Miltefosine: a review of its pharmacology and therapeutic efficacy in the treatment of leishmaniasis

Revisiting the dipeptidyl carboxypeptidase inhibitor captopril as a source of pan anti-trypanosomatid agents

The protozoan parasites Trypanosoma brucei, Trypanosoma cruzi and Leishmania spp. are responsible for continued propagation of neglected tropical diseases such as African sleeping sickness, Chagas disease and leishmaniasis respectively. Following a report that captopril targets Leishmania donovani dipeptidyl carboxypeptidase, a series of simple proline amides and captopril analogues were synthesized and found to exhibit 1-2 μM in vitro inhibition and selectivity against Trypanosoma brucei, Trypanosoma cruzi and Leishmania spp. The results were corroborated with computational docking studies. Arguably, the synthetic proline amides represent the structurally simplest examples of in vitro pan antiprotozoal compounds.

Halogen substituted aurones as potential apoptotic agents: synthesis, anticancer evaluation, molecular docking, ADMET and DFT study

A series of halogen-substituted aurone derivatives (2a-k) were synthesized and evaluated for an anti-proliferative study against NCI 60 cancer cell line panel and showed that most of the compounds predominantly exhibited promising activity against MCF-7. Compound 2e exhibited promising anticancer activity against the MCF-7 cancer cell line with 84.98% percentage growth inhibition in a single dose assay of 10 μM with an IC50 value of 8.157 ± 0.713 μM. In apoptotic assay, the effect of compound 2e on the cell cycle progression indicated that exposure of MCF-7 cells to compound 2e induced a significant disruption in the cell cycle profile including a time-dependent decrease in the cell population at G0/G1 and G2/M phase and arrests the cell cycle at the S phase. In silico, molecular docking ADME and toxicity studies of all compounds were also carried out. The docking study revealed that all the aurone derivatives displayed good docking scores ranging from -7.066 to -8.573. The results of Molecular Electrostatic Potential Mapping (MESP) and Density Functional Theory (DFT) studies of the most active compound 2e and least active compound 2k also favoured the experimental results.

Ophthalmic adverse effects of miltefosine in the treatment of leishmaniasis: a systematic review

OBJECTIVE

Miltefosine stands as the sole oral medication approved for the treatment of leishmaniasis. The appearance of severe ophthalmic toxicities induced by miltefosine in the context of leishmaniasis treatment is a matter of significant concern. The main objective of this study is to present a comprehensive summary of the ophthalmic adverse effects associated with miltefosine when used in the treatment of leishmaniasis.

METHODS

A systematic search was performed on PubMed, ScienceDirect, Embase, Scopus, and Google Scholar, covering articles from inception up to June 2023, without language restrictions, to identify relevant studies documenting ocular toxicity following miltefosine treatment for leishmaniasis.

RESULTS

A total of eight studies involving 31 leishmaniasis patients who developed ocular toxicities while undergoing miltefosine treatment were included in the analysis. These studies were conducted in various regions, with five originating from India, two from Bangladesh, and one from Nepal. Patients presented a spectrum of ophthalmic complications, including uveitis, keratitis, scleritis, and Mooren's ulcer. Commonly reported symptoms included pain, redness, excessive tearing, partial vision impairment, permanent blindness, light sensitivity, and the appearance of white spots on the eye. On average, patients received miltefosine treatment for a duration of 47 days before experiencing the onset of ocular problems. It is important to note that the risk of ocular toxicities increases with prolonged use of miltefosine.

CONCLUSIONS

Therefore, to mitigate the potential for irreversible damage to the eyes, it is imperative that all individuals undergoing miltefosine therapy undergo regular eye examinations.

Milteforan, a promising veterinary commercial product against feline sporotrichosis

Sporotrichosis, the cutaneous mycosis most commonly reported in Latin America, is caused by the Sporothrix clinical clade species, including Sporothrix brasiliensis and Sporothrix schenckii sensu stricto. Due to its zoonotic transmission in Brazil, S. brasiliensis represents a significant health threat to humans and domestic animals. Itraconazole, terbinafine, and amphotericin B are the most used antifungals for treating sporotrichosis. However, many strains of S. brasiliensis and S. schenckii have shown resistance to these agents, highlighting the importance of finding new therapeutic options. Here, we demonstrate that milteforan, a commercial veterinary product against dog leishmaniasis, whose active principle is miltefosine, is a possible therapeutic alternative for the treatment of sporotrichosis, as observed by its fungicidal activity in vitro against different strains of S. brasiliensis and S. schenckii. Fluorescent miltefosine localizes to the Sporothrix cell membrane and mitochondria and causes cell death through increased permeabilization. Milteforan decreases S. brasiliensis fungal burden in A549 pulmonary cells and bone marrow-derived macrophages and also has an immunomodulatory effect by decreasing TNF-α, IL-6, and IL-10 production. Our results suggest milteforan as a possible alternative to treat feline sporotrichosis.

IMPORTANCE

Sporotrichosis is an endemic disease in Latin America caused by different species of Sporothrix. This fungus can infect domestic animals, mainly cats and eventually dogs, as well as humans. Few drugs are available to treat this disease, such as itraconazole, terbinafine, and amphotericin B, but resistance to these agents has risen in the last few years. Alternative new therapeutic options to treat sporotrichosis are essential. Here, we propose milteforan, a commercial veterinary product against dog leishmaniasis, whose active principle is miltefosine, as a possible therapeutic alternative for treating sporotrichosis. Milteforan decreases S. brasiliensis fungal burden in human and mouse cells and has an immunomodulatory effect by decreasing several cytokine production.

Souza AB, Levita DP, Mello CC, da Silva AFM, dos Santos TC, Ronconi CM. Innovating Leishmaniasis Treatment: A Critical Chemist's Review of Inorganic Nanomaterials

Leishmaniasis, a critical Neglected Tropical Disease caused by Leishmania protozoa, represents a significant global health risk, particularly in resource-limited regions. Conventional treatments are effective but suffer from serious limitations, such as toxicity, prolonged treatment courses, and rising drug resistance. Herein, we highlight the potential of inorganic nanomaterials as an innovative approach to enhance Leishmaniasis therapy, aligning with the One Health concept by considering these treatments' environmental, veterinary, and public health impacts. By leveraging the adjustable properties of these nanomaterials─including size, shape, and surface charge, tailored treatments for various diseases can be developed that are less harmful to the environment and nontarget species. We review recent advances in metal-, oxide-, and carbon-based nanomaterials for combating Leishmaniasis, examining their mechanisms of action and their dual use as standalone treatments or drug delivery systems. Our analysis highlights a promising yet underexplored frontier in employing these materials for more holistic and effective disease management.

N-Pyrazolyl- and N-Triazolylamines and -Ureas as Antileishmanial and Antitrypanosomal Drugs

Three types of modifications of antileishmanial pyrazole lead compounds 7 and 8 were conducted to expand understanding of the relationships between structural features and antileishmanial/antitrypanosomal activity: (1) the pyrazole core was retained or replaced by a 1,2,4-triazole ring; (2) various aryl moieties including 2-fluorophenyl, pyridin-3-yl and pyrazin-2-yl rings were attached at 3-position of the core azole; (3) either arylmethylamino or ureido substituents were introduced at 5-position of the azole core. The synthesis followed established routes starting with esters 9 or 15 and anhydride 21. The synthesized 3-arylpyrazoles and 3-aryl-1,2,4-triazoles had only very low antileishmanial activity. The 2-fluorophenyl-substituted pyrazole 18c revealed the highest antileishmanial activity of this series of compounds, but its IC50 value (20 μM) still indicates low activity. However, low micromolar antitrypanosomal activity was detected for the pyridin-3-yl-substituted pyrazoles 12b (IC50=4.7 μM) and 14a (IC50=2.1 μM). Their IC50 values are comparable with the IC50 values of the reference compounds benznidazole and nifurtimox. Whereas only low unspecific cytotoxicity at the primary peritoneal mouse macrophages (PMM) was detected, considerable cytotoxicity at MRC-5 human fibroblast cells was found for both pyrazoles 12b an 14a. The activity of pyrazole 12b against T. cruzi is 4-fold higher than its unspecific MRC-5 cytotoxicity.

Investigation of miltefosine-model membranes interactions at the molecular level for two different PS levels modeling cancer cells

Miltefosine (MLT) is a broad-spectrum drug included in the alkylphospholipids (APL) used against leishmania and various types of cancer. The most crucial feature of APLs is that they are thought to only kill cancerous cells without harming normal cells. However, the molecular mechanism of action of APLs is not completely understood. The increase in the phosphatidylserine (PS) ratio is a marker showing the stage of cancer and even metastasis. The goal of this research was to investigate the molecular effects of miltefosine at the molecular level in different PS ratios. The effects of MLT on membrane phase transition, membrane orders, and dynamics were studied using DPPC/DPPS (3:1) and DPPC/DPPS (1:1) multilayer (MLV) vesicles mimicking DPPS ratio variation, Differential Scanning Calorimetry (DSC), and Fourier Transform Infrared spectroscopy (FTIR). Our findings indicate that miltefosine is evidence at the molecular level that it is directed towards the tumor cell and that the drug's effect increases with the increase of anionic lipids in the membrane depending on the stage of cancer.

