNDING: Shin Poong Pharmaceutical and the Medicines for Malaria Venture.

Pharmacokinetics of sequential and simultaneous treatment with the combination chloroquine and sulfadoxine-pyrimethamine in acute uncomplicated Plasmodium falciparum malaria in the Philippines.

The efficacy and kinetics of the combination chloroquine plus sulfadoxine-pyrimethamine (CQ + SP), given sequentially and simultaneously, were investigated in 32 patients with acute uncomplicated Plasmodium falciparum malaria in Palawan Island, the Philippines. Group 1 with 11 patients received oral CQ 25 mg/kg bw over 3 days followed by a single dose of SP (three tablets 250 mg S + 25 mg P) on Day 4 (CQ0 + SP4). Group 2 with 21 patients received a loading dose of CQ 10 mg/kg plus a single dose of SP three tablets on Day 0, and doses of CQ on Days 1 and 2 (CQ0 + SP0). Patients were followed-up for 28 days until after the clinical and parasitological remission of the disease. Serum samples for CQ, des-ethylchloroquine (DCQ), S and P levels were assayed by high-pressure liquid chromatography with UV and spectrofluorometric detection (HPLC-SF) to determine effective therapeutic concentrations achieved. Parasite and fever clearance times (PCT and FCT) in Group 1 were 48 and 33.5 h, respectively, and 39 and 24 h in Group 2. The parasite elimination half-life (pt1/2) in the CQ + SP0 group was 2.5 h, significantly shorter than the CQ + SP4 group of 5.7 h (P=0.006). Late-treatment failures (R I) were observed in 2/11 patients in Group 1 and in 2/21 patients in Group 2. Serum CQ and DCQ concentrations were effectively adequate. Group 1 pharmacokinetic parameters showed a median maximum concentration (Cmax), area under the curve (AUC) and elimination half-life (t1/2) of 285 ng/ml, 2299 day ng/ml and 5.7 days for CQ, and 89 ng/ml 1845 day ng/ml and 7.3 days for DCQ, respectively. SP was not assayed in Group 1 because of very limited time points. In Group 2, the median Cmax, AUC and t1/2 for CQ and DCQ were at 283 ng/ml 1980 day ng/ml and 5.9 days for CQ and 220 ng/ml, 2680 day ng/ml and 8.5 days for DCQ, respectively. For S and P, the median Cmax, AUC and t1/2 were at 169 microg/ml, 2758 day ng/ml and 10.9 days for sulfadoxine, and 591 ng/ml, 3029 day ng/ml and 2.9 days for pyrimethamine, respectively. Both regimens were well tolerated with a minimum of side-effects, mainly nausea and vomiting. The combination CQ + SP administered simultaneously on Day 0 is more efficacious than when administered sequentially. In the absence of an alternative treatment for acute uncomplicated malaria, this combination is well tolerated, and has an advantage over CQ or SP monotherapy, especially in countries where one drug is still highly effective.