Clindamycin as an antimalarial drug: review of clinical trials

Novel hydrazone compounds with broad-spectrum antiplasmodial activity and synergistic interactions with antimalarial drugs

The development of novel antiplasmodial compounds with broad-spectrum activity against different stages of Plasmodium parasites is crucial to prevent malaria disease and parasite transmission. This study evaluated the antiplasmodial activity of seven novel hydrazone compounds (referred to as CB compounds: CB-27, CB-41, CB-50, CB-53, CB-58, CB-59, and CB-61) against multiple stages of Plasmodium parasites. All CB compounds inhibited blood stage proliferation of drug-resistant or sensitive strains of Plasmodium falciparum in the low micromolar to nanomolar range. Interestingly, CB-41 exhibited prophylactic activity against hypnozoites and liver schizonts in Plasmodium cynomolgi, a primate model for Plasmodium vivax. Four CB compounds (CB-27, CB-41, CB-53, and CB-61) inhibited P. falciparum oocyst formation in mosquitoes, and five CB compounds (CB-27, CB-41, CB-53, CB-58, and CB-61) hindered the in vitro development of Plasmodium berghei ookinetes. The CB compounds did not inhibit the activation of P. berghei female and male gametocytes in vitro. Isobologram assays demonstrated synergistic interactions between CB-61 and the FDA-approved antimalarial drugs, clindamycin and halofantrine. Testing of six CB compounds showed no inhibition of Plasmodium glutathione S-transferase as a putative target and no cytotoxicity in HepG2 liver cells. CB compounds are promising candidates for further development as antimalarial drugs against multidrug-resistant parasites, which could also prevent malaria transmission.

Lincosamide Antibiotics: Structure, Activity, and Biosynthesis

Lincosamides are naturally occurring antibiotics isolated from Streptomyces sp. Currently, lincomycin A and its semisynthetic analogue clindamycin are used as clinical drugs. Due to their unique structures and remarkable biological activities, derivatizations of lincosamides via semi-synthesis and biosynthetic studies have been reported. This review summarizes the structures and biological activities of lincosamides, and the recent studies of lincosamide biosynthetic enzymes.

Antimalarial Drug Resistance: A Brief History of Its Spread in Indonesia

Malaria remains to be a national and global challenge and priority, as stated in the strategic plan of the Indonesian Ministry of Health and Sustainable Development Goals. In Indonesia, it is targeted that malaria elimination can be achieved by 2030. Unfortunately, the development and spread of antimalarial resistance inflicts a significant risk to the national malaria control programs which can lead to increased malaria morbidity and mortality. In Indonesia, resistance to widely used antimalarial drugs has been reported in two human species, Plasmodium falciparum and Plasmodium vivax. With the exception of artemisinin, resistance has surfaced towards all classes of antimalarial drugs. Initially, chloroquine, sulfadoxine-pyrimethamine, and primaquine were the most widely used antimalarial drugs. Regrettably, improper use has supported the robust spread of their resistance. Chloroquine resistance was first reported in 1974, while sulfadoxine-pyrimethamine emerged in 1979. Twenty years later, most provinces had declared treatment failures of both drugs. Molecular epidemiology suggested that variations in pfmdr1 and pfcrt genes were associated with chloroquine resistance, while dhfr and dhps genes were correlated with sulfadoxine-pyrimethamine resistance. Additionally, G453W, V454C and E455K of pfk13 genes appeared to be early warning sign to artemisinin resistance. Here, we reported mechanisms of antimalarial drugs and their development of resistance. This insight could provide awareness toward designing future treatment guidelines and control programs in Indonesia.

Carbohydrate derivatives fight against malaria parasite as anti-plasmodial agents

Malaria, a prevalent fatal disease around the world is caused by Plasmodium sp. and is transmitted by the bite of female Anopheles mosquito. It is leading cause of death in this century among most infectious diseases. Drug resistance was reported for almost every front-line drug against the deadliest species of the malarial parasite, i.e., Plasmodium falciparum. In the evolutionary arms race between parasite and existing arsenals of drugs new molecules having novel mechanism of action is urgently needed to overcome the drug resistance. In this review, we have discussed the importance of carbohydrate derivatives of different class of compounds as possible antimalarials with emphasis on mode of action, rational design, and SAR with improved efficacy. Carbohydrate-protein interactions are increasingly important for medicinal chemists and chemical biologists to understand the pathogenicity of the parasite. Less is known about the carbohydrate-protein interactions and pathogenicity in the Plasmodium parasite. With the increased knowledge on protein-sugar interaction and glycomics of Plasmodium parasites, carbohydrate derivatives can surpass the existing biochemical pathways responsible for drug resistance. The new candidates with novel mode of action will prove to be a potent antimalarial drug candidate without any parasitic resistance.

Squaramide Tethered Clindamycin, Chloroquine, and Mortiamide Hybrids: Design, Synthesis, and Antimalarial Activity

Malaria remains one of the major health problems in the world. In this work, a series of squaramide tethered chloroquine, clindamycin, and mortiamide D hybrids have been synthesized to assess their in vitro antiplasmodial activity against 3D7 (chloroquine-sensitive) and Dd2 strains of Plasmodium falciparum. The most active compound, a simple chloroquine analogue, displayed low nanomolar IC50 value against both strains (3 nM for 3D7 strain and 18 nM for Dd2 strain). Moreover, all molecular hybrids incorporating the hydroxychloroquine scaffold showed the most potent activities, exemplified with a chloroquine dimer, IC50 = 31 nM and 81 nM against 3D7 and Dd2 strains, respectively. These results highlight the first time use of clindamycin and mortiamide D as antimalarial molecular hybrids and establish these valuable hits for future optimization.

A High-Throughput Amenable Dual Luciferase System for Measuring Toxoplasma gondii Bradyzoite Viability after Drug Treatment

It is estimated that more than 2 billion people are chronically infected with the intracellular protozoan parasite Toxoplasma gondii (T. gondii). Despite this, there is currently no vaccine to prevent infection in humans, and there is no recognized curative treatment to clear tissue cysts. A major hurdle for identifying effective drug candidates against chronic-stage cysts has been the low throughput of existing in vitro assays for testing the survival of bradyzoites. We have developed a luciferase-based platform for specifically determining bradyzoite survival within in vitro cysts in a 96-well plate format. We engineered a cystogenic type II T. gondii PruΔku80Δhxgpr strain for stage-specific expression of firefly luciferase in the cytosol of bradyzoites and nanoluciferase for secretion into the lumen of the cyst (DuaLuc strain). Using this DuaLuc strain, we found that the ratio of firefly luciferase to nanoluciferase decreased upon treatment with atovaquone or LHVS, two compounds that are known to compromise bradyzoite viability. The 96-well format allowed us to test several additional compounds and generate dose-response curves for calculation of EC50 values indicating relative effectiveness of a compound. Accordingly, this DuaLuc system should be suitable for screening libraries of diverse compounds and defining the potency of hits or other compounds with a putative antibradyzoite activity.

