Clinical pharmacokinetics of mefloquine

Advancing liposome technology for innovative strategies against malaria

This review discusses the potential of liposomes as drug delivery systems for antimalarial therapies. Malaria continues to be a significant cause of mortality and morbidity, particularly among children and pregnant women. Drug resistance due to patient non-compliance and troublesome side effects remains a significant challenge in antimalarial treatment. Liposomes, as targeted and efficient drug carriers, have garnered attention owing to their ability to address these issues. Liposomes encapsulate hydrophilic and/or hydrophobic drugs, thus providing comprehensive and suitable therapeutic drug delivery. Moreover, the potential of passive and active drug delivery enables drug concentration in specific target tissues while reducing adverse effects. However, successful liposome formulation is influenced by various factors, including drug physicochemical characteristics and physiological barriers encountered during drug delivery. To overcome these challenges, researchers have explored modifications in liposome nanocarriers to achieve efficient drug loading, controlled release, and system stability. Computational approaches have also been adopted to predict liposome system stability, membrane integrity, and drug-liposome interactions, improving formulation development efficiency. By leveraging computational methods, optimizing liposomal drug delivery systems holds promise for enhancing treatment efficacy and minimizing side effects in malaria therapy. This review consolidates the current understanding and highlights the potential of liposome strategies against malaria.

Suspected Mefloquine Toxicity in a Colony of Humboldt Penguins (Spheniscus humboldti)

Avian malaria is an important cause of mortality in captive penguins housed in outdoor exhibits. Mefloquine was used as a prophylaxis to treat a colony of 19 Humboldt penguins (Spheniscus humboldti) for avian malaria. A target dose of 30 mg/kg was obtained from anecdotal literature for sphenisciforms that was not based on pharmacokinetic or toxicity studies. For this reason, preliminary plasma concentrations of mefloquine were acquired after the first dose in some penguins to ensure that plasma concentrations reached human malaria prophylactic concentrations. Afterward, each penguin in the entire colony received mefloquine (26-31 mg/kg [125 mg in toto] PO q7d). Regurgitation was frequently observed starting after the fourth weekly administration. Plasma concentrations of mefloquine after the seventh dose showed elevated concentrations, and the treatment was immediately terminated. Eight penguins died during and after the treatment period. The first fatality occurred after the fifth weekly administration, and 7 birds died within 7-52 days after the seventh weekly administration. Three penguins were found dead without previous symptoms. The other five presented with marked lethargy, dyspnea, poor appetite, and vomiting, and all died despite medical care. The remaining 11 penguins of the colony survived without any supportive care; 5 did not exhibit any clinical disease signs, while the other 6 showed a mild apathy and decreased appetite. Mefloquine toxicity was highly suspected on the basis of clinical signs, the elevated mefloquine plasma concentrations, and no other underlying pathologic disease conditions identified through postmortem examinations. Nonspecific lesions, including pulmonary congestion and edema and hepatic perivascular hematopoiesis, were noted in the birds that died. Additionally, 1 case presented with myocarditis, and mycobacteria were observed within granulomas in the respiratory tract of 2 penguins. Caution is advised, and further studies are encouraged before administering mefloquine to penguins.

Methylene Blue-Based Combination Therapy with Amodiaquine Prevents Severe Malaria in an Experimental Rodent Model

Untreated malaria can progress rapidly to severe forms (<24 h). Moreover, resistance to antimalarial drugs is a threat to global efforts to protect people from malaria. Given this, it is clear that new chemotherapy must be developed. We contribute new data about using methylene blue (MB) to cure malaria and cerebral malaria in a combined therapy with common antimalarial drugs, including mefloquine (MQ) and amodiaquine (AQ). A C57BL6/J mouse model was used in an experimental cerebral malaria model. Mice were infected with Plasmodium berghei ANKA on Day 0 (D0) and the treatment started on D3 (nearly 1% parasitaemia) with AQ, MQ or MB alone or in combination with AQ or MQ. AQ, MQ and MB alone were unable to prevent cerebral malaria as part of a late chemotherapy. MB-based combination therapies were efficient even if treatment began at a late stage. We found a significant difference in survival rate (p < 0.0001) between MBAQ and the untreated group, but also with the AQ (p = 0.0024) and MB groups (p < 0.0001). All the infected mice treated with MB in combination with AQ were protected from cerebral malaria. Partial protection was demonstrated with MB associated with MQ. In this group, a significant difference was found between MBMQ and the untreated group (p < 0.0001), MQ (p = 0.0079) and MB (p = 0.0039). MB associated with AQ would be a good candidate for preventing cerebral malaria.

An update on pharmacogenetic factors influencing the metabolism and toxicity of artemisinin-based combination therapy in the treatment of malaria

INTRODUCTION

Artemisinin-based combination therapies (ACTs) are recommended first-line antimalarials for uncomplicated Plasmodium falciparum malaria. Pharmacokinetic/pharmacodynamic variation associated with ACT drugs and their effect is documented. It is accepted to an extent that inter-individual variation is genetically driven, and should be explored for optimized antimalarial use.

AREAS COVERED

We provide an update on the pharmacogenetics of ACT antimalarial disposition. Beyond presently used antimalarials, we also refer to information available for the most notable next-generation drugs under development. The bibliographic approach was based on multiple Boolean searches on PubMed covering all recent publications since our previous review.

EXPERT OPINION

The last 10 years have witnessed an increase in our knowledge of ACT pharmacogenetics, including the first clear examples of its contribution as an exacerbating factor for drug-drug interactions. This knowledge gap is still large and is likely to widen as a new wave of antimalarial drug is looming, with few studies addressing their pharmacogenetics. Clinically useful pharmacogenetic markers are still not available, in particular, from an individual precision medicine perspective. A better understanding of the genetic makeup of target populations can be valuable for aiding decisions on mass drug administration implementation concerning region-specific antimalarial drug and dosage options.

Cellular targets of mefloquine

Mefloquine is a quinoline-based compound widely used as an antimalarial drug, particularly in chemoprophylaxis. Although decades of research have identified various aspects of mefloquine's anti-Plasmodium properties, toxic effects offset its robust use in humans. Mefloquine exerts harmful effects in several types of human cells by targeting many of the cellular lipids, proteins, and complexes, thereby blocking a number of downstream signaling cascades. In general, mefloquine modulates several cellular phenomena, such as alteration of membrane potential, induction of oxidative stress, imbalance of ion homeostasis, disruption of metabolism, failure of organelle function, etc., leading to cell cycle arrest and programmed cell death. This review aims to summarize the information on functional and mechanistic findings related to the cytotoxic effects of mefloquine.

Mefloquine, a Potent Anti-severe Acute Respiratory Syndrome-Related Coronavirus 2 (SARS-CoV-2) Drug as an Entry Inhibitor in vitro

Coronavirus disease 2019 (COVID-19) has caused serious public health, social, and economic damage worldwide and effective drugs that prevent or cure COVID-19 are urgently needed. Approved drugs including Hydroxychloroquine, Remdesivir or Interferon were reported to inhibit the infection or propagation of severe acute respiratory syndrome-related coronavirus 2 (SARS-CoV-2), however, their clinical efficacies have not yet been well demonstrated. To identify drugs with higher antiviral potency, we screened approved anti-parasitic/anti-protozoal drugs and identified an anti-malarial drug, Mefloquine, which showed the highest anti-SARS-CoV-2 activity among the tested compounds. Mefloquine showed higher anti-SARS-CoV-2 activity than Hydroxychloroquine in VeroE6/TMPRSS2 and Calu-3 cells, with IC₅₀ = 1.28 μM, IC₉₀ = 2.31 μM, and IC₉₉ = 4.39 μM in VeroE6/TMPRSS2 cells. Mefloquine inhibited viral entry after viral attachment to the target cell. Combined treatment with Mefloquine and Nelfinavir, a replication inhibitor, showed synergistic antiviral activity. Our mathematical modeling based on the drug concentration in the lung predicted that Mefloquine administration at a standard treatment dosage could decline viral dynamics in patients, reduce cumulative viral load to 7% and shorten the time until virus elimination by 6.1 days. These data cumulatively underscore Mefloquine as an anti-SARS-CoV-2 entry inhibitor.

