Antimalarial Regimens Research Articles

Adapting malaria indicator surveys to investigate treatment adherence: a pilot study on Bioko Island, Equatorial Guinea

BackgroundAdherence to anti-malarial treatment regimens is an important aspect of understanding and improving the impact of malaria case management. However, both adherence to artemisinin-based combination therapy (ACT) and the factors driving it vary widely. While many other evaluation activities have been conducted on Bioko Island, until now adherence to anti-malarial treatments, and in particular ACT has not been evaluated.MethodsThe implementation of a malaria indicator survey (MIS) conducted on Bioko in 2023 was leveraged to evaluate adherence to ACT provided to individuals testing positive following the survey. A follow-up team visited the targeted households, physically observed treatment blisters where possible, and provided messaging to household members on the importance of adhering to the treatment guidelines to household members. The team used survey data from the targeted households to make messaging as relevant to the household’s particular context as possible.ResultsOverall ACT adherence on Bioko Island was low, around 50%, and this varied demographically and geographically. Some of the highest transmission areas had exceptionally low adherence, but no systematic relationship between proper adherence and Plasmodium falciparum prevalence was detected. Estimates of adherence from follow-up visits were much lower than survey-based estimates in the same households (52.5% versus 87.1%), suggesting that lack of proper adherence may be a much larger issue on Bioko Island than previously thought.ConclusionRepresentative surveys can be easily adapted to provide empirical estimates of adherence to anti-malarial treatments, complementary to survey-based and health facility-based estimates. The large discrepancy between adherence as measured in this study and survey-based estimates on Bioko Island suggests a health facility-based study to quantify adherence among the population receiving treatment for symptomatic malaria may be necessary.

Characterising the blood-stage antimalarial activity of pyronaridine in healthy volunteers experimentally infected with Plasmodium falciparum

With the spread of artemisinin resistance throughout Southeast Asia and now in Africa, the antimalarial drug pyronaridine is likely to become an increasingly important component of new antimalarial drug regimens. However, the antimalarial activity of pyronaridine in humans has not been completely characterised. This volunteer infection study aimed to determine the pharmacokinetic/pharmacodynamic (PK/PD) relationship of pyronaridine in malaria naïve adults. Volunteers were inoculated with Plasmodium falciparum-infected erythrocytes on day 0 and administered different single oral doses of pyronaridine on day 8. Parasitaemia and concentrations of pyronaridine were measured and standard safety assessments performed. Curative artemether-lumefantrine therapy was administered if parasite regrowth occurred, or on day 47 ± 2. Outcomes were parasite clearance kinetics, PK and PK/PD parameters from modelling. Ten participants were inoculated and administered 360 mg (n = 4), 540 mg (n = 4) or 720 mg (n = 1) pyronaridine. One participant was withdrawn without receiving pyronaridine. The time to maximum pyronaridine concentration was 1–2 h, the elimination half-life was 8–9 d, and the parasite clearance half-life was approximately 5 h. Parasite regrowth occurred with 360 mg (4/4 participants) and 540 mg (2/4 participants). Key efficacy parameters including the minimum inhibitory concentration (5.5 ng/mL) and minimum parasiticidal concentration leading to 90% of maximum effect (MPC90: 8 ng/mL) were derived from the PK/PD model. Adverse events considered related to pyronaridine were predominantly mild to moderate gastrointestinal symptoms. There were no serious adverse events. Data obtained in this study will support the use of pyronaridine in new antimalarial combination therapies by informing partner drug selection and dosing considerations.

Superior protection in a relapsing Plasmodium cynomolgi rhesus macaque model by a chemoprophylaxis with sporozoite immunization regimen with atovaquone-proguanil followed by primaquine

BackgroundTo gain a deeper understanding of protective immunity against relapsing malaria, this study examined sporozoite-specific T cell responses induced by a chemoprophylaxis with sporozoite (CPS) immunization in a relapsing Plasmodium cynomolgi rhesus macaque model.MethodsThe animals received three CPS immunizations with P. cynomolgi sporozoites, administered by mosquito bite, while under two anti-malarial drug regimens. Group 1 (n = 6) received artesunate/chloroquine (AS/CQ) followed by a radical cure with CQ plus primaquine (PQ). Group 2 (n = 6) received atovaquone-proguanil (AP) followed by PQ. After the final immunization, the animals were challenged with intravenous injection of 104P. cynomolgi sporozoites, the dose that induced reliable infection and relapse rate. These animals, along with control animals (n = 6), were monitored for primary infection and subsequent relapses. Immunogenicity blood draws were done after each of the three CPS session, before and after the challenge, with liver, spleen and bone marrow sampling and analysis done after the challenge.ResultsGroup 2 animals demonstrated superior protection, with two achieving protection and two experiencing partial protection, while only one animal in group 1 had partial protection. These animals displayed high sporozoite-specific IFN-γ T cell responses in the liver, spleen, and bone marrow after the challenge with one protected animal having the highest frequency of IFN-γ+ CD8+, IFN-γ+ CD4+, and IFN-γ+ γδ T cells in the liver. Partially protected animals also demonstrated a relatively high frequency of IFN-γ+ CD8+, IFN-γ+ CD4+, and IFN-γ+ γδ T cells in the liver. It is important to highlight that the second animal in group 2, which experienced protection, exhibited deficient sporozoite-specific T cell responses in the liver while displaying average to high T cell responses in the spleen and bone marrow.ConclusionsThis research supports the notion that local liver T cell immunity plays a crucial role in defending against liver-stage infection. Nevertheless, there is an instance where protection occurs independently of T cell responses in the liver, suggesting the involvement of the liver's innate immunity. The relapsing P. cynomolgi rhesus macaque model holds promise for informing the development of vaccines against relapsing P. vivax.

