High therapeutic efficacy of artemether-lumefantrine and dihydroartemisinin-piperaquine for the treatment of uncomplicated falciparum malaria in Somalia

Screening for antifolate and artemisinin resistance in Plasmodium falciparum dried-blood spots from three hospitals of Eritrea

Background

Antimalarial drug resistance is a major challenge hampering malaria control and elimination. About three-quarters of Eritrea's population resides in the malaria-endemic western lowlands of the country. Plasmodium falciparum, the leading causative parasite species, has developed resistance to basically all antimalarials. Continued surveillance of drug resistance using genetic markers provides important molecular data for treatment policies which complements clinical studies, and strengthens control efforts. This study sought to genotype point mutations associated with P. falciparum resistance to sulfadoxine-pyrimethamine and artemisinin, in dried-blood spots from three hospitals in the western lowlands of Eritrea.

Methods

Dried-blood spot samples were collected from patients visiting Adi Quala, Keren and Gash Barka Hospitals, between July and October, 2014. The patients were followed up after treatment with first line artesunate-amodiaquine, and dried-blood spots were collected on day three after treatment. Nested polymerase chain reaction and Sanger sequencing techniques were employed to genotype point mutations in the Pfdhfr (PF3D7_0417200), Pfdhps (PF3D7_0810800) and PfK13 (PF3D7_1343700) partial gene regions.

Results

Sequence data analyses of PCR-positive isolates found wild-type artemisinin haplotypes associated with resistance (Y493Y, R539R, I543I) in three isolates, whereas four mutant antifolate haplotypes associated with resistance were observed in six isolates. These included the triple-mutant Pfdhfr (S108N, C59R, N51I) haplotype, the double-mutant Pfdhfr (N51I, S108N) haplotype, the single-mutant Pfdhfr (K540E) haplotype, and the mixed-mutant Pfdhfr-Pfdhps (S108N, N51I + K540E) haplotype. Other findings observed were, a rare non-synonymous Pfdhfr V45A mutation in four isolates, and a synonymous Pfdhps R449R in one isolate.

Conclusions

The mutant antifolate haplotypes observed indicate a likely existence of full SP resistance. Further studies can be carried out to estimate the prevalence of SP resistance. The wild-type artemisinin haplotypes observed suggest artemisinin is still an effective treatment. Continuous monitoring of point mutations associated with delayed parasite clearance in ART clinical studies is recommended.

Progressive heterogeneity of enlarged and irregularly shaped apicoplasts in P. falciparum persister blood stages after drug treatment

Morphological modifications and shifts in organelle relationships are hallmarks of dormancy in eukaryotic cells. Communications between altered mitochondria and nuclei are associated with metabolic quiescence of cancer cells that can survive chemotherapy. In plants, changes in the pathways between nuclei, mitochondria, and chloroplasts are associated with cold stress and bud dormancy. Plasmodium falciparum parasites, the deadliest agent of malaria in humans, contain a chloroplast-like organelle (apicoplast) derived from an ancient photosynthetic symbiont. Antimalarial treatments can fail because a small fraction of the blood stage parasites enter dormancy and recrudesce after drug exposure. Altered mitochondrial-nuclear interactions in these persisters have been described for P. falciparum, but interactions of the apicoplast remained to be characterized. In the present study, we examined the apicoplasts of dormant persisters obtained after exposure to dihydroartemisinin (a first-line antimalarial drug) followed by sorbitol treatment, or after exposure to sorbitol treatment alone. As previously observed, the mitochondrion of persisters was consistently enlarged and in close association with the nucleus. In contrast, the apicoplast varied from compact and oblate, like those of active ring stage parasites, to enlarged and irregularly shaped. Enlarged apicoplasts became more prevalent later in dormancy, but regular size apicoplasts subsequently predominated when actively replicating parasites recrudesced. All three organelles, nucleus, mitochondrion, and apicoplast, became closer during dormancy. Understanding their relationships in erythrocytic-stage persisters may lead to new strategies to prevent recrudescences and protect the future of malaria chemotherapy.

An overview on the antimalarial activity of 1,2,4-trioxanes, 1,2,4-trioxolanes and 1,2,4,5-tetraoxanes

The demand for novel, fast-acting, and effective antimalarial medications is increasing exponentially. Multidrug resistant forms of malarial parasites, which are rapidly spreading, pose a serious threat to global health. Drug resistance has been addressed using a variety of strategies, such as targeted therapies, the hybrid drug idea, the development of advanced analogues of pre-existing drugs, and the hybrid model of resistant strains control mechanisms. Additionally, the demand for discovering new potent drugs grows due to the prolonged life cycle of conventional therapy brought on by the emergence of resistant strains and ongoing changes in existing therapies. The 1,2,4-trioxane ring system in artemisinin (ART) is the most significant endoperoxide structural scaffold and is thought to be the key pharmacophoric moiety required for the pharmacodynamic potential of endoperoxide-based antimalarials. Several derivatives of artemisinin have also been found as potential treatments for multidrug-resistant strain in this area. Many 1,2,4-trioxanes, 1,2,4-trioxolanes, and 1,2,4,5-tetraoxanes derivatives have been synthesised as a result, and many of these have shown promise antimalarial activity both in vivo and in vitro against Plasmodium parasites. As a consequence, efforts to develop a functionally straight-forward, less expensive, and vastly more effective synthetic pathway to trioxanes continue. This study aims to give a thorough examination of the biological properties and mode of action of endoperoxide compounds derived from 1,2,4-trioxane-based functional scaffolds. The present system of 1,2,4-trioxane, 1,2,4-trioxolane, and 1,2,4,5-tetraoxane compounds and dimers with potentially antimalarial activity will be highlighted in this systematic review (January 1963-December 2022).