Mefloquine enhances the activity of colistin against antibiotic-resistant Enterobacterales in vitro and in an in vivo animal study

Infections caused by carbapenem-resistant Enterobacterales are difficult to treat. Colistin is the last-resort drug for the treatment of these infections, however colistin resistance has emerged in animals and humans. This study investigated the in vitro efficacy of mefloquine in combination with colistin against 114 antibiotic-resistant Enterobacterales isolates including NDM-1, extended-spectrum β-lactamase (ESBL) and mcr-1 containing strains from a broad range of origins. The effect of the mefloquine and colistin combination was examined in vitro by chequerboard method and time-kill analysis and in vivo in a murine peritoneal infection model. The fractional inhibitory concentration index (FICI) of the combination indicated that synergy was detected for all NDM-1 and mcr-1 containing strains, 87.5% of ESBL producing Escherichia coli and 97.9% of ESBL producing Klebsiella pneumoniae strains. Time-kill curves demonstrated significant synergistic activity with low concentrations of colistin that were boosted by mefloquine. The combination showed enhanced activity against infection with NDM-1- or mcr-1 containing Enterobacteriaceae in mice at 4 h and 6 h after treatment. These findings suggest that the combination of mefloquine and colistin has the potential for rejuvenating the activity of colistin against multidrug-resistant Enterobacterales.

Assay validation and determination of in vitro binding of mefloquine to plasma proteins from clinically normal and FIP-affected cats

The antimalarial agent mefloquine is currently being investigated for its potential to inhibit feline coronavirus and feline calicivirus infections. A simple, high pressure liquid chromatography assay was developed to detect mefloquine plasma concentrations in feline plasma. The assay’s lower limit of quantification was 250 ng/mL. The mean ± standard deviation intra- and inter-day precision expressed as coefficients of variation were 6.83 ± 1.75 and 5.33 ± 1.37%, respectively, whereas intra- and inter-day accuracy expressed as a percentage of the bias were 11.40 ± 3.73 and 10.59 ± 3.88%, respectively. Accordingly, this validated assay should prove valuable for future in vivo clinical trials of mefloquine as an antiviral agent against feline coronavirus and feline calicivirus. However, the proportion of mefloquine binding to feline plasma proteins has not been reported. The proportion of drug bound to plasma protein binding is an important concept when developing drug dosing regimens. As cats with feline infectious peritonitis (FIP) demonstrate altered concentrations of plasma proteins, the proportion of mefloquine binding to plasma proteins in both clinically normal cats and FIP-affected cats was also investigated. An in vitro method using rapid equilibrium dialysis demonstrated that mefloquine was highly plasma protein bound in both populations (on average > 99%).

Pharmacokinetic Profile of Oral Administration of Mefloquine to Clinically Normal Cats: A Preliminary In-Vivo Study of a Potential Treatment for Feline Infectious Peritonitis (FIP)

Simple Summary

In searching for antiviral agents against feline coronaviruses and feline caliciviruses, mefloquine, a human anti-malarial drug, has been demonstrated to reduce viral load of feline coronaviruses and feline calicivirus in infected cells. In this study, mefloquine was administered orally to seven clinically healthy cats twice weekly for four doses and mefloquine concentrations in blood were measured to investigate the pharmacokinetic profile—the movement of drug in the body. The maximum blood concentration of mefloquine was 2.71 ug/mL and was reached 15 h after a single oral dose was administered. Mefloquine side effects included vomiting following administration without food in some cats, and mild increases in symmetric dimethylarginine (SDMA), an early kidney biomarker. This study provides valuable information on mefloquine’s profile in cats as an introductory step towards investigating it as a potential treatment for feline coronavirus and feline calicivirus infection in cats.

Abstract

The pharmacokinetic profile of mefloquine was investigated as a preliminary study towards a potential treatment for feline coronavirus infections (such as feline infectious peritonitis) or feline calicivirus infections. Mefloquine was administered at 62.5 mg orally to seven clinically healthy cats twice weekly for four doses and mefloquine plasma concentrations over 336 h were measured using high pressure liquid chromatography (HPLC). The peak plasma concentration (Cmax) after a single oral dose of mefloquine was 2.71 ug/mL and time to reach Cmax (Tmax) was 15 h. The elimination half-life was 224 h. The plasma concentration reached a higher level at 4.06 ug/mL when mefloquine was administered with food. Adverse effects of dosing included vomiting following administration without food in some cats. Mild increases in serum symmetric dimethylarginine (SDMA), but not creatinine, concentrations were observed. Mefloquine may provide a safe effective treatment for feline coronavirus and feline calicivirus infections in cats.

In vitro hepatic metabolism of mefloquine using microsomes from cats, dogs and the common brush-tailed possum (Trichosurus vulpecula)

Feline infectious peritonitis (FIP) is a systemic, fatal, viral-induced, immune-mediated disease of cats caused by feline infectious peritonitis virus (FIPV). Mefloquine, a human anti-malarial agent, has been shown to inhibit FIPV in vitro. As a first step to evaluate its efficacy and safety profile as a potential FIP treatment for cats, mefloquine underwent incubation in feline, canine and common brush-tailed possum microsomes and phase I metabolism cofactors to determine its rate of phase I depletion. Tramadol was used as a phase I positive control as it undergoes this reaction in both dogs and cats. Using the substrate depletion method, the in vitro intrinsic clearance (mean ± S.D.) of mefloquine by pooled feline and common brush-tailed possum microsomes was 4.5 ± 0.35 and 18.25 ± 3.18 μL/min/mg protein, respectively. However, phase I intrinsic clearance was too slow to determine with canine microsomes. Liquid chromatography-mass spectrometry (LC-MS) identified carboxymefloquine in samples generated by feline microsomes as well as negative controls, suggesting some mefloquine instability. Mefloquine also underwent incubation with feline, canine and common brush-tailed possum microsomes and phase II glucuronidative metabolism cofactors. O-desmethyltramadol (ODMT or M1) was used as a positive control as it undergoes a phase II glucuronidation reaction in these species. The rates of phase II mefloquine depletion by microsomes by all three species were too slow to estimate. Therefore mefloquine likely undergoes phase I hepatic metabolism catalysed by feline and common brush-tailed possum microsomes but not phase II glucuronidative metabolism in all three species and mefloquine is not likely to have delayed elimination in cats with clinically normal, hepatic function.

