Recent Developments in Sterol 14-demethylase Inhibitors for Chagas Disease

Nanomedicines against Chagas disease: an update on therapeutics, prophylaxis and diagnosis

Chagas disease is a neglected parasitic infection caused by the protozoan Trypanosoma cruzi. After a mostly clinically silent acute phase, the disease becomes a lifelong chronic condition that can lead to chronic heart failure and thromboembolic phenomena followed by sudden death. Antichagasic treatment is only effective in the acute phase but fails to eradicate the intracellular form of parasites and causes severe toxicity in adults. Although conventional oral benznidazol is not a safe and efficient drug to cure chronic adult patients, current preclinical data is insufficient to envisage if conventional antichagasic treatment could be realistically improved by a nanomedical approach. This review will discuss how nanomedicines could help to improve the performance of therapeutics, vaccines and diagnosis of Chagas disease.

Development of a Fluorescence-based Trypanosoma cruzi CYP51 Inhibition Assay for Effective Compound Triaging in Drug Discovery Programmes for Chagas Disease

Chagas disease, caused by the protozoan parasite Trypanosoma cruzi (T. cruzi), is a life threatening global health problem with only two drugs available for treatment (benznidazole and nifurtimox), both having variable efficacy in the chronic stage of the disease and high rates of adverse drug reactions. Inhibitors of sterol 14α-demethylase (CYP51) have proven effective against T. cruzi in vitro and in vivo in animal models of Chagas disease. Consequently two azole inhibitors of CYP51 (posaconazole and ravuconazole) have recently entered clinical development by the Drugs for Neglected Diseases initiative. Further new drug treatments for this disease are however still urgently required, particularly having a different mode of action to CYP51 in order to balance the overall risk in the drug discovery portfolio. This need has now been further strengthened by the very recent reports of treatment failure in the clinic for both posaconazole and ravuconazole. To this end and to prevent enrichment of drug candidates against a single target, there is a clear need for a robust high throughput assay for CYP51 inhibition in order to evaluate compounds active against T. cruzi arising from phenotypic screens. A high throughput fluorescence based functional assay using recombinantly expressed T. cruzi CYP51 (Tulahuen strain) is presented here that meets this requirement. This assay has proved valuable in prioritising medicinal chemistry resource on only those T. cruzi active series arising from a phenotypic screening campaign where it is clear that the predominant mode of action is likely not via inhibition of CYP51.

Chagas disease, caused by the parasite Trypanosoma cruzi (T. cruzi), is endemic in Latin America and emerging in North America and Europe through human migration. It is a severe global health problem with 8–10 million people infected and an estimated 12,000 deaths annually. Current treatment options are poorly efficacious and have severe side effects. New drugs are therefore urgently required. Two of these potential new drugs, posaconazole and ravuconazole, both targeting an enzyme in T. cruzi called CYP51, have recently failed in clinical development. Therefore, in light of these recent clinical failures and in order to better balance the overall risk in the drug discovery portfolio for Chagas disease, it has become prudent to assess whether new chemical start points for drug discovery programmes have a mode of action predominantly driven by T. cruzi CYP51 inhibition. In this paper we report a fluorescence based assay to determine whether compounds inhibit T. cruzi CYP51. This provides a high throughput screen to help prioritise medicinal chemistry resource on those T. cruzi active new chemical series that do not have a mode of action predominantly driven by CYP51 inhibition.

Translational challenges of animal models in Chagas disease drug development: a review

Chagas disease, or American trypanosomiasis, caused by Trypanosoma cruzi parasite infection is endemic in Latin America and presents an increasing clinical challenge due to migrating populations. Despite being first identified over a century ago, only two drugs are available for its treatment, and recent outcomes from the first clinical trials in 40 years were lackluster. There is a critical need to develop new drugs to treat Chagas disease. This requires a better understanding of the progression of parasite infection, and standardization of animal models designed for Chagas disease drug discovery. Such measures would improve comparison of generated data and the predictability of test hypotheses and models designed for translation to human disease. Existing animal models address both disease pathology and treatment efficacy. Available models have limited predictive value for the preclinical evaluation of novel therapies and need to more confidently predict the efficacy of new drug candidates in clinical trials. This review highlights the overall lack of standardized methodology and assessment tools, which has hampered the development of efficacious compounds to treat Chagas disease. We provide an overview of animal models for Chagas disease, and propose steps that could be undertaken to reduce variability and improve predictability of drug candidate efficacy. New technological developments and tools may contribute to a much needed boost in the drug discovery process.

