Slow pace of antileishmanial drug development

Identification of novel inhibitors from Rubus ellipticus as anti-leishmanial agents targeting DDX3-DEAD box RNA helicase of Leishmania donovani

Visceral leishmaniasis (VL), caused by Leishmania donovani, remains challenging to treat due to severe side effects and increasing drug resistance associated with current chemotherapies. Our study investigates the anti-leishmanial potential of Rubus ellipticus from Uttarakhand, India, with extracts prepared from leaves and stems using ethanol and hexane. Advanced GC-MS analysis identified over 100 bioactive compounds, which were screened using molecular docking to assess their binding to LdHEL-67, a DDX3-DEAD box RNA helicase of L. donovani. Our results spotlighted nine major compounds with high binding energy, which were then further analyzed for ADMET properties and toxicity predictions, demonstrating their promising pharmacokinetic profiles. Among these, clionasterol emerged as the standout compound, displaying superior results in all in silico analyses compared to Amphotericin B (the control). Notably, clionasterol was present in significant proportions across all the mentioned extracts. Subsequent treatment with these extracts led to a remarkable reduction in the intracellular amastigote and axenic amastigote, and promastigote forms of L. donovani and non-toxic to THP-1-derived macrophages. Moreover, the extracts induced apoptotic effects, as evidenced by the fragmentation of parasitic genomic DNA. This study marks a significant leap in developing herbal-based, target-specific inhibitors against VL. Hence, our findings highlight the immense potential of R. ellipticus as a natural treatment for VL.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-024-04183-4.

One-pot synthesis of polyhydroquinoline-1,2,3-triazole hybrids in deep eutectic solvent as anti-leishmanial agents and molecular modeling studies

The novel hybrids with 1,2,3-triazole and polyhydroquinoline scaffolds were successfully synthesized by multicomponent reaction of propargyloxybenzaldehyde, 1,3-cyclohexadione, ethylacetoacetate and ammonium acetate followed through click reaction in the presence of deep eutectic solvent ChCl/ZnCl2 as an efficient catalyst. Their anti-leishmanial activity was evaluated against amastigote and promastigote forms of L. tropica, L. major, and two different species of L. infantum. Furthermore, to determine the cytotoxicity of the hybrids, they were evaluated against the murine macrophage cell line J774.A1. Based on the results, three hybrids showed the highest antileishmanial activity. However, they revealed low cytotoxicity. Hybrid 6j was the most potent compound against both the forms of all leishmanial types, with IC50 = 13.5 and 11.9 µg/mL for L. major, 37.5 and 25 µg/mL for L. tropica, 17.5 and 20 µg/mL for L. infantum (MCAN/IR//96/LON49) and 35.5 and 30 µg/mL for L. infantum (MCAN/ES/98/LIM-877), respectively. Finally, molecular docking and molecular dynamics simulations were also performed to identify possible mechanism antileishmanial activity.Communicated by Ramaswamy H. Sarma.

Synthetic product-based approach toward potential antileishmanial drug development

Leishmaniasis is a parasitic disease and is categorized as a tropically neglected disease (NTD) with no effective vaccines available. The available chemotherapeutics against leishmaniasis are associated with an increase in the incidence of toxicity and drug resistance. Consequently, targeting metabolic pathways and enzymes of parasites which differs from the mammalian host can be exploited to treat and overcome the resistance. The classical methods of identifying the structural fragments and the moieties responsible for the biological activities from the standard compounds and their modification are options for developing more effective novel compounds. Significant progress has been made in refining the development of potent non-toxic molecules and addressing the limitations of the current treatment available. Several examples of synthetic product-based approach utilizing their core heterocyclic rings including furan, pyrrole, thiazole, imidazole, pyrazole, triazole, quinazoline, quinoline, pyrimidine, coumarin, indole, acridine, oxadiazole, purine, chalcone, carboline, phenanthrene and metal containing derivatives and their structure-activity relationships are discussed in this review. It also analyses the groups/fragments interacting with the host cell receptors and will support the medicinal chemists with novel antileishmanial agents.