Screening Marine Natural Products for New Drug Leads against Trypanosomatids and Malaria

Neglected Tropical Diseases (NTD) represent a serious threat to humans, especially for those living in poor or developing countries. Almost one-sixth of the world population is at risk of suffering from these diseases and many thousands die because of NTDs, to which we should add the sanitary, labor and social issues that hinder the economic development of these countries. Protozoan-borne diseases are responsible for more than one million deaths every year. Visceral leishmaniasis, Chagas disease or sleeping sickness are among the most lethal NTDs. Despite not being considered an NTD by the World Health Organization (WHO), malaria must be added to this sinister group. Malaria, caused by the apicomplexan parasite Plasmodium falciparum, is responsible for thousands of deaths each year. The treatment of this disease has been losing effectiveness year after year. Many of the medicines currently in use are obsolete due to their gradual loss of efficacy, their intrinsic toxicity and the emergence of drug resistance or a lack of adherence to treatment. Therefore, there is an urgent and global need for new drugs. Despite this, the scant interest shown by most of the stakeholders involved in the pharmaceutical industry makes our present therapeutic arsenal scarce, and until recently, the search for new drugs has not been seriously addressed. The sources of new drugs for these and other pathologies include natural products, synthetic molecules or repurposing drugs. The most frequent sources of natural products are microorganisms, e.g., bacteria, fungi, yeasts, algae and plants, which are able to synthesize many drugs that are currently in use (e.g. antimicrobials, antitumor, immunosuppressants, etc.). The marine environment is another well-established source of bioactive natural products, with recent applications against parasites, bacteria and other pathogens which affect humans and animals. Drug discovery techniques have rapidly advanced since the beginning of the millennium. The combination of novel techniques that include the genetic modification of pathogens, bioimaging and robotics has given rise to the standardization of High-Performance Screening platforms in the discovery of drugs. These advancements have accelerated the discovery of new chemical entities with antiparasitic effects. This review presents critical updates regarding the use of High-Throughput Screening (HTS) in the discovery of drugs for NTDs transmitted by protozoa, including malaria, and its application in the discovery of new drugs of marine origin.

Role of P-glycoprotein in the brain disposition of seletalisib: Evaluation of the potential for drug-drug interactions

Seletalisib is an orally bioavailable selective inhibitor of phosphoinositide 3-kinase delta (PI3Kδ) in clinical development for the treatment of immune-mediated inflammatory diseases. The present study investigated the role of P-gp in seletalisib disposition, especially brain distribution, and the associated risks of interactions. Seletalisib was found to be actively transported by rodent and human P-gp in vitro (transfected LLC-PK1 cells; K_m of ca. 20 µM), with minimal or no affinity for the other tested transporters. A distribution study in knockout rats (single oral dosing at 750 mg kg^-1) showed that P-gp restricts the brain disposition of seletalisib while having minimal effect on its intestinal absorption. Restricted brain penetration was also observed in cynomolgus monkeys (single oral dosing at 30 mg kg^-1) using brain microdialysis and cerebrospinal fluid sampling (K_p,uu of 0.09 and 0.24, respectively). These findings opened the question of potential pharmacokinetic interaction between seletalisib and P-gp inhibitors. In vitro, CsA inhibited the active transport of seletalisib with an IC₅₀ of 0.13 µM. In rats, co-administration of high doses of CsA (bolus iv followed by continuous infusion) increased the brain distribution of seletalisib (single oral dosing at 5 mg kg^-1). The observed data were found aligned with those predicted by in vitro-in vivo extrapolation. Based on the same extrapolation method combined with literature data, only very few P-gp inhibitors (i.e. CsA, quinine, quinidine) were predicted to increase the brain disposition of seletalisib in the clinical setting (maximal 3-fold changes).

A cluster of the first reported Plasmodium ovale spp. infections in Peru occuring among returning UN peace-keepers, a review of epidemiology, prevention and diagnostic challenges in nonendemic regions

BACKGROUND

Plasmodium ovale curtisi and Plasmodium ovale wallikeri are regarded as less virulent forms of malaria with a geographic distribution including Southeast Asia, Central and West Africa, and is increasingly reported as an infection in returning travellers. A species of malaria that may have delayed or relapsing presentations similar to Plasmodium vivax, the clinical presentation of P. ovale spp. has been described to have prepatent periods of 2 weeks or slightly longer with reports of relapse following primary infection out to 8-9 months. This presentation may be obscured further in the setting of anti-malarial exposure, with report of delayed primary infection out to 4 years. Presented is a cluster of 4 imported P. ovale spp. cases in returning Peruvian military personnel assigned to United Nations peace-keeping operations in the Central African Republic.

CASE PRESENTATION

From January to December 2016, Peruvian peace-keepers were deployed in support of United Nations (UN) operations in the Central African Republic (CAR). While serving abroad, Navy, Army, and Air Force members experienced 223 episodes of Plasmodium falciparum malaria following interruption of prophylaxis with mefloquine. Diagnosis was made using rapid diagnostics tests (RDTs) and/or smear with no coinfections identified. Cases of malaria were treated with locally-procured artemether-lumefantrine. Returning to Peru in January 2017, 200 peace-keepers were screened via thick and thin smear while on weekly mefloquine prophylaxis with only 1 showing nucleic acid within red blood cells consistent with Plasmodium spp. and 11 reporting syndromes of ill-defined somatic complaints. Between a period of 5 days to 11 months post return, 4 cases of P. ovale spp. were diagnosed using smear and polymerase chain reaction (PCR) following febrile complaints. All cases were subsequently treated with chloroquine and primaquine, with cure of clinical disease and documented clearance of parasitaemia.

CONCLUSION

These patients represent the first imported cases in Peru of this species of malaria as well as highlight the challenges in implementing population level prophylaxis in a deployed environment, and the steps for timely diagnosis and management in a non-endemic region where risk of introduction for local transmission exists.

A Cinchona Alkaloid Antibiotic That Appears To Target ATP Synthase in Streptococcus pneumoniae

Optochin, a cinchona alkaloid derivative discovered over 100 years ago, possesses highly selective antibacterial activity toward Streptococcus pneumoniae. Pneumococcal disease remains the leading source of bacterial pneumonia and meningitis worldwide. The structure-activity relationships of optochin were examined through modification to both the quinoline and quinuclidine subunits, which led to the identification of analogue 48 with substantially improved activity. Resistance and molecular modeling studies indicate that 48 likely binds to the c-ring of ATP synthase near the conserved glutamate 52 ion-binding site, while mechanistic studies demonstrated that 48 causes cytoplasmic acidification. Initial pharmacokinetic and drug metabolism analyses of optochin and 48 revealed limitations of these quinine analogues, which were rapidly cleared, resulting in poor in vivo exposure through hydroxylation pendants to the quinuclidine and O-dealkylation of the quinoline. Collectively, the results provide a foundation to advance 48 and highlight ATP synthase as a promising target for antibiotic development.

A novel cell-free method to culture Schistosoma mansoni from cercariae to juvenile worm stages for in vitro drug testing

Background

The arsenal in anthelminthic treatment against schistosomiasis is limited and relies almost exclusively on a single drug, praziquantel (PZQ). Thus, resistance to PZQ could constitute a major threat. Even though PZQ is potent in killing adult worms, its activity against earlier stages is limited. Current in vitro drug screening strategies depend on newly transformed schistosomula (NTS) for initial hit identification, thereby limiting sensitivity to new compounds predominantly active in later developmental stages. Therefore, the aim of this study was to establish a highly standardized, straightforward and reliable culture method to generate and maintain advanced larval stages in vitro. We present here how this method can be a valuable tool to test drug efficacy at each intermediate larval stage, reducing the reliance on animal use (3Rs).

Methodology/Principal findings

Cercariae were mechanically transformed into skin-stage (SkS) schistosomula and successfully cultured for up to four weeks with no loss in viability in a commercially available medium. Under these serum- and cell-free conditions, development halted at the lung-stage (LuS). However, the addition of human serum (HSe) propelled further development into liver stage (LiS) worms within eight weeks. Skin and lung stages, as well as LiS, were submitted to 96-well drug screening assays using known anti-schistosomal compounds such as PZQ, oxamniquine (OXM), mefloquine (MFQ) and artemether (ART). Our findings showed stage-dependent differences in larval susceptibility to these compounds.