Antitrypanosomal Treatment with Benznidazole Is Superior to Posaconazole Regimens in Mouse Models of Chagas Disease

Two CYP51 inhibitors, posaconazole and the ravuconazole prodrug E1224, were recently tested in clinical trials for efficacy in indeterminate Chagas disease. The results from these studies show that both drugs cleared parasites from the blood of infected patients at the end of the treatment but that parasitemia rebounded over the following months. In the current study, we sought to identify a dosing regimen of posaconazole that could permanently clear Trypanosoma cruzi from mice with experimental Chagas disease. Infected mice were treated with posaconazole or benznidazole, an established Chagas disease drug, and parasitological cure was defined as an absence of parasitemia recrudescence after immunosuppression. Twenty-day therapy with benznidazole (10 to 100 mg/kg of body weight/day) resulted in a dose-dependent increase in antiparasitic activity, and the 100-mg/kg regimen effected parasitological cure in all treated mice. In contrast, all mice remained infected after a 25-day treatment with posaconazole at all tested doses (10 to 100 mg/kg/day). Further extension of posaconazole therapy to 40 days resulted in only a marginal improvement of treatment outcome. We also observed similar differences in antiparasitic activity between benznidazole and posaconazole in acute T. cruzi heart infections. While benznidazole induced rapid, dose-dependent reductions in heart parasite burdens, the antiparasitic activity of posaconazole plateaued at low doses (3 to 10 mg/kg/day) despite increasing drug exposure in plasma. These observations are in good agreement with the outcomes of recent phase 2 trials with posaconazole and suggest that the efficacy models combined with the pharmacokinetic analysis employed here will be useful in predicting clinical outcomes of new drug candidates.

Aryloxyethyl Thiocyanates Are Potent Growth Inhibitors of Trypanosoma cruzi and Toxoplasma gondii

As a part of our project aimed at searching for new safe chemotherapeutic agents against parasitic diseases, several compounds structurally related to the antiparasitic agent WC-9 (4-phenoxyphenoxyethyl thiocyanate), which were modified at the terminal phenyl ring, were designed, synthesized, and evaluated as growth inhibitors against Trypanosoma cruzi, the etiological agent of Chagas disease, and Toxoplasma gondii, the parasite responsible of toxoplasmosis. Most of the synthetic analogues exhibited similar antiparasitic activity and were slightly more potent than our lead WC-9. For example, two trifluoromethylated derivatives exhibited ED50 values of 10.0 and 9.2 μM against intracellular T. cruzi, whereas they showed potent action against tachyzoites of T. gondii (ED50 values of 1.6 and 1.9 μM against T. gondii). In addition, analogues of WC-9 in which the terminal aryl group is in the meta position with respect to the alkyl chain bearing the thiocyanate group showed potent inhibitory action against both T. cruzi and T. gondii at the very low micromolar range, which suggests that a para-phenyl substitution pattern is not necessary for biological activity.

The Dialogue of the Host-Parasite Relationship: Leishmania spp. and Trypanosoma cruzi Infection

The intracellular protozoa Leishmania spp. and Trypanosoma cruzi and the causative agents of Leishmaniasis and Chagas disease, respectively, belong to the Trypanosomatidae family. Together, these two neglected tropical diseases affect approximately 25 million people worldwide. Whether the host can control the infection or develops disease depends on the complex interaction between parasite and host. Parasite surface and secreted molecules are involved in triggering specific signaling pathways essential for parasite entry and intracellular survival. The recognition of the parasite antigens by host immune cells generates a specific immune response. Leishmania spp. and T. cruzi have a multifaceted repertoire of strategies to evade or subvert the immune system by interfering with a range of signal transduction pathways in host cells, which causes the inhibition of the protective response and contributes to their persistence in the host. The current therapeutic strategies in leishmaniasis and trypanosomiasis are very limited. Efficacy is variable, toxicity is high, and the emergence of resistance is increasingly common. In this review, we discuss the molecular basis of the host-parasite interaction of Leishmania and Trypanosoma cruzi infection and their mechanisms of subverting the immune response and how this knowledge can be used as a tool for the development of new drugs.

