A randomized, double-blind, phase 2b study to investigate the efficacy, safety, tolerability and pharmacokinetics of a single-dose regimen of ferroquine with artefenomel in adults and children with uncomplicated Plasmodium falciparum malaria.

BACKGROUND: For uncomplicated Plasmodium falciparum malaria, highly efficacious single-dose treatments are expected to increase compliance and improve treatment outcomes, and thereby may slow the development of resistance. The efficacy and safety of a single-dose combination of artefenomel (800 mg) plus ferroquine (400/600/900/1200 mg doses) for the treatment of uncomplicated P. falciparum malaria were evaluated in Africa (focusing on children ≤ 5 years) and Asia. METHODS: The study was a randomized, double-blind, single-dose, multi-arm clinical trial in patients aged > 6 months to < 70 years, from six African countries and Vietnam. Patients were followed up for 63 days to assess treatment efficacy, safety and pharmacokinetics. The primary efficacy endpoint was the polymerase chain reaction (PCR)-adjusted adequate clinical and parasitological response (ACPR) at Day 28 in the Per-Protocol [PP] Set comprising only African patients ≤ 5 years. The exposure-response relationship for PCR-adjusted ACPR at Day 28 and prevalence of kelch-13 mutations were explored. RESULTS: A total of 373 patients were treated: 289 African patients ≤ 5 years (77.5%), 64 African patients > 5 years and 20 Asian patients. None of the treatment arms met the target efficacy criterion for PCR-adjusted ACPR at Day 28 (lower limit of 95% confidence interval [CI] > 90%). PCR-adjusted ACPR at Day 28 [95% CI] in the PP Set ranged from 78.4% [64.7; 88.7%] to 91.7% [81.6; 97.2%] for the 400 mg to 1200 mg ferroquine dose. Efficacy rates were low in Vietnamese patients, ranging from 20 to 40%. A clear relationship was found between drug exposure (artefenomel and ferroquine concentrations at Day 7) and efficacy (primary endpoint), with higher concentrations of both drugs resulting in higher efficacy. Six distinct kelch-13 mutations were detected in parasite isolates from 10/272 African patients (with 2 mutations known to be associated with artemisinin resistance) and 18/20 Asian patients (all C580Y mutation). Vomiting within 6 h of initial artefenomel administration was common (24.6%) and associated with lower drug exposures. CONCLUSION: The efficacy of artefenomel/ferroquine combination was suboptimal in African children aged ≤ 5 years, the population of interest, and vomiting most likely had a negative impact on efficacy. Trial registration ClinicalTrials.gov, NCT02497612. Registered 14 Jul 2015, https://clinicaltrials.gov/ct2/show/NCT02497612?term=NCT02497612&draw=2&rank=1.

Intramuscular Artesunate for Severe Malaria in African Children: A Multicenter Randomized Controlled Trial.

BACKGROUND: Current artesunate (ARS) regimens for severe malaria are complex. Once daily intramuscular (i.m.) injection for 3 d would be simpler and more appropriate for remote health facilities than the current WHO-recommended regimen of five intravenous (i.v.) or i.m. injections over 4 d. We compared both a three-dose i.m. and a three-dose i.v. parenteral ARS regimen with the standard five-dose regimen using a non-inferiority design (with non-inferiority margins of 10%). METHODS AND FINDINGS: This randomized controlled trial included children (0.5-10 y) with severe malaria at seven sites in five African countries to assess whether the efficacy of simplified three-dose regimens is non-inferior to a five-dose regimen. We randomly allocated 1,047 children to receive a total dose of 12 mg/kg ARS as either a control regimen of five i.m. injections of 2.4 mg/kg (at 0, 12, 24, 48, and 72 h) (n = 348) or three injections of 4 mg/kg (at 0, 24, and 48 h) either i.m. (n = 348) or i.v. (n = 351), both of which were the intervention arms. The primary endpoint was the proportion of children with ≥ 99% reduction in parasitemia at 24 h from admission values, measured by microscopists who were blinded to the group allocations. Primary analysis was performed on the per-protocol population, which was 96% of the intention-to-treat population. Secondary analyses included an analysis of host and parasite genotypes as risks for prolongation of parasite clearance kinetics, measured every 6 h, and a Kaplan-Meier analysis to compare parasite clearance kinetics between treatment groups. A post hoc analysis was performed for delayed anemia, defined as hemoglobin ≤ 7 g/dl 7 d or more after admission. The per-protocol population was 1,002 children (five-dose i.m.: n = 331; three-dose i.m.: n = 338; three-dose i.v.: n = 333); 139 participants were lost to follow-up. In the three-dose i.m. arm, 265/338 (78%) children had a ≥ 99% reduction in parasitemia at 24 h compared to 263/331 (79%) receiving the five-dose i.m. regimen, showing non-inferiority of the simplified three-dose regimen to the conventional five-dose regimen (95% CI -7, 5; p = 0.02). In the three-dose i.v. arm, 246/333 (74%) children had ≥ 99% reduction in parasitemia at 24 h; hence, non-inferiority of this regimen to the five-dose control regimen was not shown (95% CI -12, 1; p = 0.24). Delayed parasite clearance was associated with the N86YPfmdr1 genotype. In a post hoc analysis, 192/885 (22%) children developed delayed anemia, an adverse event associated with increased leukocyte counts. There was no observed difference in delayed anemia between treatment arms. A potential limitation of the study is its open-label design, although the primary outcome measures were assessed in a blinded manner. CONCLUSIONS: A simplified three-dose i.m. regimen for severe malaria in African children is non-inferior to the more complex WHO-recommended regimen. Parenteral ARS is associated with a risk of delayed anemia in African children. TRIAL REGISTRATION: Pan African Clinical Trials Registry PACTR201102000277177.

