In vitro antiproliferative effects and mechanism of action of the new triazole derivative UR-9825 against the protozoan parasite Trypanosoma (Schizotrypanum) cruzi

A functional assay using human whole blood and flow cytometry analysis to evaluate cytotoxicity and immunomodulatory effect of anti-Trypanosoma cruzi drugs

The discovery and development of new drugs for the treatment of Chagas disease is urgent due to the high toxicity and low cure efficacy, mainly during the chronic phase of this disease. Other chemotherapeutic approaches for Chagas disease treatment are being researched and require screening assays suitable for evaluating the effectivity of new biologically active compounds. This study aims to evaluate a functional assay using the internalization of epimastigotes forms of Trypanosoma cruzi by human peripheral blood leukocytes from healthy volunteers and analyses by flow cytometry of cytotoxicity, anti-T. cruzi activity, and immunomodulatory effect of benznidazole, ravuconazole, and posaconazole. The culture supernatant was used to measure cytokines (IL-1-β, IL-6, INF-γ, TNF and IL-10) and chemokines (MCP-1/CCL2, CCL5/RANTES and CXCL8/IL-8). The data showed a reduction in the internalization of T. cruzi epimastigote forms treated with ravuconazole, demonstrating its potential anti-T. cruzi activity. In addition, an increased amount of IL-10 and TNF cytokines was observed in the supernatant of cultures upon the addition of the drug, mainly IL-10 in the presence of benznidazole, ravuconazole and posaconazole, and TNF in the presence of ravuconazole and posaconazole. Moreover, the results revealed a decrease in the MCP-1/CCL2 index in cultures in the presence of benznidazole, ravuconazole, and posaconazole. A decrease in the CCL5/RANTES and CXCL8/IL-8 index in cultures with BZ, when compared to the culture without drugs, was also observed. In conclusion, the innovative functional test proposed in this study may be a valuable tool as a confirmatory test for selecting promising compounds identified in prospecting programs for new drugs for Chagas disease treatment.

Potential anti-acanthamoebic effects through inhibition of CYP51 by novel quinazolinones

Acanthamoeba spp. are free living amoebae which can give rise to Acanthamoeba keratitis and granulomatous amoebic encephalitis. The surface of Acanthamoeba contains ergosterol which is an important target for drug development against eukaryotic microorganisms. A library of ten functionally diverse quinazolinone derivatives (Q1-Q10) were synthesised to assess their activity against Acanthamoeba castellanii T4. The in-vitro effectiveness of these quinazolinones were investigated against Acanthamoeba castellanii by amoebicidal, excystation, host cell cytopathogenicity, and NADPH-cytochrome c reductase assays. Furthermore, wound healing capability was assessed at different time durations. Maximum inhibition at 50 μg/mL was recorded for compounds Q5, Q6 and Q8, while the compound Q3 did not exhibit amoebicidal effects at tested concentrations. Moreover, LDH assay was conducted to assess the cytotoxicity of quinazolinones against HaCaT cell line. The results of wound healing assay revealed that all compounds are not cytotoxic and are likely to promote wound healing at 10 μg/mL. The excystation assays revealed that these compounds significantly inhibit the morphological transformation of A. castellanii. Compound Q3, Q7 and Q8 elevated the level of NADPH-cytochrome c reductase up to five folds. Sterol 14alpha-demethylase (CYP51) a reference enzyme in ergosterol pathway was used as a potential target for anti-amoebic drugs. In this study using i-Tasser, the protein structure of Acanthamoeba castellanii (AcCYP51) was developed in comparison with Naegleria fowleri protein (NfCYP51) structure. The sequence alignment of both proteins has shown 42.72% identity. Compounds Q1-Q10 were then molecularly docked with the predicted AcCYP51. Out of ten quinazolinones, three compounds (Q3, Q7 and Q8) showed good binding activity within 3 Å of TYR 114. The in-silico study confirmed that these compounds are the inhibitor of CYP51 target site. This report presents several potential lead compounds belonging to quinazolinone derivatives for drug discovery against Acanthamoeba infections.

Nanotechnological interventions for treatment of trypanosomiasis in humans and animals

Trypanosomiasis is a parasitic infection caused by Trypanosoma. It is one of the major causes of deaths in underprivileged, rural areas of Africa, America and Asia. Depending on the parasite species responsible for the disease, it can take two forms namely African trypanosomiasis (sleeping sickness) and American trypanosomiasis (Chagas disease). The complete life-cycle stages of trypanosomes span between insect vector (tsetse fly, triatomine bug) and mammalian host (humans, animals). Only few drugs have been approved for the treatment of trypanosomiasis. Moreover, current trypanocidal therapy has major limitations of poor efficacy, serious side effects and drug resistance. Due to the lack of economic gains from tropical parasitic infection, it has always been neglected by the researchers and drug manufacturers. There is an immense need of more effective innovative strategies to decrease the deaths associated with this diseases. Nanotechnological approaches for delivery of existing drugs have shown significant improvement in efficacy with many-fold decrease in their dose. The review emphasizes on nanotechnological interventions in the treatment of trypanosomiasis in both humans and animals. Current trypanocidal therapy and their limitations have also been discussed briefly. Graphical abstract.

Nano-Medicines a Hope for Chagas Disease!

Chagas disease, is a vector-mediated tropical disease whose causative agent is a parasitic protozoan named Trypanosoma cruzi. It is a very severe health issue in South America and Mexico infecting millions of people every year. Protozoan T. cruzi gets transmitted to human through Triatominae, a subfamily of the Reduviidae, and do not have any effective treatment or preventative available. The lack of economic gains from this tropical parasitic infection, has always been the reason behind its negligence by researchers and drug manufacturers for many decades. Hence there is an enormous requirement for more efficient and novel strategies to reduce the fatality associated with these diseases. Even, available diagnosis protocols are outdated and inefficient and there is an urgent need for rapid high throughput diagnostics as well as management protocol. The current advancement of nanotechnology in the field of healthcare has generated hope for better management of many tropical diseases including Chagas disease. Nanoparticulate systems for drug delivery like poloxamer coated nanosuspension of benzimidazole have shown promising results in reducing toxicity, elevating efficacy and bioavailability of the active compound against the pathogen, by prolonging release, thereby increasing the therapeutic index. Moreover, nanoparticle-based drug delivery has shown promising results in inducing the host’s immune response against the pathogen with very few side effects. Besides, advances in diagnostic assays, such as nanosensors, aided in the accurate detection of the parasite. In this review, we provide an insight into the life cycle stages of the pathogen in both vertebrate host and the insect vector, along with an overview of the current therapy for Chagas disease and its limitations; nano carrier-based delivery systems for antichagasic agents, we also address the advancement of nano vaccines and nano-diagnostic techniques, for treatment of Chagas disease, majorly focusing on the novel perspectives in combating the disease.