Determining tissue distribution of the oral antileishmanial agent miltefosine: a physiologically-based pharmacokinetic modeling approach

Miltefosine (MTS) is the only approved oral drug for treating leishmaniasis caused by intracellular Leishmania parasites that localize in macrophages of the liver, spleen, skin, bone marrow, and lymph nodes. MTS is extensively distributed in tissues and has prolonged elimination half-lives due to its high plasma protein binding, slow metabolic clearance, and minimal urinary excretion. Thus, understanding and predicting the tissue distribution of MTS help assess therapeutic and toxicologic outcomes of MTS, especially in special populations, e.g., pediatrics. In this study, a whole-body physiologically-based pharmacokinetic (PBPK) model of MTS was built on mice and extrapolated to rats and humans. MTS plasma and tissue concentration data obtained by intravenous and oral administration to mice were fitted simultaneously to estimate model parameters. The resulting high tissue-to-plasma partition coefficient values corroborate extensive distribution in all major organs except the bone marrow. Sensitivity analysis suggests that plasma exposure is most susceptible to changes in fraction unbound in plasma. The murine oral-PBPK model was further validated by assessing overlay of simulations with plasma and tissue profiles obtained from an independent study. Subsequently, the murine PBPK model was extrapolated to rats and humans based on species-specific physiological and drug-related parameters, as well as allometrically scaled parameters. Fold errors for pharmacokinetic parameters were within acceptable range in both extrapolated models, except for a slight underprediction in the human plasma exposure. These animal and human PBPK models are expected to provide reliable estimates of MTS tissue distribution and assist dose regimen optimization in special populations.

Skin pharmacokinetics of miltefosine in the treatment of post-kala-azar dermal leishmaniasis in South Asia

INTRODUCTION

Post-kala-azar dermal leishmaniasis (PKDL) arises as a dermal complication following a visceral leishmaniasis (VL) infection. Current treatment options for PKDL are unsatisfactory, and there is a knowledge gap regarding the distribution of antileishmanial compounds within human skin. The present study investigated the skin distribution of miltefosine in PKDL patients, with the aim to improve the understanding of the pharmacokinetics at the skin target site in PKDL.

METHODS

Fifty-two PKDL patients underwent treatment with liposomal amphotericin B (20 mg/kg) plus miltefosine (allometric dosing) for 21 days. Plasma concentrations of miltefosine were measured on study days 8, 15, 22 and 30, while a punch skin biopsy was taken on day 22. A physiologically based pharmacokinetic (PBPK) model was developed to evaluate the distribution of miltefosine into the skin.

RESULTS

Following the allometric weight-based dosing regimen, median miltefosine concentrations on day 22 were 43.73 µg/g (IQR: 21.94-60.65 µg/g) in skin and 33.29 µg/mL (IQR: 25.9-42.58 µg/mL) in plasma. The median individual concentration ratio of skin to plasma was 1.19 (IQR: 0.79-1.9). In 87% (45/52) of patients, skin exposure was above the suggested EC90 PK target of 10.6 mg/L associated with in vitro susceptibility. Simulations indicated that the residence time of miltefosine in the skin would be more than 2-fold longer than in plasma, estimated by a mean residence time of 604 versus 266 hours, respectively.

CONCLUSION

This study provides the first accurate measurements of miltefosine penetration into the skin, demonstrating substantial exposure and prolonged retention of miltefosine within the skin. These findings support the use of miltefosine in cutaneous manifestations of leishmaniasis. In combination with parasitological and clinical data, these results are critical for the future optimization of combination therapies with miltefosine in the treatment of PKDL.

The role of Nrf2 signaling in parasitic diseases and its therapeutic potential

In response to invading parasites, one of the principal arms of innate immunity is oxidative stress, caused by reactive oxygen species (ROS). However, oxidative stresses play dual functions in the disease, whereby free radicals promote pathogen removal, but they can also trigger inflammation, resulting in tissue injuries. A growing body of evidence has strongly supported the notion that nuclear factor erythroid 2-related factor 2 (NRF) signaling is one of the main antioxidant pathways to combat this oxidative burst against parasites. Given the important role of NRF2 in oxidative stress, in this review, we investigate the activation mechanism of the NRF2 antioxidant pathway in different parasitic diseases, such as malaria, leishmaniasis, trypanosomiasis, toxoplasmosis, schistosomiasis, entamoebiasis, and trichinosis.

Strategies of Pharmacological Repositioning for the Treatment of Medically Relevant Mycoses

Fungal infections represent a worldwide concern for public health, due to their prevalence and significant increase in cases each year. Among the most frequent mycoses are those caused by members of the genera Candida, Cryptococcus, Aspergillus, Histoplasma, Pneumocystis, Mucor, and Sporothrix, which have been treated for years with conventional antifungal drugs, such as flucytosine, azoles, polyenes, and echinocandins. However, these microorganisms have acquired the ability to evade the mechanisms of action of these drugs, thus hindering their treatment. Among the most common evasion mechanisms are alterations in sterol biosynthesis, modifications of drug transport through the cell wall and membrane, alterations of drug targets, phenotypic plasticity, horizontal gene transfer, and chromosomal aneuploidies. Taking into account these problems, some research groups have sought new therapeutic alternatives based on drug repositioning. Through repositioning, it is possible to use existing pharmacological compounds for which their mechanism of action is already established for other diseases, and thus exploit their potential antifungal activity. The advantage offered by these drugs is that they may be less prone to resistance. In this article, a comprehensive review was carried out to highlight the most relevant repositioning drugs to treat fungal infections. These include antibiotics, antivirals, anthelmintics, statins, and anti-inflammatory drugs.

Critically Appraised Topic on Canine Leishmaniosis: Does Treatment with Antimonials and Allopurinol Have the Same Clinical and Clinicopathological Efficacy as Treatment with Miltefosine and Allopurinol, after One Month of Treatment?

The treatment of canine leishmaniosis commonly involves meglumine antimoniate with allopurinol or miltefosine with allopurinol. This study aims to compare the clinical and clinicopathological efficacy at 28-30 days of conventional dosing regimens for both treatments using the critically appraised topic methodology. A comprehensive search across three databases (PubMed, CAB Abstracts, and Web of Science) from March 2004 to September 2023 yielded 16 relevant articles, encompassing 325 ogs treated with meglumine antimoniate and allopurinol, and 273 dogs treated with miltefosine and allopurinol. The findings indicated a significantly higher rate of complete clinical cure in the group treated with meglumine antimoniate and allopurinol. Most dogs in both groups exhibited improvement in clinicopathological alterations after one month of treatment. No significant difference was observed in the number of dogs that showed a negative Leishmania qPCR between the two groups, one month post-treatment. However, quantitative serology results were not commonly reported in the available data and therefore this aspect could not be compared.

ABC transporter inhibition by beauvericin partially overcomes drug resistance in Leishmania tropica

Leishmaniasis is a neglected tropical disease infecting the world's poorest populations. Miltefosine (ML) remains the primary oral drug against the cutaneous form of leishmaniasis. The ATP-binding cassette (ABC) transporters are key players in the xenobiotic efflux, and their inhibition could enhance the therapeutic index. In this study, the ability of beauvericin (BEA) to overcome ABC transporter-mediated resistance of Leishmania tropica to ML was assessed. In addition, the transcription profile of genes involved in resistance acquisition to ML was inspected. Finally, we explored the efflux mechanism of the drug and inhibitor. The efficacy of ML against all developmental stages of L. tropica in the presence or absence of BEA was evaluated using an absolute quantification assay. The expression of resistance genes was evaluated, comparing susceptible and resistant strains. Finally, the mechanisms governing the interaction between the ABC transporter and its ligands were elucidated using molecular docking and dynamic simulation. Relative quantification showed that the expression of the ABCG sub-family is mostly modulated by ML. In this study, we used BEA to impede resistance of Leishmania tropica. The IC50 values, following BEA treatment, were significantly reduced from 30.83, 48.17, and 16.83 µM using ML to 8.14, 11.1, and 7.18 µM when using a combinatorial treatment (ML + BEA) against promastigotes, axenic amastigotes, and intracellular amastigotes, respectively. We also demonstrated a favorable BEA-binding enthalpy to L. tropica ABC transporter compared to ML. Our study revealed that BEA partially reverses the resistance development of L. tropica to ML by blocking the alternate ATP hydrolysis cycle.

Susceptibility of Leishmania to novel pentavalent organometallics: Investigating impact on DNA and membrane integrity in antimony(III)-sensitive and -resistant strains

The aim the present study was to investigate the impact of novel pentavalent organobismuth and organoantimony complexes on membrane integrity and their interaction with DNA, activity against Sb(III)-sensitive and -resistant Leishmania strains and toxicity in mammalian peritoneal macrophages. Ph3M(L)2 type complexes were synthesized, where M = Sb(V) or Bi(V) and L = deprotonated 3-(dimethylamino)benzoic acid or 2-acetylbenzoic acid. Both organobismuth(V) and organoantimony(V) complexes exhibited efficacy at micromolar concentrations against Leishmania amazonensis and L. infantum but only the later ones demonstrated biocompatibility. Ph3Sb(L1)2 and Ph3Bi(L1)2 demonstrated distinct susceptibility profiles compared to inorganic Sb(III)-resistant strains of MRPA-overexpressing L. amazonensis and AQP1-mutated L. guyanensis. These complexes were able to permeate the cell membrane and interact with the Leishmania DNA, suggesting that this effect may contribute to the parasite growth inhibition via apoptosis. Taken altogether, our data substantiate the notion of a distinct mechanism of uptake pathway and action in Leishmania for these organometallic complexes, distinguishing them from the conventional inorganic antimonial drugs.