Increase in malaria prevalence and age of at risk population in different areas of Gabon.

BACKGROUND: Following the deployment of new recommendations for malaria control according to the World Health Organization, an estimation of the real burden of the disease is needed to better identify populations at risk and to adapt control strategies. The aim of the present study was to estimate the clinical burden of malaria among febrile children aged less than 11 years, before and after six-year of deployment of malaria control strategies in different areas of Gabon. METHODS: Cross-sectional surveys were carried out in health care facilities at four locations: two urban areas (Libreville and Port-Gentil), one semi-urban area (Melen) and one rural area (Oyem), between 2005 and 2011. Febrile paediatric patients, aged less than 11 years old were screened for malaria using microscopy. Body temperature, history of fever, age, sex, and location were collected. RESULTS: A total of 16,831 febrile children were enrolled; 78.5% (n=13,212) were less than five years old. The rate of Plasmodium falciparum-infection was the lowest in Port-gentil (below 10%) and the highest at Oyem (above 35%). Between 2005 and 2008, malaria prevalence dropped significantly from 31.2% to 18.3%, followed by an increase in 2011 in Libreville (24.1%), Port-Gentil (6.5%) and Oyem (44.2%) (p<0.01). Median age among the infected patients increased throughout the study period reaching 84 (60-108) months in Libreville in 2011 (p<0.01). From 2008, at all sites, children older than five years were more frequently infected; the risk of being infected significantly increased with time, ranging from 0.37 to 1.50 in 2005 and from 2.03 to 5.10 in 2011 in this group (p<0.01). The risk of being P. falciparum-infected in children aged less than five years old significantly decreased from 2008 to 2011 (p<0.01). CONCLUSIONS: This study shows an increased risk of malaria infection in different areas of Gabon with over-five year-old children tending to become the most at-risk population, suggesting a changing epidemiology. Moreover, the heterogeneity of the malaria burden in the country highlights the importance of maintaining various malaria control strategies and redefining their implementation.

Malaria and COVID-19 prevalence in a population of febrile children and adolescents living in Libreville.

Background: Patients with acute febrile illness need to be screened for malaria and coronavirus disease 2019 (COVID-19) in malaria-endemic areas to reduce malaria mortality rates and to prevent the transmission of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Objectives: To estimate the frequency of children and adolescents with COVID-19 and/or malaria among febrile patients attending for malaria diagnosis. Method: This cross-sectional study was conducted in a sentinel site for malaria surveillance during the SARS-CoV-2 pandemic (Omicron variant), from October 2021 to December 2021 in Gabon. All febrile patients were tested for malaria using microscopy. Severe acute respiratory syndrome coronavirus 2 was detected by real time polymerase chain reaction (RT-PCR) and rapid antigen tests developed by Sansure Biotech®. Results: A total of 135 patients were screened. Their median age was 6 (interquartile range [IQR]: 3-14) years. Malaria was confirmed for 49 (36.3%) patients, 29 (32.5%) children, 13 (59.0%) adolescents and 7 (29.2%) adults. The frequency of COVID-19 cases was 7.4% (n = 10/135), and it was comparable between children (n = 6; 6.7%), adolescents (n = 2; 9.1%) and adults (n = 2; 8.3%) (p = 0.17). Malaria and COVID-19 co-infections were diagnosed in 3 (6.1%) patients from all the age groups. Participants with a co-infection had a higher median temperature, a higher median parasitaemia, and were mostly infected with non-falciparum malaria. Conclusion: COVID-19 cases and cases of malaria/COVID-19 co-infections were found in febrile children and adolescents. SARS-CoV-2 testing should be included in the screening of suspected malaria cases. Contribution: This study highlights the presence of malaria-COVID-19 coinfection among children and adolescents who should also be screened for both diseases, like for adults.

