Miltefosine: First Oral Drug for Treatment of Visceral Leishmaniasis

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

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

Synthesis, Antimalarial, Antileishmanial, and Cytotoxicity Activities and Preliminary In Silico ADMET Studies of 2-(7-Chloroquinolin-4-ylamino)ethyl Benzoate Derivatives

A series of heterocyclic chloroquine hybrids, containing a chain of two carbon atoms at position four of the quinolinic chain and acting as a link between quinoline and several benzoyl groups, is synthesized and screened in vitro as an inhibitor of β-hematin formation and in vivo for its antimalarial activity against chloroquine-sensitive strains of Plasmodium berghei ANKA in this study. The compounds significantly reduced haeme crystallization, with IC50 values < 10 µM. The values were comparable to chloroquine's, with an IC50 of 1.50 ± 0.01 µM. The compounds 4c and 4e prolonged the average survival time of the infected mice to 16.7 ± 2.16 and 14.4 ± 1.20 days, respectively. We also studied the effect of the compounds 4b, 4c, and 4e on another important human parasite, Leishmania mexicana, which is responsible for cutaneous leishmaniasis, demonstrating a potential leishmanicidal effect against promasigotes, with an IC50 < 10 µM. Concerning the possible mechanism of action of these compounds on Lesihmania mexicana, we performed experiments demonstrating that these three compounds could induce the collapse of the parasite mitochondrial electrochemical membrane potential (Δφ). The in vitro cytotoxicity assays against mammalian cancerous and noncancerous human cell lines showed that the studied compounds exhibit low cytotoxic effects. The ADME/Tox analysis predicted moderate lipophilicity values, low unbound fraction values, and a poor distribution for these compounds. Therefore, moderate bioavailability was expected. We calculated other molecular descriptors, such as the topological polar surface area, according to Veber's rules, and except for 2 and 4i, the rest of the compounds violated this descriptor, demonstrating the low antimalarial activity of our compounds in vivo.

Nanotechnology-Based Strategies in Parasitic Disease Management: From Prevention to Diagnosis and Treatment

Parasitic infections are a major global health issue causing significant mortality and morbidity. Despite substantial advances in the diagnostics and treatment of these diseases, the currently available options fall far short of expectations. From diagnosis and treatment to prevention and control, nanotechnology-based techniques show promise as an alternative approach. Nanoparticles can be designed with specific properties to target parasites and deliver antiparasitic medications and vaccines. Nanoparticles such as liposomes, nanosuspensions, polymer-based nanoparticles, and solid lipid nanoparticles have been shown to overcome limitations such as limited bioavailability, poor cellular permeability, nonspecific distribution, and rapid drug elimination from the body. These nanoparticles also serve as nanobiosensors for the early detection and treatment of these diseases. This review aims to summarize the potential applications of nanoparticles in the prevention, diagnosis, and treatment of parasitic diseases such as leishmaniasis, malaria, and trypanosomiasis. It also discusses the advantages and disadvantages of these applications and their market values and highlights the need for further research in this field.

Assessing nystatin cream treatment efficacy against Leishmania (L.) amazonensis infection in BALB/c model

The current scenario for cutaneous leishmaniasis treatment includes the use of first and second-choice drugs, both therapeutic strategies presenting several adverse effects and being related to an increment of treatment-refractory parasite strains. These facts encourage the search for new treatment approaches, including repositioning drugs, such as nystatin. Although some in vitro assays show that this polyene macrolide compound has leishmanicidal activity, no in vivo evidence for a similar activity has been shown so far for the commercial nystatin cream formulation (25,000 IU/g). This work assessed the effects of nystatin cream administered on mice in an amount to completely cover the paw surface of BALB/c mice infected with L. (L.) amazonensis once a day, until a total of up to 20 doses. The data presented herein points to unequivocal evidence that this formulation is related to a statistically significant reduction of swelling/edema in mice paws when compared to animal groups not submitted to this treatment regimen after the fourth week of infection: lesion sizes at the sixth (p = 0.0159), seventh (p = 0.0079) and eighth (p = 0.0079) week. Furthermore, infection reduction relates to a decrease in parasite load in the footpad (∼48%) and in draining lymph nodes (∼68%) at 8th weeks post-infection. This is the first report of the effectiveness of nystatin cream used as a topical treatment in BALB/c model for cutaneous leishmaniasis.