Experimental structure based drug design (SBDD) applications for anti-leishmanial drugs: A paradigm shift?

Leishmaniasis is a group of neglected tropical diseases caused by at least 20 species of Leishmania protozoa, which are spread by the bite of infected sandflies. There are three main forms of the disease: cutaneous leishmaniasis (CL, the most common), visceral leishmaniasis (VL, also known as kala-azar, the most serious), and mucocutaneous leishmaniasis. One billion people live in areas endemic to leishmaniasis, with an annual estimation of 30,000 new cases of VL and more than 1 million of CL. New treatments for leishmaniasis are an urgent need, as the existing ones are inefficient, toxic, and/or expensive. We have revised the experimental structure-based drug design (SBDD) efforts applied to the discovery of new drugs against leishmaniasis. We have grouped the explored targets according to the metabolic pathways they belong to, and the key achieved advances are highlighted and evaluated. In most cases, SBDD studies follow high-throughput screening campaigns and are secondary to pharmacokinetic optimization, due to the majoritarian belief that there are few validated targets for SBDD in leishmaniasis. However, some SBDD strategies have significantly contributed to new drug candidates against leishmaniasis and a bigger number holds promise for future development.

Evaluation and discovery of novel benzothiazole derivatives as promising hits against Leishmania infantum

An early exploration of the benzothiazole class against two kinetoplastid parasites, Leishmania infantum and Trypanosoma cruzi, has been performed after the identification of a benzothiazole derivative as a suitable antileishmanial initial hit. The first series of derivatives focused on the acyl fragment of its class, evaluating diverse linear and cyclic, alkyl and aromatic substituents, and identified two other potent compounds, the phenyl and cyclohexyl derivatives. Subsequently, new compounds were designed to assess the impact of the presence of diverse substituents on the benzothiazole ring or the replacement of the endocyclic sulfur by other heteroatoms. All compounds showed relatively low cytotoxicity, resulting in decent selectivity indexes for the most active compounds. Ultimately, the in vitro ADME properties of these compounds were assessed, revealing a satisfying water solubility, gastrointestinal permeability, despite their low metabolic stability and high lipophilicity. Consequently, compounds 5 and 6 were identified as promising hits for further hit-to-lead exploration within this benzothiazole class against L. infantum, thus providing promising starting points for the development of antileishmanial candidates.

Unmasking the Mechanism behind Miltefosine: Revealing the Disruption of Intracellular Ca2+ Homeostasis as a Rational Therapeutic Target in Leishmaniasis and Chagas Disease

Originally developed as a chemotherapeutic agent, miltefosine (hexadecylphosphocholine) is an inhibitor of phosphatidylcholine synthesis with proven antiparasitic effects. It is the only oral drug approved for the treatment of Leishmaniasis and American Trypanosomiasis (Chagas disease). Although its precise mechanisms are not yet fully understood, miltefosine exhibits broad-spectrum anti-parasitic effects primarily by disrupting the intracellular Ca2+ homeostasis of the parasites while sparing the human hosts. In addition to its inhibitory effects on phosphatidylcholine synthesis and cytochrome c oxidase, miltefosine has been found to affect the unique giant mitochondria and the acidocalcisomes of parasites. Both of these crucial organelles are involved in Ca2+ regulation. Furthermore, miltefosine has the ability to activate a specific parasite Ca2+ channel that responds to sphingosine, which is different to its L-type VGCC human ortholog. Here, we aimed to provide an overview of recent advancements of the anti-parasitic mechanisms of miltefosine. We also explored its multiple molecular targets and investigated how its pleiotropic effects translate into a rational therapeutic approach for patients afflicted by Leishmaniasis and American Trypanosomiasis. Notably, miltefosine's therapeutic effect extends beyond its impact on the parasite to also positively affect the host's immune system. These findings enhance our understanding on its multi-targeted mechanism of action. Overall, this review sheds light on the intricate molecular actions of miltefosine, highlighting its potential as a promising therapeutic option against these debilitating parasitic diseases.

Nanoparticle-Terpene Fusion: A Game-Changer in Combating Primary Amoebic Meningoencephalitis Caused by Naegleria fowleri

Pathogenic Naegleria fowleri (N. fowleri) are opportunistic free-living amoebae and are the causative agents of a very rare but severe brain infection called primary amoebic meningoencephalitis (PAM). The fatality rate of PAM in reported cases is more than 95%. Most of the drugs used againstN. fowleri infections are repurposed drugs. Therefore, a large number of compounds have been tested againstN. fowleri in vitro, but most of the tested compounds showed high toxicity and an inability to cross the blood-brain barrier. Andrographolide, forskolin, and borneol are important natural compounds that have shown various valuable biological properties. In the present study, the nanoconjugates (AND-AgNPs, BOR-AgNPs, and FOR-AgNPs) of these compounds were synthesized and assessed against both stages (trophozoite and cyst) ofN. fowleri for their antiamoebic and cysticidal potential in vitro. In addition, cytotoxicity and host cell pathogenicity were also evaluated in vitro. FOR-AgNPs were the most potent nanoconjugate and showed potent antiamoebic activity againstN. fowleriwith an IC50 of 26.35 μM. Nanoconjugates FOR-AgNPs, BOR-AgNPs, and AND-AgNPs also significantly inhibit the viability of N. fowleri cysts. Cytotoxicity assessment showed that these nanoconjugates caused minimum damage to human keratinocyte cells (HaCaT cells) at 100 μg/mL, while also effectively reducing the cytopathogenicity of N. fowleri trophozoites to the HaCaT cells. The outcomes of our experiments have unveiled substantial potential for AND-AgNPs, BOR-AgNPs, and FOR-AgNPs in the realm of developing innovative alternative therapeutic agents to combat infections caused by N. fowleri. This study represents a significant step forward in the pursuit of advanced strategies for managing such amoebic infections, laying the foundation for the development of novel and more effective therapeutic modalities in the fight against free-living amoebae.

Discovery of novel diagnostic biomarkers for Sjögren-Larsson syndrome by untargeted lipidomics

AIM

Sjögren-Larsson syndrome (SLS) is a rare neurometabolic disorder that mainly affects brain, eye and skin and is caused by deficiency of fatty aldehyde dehydrogenase. Our recent finding of a profoundly disturbed brain tissue lipidome in SLS prompted us to search for similar biomarkers in plasma as no functional test in blood is available for SLS.

METHODS AND RESULTS

We performed plasma lipidomics and used a newly developed bioinformatics tool to mine the untargeted part of the SLS plasma and brain lipidome to search for SLS biomarkers. Plasma lipidomics showed disturbed ether lipid metabolism in known lipid classes. Untargeted lipidomics of both plasma and brain (white and grey matter) uncovered two new endogenous lipid classes highly elevated in SLS. The first biomarker group were alkylphosphocholines/ethanolamines containing different lengths of alkyl-chains where some alkylphosphocholines were > 600-fold elevated in SLS plasma. The second group of biomarkers were a set of 5 features of unknown structure. Fragmentation studies suggested that they contain ubiquinol and phosphocholine and one feature was also found as a glucuronide conjugate in plasma. The plasma features were highly distinctive for SLS with levels >100-1000-fold the level in controls, if present at all. We speculate on the origin of the alkylphosphocholines/ethanolamines and the nature of the ubiquinol-containing metabolites.

CONCLUSIONS

The metabolites identified in this study represent novel endogenous lipid classes thus far unknown in humans. They represent the first plasma metabolite SLS-biomarkers and may also yield more insight into SLS pathophysiology.

Exploring microalgal and cyanobacterial metabolites with antiprotozoal activity against Leishmania and Trypanosoma parasites

Neglected tropical diseases (NTD) like Leishmaniasis and trypanosomiasis affect millions of people annually, while currently used antiprotozoal drugs have serious side effects. Drug research based on natural products has shown that microalgae and cyanobacteria are a promising platform of biochemically active compounds with antiprotozoal activity. These unicellular photosynthetic organisms are rich in polyunsaturated fatty acids, pigments including phycocyanin, chlorophylls and carotenoids, polyphenols, bioactive peptides, terpenes, alkaloids, which have proven antioxidant, antimicrobial, antiviral, antiplasmodial and antiprotozoal properties. This review provides up-to-date information regarding ongoing studies on substances synthesized by microalgae and cyanobacteria with notable activity against Leishmania spp., Trypanosoma cruzi, and Trypanosoma brucei, the causative agents of Leishmaniasis, Chagas disease, and human African trypanosomiasis, respectively. Extracts of several freshwater or marine microalgae have been tested on different strains of Leishmania and Trypanosoma parasites. For instance, ethanolic extract of Chlamydomonas reinhardtii and Tetraselmis suecica have biological activity against T. cruzi, due to their high content of carotenoids, chlorophylls, phenolic compounds and flavonoids that are associated with trypanocidal activity. Halophilic Dunaliella salina showed moderate antileishmanial activity that may be attributed to the high β-carotene content in this microalga. Peptides such as almiramides, dragonamides, and herbamide that are biosynthesized by marine cyanobacteria Lyngbya majuscula were found to have increased activity in micromolar scale IC50 against L. donovani, T. Cruzi, and T. brucei parasites. The cyanobacterial peptides symplocamide and venturamide isolated from Symploca and Oscillatoria species, respectively, and the alkaloid nostocarbonile isolated from Nostoc have shown promising antiprotozoal properties and are being explored for pharmaceutical and medicinal purposes. The discovery of new molecules from microalgae and cyanobacteria with therapeutic potential against Leishmaniasis and trypanosomiasis may address an urgent medical need: effective and safe treatments of NTDs.