Articulate Chemotherapeutic Strategies for the Development of Effective Drugs against a Fatal Disease, Visceral Leishmaniasis

Visceral Leishmaniasis (VL) control relies mainly on chemotherapy in the absence of no effective vaccines. However, available anti-VL drugs are limited in number, having toxicity issues, adverse reactions, low efficacy, and resistance observed against antileishmanial. A significant decrease in efficacy (~tenfold increase in dosage and duration) was reported against the usual treatment with Pentavalent antimonials (the most recommended antileishmanial drug discovered 90 years ago). Amphotericin B is the second line of treatment but limits wider use due to its high cost. Pentamidine is another anti-VL drug, but its therapeutic efficacy has decreased significantly in different areas. These conventional therapeutics for VL have become almost outdated due to a significant increase in therapeutic failure in terms of percentage. Due to this, the search for an effective future anti-VL drug spans several decades, and now it is in high demand in the current situation. Some conventional therapeutics are modified, but they are also not satisfactory. Therefore, this article aimed to discuss conventional and modified therapeutics while emphasizing innovative chemotherapeutic measures against VL that could speed up the slow pace of antileishmanial drugs and overcome the drug resistance problem in the future.

Mannosylated imiquimod-terbinafine co-loaded transethosomes for cutaneous leishmaniasis; assessment of its anti-leishmanial potential, in vivo safety and immune response modulation

Current treatment options for cutaneous leishmaniasis are associated with myriad limiting factors including low penetration, poor efficacy, and drug toxicities. Herein, we reported imiquimod and terbinafine co-loaded mannosylated transethosomes (IMQ-TER-MTES) with enhanced cutaneous retention, macrophage targeting, anti-leishmanial potential, and dermal immunomodulation. IMQ-TER-MTES were optimized using Design Expert® followed by their loading into chitosan gel. Moreover, the antileishmanial response against amastigotes-infected macrophages and Leishmania-infected BALB/c mice was evaluated. Finally, the safety and immunomodulation activity of IMQ-TER-MTES gel was performed using BALB/c mice. Optimized IMQ-TER-MTES showed nano-sized particles with low poly-dispersibility index (PDI) and high drug entrapment. Mannosylation has augmented macrophage targeting and the internalization capability of TES. IMQ-TER-MTES showed significantly reduced IC₅₀ value (19.56 ± 3.62 μg/ml), higher selectivity index (29.24), and synergism against Leishmania major (L. major) amastigotes. In L. major infected BALB/c mice, the cutaneous lesion healing potential of IMQ-TER-MTES was also elevated with reduced lesion size (1.52 ± 0.43 mm). Superior safety of IMQ-TER-MTES was observed in BALB/c mice along with adequate stimulation of dermal immune cells, in contrast to the ALDARA®. Moreover, incremented Nuclear factor Kappa-β (NF-κβ) and nitric oxide (NO) biosynthesis were observed with IMQ-TER-MTES.

Krebs cycle enzymes for targeted therapeutics and immunotherapy for anti-leishmanial drug development using: Pathways, potential targets, and future perspectives

Leishmaniasis is a parasitic and neglected tropical disease which majorly impacts poor and developing nations. One of the significant factors that impacts the severity of the pathological condition includes the socioeconomic background of the affected region. The rise of drug-resistant Leishmania is a serious concern for the effectiveness of the present treatment. As a result, the drug options need to be relooked immediately. Leishmania employs Krebs cycle intermediates for its needs after infection for establishing various defense mechanisms to escape the host immune responses. Nevertheless, a variety of immunological reactions are also seen during infection, which clear the parasites. One of the more promising strategies in this regard would involve combining targeted therapy and immunotherapy. The targeted treatments work by obstructing vital pathways that are required for Leishmania to grow and survive. The mechanism of action of immunotherapy is the control of the host immune response, which entails the blockage of molecular pathways essential for the growth and maintenance of the parasite. The Krebs cycle intermediates have important biochemical roles. Additionally, in macrophages and dendritic cells, they play roles as signalling molecules for controlling inflammatory responses. The review brings together the available literature about the importance of Krebs cycle metabolites as potential treatment targets for leishmaniasis.