Designing and exploring active N'-[(5-nitrofuran-2-yl) methylene] substituted hydrazides against three Trypanosoma cruzi strains more prevalent in Chagas disease patients

Chagas disease affects around 8 million people worldwide and its treatment depends on only two nitroheterocyclic drugs, benznidazole (BZD) and nifurtimox (NFX). Both drugs have limited curative power in chronic phase of disease. Nifuroxazide (NF), a nitroheterocyclic drug, was used as lead to design a set of twenty one compounds in order to improve the anti-Trypanosoma cruzi activity. Lipinski's rules were considered in order to support drug-likeness designing. The set of N'-[(5-nitrofuran-2-yl) methylene] substituted hydrazides was assayed against three T. cruzi strains, which represent the discrete typing units more prevalent in human patients: Y (TcII), Silvio X10 cl1 (TcI), and Bug 2149 cl10 (TcV). All the derivatives, except one, showed enhanced trypanocidal activity against the three strains as compared to BZD. In the Y strain 62% of the compounds were more active than NFX. The most active compound was N'-((5-nitrofuran-2-yl) methylene)biphenyl-4-carbohydrazide (C20), which showed IC50 values of 1.17 ± 0.12 μM; 3.17 ± 0.32 μM; and 1.81 ± 0.18 μM for Y, Silvio X10 cl1, and Bug 2149 cl10 strains, respectively. Cytotoxicity assays with human fibroblast cells have demonstrated high selectivity indices for several compounds. Exploratory data analysis indicated that primarily topological, steric/geometric, and electronic properties have contributed to the discrimination of the set of investigated compounds. The findings can be helpful to drive the designing, and subsequently, the synthesis of additional promising drugs against Chagas disease.

SQ109, a new drug lead for Chagas disease

We tested the antituberculosis drug SQ109, which is currently in advanced clinical trials for the treatment of drug-susceptible and drug-resistant tuberculosis, for its in vitro activity against the trypanosomatid parasite Trypanosoma cruzi, the causative agent of Chagas disease. SQ109 was found to be a potent inhibitor of the trypomastigote form of the parasite, with a 50% inhibitory concentration (IC50) for cell killing of 50 ± 8 nM, but it had little effect (50% effective concentration [EC50], ∼80 μM) in a red blood cell hemolysis assay. It also inhibited extracellular epimastigotes (IC50, 4.6 ± 1 μM) and the clinically relevant intracellular amastigotes (IC50, ∼0.5 to 1 μM), with a selectivity index of ∼10 to 20. SQ109 caused major ultrastructural changes in all three life cycle forms, as observed by light microscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). It rapidly collapsed the inner mitochondrial membrane potential (Δψm) in succinate-energized mitochondria, acting in the same manner as the uncoupler FCCP [carbonyl cyanide 4-(trifluoromethoxy)phenylhydrazone], and it caused the alkalinization of internal acidic compartments, effects that are likely to make major contributions to its mechanism of action. The compound also had activity against squalene synthase, binding to its active site; it inhibited sterol side-chain reduction and, in the amastigote assay, acted synergistically with the antifungal drug posaconazole, with a fractional inhibitory concentration index (FICI) of 0.48, but these effects are unlikely to account for the rapid effects seen on cell morphology and cell killing. SQ109 thus most likely acts, at least in part, by collapsing Δψ/ΔpH, one of the major mechanisms demonstrated previously for its action against Mycobacterium tuberculosis. Overall, the results suggest that SQ109, which is currently in advanced clinical trials for the treatment of drug-susceptible and drug-resistant tuberculosis, may also have potential as a drug lead against Chagas disease.