Antimalarial drug efficacy and resistance in malaria-endemic countries in HANMAT-PIAM_net countries of the Eastern Mediterranean Region 2016-2020: Clinical and genetic studies

INTRODUCTION

The World Health Organization recommends regular monitoring of the efficacy of nationally recommended antimalarial drugs. We present the results of studies on the efficacy of recommended antimalarials and molecular markers of artemisinin and partner resistance in Afghanistan, Pakistan, Somalia, Sudan and Yemen.

METHODS

Single-arm prospective studies were conducted to evaluate the efficacy of artesunate-sulfadoxine-pyrimethamine (ASSP) in Afghanistan and Pakistan, artemether-lumefantrine (AL) in all countries, or dihydroartemisinin-piperaquine (DP) in Sudan for the treatment of Plasmodium falciparum. The efficacy of chloroquine (CQ) and AL for the treatment of Plasmodium vivax was evaluated in Afghanistan and Somalia, respectively. Patients were treated and monitored for 28 (CQ, ASSP and AL) or 42 (DP) days. Polymerase chain reaction (PCR)-corrected cure rate and parasite positivity rate at Day 3 were estimated. Mutations in the P. falciparum kelch 13 (Pfk13) gene and amplifications of plasmepsin (Pfpm2) and multidrug resistance-1 (Pfmdr-1) genes were also studied.

RESULTS

A total of 1680 (249 for ASSP, 1079 for AL and 352 for DP) falciparum cases were successfully assessed. A PCR-adjusted ASSP cure rate of 100% was observed in Afghanistan and Pakistan. For AL, the cure rate was 100% in all but four sites in Sudan, where cure rates ranged from 92.1% to 98.8%. All but one patient were parasite-free at Day 3. For P. vivax, cure rates were 98.2% for CQ and 100% for AL. None of the samples from Afghanistan, Pakistan and Yemen had a Pfk13 mutation known to be associated with artemisinin resistance. In Sudan, the validated Pfk13 R622I mutation accounted for 53.8% (14/26) of the detected non-synonymous Pfk13 mutations, most of which were repeatedly detected in Gadaref. A prevalence of 2.7% and 9.3% of Pfmdr1 amplification was observed in Pakistan and Yemen, respectively.

CONCLUSION

High efficacy of ASSP, AL and DP in the treatment of uncomplicated falciparum infection and of CQ and AL in the treatment of P. vivax was observed in the respective countries. The repeated detection of a relatively high rate of Pfk13 R622I mutation in Sudan underscores the need for close monitoring of the efficacy of recommended ACTs, parasite clearance rates and Pfk13 mutations in Sudan and beyond. Registration numbers of the trials: ACTRN12622000944730 and ACTRN12622000873729 for Afghanistan, ACTRN12620000426987 and ACTRN12617001025325 for Pakistan, ACTRN12618001224213 for Somalia, ACTRN12617000276358, ACTRN12622000930785 and ACTRN12618001800213 for Sudan and ACTRN12617000283370 for Yemen.

Increasing Prevalence of Artemisinin-Resistant HRP2-Negative Malaria in Eritrea

BACKGROUND

Although the clinical efficacy of antimalarial artemisinin-based combination therapies in Africa remains high, the recent emergence of partial resistance to artemisinin in Plasmodium falciparum on the continent is troubling, given the lack of alternative treatments.

METHODS

In this study, we used data from drug-efficacy studies conducted between 2016 and 2019 that evaluated 3-day courses of artemisinin-based combination therapy (artesunate-amodiaquine or artemether-lumefantrine) for uncomplicated malaria in Eritrea to estimate the percentage of patients with day-3 positivity (i.e., persistent P. falciparum parasitemia 3 days after the initiation of therapy). We also assayed parasites for mutations in Pfkelch13 as predictive markers of partial resistance to artemisinin and screened for deletions in hrp2 and hrp3 that result in variable performance of histidine rich protein 2 (HRP2)-based rapid diagnostic tests for malaria.

