Multi-target drugs active against leishmaniasis: A paradigm of drug repurposing

Repurposing FDA approved drugs against Sterol C-24 methyltransferase of Leishmania donovani: A dual in silico and in vitro approach

Leishmaniasis is a disease caused by the parasite Leishmania donovani affecting populations belonging to developing countries. The present study explores drug repurposing as an innovative strategy to identify new uses for approved clinical drugs, reducing the time and cost required for drug discovery. The three-dimensional structure of Leishmania donovani Sterol C-24 methyltransferase (LdSMT) was modeled and 1615 FDA-approved drugs from the ZINC database were computationally screened to identify the potent leads. Fulvestrant, docetaxel, indocyanine green, and iohexol were shortlisted as potential leads with the highest binding affinity and fitness scores for the concerned pathogenic receptor. Molecular dynamic simulation studies showed that the macromolecular complexes of indocyanine green and iohexol with LdSMT remained stable throughout the simulation and can be further evaluated experimentally for developing an effective drug. The proposed leads have further demonstrated promising safety profiles during cytotoxicity analysis on the J774.A1 macrophage cell line. Mechanistic analysis with these two drugs also revealed significant morphological alterations in the parasite, along with reduced intracellular parasitic load. Overall, this study demonstrates the potential of drug repurposing in identifying new treatments for leishmaniasis and other diseases affecting developing countries, highlighting the importance of considering approved clinical drugs for new applications.

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.

Natural endoperoxides as promising anti-leishmanials

BACKGROUND

The discovery of artemisinin, an endoperoxide, encouraged the scientific community to explore endoperoxides as potential anti-parasitic molecules. Although artemisinin derivatives are rapidly evolving as potent anti-malarials, their potential as anti-leishmanials is emerging gradually. The treatment of leishmaniasis, a group of neglected tropical diseases is handicapped by lack of effective vaccines, drug toxicities and drug resistance. The weak antioxidant defense mechanism of the Leishmania parasites due to lack of catalase and a selenium dependent glutathione peroxidase system makes them vulnerable to oxidative stress, and this has been successful exploited by endoperoxides.

PURPOSE

The study aimed to review the available literature on the anti-leishmanial efficacy of natural endoperoxides with a view to achieve insights into their mode of actions.

METHODS

We reviewed more around 110 research and review articles restricted to the English language, sourced from electronic bibliographic databases including PubMed, Google, Web of Science, Google scholar etc. RESULTS: Natural endoperoxides could potentially augment the anti-leishmanial drug library, with artemisinin and ascaridole emerging as potential anti-leishmanial agents. Due to higher reactivity of the cyclic peroxide moiety, and exploiting the compromised antioxidant defense of Leishmania, endoperoxides like artemisinin and ascaridole potentiate their leishmanicidal efficacy by creating a redox imbalance. Furthermore, these molecules minimally impair oxidative phosphorylation; instead inhibit glycolytic functions, culminating in depolarization of the mitochondrial membrane and depletion of ATP. Additionally, the carbon-centered free radicals generated from endoperoxides, participate in chain reactions that can generate even more reactive organic radicals that are toxic to macromolecules, including lipids, proteins and DNA, leading to cell cycle arrest and apoptosis of Leishmania parasites. However, the precise target(s) of the toxic free radicals remains open-ended.

CONCLUSION

In this overview, the spectrum of natural endoperoxide molecules as major anti-leishmanials and their mechanism of action has been delineated. In view of the substantial evidence that natural endoperoxides (e.g., artemisinin, ascaridole) exert a noxious effect on different species of Leishmania, identification and characterization of other natural endoperoxides is a promising therapeutic option worthy of further pharmacological consideration.

Spiro-Acridine Compound as a Pteridine Reductase 1 Inhibitor: in silico Target Fishing and in vitro Studies

Among the many neglected tropical diseases, leishmaniasis ranks second in mortality rate and prevalence. In a previous study, acridine derivatives were synthesized and tested for their antileishmanial activity against L. chagasi. The most active compound identified in that study (1) showed a single digit IC50 value against the parasite (1.10 μg/mL), but its macromolecular target remained unknown. Aiming to overcome this limitation, this work exploited inverse virtual screening to identify compound 1's putative molecular mechanism of action. In vitro assays confirmed that compound 1 binds to Leishmania chagasi pteridine reductase 1 (LcPTR1), with moderate affinity (Kd=33,1 μM), according to differential scanning fluorimetry assay. Molecular dynamics simulations confirm the stability of LcPTR1-compound 1 complex, supporting a competitive mechanism of action. Therefore, the workflow presented in this work successfully identified PTR1 as a macromolecular target for compound 1, allowing the designing of novel potent antileishmanial compounds.

High-throughput prioritization of target proteins for development of new antileishmanial compounds

Leishmaniasis, a vector-borne disease, is caused by the infection of Leishmania spp., obligate intracellular protozoan parasites. Presently, human vaccines are unavailable, and the primary treatment relies heavily on systemic drugs, often presenting with suboptimal formulations and substantial toxicity, making new drugs a high priority for LMIC countries burdened by the disease, but a low priority in the agenda of most pharmaceutical companies due to unattractive profit margins. New ways to accelerate the discovery of new, or the repositioning of existing drugs, are needed. To address this challenge, our study aimed to identify potential protein targets shared among clinically-relevant Leishmania species. We employed a subtractive proteomics and comparative genomics approach, integrating high-throughput multi-omics data to classify these targets based on different druggability metrics. This effort resulted in the ranking of 6502 ortholog groups of protein targets across 14 pathogenic Leishmania species. Among the top 20 highly ranked groups, metabolic processes known to be attractive drug targets, including the ubiquitination pathway, aminoacyl-tRNA synthetases, and purine synthesis, were rediscovered. Additionally, we unveiled novel promising targets such as the nicotinate phosphoribosyltransferase enzyme and dihydrolipoamide succinyltransferases. These groups exhibited appealing druggability features, including less than 40% sequence identity to the human host proteome, predicted essentiality, structural classification as highly druggable or druggable, and expression levels above the 50th percentile in the amastigote form. The resources presented in this work also represent a comprehensive collection of integrated data regarding trypanosomatid biology.

Design, synthesis and in silico molecular docking evaluation of novel 1,2,3-triazole derivatives as potent antimicrobial agents

Chalcone and triazole scaffolds have demonstrated a crucial role in the advancement of science and technology. Due to their significance, research has proceeded on the design and development of novel benzooxepine connected to 1,2,3-triazolyl chalcone structures. The new chalcone derivatives produced by benzooxepine triazole methyl ketone 2 and different aromatic carbonyl compounds 3 are discussed in this paper. All prepared compounds have well-established structures to a variety of spectral approaches, including mass analysis, 1H NMR, 13C NMR, and IR. Among the tested compounds, hybrids 4c, 4d, 4i, and 4k exhibited exceptional antibacterial susceptibilities with MIC range of 3.59-10.30 μM against the tested S. aureus strain. Compounds 4c, 4d displayed superior antifungal activity against F. oxysporum with MIC 3.25, 4.89 μM, when compared to fluconazole (MIC = 3.83 μM) respectively. On the other hand, analogues 4d, 4f, and 4k demonstrated equivalent antitubercular action against H37Rv strain with MIC range of 2.16-4.90 μM. The capacity of ligand 4f to form a stable compound on the active site of CYP51 from M. tuberculosis (1EA1) was confirmed by docking studies using amino acids Leu321(A), Pro77(A), Phe83(A), Lys74(A), Tyr76(A), Ala73(A), Arg96(A), Thr80(A), Met79(A), His259(A), and Gln72(A). Additionally, the chalcone‒1,2,3‒triazole hybrids ADME (absorption, distribution, metabolism, and excretion), characteristics of molecules, estimations of toxicity, and bioactivity parameters were assessed.