Drug repurposing based novel anti-leishmanial drug screening using in-silico and in-vitro approaches

Visceral leishmaniasis is a neglected tropical disease and is mainly caused by L. donovani in the Indian subcontinent. The mitochondria genome replication in Leishmania spp. is having a very specific mechanism, and it is initiated by a key enzyme called mitochondrial primase. This enzyme is essential for the onset of the replication process and growth of the parasite. Therefore, we focused on the primase protein as a potential therapeutic target for combating leishmaniasis diseases. We started our studies molecular modeling and followed by docking of the FDA-approved drug library into the binding site of the primase protein. The top 30 selected compounds were subjected for molecular dynamics studies. Also, the target protein was cloned, purified, and tested experimentally (primase activity assays and inhibition assays). Some compounds were very effective against the Leishmania cell culture. All these approaches helped us to identify few possible novel anti-leishmanial drugs such as Pioglitazone and Mupirocin. These drugs are effectively involved in inhibiting the promastigote of L. donovani, and it can be utilized in the next level of clinical trials. Communicated by Ramaswamy H. Sarma.

Current leishmaniasis drug discovery

Leishmaniasis is a complex protozoan infectious disease and, associated with malnutrition, poor health services and unavailability of prophylactic control measures, neglected populations are particularly affected. Current drug regimens are outdated and associated with some drawbacks, such as cytotoxicity and resistance, and the development of novel, efficacious and less toxic drug regimens is urgently required. In addition, leishmanial pathogenesis is not well established or understood, and a prophylactic vaccine is an unfulfilled goal. Human kinetoplastid protozoan infections, including leishmaniasis, have been neglected for many years, and in an attempt to overcome this situation, some new drug targets were recently identified, enabling the development of new drugs and vaccines. Compounds from new drug classes have also shown excellent antileishmanial activities, some of the most promising ones included in clinical trials, and could be a hope to control the disease burden of this endemic disease in the near future. In this review, we discuss the limitations of current control methods, explore the wide range of compounds that are being screened and identified as antileishmanial drug prototypes, summarize the advances in identifying new drug targets aiming at innovative treatments and explore the state-of-art vaccine development field, including immunomodulation strategies.

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.

Evaluation of the inhibitory potential of Valproic acid against histone deacetylase of Leishmania donovani and computational studies of Valproic acid derivatives

Valproic acid (VA) is a proven inhibitor of human histone deacetylases (HDACs). The homogenous HDAC has been associated with all major human parasitic pathogens and hence, it has been considered an attractive drug target for anti-leishmanial therapy. To assist in drug design endeavors for HDACs, an in-vitro study has been presented to investigate the VA inhibition on Leishmania donovani HDAC (LdHDAC). The regression analysis of VA by 24 hrs viability assay confirmed its activity against LdHDAC. Moreover, the toxicity of VA is also well documented. Thus, the in-silico experiments were also conducted to screen the non-toxic VA derivatives as anti-leishmanial drug candidates having potential as inhibitors of LdHDAC. For in-silico study, the 3D structure of target LdHDAC was developed by homology modeling. Based on their in-silico activity, we shortlisted 13 VA derivatives having maximum affinity for LdHDAC and identified four potential derivatives that can specifically bind to this protein. After that, these ligands were subjected to molecular dynamics simulation. These derivatives may be effective against L. donovani promastigotes since they followed Lipinski's RO5 and were non-toxic. Thus, screened derivatives can be considered as lead ligands for targeting LdHDAC and may be used as possible drug candidates to treat leishmaniasis and overcome the limitation of anti-leishmanial drugs. This is the first report of antileishmanial potential of VA and its derivatives targeting LdHDAC. Hence, the current investigation presents a search for novel target specific drugs to aid the anti-leishmanial drug development. Communicated by Ramaswamy H. Sarma.

