Synthesis and in vitro evaluation of new 5-substituted 6-nitroimidazooxazoles as antikinetoplastid agents

Identification of Novel Antileishmanial Chemotypes By High-Throughput Virtual and In Vitro Screening

BACKGROUND

Leishmaniasis is a deadly protozoan parasitic disease and a significant health problem in underdeveloped and developing countries. The global spread of the parasite, coupled with the emergence of drug resistance and severe side effects associated with existing treatments, has necessitated the identification of new and potential drugs.

OBJECTIVE

This study aimed to identify promising compounds for the treatment of leishmaniasis by targeting two essential enzymes of Leishmania donovani: trypanothione reductase (Try-R) and trypanothione synthetase (Try-S).

METHODS

High-throughput virtual and in vitro screening of in-house and commercial databases was conducted. A pharmacophore model with seven features was developed and validated using the Guner-Henery method. The pharmacophore-based virtual screening yielded 690 hits, which were further filtered through Lipinski's rule, ADMET analysis, and molecular docking against Try-R and Try-S. Molecular dynamics studies were performed on selected compounds, and in vitro experiments were conducted to evaluate their activity against the promastigote and amastigote forms of L. donovani.

RESULTS

The virtual screening and subsequent analysis identified 33 promising compounds. Molecular dynamics studies of two compounds (comp-1 and comp-2) demonstrated stable binding interactions with the target enzymes and high affinity. In vitro experiments revealed that 13 compounds exhibited moderate activity against both the promastigote (IC50, 41 µM-76 µM) and the amastigote (IC50, 44 µM-72 µM) forms of L. donovani. Compounds 1 and 2 showed the highest percent inhibition and the lowest IC50 values.

CONCLUSION

The identified compounds demonstrated significant inhibitory activity against Leishmania donovani and stable interactions with target enzymes. These findings suggest that the compounds could serve as promising leads for developing new treatments for leishmaniasis.

New drug discovery strategies for the treatment of benznidazole-resistance in Trypanosoma cruzi, the causative agent of Chagas disease

INTRODUCTION

Benznidazole, the drug of choice for treating Chagas Disease (CD), has significant limitations, such as poor cure efficacy, mainly in the chronic phase of CD, association with side effects, and parasite resistance. Understanding parasite resistance to benznidazole is crucial for developing new drugs to treat CD.

AREAS COVERED

Here, the authors review the current understanding of the molecular basis of benznidazole resistance. Furthermore, they discuss the state-of-the-art methods and critical outcomes employed to evaluate the efficacy of potential drugs against T. cruzi, aiming to select better compounds likely to succeed in the clinic. Finally, the authors describe the different strategies employed to overcome resistance to benznidazole and find effective new treatments for CD.

EXPERT OPINION

Resistance to benznidazole is a complex phenomenon that occurs naturally among T. cruzi strains. The combination of compounds that inhibit different metabolic pathways of the parasite is an important strategy for developing a new chemotherapeutic protocol.

Evaluation of 2,3-dihydroimidazo[2,1-b]oxazole and imidazo[2,1-b]oxazole derivatives as chemotherapeutic agents

Imidazo[2,1-b]oxazole and 2,3-dihydroimidazo[2,1-b]oxazole ring systems are commonly employed in therapeutically active molecules. In this article, the authors review the utilization of these core scaffolds as chemotherapeutic agents from 2018 to 2022. These scaffolds possess many important biological activities including antimicrobial and anticancer, among others. This review covers their biological activities and structure-activity relationships. One of the most important drugs in this class of compounds is the antitubercular agent delamanid. In this paper, the compounds structure-activity relationship and preclinical and clinical trial data are thoroughly presented.

Nitro compounds against trypanosomatidae parasites: Heroes or villains?

Chagas disease and Human African trypanosomiasis (HAT) are caused by Trypanosoma cruzi, T. brucei rhodesiense or T. b. gambiense parasites, respectively; while Leishmania is caused by parasites from the Leishmania genus. In recent years, many efforts have been addressed to develop inhibitors against these parasites, especially nitro-containing derivatives, which can interfere with essential enzymes from the protozoa. In this review, all anti-trypanosomatidae nitrocompounds reported so far are shown herein, highlighting their activities and SAR analyses, providing all the benefits and problems associated with this ambiguous chemical group. Finally, this review paper will be useful for many research teams around the world, which are searching for novel trypanocidal and leishmanicidal agents.

Synthesis, In Vitro Antiproliferative Activity, and In Silico Evaluation of Novel Oxiranyl-Quinoxaline Derivatives