Binding mode and potency of N-indolyloxopyridinyl-4-aminopropanyl-based inhibitors targeting Trypanosoma cruzi CYP51

Chagas disease is a chronic infection in humans caused by Trypanosoma cruzi and manifested in progressive cardiomyopathy and/or gastrointestinal dysfunction. Limited therapeutic options to prevent and treat Chagas disease put 8 million people infected with T. cruzi worldwide at risk. CYP51, involved in the biosynthesis of the membrane sterol component in eukaryotes, is a promising drug target in T. cruzi. We report the structure–activity relationships (SAR) of an N-arylpiperazine series of N-indolyloxopyridinyl-4-aminopropanyl-based inhibitors designed to probe the impact of substituents in the terminal N-phenyl ring on binding mode, selectivity and potency. Depending on the substituents at C-4, two distinct ring binding modes, buried and solvent-exposed, have been observed by X-ray structure analysis (resolution of 1.95–2.48 Å). The 5-chloro-substituted analogs 9 and 10 with no substituent at C-4 demonstrated improved selectivity and potency, suppressing ≥99.8% parasitemia in mice when administered orally at 25 mg/kg, b.i.d., for 4 days.

Recent clinical trials for the etiological treatment of chronic chagas disease: advances, challenges and perspectives

Chagas disease, a chronic systemic parasitosis caused by the Kinetoplastid protozoon Trypanosoma cruzi, is the first cause of cardiac morbidity and mortality in poor rural and suburban areas of Latin America and the largest parasitic disease burden in the continent, now spreading worldwide due to international migrations. A recent change in the scientific paradigm on the pathogenesis of chronic Chagas disease has led to a consensus that all T. cruzi-seropositive patients should receive etiological treatment. This important scientific advance has spurred the rigorous evaluation of the safety and efficacy of currently available drugs (benznidazole and nifurtimox) as well as novel anti-T. cruzi drug candidates in chronic patients, who were previously excluded from such treatment. The first results indicate that benznidazole is effective in inducing a marked and sustained reduction in the circulating parasites' level in the majority of these patients, but adverse effects can lead to treatment discontinuation in 10-20% of cases. Ergosterol biosynthesis inhibitors, such as posaconazole and ravuconazole, are better tolerated but their efficacy at the doses and treatment duration used in the initial studies was significantly lower; such results are probably related to suboptimal exposure and/or treatment duration. Combination therapies are a promising perspective but the lack of validated biomarkers of response to etiological treatment and eventual parasitological cures in chronic patients remains a serious challenge.

4-Aminopyridyl-based CYP51 inhibitors as anti-Trypanosoma cruzi drug leads with improved pharmacokinetic profile and in vivo potency

CYP51 is a P450 enzyme involved in the biosynthesis of the sterol components of eukaryotic cell membranes. CYP51 inhibitors have been developed to treat infections caused by fungi, and more recently the protozoan parasite Trypanosoma cruzi, the causative agent of Chagas disease. To specifically optimize drug candidates for T. cruzi CYP51 (TcCYP51), we explored the structure-activity relationship (SAR) of a N-indolyl-oxopyridinyl-4-aminopropanyl-based scaffold originally identified in a target-based screen. This scaffold evolved via medicinal chemistry to yield orally bioavailable leads with potent anti-T. cruzi activity in vivo. Using an animal model of infection with a transgenic T. cruzi Y luc strain expressing firefly luciferase, we prioritized the biaryl and N-arylpiperazine analogues by oral bioavailability and potency. The drug-target complexes for both scaffold variants were characterized by X-ray structure analysis. Optimization of both binding mode and pharmacokinetic properties of these compounds led to potent inhibitors against experimental T. cruzi infection.