Identification of potential inhibitor against Leishmania donovani mitochondrial DNA primase through in-silico and in vitro drug repurposing approaches

Leishmania donovani is the causal organism of leishmaniasis with critical health implications affecting about 12 million people around the globe. Due to less efficacy, adverse side effects, and resistance, the available therapeutic molecules fail to control leishmaniasis. The mitochondrial primase of Leishmania donovani (LdmtPRI1) is a vital cog in the DNA replication mechanism, as the enzyme initiates the replication of the mitochondrial genome of Leishmania donovani. Hence, we target this protein as a probable drug target against leishmaniasis. The de-novo approach enabled computational prediction of the three-dimensional structure of LdmtPRI1, and its active sites were identified. Ligands from commercially available drug compounds were selected and docked against LdmtPRI1. The compounds were chosen for pharmacokinetic study and molecular dynamics simulation based on their binding energies and protein interactions. The LdmtPRI1 gene was cloned, overexpressed, and purified, and a primase activity assay was performed. The selected compounds were verified experimentally by the parasite and primase inhibition assay. Capecitabine was observed to be effective against the promastigote form of Leishmania donovani, as well as inhibiting primase activity. This study's findings suggest capecitabine might be a potential anti-leishmanial drug candidate after adequate further studies.

The Potential Use of Peptides in the Fight against Chagas Disease and Leishmaniasis

Chagas disease and leishmaniasis are both neglected tropical diseases that affect millions of people around the world. Leishmaniasis is currently the second most widespread vector-borne parasitic disease after malaria. The World Health Organization records approximately 0.7-1 million newly diagnosed leishmaniasis cases each year, resulting in approximately 20,000-30,000 deaths. Also, 25 million people worldwide are at risk of Chagas disease and an estimated 6 million people are infected with Trypanosoma cruzi. Pentavalent antimonials, amphotericin B, miltefosine, paromomycin, and pentamidine are currently used to treat leishmaniasis. Also, nifurtimox and benznidazole are two drugs currently used to treat Chagas disease. These drugs are associated with toxicity problems such as nephrotoxicity and cardiotoxicity, in addition to resistance problems. As a result, the discovery of novel therapeutic agents has emerged as a top priority and a promising alternative. Overall, there is a need for new and effective treatments for Chagas disease and leishmaniasis, as the current drugs have significant limitations. Peptide-based drugs are attractive due to their high selectiveness, effectiveness, low toxicity, and ease of production. This paper reviews the potential use of peptides in the treatment of Chagas disease and leishmaniasis. Several studies have demonstrated that peptides are effective against Chagas disease and leishmaniasis, suggesting their use in drug therapy for these diseases. Overall, peptides have the potential to be effective therapeutic agents against Chagas disease and leishmaniasis, but more research is needed to fully investigate their potential.

Targeting with Structural Analogs of Natural Products the Purine Salvage Pathway in Leishmania (Leishmania) infantum by Computer-Aided Drug-Design Approaches

Visceral Leishmaniasis (VL) has a high death rate, with 500,000 new cases and 50,000 deaths occurring annually. Despite the development of novel strategies and technologies, there is no adequate treatment for the disease. Therefore, the purpose of this study is to find structural analogs of natural products as potential novel drugs to treat VL. We selected structural analogs from natural products that have shown antileishmanial activities, and that may impede the purine salvage pathway using computer-aided drug-design (CADD) approaches. For these, we started with the vastly studied target in the pathway, the adenine phosphoribosyl transferase (APRT) protein, which alone is non-essential for the survival of the parasite. Keeping this in mind, we search for a substance that can bind to multiple targets throughout the pathway. Computational techniques were used to study the purine salvage pathway from Leishmania infantum, and molecular dynamic simulations were used to gather information on the interactions between ligands and proteins. Because of its low homology to human proteins and its essential role in the purine salvage pathway proteins network interaction, the findings further highlight the significance of adenylosuccinate lyase protein (ADL) as a therapeutic target. An analog of the alkaloid Skimmianine, N,N-diethyl-4-methoxy-1-benzofuran-6-carboxamide, demonstrated a good binding affinity to APRT and ADL targets, no expected toxicity, and potential for oral route administration. This study indicates that the compound may have antileishmanial activity, which was granted in vitro and in vivo experiments to settle this finding in the future.

Design, synthesis, electrochemistry and anti-trypanosomatid hit/lead identification of nitrofuranylazines

Chagas disease and leishmaniasis are vector-borne infectious diseases affecting both humans and animals. These neglected tropical diseases can be fatal if not treated. Hundreds to thousands of new Chagas disease and leishmaniasis cases are being reported by the WHO every year, and currently available treatments are insufficient. Severe adverse effects, impractical administrations and increased pathogen resistance against current clinical treatments underscore a serious need for the development of new drugs to curb these ailments. In search for such drugs, we investigated a series of nitrofuran-based azine derivatives. Herein, we report the design, synthesis, electrochemistry, and biological activity of these derivatives against promastigotes and amastigotes of Leishmania major, and L. donovani strains, as well as epimastigotes and trypomastigotes of Trypanosoma cruzi. Two leishmanicidal early leads and one trypanosomacidal hit with submicromolar activity were uncovered and stand for further in vivo investigation in the search for new antitrypanosomatid drugs. Future objective will focus on the identification of involved biological targets with the parasites.

Synthesis, characterization and evaluation of prenylated chalcones ethers as promising antileishmanial compounds

Drug therapy for leishmaniasis remains a major challenge as currently available drugs have limited efficacy, induce serious side-effects and are not accessible to everyone. Thus, the discovery of affordable drugs is urgently needed. Chalcones present a great potential as bioactive agents due to simple structure and functionalization capacity. The antileishmanial activity of different natural and synthetic chalcones have been reported. Here we report the synthesis of twenty-five novel prenylated chalcones that displayed antiparasitic activity in Leishmania mexicana. All the chalcones were evaluated at 5 µg/mL and eleven compounds exhibited a metabolic inhibition close to or exceeding 50%. Compounds 49, 30 and 55 were the three most active with IC50 values < 10 μM. These chalcones also showed the highest selectivity index (SI) values. Interestingly 49 and 55 possessing a substituent at a meta position in the B ring suggests that the substitution pattern influences antileishmanial activity. Additionally, a tridimensional model of fumarate reductase of L. mexicana was obtained by homology modeling. Docking studies suggest that prenylated chalcones could modulate fumarate reductase activity by binding with good affinity to two binding sites that are critical for the target. In conclusion, the novel prenylated chalcones could be considered as promising antileishmanial agents.

