Antiprotozoal activities of benzimidazoles and correlations with beta-tubulin sequence

Phenolic chalcones as agents against Trichomonas vaginalis

Trichomonas vaginalis, a flagellated and anaerobic protozoan, is a causative agent of trichomoniasis. This disease is among the world's most common non-viral sexually transmitted infection. A single class drug, nitroimidazoles, is currently available for the trichomoniasis treatment. However, resistant isolates have been identified from unsuccessfully treated patients. Thus, there is a great challenge for a discovery of innovative anti-T. vaginalis agents. As part of our ongoing search for antiprotozoal chalcones, we designed and synthesized a series of 21 phenolic chalcones, which were evaluated against T. vaginalis trophozoites. Structure-activity relationship indicated hydroxyl group plays a role key in antiprotozoal activity. 4'-Hydroxychalcone (4HC) was the most active compound (IC50 = 27.5 µM) and selected for detailed bioassays. In vitro and in vivo evaluations demonstrated 4HC was not toxic against human erythrocytes and Galleria mellonella larvae. Trophozoites of T. vaginalis were treated with 4HC and did not present significant reactive oxygen species (ROS) accumulation. However, compound 4HC was able to increase ROS accumulation in neutrophils coincubated with T. vaginalis. qRT-PCR Experiments indicated that 4HC did not affect the expression of pyruvate:ferredoxin oxidoreductase (PFOR) and β-tubulin genes. In silico simulations, using purine nucleoside phosphorylase of T. vaginalis (TvPNP), corroborated 4HC as a promising ligand. Compound 4HC was able to establish interactions with residues D21, G20, M180, R28, R87 and T90 through hydrophobic interactions, π-donor hydrogen bond and hydrogen bonds. Altogether, these results open new avenues for phenolic chalcones to combat trichomoniasis, a parasitic neglected infection.

Screening of the Pandemic Response Box identifies anti-microsporidia compounds

Microsporidia are fungal obligate intracellular pathogens, which infect most animals and cause microsporidiosis. Despite the serious threat that microsporidia pose to humans and agricultural animals, few drugs are available for the treatment and control of microsporidia. To identify novel inhibitors, we took advantage of the model organism Caenorhabditis elegans infected with its natural microsporidian Nematocida parisii. We used this system to screen the Pandemic Response Box, a collection of 400 diverse compounds with known antimicrobial activity. After testing these compounds in a 96-well format at high (100 μM) and low (40 μM) concentrations, we identified four inhibitors that restored the ability of C. elegans to produce progeny in the presence of N. parisii. All four compounds reduced the pathogen load of both N. parisii and Pancytospora epiphaga, a C. elegans-infecting microsporidia related to human-infecting species. One of these compounds, a known inhibitor of a viral protease, MMV1006203, inhibited invasion and prevented the firing of spores. A bis-indole derivative, MMV1593539, decreased spore viability. An albendazole analog, MMV1782387, inhibited proliferation of N. parisii. We tested albendazole as well as 5 other analogs and observed that MMV1782387 was amongst the strongest inhibitors of N. parisii and displayed the least host toxicity. Our study further demonstrates the effectiveness of the C. elegans-N. parisii system for discovering microsporidia inhibitors and the compounds we identified provide potential scaffolds for anti-microsporidia drug development.

Ultrastructural Alterations of the Human Pathogen Giardia intestinalis after Drug Treatment

This review presents the main cell characteristics altered after in vitro incubation of the parasite with commercial drugs used to treat the disease caused by Giardia intestinalis. This important intestinal parasite primarily causes diarrhea in children. Metronidazole and albendazole are the primary compounds used in therapy against Giardia intestinalis. However, they provoke significant side effects, and some strains have developed resistance to metronidazole. Benzimidazole carbamates, such as albendazole and mebendazole, have shown the best activity against Giardia. Despite their in vitro efficacy, clinical treatment with benzimidazoles has yielded conflicting results, demonstrating lower cure rates. Recently, nitazoxanide has been suggested as an alternative to these drugs. Therefore, to enhance the quality of chemotherapy against this parasite, it is important to invest in developing other compounds that can interfere with key steps of metabolic pathways or cell structures and organelles. For example, Giardia exhibits a unique cell structure called the ventral disc, which is crucial for host adhesion and pathogenicity. Thus, drugs that can disrupt the adhesion process hold promise for future therapy against Giardia. Additionally, this review discusses new drugs and strategies that can be employed, as well as suggestions for developing novel drugs to control the infection caused by this parasite.