Efficacy of 3-day low dose quinine plus clindamycin versus artemether-lumefantrine for the treatment of uncomplicated Plasmodium falciparum malaria in Kenyan children (CLINDAQUINE): an open-label randomized trial

Background

The World Health Organization recommends quinine plus clindamycin as first-line treatment of malaria in the first trimester of pregnancy and as a second-line treatment for uncomplicated falciparum malaria when artemisinin-based drug combinations are not available. The efficacy of quinine plus clindamycin was compared with that of artemether-lumefantrine in the treatment of uncomplicated Plasmodium falciparum malaria in children below 5 years of age.

Methods

An open-label, phase 3, randomized trial was conducted in western Kenya. Children aged 6–59 months with uncomplicated falciparum malaria were randomly assigned (1:1) via a computer-generated randomization list to receive 3 days of twice a day treatment with either oral quinine (20 mg/kg/day) plus clindamycin (20 mg/kg/day) or artemether-lumefantrine (artemether 20 mg, lumefantrine 120 mg) as one (for those weighing 5–14 kg) or two (for those weighing 15–24 kg) tablets per dose. The primary outcome was a PCR-corrected rate of adequate clinical and parasitological response (ACPR) on day 28 in the per-protocol population.

Results

Of the 384 children enrolled, 182/192 (94.8%) receiving quinine plus clindamycin and 171/192 (89.1%) receiving artemether-lumefantrine completed the study. The PCR-corrected ACPR rate was 44.0% (80 children) in the quinine plus clindamycin group and 97.1% (166 children) in the artemether-lumefantrine group (treatment difference − 53.1%, 95% CI − 43.5% to − 62.7%). At 72 h after starting treatment, 50.3% (94 children) in the quinine plus clindamycin group were still parasitaemic compared with 0.5% (1 child) in the artemether-lumefantrine group. Three cases of severe malaria were recorded as serious adverse events in the quinine plus clindamycin group.

Conclusions

The study found no evidence to support the use of a 3-day low dose course of quinine plus clindamycin in the treatment of uncomplicated falciparum malaria in children under 5 years of age in Kenya, where artemether-lumefantrine is still effective.

Trial Registration: This trial is registered with the Pan-African Clinical Trials Registry, PACTR20129000419241.

Antimalarial Natural Products

Natural products have made a crucial and unique contribution to human health, and this is especially true in the case of malaria, where the natural products quinine and artemisinin and their derivatives and analogues, have saved millions of lives. The need for new drugs to treat malaria is still urgent, since the most dangerous malaria parasite, Plasmodium falciparum, has become resistant to quinine and most of its derivatives and is becoming resistant to artemisinin and its derivatives. This volume begins with a short history of malaria and follows this with a summary of its biology. It then traces the fascinating history of the discovery of quinine for malaria treatment and then describes quinine's biosynthesis, its mechanism of action, and its clinical use, concluding with a discussion of synthetic antimalarial agents based on quinine's structure. The volume then covers the discovery of artemisinin and its development as the source of the most effective current antimalarial drug, including summaries of its synthesis and biosynthesis, its mechanism of action, and its clinical use and resistance. A short discussion of other clinically used antimalarial natural products leads to a detailed treatment of other natural products with significant antiplasmodial activity, classified by compound type. Although the search for new antimalarial natural products from Nature's combinatorial library is challenging, it is very likely to yield new antimalarial drugs. The chapter thus ends by identifying over ten natural products with development potential as clinical antimalarial agents.

Antiprotozoal agents: How have they changed over a decade?

Neglected tropical diseases are a diverse group of communicable diseases that are endemic in low- or low-to-middle-income countries located in tropical and subtropical zones. The number and availability of drugs for treating these diseases are low, the administration route is inconvenient in some cases, and most of them have safety, efficacy, or adverse/toxic reaction issues. The need for developing new drugs to deal with these issues is clear, but one of the most drastic consequences of this negligence is the lack of interest in the research and development of new therapeutic options among major pharmaceutical companies. Positive changes have been achieved over the last few years, although the overall situation remains alarming. After more than one decade since the original work reviewing antiprotozoal agents came to light, now it is time to question ourselves: How has the scenario for the treatment of protozoal diseases such as malaria, leishmaniasis, human African trypanosomiasis, and American trypanosomiasis changed? This review covers the last decade in terms of the drugs currently available for the treatment of these diseases as well as the clinical candidates being currently investigated.

Treatment of Human Babesiosis: Then and Now

Babesiosis is an emerging tick-borne disease caused by apicomplexan parasites of the genus Babesia. With its increasing incidence worldwide and the risk of human-to-human transmission through blood transfusion, babesiosis is becoming a rising public health concern. The current arsenal for the treatment of human babesiosis is limited and consists of combinations of atovaquone and azithromycin or clindamycin and quinine. These combination therapies were not designed based on biological criteria unique to Babesia parasites, but were rather repurposed based on their well-established efficacy against other apicomplexan parasites. However, these compounds are associated with mild or severe adverse events and a rapid emergence of drug resistance, thus highlighting the need for new therapeutic strategies that are specifically tailored to Babesia parasites. Herein, we review ongoing babesiosis therapeutic and management strategies and their limitations, and further review current efforts to develop new, effective, and safer therapies for the treatment of this disease.

Pharmacotherapy for artemisinin-resistant malaria

INTRODUCTION

Malaria, the most devastating parasitic disease, is currently treated with artemisinin-based combination therapies (ACTs). Unfortunately, some ACTs are unable to rapidly clear Plasmodium falciparum parasites from the blood stream and are failing to cure malaria patients; a problem, so far, largely confined to Southeast Asia. There is a fear of resistant Plasmodium falciparum emerging in other parts of the world including Sub-Saharan Africa. Strategies for alternative treatments, ideally non-artemisinin based, are needed.

AREAS COVERED

This narrative review gives an overview of approved antimalarials and of some compounds in advanced drug development that could be used when an ACT is failing. The selection was based on a literature search in PubMed and WHO notes for malaria treatment.

EXPERT OPINION

The ACT drug class can still cure malaria in malaria endemic regions. However, the appropriate ACT drug should be chosen considering the background resistance of the partner drug of the local parasite population. Artesunate-pyronaridine, the 'newest' recommended ACT, and atovaquone-proguanil are, so far, effective, and safe treatments for uncomplicated falciparum malaria. Therefore, all available ACTs should be safeguarded from parasite resistance and the development of new antimalarial drug classes needs to be accelerated.

