Successful treatment of Old World cutaneous leishmaniasis caused by Leishmania infantum with posaconazole

Complicated Cutaneous Leishmaniasis in a Patient under Combined Immunosuppression

Species associated with visceral leishmaniasis, such as L. infantum, may be responsible for cutaneous leishmaniasis (CL), particularly in the Mediterranean region. In immunosuppressed hosts, classification as complicated CL is essential, as the risk of mucosal leishmaniasis warrants systemic therapy. We report the case of a forty-seven-year-old male living in Portugal, with Fabry disease and receiving immunosuppressive treatment with adalimumab and methotrexate for Crohn's disease. There was no travel history outside of Europe. He presented a two-year-old, 5.5 cm plaque with a well-defined hyperkeratotic elevated border and central, painless ulceration on his back. The biopsy revealed parasites inside macrophages suggestive of Leishmania, and PCR identified the species as L. infantum. A biopsy via nasal endoscopy excluded mucosal involvement. Classification as complicated CL dictated treatment with liposomal amphotericin B and subsequent topical paramomycin. The rarity of CL in Portugal may delay its diagnosis, especially in autochthonous infections. Treatment choice is complicated by the heterogeneity of drugs available worldwide. As the global prevalence of CL increases, it is important to be aware of this diagnosis.

Unusual Observations in Leishmaniasis-An Overview

Leishmaniasis significantly affects the population of the tropics and subtropics. Clinical features and infective species of Leishmania are the primary factors driving the direction of diagnosis. The rise in incidences of atypical presentations present a challenge in patient treatment. Knowledge of unusual/rare presentations can aid in having a broader perspective for including the different aspects during the examination and thus avoid misdiagnosis. A comprehensive literature survey was performed to present the array of atypical presentations confounding clinicians which have been seen in leishmaniasis. Case reports of unusual findings based on the localizations and morphology of lesions and infective species and the predominant geographical sites over almost five decades highlight such presentations in the population. Information regarding the clinical features recorded in the patient and the chosen treatment was extracted to put forward the preferred drug regimen in such cases. This comprehensive review presents various unusual observations seen in visceral leishmaniasis, post-kala-azar dermal leishmaniasis, cutaneous leishmaniasis, and mucocutaneous leishmaniasis. It highlights the need to consider such features in association with differential diagnosis to facilitate proper treatment of the patient.

Evaluating posaconazole, its pharmacology, efficacy and safety for the prophylaxis and treatment of fungal infections

INTRODUCTION

Invasive fungal diseases (IFDs) are a significant cause of morbidity and mortality among immunocompromised patients. Safe and effective antifungal medications used for prophylaxis and treatment are pivotal in their management. Posaconazole is a promising triazole antifungal agent.

AREAS COVERED

The authors discuss the pharmacological properties of posaconazole, including pharmacokinetics/pharmacodynamics, safety and tolerability profile, together with efficacy data for prophylaxis and treatment as well as its use in special populations based on current literature.

EXPERT OPINION

Posaconazole has a favorable safety and tolerability profile; however, caution is advised when co-administered with agents that are CYP3A4 inhibitors, because their concentration may significantly increase, and their levels should be closely monitored. It has an extended spectrum of activity against yeasts and filamentous fungi. It is successfully used as prophylaxis for patients with acute myeloid leukemia (AML)/myelodysplastic syndrome (MDS) and post-hematopoietic cell transplantation (HCT) with graft-versus-host disease (GVHD). It is the first line treatment for oropharyngeal candidiasis and is also used as a salvage treatment for refractory IFDs. Currently available formulations include the oral suspension, delayed-release tablets and solution for intravenous infusion, all with different PK/PD properties and indications. Its use in children and adolescents is currently being examined in Phase-II clinical trials.

Potency and preclinical evidence of synergy of oral azole drugs and miltefosine in an ex vivo model of Leishmania (Viannia) panamensis infection