Navigating drug repurposing for Chagas disease: advances, challenges, and opportunities

Chagas disease is a vector-borne illness caused by the protozoan parasite Trypanosoma cruzi (T. cruzi). It poses a significant public health burden, particularly in the poorest regions of Latin America. Currently, there is no available vaccine, and chemotherapy has been the traditional treatment for Chagas disease. However, the treatment options are limited to just two outdated medicines, nifurtimox and benznidazole, which have serious side effects and low efficacy, especially during the chronic phase of the disease. Collectively, this has led the World Health Organization to classify it as a neglected disease. To address this problem, new drug regimens are urgently needed. Drug repurposing, which involves the use of existing drugs already approved for the treatment of other diseases, represents an increasingly important option. This approach offers potential cost reduction in new drug discovery processes and can address pharmaceutical bottlenecks in the development of drugs for Chagas disease. In this review, we discuss the state-of-the-art of drug repurposing approaches, including combination therapy with existing drugs, to overcome the formidable challenges associated with treating Chagas disease. Organized by original therapeutic area, we describe significant recent advances, as well as the challenges in this field. In particular, we identify candidates that exhibit potential for heightened efficacy and reduced toxicity profiles with the ultimate objective of accelerating the development of new, safe, and effective treatments for Chagas disease.

Computer-aided drug design approaches applied to screen natural product's structural analogs targeting arginase in Leishmania spp

Introduction: Leishmaniasis is a disease with high mortality rates and approximately 1.5 million new cases each year. Despite the new approaches and advances to fight the disease, there are no effective therapies. Methods: Hence, this study aims to screen for natural products' structural analogs as new drug candidates against leishmaniasis. We applied Computer-aided drug design (CADD) approaches, such as virtual screening, molecular docking, molecular dynamics simulation, molecular mechanics-generalized Born surface area (MM-GBSA) binding free estimation, and free energy perturbation (FEP) aiming to select structural analogs from natural products that have shown anti-leishmanial and anti-arginase activities and that could bind selectively against the Leishmania arginase enzyme. Results: The compounds 2H-1-benzopyran, 3,4-dihydro-2-(2-methylphenyl)-(9CI), echioidinin, and malvidin showed good results against arginase targets from three parasite species and negative results for potential toxicities. The echioidinin and malvidin ligands generated interactions in the active center at pH 2.0 conditions by MM-GBSA and FEP methods. Conclusions: This work suggests the potential anti-leishmanial activity of the compounds and thus can be further in vitro and in vivo experimentally validated.

In-vitro biological evaluation of 3,3',5,5'-tetramethoxy-biphenyl-4,4'-diol and molecular docking studies on trypanothione reductase and Gp63 from Leishmania amazonensis demonstrated anti-leishmania potential

Available treatments for leishmaniasis have been widely used since the 1940s but come at a high cost, variable efficacy, high toxicity, and adverse side-effects. 3,3',5,5'-Tetramethoxy-biphenyl-4,4'-diol (TMBP) was synthesized through laccase-catalysis of 2,6-dimethoxyphenol and displayed antioxidant and anticancer activity, and is considered a potential drug candidate. Thus, this study aimed to evaluate the anti-leishmanial effect of TMBP against promastigote and amastigote forms of Leishmania (L.) amazonensis and investigated the mechanisms involved in parasite death. TMBP treatment inhibited the proliferation (IC₅₀ 0.62-0.86 µM) and induced the death of promastigote forms by generating reactive oxygen species and mitochondrial dysfunction. In intracellular amastigotes, TMBP reduced the percentage of infected macrophages, being 62.7 times more selective to the parasite (CC₅₀ 53.93 µM). TMBP did not hemolyze sheep erythrocytes; indicative of low cytotoxicity. Additionally, molecular docking analysis on two enzyme targets of L. amazonensis: trypanothione reductase (TR) and leishmanolysin (Gp63), suggested that the hydroxyl group could be a pharmacophoric group due to its binding affinity by hydrogen bonds with residues at the active site of both enzymes. TMBP was more selective to the Gp63 target than TR. This is the first report that TMBP is a promising compound to act as an anti-leishmanial agent.

Exploring the repositioning of the amodiaquine as potential drug against visceral leishmaniasis: The in vitro effect against Leishmania infantum is associated with multiple mechanisms, involving mitochondria dysfunction, oxidative stress and loss of cell cycle control

Visceral leishmaniasis (VL) is a progressive, debilitating, and potentially fatal disease if left untreated. As a neglected tropical disease (NTD), the available treatment is restricted to a few drugs, which typically must be administered over a long period but are associated with serious adverse effects and have variability in efficacy. In this sense, drug repositioning has been considered an excellent strategy in the search for alternative treatments, especially in reducing the time and cost of the research. In this work, the repositioning potential of amodiaquine (AQ), a well-known antimalarial drug, was investigated for the treatment of VL. AQ showed significant and selective activity against promastigotes (IC₅₀ = 11.6 μg/mL) and intracellular amastigotes (IC₅₀ = 2.4 μg/mL) of L. infantum, being 10 times more destructive to the intracellular parasites than the host cell. In addition, pre-treatment of macrophages with AQ caused a significant reduction in the infection index, indicating a prophylactic effect of this drug. SEM images showed that AQ induces strong shape alterations of the promastigotes with an increase in cell volume with rounding and ribbing (vertical ridges), as well as a shortened flagellum. In addition, AQ induced depolarization of the ΔΨm, an increase in ROS and neutral lipids levels, and changes in the cell cycle in promastigotes, without alterations to the permeability of the parasite plasma membrane. L. infantum-infected macrophages treated with AQ induced the activation of oxidative mechanisms by infected host cells, with an increase in ROS and NO levels. Finally, in vitro interactions between AQ and miltefosine were found to have an additive effect in both biological stages of the parasite, with the ∑FIC₅₀ values ranging from 0.74 to 1.16 μg/mL and 0.54-1.11 μg/mL for promastigotes and intracellular amastigotes, respectively. Overall, these data highlight the utility of drug repurposing and indicate future preclinical testing for AQ itself or in combination as a potential VL treatment.

Small molecules containing chalcogen elements (S, Se, Te) as new warhead to fight neglected tropical diseases

Neglected tropical diseases (NTDs) encompass a group of infectious diseases with a protozoan etiology, high incidence, and prevalence in developing countries. As a result, economic factors constitute one of the main obstacles to their management. Endemic countries have high levels of poverty, deprivation and marginalization which affect patients and limit their access to proper medical care. As a matter of fact, statistics remain uncollected in some affected areas due to non-reporting cases. World Health Organization and other organizations proposed a plan for the eradication and control of the vector, although many of these plans were halted by the COVID-19 pandemic. Despite of the available drugs to treat these pathologies, it exists a lack of effectiveness against several parasite strains. Treatment protocols for diseases such as American trypanosomiasis (Chagas disease), leishmaniasis, and human African trypanosomiasis (HAT) have not achieved the desired results. Unfortunately, these drugs present limitations such as side effects, toxicity, teratogenicity, renal, and hepatic impairment, as well as high costs that have hindered the control and eradication of these diseases. This review focuses on the analysis of a collection of scientific shreds of evidence with the aim of identifying novel chalcogen-derived molecules with biological activity against Chagas disease, leishmaniasis and HAT. Compounds illustrated in each figure share the distinction of containing at least one chalcogen element. Sulfur (S), selenium (Se), and tellurium (Te) have been grouped and analyzed in accordance with their design strategy, chemical synthesis process and biological activity. After an exhaustive revision of the related literature on S, Se, and Te compounds, 183 compounds presenting excellent biological performance were gathered against the different causative agents of CD, leishmaniasis and HAT.