Reevaluation of the Toxoplasma gondii and Neospora caninum genomes reveals misassembly, karyotype differences, and chromosomal rearrangements

Neosporacaninum primarily infects cattle, causing abortions, with an estimated impact of a billion dollars on the worldwide economy annually. However, the study of its biology has been unheeded by the established paradigm that it is virtually identical to its close relative, the widely studied human pathogen Toxoplasma gondii. By revisiting the genome sequence, assembly, and annotation using third-generation sequencing technologies, here we show that the N. caninum genome was originally incorrectly assembled under the presumption of synteny with T. gondii. We show that major chromosomal rearrangements have occurred between these species. Importantly, we show that chromosomes originally named Chr VIIb and VIII are indeed fused, reducing the karyotype of both N. caninum and T. gondii to 13 chromosomes. We reannotate the N. caninum genome, revealing more than 500 new genes. We sequence and annotate the nonphotosynthetic plastid and mitochondrial genomes and show that although apicoplast genomes are virtually identical, high levels of gene fragmentation and reshuffling exist between species and strains. Our results correct assembly artifacts that are currently widely distributed in the genome database of N. caninum and T. gondii and, more importantly, highlight the mitochondria as a previously oversighted source of variability and pave the way for a change in the paradigm of synteny, encouraging rethinking the genome as basis of the comparative unique biology of these pathogens.

Drug Repurposing: A Review of Old and New Antibiotics for the Treatment of Malaria: Identifying Antibiotics with a Fast Onset of Antiplasmodial Action

Malaria is one of the most life-threatening infectious diseases and constitutes a major health problem, especially in Africa. Although artemisinin combination therapies remain efficacious to treat malaria, the emergence of resistant parasites emphasizes the urgent need of new alternative chemotherapies. One strategy is the repurposing of existing drugs. Herein, we reviewed the antimalarial effects of marketed antibiotics, and described in detail the fast-acting antibiotics that showed activity in nanomolar concentrations. Antibiotics have been used for prophylaxis and treatment of malaria for many years and are of particular interest because they might exert a different mode of action than current antimalarials, and can be used simultaneously to treat concomitant bacterial infections.

Bacterial natural products in the fight against mosquito-transmitted tropical diseases

Covering: up to 2019 Secondary metabolites of microbial origin have long been acknowledged as medically relevant, but their full potential remains largely unexploited. Of the countless natural compounds discovered thus far, only 5-10% have been isolated from microorganisms. At the same time, while whole-genome sequencing has demonstrated that bacteria and fungi often encode natural products, only a few genera have yet been mined for new compounds. This review explores the contributions of bacterial natural products to combatting infection by malaria parasites, filarial worms, and arboviruses such as dengue, Zika, Chikungunya, and West Nile. It highlights how molecules isolated from microorganisms ranging from marine cyanobacteria to mosquito endosymbionts can be exploited as antimicrobials and antivirals. Pursuit of this mostly untapped source of chemical entities will potentially result in new interventions against these tropical diseases, which are urgently needed to combat the increase in the incidence of resistance.

In vitro activity of eravacycline, a novel synthetic halogenated tetracycline, against the malaria parasite Plasmodium falciparum

OBJECTIVES

Eravacycline is a novel synthetic halogenated tetracycline derivative with a broad antibacterial spectrum. Antibiotics, including tetracyclines, have been used for prophylaxis and, more rarely, for the treatment of malaria for several decades. The rise in drug-resistant malaria parasites renders the search for new treatment candidates urgent. We determined the in vitro potency of eravacycline against Plasmodium falciparum and investigated the apicoplast as a potential drug target.

METHODS

Four tetracyclines, including eravacycline, tetracycline, tigecycline, and doxycycline, and the lincosamide clindamycin, were tested in 3-day and 6-day in vitro susceptibility assays of P. falciparum laboratory strain 3D7 and/or of clinical isolates obtained from 33 P. falciparum infected individuals from Gabon in 2018. Assays with isopentenyl pyrophosphate substitution were performed to investigate whether apicoplast-encoded isoprenoid biosynthesis is inhibited by these antibiotics.

RESULTS

Eravacycline showed the highest activity of all tetracyclines tested in clinical isolates in the 3-day and 6-day assays. Substitution of isopentenyl pyrophosphate in vitro using the laboratory strain 3D7 reversed the activity of eravacycline and comparator antibiotics, indicating the apicoplast to be the main target organelle.

CONCLUSIONS

These results demonstrate the potential of novel antibiotics, and eravacycline, as candidate antimalarial therapies.

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

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

Enhancing the antimalarial activity of artesunate

The global challenge to the treatment of malaria is mainly the occurrence of resistance of malaria parasites to conventionally used antimalarials. Artesunate, a semisynthetic artemisinin compound, and other artemisinin derivatives are currently used in combination with selected active antimalarial drugs in order to prevent or delay the emergence of resistance to artemisinin derivatives. Several methods, such as preparation of hybrid compounds, combination therapy, chemical modification and the use of synthetic materials to enhance solubility and delivery of artesunate, have been employed over the years to improve the antimalarial activity of artesunate. Each of these methods has advantages it bestows on the efficacy of artesunate. This review discussed the various methods employed in enhancing the antimalarial activity of artesunate and delaying the emergence of resistance of parasite to it.

Antibiotic-induced microbiome perturbations are associated with significant alterations to colonic mucosal immunity in rhesus macaques

The diverse bacterial communities that colonize the gastrointestinal tract play an essential role in maintaining immune homeostasis through the production of critical metabolites such as short-chain fatty acids (SCFAs) and this can be disrupted by antibiotic use. However, few studies have addressed the effects of specific antibiotics longitudinally on the microbiome and immunity. We evaluated the effects of four specific antibiotics: enrofloxacin, cephalexin, paromomycin, and clindamycin, in healthy female rhesus macaques. All antibiotics disrupted the microbiome, including reduced abundances of fermentative bacteria and increased abundances of potentially pathogenic bacteria, including Enterobacteriaceae in the stool, and decreased Helicobacteraceae in the colon. This was associated with decreased SCFAs, indicating altered bacterial metabolism. Importantly, antibiotic use also substantially altered local immune responses, including increased neutrophils and Th17 cells in the colon. Furthermore, we observed increased soluble CD14 in plasma, indicating microbial translocation. These data provide a longitudinal evaluation of antibiotic-induced changes to the composition and function of colonic bacterial communities associated with specific alterations in mucosal and systemic immunity.