Structural Changes, Biological Consequences, and Repurposing of Colchicine Site Ligands

Microtubule-targeting agents (MTAs) bind to one of several distinct sites in the tubulin dimer, the subunit of microtubules. The binding affinities of MTAs may vary by several orders of magnitude, even for MTAs that specifically bind to a particular site. The first drug binding site discovered in tubulin was the colchicine binding site (CBS), which has been known since the discovery of the tubulin protein. Although highly conserved throughout eukaryotic evolution, tubulins show diversity in their sequences between tubulin orthologs (inter-species sequence differences) and paralogs (intraspecies differences, such as tubulin isotypes). The CBS is promiscuous and binds to a broad range of structurally distinct molecules that can vary in size, shape, and affinity. This site remains a popular target for the development of new drugs to treat human diseases (including cancer) and parasitic infections in plants and animals. Despite the rich knowledge about the diversity of tubulin sequences and the structurally distinct molecules that bind to the CBS, a pattern has yet to be found to predict the affinity of new molecules that bind to the CBS. In this commentary, we briefly discuss the literature evidencing the coexistence of the varying binding affinities for drugs that bind to the CBS of tubulins from different species and within species. We also comment on the structural data that aim to explain the experimental differences observed in colchicine binding to the CBS of β-tubulin class VI (TUBB1) compared to other isotypes.

Homology Modeling, Molecular Docking, Molecular Dynamic Simulation, and Drug-Likeness of the Modified Alpha-Mangostin against the β-Tubulin Protein of Acanthamoeba Keratitis

Acanthamoeba species are capable of causing amoebic keratitis (AK). As a monotherapy, alpha-mangostin is effective for the treatment of AK; however, its bioavailability is quite poor. Moreover, the efficacy of therapy is contingent on the parasite and virulent strains. To improve readiness against AK, it is necessary to find other derivatives with accurate target identification. Beta-tubulin (BT) has been used as a target for anti-Acanthamoeba (A. keratitis). In this work, therefore, a model of the BT protein of A. keratitis was constructed by homology modeling utilizing the amino acid sequence from NCBI (GenBank: JQ417907.1). Ramachandran Plot was responsible for validating the protein PDB. The verified BT PDB was used for docking with the specified ligand. Based on an improved docking score compared to alpha-mangostin (AM), two modified compounds were identified: 1,6-dihydroxy-7-methoxy-2,8-bis(3-methylbut-2-en-1-yl)-9H-xanthen-9-one (C1) and 1,6-dihydroxy-2,8-bis(3-methylbut-2-en-1-yl)-9H-xanthen-9-one (C2). In addition, molecular dynamics simulations were conducted to analyze the interaction characteristics of the two bound BT–new compound complexes. During simulations, the TRP9, ARG50, VAL52, and GLN122 residues of BT-C1 that align to the identical residues in BT-AM generate consistent hydrogen bond interactions with 0–3 and 0–2. However, the BT-C2 complex has a different binding site, TYR 258, ILE 281, and SER 302, and can form more hydrogen bonds in the range 0–4. Therefore, this study reveals that C1 and C2 inhibit BT as an additive or synergistic effect; however, further in vitro and in vivo studies are needed.