Failure of treatment of cutaneous leishmaniasis with antimonial drugs and miltefosine is frequent. Use of oral combination therapy represents an attractive strategy to increase efficacy of treatment and reduce the risk of drug resistance. We evaluated the potency of posaconazole, itraconazole, voriconazole and fluconazole, and the potential synergy of those demonstrating the highest potency, in combination with miltefosine (HePC), against infection with Leishmania (Viannia) panamensis. Synergistic activity was determined by isobolograms and calculation of Fractional Inhibitory Concentration Index (FICI), based on parasite quantification using an ex vivo model of human PBMCs infected with a luciferase-transfected, antimony and miltefosine sensitive line of L. panamensis. The drug combination and concentrations that displayed synergy were then evaluated for anti-leishmanial effect in 10 clinical strains of L. panamensis by qRT-PCR of Leishmania 7SLRNA. High potency was substantiated for posaconazole and itraconazole against sensitive as well as HePC and antimony resistant lines of L. panamensis, whereas fluconazole and voriconazole displayed low potency. HePC combined with posaconazole (Poz) demonstrated evidence of synergy at free drug concentrations achieved in plasma during treatment (2 μM HePC + 4 μM Poz). FICI, based on 70% and 90% reduction of infection, was 0.5 for the sensitive line. Combination of 2 μM HePC + 4 μM Poz effected significantly greater reduction of infection by clinical strains of L. panamensis than individual drugs. Orally administrable miltefosine/posaconazole combinations demonstrated synergistic anti-leishmanial capacity ex vivo against L. panamensis, supporting their potential as a novel therapeutic strategy to improve efficacy, and effectiveness of treatment.

Effect of Adjunctive Topical Liposomal Azithromycin on Systemic Azithromycin on Old World Cutaneous Leishmaniasis: A Pilot Clinical Study

The treatment of Cutaneous Leishmaniasis (CL) is complex, and the search for safer, more efficient, and cost-effective treatments is ongoing. This study aimed to evaluate the efficacy of the combination of liposomal and oral azithromycin as the first clinical study against CL. This assessor-blind, randomized clinical trial was conducted in out-patients Leishmaniasis clinic of Skin Diseases and Leishmaniasis. The cutaneous lesions of eligible participants were randomized to receive either oral azithromycin or the combined oral and topical liposomal azithromycin. All participants received 250 mg of azithromycin twice daily or 8 mg/per kg for 4 weeks. In the combination group, a topical liposomal formulation of 0.04 mmol/mL of azithromycin was administered as 0.2-0.5 cc twice daily according to the lesion size in order to make a thin layer of the drug on the surface of the lesion. The size and induration changes from baseline to the end of the study were analyzed. Twenty-one lesions of 13 patients in the combination group and 20 lesions of 14 patients in the oral group were recruited. The mean ± SD of improvement was significantly different between two groups after 12 weeks (3.89 ± 0.46 vs. 3.15 ± 1.23 P = 0.02 combination group vs. oral group respectively). The patients did not experience any systemic adverse effects related to azithromycin and the only adverse effects related to topical treatment were mild pruritus in 2 cases. In conclusion, the combination of oral and topical liposomal formulation of azithromycin is safe and effective to treat CL.

Synthesis and Antileishmanial Evaluation of Arylimidamide-Azole Hybrids Containing a Phenoxyalkyl Linker

Due to the limitations of existing medications, there is a critical need for new drugs to treat visceral leishmaniasis. Since arylimidamides and antifungal azoles both show oral activity in murine visceral leishmaniasis models, a molecular hybridization approach was employed where arylimidamide and azole groups were separated by phenoxyalkyl linkers in an attempt to capitalize on the favorable antileishmanial properties of both series. Among the target compounds synthesized, a greater antileishmanial potency against intracellular Leishmania donovani was observed as the linker length increased from two to eight carbons and when an imidazole ring was employed as the terminal group compared to a 1,2,4-triazole group. Compound 24c (N-(4-((8-(1H-imidazol-1-yl)octyl)oxy)-2-isopropoxyphenyl) picolinimidamide) displayed activity against L. donovani intracellular amastigotes with an IC₅₀ value of 0.53 μM. When tested in a murine visceral leishmaniasis model, compound 24c at a dose of 75 mg/kg/day p.o. for five consecutive days resulted in a modest 33% decrease in liver parasitemia compared to the control group, indicating that further optimization of these molecules is needed. While potent hybrid compounds bearing an imidazole terminal group were also strong inhibitors of recombinant CYP51 from L. donovani, as assessed by a fluorescence-based assay, additional targets are likely to play an important role in the antileishmanial action of these compounds.