Prophylactic effects of probiotic bacterium Latilactobacillus sakei on haematological parameters and cytokine profile of mice infected with Plasmodium berghei ANKA during early malaria infection

Malaria is a deadly parasitic disease caused a by protozoan parasite of the genus plasmodium. The challenges facing by chemotherapy and vector control couple with the lack of vaccine against malaria necessitate an urgent need for the development of alternative treatment regimens to combat this disease. One possible antimalarial treatment regimen is the use of probiotic bacteria as dietary supplements. Traditionally fermented milk is a rich source of probiotic bacteria that up to date, very few studies have been carried out on their immunoprotective effects against early malaria infection in mice. This study sought to assess the prophylactic activities of a probiotic bacterium Latilactobacillus sakei on malaria and inflammation in Plasmodium berghei infected mice. The probiotic bacterium was isolated from the Fulani's traditionally fermented milk and identified using the sequencing of the 16S r RNA gene. The repository activity of L. sakei on malaria was assessed using the method described by Peters with slight modification. Eighty-four BALB/c mice were randomly divided into two sets of seven groups of six mice each. One set received orally different doses of L. sakei Chloroquine and Sulfadoxine/Pyrimethamine for seven days before infection while the other set received for fourteen days before infection with 0.1 mL of 107Plasmodium berghei. Parasitaemia density, haematological parameters and inflammatory cytokines profile were evaluated. Data were presented as Mean ± SEM and analysed using SPSS version 20.0. The results of this study revealed that L. sakei significantly (p < 0.05) reduced in dose dependent manner parasite load, body weight loss and reduction of body temperature in all the treated mice when compare to untreated mice. Leukocytopenia, thrombocytosis and inflammation were also found to be significantly (p < 0.05) prevented in treated mice as compared to untreated mice.This study suggested that L sakei possesses immunomodulation and protective effects on early malaria infection in Plasmodium berghei mice.

Drug Use Practices and Self-Treatment for Suspected Malaria in Ibadan, Nigeria.

Antimalarial drug failures have been reported anecdotally in Nigeria, and malarial self-treatment practices could be a contributing factor. This study was designed to assess the pattern of drug use practices and self-treatment options among caregivers in Ibadan, Nigeria. We carried out a descriptive cross-sectional study among 283 study participant pairs (children under 5 years of age with suspected malaria and their caregivers). Structured questionnaires were used as research instruments. The results indicated that most caregivers were mothers (88.8%), 69% of caregivers self-prescribed and self-managed malaria for children under 5 years old without immediate hospital visits, and 76.4% of the caregivers believed most recommended and available antimalarial drugs were ineffective. Generally, 44.2% of respondents preferred and used antibiotics as a treatment strategy for malaria, 13.2% used agbo (a locally made liquid extract of plants and roots), 12.5% used prayers, and 19.6% used antimalarial drugs. Overall, only 57.1% of respondents stated that they always complete the standard antimalarial dosage regimen. The choice of malaria self-treatment options was significantly linked to the level of education. The findings identified antibiotics, agbo, and prayers as the immediate choices for self-treating malaria disease in Ibadan. Furthermore, incomplete adherence to antimalarial drugs is a general practice in Ibadan. Malaria self-treatment policy and continuous education on antimalarial drug use tailored to the different literacy and education levels of the general public is hereby recommended to reduce the risk of development of parasite resistance to effective anti-malarial drugs.