Persistence of High In Vivo Efficacy and Safety of Artesunate-Amodiaquine and Artemether-Lumefantrine as the First- and Second-Line Treatments for Uncomplicated Plasmodium falciparum Malaria 10 Years After Their Implementation in Gabon.

PURPOSE: Artesunate-amodiaquine (AS-AQ) and artemether-lumefantrine (AL) have been widely used for the treatment of uncomplicated Plasmodium falciparum malaria since 2005 in Gabon. Since 2011, a rebound of malaria morbidity has been observed in this country, while no survey evaluating ACT efficacy was performed. During the same period, parasite resistance against artemisinin has been reported in Asia. The aim of this study was to assess the efficacy and tolerability of these two drugs in two sentinel sites of Gabon 10 years after their implementation. METHODS: Children aged from 12 to 144 months with uncomplicated malaria were recruited at the Regional Hospital of Melen, Libreville and in the Urban Health Center of Franceville between March 2014 and September 2015. The therapeutic efficacy was evaluated according to the WHO 2008 protocol of 28-day follow-up and PCR-uncorrected/corrected treatment outcomes were assessed. RESULTS: One hundred and eighty-five children (98 ASAQ and 89 AL) were followed up until day 28. The PCR-corrected ACPR was 98.9% for AS-AQ and 96.4% for AL. Late therapeutic failure rate was 3.6% and 1.1% for AL and AS-AQ, respectively (p = 0.2). Adverse events and serious adverse events were rarely observed with both treatments. CONCLUSION: AS-AQ and AL are still efficacious and well-tolerated for the treatment of uncomplicated malaria in Gabonese children.

Correction to: Persistence of High In Vivo Efficacy and Safety of Artesunate-Amodiaquine and Artemether-Lumefantrine as the First- and Second-Line Treatments for Uncomplicated Plasmodium falciparum Malaria 10 Years After Their Implementation in Gabon.

Unfortunately two errors appeared in this article.

Submicroscopic Falciparum Malaria in Febrile Individuals in Urban and Rural Areas of Gabon.

AbstractCharacterization of the parasite reservoir is required to improve malaria control. Asymptomatic patients with subpatent parasitemia have been identified in Gabon, but the prevalence of such infections among febrile subjects is unclear. We assessed the prevalence of submicroscopic Plasmodium falciparum infections on an island (Port-Gentil), and in urban (Libreville), semiurban (Melen), and rural (Oyem) settings in Gabon. Blood samples (N = 310) from febrile patients were tested for malaria parasites by quantitative nucleic acid sequence-based amplification (QT-NASBA). Parasites were detected in 55.8% (173/310) of samples by microscopy and in 66.4% (206/310) of samples by 18S rRNA QT-NASBA. The proportion of submicroscopic infections differed considerably between sites. Gametocytes were found in 1% (3/310) of the individuals by microscopy and in 32% (99/310) by Pfs25 mRNA QT-NASBA. Thus, submicroscopic parasitemia is frequent in febrile patients, and the detection of this condition is important, to improve disease control.

Frequencies of dhfr/dhps multiple mutations and Plasmodium falciparum submicroscopic gametocyte carriage in Gabonese pregnant women following IPTp-SP implementation.

This study analyzed the relationship between intermittent preventive treatment with sulfadoxine-pyrimethamine (SP) (IPTp-SP), the rate of multiple resistant parasites and of submicroscopic gametocyte carriage among pregnant women at the beginning of IPTp implementation in Gabon (2005) and six years after (2011). The detection of pfdhfr and pfdhps gene mutations was performed by PCR-RFLP in Plasmodium (P.) falciparum positive samples collected from pregnant women in 2005 and 2011. Gametocytes carriage was detected by Pfs25mRNA amplification using QT-NASBA. Data were analyzed according to the time of collection (study period) and IPTp-SP doses. The proportion of isolates with at least a triple Pfdhfr mutation (n = 39/42, 92.9% versus 100%, n = 78/78)) and of those isolates with the S108N/C59R/N51I/S436A/A437G multiple mutation (17.9% versus 75.6%) significantly increased between 2005 and 2011 (p<0.01). Mutations I164L and A581G were not found, while higher proportions of 436 and 437 mutations were detected in 2011.A trend toward a higher frequency of isolates with five mutations was observed in women who received two SP doses (p<0.01). Pfs25mRNA was found in 6.8 % (n = 3/44) and 34.6% (n = 27/78) of the samples collected in 2005 and 2011 respectively (p<0.01). In 2011, 74.0% (n = 20/27) of women with detected submicroscopic gametocytes carried parasites with the S108N/C59R/N51/S436A/A437G multiple mutation. All the ten delivering women who received three IPTp-SP doses had a submicroscopic Plasmodium falciparum infection, but none had detected gametocytes. Following IPTp-SP implementation, an increase in the frequency of multiple mutant parasites and of submicroscopic gametocyte carriage was observed among pregnant women living in Gabon.