Cocrystals of a coumarin derivative: an efficient approach towards anti-leishmanial cocrystals against MIL-resistant Leishmania tropica

Leishmaniasis is a neglected parasitic tropical disease with numerous clinical manifestations. One of the causative agents of cutaneous leishmaniasis (CL) is Leishmania tropica (L. tropica) known for causing ulcerative lesions on the skin. The adverse effects of the recommended available drugs, such as amphotericin B and pentavalent antimonial, and the emergence of drug resistance in parasites, mean the search for new safe and effective anti-leishmanial agents is crucial. Miltefosine (MIL) was the first recommended oral medication, but its use is now limited because of the rapid emergence of resistance. Pharmaceutical cocrystallization is an effective method to improve the physicochemical and biological properties of active pharmaceutical ingredients (APIs). Herein, we describe the cocrystallization of coumarin-3-carboxylic acid (CU, 1a; 2-oxobenzopyrane-3-carboxylic acid, C10H6O4) with five coformers [2-amino-3-bromopyridine (1b), 2-amino-5-(trifluoromethyl)-pyridine (1c), 2-amino-6-methylpyridine (1d), p-aminobenzoic acid (1e) and amitrole (1f)] in a 1:1 stoichiometric ratio via the neat grinding method. The cocrystals 2-6 obtained were characterized via single-crystal X-ray diffraction, powder X-ray diffraction, differential scanning calorimetry and thermogravimetric analysis, as well as Fourier transform infrared spectroscopy. Non-covalent interactions, such as van der Waals, hydrogen bonding, C-H...π and π...π interactions contribute significantly towards the packing of a crystal structure and alter the physicochemical and biological activity of CU. In this research, newly synthesized cocrystals were evaluated for their anti-leishmanial activity against the MIL-resistant L. tropica and cytotoxicity against the 3T3 (normal fibroblast) cell line. Among the non-cytotoxic cocrystals synthesized (2-6), CU:1b (2, IC50 = 61.83 ± 0.59 µM), CU:1c (3, 125.7 ± 1.15 µM) and CU:1d (4, 48.71 ± 0.75 µM) appeared to be potent anti-leishmanial agents and showed several-fold more anti-leishmanial potential than the tested standard drug (MIL, IC50 = 169.55 ± 0.078 µM). The results indicate that cocrystals 2-4 are promising anti-leishmanial agents which require further exploration.

Miltefosine reduces coxsackievirus B3 lethality of mice with enhanced STAT3 activation

Coxsackievirus B3 (CVB3), one serotype of enteroviruses, can induce fatal myocarditis and hepatitis in neonates, but both treatment and vaccine are unavailable. Few reports tested antivirals to reduce CVB3. Several antivirals were developed against other enterovirus serotypes, but these antivirals failed in clinical trials due to side effects and drug resistance. Repurposing of clinical drugs targeting cellular factors, which enhance viral replication, may be another option. Parasite and cancer studies showed that the cellular protein kinase B (Akt) decreases interferon (IFN), apoptosis, and interleukin (IL)-6-induced STAT3 responses, which suppress CVB3 replication. Furthermore, miltefosine, the Akt inhibitor used in the clinic for parasite infections, enhances IL-6, IFN, and apoptosis responses in treated patients, suggesting that miltefosine could be the potential antiviral for CVB3. This study was therefore designated to test the antiviral effects of miltefosine against CVB3 in vitro and especially, in mice, as few studies test miltefosine in vitro, but not in vivo. In vitro results showed that miltefosine inhibited viral replication with enhanced activation of the cellular transcription factor, STAT3, which is reported to reduce CVB3 both in vitro and in mice. Notably, STAT3 knockdown abolished the anti-CVB3 activity of miltefosine in vitro. Mouse studies demonstrated that miltefosine pretreatment reduced CVB3 lethality of mice with decreased virus loads, organ damage, and apoptosis, but enhanced STAT3 activation. Miltefosine could be prophylaxis for CVB3 by targeting Akt to enhance STAT3 activation in the mechanism, which is independent of IFN responses and hardly reported in pathogen infections.

Milteforan, a promising veterinary commercial product against feline sporotrichosis

Sporotrichosis, the cutaneous mycosis most commonly reported in Latin America, is caused by the Sporothrix clinical clade species, including Sporothrix brasiliensis and Sporothrix schenckii sensu stricto. In Brazil, S. brasiliensis represents a vital health threat to humans and domestic animals due to its zoonotic transmission. Itraconazole, terbinafine, and amphotericin B are the most used antifungals for treating sporotrichosis. However, many strains of S. brasiliensis and S. schenckii have shown resistance to these agents, highlighting the importance of finding new therapeutic options. Here, we demonstrate that milteforan, a commercial veterinary product against dog leishmaniasis whose active principle is miltefosine, is a possible therapeutic alternative for the treatment of sporotrichosis, as observed by its fungicidal activity in vitro against different strains of S. brasiliensis and S. schenckii, and by its antifungal activity when used to treat infected epithelial cells and macrophages. Our results suggest milteforan as a possible alternative to treat feline sporotrichosis.

Review of Leishmaniasis Treatment: Can We See the Forest through the Trees?

There are three known clinical syndromes of leishmaniasis: cutaneous (CL), mucocutaneous (MCL), and visceral disease (VL). In MCL and VL, treatment must be systemic (either oral or intravenous), while CL treatment options vary and include observation-only localized/topical treatment, oral medications, or parenteral drugs. Leishmaniasis treatment is difficult, with several factors to be considered. First, the efficacy of treatments varies among different species of parasites prevalent in different areas on the globe, with each species having a unique clinical presentation and resistance profile. Furthermore, leishmaniasis is a neglected tropical disease (NTD), resulting in a lack of evidence-based knowledge regarding treatment. Therefore, physicians often rely on case reports or case series studies, in the absence of randomized controlled trials (RCT), to assess treatment efficacy. Second, defining cure, especially in CL and MCL, may be difficult, as death of the parasite can be achieved in most cases, while the aesthetic result (e.g., scars) is hard to predict. This is a result of the biological nature of the disease, often diagnosed late in the course of disease (with possible keloid formation, etc.). Third, physicians must consider treatment ease of use and the safety profile of possible treatments. Thus, topical or oral treatments (for CL) are desirable and promote adherence. Fourth, the cost of the treatment is an important consideration. In this review, we aim to describe the diverse treatment options for different clinical manifestations of leishmaniasis. For each currently available treatment, we will discuss the various considerations mentioned above (efficacy, ease of use, safety, and cost).

Design of Liquid Formulation Based on F127-Loaded Natural Dimeric Flavonoids as a New Perspective Treatment for Leishmaniasis

Infectious and Parasitic Diseases (IPD) remain a challenge for medicine due to several interconnected reasons, such as antimicrobial resistance (AMR). American tegumentary leishmaniasis (ATL) is an overlooked IPD causing persistent skin ulcers that are challenging to heal, resulting in disfiguring scars. Moreover, it has the potential to extend from the skin to the mucous membranes of the nose, mouth, and throat in both humans and various animals. Given the limited effectiveness and AMR of current drugs, the exploration of new substances has emerged as a promising alternative for ATL treatment. Arrabidaea brachypoda (DC). Bureau is a native Brazilian plant rich in dimeric flavonoids, including Brachydin (BRA), which displays antimicrobial activity, but still little has been explored regarding the development of therapeutic formulations. In this work, we present the design of a low-cost liquid formulation based on the use of Pluronic F127 for encapsulation of high BRA concentration (LF-B500). The characterization techniques revealed that BRA-loaded F127 micelles are well-stabilized in an unusual worm-like form. The in vitro cytotoxicity assay demonstrated that LF-B500 was non-toxic to macrophages but efficient in the inactivation of forms of Leishmania amazonensis promastigotes with IC50 of 16.06 µg/mL. The results demonstrated that LF-B500 opened a new perspective on the use of liquid formulation-based natural products for ATL treatment.

Designer phospholipid capping ligands for soft metal halide nanocrystals

The success of colloidal semiconductor nanocrystals (NCs) in science and optoelectronics is inextricable from their surfaces. The functionalization of lead halide perovskite NCs1-5 poses a formidable challenge because of their structural lability, unlike the well-established covalent ligand capping of conventional semiconductor NCs6,7. We posited that the vast and facile molecular engineering of phospholipids as zwitterionic surfactants can deliver highly customized surface chemistries for metal halide NCs. Molecular dynamics simulations implied that ligand-NC surface affinity is primarily governed by the structure of the zwitterionic head group, particularly by the geometric fitness of the anionic and cationic moieties into the surface lattice sites, as corroborated by the nuclear magnetic resonance and Fourier-transform infrared spectroscopy data. Lattice-matched primary-ammonium phospholipids enhance the structural and colloidal integrity of hybrid organic-inorganic lead halide perovskites (FAPbBr3 and MAPbBr3 (FA, formamidinium; MA, methylammonium)) and lead-free metal halide NCs. The molecular structure of the organic ligand tail governs the long-term colloidal stability and compatibility with solvents of diverse polarity, from hydrocarbons to acetone and alcohols. These NCs exhibit photoluminescence quantum yield of more than 96% in solution and solids and minimal photoluminescence intermittency at the single particle level with an average ON fraction as high as 94%, as well as bright and high-purity (about 95%) single-photon emission.