An Update on the Biologic Effects of Fenbendazole

Fenbendazole remains the drug of choice to treat pinworm infection in laboratory rodents. When fenbendazole was last reviewed (15 y ago), the literature supported the drug's lack of toxic effects at therapeutic levels, yet various demonstrated physiologic effects have the potential to alter research outcomes. Although more recent reports continue to reflect an overall discordancy of results, several studies support the premise that fenbendazole affects the bone marrow and the immune system. No effects on reproduction were reported in an extensive study that assessed common treatment protocols in mice, and food intake was unchanged in rats. Behavioral studies are sparse, with only a single report of a subtle change in a rotarod performance in mice. Notably, unexpected results in tumor models during facility treatment with fenbendazole have prompted preclinical and clinical studies of the potential roles of benzimidazoles in cancer.

Designing and development of phthalimides as potent anti-tubulin hybrid molecules against malaria

Constant emergence of drug-resistant Plasmodium falciparum warrants urgent need for effective and inexpensive drugs. Herein, phthalimide (Pht) analogs possessing the bioactive scaffolds, benzimidazole and 1,2,3-triazole, were evaluated for in vitro and in vivo anti-plasmodial activity without any apparent hemolysis, or cytotoxicity. Analogs 4(a-e) inhibited the growth of 3D7 and RKL-9 strains at submicromolar concentrations. Defects were observed during parasite egress from or invasion of the red blood cells. Mitochondrial membrane depolarization was measured as one of the causes of cell death. Phts 4(a-e) in combination with artemisinin exhibited two-to three-fold increased efficacy. Biophysical and biochemical analysis suggest that Pht analogs mediate plasmodial growth inhibition by interacting with tubulin protein of the parasite. Lastly, Phts 4(a-e) significantly decreased parasitemia and extended host survival in murine model Plasmodium berghei ANKA infection. Combined, the data indicate that Pht analogs should be further explored, which could offer novel value to the antimalarial drug development pipeline.

Design and synthesis of benzimidazole derivatives as antimycobacterial agents

A series of 2,5-disubstituted benzimidazole derivatives was synthesized with the aim to identify compounds with potent anti-TB activity. All the compounds were screened in vitro against cultured Mycobacterium tuberculosis H₃₇ Rv strain and found to be exhibiting MIC₉₉ values in the range of 0.195-100 µM. Out of 43 synthesized compounds, two compounds 11h and 13e showed better anti-TB activity than the reference drug isoniazid.

Homology modelling, molecular dynamics simulation and docking evaluation of β-tubulin of Schistosoma mansoni

Schistosomiasis is one of the neglected diseases causing considerable morbidity and mortality throughout the world. Microtubules with its main component, tubulin play a vital role in helminthes including schistosomes. Benzimidazoles represent potential drug candidates by binding β-tubulin. The study aimed to generate a homology model for the β-tubulin of S. mansoni using the crystal structure of O visaries (Sheep) β-tubulin (PDB ID: 3N2G D) as a template, then different β-tubulin models were generated and two previously reported benzimidazole derivatives (NBTP-F and NBTP-OH) were docked to the generated models, the binding results indicated that both S. mansoni, S. haematobium were susceptible to the two NBTP derivatives. Additionally, three mutated versions of S. mansoni β-tubulin wild-type were generated and the mutation (F185Y) seems to slightly enhance the ligand binding. Dynamics simulation experiments showed S. haematobium β-tubulin is highly susceptible to the tested compounds; similar to S. mansoni, moreover, mutated models of S. mansoni β-tubulin altered its NBTPs susceptibility. Moreover, additional seven new benzimidazole derivatives were synthesized and tested by molecular docking on the generated model binding site of S. mansoni β-tubulin and were found to have good interaction inside the pocket.