Synthesis, Leishmanicidal, Trypanocidal, Antiproliferative Assay and Apoptotic Induction of (2-Phenoxypyridin-3-yl)naphthalene-1(2H)-one Derivatives

The coexistence of leishmaniasis, Chagas disease, and neoplasia in endemic areas has been extensively documented. The use of common drugs in the treatment of these pathologies invites us to search for new molecules with these characteristics. In this research, we report 16 synthetic chalcone derivatives that were investigated for leishmanicidal and trypanocidal activities as well as for antiproliferative potential on eight human cancers and two nontumor cell lines. The final compounds 8−23 were obtained using the classical base-catalyzed Claisen−Schmidt condensation. The most potent compounds as parasiticidal were found to be 22 and 23, while compounds 18 and 22 showed the best antiproliferative activity and therapeutic index against CCRF-CEM, K562, A549, and U2OS cancer cell lines and non-toxic VERO, BMDM, MRC-5, and BJ cells. In the case of K562 and the corresponding drug-resistant K562-TAX cell lines, the antiproliferative activity has shown a more significant difference for compound 19 having 10.3 times higher activity against the K562-TAX than K562 cell line. Flow cytometry analysis using K562 and A549 cell lines cultured with compounds 18 and 22 confirmed the induction of apoptosis in treated cells after 24 h. Based on the structural analysis, these chalcones represent new compounds potentially useful for Leishmania, Trypanosoma cruzi, and some cancer treatments.

In vitro evaluation and in vivo efficacy of nitroimidazole-sulfanyl ethyl derivatives against Leishmania (V.) braziliensis and Leishmania (L.) mexicana

The aim of this study was to synthesize several small molecules of the type 5-nitroimidazole-sulfanyl and evaluate biological properties against the main Leishmania species that cause cutaneous leishmaniasis in Venezuela. Final compounds 4-7 were generated through simple nucleophilic substitution of 1-(2-chloroethyl)-2-methyl-5-nitroimidazole 3 with 2-mercaptoethanol, 1-methyl-2-mercaptoethanol, and 2-thyolacetic acid derivative. Compound 8 was synthesized via a coupling reaction between 7 and (S)-Methyl 2-amino-4-methylpentanoate hydrochloride. The inhibitory concentrations of (3, 4, 7, 8) against Leishmania (L.) mexicana and (V.) braziliensis in promastigotes and experimentally infected macrophages were determined by in vitro activity assays. Compounds 7 and 8 shown high activity against both species of Leishmania and were selected for the in vivo evaluation. Animals were infected with promastigotes of the two species and divided into four groups of ten (10) animals and a control group. Intralesional injection way was used for the treatment. The parasitological diagnostic after treatment was obtained by PCR using species specific oligonucleotides. The two Leishmania species were susceptible to compounds 7 and 8 in vivo assays. The results indicated that both compounds reduce significantly (96%) the size of the lesion and cure 63% of the mice infected with L (L) mexicana or L (V) braziliensis as was determined by PCR. The results are indicating that both compounds may represent an alternative treatment for these two Leishmania species.

Antileishmanial potential of immunomodulator gallic acid against experimental murine visceral leishmaniasis

The menace of the enfeebling disease leishmaniasis prevails due to the inaccessibility of effective vaccine and chemotherapy. Hence in the pursuit of finding novel alternative options with reasonable efficacy, immunomodulation, leishmanicidal activity and fewer side effects, screening of compounds from natural sources is needed. This study was focused on in vitro and in vivo antileishmanial screening of gallic acid (GA) against Leishmania donovani infection in BALB/c mice. GA showed in vitro parasiticidal activity and IC₅₀  value of 19.59 ± 0.74 µg/ml and is able to arrest cell cycle at the sub-G0/G1 phase. The therapeutic potential of gallic acid was assessed in the L. donovani-infected BALB/c mice. GA reported a reduction in parasite burden and augmentation of CD4⁺ and CD8⁺ T lymphocytes. Also, the polarization of mouse immune status to protective Th1 response was evidenced by increased delayed-type hypersensitivity response and levels of IgG2a, reactive oxygen species and nitric oxide. GA was reported to be safe and non-toxic to human cell line THP-1 and also to the liver and kidney of mice. Hence, the findings of the present study indicate the possible role of GA in the strengthening of host immune system and thus facilitating the clearance of leishmanial infection and conferring protection.