The genomic architecture of antimalarial drug resistance

Plasmodium falciparum and Plasmodium vivax, the two protozoan parasite species that cause the majority of cases of human malaria, have developed resistance to nearly all known antimalarials. The ability of malaria parasites to develop resistance is primarily due to the high numbers of parasites in the infected person's bloodstream during the asexual blood stage of infection in conjunction with the mutability of their genomes. Identifying the genetic mutations that mediate antimalarial resistance has deepened our understanding of how the parasites evade our treatments and reveals molecular markers that can be used to track the emergence of resistance in clinical samples. In this review, we examine known genetic mutations that lead to resistance to the major classes of antimalarial medications: the 4-aminoquinolines (chloroquine, amodiaquine and piperaquine), antifolate drugs, aryl amino-alcohols (quinine, lumefantrine and mefloquine), artemisinin compounds, antibiotics (clindamycin and doxycycline) and a napthoquinone (atovaquone). We discuss how the evolution of antimalarial resistance informs strategies to design the next generation of antimalarial therapies.

Kinetic Driver of Antibacterial Drugs against Plasmodium falciparum and Implications for Clinical Dosing

Antibacterial drugs are an important component of malaria therapy. We studied the interactions of clindamycin, tetracycline, chloramphenicol, and ciprofloxacin against Plasmodium falciparum under static and dynamic conditions. In microtiter plate assays (static conditions), and as expected, parasites displayed the delayed death response characteristic for apicoplast-targeting drugs. However, rescue by isopentenyl pyrophosphate was variable, ranging from 2,700-fold for clindamycin to just 1.7-fold for ciprofloxacin, suggesting that ciprofloxacin has targets other than the apicoplast. We also examined the pharmacokinetic-pharmacodynamic relationships of these antibacterials in an in vitro glass hollow-fiber system that exposes parasites to dynamically changing drug concentrations. The same total dose and area under the concentration-time curve (AUC) of the drug was deployed either as a single short-lived high peak (bolus) or as a constant low concentration (infusion). All four antibacterials were unambiguously time-driven against malaria parasites: infusions had twice the efficacy of bolus regimens, for the same AUC. The time-dependent efficacy of ciprofloxacin against malaria is in contrast to its concentration-driven action against bacteria. In silico simulations of clinical dosing regimens and resulting pharmacokinetics revealed that current regimens do not maximize time above the MICs of these drugs. Our findings suggest that simple and rational changes to dosing may improve the efficacy of antibacterials against falciparum malaria.

Drug targets for resistant malaria: Historic to future perspectives

New antimalarial targets are the prime need for the discovery of potent drug candidates. In order to fulfill this objective, antimalarial drug researches are focusing on promising targets in order to develop new drug candidates. Basic metabolism and biochemical process in the malaria parasite, i.e. Plasmodium falciparum can play an indispensable role in the identification of these targets. But, the emergence of resistance to antimalarial drugs is an escalating comprehensive problem with the progress of antimalarial drug development. The development of resistance has highlighted the need for the search of novel antimalarial molecules. The pharmaceutical industries are committed to new drug development due to the global recognition of this life threatening resistance to the currently available antimalarial therapy. The recent developments in the understanding of parasite biology are exhilarating this resistance issue which is further being ignited by malaria genome project. With this background of information, this review was aimed to highlights and provides useful information on various present and promising treatment approaches for resistant malaria, new progresses, pursued by some innovative targets that have been explored till date. This review also discusses modern and futuristic multiple approaches to antimalarial drug discovery and development with pictorial presentations highlighting the various targets, that could be exploited for generating promising new drugs in the future for drug resistant malaria.

Impact of Sickle Cell Trait and Naturally Acquired Immunity on Uncomplicated Malaria after Controlled Human Malaria Infection in Adults in Gabon

Controlled human malaria infection (CHMI) by direct venous inoculation (DVI) with 3,200 cryopreserved Plasmodium falciparum sporozoites (PfSPZ) consistently leads to parasitemia and malaria symptoms in malaria-naive adults. We used CHMI by DVI to investigate infection rates, parasite kinetics, and malaria symptoms in lifelong malaria-exposed (semi-immune) Gabonese adults with and without sickle cell trait. Eleven semi-immune Gabonese with normal hemoglobin (IA), nine with sickle cell trait (IS), and five nonimmune European controls with normal hemoglobin (NI) received 3,200 PfSPZ by DVI and were followed 28 days for parasitemia by thick blood smear (TBS) and quantitative polymerase chain reaction (qPCR) and for malaria symptoms. End points were time to parasitemia and parasitemia plus symptoms. PfSPZ Challenge was well tolerated and safe. Five of the five (100%) NI, 7/11 (64%) IA, and 5/9 (56%) IS volunteers developed parasitemia by TBS, and 5/5 (100%) NI, 9/11 (82%) IA, and 7/9 (78%) IS by qPCR, respectively. The time to parasitemia by TBS was longer in IA (geometric mean 16.9 days) and IS (19.1 days) than in NA (12.6 days) volunteers (P = 0.016, 0.021, respectively). Five of the five, 6/9, and 1/7 volunteers with parasitemia developed symptoms (P = 0.003, NI versus IS). Naturally adaptive immunity (NAI) to malaria significantly prolonged the time to parasitemia. Sickle cell trait seemed to prolong it further. NAI plus sickle cell trait, but not NAI alone, significantly reduced symptom rate. Twenty percent (4/20) semi-immunes demonstrated sterile protective immunity. Standardized CHMI with PfSPZ Challenge is a powerful tool for dissecting the impact of innate and naturally acquired adaptive immunity on malaria.

Validation of Putative Apicoplast-Targeting Drugs Using a Chemical Supplementation Assay in Cultured Human Malaria Parasites

Malaria parasites contain a relict plastid, the apicoplast, which is considered an excellent drug target due to its bacterial-like ancestry. Numerous parasiticidals have been proposed to target the apicoplast, but few have had their actual targets substantiated. Isopentenyl pyrophosphate (IPP) production is the sole required function of the apicoplast in the blood stage of the parasite life cycle, and IPP supplementation rescues parasites from apicoplast-perturbing drugs. Hence, any drug that kills parasites when IPP is supplied in culture must have a nonapicoplast target. Here, we use IPP supplementation to discriminate whether 23 purported apicoplast-targeting drugs are on- or off-target. We demonstrate that a prokaryotic DNA replication inhibitor (ciprofloxacin), several prokaryotic translation inhibitors (chloramphenicol, doxycycline, tetracycline, clindamycin, azithromycin, erythromycin, and clarithromycin), a tRNA synthase inhibitor (mupirocin), and two IPP synthesis pathway inhibitors (fosmidomycin and FR900098) have apicoplast targets. Intriguingly, fosmidomycin and FR900098 leave the apicoplast intact, whereas the others eventually result in apicoplast loss. Actinonin, an inhibitor of bacterial posttranslational modification, does not produce a typical delayed-death response but is rescued with IPP, thereby confirming its apicoplast target. Parasites treated with putative apicoplast fatty acid pathway inhibitors could not be rescued, demonstrating that these drugs have their primary targets outside the apicoplast, which agrees with the dispensability of the apicoplast fatty acid synthesis pathways in the blood stage of malaria parasites. IPP supplementation provides a simple test of whether a compound has a target in the apicoplast and can be used to screen novel compounds for mode of action.