Activity of the Di-Substituted Urea-Derived Compound I-17 in Leishmania In Vitro Infections

Protein synthesis has been a very rich target for developing drugs to control prokaryotic and eukaryotic pathogens. Despite the development of new drug formulations, treating human cutaneous and visceral Leishmaniasis still needs significant improvements due to the considerable side effects and low adherence associated with the current treatment regimen. In this work, we show that the di-substituted urea-derived compounds I-17 and 3m are effective in inhibiting the promastigote growth of different Leishmania species and reducing the macrophage intracellular load of amastigotes of the Leishmania (L.) amazonensis and L. major species, in addition to exhibiting low macrophage cytotoxicity. We also show a potential immunomodulatory effect of I-17 and 3m in infected macrophages, which exhibited increased expression of inducible Nitric Oxide Synthase (NOS2) and production of Nitric Oxide (NO). Our data indicate that I-17, 3m, and their analogs may be helpful in developing new drugs for treating leishmaniasis.

Primary amebic meningoencephalitis: a review of Naegleria fowleri and analysis of successfully treated cases

Primary amebic meningoencephalitis (PAM) is a necrotizing and hemorrhagic inflammation of the brain and meninges caused by Naegleria fowleri, a free-living thermophilic ameba of freshwater systems. PAM remains a neglected disease that disproportionately affects children in tropical and subtropical climates, with an estimated mortality rate of 95-98%. Due to anthropogenic climate change, the average temperature in the USA has increased by 0.72 to 1.06 °C in the last century, promoting the poleward spread of N. fowleri. PAM is often misdiagnosed as bacterial meningitis or viral encephalitis, which shortens the window for potentially life-saving treatment. Diagnosis relies on the patient's history of freshwater exposure and the physician's high index of suspicion, supported by cerebrospinal fluid studies. While no experimental trials have been conducted to assess the relative efficacy of treatment regimens, anti-amebic therapy with adjunctive neuroprotection is standard treatment in the USA. We performed a literature review and identified five patients from North America between 1962 and 2022 who survived PAM with various degrees of sequelae.

Effectiveness In Vivo and In Vitro of Polymeric Nanoparticles as a Drug Release System in the Treatment of Leishmaniasis

Leishmaniasis is a neglected disease caused by the parasite of the genus Leishmania. Current treatment regimens are obsolete and cause several side effects, promoting poor patient compliance, in addition to the vast majority already having the potential for resistance. Therefore, polymeric nanoparticles emerge as one of the viable alternatives to overcome existing limitations, through passive or active vectorization. This review aims to summarize the latest studies of polymeric nanoparticles as an alternative treatment for leishmaniasis. In the first section, the main pharmacokinetic and pharmacodynamic challenges of current drugs are reported. The second section details how nanoparticles with and without functionalization are efficient in the treatment of leishmaniasis, discussing the characteristics of the polymer in the formulation. In this way, polymeric nanoparticles can improve the physicochemical properties of leishmanicidal drugs, improving solubility and stability, as well as improve the release of these drugs, directly or indirectly reaching monocytes/macrophages. 64.28% drugs were focused on the treatment of visceral leishmaniasis, and 28.57% on cutaneous leishmaniasis. The most chosen polymers in the literature are chitosan (35.71%) and PLGA (35.71%), the others represented 14.30% drugs, with all able to manage the drug release and increase the in vitro and/or in vivo efficacy of the original molecule. However, there are several barriers for these nanoformulations to cross laboratory research and is necessary more in-depth studies about the metabolites and degradation pathways of the polymers used in the formulations and plasma proteomics studies.

Miltefosine: A Repurposing Drug against Mucorales Pathogens

Mucorales are a group of non-septated filamentous fungi widely distributed in nature, frequently associated with human infections, and are intrinsically resistant to many antifungal drugs. For these reasons, there is an urgent need to improve the clinical management of mucormycosis. Miltefosine, which is a phospholipid analogue of alkylphosphocholine, has been considered a promising repurposing drug to be used to treat fungal infections. In the present study, miltefosine displayed antifungal activity against a variety of Mucorales species, and it was also active against biofilms formed by these fungi. Treatment with miltefosine revealed modifications of cell wall components, neutral lipids, mitochondrial membrane potential, cell morphology, and the induction of oxidative stress. Treated Mucorales cells also presented an increased susceptibility to SDS. Purified ergosterol and glucosylceramide added to the culture medium increased miltefosine MIC, suggesting its interaction with fungal lipids. These data contribute to elucidating the effect of a promising drug repurposed to act against some relevant fungal pathogens that significantly impact public health.

In vitro susceptibility to miltefosine of amphotericin B-resistant Leishmania (Mundinia) martiniquensis

Leishmania (Mundinia) martiniquensis is a newly described species that causes human visceral, disseminated, and mucocutaneous leishmaniases. Amphotericin B deoxycholate (AmpB) is the first-line drug for the treatment of leishmaniasis in Thailand; however, several relapse cases of leishmaniasis caused by L. martiniquensis have been documented. In this study, in vitro susceptibility to AmpB and miltefosine (MIL) of wild-type (before treatment, LSCM1) and two AmpB-resistant L. martiniquensis strains (an in vitro-induced AmpB-resistant strain, AmpBRP2i, and a relapse strain, LSCM1-6) were determined. Results reveal that the IC50 value and resistance index against both drugs of promastigotes and intracellular amastigotes of the AmpBRP2i and LSCM1-6 strains were statistically significantly higher than those of the LSCM1 strain suggesting that cross-resistance with MIL occurred in both AmpB-resistant strains. The results of this study advocate further investigation into mechanisms that involve the complex nature of AmpB/MIL resistance in L. martiniquensis and development of effective methods for the identification of the AmpB-resistant parasites to help delivery of appropriate treatments for patients and for epidemiological surveys to survey the potential spread of drug-resistant strains.

Repurposing of conformationally-restricted cyclopentane-based AKT-inhibitors leads to discovery of potential and more selective antileishmanial agents than miltefosine

Conformational restriction was addressed towards the development of more selective and effective antileishmanial agents than currently used drugs for treatment of Leishmania donovani; the causative parasite of the fatal visceral leishmaniasis. Five types of cyclopentane-based conformationally restricted miltefosine analogs that were previously explored in literature as anticancer AKT-inhibitors were reprepared and repurposed as antileishmanial agents. Amongst, positions-1 and 2 cis-conformationally-restricted compound 1a and positions-2 and 3 trans-conformationally-restricted compound 3b were highly potent eliciting sub-micromolar IC50 values for inhibition of infection and inhibition of parasite number compared with the currently used miltefosine drug that showed low micromolar IC50 values for inhibition of infection and inhibition of parasite number. Compounds 1a and 3b eradicated the parasite without triggering host cells cytotoxicity over more than one log concentration interval which is a superior performance compared to miltefosine. In silico studies suggested that conformational restriction conserved the conformer capable of binding LdAKT-like kinase while it might be possible that it excludes other conformers mediating undesirable effects and/or toxicity of miltefosine. Together, this study presents compounds 1a and 3b as antileishmanial agents with superior performance over the currently used miltefosine drug.

Assessing Dose-Exposure-Response Relationships of Miltefosine in Adults and Children using Physiologically-Based Pharmacokinetic Modeling Approach

OBJECTIVES

Miltefosine is the first and only oral medication to be successfully utilized as an antileishmanial agent. However, the drug is associated with differences in exposure patterns and cure rates among different population groups e.g. ethnicity and age (i.e., children v adults) in clinical trials. In this work, mechanistic population physiologically-based pharmacokinetic (PBPK) models have been developed to study the dose-exposure-response relationship of miltefosine in in silico clinical trials and evaluate the differences in population groups, particularly children and adults.

METHODS

The Simcyp population pharmacokinetics platform was employed to predict miltefosine exposure in plasma and peripheral blood mononuclear cells (PBMCs) in a virtual population under different dosing regimens. The cure rate of a simulation was based on the percentage of number of the individual virtual subjects with AUCd0-28 > 535 µg⋅day/mL in the virtual population.

RESULTS

It is shown that both adult and paediatric PBPK models of miltefosine can be developed to predict the PK data of the clinical trials accurately. There was no significant difference in the predicted dose-exposure-response of the miltefosine treatment for different simulated ethnicities under the same dose regime and the dose-selection strategies determined the clinical outcome of the miltefosine treatment. A lower cure rate of the miltefosine treatment in paediatrics was predicted because a lower exposure of miltefosine was simulated in virtual paediatric in comparison with adult virtual populations when they received the same dose of the treatment.