Discovery of new uncompetitive inhibitors of glucose-6-phosphate dehydrogenase

The enzyme glucose-6-phosphate dehydrogenase (G6PDH) catalyzes the first step of the oxidative branch of the pentose phosphate pathway, which provides cells with NADPH, an essential cofactor for many biosynthetic pathways and antioxidizing enzymes. In Trypanosoma cruzi, the G6PDH has being pursued as a relevant target for the development of new drugs against Chagas disease. At present, the best characterized inhibitors of T. cruzi G6PDH are steroidal halogenated compounds derivatives from the mammalian hormone precursor dehydroepiandrosterone, which indeed are also good inhibitors of the human homologue enzyme. The lack of target selectivity might result in hemolytic side effects due to partial inhibition of human G6PDH in red blood cells. Moreover, the treatment of Chagas patients with steroidal drugs might also cause undesired androgenic side effects. Aiming to identify of new chemical classes of T. cruzi G6PDH inhibitors, we performed a target-based high-throughput screen campaign against a commercial library of diverse compounds. Novel TcG6PDH inhibitors were identified among thienopyrimidine and quinazolinone derivatives. Preliminary structure activity relationships for the identified hits are presented, including structural features that contribute for selectivity toward the parasite enzyme. Our results indicate that quinazolinones are promising hits that should be considered for further optimization.

Madurella mycetomatis is highly susceptible to ravuconazole

The current treatment of eumycetoma utilizing ketoconazole is unsatisfactory because of high recurrence rates, which often leads to complications and unnecessary amputations, and its comparatively high cost in endemic areas. Hence, an effective and affordable drug is required to improve therapeutic outcome. E1224 is a potent orally available, broad-spectrum triazole currently being developed for the treatment of Chagas disease. E1224 is a prodrug that is rapidly converted to ravuconazole. Plasma levels of E1224 are low and transient, and its therapeutically active moiety, ravuconazole is therapeutically active. In the present study, the in vitro activity of ravuconazole against Madurella mycetomatis, the most common etiologic agent of eumycetoma, was evaluated and compared to that of ketoconazole and itraconazole. Ravuconazole showed excellent activity with MICs ranging between ≤0.002 and 0.031 µg/ml, which were significantly lower than the MICs reported for ketoconazole and itraconazole. On the basis of our findings, E1224 with its resultant active moiety, ravuconazole, could be an effective and affordable therapeutic option for the treatment of eumycetoma.

Madurella mycetomatis is the most common etiologic agent of eumycetoma worldwide. Treatment of this infection is very difficult and associated with high recurrence rates and low cure rates. Currently the treatment consists of a combination of surgery and antifungal therapy. Antifungal therapy is usually given for at least one year. However, the commonly used antifungal ketoconazole is too expensive for many patients in endemic countries and has many side effects. In the present study we evaluated the in vitro activity of the new antifungal agent ravuconazole against M. mycetomatis. The drug showed excellent in vitro activity against all tested strains and its prodrug, E1224, might be a potential new therapeutic option for eumycetoma caused by M. mycetomatis.

Expanding the binding envelope of CYP51 inhibitors targeting Trypanosoma cruzi with 4-aminopyridyl-based sulfonamide derivatives

Chagas disease is a chronic infection caused by the protozoan parasite Trypanosoma cruzi, manifested in progressive cardiomyopathy and/or gastrointestinal dysfunction. Therapeutic options to prevent or treat Chagas disease are limited. CYP51, the enzyme key to the biosynthesis of eukaryotic membrane sterols, is a validated drug target in both fungi and T. cruzi. Sulfonamide derivatives of 4-aminopyridyl-based inhibitors of T. cruzi CYP51 (TcCYP51), including the sub-nanomolar compound 3, have molecular structures distinct from other validated CYP51 inhibitors. They augment the biologically relevant chemical space of molecules targeting TcCYP51. In a 2.08 Å X-ray structure, TcCYP51 is in a conformation that has been influenced by compound 3 and is distinct from the previously characterized ground-state conformation of CYP51 drug-target complexes. That the binding site was modulated in response to an incoming inhibitor for the first time characterizes TcCYP51 as a flexible target rather than a rigid template.