Abstract 5055: Targeting BRAFV600E/NRASQ61K-melanoma brain metastases by pharmacological intervention modulating ER/redox stress and EMT

Abstract Intracranial melanoma metastases originating from peripheral malignancy remain a frequent clinical condition with unsatisfactory pharmacological options. After screening a focused library of clinical artemisinin-combination therapeutic (ACT) antimalarials with established brain availability, we report here that an oral antimalarial regimen {(R,S)/(S,R)-[2,8-bis(trifluoromethyl)quinolin-4-yl]-piperidin-2-ylmethanol; BQPM} blocks (i) melanoma cell invasiveness and EMT-related gene expression and (ii) tumor growth in a bioluminescent murine model of BRAFi-resistant intracranial melanoma. First, we examined apoptotic elimination of cultured malignant melanoma cell lines, also examining feasibility of overcoming BRAFi-resistance comparing isogenic melanoma cells that differ only by NRAS mutational status (BRAFi-sensitive A375-BRAFV600E/NRASQ61 versus BRAFi-resistant A375-BRAFV600E/NRASQ61K). Among ACT antimalarials tested, BQPM was the only apoptogenic agent causing melanoma cell death at low micromolar concentrations. Comparative gene expression-array analysis (A375-BRAFV600E/NRASQ61 versus A375-BRAFV600E/NRASQ61K) revealed that BQPM is a dual inducer of endoplasmic reticulum (ER) and redox stress responses that precede BQPM-induced loss of viability. Moreover, we observed that BQPM treatment blocked EMT-related gene expression and phenotypic invasiveness in both BRAFi-sensitive and -resistant human cell lines, observable also in murine CNS-tropic Ret-melanoma cells. These data (combined with clinical evidence that documents brain availability of BQPM) suggest that blockade of brain metastasis and inhibition of intracranial tumor growth, even if BRAFi-resistant, can be achieved using BQPM as a repurposed ACT-antimalarial. Citation Format: Jana Jandova, Sophia L. Park, Jeremy A. Snell, Georg T. Wondrak. Targeting BRAFV600E/NRASQ61K-melanoma brain metastases by pharmacological intervention modulating ER/redox stress and EMT. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5055.

Application of Minimal Physiologically-Based Pharmacokinetic Model to Simulate Lung and Trachea Exposure of Pyronaridine and Artesunate in Hamsters.

A fixed-dose combination of pyronaridine and artesunate, one of the artemisinin-based combination therapies, has been used as a potent antimalarial treatment regimen. Recently, several studies have reported the antiviral effects of both drugs against severe acute respiratory syndrome coronavirus two (SARS-CoV-2). However, there are limited data on the pharmacokinetics (PKs), lung, and trachea exposures that could be correlated with the antiviral effects of pyronaridine and artesunate. The purpose of this study was to evaluate the pharmacokinetics, lung, and trachea distribution of pyronaridine, artesunate, and dihydroartemisinin (an active metabolite of artesunate) using a minimal physiologically-based pharmacokinetic (PBPK) model. The major target tissues for evaluating dose metrics are blood, lung, and trachea, and the nontarget tissues were lumped together into the rest of the body. The predictive performance of the minimal PBPK model was evaluated using visual inspection between observations and model predictions, (average) fold error, and sensitivity analysis. The developed PBPK models were applied for the multiple-dosing simulation of daily oral pyronaridine and artesunate. A steady state was reached about three to four days after the first dosing of pyronaridine and an accumulation ratio was calculated to be 1.8. However, the accumulation ratio of artesunate and dihydroartemisinin could not be calculated since the steady state of both compounds was not achieved by daily multiple dosing. The elimination half-life of pyronaridine and artesunate was estimated to be 19.8 and 0.4 h, respectively. Pyronaridine was extensively distributed to the lung and trachea with the lung-to-blood and trachea-to-blood concentration ratios (=Cavg,tissue/Cavg,blood) of 25.83 and 12.41 at the steady state, respectively. Also, the lung-to-blood and trachea-to-blood AUC ratios for artesunate (dihydroartemisinin) were calculated to be 3.34 (1.51) and 0.34 (0.15). The results of this study could provide a scientific basis for interpreting the dose-exposure-response relationship of pyronaridine and artesunate for COVID-19 drug repurposing.

How does pyronaridine plus artesunate compare with alternative antimalarial regimens for people with uncomplicated Plasmodium falciparum malaria?

How does pyronaridine plus artesunate compare with alternative antimalarial regimens for people with uncomplicated Plasmodium falciparum malaria?