Antimalarial drugs and the prevalence of mental and neurological manifestations: A systematic review and meta-analysis

Background: Antimalarial drugs affect the central nervous system, but it is difficult to differentiate the effect of these drugs from that of the malaria illness. We conducted a systematic review to determine the association between anti-malarial drugs and mental and neurological impairment in humans.  Methods: We systematically searched online databases, including Medline/PubMed, PsychoInfo, and Embase, for articles published up to 14th July 2016. Pooled prevalence, heterogeneity and factors associated with prevalence of mental and neurological manifestations were determined using meta-analytic techniques.  Results: Of the 2,349 records identified in the initial search, 51 human studies met the eligibility criteria. The median pooled prevalence range of mental and neurological manifestations associated with antimalarial drugs ranged from 0.7% (dapsone) to 48.3% (minocycline) across all studies, while it ranged from 0.6% (pyrimethamine) to 42.7% (amodiaquine) during treatment of acute malaria, and 0.7% (primaquine/dapsone) to 55.0% (sulfadoxine) during prophylaxis. Pooled prevalence of mental and neurological manifestations across all studies was associated with an increased number of antimalarial drugs (prevalence ratio= 5.51 (95%CI, 1.05-29.04); P=0.045) in a meta-regression analysis. Headaches (15%) and dizziness (14%) were the most common mental and neurological manifestations across all studies. Of individual antimalarial drugs still on the market, mental and neurological manifestations were most common with the use of sulphadoxine (55%) for prophylaxis studies and amodiaquine (42.7%) for acute malaria studies. Mefloquine affected more domains of mental and neurological manifestations than any other antimalarial drug.  Conclusions: Antimalarial drugs, particularly those used for prophylaxis, may be associated with mental and neurological manifestations, and the number of antimalarial drugs taken determines the association. Mental and neurological manifestations should be assessed following the use of antimalarial drugs.

Antimalarial drugs and the prevalence of mental and neurological manifestations: A systematic review and meta-analysis

Background: Antimalarial drugs affect the central nervous system, but it is difficult to differentiate the effect of these drugs from that of the malaria illness. We conducted a systematic review to determine the association between anti-malarial drugs and mental and neurological impairment in humans.  Methods: We systematically searched online databases, including Medline/PubMed, PsychoInfo, and Embase, for articles published up to 14th July 2016. Pooled prevalence, heterogeneity and factors associated with prevalence of mental and neurological manifestations were determined using meta-analytic techniques.  Results: Of the 2,349 records identified in the initial search, 51 human studies met the eligibility criteria. The median pooled prevalence range of mental and neurological manifestations associated with antimalarial drugs ranged from 0.7% (dapsone) to 48.3% (minocycline) across all studies, while it ranged from 0.6% (pyrimethamine) to 42.7% (amodiaquine) during treatment of acute malaria, and 0.7% (primaquine/dapsone) to 55.0% (sulfadoxine) during prophylaxis. Pooled prevalence of mental and neurological manifestations across all studies was associated with an increased number of antimalarial drugs (prevalence ratio= 5.51 (95%CI, 1.05-29.04); P=0.045) in a meta-regression analysis. Headaches (15%) and dizziness (14%) were the most common mental and neurological manifestations across all studies. Of individual antimalarial drugs still on the market, mental and neurological manifestations were most common with the use of sulphadoxine (55%) for prophylaxis studies and amodiaquine (42.7%) for acute malaria studies. Mefloquine affected more domains of mental and neurological manifestations than any other antimalarial drug.  Conclusions: Antimalarial drugs, particularly those used for prophylaxis, may be associated with mental and neurological manifestations, and the number of antimalarial drugs taken determines the association. Mental and neurological manifestations should be assessed following the use of antimalarial drugs.

Sulfadoxine-Pyrimethamine Exhibits Dose-Response Protection Against Adverse Birth Outcomes Related to Malaria and Sexually Transmitted and Reproductive Tract Infections

Background.

We conducted a prospective cohort study in Zambia among pregnant women who received intermittent preventive treatment using sulfadoxine-pyrimethamine (IPTp-SP).

Methods.

We calculated the odds ratios (ORs) of adverse birth outcomes by IPTp-SP exposure, 0–1 dose (n = 126) vs ≥2 doses (n = 590) and ≥2 doses (n = 310) vs ≥3 doses (n = 280) in 7 categories of malaria infection and sexually transmitted and reproductive tract infections (STIs/RTIs).

Results.

We found no significant differences in baseline prevalence of infection across IPTp-SP exposure groups. However, among women given 2 doses compared to 0–1 dose, the odds of any adverse birth outcome were reduced 45% (OR, 0.55; 95% confidence interval [CI], 0.36, 0.86) and 13% further with ≥3 doses (OR, 0.43; 95% CI, 0.27, 0.68). Two or more doses compared to 0–1 dose reduced preterm delivery by 58% (OR, 0.42; 95% CI, 0.27, 0.67) and 21% further with ≥3 doses (OR, 0.21; 95% CI, 0.13, 0.35). Women with malaria at enrollment who received ≥2 doses vs 0-1 had 76% lower odds of any adverse birth outcome (OR, 0.24; 95% 0.09, 0.66), and Neisseria gonorrhoeae and/or Chlamydia trachomatis had 92% lower odds of any adverse birth outcome (OR, 0.08; 95% CI, 0.01, 0.64). Women with neither a malaria infection nor STIs/RTIs who received ≥2 doses had 73% fewer adverse birth outcomes (OR, 0.27; 95% CI, 0.11, 0.68).

Conclusions.

IPTp-SP appears to protect against malaria, STIs/RTIs, and other unspecified causes of adverse birth outcome.

Herbicidal properties of antimalarial drugs

The evolutionary relationship between plants and the malarial parasite Plasmodium falciparum is well established and underscored by the P. falciparum apicoplast, an essential chloroplast-like organelle. As a result of this relationship, studies have demonstrated that herbicides active against plants are also active against P. falciparum and thus could act as antimalarial drug leads. Here we show the converse is also true; many antimalarial compounds developed for human use are highly herbicidal. We found that human antimalarial drugs (e.g. sulfadiazine, sulfadoxine, pyrimethamine, cycloguanil) were lethal to the model plant Arabidopsis thaliana at similar concentrations to market herbicides glufosinate and glyphosate. Furthermore, the physicochemical properties of these herbicidal antimalarial compounds were similar to commercially used herbicides. The implications of this finding that many antimalarial compounds are herbicidal proffers two novel applications: (i) using the genetically tractable A. thaliana to reveal mode-of-action for understudied antimalarial drugs, and (ii) co-opting antimalarial compounds as a new source for much needed herbicide lead molecules.