The Current Directions of Searching for Antiparasitic Drugs

Parasitic diseases are still a huge problem for mankind. They are becoming the main cause of chronic diseases in the world. Migration of the population, pollution of the natural environment, and climate changes cause the rapid spread of diseases. Additionally, a growing resistance of parasites to drugs is observed. Many research groups are looking for effective antiparasitic drugs with low side effects. In this work, we present the current trends in the search for antiparasitic drugs. We report known drugs used in other disease entities with proven antiparasitic activity and research on new chemical structures that may be potential drugs in parasitic diseases. The described investigations of antiparasitic compounds can be helpful for further drug development.

Design, Synthesis of Biaryl Piperidine Derivatives and Their Evaluation as Potential Antileishmanial Agents against Leishmania donovani Strain Ag83

We have developed a new series of simple biaryl piperidine derivatives (11-19) based on biaryl naphthylisoquinoline alkaloid Ealamine-A. The target compounds were synthesized, analyzed by spectral data, and evaluated for antileishmanial activity against Leishmania donovani strain Ag83 by MTT assay. The compounds have shown the best to moderate antileishmanial activity. The 5'-fluoro-2'-methoxyphenyl derivative 14 and 3',5'-difluorophenyl derivative 16 have inhibited the promastigotes by 86 % and 85 % after 24 h and 92 % and 91 % after 48 h incubation, respectively, at 400 μM concentration. The % inhibition was lower with the lowering of the concentration and increased with the incubation time. Compounds 12, 15, and 18 have solubility issues and proved to be less active than the rest of the compounds. Molecular docking studies were performed on selective active compounds and the results indicate that these compounds may act by binding to the Leishmanolysin and the docking scores are in good correlation with the antileishmanial activity. These results provide an initial insight into the design of new therapeutics for neglected tropical diseases.

DDX3 DEAD-box RNA helicase (Hel67) gene disruption impairs infectivity of Leishmania donovani and induces protective immunity against visceral leishmaniasis

Visceral leishmaniasis (VL) is a vector-borne disease caused by the digenetic protozoan parasite Leishmania donovani complex. So far there is no effective vaccine available against VL. The DDX3 DEAD-box RNA Helicase (Hel67) is 67 kDa protein which is quite essential for RNA metabolism, amastigote differentiation, and infectivity in L. major and L. infantum. To investigate the role of Hel67 in the L. donovani, we created L. donovani deficient in the Hel67. Helicase67 null mutants (LdHel67^-/-) were not able to differentiate as axenic amastigotes and were unable to infect the hamster. So, we have analyzed the prophylactic efficacy of the LdHel67^-/- null mutant in hamsters. The LdHel67^-/- null mutant based candidate vaccine exhibited immunogenic response and a higher degree of protection against L. donovani in comparison to the infected control group. Further, the candidate vaccine displayed antigen-specific delayed-type hypersensitivity (DTH) as well as strong antibody response and NO production which strongly correlates to long term protection of candidate vaccine against the infection. This study confirms the potential of LdHel67^-/- null mutant as a safe and protective live attenuated vaccine candidate against visceral leishmaniasis.

Nanoparticles Formulations of Artemisinin and Derivatives as Potential Therapeutics for the Treatment of Cancer, Leishmaniasis and Malaria

Cancer, malaria, and leishmaniasis remain the deadly diseases around the world although several strategies of treatment have been developed. However, most of the drugs used to treat the aforementioned diseases suffer from several pharmacological limitations such as poor pharmacokinetics, toxicity, drug resistance, poor bioavailability and water solubility. Artemisinin and its derivatives are antimalarial drugs. However, they also exhibit anticancer and antileishmanial activity. They have been evaluated as potential anticancer and antileishmanial drugs but their use is also limited by their poor water solubility and poor bioavailability. To overcome the aforementioned limitations associated with artemisinin and its derivatives used for the treatment of these diseases, they have been incorporated into nanoparticles. Several researchers incorporated this class of drugs into nanoparticles resulting in enhanced therapeutic outcomes. Their potential efficacy for the treatment of parasitic infections such as malaria and leishmaniasis and chronic diseases such as cancer has been reported. This review article will be focused on the nanoparticles formulations of artemisinin and derivatives for the treatment of cancer, malaria, and leishmaniasis and the biological outcomes (in vitro and in vivo).