Therapeutic progression of quinazolines as targeted chemotherapeutic agents

Presently cancer is a grave health issue with predominance beyond restrictions. It can affect any organ of the body. Most of the available chemotherapeutic drugs are highly toxic, not much selective and eventually lead to the development of resistance. Therefore, a target specific palliative approach for the treatment of cancer is required. Remarkable advancements in science have illuminated various molecular pathways responsible for cancer. This has resulted in abundant opportunities to develop targeted anticancer agents. Quinazoline nucleus is a privileged scaffold with significant diversified pharmacological activities. Numerous established anticancer quinazoline derivatives constitute a new class of chemotherapeutic agents which are found to act by inhibiting various protein kinases as well as other molecular targets. A recent update on various quinazoline derivatives acting on different types of molecular targets for the treatment of cancer has been compiled in this review. Brief SAR studies of quinazoline derivatives acting through different mechanisms of action have been highlighted. The comprehensive medicinal chemistry aspects of these agents in this review provide a panoramic view to the biologists as well as medicinal chemists working in this area and would assist them in their efforts to design and synthesize novel quinazoline based anticancer compounds.

Antileishmanial activity of 4-phenyl-1-[2-(phthalimido-2-yl)ethyl]-1H-1,2,3-triazole (PT4) derivative on Leishmania amazonensis and Leishmania braziliensis: In silico ADMET, in vitro activity, docking and molecular dynamic simulations

Organic compounds obtained by click chemistry reactions have demonstrated a broad spectrum of biological activities being widely applied for the development of molecules against pathogens of medical and veterinary importance. Cutaneous leishmaniasis (CL), caused by intracellular protozoa parasite of genus Leishmania, comprises a complex of clinical manifestations that affect the skin and mucous membranes. The available drugs for the treatment are toxic and costly, with long periods of treatment, and the emergence of resistant strains has been reported. In this study we investigated the in vitro effects of a phthalimide-1,2,3-triazole derivative, the 4-Phenyl-1-[2-(phthalimido-2-yl)ethyl]-1H-1,2,3-triazole (PT4) obtained by click chemistry, on mammalian cells and on L. amazonensis and L. braziliensis, the causative agents of CL in Brazil. In silico ADMET evaluation of PT4 showed that this molecule has good pharmacokinetic properties with no violation of Lipinski's rules. The in vitro assays showed that PT4 was more selective for both Leishmania species than to mammalian cells. This compound also presented low cytotoxicity to mammalian cells with CC₅₀ > 500 μM. Treatment of promastigote forms with different concentrations of PT4 resulted in ultrastructural alterations, such as plasma membrane wrinkling, shortening of cell body, increased cell volume and cell rupture. The molecular dynamic simulations showed that PT4 interacts with Lanosterol 14 α-demethylase from Leishmania, an essential enzyme of lipid synthesis pathway in this parasite. Our results demonstrated PT4 was effective against both species of Leishmania. PT4 caused a decrease of mitochondrial membrane potential and increased production of reactive oxygen species, which may lead to parasite death. Taken together, our results pointed PT4 as promissing therapeutic agent against CL.

Design, synthesis, molecular modelling, and in vitro evaluation of tricyclic coumarins against Trypanosoma cruzi

Chagas disease is caused by infection with the parasite protozoan Trypanosoma cruzi and affects about 8 million people in 21 countries in Latin America. The main form of treatment of this disease is still based on the use of two drugs, benznidazole and nifurtimox, which both present low cure rates in the chronic phase and often have serious side-effects. Herein, we describe the synthesis of tricyclic coumarins that were obtained via NHC organocatalysis and evaluation of their trypanocidal activity. Molecular docking studies against trypanosomal enzyme triosephosphate isomerase (TIM) were carried out, as well as a theoretical study of the physicochemical parameters. The tricyclic coumarins were tested in vitro against the intracellular forms of Trypanosoma cruzi. Among the 18 compounds tested, 10 were more active than the reference drug benznidazole. The trypanocidal activity of the lead compound was rationalized by molecular docking study which suggested the strong interaction with the enzyme TIM by T. cruzi and therefore indicating a possible mode of action. Furthermore, the selectivity index of eight tricyclic coumarins with high anti-T. cruzi activity was above 50 and thus showing that these lead compounds are viable candidates for further in vivo assays.

Searching for new drugs for Chagas diseases: triazole analogs display high in vitro activity against Trypanosoma cruzi and low toxicity toward mammalian cells

Chagas disease is one of the most relevant endemic diseases in Latin America caused by the flagellate protozoan Trypanosoma cruzi. Nifurtimox and benzonidazole are the drugs used in the treatment of this disease, but they commonly are toxic and present severe side effects. New effective molecules, without collateral effects, has promoted the investigation to develop new lead compounds with to advance for clinical trials. Previously, 3-nitro-1H-1,2,4-triazole-based amines and 1,2,3-triazoles demonstrated significant trypanocidal activity against T. cruzi. In this paper, we synthesized a new series of 92 examples of 1,2,3-triazoles. Six compounds exhibited antiparasitic activity, 14, 25, 27, 31 and 40, 43 and were effective against epimastigotes of two strains of T. cruzi (Y and Dm28-C) and 25, 27 and 31 exhibited trypanocidal activity similar to benzonidazole. Notably, the compound 25 compared to benzonidazole increase the toxicity against T. cruzi, with no apparent toxicity to the cell line of mice macrophages or primary mice peritoneal macrophages. As results, we calculated selectivity indexes up to 2000 to 25 and 31 in both T. cruzi strains. Derivative 14 caused a trypanostatic effect because it did not damage external epimastigote membrane. Triazoles 40 and 43 impaired parasites viability using a pathway not dependent on ROS production.