Current leishmaniasis drug discovery

Leishmaniasis is a complex protozoan infectious disease and, associated with malnutrition, poor health services and unavailability of prophylactic control measures, neglected populations are particularly affected. Current drug regimens are outdated and associated with some drawbacks, such as cytotoxicity and resistance, and the development of novel, efficacious and less toxic drug regimens is urgently required. In addition, leishmanial pathogenesis is not well established or understood, and a prophylactic vaccine is an unfulfilled goal. Human kinetoplastid protozoan infections, including leishmaniasis, have been neglected for many years, and in an attempt to overcome this situation, some new drug targets were recently identified, enabling the development of new drugs and vaccines. Compounds from new drug classes have also shown excellent antileishmanial activities, some of the most promising ones included in clinical trials, and could be a hope to control the disease burden of this endemic disease in the near future. In this review, we discuss the limitations of current control methods, explore the wide range of compounds that are being screened and identified as antileishmanial drug prototypes, summarize the advances in identifying new drug targets aiming at innovative treatments and explore the state-of-art vaccine development field, including immunomodulation strategies.

Aminoacyl-tRNA synthetase (AARS) as an attractive drug target in neglected tropical trypanosomatid diseases-Leishmaniasis, Human African Trypanosomiasis and Chagas disease

TriTryp diseases (Leishmaniasis, Human African Trypanosomiasis (HAT), and Chagas disease) are devastating parasitic neglected tropical diseases (NTDs) that affect billions of people in developing countries, cause high mortality in humans, and impose a large socio-economic burden. The current treatment options against tritryp diseases are suboptimal and challenging due to the emergence of resistance against available tritryp drugs. Hence, designing and developing effective anti-tritryp drugs with novel targets are required. Aminoacyl-tRNA synthetases (AARSs) involved in specific aminoacylation of transfer RNAs (tRNAs), interrupt protein synthesis through inhibitors, and retard the parasite growth. AaRSs have long been studied as therapeutic targets in bacteria, and three aaRS inhibitors, mupirocin (against IleRS), tavaborole AN2690 (against LeuRS), and halofuginone (against ProRS), are already in clinical practice. The structural differences between tritryp and human aaRSs and the presence of unique sequences (N-terminal domain/C-terminal domain/catalytic domain) make them potential target for developing selective inhibitors. Drugs based on a single aaRS target developed by high-throughput screening (HTS) are less effective due to the emergence of resistance. However, designing multi-targeted drugs may be a better strategy for resistance development. In this perspective, we discuss the characteristics of tritryp aaRSs, sequence conservation in their orthologs and their peculiarities, recent advancements towards the single-target and multi-target aaRS inhibitors developed through rational design.

Metabolic Pathways of Leishmania Parasite: Source of Pertinent Drug Targets and Potent Drug Candidates

Leishmaniasis is a tropical disease caused by a protozoan parasite Leishmania that is transmitted via infected female sandflies. At present, leishmaniasis treatment mainly counts on chemotherapy. The currently available drugs against leishmaniasis are costly, toxic, with multiple side effects, and limitations in the administration route. The rapid emergence of drug resistance has severely reduced the potency of anti-leishmanial drugs. As a result, there is a pressing need for the development of novel anti-leishmanial drugs with high potency, low cost, acceptable toxicity, and good pharmacokinetics features. Due to the availability of preclinical data, drug repurposing is a valuable approach for speeding up the development of effective anti-leishmanial through pointing to new drug targets in less time, having low costs and risk. Metabolic pathways of this parasite play a crucial role in the growth and proliferation of Leishmania species during the various stages of their life cycle. Based on available genomics/proteomics information, known pathways-based (sterol biosynthetic pathway, purine salvage pathway, glycolysis, GPI biosynthesis, hypusine, polyamine biosynthesis) Leishmania-specific proteins could be targeted with known drugs that were used in other diseases, resulting in finding new promising anti-leishmanial therapeutics. The present review discusses various metabolic pathways of the Leishmania parasite and some drug candidates targeting these pathways effectively that could be potent drugs against leishmaniasis in the future.

New Phenylglycinamide Derivatives with Hybrid Structure as Candidates for New Broad-Spectrum Anticonvulsants

In the present study, a focused combinatorial chemistry approach was applied to merge structural fragments of well-known TRPV1 antagonists with a potent anticonvulsant lead compound, KA-104, that was previously discovered by our group. Consequently, a series of 22 original compounds has been designed, synthesized, and characterized in the in vivo and in vitro assays. The obtained compounds showed robust in vivo antiseizure activity in the maximal electroshock (MES) test and in the 6 Hz seizure model (using both 32 and 44 mA current intensities). The most potent compounds 53 and 60 displayed the following pharmacological profile: ED₅₀ = 89.7 mg/kg (MES), ED₅₀ = 29.9 mg/kg (6 Hz, 32 mA), ED₅₀ = 68.0 mg/kg (6 Hz, 44 mA), and ED₅₀ = 73.6 mg/kg (MES), ED₅₀ = 24.6 mg/kg (6 Hz, 32 mA), and ED₅₀ = 56.3 mg/kg (6 Hz, 44 mA), respectively. Additionally, 53 and 60 were effective in the ivPTZ seizure threshold and had no influence on the grip strength and body temperature in mice. The in vitro binding and functional assays indicated a multimodal mechanism of action for 53 and 60. These molecules, beyond TRPV1 antagonism, inhibited calcium currents and fast sodium currents in patch-clamp assays. Further studies proved beneficial in vitro ADME-Tox properties for 53 and 60 (i.e., high metabolic stability, weak influence on CYPs, no neurotoxicity, etc.). Overall, 53 and 60 seem to be interesting candidates for future preclinical development in epilepsy and pain indications due to their interaction with the TRPV1 channel.

In Silico Antiprotozoal Evaluation of 1,4-Naphthoquinone Derivatives against Chagas and Leishmaniasis Diseases Using QSAR, Molecular Docking, and ADME Approaches

Chagas and leishmaniasis are two neglected diseases considered as public health problems worldwide, for which there is no effective, low-cost, and low-toxicity treatment for the host. Naphthoquinones are ligands with redox properties involved in oxidative biological processes with a wide variety of activities, including antiparasitic. In this work, in silico methods of quantitative structure–activity relationship (QSAR), molecular docking, and calculation of ADME (absorption, distribution, metabolism, and excretion) properties were used to evaluate naphthoquinone derivatives with unknown antiprotozoal activity. QSAR models were developed for predicting antiparasitic activity against Trypanosoma cruzi, Leishmania amazonensis, and Leishmania infatum, as well as the QSAR model for toxicity activity. Most of the evaluated ligands presented high antiparasitic activity. According to the docking results, the family of triazole derivatives presented the best affinity with the different macromolecular targets. The ADME results showed that most of the evaluated compounds present adequate conditions to be administered orally. Naphthoquinone derivatives show good biological activity results, depending on the substituents attached to the quinone ring, and perhaps the potential to be converted into drugs or starting molecules.