In vitro selection of Giardia duodenalis for Albendazole resistance identifies a β-tubulin mutation at amino acid E198K

Benzimidazole-2-carbamate (BZ) compounds, including Albendazole (Alb), are one of just two drug classes approved to treat the gastrointestinal protist Giardia duodenalis. Benzimidazoles bind to the tubulin dimer interface overlapping the colchicine binding site (CBS) of β-tubulin, thereby inhibiting microtubule polymerisation and disrupting microtubule networks. These BZ compounds are widely used as anthelmintic, anti-fungal and anti-giardial drugs. However, in helminths and fungi, BZ-resistance is widespread and caused by specific point mutations primarily occurring at F167, E198 and F200 in β-tubulin isoform 1. BZ-resistance in Giardia is reported clinically and readily generated in vitro, with significant implications for Giardia control. In Giardia, BZ mode of action (MOA) and resistance mechanisms are presumed but not proven, and no mutations in β-tubulin have been reported in association with Alb resistance (AlbR). Herein, we undertook detailed in vitro drug-susceptibility screens of 13 BZ compounds and 7 Alb structural analogues in isogenic G. duodenalis isolates selected for AlbR and podophyllotoxin, another β-tubulin inhibitor, as well as explored cross-resistance to structurally unrelated, metronidazole (Mtz). AlbR lines exhibited co-resistance to many structural variants in the BZ-pharmacophore, and cross-resistance to podophyllotoxin. AlbR lines were not cross-resistant to Mtz, but MtzR lines had enhanced survival in Alb. Lastly, Alb analogues with longer thioether substituents had decreased potency against our AlbR lines. In silico modelling indicated the Alb-β-tubulin interaction in Giardia partially overlaps the CBS and corresponds to residues associated with BZ-resistance in helminths and fungi (F167, E198, F200). Sequencing of Giardia β-tubulin identified a single nucleotide polymorphism resulting in a mutation from glutamic acid to lysine at amino acid 198 (E198K). To our knowledge, this is the first β-tubulin mutation reported for protistan BZ-resistance. This study provides insight into BZ mode of action and resistance in Giardia, and presents a potential avenue for a genetic test for clinically resistance isolates.

Albendazole and Mebendazole as Anti-Parasitic and Anti-Cancer Agents: an Update

The use of albendazole and mebendazole, i.e., benzimidazole broad-spectrum anthelmintics, in treatment of parasitic infections, as well as cancers, is briefly reviewed. These drugs are known to block the microtubule systems of parasites and mammalian cells leading to inhibition of glucose uptake and transport and finally cell death. Eventually they exhibit ovicidal, larvicidal, and vermicidal effects on parasites, and tumoricidal effects on hosts. Albendazole and mebendazole are most frequently prescribed for treatment of intestinal nematode infections (ascariasis, hookworm infections, trichuriasis, strongyloidiasis, and enterobiasis) and can also be used for intestinal tapeworm infections (taeniases and hymenolepiasis). However, these drugs also exhibit considerable therapeutic effects against tissue nematode/cestode infections (visceral, ocular, neural, and cutaneous larva migrans, anisakiasis, trichinosis, hepatic and intestinal capillariasis, angiostrongyliasis, gnathostomiasis, gongylonemiasis, thelaziasis, dracunculiasis, cerebral and subcutaneous cysticercosis, and echinococcosis). Albendazole is also used for treatment of filarial infections (lymphatic filariasis, onchocerciasis, loiasis, mansonellosis, and dirofilariasis) alone or in combination with other drugs, such as ivermectin or diethylcarbamazine. Albendazole was tried even for treatment of trematode (fascioliasis, clonorchiasis, opisthorchiasis, and intestinal fluke infections) and protozoan infections (giardiasis, vaginal trichomoniasis, cryptosporidiosis, and microsporidiosis). These drugs are generally safe with few side effects; however, when they are used for prolonged time (>14-28 days) or even only 1 time, liver toxicity and other side reactions may occur. In hookworms, Trichuris trichiura, possibly Ascaris lumbricoides, Wuchereria bancrofti, and Giardia sp., there are emerging issues of drug resistance. It is of particular note that albendazole and mebendazole have been repositioned as promising anti-cancer drugs. These drugs have been shown to be active in vitro and in vivo (animals) against liver, lung, ovary, prostate, colorectal, breast, head and neck cancers, and melanoma. Two clinical reports for albendazole and 2 case reports for mebendazole have revealed promising effects of these drugs in human patients having variable types of cancers. However, because of the toxicity of albendazole, for example, neutropenia due to myelosuppression, if high doses are used for a prolonged time, mebendazole is currently more popularly used than albendazole in anti-cancer clinical trials.