Conclusion

With this robust and highly standardized in vitro assay, important developmental stages of S. mansoni up to LiS worms can be generated and maintained over prolonged periods of time. The phenotype of LiS worms, when exposed to reference drugs, was comparable to most previously published works for ex vivo harvested adult worms. Therefore, this in vitro assay can help reduce reliance on animal experiments in search for new anti-schistosomal drugs.

Schistosomiasis remains a major health threat, predominantly in developing countries. Even though there has been some progress in search of new drugs, praziquantel remains the only available drug. Probably the most important advance in the search for new drugs was in vitro transformation of cercariae and their subsequent culture. However, hit identification in compound screenings is exclusively tested in skin stage parasites and is only confirmed for more mature worms in a subsequent step. This is in part due to the lack of an easy culture system for advance-stage parasites. We present here a reliable and highly standardized way to generate LiS worms in vitro in a cell-free culture system. The inclusion of in vitro drug tests on advanced-stage parasites in initial hit identification will help to identify compounds that might otherwise be overlooked. Furthermore, the ability to continuously observe the parasite’s development in vitro will provide an important platform for a better understanding of its maturation in the human host. Taken together, this opens up new avenues to investigate the influence of specific cell types or host proteins on the development of Schistosoma mansoni and provides an additional tool to reduce animal use in future drug discovery efforts (3Rs).

Population Pharmacokinetics of Mefloquine Intermittent Preventive Treatment for Malaria in Pregnancy in Gabon

Mefloquine was evaluated as an alternative for intermittent preventive treatment of malaria in pregnancy (IPTp) due to increasing resistance against the first-line drug sulfadoxine-pyrimethamine (SP). This study determined the pharmacokinetic characteristics of the mefloquine stereoisomers and the metabolite carboxymefloquine (CMQ) when given as IPTp in pregnant women. Also, the relationship between plasma concentrations of the three analytes and cord samples was evaluated, and potential covariates influencing the pharmacokinetic properties were assessed. A population pharmacokinetic analysis was performed with 264 pregnant women from a randomized controlled trial evaluating a single and a split-dose regimen of two 15-mg/kg mefloquine doses at least 1 month apart versus SP-IPTp. Both enantiomers of mefloquine and its carboxy-metabolite (CMQ), measured in plasma and cord samples, were applied for pharmacokinetic modelling using NONMEM 7.3. Both enantiomers and CMQ were described simultaneously by two-compartment models. In the split-dose group, mefloquine bioavailability was significantly increased by 5%. CMQ induced its own metabolism significantly. Maternal and cord blood concentrations were significantly correlated (r ² = 0.84) at delivery. With the dosing regimens investigated, prophylactic levels are not constantly achieved. A modeling tool for simulation of the pharmacokinetics of alternative mefloquine regimens is presented. This first pharmacokinetic characterization of mefloquine IPTp indicates adequate exposure in both mefloquine regimens; however, concentrations at delivery were below previously suggested threshold levels. Our model can serve as a valuable tool for researchers and clinicians to develop and optimize alternative dosing regimens for IPTp in pregnant women.

Development of a physiologically based pharmacokinetic model for mefloquine and its application alongside a clinical effectiveness model to select an optimal dose for prevention of malaria in young Caucasian children

AIMS

To predict the optimal chemoprophylactic dose of mefloquine in infants of 5-10 kg using physiologically based pharmacokinetic (PBPK) and clinical effectiveness models.

METHODS

The PBPK model was developed in Simcyp version 14.1 and verified against clinical pharmacokinetic data in adults; the final model, accounting for developmental physiology and enzyme ontogeny was then applied in the paediatric population. The clinical effectiveness model utilized real-world chemoprophylaxis data with stratification of output by age and including infant data from the UK population.

RESULTS

PBPK simulations in infant populations depend on the assumed fraction of mefloquine metabolized by CYP3A4 (0.47, 0.95) and on the associated CYP3A4 ontogeny (Salem, Upreti). However, all scenarios suggest that a dose of 62.5 mg weekly achieves or exceeds the exposure in adults following a 250 mg weekly dose and results in a minimum plasma concentration of 620 ng ml^-1 , which is considered necessary to achieve 95% prophylactic efficacy. The clinical effectiveness model predicts a 96% protective efficacy from mefloquine chemoprophylaxis at 62.5 mg weekly.

CONCLUSIONS

The PBPK and clinical effectiveness models are mutually supportive and suggest a prophylactic dose of 62.5 mg weekly in the Caucasian 5-10 kg infant population travelling to endemic countries. This dual approach offers a novel route to dose selection in a vulnerable population, where clinical trials would be difficult to conduct.

Pharmacokinetics of mefloquine administered with artesunate in patients with uncomplicated falciparum malaria from the Brazilian Amazon basin

Background

A fixed-dose combination of mefloquine with artesunate was evaluated in cases of falciparum malaria in the Brazilian Amazon basin with acceptable efficacy, safety and tolerability. However, there are no data on the pharmacokinetics of mefloquine in this coformulation in Brazil, which is valuable to evaluate whether Plasmodium is exposed to an effective concentration of the drug.

Methods

A prospective, single-arm study was conducted in male patients with slide-confirmed infection by Plasmodium falciparum using two tablets of a fixed-dose combination of artesunate (100 mg) and mefloquine base (200 mg) once daily and over 3 consecutive days. Serial blood samples were collected at admission and throughout 672 h post-administration of the drugs. Mefloquine was measured in each blood sample by high-performance liquid chromatography. The pharmacokinetic parameters were determined by non-compartmental analysis.

Results

A total of 61 patients were enrolled in the study and 450 whole blood samples were collected for mefloquine measurement. The mefloquine half-life was 10.25 days, the maximum concentration (C_max) was 2.53 µg/ml, the area-under-the-curve (AUC_0–∞) was 359 µg^/ml h, the observed clearance (Cl/f) was 0.045 l/kg/h and the volume of distribution (V/f) was 14.6 l/kg. Mefloquine concentrations above 0.5 µg/ml were sustained for a mean time of 9.2 days.

Conclusion

The pharmacokinetic parameters of mefloquine determined in the study suggest an adequate exposure of parasite to mefloquine in the multiple oral dose regimen of the fixed dose combination of mefloquine and artesunate.

An Inexpensive, In-House-Made, Microdialysis Device for Measuring Drug-Protein Binding

An inexpensive, in-house made microdialysis device is described that is suitable for measuring the binding of small molecules including drug candidates to serum proteins or other macromolecules. The device is based on the standard equilibrium dialysis method to measure the fraction of low molecular weight compound bound to proteins. It is constructed from a standard polypropylene 96-well plate, dialysis tubing, and low viscosity epoxy resin. The device can be readily prepared for a small fraction of the cost of a commercial, multichamber microdialysis device. Drug-protein binding results are provided, which validates the device.