The quinoxaline core is a promising scaffold in medicinal chemistry. Multiple quinoxaline derivatives, such as the topoisomerase IIβ inhibitor XK-469 and the tissue transglutaminase 2 inhibitor GK-13, have been evaluated for their antiproliferative activity. Previous work reported that quinoxaline derivatives bearing an oxirane ring present antiproliferative properties against neuroblastoma cell lines SK-N-SH and IMR-32. Likewise, quinoxalines with an arylethynyl group displayed promising antineoplastic properties against glioblastoma and lung cancer cell lines, U87-MG and A549 respectively. Here, 40 new quinoxaline derivatives bearing an oxirane ring were synthesized using a tetrakis(dimethylamino)ethylene (TDAE) strategy and a Sonogashira cross-coupling reaction. Each reaction with TDAE furnished a pair of diastereoisomers cis and trans. These new compounds formed two series according to the substitution of position 2 on the quinoxaline core, with chlorine or phenylacetylene respectively. Each of these isomers was evaluated for antiproliferative activity against neuroblastoma cell lines SK-N-SH and IMR-32 by MTT assay. All cell viability assay results were analyzed using R programming, as well as a statistical comparison between groups of compounds. Our evaluation showed no difference in drug sensitivity between the two neuroblastoma cell lines. Moreover, trans derivatives were observed to display better activities than cis derivatives, leading us to conclude that stereochemistry plays an important role in the antiproliferative activity of these compounds. Further support for this hypothesis is provided by the lack of improvement in antineoplastic activity following the addition of the phenylacetylene moiety, probably due to steric hindrance. As a result, compounds with nitrofuran substituents from the TDAE series demonstrated the highest antiproliferative activity with IC₅₀ = 2.49 ± 1.33 μM and IC₅₀ = 3.96 ± 2.03 μM for compound 11a and IC₅₀ = 5.3 ± 2.12 μM and IC₅₀ = 7.12 ± 1.59 μM for compound 11b against SK-N-SH and IMR-32, respectively. Furthermore, an in silico study was carried out to evaluate the mechanism of action of our lead compounds and predict their pharmacokinetic properties.

Probing O-substituted Nifuroxazide analogues against Leishmania: Synthesis, in vitro efficacy, and hit/lead identification

Leishmaniasis is a neglected tropical disease affecting millions of people worldwide, with 650 000 to 1.1 million new infections reported annually by the World Health Organization. Current antileishmanial treatments are unsatisfactory due to the development of parasitic resistance and the toxicity associated with the drugs used, and this highlights the need for the development of new antileishmanial drugs. In this study, a series of nifuroxazide analogues were synthesized in a single step reaction and investigated for their antileishmanial potential. The sulfonate 1l, bearing pyridine ring, was deemed an antileishmanial hit, targeting the amastigotes of Leishmania (L.) donovani and L. major, the pathogens of visceral and cutaneous leishmaniasis, respectively, with micromolar potencies. The benzyl analogues 2c and 2d were also confirmed as submicromolar active leads against amastigotes of L. major. These analogues stand as promising candidates for further investigation involving the evaluation of their in vivo activities and molecular targets.

Recent advancements in anti-leishmanial research: Synthetic strategies and structural activity relationships

Leishmaniasis is a parasitic neglected tropical disease caused by various species of Leishmania parasite. Despite tremendous advancements in the therapeutic sector and drug development strategies, still the existing anti-leishmanial agents are associated with some clinical issues like drug resistance, toxicity and selectivity. Therefore, several research groups are continuously working towards the development of new therapeutic candidates to overcome these issues. Many potential heterocyclic moieties have been explored for this purpose including triazoles, chalcones, chromone, thiazoles, thiosemicarbazones, indole, quinolines, etc. It is evident from the literature that the majority of anti-leishmanial agents act by interacting with key regulators including PTR-I, DHFR, LdMetAP1, MAPK, 14 α-demethylase and pteridine reductase-I, etc. Also, these tend to induce the production of ROS which causes damage to parasites. In the present compilation, authors have summarized various significant synthetic procedures for anti-leishmanial agents reported in recent years. A brief description of the pharmacological potentials of synthesized compounds along with important aspects related to structural activity relationship has been provided. Important docking outcomes highlighting the possible mode of interaction for the reported compounds have also been included. This review would be helpful to the scientific community to design newer strategies and also to develop novel therapeutic candidates against leishmaniasis.

Chagas Disease Chemotherapy: What Do We Know So Far?

Chagas disease is a Neglected Tropical Disease (NTD), and although endemic in Latin America, affects around 6-7 million people infected worldwide. The treatment of Chagas disease is based on benznidazole and nifurtimox, which are the only available drugs. However, they are not effective during the chronic phase and cause several side effects. Furthermore, BZ promotes cure in 80% of the patients in the acute phase, but the cure rate drops to 20% in adults in the chronic phase of the disease. In this review, we present several studies published in the last six years, which describes the antiparasitic potential of distinct drugs, from the synthesis of new compounds aiming to target the parasite, as well as the repositioning and the combination of drugs. We highlight several compounds for having shown results that are equivalent or superior to BZ, which means that they should be further studied, either in vitro or in vivo. Furthermore, we stand out the differences in the effects of BZ on the same strain of T. cruzi, which might be related to methodological differences such as parasite and cell ratios, host cell type and the time of adding the drug. In addition, we discuss the wide variety of strains and also the cell types used as a host cell, which makes it difficult to compare the trypanocidal effect of the compounds.

Recent Progress in the Discovery and Development of 2-Nitroimidazooxazines and 6-Nitroimidazooxazoles to Treat Tuberculosis and Neglected Tropical Diseases

Nitroimidazole drugs have a long history as therapeutic agents to treat bacterial and parasitic diseases. The discovery in 1989 of a bicyclic nitroimidazole lead, displaying in vitro and in vivo antitubercular activity, spurred intensive exploration of this and related scaffolds, which led to the regulatory approval of pretomanid and delamanid as a new class of tuberculosis drugs. Much of the discovery work related to this took place over a 20-year period ending in 2010, which is covered in a number of cited reviews. This review highlights subsequent research published over the 2011–August 2020 timeframe, and captures detailed structure–activity relationship studies and synthetic strategies directed towards uncovering newer generation drugs for both tuberculosis and selected neglected tropical diseases. Additionally, this review presents in silico calculations relating to the drug-like properties of lead compounds and clinical agents, as well as chemical development and manufacturing processes toward providing bulk drug supplies.