RESULTS

We noted an increase in the percentage of patients with day-3 positivity from 0.4% (1 of 273) in 2016 to 1.9% (4 of 209) in 2017 and 4.2% (15 of 359) in 2019. An increase was also noted in the prevalence of the Pfkelch13 R622I mutation, which was detected in 109 of 818 isolates before treatment, from 8.6% (24 of 278) in 2016 to 21.0% (69 of 329) in 2019. The odds of day-3 positivity increased by a factor of 6.2 (95% confidence interval, 2.5 to 15.5) among the patients with Pfkelch13 622I variant parasites. Partial resistance to artemisinin, as defined by the World Health Organization, was observed in Eritrea. More than 5% of the patients younger than 15 years of age with day-3 positivity also had parasites that carried Pfkelch13 R622I. In vitro, the R622I mutation conferred a low level of resistance to artemisinin when edited into NF54 and Dd2 parasite lines. Deletions in both hrp2 and hrp3 were identified in 16.9% of the parasites that carried the Pfkelch13 R622I mutation, which made them potentially undetectable by HRP2-based rapid diagnostic tests.

CONCLUSIONS

The emergence and spread of P. falciparum lineages with both Pfkelch13-mediated partial resistance to artemisinin and deletions in hrp2 and hrp3 in Eritrea threaten to compromise regional malaria control and elimination campaigns. (Funded by the Bill and Melinda Gates Foundation and others; Australian New Zealand Clinical Trials Registry numbers, ACTRN12618001223224, ACTRN12618000353291, and ACTRN12619000859189.).

Prevalence of mutations in the cysteine desulfurase IscS (Pfnfs1) gene in recurrent Plasmodium falciparum infections following artemether-lumefantrine (AL) and dihydroartemisinin-piperaquine (DP) treatment in Matayos, Western Kenya

BACKGROUND

Malaria remains a public health concern globally. Resistance to anti-malarial drugs has consistently threatened the gains in controlling the malaria parasites. Currently, artemether-lumefantrine (AL) and dihydroartemisinin-piperaquine (DP) are the treatment regimens against Plasmodium falciparum infections in many African countries, including Kenya. Recurrent infections have been reported in patients treated with AL or DP, suggesting the possibility of reinfection or parasite recrudescence associated with the development of resistance against the two therapies. The Plasmodium falciparum cysteine desulfurase IscS (Pfnfs1) K65 selection marker has previously been associated with decreased lumefantrine susceptibility. This study evaluated the frequency of the Pfnfs1 K65 resistance marker and associated K65Q resistant allele in recurrent infections collected from P. falciparum-infected individuals living in Matayos, Busia County, in western Kenya.

METHODS

Archived dried blood spots (DBS) of patients with recurrent malaria infection on clinical follow-up days after treatment with either AL or DP were used in the study. After extraction of genomic DNA, PCR amplification and sequencing analysis were employed to determine the frequencies of the Pfnfs1 K65 resistance marker and K65Q mutant allele in the recurrent infections. Plasmodium falciparum msp1 and P. falciparum msp2 genetic markers were used to distinguish recrudescent infections from new infections.

RESULTS

The K65 wild-type allele was detected at a frequency of 41% while the K65Q mutant allele was detected at a frequency of 22% in the recurrent samples. 58% of the samples containing the K65 wild-type allele were AL treated samples and while 42% were DP treated samples. 79% of the samples with the K65Q mutation were AL treated samples and 21% were DP treated samples. The K65 wild-type allele was detected in three recrudescent infections (100%) identified from the AL treated samples. The K65 wild-type allele was detected in two recrudescent DP treated samples (67%) while the K65Q mutant allele was identified in one DP treated (33%) recrudescent sample.

CONCLUSIONS

The data demonstrate a higher frequency of the K65 resistance marker in patients with recurrent infection during the study period. The study underscores the need for consistent monitoring of molecular markers of resistance in regions of high malaria transmission.

Antiplasmodial activity of coumarins isolated from Polygala boliviensis: in vitro and in silico studies

Polygala boliviensis is found in the Brazilian semiarid region. This specie is little chemically and biologically studied. Polygala spp. have different metabolites, especially coumarins. Studies indicate that coumarins have antimalarial potential, denoting the importance of researching new active compounds from plants, since the resistance of Plasmodium strains to conventional therapy has increased. The present study aimed to evaluate the antiplasmodial activity of auraptene and poligalen against a chloroquine-resistant strain of Plasmodium falciparum. Coumarins were isolated from P. boliviensis by open column chromatography and identified by Nuclear Magnetic Resonance Spectroscopy. A cytotoxicity assay was carried out using MTT test, and the in vitro antiplasmodial activity was evaluated using the W2 strain. The antiplasmodial activity results found were IC50=0.171 ± 0.016 for auraptene and 0.164 ± 0.012 for poligalen; the selectivity indexes were 78.71 and 609.76, respectively. Inverse virtual screening in the BRAMMT database by OCTOPUS 1.2 was applied to coumarins to find potential P. falciparum targets and showed higher affinity energy of auraptene for purine nucleoside phosphorylase (PfPNP) and of poligalen for dihydroorotate dehydrogenase (PfDHODH). Molecular Dynamics studies (MD and MM-GBSA) approach were applied to calculate binding energies against selected P. falciparum targets and showed that all coumarins were stable at the binding site during simulations. Furthermore, energies were favorable for complexation. This is the first report of auraptene in P. boliviensis species and of in vitro antiplasmodial activity of auraptene and poligalen. In silico studies indicated that the mechanism of action of coumarins is the inhibition of PfPNP and PfDHODH.Communicated by Ramaswamy H. Sarma.