Experimental and Clinical Treatment of Chagas Disease: A Review

Chagas disease (CD) is caused by the protozoan parasite Trypanosoma cruzi that infects a broad range of triatomines and mammalian species, including man. It afflicts 8 million people in Latin America, and its incidence is increasing in nonendemic countries owing to rising international immigration and nonvectorial transmission routes such as blood donation. Since the 1960s, the only drugs available for the clinical treatment of this infection have been benznidazole (BZ) and nifurtimox (NFX). Treatment with these trypanocidal drugs is recommended in both the acute and chronic phases of CD. These drugs have low cure rates mainly during the chronic phase, in addition both drugs present side effects that may result in the interruption of the treatment. Thus, more efficient and better-tolerated new drugs or pharmaceutical formulations containing BZ or NFX are urgently needed. Here, we review the drugs currently used for CD chemotherapy, ongoing clinical assays, and most-promising new experimental drugs. In addition, the mechanism of action of the commercially available drugs, NFX and BZ, the biodistribution of the latter, and the potential for novel formulations of BZ based on nanotechnology are discussed. Taken together, the literature emphasizes the urgent need for new therapies for acute and chronic CD.

Development, validation and application of a GC-MS method for the simultaneous detection and quantification of neutral lipid species in Trypanosoma cruzi

The development and validation of an analytical method for the simultaneous analysis of five neutral lipids in Trypanosoma cruzi epimastigotes by GC-MS is presented in this study. The validated method meets all validation parameters for all components and the chromatographic conditions have been optimized during its development. This analytical method has demonstrated good selectivity, accuracy, within-day precision, recovery and linearity in each of the established ranges. In addition, detection and quantification limits for squalene, cholesterol, ergosterol and lanosterol have been improved and it is worth highlighting the fact that this is the first time that squalene-2,3-epoxide validation data have been reported. The new validated method has been applied to epimastigotes treated with compounds with in vitro anti-T.cruzi activity. This new methodology is straightforward and constitutes a tool for screening possible sterol biosynthesis pathway inhibitors in Trypanosoma cruzi, one of the most studied targets in Chagas disease treatment. Therefore, it is an interesting and useful contribution to medicinal chemistry research.

Novel drug discovery for Chagas disease

INTRODUCTION

Chagas disease is a chronic infection associated with long-term morbidity. Increased funding and advocacy for drug discovery for neglected diseases have prompted the introduction of several important technological advances, and Chagas disease is among the neglected conditions that has mostly benefited from technological developments. A number of screening campaigns, and the development of new and improved in vitro and in vivo assays, has led to advances in the field of drug discovery.

AREAS COVERED

This review highlights the major advances in Chagas disease drug screening, and how these are being used not only to discover novel chemical entities and drug candidates, but also increase our knowledge about the disease and the parasite. Different methodologies used for compound screening and prioritization are discussed, as well as novel techniques for the investigation of these targets. The molecular mechanism of action is also discussed.

EXPERT OPINION

Technological advances have been executed with scientific rigour for the development of new in vitro cell-based assays and in vivo animal models, to bring about novel and better drugs for Chagas disease, as well as to increase our understanding of what are the necessary properties for a compound to be successful in the clinic. The gained knowledge, combined with new exciting approaches toward target deconvolution, will help identifying new targets for Chagas disease chemotherapy in the future.

Trypanosoma cruzi response to sterol biosynthesis inhibitors: morphophysiological alterations leading to cell death

The protozoan parasite Trypanosoma cruzi displays similarities to fungi in terms of its sterol lipid biosynthesis, as ergosterol and other 24-alkylated sterols are its principal endogenous sterols. The sterol pathway is thus a potential drug target for the treatment of Chagas disease. We describe here a comparative study of the growth inhibition, ultrastructural and physiological changes leading to the death of T. cruzi cells following treatment with the sterol biosynthesis inhibitors (SBIs) ketoconazole and lovastatin. We first calculated the drug concentration inhibiting epimastigote growth by 50% (EC(50)/72 h) or killing all cells within 24 hours (EC(100)/24 h). Incubation with inhibitors at the EC(50)/72 h resulted in interesting morphological changes: intense proliferation of the inner mitochondrial membrane, which was corroborated by flow cytometry and confocal microscopy of the parasites stained with rhodamine 123, and strong swelling of the reservosomes, which was confirmed by acridine orange staining. These changes to the mitochondria and reservosomes may reflect the involvement of these organelles in ergosterol biosynthesis or the progressive autophagic process culminating in cell lysis after 6 to 7 days of treatment with SBIs at the EC(50)/72 h. By contrast, treatment with SBIs at the EC(100)/24 h resulted in rapid cell death with a necrotic phenotype: time-dependent cytosolic calcium overload, mitochondrial depolarization and reservosome membrane permeabilization (RMP), culminating in cell lysis after a few hours of drug exposure. We provide the first demonstration that RMP constitutes the "point of no return" in the cell death cascade, and propose a model for the necrotic cell death of T. cruzi. Thus, SBIs trigger cell death by different mechanisms, depending on the dose used, in T. cruzi. These findings shed new light on ergosterol biosynthesis and the mechanisms of programmed cell death in this ancient protozoan parasite.

VNI cures acute and chronic experimental Chagas disease

Chagas disease is a deadly infection caused by the protozoan parasite Trypanosoma cruzi. Afflicting approximately 8 million people in Latin America, Chagas disease is now becoming a serious global health problem proliferating beyond the traditional geographical borders, mainly because of human and vector migration. Because the disease is endemic in low-resource areas, industrial drug development has been lethargic. The chronic form remains incurable, there are no vaccines, and 2 existing drugs for the acute form are toxic and have low efficacy. Here we report the efficacy of a small molecule, VNI, including evidence of its effectiveness against chronic Chagas disease. VNI is a potent experimental inhibitor of T. cruzi sterol 14α-demethylase. Nontoxic and highly selective, VNI displays promising pharmacokinetics and administered orally to mice at 25 mg/kg for 30 days cures, with 100% cure rate and 100% survival, the acute and chronic T. cruzi infection.

Chagas disease. What is known and what should be improved: a systemic review

This study consists of a broad review on what is known and what should be improved regarding knowledge of Chagas disease, not only through analysis on the main studies published on the topics discussed, but to a large extent based on experience of this subject, acquired over the past 50 years (1961-2011). Among the subjects covered, we highlight the pathogenesis and evolution of infection by Trypanosoma cruzi, drugs in use and new strategies for treating Chagas disease; the serological tests for the diagnosis and the controls of cure the infection; the regional variations in prevalence, morbidity and response to treatment of the disease; the importance of metacyclogenesis of T. cruzi in different species of triatomines and its capacity to transmit Chagas infection; the risks of adaptation of wild triatomines to human dwellings; the morbidity and need for a surveillance and control program for Chagas disease in the Amazon region and the need to prioritize initiatives for controlling Chagas disease in Latin America and Mexico and in non-endemic countries, which is today a major international dilemma. Finally, we raise the need for to create a new initiative for controlling Chagas disease in the Gran Chaco, which involves parts of Argentina, Bolivia and Paraguay.