The emerging paradigm of calcium homeostasis as a new therapeutic target for protozoan parasites

Calcium channels (CCs), a group of ubiquitously expressed membrane proteins, are involved in many pathophysiological processes of protozoan parasites. Our understanding of CCs in cell signaling, organelle function, cellular homeostasis, and cell cycle control has led to improved insights into their structure and functions. In this article, we discuss CCs characteristics of five major protozoan parasites Plasmodium, Leishmania, Toxoplasma, Trypanosoma, and Cryptosporidium. We provide a comprehensive review of current antiparasitic drugs and the potential of using CCs as new therapeutic targets. Interestingly, previous studies have demonstrated that human CC modulators can kill or sensitize parasites to antiparasitic drugs. Still, none of the parasite CCs, pumps, or transporters has been validated as drug targets. Information for this review draws from extensive data mining of genome sequences, chemical library screenings, and drug design studies. Parasitic resistance to currently approved therapeutics is a serious and emerging threat to both disease control and management efforts. In this article, we suggest that the disruption of calcium homeostasis may be an effective approach to develop new anti-parasite drug candidates and reduce parasite resistance.

Disruption of Intracellular Calcium Homeostasis as a Therapeutic Target Against Trypanosoma cruzi

There is no effective cure for Chagas disease, which is caused by infection with the arthropod-borne parasite, Trypanosoma cruzi. In the search for new drugs to treat Chagas disease, potential therapeutic targets have been identified by exploiting the differences between the mechanisms involved in intracellular Ca²⁺ homeostasis, both in humans and in trypanosomatids. In the trypanosomatid, intracellular Ca²⁺ regulation requires the concerted action of three intracellular organelles, the endoplasmic reticulum, the single unique mitochondrion, and the acidocalcisomes. The single unique mitochondrion and the acidocalcisomes also play central roles in parasite bioenergetics. At the parasite plasma membrane, a Ca²⁺-⁻ATPase (PMCA) with significant differences from its human counterpart is responsible for Ca²⁺ extrusion; a distinctive sphingosine-activated Ca²⁺ channel controls Ca²⁺ entrance to the parasite interior. Several potential anti-trypansosomatid drugs have been demonstrated to modulate one or more of these mechanisms for Ca²⁺ regulation. The antiarrhythmic agent amiodarone and its derivatives have been shown to exert trypanocidal effects through the disruption of parasite Ca²⁺ homeostasis. Similarly, the amiodarone-derivative dronedarone disrupts Ca²⁺ homeostasis in T. cruzi epimastigotes, collapsing the mitochondrial membrane potential (ΔΨ_m), and inducing a large increase in the intracellular Ca²⁺ concentration ([Ca²⁺]_i) from this organelle and from the acidocalcisomes in the parasite cytoplasm. The same general mechanism has been demonstrated for SQ109, a new anti-tuberculosis drug with potent trypanocidal effect. Miltefosine similarly induces a large increase in the [Ca²⁺]_i acting on the sphingosine-activated Ca²⁺ channel, the mitochondrion and acidocalcisomes. These examples, in conjunction with other evidence we review herein, strongly support targeting Ca²⁺ homeostasis as a strategy against Chagas disease.

Effective Tetradentate Compound Complexes against Leishmania spp. that Act on Critical Enzymatic Pathways of These Parasites

The spectrum and efficacy of available antileishmanial drugs is limited. In the present work we evaluated in vitro the antiproliferative activity of 11 compounds based on tetradentate polyamines compounds against three Leishmania species (L. braziliensis, L. donovani and L. infantum) and the possible mechanism of action. We identified six compounds (3, 5, 6, 7, 8 and 10) effective against all three Leishmania spp both on extracellular and intracellular forms. These six most active leishmanicidal compounds also prevent the infection of host cells. Nevertheless, only compound 7 is targeted against the Leishmania SOD. Meanwhile, on the glucose metabolism the tested compounds have a species-specific effect on Leishmania spp.: L. braziliensis was affected mainly by 10 and 8, L. donovani by 7, and L. infantum by 5 and 3. Finally, the cellular ultrastructure was mainly damaged by 11 in the three Leishmania spp. studied. These identified antileishmania candidates constitute a good alternative treatment and will be further studied.

CYP51 as drug targets for fungi and protozoan parasites: past, present and future

The efficiency of treatment of human infections with the unicellular eukaryotic pathogens such as fungi and protozoa remains deeply unsatisfactory. For example, the mortality rates from nosocomial fungemia in critically ill, immunosuppressed or post-cancer patients often exceed 50%. A set of six systemic clinical azoles [sterol 14α-demethylase (CYP51) inhibitors] represents the first-line antifungal treatment. All these drugs were discovered empirically, by monitoring their effects on fungal cell growth, though it had been proven that they kill fungal cells by blocking the biosynthesis of ergosterol in fungi at the stage of 14α-demethylation of the sterol nucleus. This review briefs the history of antifungal azoles, outlines the situation with the current clinical azole-based drugs, describes the attempts of their repurposing for treatment of human infections with the protozoan parasites that, similar to fungi, also produce endogenous sterols, and discusses the most recently acquired knowledge on the CYP51 structure/function and inhibition. It is our belief that this information should be helpful in shifting from the traditional phenotypic screening to the actual target-driven drug discovery paradigm, which will rationalize and substantially accelerate the development of new, more efficient and pathogen-oriented CYP51 inhibitors.