Enhanced efficacy of clindamycin hydrochloride encapsulated in PLA/PLGA based nanoparticle system for oral delivery

Clindamycin hydrochloride (CLH) is a clinically important oral antibiotic with wide spectrum of antimicrobial activity that includes gram-positive aerobes (staphylococci, streptococci etc.), most anaerobic bacteria, Chlamydia and certain protozoa. The current study was focused to develop a stabilised clindamycin encapsulated poly lactic acid (PLA)/poly (D,L-lactide-co-glycolide) (PLGA) nano-formulation with better drug bioavailability at molecular level. Various nanoparticle (NPs) formulations of PLA and PLGA loaded with CLH were prepared by solvent evaporation method varying drug: polymer concentration (1:20, 1:10 and 1:5) and characterised (size, encapsulation efficiency, drug loading, scanning electron microscope, differential scanning calorimetry [DSC] and Fourier transform infrared [FTIR] studies). The ratio 1:10 was found to be optimal for a monodispersed and stable nano formulation for both the polymers. NP formulations demonstrated a significant controlled release profile extended up to 144 h (both CLH-PLA and CLH-PLGA). The thermal behaviour (DSC) studies confirmed the molecular dispersion of the drug within the system. The FTIR studies revealed the intactness as well as unaltered structure of drug. The CLH-PLA NPs showed enhanced antimicrobial activity against two pathogenic bacteria Streptococcus faecalis and Bacillus cereus. The results notably suggest that encapsulation of CLH into PLA/PLGA significantly increases the bioavailability of the drug and due to this enhanced drug activity; it can be widely applied for number of therapies.

Comprehensive review on various strategies for antimalarial drug discovery

The resistance of malaria parasites to existing drugs carries on growing and progressively limiting our ability to manage this severe disease and finally lead to a massive global health burden. Till now, malaria control has relied upon the traditional quinoline, antifolate and artemisinin compounds. Very few new antimalarials were developed in the past 50 years. Among recent approaches, identification of novel chemotherapeutic targets, exploration of natural products with medicinal significance, covalent bitherapy having a dual mode of action into a single hybrid molecule and malaria vaccine development are explored heavily. The proper execution of these approaches and proper investment from international agencies will accelerate the discovery of drugs that provide new hope for the control or eventual eradication of this global infectious disease. This review explores various strategies for assessment and development of new antimalarial drugs. Current status and scientific value of previous approaches are systematically reviewed and new approaches provide a pragmatic forecast for future developments are introduced as well.

Efficacy and safety of re-treatment with the same artemisinin-based combination treatment (ACT) compared with an alternative ACT and quinine plus clindamycin after failure of first-line recommended ACT (QUINACT): a bicentre, open-label, phase 3, randomised controlled trial

BACKGROUND

Quinine or alternative artemisinin-based combination treatment (ACT) is the recommended rescue treatment for uncomplicated malaria. However, patients are often re-treated with the same ACT though it is unclear whether this is the most suitable approach. We assessed the efficacy and safety of re-treating malaria patients with uncomplicated failures with the same ACT used for the primary episode, compared with other rescue treatments.

METHODS

This was a bicentre, open-label, randomised, three-arm phase 3 trial done in Lisungi health centre in DR Congo, and Kazo health centre in Uganda in 2012-14. Children aged 12-60 months with recurrent malaria infection after treatment with the first-line ACT were randomly assigned to either re-treatment with the same first-line ACT, an alternative ACT, which were given for 3 days, or quinine-clindamycin (QnC), which was given for 5-7 days, following a 2:2:1 ratio. Randomisation was done by computer-generated randomisation list in a block design by country. The three treatment groups were assumed to have equivalent efficacy above 90%. Both the research team and parents or guardians were aware of treatment allocation. The primary outcome was the proportion of patients with an adequate clinical and parasitological response (ACPR) at day 28, in the per-protocol population. This trial was registered under the numbers NCT01374581 in ClinicalTrials.gov and PACTR201203000351114 in the Pan African Clinical Trials Registry.

FINDINGS

From May 22, 2012, to Jan 31, 2014, 571 children were included in the trial. 240 children were randomly assigned to the re-treatment ACT group, 233 to the alternative ACT group, and 98 to the QnC group. 500 children were assessed for the primary outcome. 71 others were not included because they did not complete the follow-up or PCR genotyping result was not conclusive. The ACPR response was similar in the three groups: 91·4% (95% CI 87·5-95·2) for the re-treatment ACT, 91·3% (95% CI 87·4-95·1) for the alternative ACT, and 89·5% (95% CI 83·0-96·0) for QnC. The estimates for rates of malaria recrudescence in the three treatment groups were similar (log-rank test: χ²=0·22, p=0·894). Artemether-lumefantrine was better tolerated than QnC (p=0·0005) and artesunate-amodiaquine (p<0·0001) in the modified intention-to-treat analysis. No serious adverse events were observed. The most common adverse events reported in the re-treatment ACT group were anorexia (31 [13%] of 240 patients), asthenia (20 [8%]), coughing (16 [7%]), abnormal behaviour (13 [5%]), and diarrhoea (12 [5%]). Anorexia (13 [6%] of 233 patients) was the most frequently reported adverse event in the alternative ACT group. The most commonly reported adverse events in the QnC group were anorexia (12 [12%] of 98 patients), abnormal behaviour (6 [6%]), asthenia (6 [6%]), and pruritus (5 [5%]).

INTERPRETATION

Re-treatment with the same ACT shows similar efficacy as recommended rescue treatments and could be considered for rescue treatment for Plasmodium falciparum malaria. However, the effect of this approach on the selection of resistant strains should be monitored to ensure that re-treatment with the same ACT does not contribute to P falciparum resistance.

FUNDING

Fonds Wetenschappelijk Onderzoek, Vlaamse Interuniversitaire Raad-Universitaire Ontwikkelings Samenwerking, European and Developing Countries Clinical Trials Partnership, and the Belgian Technical Cooperation-Programme d'Etudes et d'Expertises-in the Democratic Republic of Congo.