Pharmacokinetic Interactions for Drugs with a Long Half-Life—Evidence for the Need of Model-Based Analysis

Pharmacokinetic drug-drug interactions (DDIs) can lead to undesired drug exposure, resulting in insufficient efficacy or aggravated toxicity. Accurate quantification of DDIs is therefore crucial but may be difficult when full concentration-time profiles are problematic to obtain. We have compared non-compartmental analysis (NCA) and model-based predictions of DDIs for long half-life drugs by conducting simulation studies and reviewing published trials, using antituberculosis drug bedaquiline (BDQ) as a model compound. Furthermore, different DDI study designs were evaluated. A sequential design mimicking conducted trials and a population pharmacokinetic (PK) model of BDQ and the M2 metabolite were utilized in the simulations where five interaction scenarios from strong inhibition (clearance fivefold decreased) to strong induction (clearance fivefold increased) were evaluated. In trial simulations, NCA systematically under-predicted the DDIs’ impact. The bias in average exposure was 29–96% for BDQ and 20–677% for M2. The model-based analysis generated unbiased predictions, and simultaneous fitting of metabolite data increased precision in DDI predictions. The discrepancy between the methods was also apparent for conducted trials, e.g., lopinavir/ritonavir was predicted to increased BDQ exposure 22% by NCA and 188% by model-based methods. In the design evaluation, studies with parallel designs were considered and shown to generally be inferior to sequential/cross-over designs. However, in the case of low inter-individual variability and no informative metabolite data, a prolonged parallel design could be favored. Model-based analysis for DDI assessments is preferable over NCA for victim drugs with a long half-life and should always be used when incomplete concentration-time profiles are part of the analysis.

Patient age does not affect mefloquine concentrations in erythrocytes and plasma during the acute phase of falciparum malaria

Objective

To evaluate whether patient age has a significant impact on mefloquine concentrations in the plasma and erythrocytes over the course of treatment for uncomplicated falciparum malaria.

Methods

A total of 20 children aged between 8 and 11 years and 20 adult males aged between 22 and 41 years with uncomplicated falciparum malaria were enrolled in the study. Mefloquine was administered to patients in both age groups at a dose of 20 mg kg⁻¹. The steady-state drug concentrations were measured by reversed-phase high performance liquid chromatography.

Results

All patients had an undetectable mefloquine concentration on day 0. In adults, the plasma mefloquine concentrations ranged from 770 to 2930 ng mL⁻¹ and the erythrocyte concentrations ranged from 2000 to 6030 ng mL⁻¹. In children, plasma mefloquine concentrations ranged from 881 to 3300 ng mL⁻¹ and erythrocyte concentrations ranged from 3000 to 4920 ng mL⁻¹. There was no significant correlation between mefloquine concentrations in the plasma and erythrocytes in either adults or children.

Conclusion

In the present study, we observed no effect of patient age on the steady-state concentrations of mefloquine in the plasma and erythrocytes. We found that the mefloquine concentration in the erythrocytes was approximately 2.8-times higher than in the plasma. There were no significant correlations between mefloquine concentrations in the erythrocytes and plasma for either age group.

A Screen of FDA-Approved Drugs for Inhibitors of Zika Virus Infection

Currently there are no approved vaccines or specific therapies to prevent or treat Zika virus (ZIKV) infection. We interrogated a library of FDA-approved drugs for their ability to block infection of human HuH-7 cells by a newly isolated ZIKV strain (ZIKV MEX_I_7). More than 20 out of 774 tested compounds decreased ZIKV infection in our in vitro screening assay. Selected compounds were further validated for inhibition of ZIKV infection in human cervical, placental, and neural stem cell lines, as well as primary human amnion cells. Established anti-flaviviral drugs (e.g., bortezomib and mycophenolic acid) and others that had no previously known antiviral activity (e.g., daptomycin) were identified as inhibitors of ZIKV infection. Several drugs reduced ZIKV infection across multiple cell types. This study identifies drugs that could be tested in clinical studies of ZIKV infection and provides a resource of small molecules to study ZIKV pathogenesis.

Comparison of artesunate-mefloquine and artemether-lumefantrine fixed-dose combinations for treatment of uncomplicated Plasmodium falciparum malaria in children younger than 5 years in sub-Saharan Africa: a randomised, multicentre, phase 4 trial

BACKGROUND

WHO recommends combinations of an artemisinin derivative plus an antimalarial drug of longer half-life as treatment options for uncomplicated Plasmodium falciparum infection. In Africa, artemether-lumefantrine is the most widely used artemisinin-based combination therapy, whereas artesunate-mefloquine is used infrequently because of a perceived poor tolerance to mefloquine. WHO recommends reconsideration of the use of artesunate-mefloquine in Africa. We compared the efficacy and safety of fixed-dose artesunate-mefloquine with that of artemether-lumefantrine for treatment of children younger than 5 years with uncomplicated P falciparum malaria.

METHODS

We did this multicentre, phase 4, open-label, non-inferiority trial in Burkina Faso, Kenya, and Tanzania. Children aged 6-59 months with uncomplicated malaria were randomly assigned (1:1), via a computer-generated randomisation list, to receive 3 days' treatment with either one or two artesunate-mefloquine tablets (25 mg artesunate and 55 mg mefloquine) once a day or one or two artemether-lumefantrine tablets (20 mg artemether and 120 mg lumefantrine) twice a day. Parasitological assessments were done independently by two microscopists who were blinded to treatment allocation. The primary outcome was the PCR-corrected rate of adequate clinical and parasitological response (ACPR) at day 63 in the per-protocol population. Non-inferiority was shown if the lower limit of the 95% CI for the difference between groups was greater than -5%. Early vomiting was monitored and neuropsychiatric status assessed regularly during follow-up. This study is registered with ISRCTN, number ISRCTN17472707, and the Pan African Clinical Trials Registry, number PACTR201202000278282.

FINDINGS

945 children were enrolled and randomised, 473 to artesunate-mefloquine and 472 to artemether-lumefantrine. The per-protocol population consisted of 407 children in each group. The PCR-corrected ACPR rate at day 63 was 90·9% (370 patients) in the artesunate-mefloquine group and 89·7% (365 patients) in the artemether-lumefantrine group (treatment difference 1·23%, 95% CI -2·84% to 5·29%). At 72 h after the start of treatment, no child had detectable parasitaemia and less than 6% had fever, with a similar number in each group (21 in the artesunate-mefloquine group vs 24 in the artemether-lumefantrine group). The safety profiles of artesunate-mefloquine and artemether-lumefantrine were similar, with low rates of early vomiting (71 [15·3%] of 463 patients in the artesunate-mefloquine group vs 79 [16·8%] of 471 patients in the artemether-lumefantrine group in any of the three dosing days), few neurological adverse events (ten [2·1%] of 468 vs five [1·1%] of 465), and no detectable psychiatric adverse events.

INTERPRETATION

Artesunate-mefloquine is effective and safe, and an important treatment option, for children younger than 5 years with uncomplicated P falciparum malaria in Africa.

FUNDING

Agence Française de Développement, France; Department for International Development, UK; Dutch Ministry of Foreign Affairs, Netherlands; European and Developing Countries Clinical Trials Partnership; Fondation Arpe, Switzerland; Médecins Sans Frontières; Swiss Agency for Development and Cooperation, Switzerland.