Sterol 14α-Demethylase Structure-Based Optimization of Drug Candidates for Human Infections with the Protozoan Trypanosomatidae

Sterol 14α-demethylases (CYP51) are cytochrome P450 enzymes essential for sterol biosynthesis in eukaryotes and therapeutic targets for antifungal azoles. Multiple attempts to repurpose antifungals for treatment of human infections with protozoa (Trypanosomatidae) have been undertaken, yet so far none of them have revealed sufficient efficacy. VNI and its derivative VFV are two potent experimental inhibitors of Trypanosomatidae CYP51, effective in vivo against Chagas disease, visceral leishmaniasis, and sleeping sickness and currently under consideration as antiprotozoal drug candidates. However, VNI is less potent against Leishmania and drug-resistant strains of Trypanosoma cruzi and VFV, while displaying a broader spectrum of antiprotozoal activity, and is metabolically less stable. In this work we have designed, synthesized, and characterized a set of close analogues and identified two new compounds (7 and 9) that exceed VNI/VFV in their spectra of antiprotozoal activity, microsomal stability, and pharmacokinetics (tissue distribution in particular) and, like VNI/VFV, reveal no acute toxicity.

Antileishmanial Efficacy and Pharmacokinetics of DB766-Azole Combinations

Given the limitations of current antileishmanial drugs and the utility of oral combination therapy for other infections, developing an oral combination against visceral leishmaniasis should be a high priority. In vitro combination studies with DB766 and antifungal azoles against intracellular Leishmania donovani showed that posaconazole and ketoconazole, but not fluconazole, enhanced DB766 potency. Pharmacokinetic analysis of DB766-azole combinations in uninfected Swiss Webster mice revealed that DB766 exposure was increased by higher posaconazole and ketoconazole doses, while DB766 decreased ketoconazole exposure. In L. donovani-infected BALB/c mice, DB766-posaconazole combinations given orally for 5 days were more effective than DB766 or posaconazole alone. For example, 81% ± 1% (means ± standard errors) inhibition of liver parasite burden was observed for 37.5 mg/kg of body weight DB766 plus 15 mg/kg posaconazole, while 37.5 mg/kg DB766 and 15 mg/kg posaconazole administered as monotherapy gave 40% ± 5% and 21% ± 3% inhibition, respectively. Combination index (CI) analysis indicated that synergy or moderate synergy was observed in six of nine combined dose groups, while the other three were nearly additive. Liver concentrations of DB766 and posaconazole increased in almost all combination groups compared to monotherapy groups, although many increases were not statistically significant. For DB766-ketoconazole combinations evaluated in this model, two were antagonistic, one displayed synergy, and one was nearly additive. These data indicate that the efficacy of DB766-posaconazole and DB766-ketoconazole combinations in vivo is influenced in part by the pharmacokinetics of the combination, and that the former combination deserves further consideration in developing new treatment strategies against visceral leishmaniasis.

An overview of azoles targeting sterol 14α-demethylase for antileishmanial therapy

The azole antifungal drugs are an important class of chemotherapeutic agents with broad-spectrum of activity against yeasts and filamentous fungi, act in the ergosterol biosynthetic pathway through inhibition of the cytochrome P450-dependent enzyme sterol 14α-demethylase. Azole antifungals have also been repurposed for treatment of tropical protozoan infections including human leishmaniasis. Recent advances in molecular biology and computational chemistry areas have increased our knowledge about sterol biochemical pathway in Leishmania parasites. Based on the importance of sterol biosynthetic pathway in Leishmania parasites, we reviewed all studies reported on azoles for potential antileishmanial therapy along their structural and biological aspects. This review may help medicinal chemists for design of new azole-derived antileishmanial drugs.

