DNDI-6174 is a preclinical candidate for visceral leishmaniasis that targets the cytochrome bc1

Advancing Treatment for Leishmaniasis: From Overcoming Challenges to Embracing Therapeutic Innovations

Protozoan parasite infections, particularly leishmaniasis, present significant public health challenges in tropical and subtropical regions, affecting socio-economic status and growth. Despite advancements in immunology, effective vaccines remain vague, leaving drug treatments as the primary intervention. However, existing medications face limitations, such as toxicity and the rise of drug-resistant parasites. This presents an urgent need to identify new therapeutic targets for leishmaniasis treatment. Understanding the complex life cycle of Leishmania and its survival in host macrophages can provide insights into potential targets for intervention. Current treatments, including antimonials, amphotericin B, and miltefosine, are constrained by side effects, costs, resistance, and reduced efficacy. Exploring novel therapeutic targets within the parasite's physiology, such as key metabolic enzymes or essential surface proteins, may lead to the development of more effective and less toxic drugs. Additionally, innovative strategies like drug repurposing, combination therapies, and nanotechnology-based delivery systems could enhance efficacy and combat resistance, thus improving anti-leishmanial therapies.

The latest progress in assay development in leishmaniasis drug discovery: a review of the available papers on PubMed from the past year

INTRODUCTION

Leishmaniasis is a significant neglected tropical disease with limited treatment options that urgently requires ongoing efforts in drug discovery. Recent advances have focused on the development of new assays and methods to identify effective therapeutic candidates.

AREAS COVERED

This review explores recent trends and methodologies in leishmaniasis drug discovery, with a particular focus on in silico and in vitro studies, as well as in vivo validation, using animal models. A detailed analysis of recent studies was provided, discussing the methodologies employed, such as manual and automated parasite quantification, and the use of fluorescence and luminescence-based techniques. Additionally, global research trends were analyzed, highlighting the leading countries in scientific output and the collaborative efforts driving advancements in this field.

EXPERT OPINION

The field of leishmaniasis drug discovery has rapidly progressed in the last years, but the lack of standardized methodologies and limited in vivo validation remain significant hurdles. To advance promising treatments to clinical trials, cross-validation of preclinical findings and interdisciplinary collaboration are essential. Increased funding and global partnerships are also crucial to accelerate the discovery and development of alternative and effective therapies.

Synthesis and in vitro leishmanicidal activity of novel N-arylspermidine derivatives

This work describes the synthesis and biological evaluation of hitherto unknown N-arylspermidine derivatives 3. Compounds 3 were efficiently prepared from cyclic amidines through a novel synthetic approach comprising alkylation with ω-halonitriles followed by reduction. The cyclic N-arylamidine directs the alkylation to the unsubstituted nitrogen and also provides the N-benzyl group present in the triamine after simultaneous reduction of the resulting quaternary salt 2 and the cyano group. The N-aryl spermidines were tested in Leishmania infantum promastigotes and also in the more challenging form intracellular amastigotes. The compounds toxicity was also assessed in two cell lines, THP-1 and HepG2. In silico physicochemical and ADME predictions were also carried out. Eight out of ten compounds displayed EC50 around 5 µM against L. infantum intracellular amastigotes. Among them, derivatives 3c, 3d, and 3h showed potency in the low micromolar range with SI > 5 and suitable predicted physicochemical ADME properties. The antileishmanial activity of the compounds would rely on the N-arylspermidine moiety, as assessed by evaluation of related substructures which were inactive. This first series of compounds, among which two derivatives (3b,h) displayed EC50 values comparable to Miltefosine, represent a good starting point for further studies and multiparametric optimization to obtain more potent and selective candidates for the treatment of this neglected tropical disease.

Anti-leishmanial therapies: overcoming current challenges with emerging therapies

INTRODUCTION

Leishmaniasis, including visceral, cutaneous, and mucocutaneous forms, present a major health challenge in tropical regions. Current antileishmanial medications has significant limitations, creating a critical need for novel therapies that are safe and cost-effective with a shorter duration of treatment.

AREAS COVERED

This review explores the critical aspects of existing antileishmanial therapy and targets for future therapeutic developments. It emphasizes the need for new treatment options due to drug resistance, low success rates, toxicity, and high prices associated with current medications. The different forms of leishmaniasis, their clinical manifestations, the challenges associated with their treatment and emerging treatment options are explored in detail.

EXPERT OPINION

The first anti-leishmanial drug pentavalent antimony (SbV) was invented more than 100 years back. Since then, this compound has been used for all forms of leishmaniasis worldwide. For more than 70-80 years after discovery of SbV, no new antileishmanial drugs were developed, reflecting the lack of interest from academia or pharma industry. All three new treatments (Amphotericin-B, paromomycin and miltefosine) which underwent the clinical trials were repurposed drugs. The current pipeline for antileishmanial drugs is empty, with LXE 408 being the only potential drug reaching phase II clinical trial.

Nucleoside Analogues for Chagas Disease and Leishmaniasis Therapy: Current Status and Future Perspectives

Chagas disease and leishmaniasis are two neglected tropical diseases that affect millions of people in low- and middle-income tropical countries. These diseases caused by protozoan parasites pose significant global health challenges, which have been exacerbated by the recent COVID-19 pandemic. There is an urgent need for novel therapeutics as current treatments are limited by toxicity and drug resistance. Nucleoside analogues, which have been extensively studied and successfully applied in antiviral and antitumor therapies, hold potential that has yet to be fully explored for treating these neglected diseases. In this review, we discuss the use of nucleoside analogues as promising therapeutic agents for Chagas disease and leishmaniasis. After briefly examining the pathology, progression, and current treatment options for these diseases, we provide a comprehensive analysis of the status of nucleoside analogues and explore their prospects. By outlining the current landscape and future directions, this review aims to guide research and development efforts towards more effective nucleoside-based treatments for Chagas disease and leishmaniasis.