Naphthoquinone as a New Chemical Scaffold for Leishmanicidal Inhibitors of Leishmania GSK-3

More than 1 billion people live in areas endemic for leishmaniasis, which is a relevant threat for public health worldwide. Due to the inadequate treatments, there is an urgent need to develop novel alternative drugs and to validate new targets to fight this disease. One appealing approach is the selective inhibition of protein kinases (PKs), enzymes involved in a wide range of processes along the life cycle of Leishmania. Several PKs, including glycogen synthase kinase 3 (GSK-3), have been validated as essential for this parasite by genetic or pharmacological methods. Recently, novel chemical scaffolds have been uncovered as Leishmania GSK-3 inhibitors with antiparasitic activity. In order to find new inhibitors of this enzyme, a virtual screening of our in-house chemical library was carried out on the structure of the Leishmania GSK-3. The virtual hits identified were experimentally assayed both for leishmanicidal activity and for in vitro inhibition of the enzyme. The best hits have a quinone scaffold. Their optimization through a medicinal chemistry approach led to a set of new compounds, provided a frame to establish biochemical and antiparasitic structure–activity relationships, and delivered molecules with an improved selectivity index. Altogether, this study paves the way for a systemic search of this class of inhibitors for further development as potential leishmanicidal drugs.

Advancement in leishmaniasis diagnosis and therapeutics: An update

Leishmaniasis is regarded as a neglected tropical disease by World Health Organization (WHO) and is ranked next to malaria as the deadliest protozoan disease. The primary causative agents of the disease comprise of diverse leishmanial species sharing clinical features ranging from skin abrasions to lethal infection in the visceral organs. As several Leishmania species are involved in infection, the role of accurate diagnosis becomes pivotal in adding new dimensions to anti-leishmanial therapy. Diagnostic methods must be fast, reliable, easy to perform, highly sensitive, and specific to differentiate among similar parasitic diseases. Herein, we present the conventional and recent approaches impended for the disease diagnosis and their sensitivity, specificity, and clinical application in parasite detection. Furthermore, we have also elaborated various new methods to cure leishmaniasis, which include host-directed therapies, drug repurposing, nanotechnology, and combinational therapy. This review addresses novel techniques and innovations in leishmaniasis, which can aid in unraveling new strategies to fight against the deadly infection.

Nitric Oxide Induction in Peritoneal Macrophages by a 1,2,3-Triazole Derivative Improves Its Efficacy upon Leishmania amazonensis In Vitro Infection

1,2,3-Triazole is one of the most flexible chemical scaffolds broadly used in various fields. Here, we report the antileishmanial activity of 1,2,3-triazole derivatives, the ultrastructural alterations induced by their treatment, and the nitric oxide (NO) modulation effect on their efficacy against Leishmania amazonensis in vitro infection. After the screening of eleven compounds, compound 4 exhibited better results against L. amazonensis promastigotes (IC₅₀ = 15.52 ± 3.782 μM) and intracellular amastigotes (IC₅₀ = 4.10 ± 1.136 μM), 50% cytotoxicity concentration at 84.01 ± 3.064 μM against BALB/c peritoneal macrophages, and 20.49-fold selectivity for the parasite over the cells. Compound 4 induced ultrastructural mitochondrial alterations and lipid inclusions in L. amazonensis promastigotes, upregulated tumor necrosis factor α, interleukin (IL)-1β, IL-6, IL-12, and IL-10 messenger RNA expressions, and enhanced the NO production, verified by nitrite (p = 0.0095) and inducible nitric oxide synthase expression (p = 0.0049) quantification, which played an important role in its activity against intramacrophagic L. amazonensis. In silico prediction in association with antileishmanial activity results showed compound 4 as a hit compound with promising potential for further studies of new leishmaniasis treatment options.

Ex Vivo Phenotypic Screening of Two Small Repurposing Drug Collections Identifies Nifuratel as a Potential New Treatment against Visceral and Cutaneous Leishmaniasis

Leishmaniases are vector-borne neglected diseases caused by single-celled parasites. The search for new antileishmanial drugs has experienced a strong boost thanks to the application of bioimaging to phenotypic screenings based on intracellular amastigotes. Mouse splenic explants infected with fluorescent strains of Leishmania are proven tools of drug discovery, where hits can be easily transferred to preclinical in vivo models. We have developed a two-staged platform for antileishmanial drugs. First, we screened two commercial collections of repurposing drugs with a total of 1769 compounds in ex vivo mouse splenocytes infected with an infrared emitting Leishmania infantum strain. The most active and safest compounds were scaled-up to in vivo models of chronic Leishmania donovani visceral leishmaniasis and Leishmania major cutaneous leishmaniasis. From the total of 1769 compounds, 12 hits with selective indices >35 were identified, and 4 of them were tested in vivo in a model of L. donovani visceral leishmaniasis. Nifuratel, a repurposed synthetic nitrofuran, when administered orally at 50 mg/kg bw once or twice a day for 10 days, caused >80% reduction in the parasitic load. Furthermore, the intralesional administration of nifuratel in a model of cutaneous leishmaniasis by L. major produced the parasitological cure. From the previous results we have deduced the great capacity of mouse splenic explants to identify new hits, a model which could be easily transferred to in vivo models, as well as the potential use of nifuratel as an alternative to the current treatment of cutaneous leishmaniasis.

Synthesis and biological activity of novel 4-aminoquinoline/1,2,3-triazole hybrids against Leishmania amazonensis

Quinoline and 1,2,3-triazoles are well-known nitrogen-based heterocycles presenting diverse pharmacological properties, although their antileishmanial activity is still poorly exploited. As an effort to contribute with studies involving these interesting chemical groups, in the present study, a series of compounds derived from 4-aminoquinoline and 1,2,3-triazole were synthetized and biological studies using L. amazonensis species were performed. The results pointed that the derivative 4, a hybrid of 4-aminoquinoline/1,2,3-triazole exhibited the best antileishmanial action, with inhibitory concentration (IC₅₀) values of ~1 µM against intramacrophage amastigotes of L. amazonensis , and being 16-fold more active to parasites than to the host cell. The mechanism of action of derivative 4 suggest a multi-target action on Leishmania parasites, since the treatment of L. amazonensis promastigotes caused mitochondrial membrane depolarization, accumulation of ROS products, plasma membrane permeabilization, increase in neutral lipids, exposure of phosphatidylserine to the cell surface, changes in the cell cycle and DNA fragmentation. The results suggest that the antileishmanial effect of this compound is primarily altering critical biochemical processes for the correct functioning of organelles and macromolecules of parasites, with consequent cell death by processes related to apoptosis-like and necrosis. No up-regulation of reactive oxygen and nitrogen intermediates was promoted by derivative 4 on L. amazonensis -infected macrophages, suggesting a mechanism of action independent from the activation of the host cell. In conclusion, data suggest that derivative 4 presents selective antileishmanial effect, which is associated with multi-target action, and can be considered for future studies for the treatment against disease.

Leismanicidal Activity of Propolis Collected in the Semiarid Region of Brazil

Objective: The aim of the current study is to investigate the chemical composition, cytotoxic effect, and leishmanicidal activity of propolis collected in the semi-arid region of Bahia, Brazil.