Teratogenicity of Artemether–Clindamycin Nanostructured Lipid Carriers in Rats

Currently, artemisinin-based combination therapy is considered the best option in the treatment of malaria. However, toxicity of artemisinins limits their use in pregnancy. In the absence of sufficient toxicity data, the World Health Organization recommends that artemisinins are not to be used in the first trimester of pregnancy and can be used only in second and third trimesters, when other treatments are not available. We have recently observed that drugs loaded in nanolipid carriers are selectively taken up in Plasmodium-infected erythrocytes with a concomitant reduction in the dose required to cure animals. Thus, 20% of the therapeutic dose of artemether–clindamycin (ARM-CP) loaded in nanostructured lipid carriers (NLCs; mean particle size 55 ± 10 nm) resulted in complete parasite clearance and 100% survival of infected mice. Here, we investigate the teratogenicity of this formulation in rodents (dosing on alternate days from 6th day to 18th day of gestation; 12-15 animals/group). The teratogenicity of drug-free NLCs and artesunate–clindamycin (ARS-CP) solution was also evaluated. We found that the therapeutic dose of ARS-CP caused fetal resorptions (87.5% resorptions in 8 litters), suggesting its unsuitability for use in pregnancy. Artesunate–clindamycin NLCs at therapeutic doses also resulted in ∼90% fetal resorptions in 10 litters examined. However, postimplantation losses or fetal malformations were not observed at the dose of ARM-CP NLCs that was required for complete parasite clearance in preclinical trials (ie, 20% of the therapeutic dose). Our data suggest that the NLCs loaded with 20% of the therapeutic dose of ARM-CP may have potential in treating malaria during pregnancy.

Malaria Prevention, Mefloquine Neurotoxicity, Neuropsychiatric Illness, and Risk-Benefit Analysis in the Australian Defence Force

The Australian Defence Force (ADF) has used mefloquine for malaria chemoprophylaxis since 1990. Mefloquine has been found to be a plausible cause of a chronic central nervous system toxicity syndrome and a confounding factor in the diagnosis of existing neuropsychiatric illnesses prevalent in the ADF such as posttraumatic stress disorder and traumatic brain injury. Overall health risks appear to have been mitigated by restricting the drug's use; however serious risks were realised when significant numbers of ADF personnel were subjected to clinical trials involving the drug. The full extent of the exposure, health impacts for affected individuals, and consequences for ADF health management including mental health are not yet known, but mefloquine may have caused or aggravated neuropsychiatric illness in large numbers of patients who were subsequently misdiagnosed and mistreated or otherwise failed to receive proper care. Findings in relation to chronic mefloquine neurotoxicity were foreseeable, but this eventuality appears not to have been considered during risk-benefit analyses. Thorough analysis by the ADF would have identified this long-term risk as well as other qualitative risk factors. Historical exposure of ADF personnel to mefloquine neurotoxicity now also necessitates ongoing risk monitoring and management in the overall context of broader health policies.

Mefloquine in the nucleus accumbens promotes social avoidance and anxiety-like behavior in mice

Mefloquine continues to be a key drug used for malaria chemoprophylaxis and treatment, despite reports of adverse events like depression and anxiety. It is unknown how mefloquine acts within the central nervous system to cause depression and anxiety or why some individuals are more vulnerable. We show that intraperitoneal injection of mefloquine in mice, when coupled to subthreshold social defeat stress, is sufficient to produce depression-like social avoidance behavior. Direct infusion of mefloquine into the nucleus accumbens (NAc), a key brain reward region, increased stress-induced social avoidance and anxiety behavior. In contrast, infusion into the ventral hippocampus had no effect. Whole cell recordings from NAc medium spiny neurons indicated that mefloquine application increases the frequency of spontaneous excitatory postsynaptic currents, a synaptic adaptation that we have previously shown to be associated with increased susceptibility to social defeat stress. Together, these data demonstrate a role for the NAc in mefloquine-induced depression and anxiety-like behaviors.

Complex Membrane Channel Blockade: A Unifying Hypothesis for the Prodromal and Acute Neuropsychiatric Sequelae Resulting from Exposure to the Antimalarial Drug Mefloquine

The alkaloid toxin quinine and its derivative compounds have been used for many centuries as effective medications for the prevention and treatment of malaria. More recently, synthetic derivatives, such as the quinoline derivative mefloquine (bis(trifluoromethyl)-(2-piperidyl)-4-quinolinemethanol), have been widely used to combat disease caused by chloroquine-resistant strains of the malaria parasite, Plasmodium falciparum. However, the parent compound quinine, as well as its more recent counterparts, suffers from an incidence of adverse neuropsychiatric side effects ranging from mild mood disturbances and anxiety to hallucinations, seizures, and psychosis. This review considers how the pharmacology, cellular neurobiology, and membrane channel kinetics of mefloquine could lead to the significant and sometimes life-threatening neurotoxicity associated with mefloquine exposure. A key role for mefloquine blockade of ATP-sensitive potassium channels and connexins in the substantia nigra is considered as a unifying hypothesis for the pathogenesis of severe neuropsychiatric events after mefloquine exposure in humans.

Discovery of Quinoline-Derived Trifluoromethyl Alcohols, Determination of Their in vivo Toxicity and Anticancer Activity in a Zebrafish Embryo Model

In this study the rational design, synthesis, and anticancer activity of quinoline-derived trifluoromethyl alcohols were evaluated. Members of this novel class of trifluoromethyl alcohols were identified as potent growth inhibitors in a zebrafish embryo model. Synthesis of these compounds was carried out with an sp(3) -C-H functionalization strategy of methyl quinolines with trifluoromethyl ketones. A zebrafish embryo model was also used to explore the toxicity of ethyl 4,4,4-trifluoro-3-hydroxy-3-(quinolin-2-ylmethyl)butanoate (1), 2-benzyl-1,1,1-trifluoro-3-(quinolin-2-yl)propan-2-ol (2), and trifluoro-3-(isoquinolin-1-yl)-2-(thiophen-2-yl)propan-2-ol (3). Compounds 2 and 3 were found to be more toxic than compound 1; apoptotic staining assays indicated that compound 3 causes increased cell death. In vitro cell proliferation assays showed that compound 2, with an LC50 value of 14.14 μm, has more potent anticancer activity than cisplatin. This novel class of inhibitors provides a new direction in the discovery of effective anticancer agents.

Artemisinin-naphthoquine for treating uncomplicated Plasmodium falciparum malaria

BACKGROUND

The World Health Organization (WHO) recommends artemisinin-based combination therapy (ACT) for treating people with Plasmodium falciparum malaria. Five combinations are currently recommended, all administered over three days. Artemisinin-naphthoquine is a new combination developed in China, which is being marketed as a one-day treatment. Although shorter treatment courses may improve adherence, the WHO recommends at least three days of the short-acting artemisinin component to eliminate 90% P. falciparum parasites in the bloodstream, before leaving the longer-acting partner drug to clear the remaining parasites.

OBJECTIVES

To evaluate the efficacy and safety of the artemisinin-naphthoquine combination for treating adults and children with uncomplicated P. falciparum malaria.

SEARCH METHODS

We searched the Cochrane Infectious Diseases Group Specialized Register; Cochrane Central Register of Controlled Trials (CENTRAL) published in The Cochrane Library; MEDLINE; EMBASE; and LILACS up to January 2015. We also searched the metaRegister of Controlled Trials (mRCT) using 'malaria' and 'arte* OR dihydroarte*' as search terms.

SELECTION CRITERIA

Randomized controlled trials comparing artemisinin-naphthoquine combinations with established WHO-recommended ACTs for the treatment of adults and children with uncomplicated malaria due to P. falciparum.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trials for eligibility and risk of bias, and extracted data. We analysed primary outcomes in line with the WHO 'Protocol for assessing and monitoring antimalarial drug efficacy' and compared drugs using risk ratios (RR) and 95% confidence intervals (CI). Secondary outcomes were effects on gametocytes, haemoglobin, and adverse events. We assessed the quality of evidence using the GRADE approach.