Safety and therapeutic efficacy of artemether-lumefantrine in the treatment of uncomplicated Plasmodium falciparum malaria at Shecha health centre, Arba Minch, Ethiopia

BACKGROUND

In 2004, Ethiopia adopted artemether-lumefantrine (AL, Coartem^®) as first-line treatment for the management of uncomplicated Plasmodium falciparum malaria. Continuous monitoring of AL therapeutic efficacy is crucial in Ethiopia, as per the World Health Organization (WHO) recommendation. This study aimed to assess the therapeutic efficacy of AL in the treatment of uncomplicated P. falciparum infection.

METHODS

A 28 day onearm, prospective evaluation of the clinical and parasitological response to AL was conducted at Shecha Health Centre, Arba Minch town, Southern Ethiopia. Patients were treated with six-dose regimen of AL over three days and monitored for 28 days with clinical and laboratory assessments. Participant recruitment and outcome classification was done in accordance with the 2009 WHO methods for surveillance of anti-malarial drug efficacy guidelines.

RESULTS

A total of 88 study participants were enrolled and 69 of them completed the study with adequate clinical and parasitological response. Two late parasitological failures were observed, of which one was classified as a recrudescence by polymerase chain reaction (PCR). The PCRcorrected cure rate was 98.6% (95% CI 92.3-100). AL demonstrated a rapid parasite and fever clearance with no parasitaemia on day 2 and febrile cases on day 3. Gametocyte clearance was complete by day three. No serious adverse events were reported during the 28 days follow-up.

CONCLUSION

The study demonstrated high therapeutic efficacy and good safety profile of AL. This suggests the continuation of AL as the first-line drug for the treatment of uncomplicated P. falciparum malaria in Ethiopia. Periodic therapeutic efficacy studies and monitoring of markers of resistance are recommended for early detection of resistant parasites.

Therapeutic efficacy of dihydroartemisinin-piperaquine combination for the treatment of uncomplicated malaria in Ghana

In 2020, Dihydroartemisinin-Piperaquine (DHAP) was adopted as a second-line antimalarial for treatment of uncomplicated malaria in Ghana following a review of the country's antimalarial medicines policy. Available data obtained in 2007 had shown PCR-uncorrected therapeutic efficacy of 93.3% using a 28-day follow-up schedule. In 2020, the standard 42-day follow-up schedule for DHAP was used to estimate efficacy levels among febrile children aged 6 months to 9 years in three malaria sentinel sites representing the three main ecological zones of the country- savannah, forest, and coastal. PCR genotyping distinguished between recrudescence and re-infection using merozoite surface protein 2 (MSP2)-specific primers for FC27 and 3D7 strains. Per protocol analyses showed day 28 efficacy of 100% in all three sentinel sites with day 42 PCR-corrected efficacy ranging between 90.3% (95% CI: 80.1 - 96.4%) in the savannah zone and 100% in the forest and coastal zones, yielding a national average of 97.0% (95% CI: 93.4 - 98.8). No day 3 parasitemia was observed in all three sites. Prevalence of measured fever (axillary temperature ≥ 37.5°C) declined from 50.0 - 98.8% on day 0 to 7.1-11.5% on day 1 whilst parasitemia declined from 100% on day 0 to 1.2 - 2.3% on day 1. Mean haemoglobin levels on days 28 and 42 were significantly higher than pre-treatment levels in all three sites. We conclude that DHAP is highly efficacious in the treatment of uncomplicated malaria in Ghana. This data will serve as baseline for subsequent DHAP efficacy studies in the country.

Therapeutic efficacies of artemether-lumefantrine and dihydroartemisinin-piperaquine for the treatment of uncomplicated Plasmodium falciparum and chloroquine and dihydroartemisinin-piperaquine for uncomplicated Plasmodium vivax infection in Ethiopia

BACKGROUND

Routine monitoring of anti-malarial drugs is recommended for early detection of drug resistance and to inform national malaria treatment guidelines. In Ethiopia, the national treatment guidelines employ a species-specific approach. Artemether-lumefantrine (AL) and chloroquine (CQ) are the first-line schizonticidal treatments for Plasmodium falciparum and Plasmodium vivax, respectively. The National Malaria Control and Elimination Programme in Ethiopia is considering dihydroartemisinin-piperaquine (DHA/PPQ) as an alternative regimen for P. falciparum and P. vivax.

METHODS

The study assessed the clinical and parasitological efficacy of AL, CQ, and DHA/PPQ in four arms. Patients over 6 months and less than 18 years of age with uncomplicated malaria mono-infection were recruited and allocated to AL against P. falciparum and CQ against P. vivax. Patients 18 years or older with uncomplicated malaria mono-infection were recruited and randomized to AL or dihydroartemisinin-piperaquine (DHA/PPQ) against P. falciparum and CQ or DHA/PPQ for P. vivax. Patients were followed up for 28 (for CQ and AL) or 42 days (for DHA/PPQ) according to the WHO recommendations. Polymerase chain reaction (PCR)-corrected and uncorrected estimates were analysed by Kaplan Meier survival analysis and per protocol methods.