In vitro and in vivo trypanocidal activity of some benzimidazole derivatives against two strains of Trypanosoma cruzi

The trypanocidal effect of five benzimidazole derivatives (1-5) was determined in vitro and in vivo assays against two strains of Trypanosoma cruzi (NINOA and INC5). The in vitro trypanocidal activity was evaluated by measuring the percentage of lysis of bloodstream trypomastigotes of T. cruzi. Results point to 5-chloro-1H-benzimidazole-2-thiol (1) as the best activity profile compound with a 50% lytic concentration (LC(50)) of 0.014 mM (NINOA strain) and 0.32 mM (INC5 strain). Reference drugs were nifurtimox (Nfx) and benznidazole (Bnz), which on NINOA strain displayed a LC(50)=0.60 mM and LC(50)=0.78 mM, respectively; while on INC5 strain they exhibited LC(50) values of 0.31 mM and 0.69 mM, respectively. The in vivo trypanocidal activity of 1-5 on parasitemia in a murine model acute Chagas' disease indicated that 1 and Nfx showed similar activity on INC5 strain, while 5-chloro-1-methyl-1H-benzimidazole-2-thiol (2) and its regioisomer, 6-chloro-1-methyl-1H-benzimidazole-2-thiol (3), displayed better activity than Nfx and Bnz on NINOA strain. All compounds showed low cytotoxicity against Vero cells, with selective index 38-3000 times higher to the parasite.

Targeting Trypanosoma cruzi sterol 14α-demethylase (CYP51)

There are at least two obvious features that must be considered upon targeting specific metabolic pathways/enzymes for drug development: the pathway must be essential and the enzyme must allow the design of pharmacologically useful inhibitors. Here, we describe Trypanosoma cruzi sterol 14α-demethylase as a promising target for anti-Chagasic chemotherapy. The use of anti-fungal azoles, which block sterol biosynthesis and therefore membrane formation in fungi, against the protozoan parasite has turned out to be highly successful: a broad spectrum anti-fungal drug, the triazole compound posaconazole, is now entering phase II clinical trials for treatment of Chagas disease. This review summarizes comparative information on anti-fungal azoles and novel inhibitory scaffolds selective for Trypanosomatidae sterol 14α-demethylase through the lens of recent structure/functional characterization of the target enzyme. We believe our studies open wide opportunities for rational design of novel, pathogen-specific and therefore more potent and efficient anti-trypanosomal drugs.

Specific chemotherapy of Chagas disease: relevance, current limitations and new approaches

A critical review of the development of specific chemotherapeutic approaches for the management of American Trypanosomiasis or Chagas disease is presented, including controversies on the pathogenesis of the disease, the initial efforts that led to the development of currently available drugs (nifurtimox and benznidazole), limitations of these therapies and novel approaches for the development of anti-Trypanosoma cruzi drugs, based on our growing understanding of the biology of this parasite. Among the later, the most promising approaches are ergosterol biosynthesis inhibitors such as posaconazole and ravuconazole, poised to enter clinical trials for chronic Chagas disease in the short term; inhibitors of cruzipain, the main cysteine protease of T. cruzi, essential for its survival and proliferation in vitro and in vivo; bisphosphonates, metabolic stable pyrophosphate analogs that have trypanocidal activity through the inhibition of the parasite's farnesyl-pyrophosphate synthase or hexokinase; inhibitors of trypanothione synthesis and redox metabolism and inhibitors of hypoxanthine-guanine phosphoribosyl-transferase, an essential enzyme for purine salvage in T. cruzi and related organisms. Finally, the economic and political challenges faced by development of drugs for the treatment of neglected tropical diseases, which afflict almost exclusively poor populations in developing countries, are analyzed and recent potential solutions for this conundrum are discussed.

Synthetic Medicinal Chemistry in Chagas' Disease: Compounds at The Final Stage of "Hit-To-Lead" Phase

Chagas' disease, or American trypanosomosiasis, has been the most relevant illness produced by protozoa in Latin America. Synthetic medicinal chemistry efforts have provided an extensive number of chemodiverse hits at the "active-to-hit" stage. However, only a more limited number of these have been studied in vivo in models of Chagas' disease. Herein, we survey some of the cantidates able to surpass the "hit-to-lead" stage discussing their limitations or merit to enter in clinical trials in the short term.

Nanotechnological approaches against Chagas disease

Over several thousand years, the flagellated Trypanosome cruzi-causative agent of Chagas disease-developed a complex life cycle between the reduviidae vectors and its human hosts. Due to their silent and hidden location, the intracellular amastigotes are mainly responsible for the nearly 50,000 annual deaths caused by the chronic chagasic cardiomyopathy. Chagas disease is the most important parasitic disease in the Americas, though treatments have not evolved towards a more efficient pharmacotherapy that (i) eradicates the scarce amastigotes present at the indeterminate/chronic form and (ii) employs less toxic drugs than benznidazole or nifurtimox. Nano-drug delivery systems (nanoDDS) represent useful means to selectively deliver the drug to intracellular targets. However, preclinical research in Chagas must be extended in order to improve the chances of a clinical implementation. The stages involved in this process are (i) selection of the appropriate drug for a specific parasite, (ii) development of a drug-loaded nanoDDS structure that displays the adequate pharmacokinetics, biodistribution and intracellular transit and (iii) selection of the right parasite form to target and the right stage of the disease for the treatment to be started. In this review we will critically overview the few research works published in the last 20years in the context of nanotechnology and Chagas diseases and highlight the gaps in knowledge towards the design of more efficient medicines to address this endemic.