Molecular Detection of Plasmodium falciparum Infection in Matched Peripheral and Placental Blood Samples from Delivering Women in Libreville, Gabon.

Submicroscopic infections account for more than 50% of all Plasmodium (P.) infections in areas with decreasing malaria prevalence and might contribute to poor pregnancy outcomes. The frequency of submicroscopic P. falciparum infections was assessed in matched peripheral and placental blood samples with microscopy negative or discordant results according to IPTp administration. Methods. P. falciparum infection was detected by nested PCR in matched blood samples collected from delivering women with a history of antimalarial drug treatment and living in Gabon. Results. Submicroscopic P. falciparum infections were detected in 87% (n = 33) of the 44 selected matched samples. Plasmodial DNA was found in 90% (n = 35/39) and 87% (n = 33/38) of microscopy negative peripheral and placental blood samples, respectively. Overall, 95% of samples obtained during the high IPTp-SP coverage period had a submicroscopic infection versus 79% among those from the low coverage period. Conclusion. Submicroscopic infections frequency is high in peripheral and placental blood samples from delivering women with a history of antimalarial treatment whatever the level of IPTp coverage. These data highlight the need of accurate diagnostic tools for a regular antenatal screening of malaria during the pregnancy in endemic areas.

Falciparum malaria as an emerging cause of fever in adults living in Gabon, Central Africa.

Following the observed increase of malaria prevalence among older children in Gabon, a descriptive observational study was carried out in 2012 to determine the prevalence of malaria in adults presenting with fever in two health centres of Libreville, the capital city of Gabon. Thick- and thin-blood smears for malaria diagnosis were performed in febrile individuals aged more than 15 years old. Age, use of bed nets, previous antimalarial drug treatment, clinical symptoms, chest radiography results, and available haemoglobin data were also recorded. Among the 304 patients screened, the global malaria frequency was of 42.1% (n = 128/34). Plasmodium (P). falciparum was the only species identified. The proportion of patients with a clinical malaria requiring parenteral treatment was 38.5%, whereas 47.5% of outpatients had uncomplicated malaria. According to WHO classification, 14 (19.7%) infected patients had severe malaria; neurological and respiratory symptoms tended to be more frequent in case of P. falciparum infection. Anaemia was found in 51.5% adults and none had severe anaemia. Almost half of adults consulting for fever in two health centres of the urban city of Libreville have malaria. The use of insecticide-treated bed nets, the screening, and the treatment of individuals with P. falciparum microscopic and submicroscopic asymptomatic infection or clinical malaria should be emphasized to reduce the transmission.

Pfmdr1 alleles and response to ultralow-dose mefloquine treatment in Gabonese patients.

The identification of parasite molecular markers involved in resistance to antimalarial compounds is of great interest for monitoring the development and spread of resistance in the field. Polymorphisms in Plasmodium falciparum multidrug resistance gene 1 (pfmdr1) have been associated with chloroquine resistance and mefloquine susceptibility. In the present study, carried out in Lambaréné, Gabon, we investigated the relationship between the presence of mutations at codons 86, 184, 1034, 1042, and 1246 in the pfmdr1 gene and the success of ultralow-dose mefloquine treatment (1.1 mg/kg of body weight). Sixty-nine patients were included in the study, and depending on the level of in vivo resistance to mefloquine, they were classified as sensitive responders (S), patients with low-grade resistance (RI), and nonresponders (NR). We found that the prevalences of the Tyr-86 mutation among isolates from patients in groups S, RI, and NR were 100, 96, and 90%, respectively, and that the prevalence of the Phe-184 mutation among the isolates was 80% in each group. A prevalence of about 10% point mutations at codons 1042 and 1246 was detected only in isolates from patients in groups RI and NR. There was no statistically significant association between the presence of the Tyr-86 mutation and the in vivo response (P = 0.79). Among the parasite isolates from patients with drug-resistant infections, 83% had the wild-type pfmdr1 genotype (S(1034)-N(1042)-D(1246)). No link between the presence of this genotype and parasite resistance was detected (P = 0.42). Among the isolates analyzed, 85 had double mutations (Y(86)-F(184) or Y(86)-Y(1246)) and 11 had triple mutations (Y(86)-D(1042)-Y(1246), Y(86)-F(184)-Y(1246), or Y(86)-F(184)-D(1042)). These findings are not consistent with those of previous in vitro studies and suggest that further evaluation of pfmdr1 gene polymorphism and in vivo mefloquine sensitivity are needed.