RESULTS

A total of 379 patients were enroled in four arms (n = 106, AL-P. falciparum; n = 75, DHA/PPQ- P. falciparum; n = 142, CQ-P. vivax; n = 56, DHA/PPQ-P. vivax). High PCR-corrected adequate clinical and parasitological response (ACPR) rates were observed at the primary end points of 28 days for AL and CQ and 42 days for DHA/PPQ. ACPR rates were 100% in AL-Pf (95% CI: 96-100), 98% in CQ-P. vivax (95% CI: 95-100) at 28 days, and 100% in the DHA/PPQ arms for both P. falciparum and P. vivax at 42 days. For secondary endpoints, by day three 99% of AL-P. falciparum patients (n = 101) cleared parasites and 100% were afebrile. For all other arms, 100% of patients cleared parasites and were afebrile by day three. No serious adverse events were reported.

CONCLUSION

This study demonstrated high therapeutic efficacy for the anti-malarial drugs currently used by the malaria control programme in Ethiopia and provides information on the efficacy of DHA/PPQ for the treatment of P. falciparum and P. vivax as an alternative option.

Therapeutic efficacy of artemether-lumefantrine, artesunate-amodiaquine and dihydroartemisinin-piperaquine in the treatment of uncomplicated Plasmodium falciparum malaria in Sub-Saharan Africa: A systematic review and meta-analysis

Background

Sub-Saharan Africa has the highest burden of malaria in the world. Artemisinin-based combination therapies (ACTs) have been the cornerstone in the efforts to reduce the global burden of malaria. In the effort to facilitate early detection of resistance for artemisinin derivatives and partner drugs, WHO recommends monitoring of ACT’s efficacy in the malaria endemic countries. The present systematic meta-analysis study summarises the evidence of therapeutic efficacy of the commonly used artemisinin-based combinations for the treatment of uncomplicated P. falciparum malaria in Sub-Saharan Africa after more than a decade since the introduction of the drugs.

Methods

Fifty two studies carried out from 2010 to 2020 on the efficacy of artemether-lumefantrine or dihydro-artemisinin piperaquine or artesunate amodiaquine in patients with uncomplicated P. falciparum malaria in Sub-Saharan Africa were searched for using the Google Scholar, Cochrane Central Register of controlled trials (CENTRAL), PubMed, Medline, LILACS, and EMBASE online data bases. Data was extracted by two independent reviewers. Random analysis effect was performed in STATA 13. Heterogeneity was established using I² statistics.

Results

Based on per protocol analysis, unadjusted cure rates in malaria infected patients treated with artemether-lumefantrine (ALU), artesunate-amodiaquine (ASAQ) and dihydroartemisinin-piperaquine (DHP) were 89%, 94% and 91% respectively. However, the cure rates after PCR correction were 98% for ALU, 99% for ASAQ and 99% for DHP.

Conclusion

The present meta-analysis reports the overall high malaria treatment success for artemether-lumefantrine, artesunate-amodiaquine and dihydroartemisinin-piperaquine above the WHO threshold value in Sub-Saharan Africa.

Efficacy and safety of artemether-lumefantrine and dihydroartemisinin-piperaquine for the treatment of uncomplicated Plasmodium falciparum malaria and prevalence of molecular markers associated with artemisinin and partner drug resistance in Uganda

Background

In Uganda, artemether-lumefantrine (AL) is first-line therapy and dihydroartemisinin-piperaquine (DP) second-line therapy for the treatment of uncomplicated malaria. This study evaluated the efficacy and safety of AL and DP in the management of uncomplicated falciparum malaria and measured the prevalence of molecular markers of resistance in three sentinel sites in Uganda from 2018 to 2019.

Methods

This was a randomized, open-label, phase IV clinical trial. Children aged 6 months to 10 years with uncomplicated falciparum malaria were randomly assigned to treatment with AL or DP and followed for 28 and 42 days, respectively. Genotyping was used to distinguish recrudescence from new infection, and a Bayesian algorithm was used to assign each treatment failure a posterior probability of recrudescence. For monitoring resistance, Pfk13 and Pfmdr1 genes were Sanger sequenced and plasmepsin-2 copy number was assessed by qPCR.

Results

There were no early treatment failures. The uncorrected 28-day cumulative efficacy of AL ranged from 41.2 to 71.2% and the PCR-corrected cumulative 28-day efficacy of AL ranged from 87.2 to 94.4%. The uncorrected 28-day cumulative efficacy of DP ranged from 95.8 to 97.9% and the PCR-corrected cumulative 28-day efficacy of DP ranged from 98.9 to 100%. The uncorrected 42-day efficacy of DP ranged from 73.5 to 87.4% and the PCR-corrected 42-day efficacy of DP ranged from 92.1 to 97.5%. There were no reported serious adverse events associated with any of the regimens. No resistance-associated mutations in the Pfk13 gene were found in the successfully sequenced samples. In the AL arm, the NFD haplotype (N86Y, Y184F, D1246Y) was the predominant Pfmdr1 haplotype, present in 78 of 127 (61%) and 76 of 110 (69%) of the day 0 and day of failure samples, respectively. All the day 0 samples in the DP arm had one copy of the plasmepsin-2 gene.