Questionnaire-Based Analysis of Adverse Events and Compliance with Malaria Chemoprophylaxis in Taiwan

Malaria was eradicated in Taiwan in 1952; however, imported malaria cases are reported every year. The subtropical climate in Taiwan permits mosquito propagation and possible outbreaks of mosquito-borne diseases. The aim of this study was to investigate travelers' compliance and side effects of malaria prophylaxis to prevent a malaria outbreak in Taiwan. In this prospective study, we enrolled travelers who visited our travel clinic before going to malarious areas. A total of 161 questionnaires were collected and analyzed. Associations between the occurrence of side effects and compliance with antimalarial drugs were analyzed. Adjusted odds ratios were calculated after adjusting for potential risk factors in multiple logistic regression analysis. Of the 161 enrolled travelers, 58 (36.0%) reported side effects. Insomnia, somnolence, irritability, nausea, and anorexia were associated with poor compliance. Mefloquine was not associated with more neuropsychological side effects than doxycycline. Multiple logistic regression analysis showed that chemoprophylaxis compliance was affected by a younger age, visiting friends and relatives, visiting the travel clinic more than 1 week before the trip, and preferring to use the same antimalarial regimen on the next trip. Our findings could provide information to travelers besides labeled side effects to improve compliance with malaria prophylaxis and consequently help to prevent malaria outbreaks in Taiwan.

Abstract 13815: SARS-CoV-2 and Plasmodium Falciparum Co-Infection A Lethal Combination to the Heart

Introduction: COVID-19 pandemic has had an unprecedented impact worldwide, co-infections with neglected tropical diseases like Malaria can occur and affect the heart. Objective: Describe a unique case of Malaria and SARS CoV2 infection occurring concurrently with cardiac complications. Clinical Case: A 69-year-old male, retired canoeing athlete, with well-controlled arterial hypertension, presented odynophagia, cough, and dyspnea on slight exertion for 2 days. On examination, O2 saturation was 91%, blood pressure 100/60 mmHg, regular heart rate of 110 bpm, positive PCR for SARS-CoV-2, elevated D-Dimer, and chest X-ray with evidence of viral pneumonia. He received supplemental oxygen, steroids, and paracetamol. Two days later, he presented with choluria, afternoon episodes of high fever preceded by chills and myalgia, and a thick blood smear showed Plasmodium falciparum (PF) trophozoites. Antimalarial treatment was started with primaquine 15mg, 20 mg of artemether, and 120 mg of Lumefantrine daily with the disappearance of fever until day 14 of onset of symptoms when he presented with acute heart failure (AHF) with a reduced ejection fraction of 45%. NYHA Class IV, arterial hypotension, sudden onset palpitations, and afternoon febrile episode. The electrocardiogram showed atrial fibrillation (AF) with a rapid irregular ventricular response of 120 bpm; The echocardiogram revealed a 7mm circumferential pericardial effusion, right ventricular dysfunction. Treatment with colchicine, enoxaparin, spironolactone, and bisoprolol was started. A new thick smear demonstrated the persistence of PF. A new antimalarial regimen was restarted, with the disappearance of the fever 48 hours after its onset, with the reversion of AF to sinus rhythm. Discussion: A unique case of concurrent COVID-19 and Malaria, which cause challenges to the heart and lead to cardiovascular complications. Conclusion: An exceptional case is presented, the coexistence of SARS-CoV-2 and PF infection-associated complications of myocarditis, pericarditis, new-onset AF, and AHF. This interaction should not go unnoticed, physicians’ awareness is key, and early diagnosis and treatment can be lifesaving, mitigate and offer the best chance of cure.

Impact of prophylactic antimalarials in pregnant women living with Human Immunodeficiency Viruson birth outcomes in Botswana.

Until late 2015, Botswana recommended preventive treatment for pregnant women in malarial regions with chloroquine and proguanil (CP). The guideline change provided an opportunity to evaluate CP and adverse birth outcomes. The Tsepamo Study performed birth outcomes surveillance at large delivery centres throughout Botswana. We evaluated adverse birth outcomes from 2015 to 2017 at three hospitals where 93% of CP use was recorded. Outcomes included neonatal death (NND), small for gestational age (SGA), very SGA, stillbirth (SB), preterm delivery (PTD) and very PTD. Logistic regression analysis (unadjusted and adjusted) was conducted for each adverse birth outcome. During the study period, 5883 (26%) of 23,033 deliveries were exposed to CP, with the majority (65%) in the most malaria-endemic region. At this site, there was a trend or an association between CP use and reduction of three adverse birth outcomes: PTD (aOR 0.85, 95% CI 0.76-0.96), vPTD (aOR 0.83, 95% CI 0.68-1.01) and NND (aOR 0.65, 95% CI 0.42-1.00). However, at the least malaria-endemic site, the association was in the opposite direction for SB (aOR 1.54, 95% CI 1.08-2.22), SGA (aOR 1.24, 95% CI 1.06-1.44) and vSGA (aOR 1.42, 95% CI 1.14-1.77). The association between CP and reduced PTD was present among women without HIV (aOR 0.77, 95% CI 0.67-0.89) but not among women with HIV (aOR 1.09, 95% CI 0.78-1.35). Antimalarial prophylaxis was associated with improved birth outcomes in the most malaria-endemic region of Botswana, but not elsewhere. This finding supports current WHO guidance to use prophylaxis strategies among pregnant women in highly malaria-endemic regions. Further studies of the risks and benefits of specific antimalarial regimens in pregnancy are warranted, particularly in areas with lower incidence of malaria.