Methods: EtOH extract, hexane, EtOAc and MeOH fractions from propolis were analyzed by ultra-performance liquid chromatography coupled with diode array detector and quadrupole time-of-flight mass spectrometry. The identification was based on the exact mass, general fragmentation behaviors and UV absorption of the flavonoids. The in vitro cytotoxic effect and leishmanicidal activity of ethanolic extract, hexane, ethyl acetate, and methanolic fractions of propolis were evaluated.

Results: Five triterpenes and twenty-four flavonoids were identified. The propolis did not present toxicity to the host cell up to the maximum concentration tested. In addition, all tested samples showed statistically significant activity against promastigotes of Leishmania chagasi and Leishmania amazonensis. Regarding the activity against amastigote forms of L. amazonensis, the hexane fraction, presented statistically significant activity with IC₅₀ of 1.3 ± 0.1 μg/ml.

Conclusion: The results support the idea that propolis can be used for future antileishmania studies.

A Novel Automated Framework for QSAR Modeling of Highly Imbalanced Leishmania High-Throughput Screening Data

In silico prediction of antileishmanial activity using quantitative structure-activity relationship (QSAR) models has been developed on limited and small datasets. Nowadays, the availability of large and diverse high-throughput screening data provides an opportunity to the scientific community to model this activity from the chemical structure. In this study, we present the first KNIME automated workflow to modeling a large, diverse, and highly imbalanced dataset of compounds with antileishmanial activity. Because the data is strongly biased toward inactive compounds, a novel strategy was implemented based on the selection of different balanced training sets and a further consensus model using single decision trees as the base model and three criteria for output combinations. The decision tree consensus was adopted after comparing its classification performance to consensuses built upon Gaussian-Naı̈ve-Bayes, Support-Vector-Machine, Random-Forest, Gradient-Boost, and Multi-Layer-Perceptron base models. All these consensuses were rigorously validated using internal and external test validation sets and were compared against each other using Friedman and Bonferroni-Dunn statistics. For the retained decision tree-based consensus model, which covers 100% of the chemical space of the dataset and with the lowest consensus level, the overall accuracy statistics for test and external sets were between 71 and 74% and 71 and 76%, respectively, while for a reduced chemical space (21%) and with an incremental consensus level, the accuracy statistics were substantially improved with values for the test and external sets between 86 and 92% and 88 and 92%, respectively. These results highlight the relevance of the consensus model to prioritize a relatively small set of active compounds with high prediction sensitivity using the Incremental Consensus at high level values or to predict as many compounds as possible, lowering the level of Incremental Consensus. Finally, the workflow developed eliminates human bias, improves the procedure reproducibility, and allows other researchers to reproduce our design and use it in their own QSAR problems.

In Silico Insights into the Mechanism of Action of Epoxy-α-Lapachone and Epoxymethyl-Lawsone in Leishmania spp

Epoxy-α-lapachone (Lap) and Epoxymethyl-lawsone (Law) are oxiranes derived from Lapachol and have been shown to be promising drugs for Leishmaniases treatment. Although, it is known the action spectrum of both compounds affect the Leishmania spp. multiplication, there are gaps in the molecular binding details of target enzymes related to the parasite’s physiology. Molecular docking assays simulations were performed using DockThor server to predict the preferred orientation of both compounds to form stable complexes with key enzymes of metabolic pathway, electron transport chain, and lipids metabolism of Leishmania spp. This study showed the hit rates of both compounds interacting with lanosterol C-14 demethylase (−8.4 kcal/mol to −7.4 kcal/mol), cytochrome c (−10.2 kcal/mol to −8.8 kcal/mol), and glyceraldehyde-3-phosphate dehydrogenase (−8.5 kcal/mol to −7.5 kcal/mol) according to Leishmania spp. and assessed compounds. The set of molecular evidence reinforces the potential of both compounds as multi-target drugs for interrupt the network interactions between parasite enzymes, which can lead to a better efficacy of drugs for the treatment of leishmaniases.

In vitro and in vivo antileishmanial activity of β-acetyl-digitoxin, a cardenolide of Digitalis lanata potentially useful to treat visceral leishmaniasis

Current treatments of visceral leishmaniasis face limitations due to drug side effects and/or high cost, along with the emergence of parasite resistance. Novel and low-cost antileishmanial agents are therefore required. We report herein the antileishmanial activity of β-acetyl-digitoxin (b-AD), a cardenolide isolated from Digitalis lanata leaves, assayed in vitro and in vivo against Leishmania infantum. Results showed direct action of b-AD against parasites, as well as efficacy for the treatment of Leishmania-infected macrophages. In vivo experiments using b-AD-containing Pluronic^® F127 polymeric micelles (b-AD/Mic) to treat L. infantum-infected mice showed that this composition reduced the parasite load in distinct organs in more significant levels. It also induced the development of anti-parasite Th1-type immunity, attested by high levels of IFN-γ, IL-12, TNF-α, GM-CSF, nitrite and specific IgG2a antibodies, in addition to low IL-4 and IL-10 contents, along with higher IFN-γ-producing CD4⁺ and CD8⁺ T-cell frequency. Furthermore, low toxicity was found in the organs of the treated animals. Comparing the therapeutic effect between the treatments, b-AD/Mic was the most effective in protecting animals against infection, when compared to the other groups including miltefosine used as a drug control. Data found 15 days after treatment were similar to those obtained one day post-therapy. In conclusion, the results obtained suggest that b-AD/Mic is a promising antileishmanial agent and deserves further studies to investigate its potential to treat visceral leishmaniasis.

Nanoemulsified Butenafine for Enhanced Performance against Experimental Cutaneous Leishmaniasis

The production of ergosterol lipid involves the activity of different enzymes and is a crucial event for the Leishmania membrane homeostasis. Such enzymes can be blocked by azoles and allylamines drugs, such as the antifungal butenafine chloride. This drug was active on parasites that cause cutaneous and visceral leishmaniasis. Based on the leishmanicidal activity of butenafine chloride and considering the absence of reports about the therapeutic potential of this drug in cutaneous leishmaniasis, the present work is aimed at analyzing the efficacy of butenafine formulated in two different topical delivery systems, the self-nanoemulsifying drug delivery systems (BUT-SNEDDS) and in a SNEDDS-based nanogel (BUT-SNEDDS gel) as well as in the free form in experimental cutaneous leishmaniasis. Physical studies showed that both formulations were below 300 nm with low polydispersity (<0.5) and good colloidal stability (around -25 mV). Increased steady-state flux was reported for nanoenabled butenafine formulations with reduced lag time in Franz cell diffusion assays across Strat-M membranes. No toxic or inflammatory reactions were detected in animals treated with BUT-SNEDDS, BUT-SNEDDS gel, or butenafine. Animals topically treated with butenafine (free or nanoformulated) showed small dermal lesions and low tissue parasitism. Furthermore, BUT-SNEDD gel and butenafine presented similar efficacy than the standard drug Glucantime given by the intralesional route. Increased levels of IFN-γ were observed in animals treated with BUT-SNEDDS gel or butenafine. Based on these data, the antifungal drug butenafine chloride can be considered an interesting repurposed drug for the treatment of cutaneous leishmaniasis.