CONCLUSIONS

The mechanistic PBPK model suggested that the higher fraction of unbound miltefosine in plasma was responsible for a higher probability of failure in paediatrics because of the difference in the distribution of plasma proteins between adults and paediatrics. The developed PBPK models could be used to determine an optimal miltefosine dose regime in future clinical trials.

In Silico Exploration of the Trypanothione Reductase (TryR) of L. mexicana

Human leishmaniasis is a neglected tropical disease which affects nearly 1.5 million people every year, with Mexico being an important endemic region. One of the major defense mechanisms of these parasites is based in the polyamine metabolic pathway, as it provides the necessary compounds for its survival. Among the enzymes in this route, trypanothione reductase (TryR), an oxidoreductase enzyme, is crucial for the Leishmania genus' survival against oxidative stress. Thus, it poses as an attractive drug target, yet due to the size and features of its catalytic pocket, modeling techniques such as molecular docking focusing on that region is not convenient. Herein, we present a computational study using several structure-based approaches to assess the druggability of TryR from L. mexicana, the predominant Leishmania species in Mexico, beyond its catalytic site. Using this consensus methodology, three relevant pockets were found, of which the one we call σ-site promises to be the most favorable one. These findings may help the design of new drugs of trypanothione-related diseases.

Miltefosine repositioning: A review of potential alternative antifungal therapy

Fungal infections are a global health problem with high mortality and morbidity rates. Available antifungal agents have high toxicity and pharmacodynamic and pharmacokinetic limitations. Moreover, the increased incidence of antifungal-resistant isolates and the emergence of intrinsically resistant species raise concerns about seeking alternatives for efficient antifungal therapy. In this context, we review literature data addressing the potential action of miltefosine (MFS), an anti-Leishmania and anticancer agent, as a repositioning drug for antifungal treatment. Here, we highlight the in vitro and in vivo data, MFS possible mechanisms of action, case reports, and nanocarrier-mediated MFS delivery, focusing on fungal infection therapy. Finally, many studies have demonstrated the promising antifungal action of MFS in vitro, but there is little or no data on antifungal activity in vertebrate animal models and clinical trials, so have a need to develop more research for the repositioning of MFS as an antifungal therapy.

Safety and efficacy of paromomycin/miltefosine/liposomal amphotericin B combinations for the treatment of post-kala-azar dermal leishmaniasis in Sudan: A phase II, open label, randomized, parallel arm study

BACKGROUND

Treatment for post-kala-azar dermal leishmaniasis (PKDL) in Sudan is currently recommended only for patients with persistent or severe disease, mainly because of the limitations of current therapies, namely toxicity and long hospitalization. We assessed the safety and efficacy of miltefosine combined with paromomycin and liposomal amphotericin B (LAmB) for the treatment of PKDL in Sudan.

METHODOLOGY/PRINCIPAL FINDINGS

An open-label, phase II, randomized, parallel-arm, non-comparative trial was conducted in patients with persistent (stable or progressive disease for ≥ 6 months) or grade 3 PKDL, aged 6 to ≤ 60 years in Sudan. The median age was 9.0 years (IQR 7.0-10.0y) and 87% of patients were ≤12 years old. Patients were randomly assigned to either daily intra-muscular paromomycin (20mg/kg, 14 days) plus oral miltefosine (allometric dose, 42 days)-PM/MF-or LAmB (total dose of 20mg/kg, administered in four injections in week one) and oral miltefosine (allometric dose, 28 days)-LAmB/MF. The primary endpoint was a definitive cure at 12 months after treatment onset, defined as clinical cure (100% lesion resolution) and no additional PKDL treatment between end of therapy and 12-month follow-up assessment. 104/110 patients completed the trial. Definitive cure at 12 months was achieved in 54/55 (98.2%, 95% CI 90.3-100) and 44/55 (80.0%, 95% CI 70.2-91.9) of patients in the PM/MF and AmB/MF arms, respectively, in the mITT set (all randomized patients receiving at least one dose of treatment; in case of error of treatment allocation, the actual treatment received was used in the analysis). No SAEs or deaths were reported, and most AEs were mild or moderate. At least one adverse drug reaction (ADR) was reported in 13/55 (23.6%) patients in PM/MF arm and 28/55 (50.9%) in LAmB/MF arm, the most frequent being miltefosine-related vomiting and nausea, and LAmB-related hypokalaemia; no ocular or auditory ADRs were reported.

CONCLUSIONS/SIGNIFICANCE

The PM/MF regimen requires shorter hospitalization than the currently recommended 60-90-day treatment, and is safe and highly efficacious, even for patients with moderate and severe PKDL. It can be administered at primary health care facilities, with LAmB/MF as a good alternative. For future VL elimination, we need new, safe oral therapies for all patients with PKDL.

TRIAL REGISTRATION

ClinicalTrials.gov NCT03399955, https://clinicaltrials.gov/study/NCT03399955 ClinicalTrials.gov ClinicalTrials.gov.

Structure and dynamics of pteridine reductase 1: the key phenomena relevant to enzyme function and drug design

Pteridine reductase 1 (PTR1) is a folate and pterin pathway enzyme unique for pathogenic trypanosomatids. As a validated drug target, PTR1 has been the focus of recent research efforts aimed at finding more effective treatments against human parasitic diseases such as leishmaniasis or sleeping sickness. Previous PTR1-centered structural studies highlighted the enzyme characteristics, such as flexible regions around the active site, highly conserved structural waters, and species-specific differences in pocket properties and dynamics, which likely impacts the binding of natural substrates and inhibitors. Furthermore, several aspects of the PTR1 function, such as the substrate inhibition phenomenon and the level of ligand binding cooperativity in the enzyme homotetramer, likely related to the global enzyme dynamics, are poorly known at the molecular level. We postulate that future drug design efforts could greatly benefit from a better understanding of these phenomena through studying both the local and global PTR1 dynamics. This review highlights the key aspects of the PTR1 structure and dynamics relevant to structure-based drug design that could be effectively investigated by modeling approaches. Particular emphasis is given to the perspective of molecular dynamics, what has been accomplished in this area to date, and how modeling could impact the PTR1-targeted drug design in the future.

Synthesis of ether lipids: natural compounds and analogues

Ether lipids are compounds present in many living organisms including humans that feature an ether bond linkage at the sn-1 position of the glycerol. This class of lipids features singular structural roles and biological functions. Alkyl ether lipids and alkenyl ether lipids (also identified as plasmalogens) correspond to the two sub-classes of naturally occurring ether lipids. In 1979 the discovery of the structure of the platelet-activating factor (PAF) that belongs to the alkyl ether class of lipids increased the interest in these bioactive lipids and further promoted the synthesis of non-natural ether lipids that was initiated in the late 60's with the development of edelfosine (an anticancer drug). More recently, ohmline, a glyco glycero ether lipid that modulates selectively SK3 ion channels and reduces in vivo the occurrence of bone metastases, and other glyco glycero ether also identified as GAEL (glycosylated antitumor ether lipids) that exhibit promising anticancer properties renew the interest in this class of compounds. Indeed, ether lipid represent a new and promising class of compounds featuring the capacity to modulate selectively the activity of some membrane proteins or, for other compounds, feature antiproliferative properties via an original mechanism of action. The increasing interest in studying ether lipids for fundamental and applied researches invited to review the methodologies developed to prepare ether lipids. In this review we focus on the synthetic method used for the preparation of alkyl ether lipids either naturally occurring ether lipids (e.g., PAF) or synthetic derivatives that were developed to study their biological properties. The synthesis of neutral or charged ether lipids are reported with the aim to assemble in this review the most frequently used methodologies to prepare this specific class of compounds.

The adaptive roles of aneuploidy and polyclonality in Leishmania in response to environmental stress

Aneuploidy is generally considered harmful, but in some microorganisms, it can act as an adaptive mechanism against environmental stress. Here, we use Leishmania-a protozoan parasite with remarkable genome plasticity-to study the early steps of aneuploidy evolution under high drug pressure (using antimony or miltefosine as stressors). By combining single-cell genomics, lineage tracing with cellular barcodes, and longitudinal genome characterization, we reveal that aneuploidy changes under antimony pressure result from polyclonal selection of pre-existing karyotypes, complemented by further and rapid de novo alterations in chromosome copy number along evolution. In the case of miltefosine, early parasite adaptation is associated with independent point mutations in a miltefosine transporter gene, while aneuploidy changes only emerge later, upon exposure to increased drug levels. Therefore, polyclonality and genome plasticity are hallmarks of parasite adaptation, but the scenario of aneuploidy dynamics depends on the nature and strength of the environmental stress as well as on the existence of other pre-adaptive mechanisms.