Ergosterol biosynthesis and drug development for Chagas disease

This article presents an overview of the currently available drugs nifurtimox (NFX) and benznidazole (BZN) used against Trypanosoma cruzi, the aetiological agent of Chagas disease; herein we discuss their limitations along with potential alternatives with a focus on ergosterol biosynthesis inhibitors (EBI). These compounds are currently the most advanced candidates for new anti-T. cruzi agents given that they block de novo production of 24-alkyl-sterols, which are essential for parasite survival and cannot be replaced by a host's own cholesterol. Among these compounds, new triazole derivatives that inhibit the parasite's C14alpha sterol demethylase are the most promising, as they have been shown to have curative activity in murine models of acute and chronic Chagas disease and are active against NFX and BZN-resistant T. cruzi strains; among this class of compounds, posaconazole (Schering-Plough Research Institute) and ravuconazole (Eisai Company) are poised for clinical trials in Chagas disease patients in the short term. Other T. cruzi-specific EBI, with in vitro and in vivo potency, include squalene synthase, lanosterol synthase and squalene epoxidase-inhibitors as well as compounds with dual mechanisms of action (ergosterol biosynthesis inhibition and free radical generation), but they are less advanced in their development process. The main putative advantages of EBI over currently available therapies include their higher potency and selectivity in both acute and chronic infections, activity against NFX and BZN-resistant T. cruzi strains, and much better tolerability and safety profiles. Limitations may include complexity and cost of manufacture of the new compounds. As for any new drug, such compounds will require extensive clinical testing before being introduced for clinical use, and the complexity of such studies, particularly in chronic patients, will be compounded by the current limitations in the verification of true parasitological cures for T. cruzi infections.

New triazoles and echinocandins: mode of action, in vitro activity and mechanisms of resistance

Different types of mycoses, especially invasive mycoses caused by yeasts and molds, are a growing problem in healthcare. The most notable explanation for this increase is a rise in the number of immunocompromised patients owing to advances in transplantation, the emergence of AIDS and a rise in the number of invasive surgical procedures. Despite advances in medical practice, some therapeutic problems remain. In addition, intrinsic or acquired antifungal resistance may pose a serious problem to antifungal therapy. A new generation of triazole agents (voriconazole, posaconazole, isavuconazole, ravuconazole and albaconazole) and the recent class of the echinocandins (caspofungin, micafungin and anidulafungin) have become available, and represent an alternative to conventional antifungals for serious fungal infection management. Currently, only two of the recent triazole generation (voriconazole and posaconazole) and all three echinocandins are available for clinical use. More precisely, voriconazole and posaconazole are indicated for the treatment of invasive fungal infections and the echinocandins for the treatment of specific candidiasis. Voriconazole and posaconazole have a very broad spectrum of antifungal activity that includes Candida species, and filamentous and dimorphic fungi. Their activity extends to both fluconazole- and itraconazole-resistant strains of Candida. A major difference between posaconazole and voriconazole is that posaconazole has activity against Zygomycetes including Mucor spp., Rhizopus spp. and Cunninghamella spp., and voriconazole has no activity against this class of fungi. Ravuconazole, isavuconazole and albaconazole have shown very potent in vitro activity against species of Candida, Cryptococcus and Aspergillus, and they are currently in various stages of development. All three echinocandin agents, caspofungin, micafungin and anidulafungin, are similar in their spectrum of activity. Echinocandins do not possess in vitro activity against important basidiomycetes, including Cryptococcus, Rhodotorula and Trichosporon. This review attempts to deliver the most up-to-date knowledge on the mode of action and mechanisms of resistance to triazoles and echinocandins in fungal pathogens. In addition, the in vitro activity data available on triazoles and echinocandins are reported.

Efficacy of albaconazole against Candida albicans in a vaginitis model

The efficacy of albaconazole (ABC) was evaluated using a murine model of vaginal Candida albicans infection. Both ABC and fluconazole (FLC) were effective in reducing the fungal load from vaginas of infected mice; however, ABC demonstrated encouraging activities against an FLC-resistant strain, with trends toward superiority over FLC in some treatment groups.

Biological activity of 1,2,3,4-tetrahydro-beta-carboline-3-carboxamides against Trypanosoma cruzi

Several beta-carboline compounds were evaluated for in vitro trypanocidal activity against Trypanosoma cruzi and their potential toxic effects was also assessed. beta-Carboline derivative 4 showed good activity against epimastigote, trypomastigote, and amastigote forms of T. cruzi, with a dose-dependent inhibitory effect. It showed an IC(50) of 14.9 microM against the epimastigote form and an EC(50) of 45 microM and 33 microM against trypomastigote and amastigote forms, respectively. Additionally, 4 was able to be active on mammalian cell-protozoan interaction, reducing the number of infected cells and the number of internalized parasites. The compound showed low cytotoxicity, with a selective index 31 times higher to the parasite than for mammalian cells. In human red-blood cells beta-Carboline 4 at 14.9 microM not caused haemolysis. Observed at electron microscopy 4-treated epimastigotes showed abnormal swelling of the mitochondrion, a diffuse kinetoplast, and distortions of the parasite cell body. The present data support the potential effect of this class of compounds against T. cruzi and encourage further experiments in vitro to evaluate the action mechanism of this drug and also with in vivo models.

Sterol 14-demethylase inhibitors for Trypanosoma cruzi infections

Chagas disease is caused by infection with the protozoan pathogen, Trypanosoma cruzi. The only approved therapeutics for treating Chagas disease are two nitroheterocyclic compounds (benznidazole and nifurtimox) that are suboptimal due to poor curative activity for chronic Chagas disease and high rates of adverse drug reactions. Sterol 14-demethylase inhibitors include azole antifungal drugs such as ketoconazole, fluconazole, itraconazole, and others. The first reports of potent activity of azole antifungal drugs against Trypanosoma cruzi came out about 25 years ago. Since then, a sizeable literature has accumulated on this topic. Newer triazole compounds such as posaconazole and D0870 have been shown to be effective at curing mice with chronic Trypanosoma cruzi infection. Small clinical studies with-ketoconazole or itraconazole in humans with chronic Chagas disease have not demonstrated significant curative activity. However, there is good reason for optimism that newer compounds with greater potency and improved pharmacokinetic properties might be more efficacious. Data have been published demonstrating synergistic activity of azole drugs with various other compounds, indicating that combination chemotherapy may be an effective strategy as this field moves ahead. In light of the near absence of adequate therapeutics for curing patients with chronic Chagas disease, additional effort to develop better drugs needs to be a priority.