Drug Repurposing of the Alcohol Abuse Medication Disulfiram as an Anti-Parasitic Agent

Parasitic infections contribute significantly to worldwide morbidity and mortality. Antibiotic treatment is essential for managing patients infected with these parasites since control is otherwise challenging and there are no vaccines available for prevention. However, new antimicrobial therapies are urgently needed as significant problems exist with current treatments such as drug resistance, limited options, poor efficacy, as well as toxicity. This situation is made worse by the challenges of drug discovery and development which is costly especially for non-profitable infectious diseases, time-consuming, and risky with a high failure rate. Drug repurposing which involves finding new use for existing drugs may help to more rapidly identify therapeutic candidates while drastically cutting costs of drug research and development. In this perspective article, we discuss the importance of drug repurposing, review disulfiram pharmacology, and highlight emerging data that supports repurposing disulfiram as an anti-parasitic, exemplified by the major diarrhea-causing parasite Entamoeba histolytica.

Identification of Trypanosoma cruzi Growth Inhibitors with Activity In Vivo within a Collection of Licensed Drugs

Chagas disease, caused by the parasite Trypanosoma cruzi (T. cruzi), affects more than six million people worldwide, with its greatest burden in Latin America. Available treatments present frequent toxicity and variable efficacy at the chronic phase of the infection, when the disease is usually diagnosed. Hence, development of new therapeutic strategies is urgent. Repositioning of licensed drugs stands as an attractive fast-track low-cost approach for the identification of safer and more effective chemotherapies. With this purpose we screened 32 licensed drugs for different indications against T. cruzi. We used a primary in vitro assay of Vero cells infection by T. cruzi. Five drugs showed potent activity rates against it (IC₅₀ < 4 µmol L⁻¹), which were also specific (selectivity index >15) with respect to host cells. T. cruzi inhibitory activity of four of them was confirmed by a secondary anti-parasitic assay based on NIH-3T3 cells. Then, we assessed toxicity to human HepG2 cells and anti-amastigote specific activity of those drugs progressed. Ultimately, atovaquone-proguanil, miltefosine, and verapamil were tested in a mouse model of acute T. cruzi infection. Miltefosine performance in vitro and in vivo encourages further investigating its use against T. cruzi.

Combination of Subtherapeutic Doses of Tretazicar and Liposomal Amphotericin B Suppresses and Cures Leishmania major-Induced Cutaneous Lesions in Murine Models

Cutaneous leishmaniasis (CL) is the most common form of leishmaniasis affecting human populations, yet CL remains largely ignored in drug discovery programs. CL causes disfiguring skin lesions and often relapses after "clinical cure" using existing therapeutics. To expand the pool of anti-CL lead candidates, we implemented an integrated screening platform comprising three progressive Leishmania parasite life cycle forms. We identified tretazicar (CB1954, 5-(aziridin-1-yl)-2,4-dinitrobenzamide) as a potent inhibitor of Leishmania parasite viability across multiple Leishmania species, which translated into complete and prolonged in vivo suppression of CL lesion formation in BALB/c mice when used as a monotherapy and which was superior to liposomal amphotericin B. In addition, oral twice a day administration of tretazicar healed the majority of existing Leishmania major (L. major) cutaneous lesions. In drug combination studies, there was a strong potentiation when subtherapeutic doses of liposomal amphotericin B and tretazicar were simultaneously administered. This drug combination decreased L. major lesion size in mice earlier than individual monotherapy drug treatments and maintained all animals lesion free for up to 64 days after treatment cessation. In contrast, administration of subtherapeutic doses of tretazicar or amphotericin B as monotherapies resulted in no or partial lesion cures, respectively. We propose that tretazicar should be explored as a component of a systemic CL combination therapy and potentially for other diseases where amphotericin B is a first line therapy.

The ultimate fate determinants of drug induced cell-death mechanisms in Trypanosomatids

Chemotherapy constitutes a major part of modern-day therapy for infectious and chronic diseases. A drug is said to be effective if it can inhibit its target, induce stress, and thereby trigger an array of cell death pathways in the form of programmed cell death, autophagy, necrosis, etc. Chemotherapy is the only treatment choice against trypanosomatid diseases like Leishmaniasis, Chagas disease, and sleeping sickness. Anti-trypanosomatid drugs can induce various cell death phenotypes depending upon the drug dose and growth stage of the parasites. The mechanisms and pathways triggering cell death in Trypanosomatids serve to help identify potential targets for the development of effective anti-trypanosomatids. Studies show that the key proteins involved in cell death of trypanosomatids are metacaspases, Endonuclease G, Apoptosis-Inducing Factor, cysteine proteases, serine proteases, antioxidant systems, etc. Unlike higher eukaryotes, these organisms either lack the complete set of effectors involved in cell death pathways, or are yet to be deciphered. A detailed summary of the existing knowledge of different drug-induced cell death pathways would help identify the lacuna in each of these pathways and therefore open new avenues for research and thereby new therapeutic targets to explore. The cell death pathway associated complexities in metazoans are absent in trypanosomatids; hence this summary can also help understand the trigger points as well as cross-talk between these pathways. Here we provide an in-depth overview of the existing knowledge of these drug-induced trypanosomatid cell death pathways, describe their associated physiological changes, and suggest potential interconnections amongst them.

Thiohydantoins as anti-leishmanial agents: n vitro biological evaluation and multi-target investigation by molecular docking studies

Leishmaniasis is a neglected tropical disease caused by protozoa of the genus Leishmania. The first-line treatment of this disease is still based on pentavalent antimonial drugs that have a high toxicity profile, which could induce parasitic resistance. Therefore, there is a critical need to discover more effective and selective novel anti-leishmanial agents. In this context, thiohydantoins are a versatile class of substances due to their simple synthesis and several biological activities. In this work, thiohydantoins 1a-l were evaluated in vitro for antileishmania activity. Among them, four derivatives (1c, 1e, 1h and 1l) showed promising IC₅₀ values around 10 µM against promastigotes forms of Leishmania amazonensis and low cytotoxicity profile for peritoneal macrophages cells. Besides, these compounds induce oxidative stress through an increase in ROS production and the labeling of annexin-V and propidium iodide, indicating that promastigotes were undergoing a late apoptosis-like process. Additionally, molecular consensual docking analysis was carried out against two important targets to L. amazonensis: arginase and trypanothione reductase enzymes. Docking results suggest that thiohydantoin ring could be a pharmacophoric group due to its binding affinity by hydrogens bond interactions with important amino acid residues at the active site of both enzymes. These results demonstrate that compounds 1c, 1e, 1h and 1l may are promising in future advance studies.Communicated by Ramaswamy H. Sarma.

Synthesis, physicochemical properties and biological activities of novel alkylphosphocholines with foscarnet moiety

A series of alkylphosphocholines with foscarnet moiety was synthesized. The structure of these zwitterionic amphiphiles was modified in both polar and non-polar parts of surfactant molecule. Investigations of physicochemical properties are represented by the determination of critical micelle concentration, the surface tension value at the cmc and the surface area per surfactant head group utilising surface tension measurements. Hydrodynamic diameter of surfactant micelles was determined using the dynamic light scattering technique. Alkylphosphocholines exhibit significant cytotoxic, anticandidal (Candida albicans) and antiamoebal (Acanthamoeba spp. T4 genotype) activity. The relationship between the structure, physicochemical properties and biological activity of the tested compounds revealed that lipophilicity has a significant influence on biological activity of the investigated surfactants. More lipophilic alkylphosphocholines with octadecyl chains show cytotoxic activity against cancer cells which is higher than that of the compounds with shorter alkyl chains. The opposite situation was observed in case of anticandidal and antiamoebal activity of these surfactants. The most active compounds were found to have pentadecyl chains. The foscarnet analogue of miltefosine C15-PFA-C showed the highest anticandidal activity. The minimum value of anticandidal activity of this compound is 1,4 μM thus representing the highest anticandidal activity found within the group of alkylphosphocholines.