Molecular docking and dynamic simulations of benzimidazoles with beta-tubulins

It is of interest to document the molecular docking and dynamic simulations of benzimidazoles with beta-tubulins in the context of anthelmintic activity. We document the compound BI-02 (2-(3,4-dimethyl phenyl)-1H-1,3-benzimidazole (BI-02) with optimal bindig features compared to the standard molecule albendazole (7.0 Kcal/mol) with binding energy -8.50 Kcal/mol and PIC50 value 583.62 nM.

Evaluation of Therapeutic Approaches for the Treatment of Spironucleus muris in Mice

Spironucleus muris is an intestinal protozoal pathogen that can infect various species of rodents. The infection can have a wide range of clinical presentations, from no signs of disease to death. In addition, this pathogen can adversely affect research results, especially immunologic and gastrointestinal studies. For these reasons, institutions may exclude Spironucleus muris. However, despite rigorous efforts to keep this pathogen out, it can be common in rodent colonies. The current recommended approach to eradicating this pathogen is by testing and culling positive animals. A similar organism, Giardia muris, has been effectively eliminated by using chemotherapeutics. Therefore, the objective of this study was to determine whether S. muris is also susceptible to chemotherapeutics. Naturally infected mice were randomized to treatment groups after confirmation of positive infection via PCR. Mice received either metronidazole, fenbendazole, a combination of metronidazole-fenbendazole, or acidified water (control) treatments for a period of 4 wk. Each week fecal testing of S. muris was performed via PCR to evaluate the effectiveness of the treatments. At the end of the 4 wk period, mice were euthanized via CO₂ inhalation and segments of the proximal gastrointestinal tract were submitted for histopathologic analysis. Treatment with metronidazole or fenbendazole alone or in combination, failed to clear S. muris infected mice. After 4 wk of treatment, none of the mice given fenbendazole via sucralose medicated gel were positive by either PCR or histopathology; however, this finding is most likely due to intermittent shedding rather than chemotherapeutic success. Therefore, the recommendation remains to test-and-cull or rederive mice as necessary to eliminate S. muris from laboratory animal facilities.

New Approaches for the Synthesis of Heterocyclic Compounds Corporating Benzo[d]imidazole as Anticancer Agents, Tyrosine, Pim-1 Kinases Inhibitions and their PAINS Evaluations

BACKGROUND

Benzo[d]imidazoles are highly biologically active, in addition, they are considered as a class of heterocyclic compounds with many pharmaceutical applications.

OBJECTIVE

We are aiming in this work to synthesize target molecules that possess not only anti-tumor activities but also kinase inhibitors. The target molecules were obtained starting from the benzo[d]imidazole derivatives followed by their heterocyclization reactions to produce anticancer target molecules.

METHODS

The 1-(1H-benzo[d]imidazol-2-yl)propan-2-one (3) and the ethyl 2-(1H-benzo[d]imidazol-2- yl)acetate (16) were used as the key starting material which reacted with salicylaldehyde to give the corresponding benzo[4,5]imidazo[1,2-a]quinoline derivatives. On the other hand, both of them were reacted with different reagents to give thiophene, pyran and benzo[4,5]imidazo[1,2-c]pyrimidine derivatives. The synthesized compounds were evaluated against the six cancer cell lines A549, HT-29, MKN-45, U87MG, SMMC-7721, and H460 together with inhibitions toward tyrosine kinases, c-Met kinase and prostate cancer cell line PC-3 using the standard MTT assay in vitro, with foretinib as the positive control.

RESULTS

Most of the synthesized compounds exhibited high inhibitions toward the tested cancer cell lines. In addition, tyrosine and Pim-1 kinases inhibitions were performed for the most active compounds where the variation of substituent through the aryl ring and heterocyclic ring afforded compounds with high activities. Our analysis showed that there is a strong correlation between the structure of the compound and the substituents of target molecules.