Conclusions

DP remains highly effective and safe for the treatment of uncomplicated malaria in Uganda. Recurrent infections with AL were common. In Busia and Arua, the 95% confidence interval for PCR-corrected AL efficacy fell below 90%. Further efficacy monitoring for AL, including pharmacokinetic studies, is recommended.

Trial registration The trail was also registered with the ISRCTN registry with study Trial No. PACTR201811640750761

Supplementary Information

The online version contains supplementary material available at 10.1186/s12936-021-04021-5.

Comparative effect of dihydroartemisinin-piperaquine and artemether-lumefantrine on gametocyte clearance and haemoglobin recovery in children with uncomplicated Plasmodium falciparum malaria in Africa: a systematic review and meta-analysis of randomized control trials

BACKGROUND

Plasmodium falciparum gametocytaemia has been associated with anaemia. The aim of this review was to synthesize available evidence on the comparative effect of dihydroartemisinin-piperaquine (DHA-PQ) and artemether-lumefantrine (AL) on gametocyte clearance and haemoglobin recovery in children with uncomplicated P. falciparum malaria in Africa.

METHODS

A systematic literature search was undertaken to identify relevant articles from online databases. The search was performed from August 2020 to 30 April 2021. Extracted data from eligible studies were pooled as risk ratios with 95% confidence intervals (CI).

RESULTS

Gametocyte carriage was reduced in both treatment groups, with no significant difference found between the groups. However, on days 28 and 42, a significant increase in serum haemoglobin level from baseline was observed in the DHA-PQ group (standardized mean difference 0.15, 95% CI 0.05-0.26; participants=2715; studies=4; I²⁼32%, high quality of evidence) compared with the AL group (mean difference 0.35, 95% CI 0.12-0.59; participants=1434; studies=3; I²=35%, high quality of evidence).

CONCLUSION

DHA-PQ had a greater impact on haemoglobin recovery than AL on days 28 and 42; this difference was significant.

Efficacy of dihydroartemisinin-piperaquine versus artemether-lumefantrine for the treatment of uncomplicated Plasmodium falciparum malaria among children in Africa: a systematic review and meta-analysis of randomized control trials

BACKGROUND

Emergence of Plasmodium falciparum resistance to artemisinin and its derivatives poses a threat to the global effort to control malaria. The emergence of anti-malarial resistance has become a great public health challenge and continues to be a leading threat to ongoing malaria control efforts. The aim of this review was to synthesize available evidence on the efficacy of dihydroartemisinin-piperaquine (DHA-PQ) compared to artemether-lumefantrine (AL) for the treatment of uncomplicated falciparum malaria among children in Africa.

METHODS

A systematic literature search was done to identify relevant articles from online databases PubMed/ MEDLINE, Embase, and Cochrane Central Register of Controlled Trials' database (CENTRAL) for retrieving randomized control trials comparing efficacy of DHA-PQ and AL for treatment of uncomplicated falciparum malaria in African children. The search was performed from August 2020 to April 2021. Using Rev-Man software (V5.4.1), R-studio and Comprehensive Meta-analysis software version 3, the extracted data from eligible studies were pooled as risk ratio (RR) with 95% confidence interval (CI).

RESULTS

In this review, 25 studies which involved a total of 13,198 participants were included. PCR-unadjusted treatment failure in children aged between 6 months and 15 years was significantly lower in the DHA-PQ treatment arm on day 28 than that of AL (RR 0.14, 95% CI 0.08-0.26; participants = 1302; studies = 4; I² = 0%, high quality of evidence). Consistently, the PCR-adjusted treatment failure was significantly lower with DHA-PQ treatment group on day 28 (RR 0.45, 95% CI 0.29-0.68; participants = 8508; studies = 16; I² = 51%, high quality of evidence) and on day 42 (RR 0.60, 95% CI 0.47-0.78; participants = 5959; studies = 17; I² = 0%, high quality of evidence). However, the efficacy was ≥ 95% in both treatment groups on day 28.

CONCLUSION

From this review, it can be concluded that DHA-PQ reduces new infection and recrudescence on days 28 and 42 more than AL. This may trigger DHA-PQ to become a first-line treatment option.

Therapeutic efficacy of artesunate-amodiaquine and artemether-lumefantrine and polymorphism in Plasmodium falciparum kelch13-propeller gene in Equatorial Guinea

Background

Artesunate-amodiaquine (ASAQ) and artemether-lumefantrine (AL) are the currently recommended first- and second-line therapies for uncomplicated Plasmodium falciparum infections in Equatorial Guinea. This study was designed to evaluate the efficacy of these artemisinin-based combinations and detect mutations in P. falciparum kelch13-propeller domain gene (Pfkelch13).