Nuclear DNA replication and repair in parasites of the genus Leishmania: Exploiting differences to develop innovative therapeutic approaches

Leishmaniasis is a common tropical disease that affects mainly poor people in underdeveloped and developing countries. This largely neglected infection is caused by Leishmania spp, a parasite from the Trypanosomatidae family. This parasitic disease has different clinical manifestations, ranging from localized cutaneous to more harmful visceral forms. The main limitations of the current treatments are their high cost, toxicity, lack of specificity, and long duration. Efforts to improve treatments are necessary to deal with this infectious disease. Many approved drugs to combat diseases as diverse as cancer, bacterial, or viral infections take advantage of specific features of the causing agent or of the disease. Recent evidence indicates that the specific characteristics of the Trypanosomatidae replication and repair machineries could be used as possible targets for the development of new treatments. Here, we review in detail the molecular mechanisms of DNA replication and repair regulation in trypanosomatids of the genus Leishmania and the drugs that could be useful against this disease.

Targeting CYP51 for drug design by the contributions of molecular modeling

CYP51 is an enzyme of sterol biosynthesis pathway present in animals, plants, protozoa and fungi. This enzyme is described as an important drug target that is still of interest. Therefore, in this work, we reviewed the structure and function of CYP51 and explored the molecular modeling approaches for the development of new antifungal and antiprotozoans that target this enzyme. Crystallographic structures of CYP51 of some organisms have already been described in the literature, which enable the construction of homology models of other organisms' enzymes and molecular docking studies of new ligands. The binding mode and interactions of some new series of azoles with antifungal or antiprotozoan activities has been studied and showed important residues of the active site. Molecular modeling is an important tool to be explored for the discovery and optimization of CYP51 inhibitors with better activities, pharmacokinetics, and toxicological profiles.

Synthesis and pharmacological evaluation of mono-arylimidamides as antileishmanial agents

Arylimidamide (AIA) compounds containing two pyridylimidamide terminal groups (bis-AIAs) possess outstanding in vitro antileishmanial activity, and the frontrunner bis-AIA DB766 (2,5-bis[2-(2-isopropoxy)-4-(2-pyridylimino)aminophenyl]furan) is active in visceral leishmaniasis models when given orally. Eighteen compounds containing a single pyridylimidamide terminal group (mono-AIAs) were synthesized and evaluated for their antileishmanial potential. Six of these compounds exhibited sub-micromolar potency against both intracellular Leishmania donovani and Leishmania amazonensis amastigotes, and three of these compounds also displayed selectivity indexes of 25 or greater for the parasites compared to a J774 macrophage cell line. When given orally at a dose of 100 mg/kg/day for five days, compound 1b (N-(3-isopropoxy-4-(5-phenylfuran-2-yl)phenyl)picolinimidamide methanesulfonate) reduced liver parasitemia by 46% in L. donovani-infected mice. Mono-AIAs are thus a new class of candidate molecules for antileishmanial drug development.

Polymerase Chain Reaction Diagnosis of Leishmaniasis: A Species-Specific Approach

Leishmaniasis is an infectious disease caused by protozoan parasites of the genus Leishmania which are transmitted to humans through bites of infected sand flies. The variable clinical manifestations and the evolution of the disease are determined by the infecting species. Recognition at a species level is of utmost importance since this greatly impacts therapy decision making as well as predicts outcome for the disease. This chapter describes the application of polymerase chain reaction (PCR) in the detection of Leishmania parasites across the disease spectrum, including protocols for sample collection and transportation, genomic material extraction, and target amplification methods with special emphasis on PCR amplification of the cytochrome b gene for Leishmania spp. species identification.

Potent In Vitro Antiproliferative Synergism of Combinations of Ergosterol Biosynthesis Inhibitors against Leishmania amazonensis

Leishmaniases comprise a spectrum of diseases caused by protozoan parasites of the Leishmania genus. Treatments available have limited safety and efficacy, high costs, and difficult administration. Thus, there is an urgent need for safer and more-effective therapies. Most trypanosomatids have an essential requirement for ergosterol and other 24-alkyl sterols, which are absent in mammalian cells. In previous studies, we showed that Leishmania amazonensis is highly susceptible to aryl-quinuclidines, such as E5700, which inhibit squalene synthase, and to the azoles itraconazole (ITZ) and posaconazole (POSA), which inhibit C-14α-demethylase. Herein, we investigated the antiproliferative, ultrastructural, and biochemical effects of combinations of E5700 with ITZ and POSA against L. amazonensis. Potent synergistic antiproliferative effects were observed against promastigotes, with fractional inhibitory concentration (FIC) ratios of 0.0525 and 0.0162 for combinations of E5700 plus ITZ and of E5700 plus POSA, respectively. Against intracellular amastigotes, FIC values were 0.175 and 0.1125 for combinations of E5700 plus ITZ and E5700 plus POSA, respectively. Marked alterations of the ultrastructure of promastigotes treated with the combinations were observed, in particular mitochondrial swelling, which was consistent with a reduction of the mitochondrial transmembrane potential, and an increase in the production of reactive oxygen species. We also observed the presence of vacuoles similar to autophagosomes in close association with mitochondria and an increase in the number of lipid bodies. Both growth arrest and ultrastructural/biochemical alterations were strictly associated with the depletion of the 14-desmethyl endogenous sterol pool. These results suggest the possibility of a novel combination therapy for the treatment of leishmaniasis.