CONCLUSION

Our present research proved that the synthesized heterocyclic compounds with varieties of substituents have a strong impact on the activity of compounds. The evaluations through different cell lines and tyrosine kinases indicated that the compounds were the excellent candidates as anticancer agents. This could encourage doing further research within this field for the building of compounds with high inhibitions.

Anti-Giardia Drug Discovery: Current Status and Gut Feelings

Giardia parasites are ubiquitous protozoans of global importance that impact a wide range of animals including humans. They are the most common enteric pathogen of cats and dogs in developed countries and infect ∼1 billion people worldwide. While Giardia infections can be asymptomatic, they often result in severe and chronic diseases. There is also mounting evidence that they are linked to postinfection disorders. Despite growing evidence of the widespread morbidity associated with Giardia infections, current treatment options are limited to compound classes with broad antimicrobial activity. Frontline anti-Giardia drugs are also associated with increasing drug resistance and treatment failures. To improve the health and well-being of millions, new selective anti-Giardia drugs are needed alongside improved health education initiatives. Here we discuss current treatment options together with recent advances and gaps in drug discovery. We also propose criteria to guide the discovery of new anti-Giardia compounds.

Vaginitis: Review on Drug Resistance

Female genital tract infections have a high incidence among different age groups and represent an important impact on public health. Among them, vaginitis refers to inflammation of the vulva and/or vagina due to the presence of pathogens that cause trichomoniasis, bacterial vaginosis, and vulvovaginal candidiasis. Several discomforts are associated with these infections, as well as pregnancy complications and the facilitation of HIV transmission and acquisition. The increasing resistance of microorganisms to drugs used in therapy is remarkable, since women report the recurrence of these infections and associated comorbidities. Different resistant mechanisms already described for the drugs used in the therapy against Trichomonas vaginalis, Candida spp., and Gardnerella vaginalis, as well as aspects related to pathogenesis and treatment, are discussed in this review. This study aims to contribute to drug design, avoiding therapy ineffectiveness due to drug resistance. Effective alternative therapies to treat vaginitis will reduce the recurrence of infections and, consequently, the high costs generated in the health system, improving women's well-being.

Encephalitozoon cuniculi Genotype III Evinces a Resistance to Albendazole Treatment in both Immunodeficient and Immunocompetent Mice

Of four genotypes of Encephalitozoon cuniculi, E. cuniculi genotype II is considered to represent a parasite that occurs in many host species in a latent asymptomatic form, whereas E. cuniculi genotype III seems to be more aggressive, and infections caused by this strain can lead to the death of even immunocompetent hosts. Although albendazole has been considered suitable for treatment of Encephalitozoon species, its failure in control of E. cuniculi genotype III infection has been reported. This study determined the effect of a 100× recommended daily dose of albendazole on an Encephalitozoon cuniculi genotype III course of infection in immunocompetent and immunodeficient mice and compared the results with those from experiments performed with a lower dose of albendazole and E. cuniculi genotype II. The administration of the regular dose of abendazole during the acute phase of infection reduced the number of affected organs in all strains of mice and absolute counts of spores in screened organs. However, the effect on genotype III was minor. Surprisingly, no substantial effect was recorded after the use of a 100× dose of albendazole, with larger reductions seen only in the number of affected organs and absolute counts of spores in all strains of mice, implying variations in albendazole resistance between these Encephalitozoon cuniculi genotypes. These results imply that differences in the course of infection and the response to treatment depend not only on the immunological status of the host but also on the genotype causing the infection. Understanding how microsporidia survive in hosts despite targeted antimicrosporidial treatment could significantly contribute to research related to human health.