Design, synthesis and biological evaluation of antiparasitic dinitroaniline-ether phospholipid hybrids

A series of nine novel ether phospholipid-dinitroaniline hybrids were synthesized in an effort to deliver more potent antiparasitic agents with improved safety profile compared to miltefosine. The compounds were evaluated for their in vitro antiparasitic activity against L. infantum, L.donovani, L. amazonensis, L. major and L. tropica promastigotes, L. infantum and L. donovani intracellular amastigotes, Trypanosoma brucei brucei and against different developmental stages of Trypanosoma cruzi. The nature of the oligomethylene spacer between the dinitroaniline moiety and the phosphate group, the length of the side chain substituent on the dinitroaniline and the choline or homocholine head group were found to affect both the activity and toxicity of the hybrids. The early ADMET profile of the derivatives did not reveal major liabilities. Hybrid 3, bearing an 11-carbon oligomethylene spacer, a butyl side chain and a choline head group, was the most potent analogue of the series. It exhibited a broad spectrum antiparasitic profile against the promastigotes of New and Old World Leishmania spp., against intracellular amastigotes of two L. infantum strains and L. donovani, against T. brucei and against T. cruzi Y strain epimastigotes, intracellular amastigotes and trypomastigotes. The early toxicity studies revealed that hybrid 3 showed a safe toxicological profile while its cytotoxicity concentration (CC50) against THP-1 macrophages being >100 μM. Computational analysis of binding sites and docking indicated that the interaction of hybrid 3 with trypanosomatid α-tubulin may contribute to its mechanism of action. Furthermore, compound 3 was found to interfere with the cell cycle in T. cruzi epimastigotes, while ultrastructural studies using SEM and TEM in T. cruzi showed that compound 3 affects cellular processes that result in changes in the Golgi complex, the mitochondria and the parasite's plasma membrane. The snapshot pharmacokinetic studies showed low levels of 3 after 24 h following oral administration of 100 mg/Kg, while, its homocholine congener compound 9 presented a better pharmacokinetic profile.

Synthesis of 1,2,3-Triazole-Containing Methoxylated Cinnamides and Their Antileishmanial Activity against the Leishmania braziliensis Species

Leishmaniasis is a group of infectious diseases caused by protozoan parasites that belong to the genus Leishmania. Currently, there is no human vaccine, and the available treatments are associated with toxicity, high cost, and the emergence of resistant strains. These factors highlight the need to identify new antileishmanial candidates. In this study, we synthesized twenty-four methoxylated cinnamides containing 1,2,3-triazole fragments and evaluated their antileishmanial activity against the Leishmania braziliensis species, which is the main etiological agent responsible for American Tegumentary Leishmaniasis (ATL). The cinnamides were synthetically prepared using nucleophilic acyl substitution and copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) reactions. The compounds were characterized using infrared, nuclear magnetic resonance, and high-resolution mass spectrometry techniques. We performed preliminary studies to evaluate the biological activity of these compounds against L. braziliensis promastigotes and axenic amastigotes. Compound 28, N-((1-(7-(diethylamino)-2-oxo-2H-chromen-3-yl)-1H-1,2,3-triazole-4-yl) methyl)-3,4-dimethoxy cinnamide, demonstrated relevant antileishmanial activity with low toxicity in murine cells. The selectivity index values for this compound were superior compared with data obtained using amphotericin B. Furthermore, this cinnamide derivative reduced the infection percentage and number of recovered amastigotes in L. braziliensis-infected macrophages. It also induced an increase in reactive oxygen species production, depolarization of the mitochondrial potential, and disruption of the parasite membrane. Taken together, these findings suggest that this synthetic compound holds potential as an antileishmanial candidate and should be considered for future studies in the treatment of ATL.

Field-Deployable Treatments For Leishmaniasis: Intrinsic Challenges, Recent Developments and Next Steps

Leishmaniasis is a neglected tropical disease endemic primarily to low- and middle-income countries, for which there has been inadequate development of affordable, safe, and efficacious therapies. Clinical manifestations of leishmaniasis range from self-healing skin lesions to lethal visceral infection with chances of relapse. Although treatments are available, secondary effects limit their use outside the clinic and negatively impact the quality of life of patients in endemic areas. Other non-medicinal treatments, such as thermotherapies, are limited to use in patients with cutaneous leishmaniasis but not with visceral infection. Recent studies shed light to mechanisms through which Leishmania can persist by hiding in cellular safe havens, even after chemotherapies. This review focuses on exploring the cellular niches that Leishmania parasites may be leveraging to persist within the host. Also, the cellular, metabolic, and molecular implications of Leishmania infection and how those could be targeted for therapeutic purposes are discussed. Other therapies, such as those developed against cancer or for manipulation of the ferroptosis pathway, are proposed as possible treatments against leishmaniasis due to their mechanisms of action. In particular, treatments that target hematopoietic stem cells and monocytes, which have recently been found to be necessary components to sustain the infection and provide a safe niche for the parasites are discussed in this review as potential field-deployable treatments against leishmaniasis.

The role of natural anti-parasitic guided development of synthetic drugs for leishmaniasis

Leishmaniasis is a parasitic disease and categorised as a neglected tropical disease (NTD). Each year, between 70,0000 and 1 million new cases are believed to occur. There are approximately 90 sandfly species which can spread the Leishmania parasites (over 20 species) causing 20,000 to 30,000 death per year. Currently, leishmaniasis has no specific therapeutic treatment available. The prescribed drugs with several drawbacks including high cost, challenging administration, toxicity, and drug resistance led to search for the alternative treatment with less toxicity and selectivity. Introducing the molecular features like that of phytoconstituents for the search of compounds with less toxicity is another promising approach. The current review classifies the synthetic compounds according to the core rings present in the natural phytochemicals for the development of antileishmanial agents (2020-2022). Considering the toxicity and limitations of synthetic analogues, natural compounds are at the higher notch in terms of effectiveness and safety. Synthesized compounds of chalcones (Compound 8; IC₅₀: 0.03 μM, 4.7 folds more potent than Amphotericin B; IC₅₀: 0.14 μM), pyrimidine (compound 56; against L. tropica; 0.04 μM and L. infantum; 0.042 μM as compared to glucantime: L. tropica; 8.17 μM and L. infantum; 8.42 μM), quinazoline and (compound 72; 0.021 μM, 150 times more potent than miltefosine). The targeted delivery against DHFR have been demonstrated by one of the pyrimidine compounds 62 with an IC₅₀ value of 0.10 μM against L. major as compared to the standard trimethoprim (IC₅₀: 20 μM). The review covers the medicinal importance of antileishmanial agents from synthetic and natural sources such as chalcone, pyrazole, coumarins, steroids, and alkaloidal-containing drugs (indole, quinolines, pyridine, pyrimidine, carbolines, pyrrole, aurones, and quinazolines). The efforts of introducing the core rings present in the natural phytoconstituents as antileishmanial in the synthetic compounds are discussed with their structural activity relationship. The perspective will support the medicinal chemists in refining and directing the development of novel molecules phytochemicals-based antileishmanial agents.

Antiprotozoal activity of natural products from Nigerien plants used in folk medicine

In the course of the screening of plants from Niger for antiprotozoal activity, the methanol extract of Cassia sieberiana, and the dichloromethane extracts of Ziziphus mauritiana and Sesamun alatum were found to be active against protozoan parasites, namely Trypanosoma brucei rhodesiense, Trypanosoma cruzi, Leishmania donovani and/or Plasmodium falciparum. Myricitrin (1), quercitrin (2) and 1-palmitoyl-lysolecithin (3) were isolated from C. sieberiana. From Z. mauritiana, the three triterpene derivatives 13, 15, and 16 are described here for the first time. Their chemical structures were determined by 1D and 2D NMR experiments, UV, IR and HRESIMS data. The absolute configurations were assigned via comparison of the experimental and calculated ECD spectra. In addition, eight known cyclopeptide alkaloids (4, 5, 7-12), and five known triterpenoids (6, 14, 17-19) were isolated. The antiprotozoal activity of the isolated compounds, as well as of eleven quinone derivatives (20-30) previously isolated from S. alatum was determined in vitro. The cytotoxicity in L6 rat myoblast cells was also evaluated. Compound 18 showed the highest antiplasmodial activity (IC₅₀ = 0.2 µm) and compound 24 inhibited T. b. rhodesiense with an IC₅₀ value of 0.007 µM. However, it also displayed significant cytotoxicity in L6 cells (IC₅₀ = 0.4 µm).

Retrospective Long-Term Evaluation of Miltefosine-Allopurinol Treatment in Canine Leishmaniosis