Molecular Profiles of Multiple Antimalarial Drug Resistance Markers in Plasmodium falciparum and Plasmodium vivax in the Mandalay Region, Myanmar.

Emergence and spreading of antimalarial drug resistant malaria parasites are great hurdles to combating malaria. Although approaches to investigate antimalarial drug resistance status in Myanmar malaria parasites have been made, more expanded studies are necessary to understand the nationwide aspect of antimalarial drug resistance. In the present study, molecular epidemiological analysis for antimalarial drug resistance genes in Plasmodium falciparum and P. vivax from the Mandalay region of Myanmar was performed. Blood samples were collected from patients infected with P. falciparum and P. vivax in four townships around the Mandalay region, Myanmar in 2015. Partial regions flanking major mutations in 11 antimalarial drug resistance genes, including seven genes (pfdhfr, pfdhps, pfmdr-1, pfcrt, pfk13, pfubp-1, and pfcytb) of P. falciparum and four genes (pvdhfr, pvdhps, pvmdr-1, and pvk12) of P. vivax were amplified, sequenced, and overall mutation patterns in these genes were analyzed. Substantial levels of mutations conferring antimalarial drug resistance were detected in both P. falciparum and P. vivax isolated in Mandalay region of Myanmar. Mutations associated with sulfadoxine-pyrimethamine resistance were found in pfdhfr, pfdhps, pvdhfr, and pvdhps of Myanmar P. falciparum and P. vivax with very high frequencies up to 90%. High or moderate levels of mutations were detected in genes such as pfmdr-1, pfcrt, and pvmdr-1 associated with chloroquine resistance. Meanwhile, low frequency mutations or none were found in pfk13, pfubp-1, pfcytb, and pvk12 of the parasites. Overall molecular profiles for antimalarial drug resistance genes in malaria parasites in the Mandalay region suggest that parasite populations in the region have substantial levels of mutations conferring antimalarial drug resistance. Continuous monitoring of mutations linked with antimalarial drug resistance is necessary to provide useful information for policymakers to plan for proper antimalarial drug regimens to control and eliminate malaria in the country.

Efficacy of three anti-malarial regimens for uncomplicated Plasmodium falciparum malaria in Cambodia, 2009–2011: a randomized controlled trial and brief review

BackgroundAnti-malarial resistance remains an important public health challenge in Cambodia. The effectiveness of three therapies for uncomplicated falciparum malaria was evaluated in Oddar Meanchey province in Northern Cambodia from 2009 to 2011.MethodsIn this randomized, open-label, parallel group-controlled trial, 211 subjects at least 5 years old with uncomplicated falciparum malaria were treated with 3 days of directly observed therapy: 63 received artesunate–mefloquine (AS/MQ), 77 received dihydroartemisinin–piperaquine (DHA/PPQ), and 71 received atovaquone–proguanil (ATQ/PG). The subjects were followed for 42 days or until recurrent parasitaemia. Genotyping of msp1, msp2, and glurp among individual parasite isolates distinguished recrudescence from reinfection. Pfmdr1 copy number was measured by real-time PCR and half-maximal parasite inhibitory concentrations (IC50) were measured in vitro by 48-h isotopic hypoxanthine incorporation assay.ResultsThe per-protocol PCR-adjusted efficacy (95% confidence interval) at 42 days was 80.6% (70.8–90.5%) for AS/MQ, 97.2% (93.3–100%) for DHA/PPQ, and 92.9% (86.1–99.6%) for ATQ/PG. On day 3, 57.9% remained parasitaemic in the AS/MQ and DHA/PPQ arms. At baseline, 46.9% had microscopic Plasmodium falciparum gametocytaemia. Both recurrences in the DHA/PPQ arm lost Pfmdr1 copy number amplification at recrudescence. All four recurrences in the ATQ/PG arm were wild-type for cytochrome bc1. One subject withdrew from the ATQ/PG arm due to drug allergy.ConclusionsThis study was conducted at the epicentre of substantial multi-drug resistance that emerged soon thereafter. Occurring early in the national transition from AS/MQ to DHA/PPQ, both DHA/PPQ and ATQ/PG had acceptable efficacy against uncomplicated falciparum malaria. However, efficacy of AS/MQ was only 80% with apparent mefloquine resistance based on elevated Pfmdr1 copy number and IC50. By 2009, there was already significant evidence of artemisinin resistance not previously reported at the Northern Cambodia–Thai border. This study suggests the basis for early development of significant DHA/PPQ failures within 3 years of introduction. Artemisinin resistance likely occurred on the Northern border concurrently with that reported along the Western border in Pailin.Trial registration This legacy trial was conducted prior to International Committee of Medical Journal Editors’ requirements for preregistration on ClinicalTrials.gov. The full protocol has been provided.