Genetic profiling of the isoprenoid and sterol biosynthesis pathway genes of Trypanosoma cruzi

In Trypanosoma cruzi the isoprenoid and sterol biosynthesis pathways are validated targets for chemotherapeutic intervention. In this work we present a study of the genetic diversity observed in genes from these pathways. Using a number of bioinformatic strategies, we first identified genes that were missing and/or were truncated in the T. cruzi genome. Based on this analysis we obtained the complete sequence of the ortholog of the yeast ERG26 gene and identified a non-orthologous homolog of the yeast ERG25 gene (sterol methyl oxidase, SMO), and we propose that the orthologs of ERG25 have been lost in trypanosomes (but not in Leishmanias). Next, starting from a set of 16 T. cruzi strains representative of all extant evolutionary lineages, we amplified and sequenced ∼24 Kbp from 22 genes, identifying a total of 975 SNPs or fixed differences, of which 28% represent non-synonymous changes. We observed genes with a density of substitutions ranging from those close to the average (∼2.5/100 bp) to some showing a high number of changes (11.4/100 bp, for the putative lathosterol oxidase gene). All the genes of the pathway are under apparent purifying selection, but genes coding for the sterol C14-demethylase, the HMG-CoA synthase, and the HMG-CoA reductase have the lowest density of missense SNPs in the panel. Other genes (TcPMK, TcSMO-like) have a relatively high density of non-synonymous SNPs (2.5 and 1.9 every 100 bp, respectively). However, none of the non-synonymous changes identified affect a catalytic or ligand binding site residue. A comparative analysis of the corresponding genes from African trypanosomes and Leishmania shows similar levels of apparent selection for each gene. This information will be essential for future drug development studies focused on this pathway.

Squalene synthase as a target for Chagas disease therapeutics

Trypanosomatid parasites are the causative agents of many neglected tropical diseases and there is currently considerable interest in targeting endogenous sterol biosynthesis in these organisms as a route to the development of novel anti-infective drugs. Here, we report the first x-ray crystallographic structures of the enzyme squalene synthase (SQS) from a trypanosomatid parasite, Trypanosoma cruzi, the causative agent of Chagas disease. We obtained five structures of T. cruzi SQS and eight structures of human SQS with four classes of inhibitors: the substrate-analog S-thiolo-farnesyl diphosphate, the quinuclidines E5700 and ER119884, several lipophilic bisphosphonates, and the thiocyanate WC-9, with the structures of the two very potent quinuclidines suggesting strategies for selective inhibitor development. We also show that the lipophilic bisphosphonates have low nM activity against T. cruzi and inhibit endogenous sterol biosynthesis and that E5700 acts synergistically with the azole drug, posaconazole. The determination of the structures of trypanosomatid and human SQS enzymes with a diverse set of inhibitors active in cells provides insights into SQS inhibition, of interest in the context of the development of drugs against Chagas disease.

Chagas disease is caused by the protozoan parasite Trypanosoma cruzi and affects eight million individuals, primarily in Latin America. Currently there is no cure for chronic T. cruzi infections. Unlike humans, this parasite use a variety of sterols (e.g. ergosterol, 24-ethyl-cholesta-5,7,22-trien-3 beta ol, and its 22-dihydro analogs), rather than cholesterol in their cell membranes, so inhibiting endogenous sterol biosynthesis is an important therapeutic target. Here, we report the first structure of the parasite's squalene synthase, which catalyzes the first committed step in sterol biosynthesis, as well as the structures of a broad range of squalene synthase inhibitors active against the clinically relevant intracellular stages, opening the way to new approaches to treating this neglected tropical disease.