Miltefosine-Allopurinol (MIL-AL) combination is reported to be one of the most effective treatments for canine leishmaniosis, thanks to its oral administration and MIL-documented low impact on renal function. However, MIL-AL is considered a second-choice treatment when compared to meglumine-antimoniate-allopurinol combination, mainly due to the risk of earlier relapses. The aim of this study was to evaluate the efficacy of the MIL-AL protocol during a long-term follow-up with an average duration of nine years. Dogs were living in Southern Italy (Puglia, Italy) in an area considered endemic for Canine leishmaniosis (CanL). Inclusion criteria were clinical and/or clinicopathological signs consistent with CanL; positive result to Leishmania quantitative ELISA; and negativity to the most frequent canine vector-borne infections. All dogs received 2 mg/kg MIL for 28 days, and 10 mg/kg AL, BID, for a period varying between 2 and 12 months. Ancillary treatments were allowed according to the clinical condition of the dog. A total clinical score and a total clinicopathological score were calculated at each time point by attributing one point to each sign or alteration present and then by adding all points. Improvement after each treatment was defined by the reduction of at least 50% of the total score. A survival analysis (Kaplan-Meier curve) was performed for quantifying the probability of the events occurring during the study follow-up. The following events were considered: decreased and negative ELISA results; improvement/recovery of the clinical and clinicopathological alterations; and relapse of leishmaniasis. One hundred seventy-three dogs (75f and 98m) were retrospectively included in the study by examining their clinical records since the first diagnosis of CanL. One hundred forty-three (83%) dogs were under five years of age. The mean duration of the follow-up period was 5.4 (±1.1) years with a minimum of 3.2 years and a maximum of 9 years. All dogs received a first treatment of MIL-AL at inclusion; then, during the follow-up course, 30 dogs required a second treatment, 2 dogs required a third treatment and 1 dog required a fourth and a fifth treatment. The mean time interval between the first and the second treatment was 27.2 (±18.3) months. After the first treatment, all dogs had decreased ELISA levels, in an average interval of 2.6 (±1.6) months. One hundred seventy dogs (98%) experienced a clinical improvement (mean time 3.0 ± 4.9 months); 152 (88%) dogs were considered clinically recovered after a mean time of 16.7 ± 13.5 months. A similar trend was observed for clinicopathological alterations; interestingly, proteinuria decreased in most dogs (p < 0.0001-Chi-square for trends). Thirty dogs experienced relapses, the earliest after 4.8 months. The mean time without relapse was 90.4 (±2.5) months. In relapsed dogs, the mean time for clinical improvement after the second treatment was 8.6 (±12.6) months, whereas it was 11.0 (±15.4) months for clinicopathological alterations. Five dogs had limited gastrointestinal side effects associated with MIL treatment. The present study confirms that the MIL-AL protocol can be considered one of the most effective treatments for CanL therapy, mainly for its capacity to provide a long-time clinical improvement in a large majority of treated dogs. As reported in the literature, the clinical stabilization of dogs does not occur immediately after treatment, probably due to the particular pharmacokinetic properties of MIL. The efficacy of MIL-AL decreases in dogs that need more than one treatment, suggesting the necessity to alternate anti-Leishmania drugs for the treatment of relapses. Side effects were transient and slight, even in dogs that required several treatments.

Disseminated cutaneous leishmaniasis in a kidney transplant recipient

Key Clinical Message

In this case of disseminated cutaneous leishmaniasis in our immunosuppressive patient who was a refractor to treatment with intra-lesion Glucantime® and systemic L-AmB, considering the good clinical response to oral miltefosine, this drug might be the best treatment option.

Abstract

Diagnosis and treatment of leishmaniasis are challenging in immunosuppressed patients. Here, we report a 46-year-old male renal transplant recipient with disseminated cutaneous leishmaniasis presenting with multiple lesions on the face and upper extremities 15 years after transplant with a challenging course of treatment with meglumine antimoniate, liposomal amphotericin B, and miltefosine.

A short-term method to evaluate anti-leishmania drugs by inhibition of stage differentiation in Leishmania mexicana using flow cytometry

Leishmaniasis is a vector-borne neglected tropical disease caused by the Leishmania spp. Parasite. The disease is transmitted to humans and animals by the bite of infected female sandflies during the ingestion of bloodmeal. Because current drug treatments induce toxicity and parasite resistance, there is an urgent need to evaluate new drugs. Most therapeutics target the differentiation of promastigotes to amastigotes, which is necessary to maintain Leishmania infection. However, in vitro assays are laborious, time-consuming, and depend on the experience of the technician. In this study, we aimed to establish a short-term method to assess the differentiation status of Leishmania mexicana (L. mexicana) using flow cytometry. Here, we showed that flow cytometry provides a rapid means to quantify parasite differentiation in cell culture as reliably as light microscopy. Interestingly, we found using flow cytometry that miltefosine reduced promastigote-to-amastigote differentiation of L. mexicana. We conclude that flow cytometry provides a means to rapidly assay the efficacy of small molecules or natural compounds as potential anti-leishmanials.

Efficacy of oleylphosphocholine in experimental cutaneous leishmaniasis

OBJECTIVES

Cutaneous leishmaniasis (CL) is a neglected tropical disease causing a range of skin lesions for which safe and efficacious drugs are lacking. Oleylphosphocholine (OLPC) is structurally similar to miltefosine and has previously demonstrated potent activity against visceral leishmaniasis. We here present the in vitro and in vivo efficacy of OLPC against CL-causing Leishmania species.

METHODS

The antileishmanial activities of OLPC were evaluated and compared with miltefosine in vitro against intracellular amastigotes of seven CL-causing species. Following the confirmation of significant in vitro activity, the performance of the maximum tolerated dose of OLPC was evaluated in an experimental murine model of CL followed by a dose-response titration and the efficacy evaluation of four OLPC formulations (two with a fast-release and two with a slow-release profile) using bioluminescent Leishmania major parasites.

RESULTS

OLPC demonstrated potent in vitro activity of the same order as miltefosine in the intracellular macrophage model against a range of CL-causing species. A dose of 35 mg of OLPC/kg/day administered orally for 10 days was well-tolerated and able to reduce the parasite load in the skin of L. major-infected mice to a similar extent as the positive control paromomycin (50 mg/kg/day, intraperitoneally) in both in vivo studies. Reducing the dose of OLPC resulted in inactivity and modifying the release profile using mesoporous silica nanoparticles led to a decrease in activity when solvent-based loading was used in contrast to extrusion-based loading, which had no impact on its antileishmanial efficacy.

CONCLUSIONS

Together, these data suggest that OLPC could be a promising alternative to miltefosine treatment for CL. Further investigations exploring experimental models with additional Leishmania species and skin pharmacokinetic and dynamic analyses are required.

Recent Advances in Chemotherapeutics for Leishmaniasis: Importance of the Cellular Biochemistry of the Parasite and Its Molecular Interaction with the Host

Leishmaniasis, a category 1 neglected protozoan disease caused by a kinetoplastid pathogen called Leishmania, is transmitted through dipteran insect vectors (phlebotomine, sand flies) in three main clinical forms: fatal visceral leishmaniasis, self-healing cutaneous leishmaniasis, and mucocutaneous leishmaniasis. Generic pentavalent antimonials have long been the drug of choice against leishmaniasis; however, their success is plagued with limitations such as drug resistance and severe side effects, which makes them redundant as frontline therapy for endemic visceral leishmaniasis. Alternative therapeutic regimens based on amphotericin B, miltefosine, and paromomycin have also been approved. Due to the unavailability of human vaccines, first-line chemotherapies such as pentavalent antimonials, pentamidine, and amphotericin B are the only options to treat infected individuals. The higher toxicity, adverse effects, and perceived cost of these pharmaceutics, coupled with the emergence of parasite resistance and disease relapse, makes it urgent to identify new, rationalized drug targets for the improvement in disease management and palliative care for patients. This has become an emergent need and more relevant due to the lack of information on validated molecular resistance markers for the monitoring and surveillance of changes in drug sensitivity and resistance. The present study reviewed the recent advances in chemotherapeutic regimens by targeting novel drugs using several strategies including bioinformatics to gain new insight into leishmaniasis. Leishmania has unique enzymes and biochemical pathways that are distinct from those of its mammalian hosts. In light of the limited number of available antileishmanial drugs, the identification of novel drug targets and studying the molecular and cellular aspects of these drugs in the parasite and its host is critical to design specific inhibitors targeting and controlling the parasite. The biochemical characterization of unique Leishmania-specific enzymes can be used as tools to read through possible drug targets. In this review, we discuss relevant metabolic pathways and novel drugs that are unique, essential, and linked to the survival of the parasite based on bioinformatics and cellular and biochemical analyses.

High Selectivity of 8-Hydroxyquinoline on Leishmania (Leishmania) and Leishmania (Viannia) Species Correlates with a Potent Therapeutic Activity In Vivo

Leishmaniasis is a neglected disease caused by protozoa of the genus Leishmania, which causes different clinical manifestations. Drugs currently used in the treatment such as pentavalent antimonial and amphotericin B cause severe side effects in patients, and parasite resistance has been reported. Thus, it is necessary and urgent to characterize new and effective alternative drugs to replace the current chemotherapy of leishmaniasis. In this regard, it has been experimentally demonstrated that quinoline derivatives present significative pharmacological and parasitic properties. Thus, the aim of this work was to demonstrate the leishmanicidal activity of 8-hydroxyquinoline (8-HQ) in vitro and in vivo. The leishmanicidal activity (in vitro) of 8-HQ was assayed on promastigote and intracellular amastigote forms of L. (L.) amazonensis, L. (L.) infantum chagasi, L. (V.) guyanensis L. (V.) naiffi, L. (V.) lainsoni, and L. (V.) shawi. Additionally, the levels of nitric oxide and hydrogen peroxide were analyzed. The therapeutic potential of 8-HQ was analyzed in BALB/c mice infected with a strain of L. (L.) amazonensis that causes anergic cutaneous diffuse leishmaniasis. In vitro data showed that at 24 and 72 h, 8-HQ eliminated promastigote and intracellular amastigote forms of all studied species and this effect may be potentialized by nitric oxide. Furthermore, 8-HQ was more selective than miltefosine. Infected animals treated with 8-HQ by the intralesional route dramatically reduced the number of tissue parasites in the skin, and it was associated with an increase in IFN-γ and decrease in IL-4, which correlated with a reduction in inflammatory reaction in the skin. These results strongly support the idea that 8-HQ is an alternative molecule that can be employed in the treatment of leishmaniasis, given its selectivity and multispectral action in parasites from the Leishmania genus.