Quinuclidine derivatives as potential antiparasitics

There is an urgent need for the development of new drugs for the treatment of tropical parasitic diseases such as Chagas' disease and leishmaniasis. One potential drug target in the organisms that cause these diseases is sterol biosynthesis. This paper describes the design and synthesis of quinuclidine derivatives as potential inhibitors of a key enzyme in sterol biosynthesis, squalene synthase (SQS). A number of compounds that were inhibitors of the recombinant Leishmania major SQS at submicromolar concentrations were discovered. Some of these compounds were also selective for the parasite enzyme rather than the homologous human enzyme. The compounds inhibited the growth of and sterol biosynthesis in Leishmania parasites. In addition, we identified other quinuclidine derivatives that inhibit the growth of Trypanosoma brucei (the causative organism of human African trypanosomiasis) and Plasmodium falciparum (a causative agent of malaria), but through an unknown mode(s) of action.

Trypanosoma cruzi: in vitro and in vivo antiproliferative effects of epigallocatechin gallate (EGCg)

The trypanocidal activity of catechins on Trypanosoma cruzi bloodstream trypomastigotes has been previously reported. Herein, we present the effect of epigallocatechin gallate (EGCg) on parasitemia and survival in a murine model of acute Chagas' disease as well as on the epimastigote form of the parasite. Upon intraperitoneal administration of daily doses of 0.8 mg/kg/day of EGCg for 45 days, mice survival rates increased from 11% to 60%, while parasitemia diminished to 50%. No side effects were observed in EGCg-treated animals. Fifty percent inhibition of epimastigotes growth was achieved with 311 microM EGCg 120 h after drug addition. No lysis, total culture growth inhibition or morphological changes were observed upon addition of 1-3mM EGCg at 24 h. This treatment also produced oligosomal fragmentation of epimastigotes DNA, suggesting a programmed cell death (PCD)-like process. All these findings point out EGCg as a potential new lead compound for chemotherapy of Chagas' disease.

The Anti-Trypanosoma cruzi activity of posaconazole in a murine model of acute Chagas' disease is less dependent on gamma interferon than that of benznidazole

We have investigated the influences of gamma interferon (IFN-gamma) and interleukin-12 (IL-12) on the efficacy of posaconazole (POS) treatment of acute experimental infections with Trypanosoma cruzi; the standard drug, benznidazole (BZ), was used as a positive control. Wild-type (WT) mice infected with T. cruzi and treated with POS or BZ had no parasitemia, 100% survival, and cure rates of 86 to 89%. IFN-gamma-knockout (KO) mice infected with T. cruzi and treated with BZ controlled the infection during treatment but relapsed after the drug pressure ceased and had 0% survival, while those receiving POS better controlled the infection after the end of treatment and had 70% survival (P<0.0001 compared to the results for both untreated and BZ-treated animals). IL-12-KO mice infected and treated with POS or BZ had intermediate results, displaying enhanced parasitemia, decreased survival (77 to 83%), and reduced cure rates (35 to 39%) compared with those of the WT animals. Our results demonstrate that either IFN-gamma or IL-12 deficiency reduces the efficacy of POS or BZ in this experimental model but also indicate that the anti-T. cruzi activity of POS is much less dependent on the activity of IFN-gamma than that of BZ is.

Novel antitrypanosomal agents

Trypanosomes are the causative agents of Chagas' disease in Central and South America and sleeping sickness in sub-Saharan Africa. The current chemotherapy of the human trypanosomiases relies on only six drugs, five of which were developed > 30 years ago. In addition, these drugs display undesirable toxic side effects and the emergence of drug-resistant trypanosomes has been reported. Therefore, the development of new drugs in the treatment of Chagas' disease and sleeping sickness is urgently required. This article summarises the recent progress in identifying novel lead compounds for antitrypanosomal chemotherapy. Particular emphasis is placed on those agents showing promising, selective antitrypanosomal activity.

Lipophilic antifolate trimetrexate is a potent inhibitor of Trypanosoma cruzi: prospect for chemotherapy of Chagas' disease

Trypanosoma cruzi, a protozoan parasite, is the causative agent for Chagas' disease, which poses serious public health problem in Latin America. The two drugs available for the treatment of this disease are effective only against recent infections and are toxic. Dihydrofolate reductase (DHFR) has a proven track record as a drug target. The lipophilic antifolate trimetrexate (TMQ), which is an FDA-approved drug for the treatment of Pneumocystis carinii infection in AIDS patients, is a potent inhibitor of T. cruzi DHFR activity, with an inhibitory constant of 6.6 nM. The compound is also highly effective in killing T. cruzi parasites. The 50 and 90% lethal dose values against the trypomastigote are 19 and 36 nM, and the corresponding values for the amastigote form are 26 and 72 nM, respectively. However, as TMQ is also a good inhibitor of human DHFR, further improvement of the selectivity of this drug would be preferable. Identification of a novel antifolate selective against T. cruzi would open up new therapeutic avenues for treatment of Chagas' disease.

Biphenylquinuclidines as inhibitors of squalene synthase and growth of parasitic protozoa

In this paper we describe the preparation of some biphenylquinuclidine derivatives and their evaluation as inhibitors of squalene synthase in order to explore their potential in the treatment of the parasitic diseases leishmaniasis and Chagas disease. The compounds were screened against recombinant Leishmania major squalene synthase and against Leishmania mexicana promastigotes, Leishmania donovani intracellular amastigotes and Trypanosoma cruzi intracellular amastigotes. Compounds that inhibited the enzyme, also reduced the levels of steroids and caused growth inhibition of L. mexicana promastigotes. However there was a lower correlation between inhibition of the enzyme and growth inhibition of the intracellular parasites, possibly due to delivery problems. Some compounds also showed growth inhibition of T. brucei rhodesiense trypomastigotes, although in this case alternative modes of action other than inhibition of SQS are probably involved.