Recent advances and new strategies on leishmaniasis treatment

Leishmaniasis is one of the most important tropical neglected diseases according to the World Health Organization. Even after more than a century, we still have few drugs for the disease therapy and their great toxicity and side effects put in check the treatment control program around the world. Moreover, the emergence of strains resistant to conventional drugs, co-infections such as HIV/Leishmania spp., the small therapeutic arsenal (pentavalent antimonials, amphotericin B and formulations, and miltefosine), and the low investment for the discovery/development of new drugs force researchers and world health agencies to seek new strategies to combat and control this important neglected disease. In this context, the aim of this review is to summarize new advances and new strategies used on leishmaniasis therapy addressing alternative and innovative treatment paths such as physical and local/topical therapies, combination or multi-drug uses, immunomodulation, drug repurposing, and the nanotechnology-based drug delivery systems.Key points• The treatment of leishmaniasis is a challenge for global health agencies.• Toxicity, side effects, reduced therapeutic arsenal, and drug resistance are the main problems.• New strategies and recent advances on leishmaniasis treatment are urgent.• Immunomodulators, nanotechnology, and drug repurposing are the future of leishmaniasis treatment.

Pharmaceutical agents for treatment of leishmaniasis: a patent landscape

INTRODUCTION

Leishmaniasis is a neglected tropical disease caused by protozoa of the genus Leishmania. Worldwide, approximately 1.5-2 million new cases of leishmaniasis and 20,000-30,000 deaths occurs each year. Effective treatment for all forms of leishmaniasis have numerous adverse effects contributing to poor adherence and/or treatment interruption by the patient. Development of novel therapies, as multitarget drugs, for example, can contribute to accelerate discover safer, more active, and patient-compliant drugs for leishmaniasis treatment.

AREAS COVERED

In this review, authors summarize pharmaceutical agents for treatment of leishmaniasis developed between 2014 and 2019, which includes synthetic and natural drugs for specific treatments, as well as considering new approaches and strategies using drug delivery system.

EXPERT OPINION

Universities or public research institutes produced most of the patents related to pharmaceutical agents for treatment of leishmaniasis in this review, and the majority of the inventions disclosed did not conduct clinical trials. In other words, there is still a lot of investment to be done for the identification of new drugs.

Trichomonas vaginalis NTPDase inhibited by lycorine modulates the parasite-neutrophil interaction

Lycorine is an Amaryllidaceae alkaloid that presents anti-Trichomonas vaginalis activity. T. vaginalis causes trichomoniasis, the most common non-viral sexually transmitted infection. The modulation of T. vaginalis purinergic signaling through the ectonucleotidases, nucleoside triphosphate diphosphohydrolase (NTPDase), and ecto-5'-nucleotidase represents new targets for combating the parasite. With this knowledge, the aim of this study was to investigate whether NTPDase and ecto-5'-nucleotidase inhibition by lycorine could lead to extracellular ATP accumulation. Moreover, the lycorine effect on the reactive oxygen species (ROS) production by neutrophils and parasites was evaluated as well as the alkaloid toxicity. The metabolism of purines was assessed by HPLC. ROS production was measured by flow cytometry. Cytotoxicity against epithelial vaginal cells and fibroblasts was tested, as well as the hemolytic effect of lycorine and its in vivo toxicity in Galleria mellonella larvae. Our findings showed that lycorine caused ATP accumulation due to NTPDase inhibition. The alkaloid did not affect the ROS production by T. vaginalis; however, it increased ROS levels in neutrophils incubated with lycorine-treated trophozoites. Lycorine was cytotoxic against vaginal epithelial cells and fibroblasts; conversely, it was not hemolytic neither exhibited toxicity against the in vivo model of G. mellonella larvae. Overall, besides having anti-T. vaginalis activity, lycorine modulates ectonucleotidases and stimulates neutrophils to secrete ROS. This mechanism of action exerted by the alkaloid could enhance the susceptibility of T. vaginalis to host immune cell, contributing to protozoan clearance.

Recent strategies for the development of oral medicines for the treatment of visceral leishmaniasis

Considered prevalent in many countries on five continents, especially in low-income regions, leishmaniasis is a neglected tropical disease classified by World Health Organization as one of the diseases for which the development of new treatments is a priority. It is an infectious disease caused by protozoa of the genus Leishmania, whose species may cause different clinical manifestations, such as cutaneous and visceral leishmaniasis (VL). Treatment is exclusively by drug therapy, as it has not been possible to develop vaccines yet. Currently available drugs are not fully effective in all cases; they have parenteral administration and exhibit a number of serious and very common adverse effects. The only oral drug available is expensive and it is not available in many endemic countries. Injectable administration is the main problem of treatments, since it requires patients to go to health centers, hospitalization and professional administration, which are conditions that are not adapted to the reality of the poverty conditions of patients with the disease. In this context, the development of an oral medicine has become a focus as it may solve many of these issues. Based on this scenario, this review aimed to investigate which therapeutic alternatives have been studied for the development of oral drugs directed to the treatment of human VL.

Tissue-specific transcriptomic changes associated with AmBisome® treatment of BALB/c mice with experimental visceral leishmaniasis

Background: Liposomal amphotericin B (AmBisome®) as a treatment modality for visceral leishmaniasis (VL) has had significant impact on patient care in some but not all regions where VL is endemic.  As the mode of action of AmBisome® in vivo is poorly understood, we compared the tissue-specific transcriptome in drug-treated vs untreated mice with experimental VL.    Methods:  BALB/c mice infected with L. donovani were treated with 8mg/kg AmBisome®, resulting in parasite elimination from liver and spleen over a 7-day period. At day 1 and day 7 post treatment (R x+1 and R x+7), transcriptomic profiling was performed on spleen and liver tissue from treated and untreated mice and uninfected mice.  BALB/c mice infected with M. bovis BCG (an organism resistant to amphotericin B) were analysed to distinguish between direct effects of AmBisome® and those secondary to parasite death.   Results: AmBisome® treatment lead to rapid parasitological clearance.  At R x+1, spleen and liver displayed only 46 and 88 differentially expressed (DE) genes (P<0.05; 2-fold change) respectively. In liver, significant enrichment was seen for pathways associated with TNF, fatty acids and sterol biosynthesis.  At R x+7, the number of DE genes was increased (spleen, 113; liver 400).  In spleen, these included many immune related genes known to be involved in anti-leishmanial immunity. In liver, changes in transcriptome were largely accounted for by loss of granulomas.   PCA analysis indicated that treatment only partially restored homeostasis.  Analysis of BCG-infected mice treated with AmBisome® revealed a pattern of immune modulation mainly targeting macrophage function.   Conclusions: Our data indicate that the tissue response to AmBisome® treatment varies between target organs and that full restoration of homeostasis is not achieved at parasitological cure.  The pathways required to restore homeostasis deserve fuller attention, to understand mechanisms associated with treatment failure and relapse and to promote more rapid restoration of immune competence.