Antibody responses to Plasmodium falciparum merozoite surface protein-1 and efficacy of amodiaquine in Gabonese children with P. falciparum malaria.

The relationship between the efficacy of amodiaquine for the treatment of uncomplicated Plasmodium falciparum malaria and preexisting antibodies against merozoite surface protein (MSP)-1, a blood-stage P. falciparum antigen, was investigated. The immunoglobulin G antibody response to different MSP-1 recombinant proteins was evaluated in plasma samples from Gabonese children with uncomplicated malaria who were treated with amodiaquine. The prevalence of anti-MSP-1 antibodies was similar among patients with either parasitological and clinical cure after treatment (n=102) or treatment failure (n=51) by day 28 (83% in both groups). However, associations between antibody responses to K1 and MAD20 allelic families and therapeutic success were found (P< .001 and P= .034, respectively). A high proportion of plasma samples recognizing several antigens was found in the cured group. This association was significant even when data were stratified by age, particularly for the K1 family antigens (P= .029). These results suggest that humoral immune responses play a supportive role in the efficacy of amodiaquine treatment.

Fosmidomycin-clindamycin for Plasmodium falciparum Infections in African children.

BACKGROUND: Fosmidomycin is a new antimalarial drug with a novel mechanism of action. Studies in Africa that have evaluated fosmidomycin as monotherapeutic agent demonstrated its excellent tolerance, but 3-times-daily treatment regimens of >or=4 days were required to achieve radical cure, prompting further research to identify and validate a suitable combination partner to enhance its efficacy. METHODS: We conducted a randomized, controlled, open-label study to evaluate the efficacy and safety of fosmidomycin combined with clindamycin (n=12; 30 and 5 mg/kg body weight every 12 h for 5 days, respectively), compared with fosmidomycin alone (n=12; 30 mg/kg body weight every 12 h for 5 days) and clindamycin alone (n=12; 5 mg/kg body weight every 12 h for 5 days) for the clearance of asymptomatic Plasmodium falciparum infections in schoolchildren in Gabon aged 7-14 years. RESULTS: Asexual parasites were rapidly cleared in children treated with fosmidomycin-clindamycin (median time, 18 h) and fosmidomycin alone (25 h) but slowly in children treated with clindamycin alone (71 h; P=.004). However, only treatment with fosmidomycin-clindamycin or clindamycin alone led to the radical elimination of asexual parasites as measured by day 14 and 28 cure rates of 100%. Asexual parasites reappeared by day 28 in 7 children who received fosmidomycin (day 14 cure rate, 92% [11/12; day 28 cure rate, 42% [5/12]). All regimens were well tolerated, and no serious adverse events occurred. CONCLUSION: The combination of fosmidomycin and clindamycin is well tolerated and superior to either agent on its own with respect to the rapid and radical clearance of P. falciparum infections in African children.

Fosmidomycin-clindamycin for the treatment of Plasmodium falciparum malaria.

It has been demonstrated that fosmidomycin has good tolerability and rapid onset of action, but late recrudescences preclude its use alone; in vitro, clindamycin has been shown to act synergistically with fosmidomycin against Plasmodium falciparum. We conducted a study in pediatric outpatients with P. falciparum malaria in Gabon to evaluate the efficacy and safety of an oral combination of fosmidomycin-clindamycin of 30 mg/kg and 10 mg/kg of body weight, respectively, every 12 h. Patients 7-14 years old were recruited in cohorts of 10. The first 10 patients were treated for 5 days. The duration of treatment was then incrementally shortened in intervals of 1 day if >85% of the patients in a cohort were cured by day 14. All dosing regimens were well tolerated, and no serious adverse events occurred. Asexual parasites and fever rapidly cleared in all patients. Cure ratios of 100% on day 14 were achieved with treatment durations of 5 (10/10 patients), 4 (10/10 patients), 3 (10/10 patients), and 2 days (10/10 patients); 1 day of treatment led to a cure ratio of 50% (5/10 patients). Fosmidomycin-clindamycin is safe and well tolerated, and short-course regimens achieved high efficacy in children with P. falciparum malaria. Fosmidomycin-clindamycin is a promising novel treatment option for malaria.