Investigational new drugs for the treatment of leishmaniasis

INTRODUCTION

Over the past 20 years, significant progress has been made in anti-leishmanial therapy. Three new drugs/formulations are available for the treatment of various forms of leishmaniasis, namely oral miltefosine, paromomycin and liposomal amphotericin B. However, these advances in drug development have added considerable complexity for clinicians including toxicity, emergence of resistance and decreased sensitivity of available drugs. The development of newer drugs with less toxicity and more efficacy is urgently needed.

AREAS COVERED

This review comprehensively examines the latest developments and current status of antileishmanial drugs for the treatment of leishmaniasis across the world. Several new investigational drugs that showed anti-leishmanial activity under in vitro or in vivo conditions and either underwent the phase-I/II clinical trials or are on the verge of entering the trials were reviewed. We also delve into the challenges of drug resistance and discuss the emergence of new and effective antileishmanial compounds.

EXPERT OPINION

The available treatments for leishmaniasis are limited in number, toxic, expensive, and demand extensive healthcare resources. Every available antileishmanial drug is associated with several disadvantages, such as drug resistance and toxicity or high cost. Miltefosine is potentially teratogenic. New antileishmanial drugs/treatment modalities are sorely needed for expanding future treatment options.

Identification and Validation of Compounds Targeting Leishmania major Leucyl-Aminopeptidase M17

Leishmaniasis is a neglected tropical disease; there is currently no vaccine and treatment is reliant upon a handful of drugs suffering from multiple issues including toxicity and resistance. There is a critical need for development of new fit-for-purpose therapeutics, with reduced toxicity and targeting new mechanisms to overcome resistance. One enzyme meriting investigation as a potential drug target in Leishmania is M17 leucyl-aminopeptidase (LAP). Here, we aimed to chemically validate LAP as a drug target in L. major through identification of potent and selective inhibitors. Using RapidFire mass spectrometry, the compounds DDD00057570 and DDD00097924 were identified as selective inhibitors of recombinant Leishmania major LAP activity. Both compounds inhibited in vitro growth of L. major and L. donovani intracellular amastigotes, and overexpression of LmLAP in L. major led to reduced susceptibility to DDD00057570 and DDD00097924, suggesting that these compounds specifically target LmLAP. Thermal proteome profiling revealed that these inhibitors thermally stabilized two M17 LAPs, indicating that these compounds selectively bind to enzymes of this class. Additionally, the selectivity of the inhibitors to act on LmLAP and not against the human ortholog was demonstrated, despite the high sequence similarities LAPs of this family share. Collectively, these data confirm LmLAP as a promising therapeutic target for Leishmania spp. that can be selectively inhibited by drug-like small molecules.

Discovery and Optimization of Tambjamines as a Novel Class of Antileishmanial Agents

Leishmaniasis is a neglected tropical disease that is estimated to afflict over 12 million people. Current drugs for leishmaniasis suffer from serious deficiencies, including toxicity, high cost, modest efficacy, primarily parenteral delivery, and emergence of widespread resistance. We have discovered and developed a natural product-inspired tambjamine chemotype, known to be effective against Plasmodium spp, as a novel class of antileishmanial agents. Herein, we report in vitro and in vivo antileishmanial activities, detailed structure-activity relationships, and metabolic/pharmacokinetic profiles of a large library of tambjamines. A number of tambjamines exhibited excellent potency against both Leishmania mexicana and Leishmania donovani parasites with good safety and metabolic profiles. Notably, tambjamine 110 offered excellent potency and provided partial protection to leishmania-infected mice at 40 and/or 60 mg/kg/10 days of oral treatment. This study presents the first account of antileishmanial activity in the tambjamine family and paves the way for the generation of new oral antileishmanial drugs.

A promising pipeline of preclinical drug candidates for leishmaniasis and chronic Chagas' disease

The drug discovery pipeline for leishmaniasis and trypanosomiasis has been filling with novel chemical entities with known mechanisms of action. González et al. and Braillard et al. report a cytochrome bc1 complex inhibitor as another promising preclinical candidate for visceral leishmaniasis (VL) and, in combination with benznidazole, for chronic Chagas' disease (CCD).

Short-course combination treatment for experimental chronic Chagas disease

Chagas disease, caused by the protozoan parasite Trypanosoma cruzi, affects millions of people in the Americas and across the world, leading to considerable morbidity and mortality. Current treatment options, benznidazole (BNZ) and nifurtimox, offer limited efficacy and often lead to adverse side effects because of long treatment durations. Better treatment options are therefore urgently required. Here, we describe a pyrrolopyrimidine series, identified through phenotypic screening, that offers an opportunity to improve on current treatments. In vitro cell-based washout assays demonstrate that compounds in the series are incapable of killing all parasites; however, combining these pyrrolopyrimidines with a subefficacious dose of BNZ can clear all parasites in vitro after 5 days. These findings were replicated in a clinically predictive in vivo model of chronic Chagas disease, where 5 days of treatment with the combination was sufficient to prevent parasite relapse. Comprehensive mechanism of action studies, supported by ligand-structure modeling, show that compounds from this pyrrolopyrimidine series inhibit the Qi active site of T. cruzi cytochrome b, part of the cytochrome bc1 complex of the electron transport chain. Knowledge of the molecular target enabled a cascade of assays to be assembled to evaluate selectivity over the human cytochrome b homolog. As a result, a highly selective and efficacious lead compound was identified. The combination of our lead compound with BNZ rapidly clears T. cruzi parasites, both in vitro and in vivo, and shows great potential to overcome key issues associated with currently available treatments.