Spatiotemporal spread of Plasmodium falciparum mutations for resistance to sulfadoxine-pyrimethamine across Africa, 1990-2020.

BackgroundSulfadoxine-pyrimethamine (SP) is recommended in Africa in several antimalarial preventive regimens including Intermittent Preventive Treatment in pregnant women (IPTp), Intermittent Preventive Treatment in infants (IPTi) and Seasonal Malaria Chemoprevention (SMC). The effectiveness of SP-based preventive treatments are threatened in areas where Plasmodium falciparum resistance to SP is high. The prevalence of mutations in the dihydropteroate synthase gene (pfdhps) can be used to monitor SP effectiveness. IPTi-SP is recommended only in areas where the prevalence of the pfdhps540E mutation is below 50%. It has also been suggested that IPTp-SP does not have a protective effect in areas where the pfdhps581G mutation, exceeds 10%. However, pfdhps mutation prevalence data in Africa are extremely heterogenous and scattered, with data completely missing from many areas.Methods and findingsThe WWARN SP Molecular Surveyor database was designed to summarize dihydrofolate reductase (pfdhfr) and pfdhps gene mutation prevalence data. In this paper, pfdhps mutation prevalence data was used to generate continuous spatiotemporal surface maps of the estimated prevalence of the SP resistance markers pfdhps437G, pfdhps540E, and pfdhps581G in Africa from 1990 to 2020 using a geostatistical model, with a Bayesian inference framework to estimate uncertainty. The maps of estimated prevalence show an expansion of the pfdhps437G mutations across the entire continent over the last three decades. The pfdhps540E mutation emerged from limited foci in East Africa to currently exceeding 50% estimated prevalence in most of East and South East Africa. pfdhps540E distribution is expanding at low or moderate prevalence in central Africa and a predicted focus in West Africa. Although the pfdhps581G mutation spread from one focus in East Africa in 2000, to exceeding 10% estimated prevalence in several foci in 2010, the predicted distribution of the marker did not expand in 2020, however our analysis indicated high uncertainty in areas where pfdhps581G is present. Uncertainty was higher in spatial regions where the prevalence of a marker is intermediate or where prevalence is changing over time.ConclusionsThe WWARN SP Molecular Surveyor database and a set of continuous spatiotemporal surface maps were built to provide users with standardized, current information on resistance marker distribution and prevalence estimates. According to the maps, the high prevalence of pfdhps540E mutation was to date restricted to East and South East Africa, which is reassuring for continued use of IPTi and SMC in West Africa, but continuous monitoring is needed as the pfdhps540E distribution is expanding. Several foci where pfdhps581G prevalence exceeded 10% were identified. More data on the pfdhps581G distribution in these areas needs to be collected to guide IPTp-SP recommendations. Prevalence and uncertainty maps can be utilized together to strategically identify sites where increased surveillance can be most informative. This study combines a molecular marker database and predictive modelling to highlight areas of concern, which can be used to support decisions in public health, highlight knowledge gaps in certain regions, and guide future research.

In silico evaluation of inhibitors of Plasmodium falciparumAP2‐I transcription factor