DNA-based microarray studies in visceral leishmaniasis: identification of biomarkers for diagnostic, prognostic and drug target for treatment

Visceral leishmaniasis (VL) is one of the major infectious diseases affecting the poorest regions of the world. Current therapy is not very much satisfactory. The alarming rise of drug resistance and the unavailability of an effective vaccine against VL urges research towards identifying new targets or biomarkers for its effective treatment. New technology developments offer some fresh hope in its diagnosis, treatment, and control. DNA microarray approach is now broadly used in parasitology research to facilitate the thoughtful of mechanisms of disease and identification of drug targets and biomarkers for diagnostic and therapeutic development. An electronic search on "VL" and "Microarray" was conducted in Medline and Scopus and papers published in the English mentioning use of DNA microarray on VL were selected and read to write this paper review. Functional analysis and interpretation of microarray results remain very challenging due to the inherent nature of experimental workflows, access, cost, and complexity of data obtained. We have explained and emphasized the use of curate knowledge of microarray in the case of VL for the identification of therapeutic target and biomarker and their selection/implementation in clinical use.

Identification of trans-2-cis-8-Matricaria-ester from the Essential Oil of Erigeron multiradiatus and Evaluation of Its Antileishmanial Potential by in Vitro and in Silico Approaches

The essential oil (EO) composition of the aerial parts of Erigeron multiradiatus (Lindl.ex DC.) Benth growing wild in the central Himalayan region of Uttarakhand, India, was analyzed by capillary gas chromatography with a flame ionization detector and gas chromatography-mass spectrometry. A sum of 12 constituents was identified, representing 97.81% of the oil composition. The oil was composed mainly of oxygenated monoterpenes (88.95%), sesquiterpene hydrocarbons (5.61%), oxygenated sesquiterpenes (3.05%), and monoterpene hydrocarbons (0.20%). Major constituents identified were trans-2-cis-8-matricaria-ester (77.79%), cis-lachnophyllum ester (11.04%), zingiberene (4.43%), and spathulenol (1.59%). Further, the leishmanicidal effect of EO and the purified compound trans-2-cis-8-matricaria-ester has been investigated against Leishmania donovani promastigotes and intracellular amastigotes. EO and trans-2-cis-8-matricaria-ester were safer for the hamster peritoneal macrophage and lethal to promastigotes and intracellular amastigotes at different concentrations. Further, using an in silico approach, these four compounds were tested against 10 major proteins of L. donovani associated with its virulence. Out of them, only trans-2-cis-8-matricaria-ester was found to be effective against the four target proteins, namely, l-asparaginase-1-like protein, metacaspase 2, metacaspase 1, and DNA topoisomerase II of L. donovani. The results indicate that EO contains trans-2-cis-8-matricaria-ester as a major component and showed antileishmanial activity which may facilitate discovery of new lead molecules for developing herbal medicines against visceral leishmaniasis.

Metacaspases: Potential Drug Target Against Protozoan Parasites

Among the numerous strategies/targets for controlling infectious diseases, parasites-derived proteases receive prime attention due to their essential contribution to parasite growth and development. Parasites produce a broad array of proteases, which are required for parasite entry/invasion, modification/degradation of host proteins for their nourishment, and activation of inflammation that ensures their survival to maintain infection. Presently, extensive research is focused on unique proteases termed as "metacaspases" (MCAs) in relation to their versatile functions in plants and non-metazoans. Such unique MCAs proteases could be considered as a potential drug target against parasites due to their absence in the human host. MCAs are cysteine proteases, having Cys-His catalytic dyad present in fungi, protozoa, and plants. Studies so far indicated that MCAs are broadly associated with apoptosis-like cell death, growth, and stress regulation in different protozoa. The present review comprises the important research outcomes from our group and published literature, showing the variable properties and function of MCAs for therapeutic purpose against infectious diseases.