Targeting Ergosterol biosynthesis in Leishmania donovani: essentiality of sterol 14 alpha-demethylase

Leishmania protozoan parasites (Trypanosomatidae family) are the causative agents of cutaneous, mucocutaneous and visceral leishmaniasis worldwide. While these diseases are associated with significant morbidity and mortality, there are few adequate treatments available. Sterol 14alpha-demethylase (CYP51) in the parasite sterol biosynthesis pathway has been the focus of considerable interest as a novel drug target in Leishmania. However, its essentiality in Leishmania donovani has yet to be determined. Here, we use a dual biological and pharmacological approach to demonstrate that CYP51 is indispensable in L. donovani. We show via a facilitated knockout approach that chromosomal CYP51 genes can only be knocked out in the presence of episomal complementation and that this episome cannot be lost from the parasite even under negative selection. In addition, we treated wild-type L. donovani and CYP51-deficient strains with 4-aminopyridyl-based inhibitors designed specifically for Trypanosoma cruzi CYP51. While potency was lower than in T. cruzi, these inhibitors had increased efficacy in parasites lacking a CYP51 allele compared to complemented parasites, indicating inhibition of parasite growth via a CYP51-specific mechanism and confirming essentiality of CYP51 in L. donovani. Overall, these results provide support for further development of CYP51 inhibitors for the treatment of visceral leishmaniasis.

Visceral leishmaniasis is the second most lethal parasitic infection after malaria. Other forms of leishmaniasis also cause significant morbidity. However, there are few treatments available, and many cause severe side effects or are associated with the development of resistance. A key difference between mammalian cells and Leishmania parasites is the type of sterol in their membranes: while mammalian cell membranes contain cholesterol, Leishmania parasites use ergosterol. There has therefore been considerable interest in developing inhibitors of sterol biosynthesis pathways to target Leishmania parasites. Sterol 14alpha-demethylase (CYP51) is one of the enzymes in the sterol biosynthesis pathway, and the target of significant drug development research in Leishmania. Here we use a double approach to determine whether this gene is essential in Leishmania donovani, the causative agent of visceral leishmaniasis. We demonstrate via gene knockout and drug targeting approaches that loss or inhibition of CYP51 inhibits L. donovani growth. These results validate CYP51 as a drug target in L. donovani and support further work to develop CYP51-directed therapies for visceral leishmaniasis.

Therapeutic options for old world cutaneous leishmaniasis and new world cutaneous and mucocutaneous leishmaniasis

Estimated worldwide incidence of tegumentary leishmaniasis (cutaneous leishmaniasis [CL] and mucocutaneous leishmaniasis [MCL]) is over 1.5 million cases per year in 82 countries, with 90 % of cases occurring in Afghanistan, Brazil, Iran, Peru, Saudi Arabia and Syria. Current treatments of CL are poorly justified and have sub-optimal effectiveness. Treatment can be based on topical or systemic regimens. These different options must be based on Leishmania species, geographic regions, and clinical presentations. In certain cases of Old World CL (OWCL), lesions can spontaneously heal without any need for therapeutic intervention. Local therapies (thermotherapy, cryotherapy, paromomycin ointment, local infiltration with antimonials) are good options with less systemic toxicity, reserving systemic treatments (azole drugs, miltefosine, antimonials, amphotericin B formulations) mainly for complex cases. The majority of New World CL (NWCL) types require systemic treatment (mainly with pentavalent antimonials), either to speed the healing or to prevent dissemination to oral-nasal mucosa as MCL (NWMCL). These types of lesions are potentially serious and always require systemic-based regimens, mainly antimonials and pentamidine; however, the associated immunotherapy is promising. This paper is an exhaustive review of the published literature on the treatment of OWCL, NWCL and NWMCL, and provides treatment recommendations stratified according to their level of evidence regarding the species of Leishmania implicated and the geographical location of the infection.