Recent treatment failures observed for Artemisinin‐based combination therapy (ACT) have raised concerns about the efficacy of the front‐line drug to treat malaria and the need to develop a new antimalarial drug regimen. Plasmodium falciparum Apicomplexan Apetala 2 Invasion (PfAP2‐I) transcription factor (TF) is a protein that regulates the expression of a subset of gene families involved in Plasmodium falciparum red blood cell (RBC) invasion. Inhibiting PfAP2‐I TF with small molecules represents a potential new antimalarial therapeutic target to combat drug resistance, which is the aim of this study. The 3D model structure of PfAP2‐I was predicted ab initio using ITASSER and ROBETTA prediction tools and was validated using Errat and Procheck from the Save server 6.0. Computed Atlas of Surface Topography of proteins (CASTp) 3.0 and ConCavity were used to predict the active sites of the PfAP2‐I 3D7 modeled structure. Pharmacophore modeling of the control ligand (3W7 from COACH server) and modeled 3D structure of PfAP2‐I was carried out using the Pharmit server to obtain several compounds for docking analysis. Chimera software was used to remove the complexed ligands, and the modeled protein structure was defined as a receptor. Virtual screening and post‐screening studies were conducted using AutoDock vina and LigPlot. The designed ligands’ toxicity predictions and in silico drug‐likeness were performed using the Swiss ADME predictor and OSIRIS Property Explorer. The modeled protein from the ROBETTA prediction tool was prioritized based on structure validation results of 96.827 for ERRAT and 90.2% of the amino acid residues in the most favored region for the Ramachandran plot. A total of 8656 compounds obtained from six (6) databases on the Pharmit server were used to prepare the ligand library and screened against the prepared 3D model structure of PfAP2‐I, considering the active sites predicted from CASTp and ConCavity. Six (6) best hits were selected based on the binding affinity to the active site PfAP2‐I and were considered for post‐screening analyses. The six compounds exhibited dock score values (between ‐9.9 to ‐10.2 kcal/mol), having lower binding energies than the standard drug ‐ Chloroquine (‐5.10 kcal/mol). The best dock score was compound ZINC97139187 (‐10.2 kcal/mol). For the ADMET properties, compound ZINC97139187 had the highest drug score of 0.63, followed by compound 154861216 with a drug score of 0.58 (both higher than that of the standard drug ‐ chloroquine of 0.25). The good, estimated binding energies and drug score values observed for compound ZINC97139187 and compound 154861216 suggest that they can be considered possible PfAP2‐I inhibitors. Further pre‐clinical experimental validations should be carried out to ascertain the efficacy of these predicted best hits.

Forest malaria and prospects for anti-malarial chemoprophylaxis among forest goers: findings from a qualitative study in Thailand

BackgroundAcross the Greater Mekong Subregion, malaria remains a dangerous infectious disease, particularly for people who visit forested areas where residual transmission continues. Because vector control measures offer incomplete protection to forest goers, chemoprophylaxis has been suggested as a potential supplementary measure for malaria prevention and control. To implement prophylaxis effectively, additional information is needed to understand forest goers’ activities and their willingness to use malaria prevention measures, including prophylaxis, and how it could be delivered in communities. Drawing on in-depth interviews with forest goers and stakeholders, this article examines the potential acceptability and implementation challenges of malaria prophylaxis for forest goers in northeast Thailand.MethodsIn-depth interviews were conducted with forest goers (n = 11) and stakeholders (n = 16) including healthcare workers, community leaders, and policymakers. Interviews were audio-recorded, transcribed and coded using NVivo, employing an inductive and deductive approach, for thematic analysis.ResultsForest goers were well aware of their (elevated) malaria risk and reported seeking care for malaria from local health care providers. Forest goers and community members have a close relationship with the forest but are not a homogenous group: their place and time-at-risk varied according to their activities and length of stay in the forest. Among stakeholders, the choice and cost of anti-malarial prophylactic regimen—its efficacy, length and complexity, number of tablets, potential side effects, and long-term impact on users—were key considerations for its feasibility. They also expressed concern about adherence to the preventive therapy and potential difficulty treating malaria patients with the same regimen. Prophylaxis was considered a low priority in areas with perceived accessible health system and approaching malaria elimination.ConclusionsIn the context of multi-drug resistance, there are several considerations for implementing malaria prophylaxis: the need to target forest goers who are at-risk with a clear period of exposure, to ensure continued use of vector control measures and adherence to prophylactic anti-malarials, and to adopt an evidence-based approach to determine an appropriate regimen. Beyond addressing current intervention challenges and managing malaria incidence in low-transmission setting, it is crucial to keep malaria services available and accessible at the village level especially in areas home to highly mobile populations.

Mechanistic Modeling of Primaquine Pharmacokinetics, Gametocytocidal Activity, and Mosquito Infectivity.

Clinical studies have shown that adding a single 0.25 mg base/kg dose of primaquine to standard antimalarial regimens rapidly sterilizes Plasmodium falciparum gametocytes. However, the mechanism of action and overall impact on malaria transmission is still unknown. Using data from 81 adult Malians with P. falciparum gametocytemia who received the standard dihydroartemisinin‐piperaquine treatment course and were randomized to receive either a single dose of primaquine between 0.0625 and 0.5 mg base/kg or placebo, we characterized the pharmacokinetic‐pharmacodynamic relationships for transmission blocking activity. Both gametocyte clearance and mosquito infectivity were assessed. A mechanistically linked pharmacokinetic‐pharmacodynamic model adequately described primaquine and carboxy‐primaquine pharmacokinetics, gametocyte dynamics, and mosquito infectivity at different clinical doses of primaquine. Primaquine showed a dose‐dependent gametocytocidal effect that precedes clearance. A single low dose of primaquine (0.25 mg/kg) rapidly prevented P. falciparum transmissibility.