MAIN RESULTS

Four trials, enrolling 740 adults and children, met the inclusion criteria. Artemisinin-naphthoquine was administered as a single dose (two trials), as two doses given eight hours apart (one trial), and once daily for three days (one trial), and compared to three-day regimens of established ACTs. Three additional small pharmaceutical company trials have been carried out. We have requested the data but have not received a response from the company. Artemisinin-naphthoquine versus artemether-lumefantrineIn three small trials from Benin, Côte d'Ivoire, and Papua New Guinea, both combinations had a very low incidence of treatment failure at Day 28, and there were no differences demonstrated in PCR-unadjusted, or PCR-adjusted treatment failure (three trials, 487 participants, low quality evidence). Only the single study from Papua New Guinea followed participants up to Day 42, and the number of treatment failures remained very low with both combinations (one trial, 186 participants, very low quality evidence). Artemisinin-naphthoquine versus dihydroartemisinin-piperaquineIn a single small trial from Indonesia, treatment failure at Day 28 and Day 42 was very low in both groups with no differences demonstrated (one trial, 144 participants, very low quality evidence).

AUTHORS' CONCLUSIONS

The results of these few trials of artemisinin-naphthoquine are promising, but further trials from multiple settings are required to reliably demonstrate the relative efficacy and safety compared to established ACTs. Future trials should be adequately powered to demonstrate non-inferiority, and regimens incorporating three days of the artemisinin component are probably preferable to the one-day regimens.

Acute and long-term psychiatric side effects of mefloquine: a follow-up on Danish adverse event reports

BACKGROUND

The aim of the study was to explore the profile of acute and long-term psychiatric side effects associated with mefloquine.

METHODS

Subjects (n = 73) reported to a Danish national register during five consecutive years for mefloquine associated side effects were included. Acute psychiatric side effects were retrospectively assessed using the SCL-90-R and questions based on Present State Examination (PSE). Subjects reporting suspected psychotic states were contacted for a personal PSE interview. Electronic records of psychiatric hospitalizations and diagnoses were cross-checked. Long-term effects were evaluated with SF-36. SCL-90-R and SF-36 data were compared to age- and gender matched controls.

RESULTS

In the SCL-90-R, clinically significant scores for anxiety, phobic anxiety and depression were found in 55%, 51%, and 44% of the mefloquine group. Substantial acute phase psychotic symptoms were found in 15% and were time-limited. Illusions/hallucinations were more frequently observed among women. Cases of hypomania/mania in the acute phase were 5.5%. Significant long-term mental health effects were demonstrated for the SF-36 subscales mental health (MH), role emotional (RE), and vitality (VT) in the mefloquine group compared to matched controls.

CONCLUSION

The most frequent acute psychiatric problems were anxiety, depression, and psychotic symptoms. Data indicated that subjects experiencing acute mefloquine adverse side effects may develop long-term mental health problems with a decreased sense of global quality of life with lack of energy, nervousness, and depression.

Failure of malaria chemoprophylaxis with mefloquine in an oversize traveller to Mozambique

A case of failure of mefloquine prophylaxis in an oversize traveller, who correctly took the drug. This case seems to be attributed to mefloquine resistance, however it is suggested that mefloquine dosage should be modulated by body weight, as is already indicated by some authorities.

Gender-specific distribution of mefloquine in the blood following the administration of therapeutic doses

Background

The objectives of the study were to elucidate the gender-specific distribution of mefloquine in cellular and fluid blood compartments when given at therapeutic dosage, to assess its correlation with the occurrence of treatment-related adverse events, and to explore the necessity of adjusting treatment guidelines for females.

Methods

The distribution of mefloquine following the administration of standard therapeutic doses (1,250 mg mefloquine in split dose) to 22 healthy Caucasian volunteers was assessed in whole blood, serum, plasma, red blood cells (RBCs), white blood cells, and platelets using high performance liquid chromatography.

Results

Plasma mefloquine concentrations after 14 hours were considerably higher in female subjects than in males (2,778 vs 1,017 ng/ml at H14), concordant with a significantly higher frequency, duration, and severity of adverse reactions. However, mean drug concentrations of RBC appeared slightly higher in male volunteers (857 vs 719 ng/ml). At H48, a similar situation prevailed, and at H168 the mefloquine concentrations in plasma continued to be higher in females compared to males (1,353 vs 666 ng/ml), while the concentrations of RBC were similar in females (389 vs 375 ng/ml). Since the observations relate to healthy individuals, they do not take into account selective uptake of mefloquine by Plasmodium-infected erythrocytes as in the case of therapeutic drug use.

Conclusion

Although plasma mefloquine concentrations in female healthy volunteers are considerably higher and the concentrations of the RBCs are initially lower compared to males, they do not seem to justify an adjustment of treatment guidelines for mefloquine in female Caucasian individuals.

Investigation of the in vitro gender-specific partitioning of mefloquine in malarial infected red blood cells and plasma

The investigation of gender-specific partitioning of the antimalarial drug mefloquine to cellular and fluid blood compartments was performed using blood collected from a female and male healthy subject that were infected with Plasmodium falciparum PCM2 clone and spiked with mefloquine (0.25, 1, and 5 μM). Mefloquine concentrations in red cells of both female and male subjects were significantly higher than plasma, which suggests an intensive uptake by red cells. This was supported by a high ratio of mefloquine concentrations in the parasitized and non-parasitized red cells of about 4-fold. Gender-specific partitioning of mefloquine in parasitized blood was seen only in plasma where significantly higher concentrations were observed in female compared with male plasma. Down-adjusting the therapeutic dose of mefloquine in female patients with malaria is not advisable because mefloquine concentrations in the target cellular compartment are similar in both genders.

Absolute Configuration and Antimalarial Activity of erythro-Mefloquine Enantiomers

Mefloquine (MQ), an antimalarial drug, is used as a racemate of (-)- and (+)-enantiomers, which display biological differences. The question concerning their exact configuration remains a matter of debate. The absolute configuration of the two MQ enantiomers as well as their biological activity has been established, thus confirming the importance of the stereochemistry in the design of MQ analogues that have fewer adverse side effects.

The anti-malarial drug Mefloquine disrupts central autonomic and respiratory control in the working heart brainstem preparation of the rat

Background

Mefloquine is an anti-malarial drug that can have neurological side effects. This study examines how mefloquine (MF) influences central nervous control of autonomic and respiratory systems using the arterially perfused working heart brainstem preparation (WHBP) of the rat. Recordings of nerve activity were made from the thoracic sympathetic chain and phrenic nerve, while heart rate (HR) and perfusion pressure were also monitored in the arterially perfused, decerebrate, rat WHBP. MF was added to the perfusate at 1 μM to examine its effects on baseline parameters as well as baroreceptor and chemoreceptor reflexes.

Results

MF caused a significant, atropine resistant, bradycardia and increased phrenic nerve discharge frequency. Chemoreceptor mediated sympathoexcitation (elicited by addition of 0.1 ml of 0.03% sodium cyanide to the aortic cannula) was significantly attenuated by the application of MF to the perfusate. Furthermore MF significantly decreased rate of return to resting HR following chemoreceptor induced bradycardia. An increase in respiratory frequency and attenuated respiratory-related sympathetic nerve discharge during chemoreceptor stimulation was also elicited with MF compared to control. However, MF did not significantly alter baroreceptor reflex sensitivity.

Conclusions

These studies indicate that in the WHBP, MF causes profound alterations in autonomic and respiratory control. The possibility that these effects may be mediated through actions on connexin 36 containing gap junctions in central neurones controlling sympathetic nervous outflow is discussed.