Nitroheterocyclic compounds are more efficacious than CYP51 inhibitors against Trypanosoma cruzi: implications for Chagas disease drug discovery and development

Advocacy for better drugs and access to treatment has boosted the interest in drug discovery and development for Chagas disease, a chronic infection caused by the genetically heterogeneous parasite, Trypanosoma cruzi. In this work new in vitro assays were used to gain a better understanding of the antitrypanosomal properties of the most advanced antichagasic lead and clinical compounds, the nitroheterocyclics benznidazole, nifurtimox and fexinidazole sulfone, the oxaborole AN4169, and four ergosterol biosynthesis inhibitors--posaconazole, ravuconazole, EPL-BS967 and EPL-BS1246. Two types of assays were developed: one for evaluation of potency and efficacy in dose-response against a panel of T. cruzi stocks representing all current discrete typing units (DTUs), and a time-kill assay. Although less potent, the nitroheterocyclics and the oxaborole showed broad efficacy against all T. cruzi tested and were rapidly trypanocidal, whilst ergosterol biosynthesis inhibitors showed variable activity that was both compound- and strain-specific, and were unable to eradicate intracellular infection even after 7 days of continuous compound exposure at most efficacious concentrations. These findings contest previous reports of variable responses to nitroderivatives among different T. cruzi strains and further challenge the introduction of ergosterol biosynthesis inhibitors as new single chemotherapeutic agents for the treatment of Chagas disease.

R-Configuration of 4-Aminopyridyl-Based Inhibitors of CYP51 Confers Superior Efficacy Against Trypanosoma cruzi

Sterol 14α-demethylase (CYP51) is an important therapeutic target for fungal and parasitic infections due to its key role in the biosynthesis of ergosterol, an essential component of the cell membranes of these pathogenic organisms. We report the development of potent and selective d-tryptophan-derived inhibitors of T. cruzi CYP51. Structural information obtained from the cocrystal structure of CYP51 and (R)-2, which is >1000-fold more potent than its enantiomer (S)-1, was used to guide design of additional analogues. The in vitro efficacy data presented here for (R)-2-(R)-8, together with preliminary in vitro pharmacokinetic data suggest that this new CYP51 inhibitor scaffold series has potential to deliver drug candidates for treatment of T. cruzi infections.

Clotrimazole as a Cancer Drug: A Short Review

Although clotrimazole was first used against fungal infections, a body of research was later developed indicating that this drug has anticancer properties as well. The mechanism of action is based on the inhibition of mitochondrial-bound glycolytic enzymes and calmodulin, which starves cancer cells of energy. Clotrimazole and its derivatives have been shown to decrease rates of cancer cell proliferation, induce G1 phase arrest, and promote pro-apoptotic factors, which lead to cell death.

Soulamarin isolated from Calophyllum brasiliense (Clusiaceae) induces plasma membrane permeabilization of Trypanosoma cruzi and mytochondrial dysfunction

Chagas disease is caused by the parasitic protozoan Trypanosoma cruzi. It has high mortality as well as morbidity rates and usually affects the poorer sections of the population. The development of new, less harmful and more effective drugs is a promising research target, since current standard treatments are highly toxic and administered for long periods. Fractioning of methanol (MeOH) extract of the stem bark of Calophyllum brasiliense (Clusiaceae) resulted in the isolation of the coumarin soulamarin, which was characterized by one- and two-dimensional ¹H- and ¹³C NMR spectroscopy as well as ESI mass spectrometry. All data obtained were consistent with a structure of 6-hydroxy-4-propyl-5-(3-hydroxy-2-methyl-1-oxobutyl)-6″,6″-dimethylpyrane-[2″,3″:8,7]-benzopyran-2-one for soulamarin. Colorimetric MTT assays showed that soulamarin induces trypanocidal effects, and is also active against trypomastigotes. Hemolytic activity tests showed that soulamarin is unable to induce any observable damage to erythrocytes (c_max. = 1,300 µM). The lethal action of soulamarin against T. cruzi was investigated by using amino(4-(6-(amino(iminio)methyl)-1H-indol-2-yl)phenyl)methaniminium chloride (SYTOX Green and 1H,5H,11H,15H-Xantheno[2,3,4-ij:5,6,7-i′j′]diquinolizin-18-ium, 9-[4-(chloromethyl)phenyl]-2,3,6,7,12,13,16,17-octahydro-chloride (MitoTracker Red) as fluorimetric probes. With the former, soulamarin showed dose-dependent permeability of the plasma membrane, relative to fully permeable Triton X-100-treated parasites. Spectrofluorimetric and fluorescence microscopy with the latter revealed that soulamarin also induced a strong depolarization (ca. 97%) of the mitochondrial membrane potential. These data demonstrate that the lethal action of soulamarin towards T. cruzi involves damages to the plasma membrane of the parasite and mitochondrial dysfunction without the additional generation of reactive oxygen species, which may have also contributed to the death of the parasites. Considering the unique mitochondrion of T. cruzi, secondary metabolites of plants affecting the bioenergetic system as soulamarin may contribute as scaffolds for the design of novel and selective drug candidates for neglected diseases, mainly Chagas disease.