Non-healing old world cutaneous leishmaniasis caused by L. infantum in a patient from Spain

BACKGROUND

The prevalence of Old World Cutaneous Leishmaniasis in the Mediterranean region is increasing and in Southern Europe often caused by Leishmania infantum. Spontaneous healing of cutaneous leishmaniasis is commonly observed, especially if caused by L. major, whereas L. infantum associated lesions have been reported with longer disease duration and decreased tendency for self-limitation, however, available information is sparse.

CASE PRESENTATION

We report the case of an otherwise healthy woman from Southern Spain who presented with a seven years persistent, non-healing, painless, central ulcerated, nodular cutaneous lesion with a diameter of 2 cm of the forearm. Cutaneous leishmaniasis was diagnosed by smear and histology, showing large amounts of leishmania amastigotes in subepidermal histiocytes and extensive lymphocyte and plasma cell inflammation. L. infantum as the causative pathogen was confirmed by restriction fragment length polymorphism and microsatellite-PCR. Systemic or visceral involvement was excluded by negative leishmania serology and clinical presentation, relevant concomitant diseases or immunosuppression were excluded including quantification of immunoglobulin levels and lymphocyte phenotyping. Topical and systemic anti-infectious treatment options, often limited in terms of efficacy, tolerability and long lasting treatment duration, were considered. Treatment was successfully performed by surgical extraction in local anaesthesia only.

CONCLUSION

To our knowledge this is the longest reported duration of a L. infantum associated cutaneous leishmaniasis indicating a potential long lasting natural evolution of the disease in an otherwise healthy and immunocompetent patient, however, high parasite density may have reflected a lack of a L. infantum specific immune response. Complete surgical extraction can be successfully performed as treatment.

In vitro activity of the antifungal azoles itraconazole and posaconazole against Leishmania amazonensis

Leishmaniasis, caused by protozoan parasites of the Leishmania genus, is one of the most prevalent neglected tropical diseases. It is endemic in 98 countries, causing considerable morbidity and mortality. Pentavalent antimonials are the first line of treatment for leishmaniasis except in India. In resistant cases, miltefosine, amphotericin B and pentamidine are used. These treatments are unsatisfactory due to toxicity, limited efficacy, high cost and difficult administration. Thus, there is an urgent need to develop drugs that are efficacious, safe, and more accessible to patients. Trypanosomatids, including Leishmania spp. and Trypanosoma cruzi, have an essential requirement for ergosterol and other 24-alkyl sterols, which are absent in mammalian cells. Inhibition of ergosterol biosynthesis is increasingly recognized as a promising target for the development of new chemotherapeutic agents. The aim of this work was to investigate the antiproliferative, physiological and ultrastructural effects against Leishmania amazonensis of itraconazole (ITZ) and posaconazole (POSA), two azole antifungal agents that inhibit sterol C14α-demethylase (CYP51). Antiproliferative studies demonstrated potent activity of POSA and ITZ: for promastigotes, the IC50 values were 2.74 µM and 0.44 µM for POSA and ITZ, respectively, and for intracellular amastigotes, the corresponding values were 1.63 µM and 0.08 µM, for both stages after 72 h of treatment. Physiological studies revealed that both inhibitors induced a collapse of the mitochondrial membrane potential (ΔΨm), which was consistent with ultrastructural alterations in the mitochondrion. Intense mitochondrial swelling, disorganization and rupture of mitochondrial membranes were observed by transmission electron microscopy. In addition, accumulation of lipid bodies, appearance of autophagosome-like structures and alterations in the kinetoplast were also observed. In conclusion, our results indicate that ITZ and POSA are potent inhibitors of L. amazonensis and suggest that these drugs could represent novel therapies for the treatment of leishmaniasis, either alone or in combination with other agents.

Development of liposomes loaded with anti-leishmanial drugs for the treatment of cutaneous leishmaniasis

Cutaneous leishmaniasis is caused by different species of Leishmania parasites and its available treatments have not yet provided a strong consistent result. The weak response of current chemotherapeutics is due to their deficient effects on stealth parasites inside macrophages, rapid clearance from the site of action and systemic side effects in high doses. Liposomal formulation of anti-leishmanial drugs could overcome these problems. In this study, different liposomal formulations of three famous anti-leishmanial drugs: Glucantime®, miltefosine and paromomycin were prepared by a modified freeze-drying double emulsion method. Liposome size, zeta potential and encapsulation efficiency were evaluated, and their imaging was carried out by means of atomic force microscopy. Three formulations were evaluated in vivo by subcutaneous injection into skin lesions caused by Leishmania major in BALB/c mice. Encapsulation efficiency of prepared liposomes was up to 90%; however, they inherited a bimodal size distribution that caused their encapsulation efficiency to decrease to 50% during filtering sterilization. Besides, the effect of surface charge was significant on preparation procedure, size and encapsulation efficiency. All three formulations reduced amastigote counts and lesion size but only miltefosine-loaded formulations had significant therapeutic effects compared with control group (p < 0.05).