In Vivo Efficacy and Tolerability of Artesunate-Azithromycin for the Treatment of Falciparum Malaria in Vietnam

Safe and effective antimalarial drugs are required for the treatment of pregnant women. We report a 3-day regimen of artesunate (4 mg/kg/day)-azithromycin (25 mg/kg/day) (ASAZ) to be efficacious (polymerase chain reaction-corrected cure rate of 96.7%) and well tolerated in the treatment of Plasmodium falciparum malaria in children (N = 11) and adults (N = 19), in Vietnam in 2010. In comparison, the cure rate for artesunate (4 mg/kg on day 0, 2 mg/kg on days 1-6) was 90.0% in children (N = 7) and adults (N = 23). Because azithromycin is considered safe in pregnancy, our findings provide further evidence that ASAZ should be evaluated for the treatment of pregnant women with malaria.

FR-900098, an antimalarial development candidate that inhibits the non-mevalonate isoprenoid biosynthesis pathway, shows no evidence of acute toxicity and genotoxicity

FR-900098 is an inhibitor of 1-deoxy-d-xylulose-5-phosphate (DXP) reductoisomerase, the second enzyme in the non-mevalonate isoprenoid biosynthesis pathway. In previous studies, FR-900098 was shown to possess potent antimalarial activity in vitro and in a murine malaria model. In order to provide a basis for further preclinical and clinical development, we studied the acute toxicity and genotoxicity of FR-900098. We observed no acute toxicity in rats, i.e. there were no clinical signs of toxicity and no substance-related deaths after the administration of a single dose of 3000 mg/kg body weight orally or 400 mg/kg body weight intravenously. No mutagenic potential was detected in the Salmonella typhimurium reverse mutation assay (Ames test) or an in vitro mammalian cell gene mutation test using mouse lymphoma L5178Y/TK(+/-) cells (clone 3.7.2C), both with and without metabolic activation. In addition, FR-900098 demonstrated no clastogenic or aneugenic capability or significant adverse effects on blood formation in an in vivo micronucleus test with bone marrow erythrocytes from NMRI mice. We conclude that FR-900098 lacks acute toxicity and genotoxicity, supporting its further development as an antimalarial drug.

Macrolides and associated antibiotics based on similar mechanism of action like lincosamides in malaria

Malaria, a parasite vector-borne disease, is one of the biggest health threats in tropical regions, despite the availability of malaria chemoprophylaxis. The emergence and rapid extension of Plasmodium falciparum resistance to various anti-malarial drugs has gradually limited the potential malaria therapeutics available to clinicians. In this context, macrolides and associated antibiotics based on similar mechanism of action like lincosamides constitute an interesting alternative in the treatment of malaria. These molecules, whose action spectrum is similar to that of tetracyclines, are typically administered to children and pregnant women. Recent studies have examined the effects of azithromycin and the lincosamide clindamycin, on isolates from different continents. Azithromycin and clindamycin are effective and well tolerated in the treatment of uncomplicated malaria in combination with quinine. This literature review assesses the roles of macrolides and lincosamides in the prophylaxis and treatment of malaria.

New insight-guided approaches to detect, cure, prevent and eliminate malaria

New challenges posed by the development of resistance against artemisinin-based combination therapies (ACTs) as well as previous first-line therapies, and the continuing absence of vaccine, have given impetus to research in all areas of malaria control. This review portrays the ongoing progress in several directions of malaria research. The variants of RTS,S and apical membrane antigen 1 (AMA1) are being developed and test adapted as multicomponent and multistage malaria control vaccines, while many other vaccine candidates and methodologies to produce antigens are under experimentation. To track and prevent the spread of artemisinin resistance from Southeast Asia to other parts of the world, rolling circle-enhanced enzyme activity detection (REEAD), a time- and cost-effective malaria diagnosis in field conditions, and a DNA marker associated with artemisinin resistance have become available. Novel mosquito repellents and mosquito trapping and killing techniques much more effective than the prevalent ones are undergoing field testing. Mosquito lines stably infected with their symbiotic wild-type or genetically engineered bacteria that kill sympatric malaria parasites are being constructed and field tested for stopping malaria transmission. A complementary approach being pursued is the addition of ivermectin-like drug molecules to ACTs to cure malaria and kill mosquitoes. Experiments are in progress to eradicate malaria mosquito by making it genetically male sterile. High-throughput screening procedures are being developed and used to discover molecules that possess long in vivo half life and are active against liver and blood stages for the fast cure of malaria symptoms caused by simple or relapsing and drug-sensitive and drug-resistant types of varied malaria parasites, can stop gametocytogenesis and sporogony and could be given in one dose. Target-based antimalarial drug designing has begun. Some of the putative next-generation antimalarials that possess in their scaffold structure several of the desired properties of malaria cure and control are exemplified by OZ439, NITD609, ELQ300 and tafenoquine that are already undergoing clinical trials, and decoquinate, usnic acid, torin-2, ferroquine, WEHI-916, MMV396749 and benzothiophene-type N-myristoyltransferase (NMT) inhibitors, which are candidates for future clinical usage. Among these, NITD609, ELQ300, decoquinate, usnic acid, torin-2 and NMT inhibitors not only cure simple malaria and are prophylactic against simple malaria, but they also cure relapsing malaria.

Severe Malaria Complicated by G6PD Deficiency in a Pediatric Tanzanian Immigrant

Approximately 1,500 cases of malaria are diagnosed in the United States each year. Most cases are travelers and immigrants returning from parts of the world where malaria transmission occurs. Malaria is the most frequent cause of systemic febrile illness without localizing symptoms in travelers returning from the developing world, so vigilance by providers is needed when evaluating patients returning from areas in which malaria is endemic. Despite the availability of effective treatment, malaria still accounts for more than 1 million deaths per year worldwide, with rates being disproportionately high in young children under the age of 5. We present the case of a 4-year-old refugee who emigrated from Tanzania with severe malaria due to dual infections of Plasmodium falciparum and P. ovale, whose treatment course was complicated by quinidine gluconate cardiotoxicity and glucose-6-phosphate dehydrogenase deficiency.

Antimalarial compounds in Phase II clinical development

INTRODUCTION

Malaria is a major health problem in endemic countries and chemotherapy remains the most important tool in combating it. Treatment options are limited and essentially rely on a single drug class - the artemisinins. Efforts are ongoing to restrict the evolving threat of artemisinin resistance but declining sensitivity has been reported. Fueled by the ambitious aim of malaria eradication, novel antimalarial compounds, with improved properties, are now in the progressive phase of drug development.

AREAS COVERED

Herein, the authors describe antimalarial compounds currently in Phase II clinical development and present the results of these investigations.