Methods

A single-arm prospective study evaluating the efficacy of ASAQ and AL at three sites: Malabo, Bata and Ebebiyin was conducted between August 2017 and July 2018. Febrile children aged six months to 10 years with confirmed uncomplicated P. falciparum infection and other inclusion criteria were sequentially enrolled first in ASAQ and then in AL at each site, and followed up for 28 days. Clinical and parasitological parameters were assessed. The primary endpoint was PCR-adjusted adequate clinical and parasitological response (ACPR). Samples on day-0 were analysed for mutations in Pfkelch13 gene.

Results

A total 264 and 226 patients were enrolled in the ASAQ and AL treatment groups, respectively. Based on per-protocol analysis, PCR-adjusted cure rates of 98.6% to 100% and 92.4% to 100% were observed in patients treated with ASAQ and AL, respectively. All study children in both treatment groups were free of parasitaemia by day-3. Of the 476 samples with interpretable results, only three samples carried non-synonymous Pfkelch13 mutations (E433D and A578S), and none of them is the known markers associated with artemisinin resistance.

Conclusion

The study confirmed high efficacy of ASAQ and AL for the treatment of uncomplicated falciparum infections as well as the absence of delayed parasite clearance and Pfkelch13 mutations associated with artemisinin resistance. Continued monitoring of the efficacy of these artemisinin-based combinations, at least every two years, along with molecular markers associated with artemisinin and partner drug resistance is imperative to inform national malaria treatment policy and detect resistant parasites early.

Trial registration ACTRN12617000456358, Registered 28 March 2017; http://www.anzctr.org.au/trial/MyTrial.aspx

Efficacy and safety of dihydroartemisinin-piperaquine versus artemether-lumefantrine for treatment of uncomplicated Plasmodium falciparum malaria in Ugandan children: a systematic review and meta-analysis of randomized control trials

Background

The emergence of artemisinin resistance in Southeast Asia and Plasmodium falciparum kelch13 propeller gene mutations in sub-Saharan African pose the greatest threat to global efforts to control malaria. This is a critical concern in Uganda, where artemisinin-based combination therapy (ACT) is the first-line treatment for uncomplicated falciparum. The objective of this study was to compare the efficacy and safety of dihydroartemisinin–piperaquine (DHA–PQ) and artemether–lumefantrine (AL) for the treatment of uncomplicated falciparum malaria in Ugandan children.

Methods

A search of PubMed and the Cochrane Central Register of Controlled Trials for retrieving randomized controlled trials comparing the efficacy and safety of DHA–PQ and AL for treatment of uncomplicated falciparum malaria in Ugandan children was done. The search was performed up to 31 August 2020. The data extracted from eligible studies and pooled as risk ratio (RR) with a 95% confidence interval (CI), using Rev Man Software (5.4). The protocol was registered in PROSPERO, ID: CRD42020182354.

Results

Eleven trials were included in this review and two of them only included under safety outcome. Total 3798 participants were enrolled. The PCR unadjusted treatment failure was significantly lower with DHA–PQ at day 28 (RR 0.30, 95% CI 0.19–0.49; participants = 7863; studies = 5; I² = 93%, low quality evidence) and at day 42 (RR 0.53, 95% CI 0.38–0.76; participants = 1618; studies = 4; I² = 79%, moderate quality of evidence). The PCR adjusted treatment failure at day 42 was significantly lower with DHA–PQ treatment group (RR 0.45, 95% CI 0.28 to 0.72; participants = 1370; studies = 5, high quality of evidence), and it was below 5% in both arms at day 28 (moderate quality of evidence). AL showed a longer prophylactic effect on new infections which may last for up to 63 days (PCR-adjusted treatment failure: RR 2.04, 95% CI 1.13–3.70; participants = 1311; studies = 2, moderate quality of evidence). Compared to AL, DHA–PQ was associated with a slightly higher frequency of cough (RR 1.07, 95% CI 1.01 to 1.13; 2575 participants; six studies; high quality of evidence). In both treatment groups, the risk of recurrent parasitaemia due to possible recrudescence was less than 5% at day 28. The appearance of gametocyte between 29 and 42 days was also significantly lower in DHA–PQ than AL (RR 0.26, 95% CI 0.12 to 0.56; participants = 623; studies = 2; I² = 0%).

Conclusion

Compared to AL, DHA–PQ appeared to reduce treatment failure and gametocyte carriage in Ugandan children. This may trigger DHA–PQ to become the first-line treatment option. Both treatments were safe and well-tolerated.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12936-021-03711-4.