Differences in anti-malarial activity of 4-aminoalcohol quinoline enantiomers and investigation of the presumed underlying mechanism of action

Background

A better anti-malarial efficiency and lower neurotoxicity have been reported for mefloquine (MQ) (+)- enantiomer. However, the importance of stereoselectivity remains poorly understood as the anti-malarial activity of pure enantiomer MQ analogues has never been described. Building on these observations, a series of enantiopure 4-aminoalcohol quinoline derivatives has previously been synthesized to optimize the efficiency and reduce possible adverse effects. Their in vitro activity on Plasmodium falciparum W2 and 3D7 strains is reported here along with their inhibition of β-haematin formation and peroxidative degradation of haemin, two possible mechanisms of action of anti-malarial drugs.

Results

The (S)-enantiomers of this series of 4-aminoalcohol quinoline derivatives were found to be at least as effective as both chloroquine (CQ) and MQ. The derivative with a 5-carbon side-chain length was the more efficient on both P. falciparum strains. (R )-enantiomers displayed an activity decreased by 2 to 15-fold as compared to their (S) counterparts. The inhibition of β-haematin formation was significantly stronger with all tested compounds than with MQ, irrespective of the stereochemistry. Similarly, the inhibition of haemin peroxidation was significantly higher for both (S) and (R)-enantiomers of derivatives with a side-chain length of five or six carbons than for MQ and CQ.

Conclusions

The prominence of stereochemistry in the anti-malarial activity of 4-aminoalcohol quinoline derivatives is confirmed. The inhibition of β-haematin formation and haemin peroxidation can be put forward as presumed mechanisms of action but do not account for the stereoselectivity of action witnessed in vitro.

Mefloquine for uncomplicated Plasmodium falciparum malaria in children

BACKGROUND

Children with uncomplicated Plasmodium falciparum imported malaria are treated with various antimalarial regimens including mefloquine depending on national guidelines. Little is known regarding mefloquine treatment efficacy in this setting.

METHODS

In this prospective study, children 3 months to 16 years of age admitted in a tertiary hospital emergency ward in France with uncomplicated P. falciparum malaria were treated with oral mefloquine. Each dose was given with an antiemetic.

RESULTS

Between 2004 and 2009, 95 children were evaluated. In all, 94% had traveled in the Indian Ocean region (Comoros and Madagascar); 79% used a malaria chemoprophylaxis, but none was fully compliant with World Health Organization recommended regimens. Main clinical features at admission were fever (91%), vomiting (44%), and headaches (44%). Hemoglobin < 80 g/L and platelets <100 G/L were observed in 16% and 17%, respectively. All children were initially cured by mefloquine, and no relapse was noted within 45 days after admission. One Plasmodium vivax relapse occurred 6 months later. Vomiting within 1 hour after dosing occurred in 20% of children. Significant features associated with early vomiting by univariate analysis were a weight ≤ 15 kg, C-reactive protein ≥ 50 mg/L, and parasitemia ≥ 1%, but only low weight was significant by multivariate analysis.

CONCLUSION

Mefloquine is an effective treatment for uncomplicated imported P. falciparum malaria in children returning from countries with low mefloquine resistance. Early vomiting after mefloquine dosing is frequent, especially in children < 15 kg of weight, but a second dose can be given successfully.

The pharmacogenetics of antimalaria artemisinin combination therapy

INTRODUCTION

Plasmodium falciparum malaria is one of the world's most lethal infectious diseases, commanding millions of drug administrations per year. The pharmacogenetics of these drugs is poorly known, although its application can be pivotal for the optimized management of this disease.

AREAS COVERED

The main components of artemisinin combination therapy (ACT), the worldwide main antimalarial strategy, are metabolized by the polymorphic CYP3A4 (mefloquine, artemether, lumefantrine), CYP2C8 (amodiaquine), CYP2A6 (artesunate) and CYP1A1/2 (amodiaquine/desethylamodiaquine), with dihydroartemisinin being acted by Phase II UDP-glucuronosyltransferases. The worldwide adoption of ACT is leading to a large number of antimalarial treatments. Simultaneously, the feared development of parasite drug resistance might drive dosing increases. In these scenarios of increased drug exposure, pharmacogenetics can be a key tool supporting evidence-based medicine aiming for the longest possible useful lifespan of this important chemotherapy.

EXPERT OPINION

Translation in this moment is not operationally possible at an individual level, but large population studies are achievable for: i) the development of robust pharmacogenetics markers; and ii) the parallel development of a pharmacogenetic cartography of malaria settings. Advances in the understanding of antimalarial pharmacogenetics are urgent in order to protect the exposed populations, enhance the effectiveness of ACT and, consequently, contributing for the long aimed elimination of the disease.

From innovation to application: social-ecological context, diagnostics, drugs and integrated control of schistosomiasis

Compared to malaria, tuberculosis and HIV/AIDS, schistosomiasis remains a truly neglected tropical disease. Schistosomiasis, perhaps more than any other disease, is entrenched in prevailing social-ecological systems, since transmission is governed by human behaviour (e.g. open defecation and patterns of unprotected surface water contacts) and ecological features (e.g. living in close proximity to suitable freshwater bodies in which intermediate host snails proliferate). Moreover, schistosomiasis is intimately linked with poverty and the disease has spread to previously non-endemic areas as a result of demographic, ecological and engineering transformations. Importantly though, thanks to increased advocacy there is growing awareness, financial and technical support to control and eventually eliminate schistosomiasis as a public health problem at local, regional and global scales. The purpose of this review is to highlight recent progress made in innovation, validation and application of new tools and strategies for research and integrated control of schistosomiasis. First, we explain that schistosomiasis is deeply embedded in social-ecological systems and explore linkages with poverty. We then summarize and challenge global statistics, risk maps and burden estimates of human schistosomiasis. Discovery and development research pertaining to novel diagnostics and drugs forms the centrepiece of our review. We discuss unresolved issues and emerging opportunities for integrated and sustainable control of schistosomiasis and conclude with a series of research needs.

Azithromycin plus chloroquine: combination therapy for protection against malaria and sexually transmitted infections in pregnancy

Introduction:

The first-line therapy for the intermittent preventive treatment of malaria in pregnancy (IPTp) is sulphadoxine-pyrimethamine (SP). There is an urgent need to identify safe, well-tolerated and efficacious alternatives to SP due to widespread Plasmodium falciparum resistance. Combination therapy using azithromycin and chloroquine is one possibility that has demonstrated adequate parasitological response > 95% in clinical trials of non-pregnant adults in sub-Saharan Africa and where IPTp is a government policy in 33 countries.

Areas covered:

Key safety, tolerability and efficacy data are presented for azithromycin and chloroquine, alone and/or in combination, when used to prevent and/or treat P. falciparum, P. vivax, and several curable sexually transmitted and reproductive tract infections (STI/RTI). Pharmacokinetic evidence from pregnant women is also summarized for both compounds.

Expert opinion:

The azithromycin-chloroquine regimen that has demonstrated consistent efficacy in non-pregnant adults has been a 3-day course containing daily doses of 1 g of azithromycin and 600 mg base of chloroquine. The pharmacokinetic evidence of these compounds individually suggests that dose adjustments may not be necessary when used in combination for treatment efficacy against P. falciparum, P. vivax, as well as several curable STI/ RTI among pregnant women, although clinical confirmation will be necessary. Mass trachoma-treatment campaigns have shown that azithromycin selects for macrolide resistance in the pneumococcus, which reverses following the completion of therapy. Most importantly, no evidence to date suggests that azithromycin induces pneumococcal resistance to penicillin.