Co-administration effects and toxicity profile of ethyl acetate fraction of Stemonocoleus micranthus Harms and Artesunate in murine malaria model

The increasing reports of multi-drug resistant malaria has necessitated the continuous search for new drug candidates, enhancing the efficacy and life span of existing agents. The study aims at evaluating antimalarial potentials and safety use of ethyl acetate fraction of Stemonocoleus micranthus Harms (SM-EF) in co-administration with antimalarial artesunate. Ethyl acetate fraction from 80% methanolic leaf extract was investigated for antimalarial activity in single and combination with different doses of artesunate (2.5, 5 and 10 mg kg−1) against Plasmodium berghei in mice. The parameters measured were curative effect against established infection, mean survival time (MST), weight loss, rectal temperature changes and packed cell volume (PCV). Histopathological study was done on concerned internal organs. The daily monitored curative effect of SM-EF used singly and in combination with artesunate showed a daily, dose-dependent and progressively reduction of malaria parasite. Ethyl acetate fraction of Stemonocoleus micranthus Harms used alone showed a poor onset of activity but long acting effect. On day 9, percentage inhibition effect was 86.78, 85.42, 92.98, 100, 91.19 and 100% for SM-EF, SM-EF-artesunate 2.3, 5 and 10 mg kg-1, artesunate 10 mg kg−1 and chloroquine 10 mg kg−1 respectively. Highest MST was chloroquine (21 days) and SM-EF-artesunate 10 mg kg−1 (19.5 days). Safety study of the harvested organs showed no untoward effect. The combination of SM-EF with artesunate 10 mg kg−1, showed an enhanced antimalarial activity. This study supports the basis for the suggestion of SM-EF as a prospective drug candidate in antimalarial drug combinations regimen.

Long-term safety of the tafenoquine antimalarial chemoprophylaxis regimen: A 12-month, randomized, double-blind, placebo-controlled trial

BackgroundTafenoquine is a long-acting 8-aminoquinoline approved for antimalarial prophylaxis for ≤6 months. Additional data is needed to establish the drug's longer-term safety profile, including potential ophthalmic or neuropsychiatric effects. MethodThis was a randomized, double-blind, placebo-controlled trial in 600 healthy adults. Eligible subjects were randomized 1:1 to receive tafenoquine 200 mg weekly (antimalarial prophylactic regimen) or placebo for 52 weeks. Scheduled safety visits occurred at Weeks 4, 12, 24, 52 (dosing completed), and 64 (final follow-up). Safety assessments included ophthalmic changes, general and neuropsychiatric adverse events (AEs), and laboratory value changes. ResultsThe percentage of subjects with a protocol-defined Serious Ophthalmic Safety Event was lower in the Tafenoquine Group (18.2%) versus the Placebo Group (19%, p = 0.308). There was no significant difference between the percentages of subjects with at least one AE in the Tafenoquine Group (91.0%) versus Placebo (89.9%, p = 0.65). Common AEs seen at a significantly higher incidence for tafenoquine included reversible cornea verticillata (54.5%) and nausea (13.0%), leading to 0.0% and 0.7% discontinuations. Psychiatric AEs occurred at similar percentages in both study groups. Reversible changes in hemoglobin, methemoglobin, creatinine, and blood urea nitrogen (BUN) were noted. ConclusionsThis study supports the safety of extended 52-week tafenoquine prophylaxis. Clinical trial registration Number/ClinicalTrials.gov IdentifierNCT03320174.

Knowledge, Treatment-Seeking, and Socioeconomic Impact of Malaria on the Essequibo Coast of Guyana

The study was conducted to provide insight into malaria control efforts in Guyana, and to identify areas to emphasize in future educational campaigns. To do this, a community-based survey of knowledge, treatment-seeking patterns, and socio-economic impact of malaria was conducted at four outdoor markets in Region 2 Guyana. One hundred and eight individuals between the ages of 16 and 65 who had a malaria infection in the previous twelve months were interviewed. Within the study population, 94% identified mosquitoes as being the source of malaria infection. More than 70% of respondents identified fever, headache and chills as symptoms of malaria. Sixty percent of individuals incorrectly believed that women could not be treated with antimalarials when pregnant or they risked spontaneous abortion or congenital defects. Most individuals (76%) used bed nets although very few nets were chemically treated. Mean delay in presentation to a health clinic was 6.3 days. Use of the official health care sector was high (96%) and relatively few individuals (15%) self-treated with antimalarials. Compliance with antimalarial regimens was also found to be relatively good (92%). Cost of treatment was significantly higher among those who used private clinics (US$ 13.74) than those who used public clinics (US$ 0.96) (p &lt; 0.001). The good level of knowledge of malaria may be due to the relatively high literacy rate and level of education in Guyana. The fact that public clinics in Guyana provide treatment and antimalarials at no cost may explain the relatively high use of the official health sector, low levels of self-treatment, and good compliance.