An insight into the recent development of the clinical candidates for the treatment of malaria and their target proteins

Malaria is an endemic disease, prevalent in tropical and subtropical regions which cost half of million deaths annually. The eradication of malaria is one of the global health priority nevertheless, current therapeutic efforts seem to be insufficient due to the emergence of drug resistance towards most of the available drugs, even first-line treatment ACT, unavailability of the vaccine, and lack of drugs with a new mechanism of action. Intensification of antimalarial research in recent years has resulted into the development of single dose multistage therapeutic agents which has advantage of overcoming the antimalarial drug resistance. The present review explored the current progress in the development of new promising antimalarials against prominent target proteins that have the potential to be a clinical candidate. Here, we also reviewed different aspects of drug resistance and highlighted new drug candidates that are currently in a clinical trial or clinical development, along with a few other molecules with excellent antimalarial activity overs ACTs. The summarized scientific value of previous approaches and structural features of antimalarials related to the activity are highlighted that will be helpful for the development of next-generation antimalarials.

'Artemisinin Resistance': Something New or Old? Something of a Misnomer?

Artemisinin and its derivatives (ART) are crucial first-line antimalarial drugs that rapidly clear parasitemia, but recrudescences of the infection frequently follow ART monotherapy. For this reason, ART must be used in combination with one or more partner drugs that ensure complete cure. The ability of malaria parasites to survive ART monotherapy may relate to an innate growth bistability phenomenon whereby a fraction of the drug-exposed population enters into metabolic quiescence (dormancy) as persister forms. Characterization of the events that underlie entry and waking from persistence may lead to lasting breakthroughs in malaria chemotherapy that can prevent recrudescences and protect the future of ART-based combination therapies.

Efficacy and safety of artemisinin-based combination therapy and the implications of Pfkelch13 and Pfcoronin molecular markers in treatment failure in Senegal

In 2006, Senegal adopted artemisinin-based combination therapy (ACT) as first-line treatment in the management of uncomplicated malaria. This study aimed to update the status of antimalarial efficacy more than ten years after their first introduction. This was a randomized, three-arm, open-label study to evaluate the efficacy and safety of artemether-lumefantrine (AL), artesunate-amodiaquine (ASAQ) and dihydroartemisinin-piperaquine (DP) in Senegal. Malaria suspected patients were screened, enrolled, treated, and followed for 28 days for AL and ASAQ arms or 42 days for DP arm. Clinical and parasitological responses were assessed following antimalarial treatment. Genotyping (msp1, msp2 and 24 SNP-based barcode) were done to differentiate recrudescence from re-infection; in case of PCR-confirmed treatment failure, Pfk13 propeller and Pfcoronin genes were sequenced. Data was entered and analyzed using the WHO Excel-based application. A total of 496 patients were enrolled. In Diourbel, PCR non-corrected/corrected adequate clinical and parasitological responses (ACPR) was 100.0% in both the AL and ASAQ arms. In Kedougou, PCR corrected ACPR values were 98.8%, 100% and 97.6% in AL, ASAQ and DP arms respectively. No Pfk13 or Pfcoronin mutations associated with artemisinin resistance were found. This study showed that AL, ASAQ and DP remain efficacious and well-tolerated in the treatment of uncomplicated P. falciparum malaria in Senegal.

The gender-related variability in the pharmacokinetics and antiplasmodial activity of naphthoquine in rodents

BACKGROUND

Naphthoquine (NQ) is a suitable partner anti-malarial for the artemisinin-based combination therapy (ACT), which is recommended to be taken orally as a single-dose regimen. The metabolism of NQ was mainly mediated by CYP2D6, which is well-known to show gender-specific differences in its expression. In spite of its clinical use, there is limited information on the pharmacokinetics of NQ, and no data are available for females. In this study, the effect of gender on the pharmacokinetics and antiplasmodial efficacy of NQ in rodents was evaluated. The underlying factors leading to the potential gender difference, i.e., plasma protein binding and metabolic clearance, were also evaluated.

METHODS

The pharmacokinetic profiles of NQ were investigated in healthy male or female rats after a single oral administration of NQ. The antiplasmodial efficacy of NQ was studied in male or female mice infected with Plasmodium yoelii. The recrudescence and survival time of infected mice were also recorded after drug treatment. Plasma protein binding of NQ was determined in pooled plasma collected from male or female mice, rat or human. In vitro metabolism experiments were performed in the liver microsomes of male or female mice, rat or human.

RESULTS

The results showed that the gender of rats did not affect NQ exposure (AUC_0-t and C_max) significantly (P > 0.05). However, a significant (P < 0.05) longer t_1/2 was found for NQ in male rats (192.1 ± 47.7), compared with female rats (143.9 ± 27.1). Slightly higher but not significant (P > 0.05) antiplasmodial activity was found for NQ in male mice (ED₉₀, 1.10 mg/kg) infected with P. yoelii, compared with female mice (ED₉₀, 1.67 mg/kg). The binding rates of NQ to plasma protein were similar in males and females. There was no metabolic difference for NQ in male and female mice, rat or human liver microsomes.

CONCLUSIONS

These results indicated that the pharmacokinetic profiles of NQ were similar between male and female rats, except for a longer t_1/2 in male rats. The difference was not associated with plasma protein binding or hepatic metabolic clearance. Equivalent antiplasmodial activity was found for NQ in male and female mice infected with P. yoelii. This study will be helpful for the rational design of clinical trials for NQ.