Modeling and simulation study to identify threonine synthase as possible drug target in Leishmania major

Leishmaniasis is one of the most neglected tropical diseases that demand immediate attention to the identification of new drug targets and effective drug candidates. The present study demonstrates the possibility of using threonine synthase (TS) as a putative drug target in leishmaniasis disease management. We report the construction of an effective homology model of the enzyme that appears to be structurally as well as functionally well conserved. The 200 nanosecond molecular dynamics data on TS with and without pyridoxal phosphate (PLP) shed light on mechanistic details of PLP-induced conformational changes. Moreover, we address some important structural and dynamic interactions in the PLP binding region of TS that are in good agreement with previously speculated crystallographic estimations. Additionally, after screening more than 44,000 compounds, we propose 10 putative inhibitor candidates for TS based on virtual screening data and refined Molecular Mechanics Generalized Born Surface Area calculations. We expect that structural and functional dynamics data disclosed in this study will help initiate experimental endeavors toward establishing TS as an effective antileishmanial drug target.

Synthesis, Biological Evaluation, Structure-Activity Relationship, and Mechanism of Action Studies of Quinoline-Metronidazole Derivatives Against Experimental Visceral Leishmaniasis

In our efforts to identify novel chemical scaffolds for the development of antileishmanial agents, a series of quinoline-metronidazole hybrid compounds was synthesized and tested against the murine model of visceral leishmaniasis. Among all synthesized derivatives, 15b and 15i showed significant antileishmanial efficacy against both extracellular promastigote (IC₅₀ 9.54 and 5.42 μM, respectively) and intracellular amastigote (IC₅₀ 9.81 and 3.75 μM, respectively) forms of Leishmania donovani with negligible cytotoxicity toward the host (J774 macrophages, Vero cells). However, compound 15i effectively inhibited the parasite burden in the liver and spleen (>80%) of infected BALB/c mice. Mechanistic studies revealed that 15i triggers oxidative stress which induces bioenergetic collapse and apoptosis of the parasite by decreasing ATP production and mitochondrial membrane potential. Structure-activity analyses and pharmacokinetic studies suggest 15i as a promising antileishmanial lead and emphasize the importance of quinoline-metronidazole series as a suitable platform for the future development of antileishmanial agents.

Mechanism of Action of Miltefosine on Leishmania donovani Involves the Impairment of Acidocalcisome Function and the Activation of the Sphingosine-Dependent Plasma Membrane Ca2+ Channel

Leishmania donovani is the causing agent of visceral leishmaniasis, a common infection that affects millions of people from the most underdeveloped countries. Miltefosine is the only oral drug to treat infections caused by L. donovani Nevertheless, its mechanism of action is not well understood. While miltefosine inhibits the synthesis of phosphatidylcholine and also affects the parasite mitochondrion, inhibiting the cytochrome c oxidase, it is to be expected that this potent drug also produces its effect through other targets. In this context, it has been reported that the disruption of the intracellular Ca²⁺ homeostasis represents an important object for the action of drugs in trypanosomatids. Recently, we have described a plasma membrane Ca²⁺ channel in Leishmania mexicana, which is similar to the L-type voltage-gated Ca²⁺ channel (VGCC) present in humans. Remarkably, the parasite Ca²⁺ channel is activated by sphingosine, while the L-type VGCC is not affected by this sphingolipid. In the present work we demonstrated that, similarly to sphingosine, miltefosine is able to activate the plasma membrane Ca²⁺ channel from L. donovani Interestingly, nifedipine, the classical antagonist of the human channel, was not able to fully block the parasite plasma membrane Ca²⁺ channel, indicating that the mechanism of interaction is not identical to that of sphingosine. In this work we also show that miltefosine is able to strongly affect the acidocalcisomes from L. donovani, inducing the rapid alkalinization of these important organelles. In conclusion, we demonstrate two new mechanisms of action of miltefosine in L. donovani, both related to disruption of parasite Ca²⁺ homeostasis.