Voriconazole suppresses the growth of Leishmania species in vitro

The digenetic protozoan Leishmania is dependent on ergosterol synthesis for growth and viability. We compared the in vitro activity of ergosterol synthesis inhibitor voriconazole with fluconazole and ketoconazole against cutaneous and visceral Leishmania species. We found the IC50 of voriconazole was comparable to ketoconazole and both were superior to fluconazole. Both ketoconazole and voriconazole were active against insect and mammalian stage parasites. This is the first report of the in vitro activity of voriconazole against leishmanial species.

CYP51 structures and structure-based development of novel, pathogen-specific inhibitory scaffolds

CYP51 (sterol 14α-demethylase) is a cytochrome P450 enzyme essential for sterol biosynthesis and the primary target for clinical and agricultural antifungal azoles. The azoles that are currently in clinical use for systemic fungal infections represent modifications of two basic scaffolds, ketoconazole and fluconazole, all of them being selected based on their antiparasitic activity in cellular experiments. By studying direct inhibition of CYP51 activity across phylogeny including human pathogens Trypanosoma brucei, Trypanosoma cruzi and Leishmania infantum, we identified three novel protozoa-specific inhibitory scaffolds, their inhibitory potency correlating well with antiprotozoan activity. VNI scaffold (carboxamide containing β-phenyl-imidazoles) is the most promising among them: killing T. cruzi amastigotes at low nanomolar concentration, it is also easy to synthesize and nontoxic. Oral administration of VNI (up to 400 mg/kg) neither leads to mortality nor reveals significant side effects up to 48 h post treatment using an experimental mouse model of acute toxicity. Trypanosomatidae CYP51 crystal structures determined in the ligand-free state and complexed with several azole inhibitors as well as a substrate analog revealed high rigidity of the CYP51 substrate binding cavity, which must be essential for the enzyme strict substrate specificity and functional conservation. Explaining profound potency of the VNI inhibitory scaffold, the structures also outline guidelines for its further development. First steps of the VNI scaffold optimization have been undertaken; the results presented here support the notion that CYP51 structure-based rational design of more efficient, pathogen-specific inhibitors represents a highly promising direction.

In vitro anti-Trypanosoma cruzi activity of dronedarone, a novel amiodarone derivative with an improved safety profile

Amiodarone, a commonly used antiarrhythmic, is also a potent and selective anti-Trypanosoma cruzi agent. Dronedarone is an amiodarone derivative in which the 2,5-diiodophenyl moiety of the parental drug has been replaced with an unsubstituted phenyl group aiming to eliminate the thyroid toxicity frequently observed with amiodarone treatment. Dronedarone has been approved by the Food and Drug Administration (FDA), and its use as a safe antiarrhythmic has been extensively documented. We show here that dronedarone also has potent anti-T. cruzi activity, against both extracellular epimastigotes and intracellular amastigotes, the clinically relevant form of the parasite. The 50% inhibitory concentrations against both proliferative stages are lower than those previously reported for amiodarone. The mechanism of action of dronedarone resembles that of amiodarone, as it induces a large increase in the intracellular Ca(2+) concentration of the parasite, which results from the release of this ion from intracellular storage sites, including a direct effect of the drug on the mitochondrial electrochemical potential, and through alkalinization of the acidocalcisomes. Our results suggest a possible future repurposed use of dronedarone for the treatment of Chagas' disease.

Leishmaniasis chemotherapy--challenges and opportunities

Although there have been significant advances in the treatment of visceral leishmaniasis (VL), there remain challenges to ensure that treatments effective in India are also effective in other regions of the world and to identify treatment for post kala-azar dermal leishmaniasis as well as the opportunity to develop a safe oral short-course treatment. At the same time, there have been few advances for the treatment of simple or complex forms of cutaneous leishmaniasis (CL), other than topical paromomycin formulations. The main challenge for CL is to ensure that this disease is on the research and development agenda, so that new drugs are evaluated or compounds are screened in appropriate models, and that the standardization of quality of clinical trials is guaranteed. Problems also remain in the treatment of HIV/leishmaniasis co-infected patients. We are some way from having the ideal treatments for VL and CL and drug research and development for these diseases must remain focused.