Activity of the new triazole derivative albaconazole against Trypanosoma (Schizotrypanum) cruzi in dog hosts

Albaconazole is an experimental triazole derivative with potent and broad-spectrum antifungal activity and a remarkably long half-life in dogs, monkeys, and humans. In the present work, we investigated the in vivo activity of this compound against two strains of the protozoan parasite Trypanosoma (Schizotrypanum) cruzi, the causative agent of Chagas' disease, using dogs as hosts. The T. cruzi strains used in the study were previously characterized (murine model) as susceptible (strain Berenice-78) and partially resistant (strain Y) to the drugs currently in clinical use, nifurtimox and benznidazole. Our results demonstrated that albaconazole is very effective in suppressing the proliferation of the parasite and preventing the death of infected animals. Furthermore, the parasitological, PCR, serological, and proliferative assay results indicated parasitological cure indices of 25 and 100% among animals inoculated with T. cruzi strain Y when they were treated with albaconazole at 1.5 mg/kg of body weight/day for 60 and 90 days, respectively. On the other hand, although albaconazole given at 1.5 mg/kg/day was very effective in suppressing the proliferation of the parasite in animals infected with the Berenice-78 T. cruzi strain, no parasitological cure was observed among them, even when a longer treatment period (150 doses) was used. In conclusion, our results demonstrate that albaconazole has trypanocidal activity in vivo and is capable of inducing radical parasitological cure, although natural resistance to this compound was also indicated. Furthermore, the compound can be used in long-term treatment schemes (60 to 150 days) with minimal toxicity and thus represents a potentially useful candidate for the treatment of human Chagas' disease.

The glycosome membrane of Trypanosoma cruzi epimastigotes: protein and lipid composition

Highly purified glycosomes from Trypanosoma cruzi epimastigotes were obtained by differential centrifugation and isopycnic ultracentrifugation. Glycosomal membranes, produced by carbonate treatment of purified glycosomes, exhibited about eight main protein bands and eight minor ones. Essentially the same protein pattern was observed in the detergent-rich fraction of a Triton X-114 fractionation of whole glycosomes, indicating that most of the membrane-bound polypeptides were highly hydrophobic. The orientation of these proteins was studied by in situ labelling followed by limited pronase hydrolysis of intact glycosomes. Three glycosome membrane proteins were characterized as peripheral by comparing the protein bands patterns of membrane fractions obtained by different treatments. Noteworthy membrane polypeptides were: (1) a peripheral 75k Da membrane protein, oriented towards the cytosol, which was the most abundant glycosomal membrane protein in exponentially growing epimastigotes but was essentially absent in stationary phase cells; (2) a pair of integral membrane proteins with molecular masses in the range of 85-100 kDa, which were only present in stationary phase cells; (3) a heme-containing 36k Da protein, strongly associated to the membrane, present in both growth phases; (4) a very immunogenic 41k Da integral membrane polypeptide, oriented towards the cytosol. The lipid composition of the glycosomal membranes was also investigated. The distribution of phospholipid species in glycosomes and glycosomal membranes was very similar to that of whole cells, with phosphatidyl-ethanolamine, phosphatidyl-choline, and phosphatidyl-serine as main components and smaller proportions of sphingomyelin and with phosphatidyl-inositol. On the other hand, glycosomes were enriched in endogenous sterols (ergosterol, 24-ethyl-5,7,22-cholesta-trien-3beta-ol), and precursors, when compared with whole cells, a finding consistent with the proposal that these organelles are involved in the de novo biosynthesis of sterols in trypanosomatids.

Inhibition of in vitro intracellular growth of Trypanosoma cruzi by dicationic compounds

Dicationic compounds, which are derivatives of pentamidine, are being developed for use as antiprotozoal drugs. These compounds bind to the minor groove of DNA and are thought to inhibit DNA-dependent enzymes and thereby prevent cellular replication by protozoans. The objective of this study was to test the ability of a group of these compounds to inhibit the intracellular and extracellular reproduction of Trypanosoma cruzi in vitro. At present, there are few drugs in use capable of inhibiting the intracellular stages of this parasite, and therefore compounds with this ability would be of value. Cultures of mouse fibroblasts were infected and treated with doses of dicationic compounds, and the numbers of parasites released at the end of the 5- to 7-day growth cycle were determined. Five of the compounds tested were found to be effective at inhibiting T. cruzi growth at doses that were not toxic to the host cells. The compound found most effective (DB709) inhibited parasite release at the low concentration of 0.8 ng/ ml, justifying further study. These results suggest that dicationic compounds may have potential as chemotherapy against T. cruzi infection.

Fatty acid and sterol metabolism: potential antimicrobial targets in apicomplexan and trypanosomatid parasitic protozoa

Current treatments for diseases caused by apicomplexan and trypanosomatid parasites are inadequate due to toxicity, the development of drug resistance and an inability to eliminate all life cycle stages of these parasites from the host. New therapeutics agents are urgently required. It has recently been demonstrated that type II fatty acid biosynthesis occurs in the plastid of Plasmodium falciparum and Toxoplasma gondii and inhibitors of this pathway such as triclosan and thiolactomycin restrict their growth. Furthermore, Trypanosoma brucei has recently been demonstrated to use type II fatty acid biosynthesis for myristate synthesis and to be susceptible to thiolactomycin. As this pathway is absent from mammals, it may provide an excellent target for novel antimicrobial agents to combat these diverse parasites. Leishmania and Trypanosoma parasites produce ergosterol-related sterols by a biosynthetic pathway similar to that operating in pathogenic fungi and their growth is susceptible to sterol biosynthesis inhibitors. Thus, inhibition of squalene 2,3-epoxidase by terbinafine, 14alpha-methylsterol 14-demethylase by azole and triazole compounds and delta(24)-sterol methyl transferase by azasterols all cause a depletion of normal sterols and an accumulation of abnormal amounts of sterol precursors with cytostatic or cytoxic consequences. However, Leishmania parasites can survive with greatly altered sterol profiles induced by continuous treatment with low concentrations of some inhibitors and they also have some ability to utilise and metabolise host sterol. These properties may permit the parasites to evade treatment with sterol biosynthesis inhibitors in some clinical situations and need to be taken into account in the design of future drugs.

Parasitological cure of acute and chronic experimental Chagas disease using the long-acting experimental triazole TAK-187. Activity against drug-resistant Trypanosoma cruzi strains

We investigated the activity of TAK-187, an experimental antifungal triazole with a long terminal half-life in several experimental animals, against Trypanosoma cruzi. In vitro studies showed that the minimal inhibitory concentration (MIC) against the (extracellular) epimastigote form was 0.3-1 microM, while the corresponding concentration against clinically relevant intracellular amastigotes was 1 nM. At the MIC the endogenous epimastigote C4,14-desmethyl sterols were replaced by di- and tri-methylated sterols, supporting the notion that the primary target of TAK-187 is the parasite's sterol C14alpha demethylase. We investigated the in vivo activity of the compound in a murine model of acute Chagas disease, using T. cruzi strains with different susceptibilities to the drugs currently used clinically (nitrofurans and nitroimidazoles). It was found that TAK-187 given orally at 20 mg/kg induced complete protection against death and high levels (60-100%) of parasitological cures, independently of the infecting strain and even when administered every other day (e.o.d.), consistent with its long terminal half-life in mice. Other experiments, using longer treatment periods were carried out in both acute and chronic models of the disease and showed that TAK-187 given at 10-20 mg/kg e.o.d. induced 80-100% survival with 80-100% of parasitological cures of survivors in both models. No toxic side effects were observed in any of the experimental protocols. TAK-187 is a potent anti-T. cruzi compound with trypanocidal activity in vivo and should be considered for further studies as a potential specific treatment of human Chagas disease.