Chagas disease is a parasitic protozoan that affects the poorest population in the world, causing a high mortality and morbidity. As a result of highly toxic and long-term treatments, the discovery of novel, safe and more efficacious drugs is essential. Natural products isolated from plants are commonly used as drug prototypes or precursors to treat parasitic diseases. As part of our investigation of bioactive compounds from Brazilian flora, the present study was undertaken in order to determine the antitrypanosomal effects of the soulamarin, a coumarin isolated from the stem bark of Callophyllum brasiliense (Clusiaceae), against Trypanossoma cruzi. This study moreover investigated the lethal action of soulamarin towards the parasite. Considering the obtained results, secondary metabolites of plants affecting the bioenergetic system as soulamarin may contribute as scaffolds for the design of novel and selective drug candidates for neglected diseases, mainly Chagas disease.

Rational development of 4-aminopyridyl-based inhibitors targeting Trypanosoma cruzi CYP51 as anti-chagas agents

A new series of 4-aminopyridyl-based lead inhibitors targeting Trypanosoma cruzi CYP51 (TcCYP51) has been developed using structure-based drug design as well as structure-property relationship (SPR) analyses. The screening hit starting point, LP10 (KD ≤ 42 nM; EC50 = 0.65 μM), has been optimized to give the potential leads 14t, 27i, 27q, 27r, and 27t, which have low-nanomolar binding affinity to TcCYP51 and significant activity against T. cruzi amastigotes cultured in human myoblasts (EC50 = 14-18 nM for 27i and 27r). Many of the optimized compounds have improved microsome stability, and most are selective against human CYPs 1A2, 2D6, and 3A4 (<50% inhibition at 1 μM). A rationale for the improvement in microsome stability and selectivity of inhibitors against human metabolic CYP enzymes is presented. In addition, the binding mode of 14t with the Trypanosoma brucei CYP51 (TbCYP51) orthologue has been characterized by X-ray structure analysis.

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.

Organocatalytic, enantioselective synthesis of VNI: a robust therapeutic development platform for Chagas, a neglected tropical disease

VNI is a potent inhibitor of CYP51 and was recently shown to achieve a parasitological cure of mice infected with T. cruzi in both acute and chronic stages of infection. T. cruzi is the causative parasite of Chagas disease, a neglected tropical disease. The first enantioselective chemical synthesis of VNI (at a materials cost of less than $0.10/mg) is described. Furthermore, the key enantioselective step is performed at the 10 g scale.

Efficacy of voriconazole in a murine model of acute Trypanosoma cruzi infection

OBJECTIVES

Antifungal triazole derivatives have been studied as possible alternatives for the treatment of Chagas' disease. Voriconazole has demonstrated in vitro activity against Trypanosoma cruzi, but its efficacy in vivo has not yet been tested. We aimed to determine the effect of voriconazole in a murine model of acute T. cruzi infection.

METHODS

Treatment efficacy was evaluated by comparing parasitaemia, mortality and organ involvement (by histological examination) of infected mice.

RESULTS

Treatment with voriconazole significantly lowered parasitaemia and mortality compared with controls, reduced the percentage of mice with amastigote nests in heart and skeletal muscle and moderately decreased myocardial inflammation.

CONCLUSIONS

Our findings support the potential of voriconazole for the treatment of acute Chagas' disease and motivate future animal studies using varying doses and treatment schemes. Further evaluation of voriconazole for clinical use in human Chagas' patients is warranted.