EXPERT OPINION

Thanks to recent efforts, a number of promising antimalarial compounds are now in the pipeline. First safety data have been generated for all of these candidates, although their efficacy as antimalarials is still unclear for most of them. Of particular note are KAE609, KAF156 and DSM265, which are of chemical scaffolds new to malaria chemotherapy and would truly diversify antimalarial options. Apart from SAR97276, which also has a novel chemical scaffold that has had its development stopped, all other compounds in the pipeline belong to already known substance classes, which have been chemically modified. At this moment in time, there is not one standout compound that will revolutionize malaria treatment but several compounds that will add to its control in the future.

Transformation of saturated nitrogen-containing heterocyclic compounds by microorganisms

The saturated nitrogen-containing heterocyclic compounds include many drugs and compounds that may be used as synthons for the synthesis of other pharmacologically active substances. The need for new derivatives of saturated nitrogen-containing heterocycles for organic synthesis, biotechnology and the pharmaceutical industry, including optically active derivatives, has increased interest in microbial synthesis. This review provides an overview of microbial technologies that can be valuable to produce new derivatives of saturated nitrogen-containing heterocycles, including hydroxylated derivatives. The chemo-, regio- and enantioselectivity of microbial processes can be indispensable for the synthesis of new compounds. Microbial processes carried out with fungi, including Beauveria bassiana, Cunninghamella verticillata, Penicillium simplicissimum, Aspergillus niger and Saccharomyces cerevisiae, and bacteria, including Pseudomonas sp., Sphingomonas sp. and Rhodococcus erythropolis, biotransform many substrates efficiently. Among the biological activities of saturated nitrogen-containing heterocyclic compounds are antimicrobial, antitumor, antihypertensive and anti-HIV activities; some derivatives are effective for the treatment and prevention of malaria and trypanosomiasis, and others are potent glycosidase inhibitors.

Antimalarial interaction of quinine and quinidine with clarithromycin

Quinine (QN) and quinidine (QND) have been commonly used as effective and affordable antimalarials for over many years. Quinine primarily is used for severe malaria treatment. However, plasmodia resistance to these drugs and poor patient compliance limits their administration to the patients. The declining sensitivity of the parasite to the drugs can thus be dealt with by combining with a suitable partner drug. In the present study QN/QND was assessed in combination with clarithromycin (CLTR), an antibiotic of the macrolide family. In vitro interactions of these drugs with CLTR against Plasmodium falciparum (P. falciparum) have shown a synergistic response with mean sum fractional inhibitory concentrations (ΣFICs) of ≤1 (0.85 ± 0.11 for QN + CLTR and 0.64 ± 0.09 for QND + CLTR) for all the tested combination ratios. Analysis of this combination of QN/QND with CLTR in mouse model against Plasmodium yoelii nigeriensis multi-drug resistant (P. yoelii nigeriensis MDR) showed that a dose of 200 mg/kg/day for 4 days of QN or QND produces 100% curative effect with 200 mg/kg/day for 7 days and 150 mg/kg/day for 7 days CLTR respectively, while the same dose of individual drugs could produce only up to a maximum 20% cure. It is postulated that CLTR, a CYP3A4 inhibitor, might have caused reduced CYP3A4 activity leading to increased plasma level of the QN/QND to produce enhanced antimalarial activity. Further, parasite apicoplast disruption by CLTR synergies the antimalarial action of QN and QND.

Inadequate efficacy of a new formulation of fosmidomycin-clindamycin combination in Mozambican children less than three years old with uncomplicated Plasmodium falciparum malaria

The combination of fosmidomycin and clindamycin (F/C) is effective in adults and older children for the treatment of malaria and could be an important alternative to existing artemisinin-based combinations (ACTs) if proven to work in younger children. We conducted an open-label clinical trial to assess the efficacy, safety, and tolerability of F/C for the treatment of uncomplicated P. falciparum malaria in Mozambican children <3 years of age. Aqueous solutions of the drugs were given for 3 days, and the children were followed up for 28 days. The primary outcome was the PCR-corrected adequate clinical and parasitological response at day 28. Secondary outcomes included day 7 and 28 uncorrected cure rates and fever (FCT) and parasite (PCT) clearance times. Fifty-two children were recruited, but only 37 patients were evaluable for the primary outcome. Day 7 cure rates were high (94.6%; 35/37), but the day 28 PCR-corrected cure rate was 45.9% (17/37). The FCT was short (median, 12 h), but the PCT was longer (median, 72 h) than in previous studies. Tolerability was good, and most common adverse events were related to the recurrence of malaria. The poor efficacy observed for the F/C combination may be a consequence of the new formulations used, differential bioavailability in younger children, naturally occurring variations in parasite sensitivity to the drugs, or an insufficient enhancement of their effects by naturally acquired immunity in young children. Additional studies should be conducted to respond to the many uncertainties arising from this trial, which should not discourage further evaluation of this promising combination.

Clindamycin plus quinine for treating uncomplicated falciparum malaria: a systematic review and meta-analysis

Background

Artemisinin-based combinations are recommended for treatment of uncomplicated falciparum malaria, but are costly and in limited supply. Clindamycin plus quinine is an alternative non-artemisinin-based combination recommended by World Health Organization. The efficacy and safety of clindamycin plus quinine is not known. This systematic review aims to assess the efficacy of clindamycin plus quinine versus other anti-malarial drugs in the treatment of uncomplicated falciparum malaria.

Methods

All randomized controlled trials comparing clindamycin plus quinine with other anti-malarial drugs in treating uncomplicated malaria were included in this systematic review. Databases searched included: Cochrane Central Register of Controlled Trials, MEDLINE, EMBASE and LILACS. Two authors independently assessed study eligibility, extracted data and assessed methodological quality. The primary outcome measure was treatment failure by day 28. Dichotomous data was compared using risk ratio (RR), in a fixed effects model.

Results

Seven trials with 929 participants were included. Clindamycin plus quinine significantly reduced the risk of day 28 treatment failure compared with quinine (RR 0.14 [95% CI 0.07 to 0.29]), quinine plus sulphadoxine-pyrimethamine (RR 0.17 [95% CI 0.06 to 0.44]), amodiaquine (RR 0.11 [95% CI 0.04 to 0.27]), or chloroquine (RR 0.11 [95% CI 0.04 to 0.29]), but had similar efficacy compared with quinine plus tetracycline (RR 0.33 [95% CI 0.01 to 8.04]), quinine plus doxycycline (RR 1.00 [95% CI 0.21 to 4.66]), artesunate plus clindamycin (RR 0.57 [95% CI 0.26 to 1.24]), or chloroquine plus clindamycin (RR 0.38 [95% CI 0.13 to 1.10]). Adverse events were similar across treatment groups but were poorly reported.

Conclusion

The evidence on the efficacy of clindamycin plus quinine as an alternative treatment for uncomplicated malaria is inconclusive. Adequately powered trials are urgently required to compare this combination with artemisinin-based combinations.