In vitro and in vivo activities of ravuconazole on Trypanosoma cruzi, the causative agent of Chagas disease

Ravuconazole is an experimental triazole derivative with potent and broad-spectrum antifungal activity and a remarkably long half-life in humans. In this work, we investigated the in vitro and in vivo activities of this compound against Trypanosoma cruzi. Ravuconazole showed very potent in vitro anti-T. cruzi activity with minimal inhibitory concentrations (MIC) of 300 and 1 nM against the extracellular epimastigote and intracellular amastigote forms, respectively. As with other azole derivatives, ravuconazole at the MIC led to an essentially complete depletion of the epimastigotes' endogenous C4,14-desmethyl sterols and their replacement by di- and tri-methylated sterols. In murine acute models of acute Chagas disease, it was found that ravuconazole treatment led to high levels of parasitological cures, but only when given twice a day (b.i.d.), consistent with its short terminal half-life in mice (4 h). Furthermore, it was found that this curative activity was restricted towards nitrofuran/nitroimidazole-susceptible (CL) and partially drug-resistant (Y) strains of T. cruzi, with no curative activity in animals infected with the fully drug-resistant Colombiana strain. No curative activity occurred in a chronic model of the disease. No toxic side effects were observed resulting from treatment with the triazole. Ravuconazole is a very potent and specific anti-T. cruzi agent in vitro but its in vivo activity in mice is limited, probably due to its unfavourable pharmacokinetic properties in this animal model. However, these results do not necessarily rule out the potential utility of ravuconazole in the treatment of human T. cruzi infections.

Cytotoxic and genotoxic effects of megazol, an anti-Chagas' disease drug, assessed by different short-term tests

Cyto- and genotoxicity induced by drugs can limit the dose and duration of treatment, can adversely affect patient quality of life, and may be life-threatening. Two drugs are currently being used for treatment of the acute phase of Chagas' disease and both have serious undesirable effects. In this research, cyto- and genotoxic activity of the nitroimidazole-tiadiazole derivative CL 64855 2-amino-5-(1-methyl-5-nitro-2-imidazolyl)-1,3,4-thiadiazole (megazol), a promising alternative drug, was evaluated in vitro with different short-term tests: (a) induction of recombination events and mutation in the yeast Saccharomyces cerevisiae D7 strain, with and without induction of cytochrome P-450; DNA damage (single and double strand breaks, alkali-labile sites, etc.) by the Comet assay in different mammalian cells. S. cerevisiae did not show a significant increase of mutant and recombinant event frequency, both with and without cytochrome P-450. On the other hand, the cytochrome complex appeared to detoxify the drug with respect to cytotoxicity. Results in rat and mouse fresh leukocytes showed a dose-response relation of drug-induced DNA damage. Findings in treated VERO cells suggested a complex treatment time-DNA damage relationship and the possible induction of repair mechanisms. Furthermore, bleomycin effects were increased in rat cells by simultaneous administration of megazol. Megazol shows different biological activity in relation to cellular types and experimental conditions (with or without cytochrome P-450, short/long time of exposure, with or without other genotoxins), thus suggesting a modulation of effectiveness by different physiological/biochemical conditions of cells. The findings could be useful to evaluate new megazol-derived compounds and to assess the risks/benefits relationship for each drug.

A critical review on Chagas disease chemotherapy

In this "Critical Review" we made a historical introduction of drugs assayed against Chagas disease beginning in 1912 with the works of Mayer and Rocha Lima up to the experimental use of nitrofurazone. In the beginning of the 70s, nifurtimox and benznidazole were introduced for clinical treatment, but results showed a great variability and there is still a controversy about their use for chronic cases. After the introduction of these nitroheterocycles only a few compounds were assayed in chagasic patients. The great advances in vector control in the South Cone countries, and the demonstration of parasite in chronic patients indicated the urgency to discuss the etiologic treatment during this phase, reinforcing the need to find drugs with more efficacy and less toxicity. We also review potential targets in the parasite and present a survey about new classes of synthetic and natural compounds studied after 1992/1993, with which we intend to give to the reader a general view about experimental studies in the area of the chemotherapy of Chagas disease, complementing the previous papers of Brener (1979) and De Castro (1993).

Specific treatment of Chagas disease: current status and new developments

The current situation regarding specific chemotherapy for Chagas disease (American trypanosomiasis), and new developments in this field, are reviewed. Despite previous controversy on the autoimmune origin of Chagas disease pathology, available knowledge supports the notion that this condition should be treated as a parasitic, not an autoimmune, disease. Currently available drugs (nitrofurans and nitroimidazoles) are active in acute or short-term chronic infections, but have very low antiparasitic activity against the prevalent chronic form of the disease, and toxic side-effects are frequently encountered. The nitroimidazole benznidazole has also shown significant activity in the treatment of reactivated Trypanosoma cruzi infections in patients with acquired immune deficiency syndrome and in other immunosuppressed patients with underlying chronic Chagas disease. Although the etiological agent, T. (Schizotrypanum) cruzi, requires specific endogenous sterols for cell viability and proliferation, the currently available antifungal sterol biosynthesis inhibitors are not powerful enough to induce parasitological cures of human or experimental infections. However, new triazole antifungal compounds, which are potent inhibitors of the sterol C14alpha demethylase of the parasite and have special pharmacokinetic properties, are capable of inducing parasitological cures in murine models of both acute and chronic Chagas disease. They are currently the most advanced candidates for clinical trials in patients with Chagas disease. Other potential chemotherapeutic agents against T. cruzi currently in development include antiproliferative lysophospholipid analogs (already in clinical trials as the first oral treatment for visceral leishmaniasis), cysteine proteinase (cruzipain) inhibitors, and compounds that interfere with purine salvage and inositol metabolism.