An image-based Pathogen Box screen identifies new compounds with anti-Giardia activity and highlights the importance of assay choice in phenotypic drug discovery

Giardia duodenalis, the most prevalent human intestinal parasite causes the disease, giardiasis. On an annual basis G. duodenalis infects ~1 billion people, of which ~280 million develop symptomatic disease. Giardiasis can be severe and chronic, causing malnutrition, stunted growth and poor cognitive development in children. Current treatment options rely on drugs with declining efficacy and side-effects. To improve the health and well-being of millions of people world-wide, new anti-Giardia drugs with different modes of action to currently used drugs are required. The Medicines for Malaria Venture's Pathogen Box, a collection of bio-active compounds specifically chosen to stimulate infectious disease drug discovery, represents an opportunity for the discovery of new anti-Giardia agents. While the anti-Giardia activity of Pathogen Box compounds has been reported, this work failed to identify known anti-Giardia controls within the compound set. It also reported the activity of compounds previously screened and shown to be inactive by others, suggesting data may be inaccurate. Given these concerns the anti-Giardia activity of Pathogen Box compounds was re-assessed in the current study. Data from this work identified thirteen compounds with anti-Giardia IC₅₀ values ≤2 μM. Five of these compounds were reference compounds (marketed drugs with known anti-microbial activity), or analogues of compounds with previously described anti-Giardia activity. However, eight, including MMV676358 and MMV028694, which demonstrated potent sub-μM IC₅₀s against assemblage A, B and metronidazole resistant parasites (0.3 μM and 0.9 μM respectively), may represent new leads for future drug development. Interestingly, only four of these compounds were identified in the previously reported Pathogen Box screen highlighting the importance of assay selection and design when assessing compounds for activity against infectious agents.

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13 compounds with anti-Giardia IC₅₀ values < 2 μM were identified.

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8 compounds represent new leads for drug development.

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MMV676358 and MMV028694 demonstrated the most promising acting.

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Data highlight the importance of assay selection and design in drug discovery.

Zirconium based porous coordination polymer (PCP) bearing organocatalytic ligand: A promising dual catalytic center for ultrasonic heterocycle synthesis

Herein, the efficient role of ultrasonic irradiation both in synthesis of Zr based porous coordination polymer (Zr-PCP) nanoparticles and boosting its catalytic activity, towards the benzimidazoles synthesis is represented. We use an amine based ligand (amino-terephthalate) for PCP and we exhibit that it can have a synergistic catalytic activity. In this work, a unique nano-engineering of cooperative and synergistic catalytic activity of zirconium, as a Lewis acid, and aminophenylene, as an organocatalyst, in the synthesis of heterocycles is presented for the synthesis of benzimidazole from cascade reaction of phenylene diamine with aldehyde at ambient temperature. Zr and amine groups of the Zr-PCP are active catalytic sites which in combination with the ultrasonic irradiation leads to a high selectivity and rapid catalytic production of benzylimidazoles. N₂ adsorption-desorption along with BJH analyses confirm the microporosity of the catalyst and recyclability shows that the catalyst is green and sustainable heterogeneous microporous catalyst.

Benzo[d]imidazol-5-yl)-5-(substituted)-1,3,4-Oxadiazoles: Synthesis, Anticancer, Antimicrobial and In Silico Studies

Background:

Cancer is a fatal disease for mankind; continuous research is still going on for the invention of potent anticancer drugs. In this view, 1, 3, 4-Oxadiazoles are privileged molecules which attracted medicinal chemists towards their anticancer properties.

Methods:

A new series of benzo[d]imidazol-5-yl)-5-(substituted)-1,3,4-oxadiazole derivatives was synthesized in an efficient ‘one-pot’ nitro reductive cyclization using sodium dithionite as a cyclizing agent by a conventional method with good yield. All the structures of the synthesized molecules were characterized by IR, 1H NMR, HRMS and Mass spectral analysis. Anticancer activity screening against A375 melanoma cancer cell line and MDA-MB-231 breast cancer cell line along with antimicrobial activity were carried out using agar well diffusion method.

Results:

Compounds 8a and 8j of the series emerged as potent anticancer agents against A375 melanoma cancer cell line with IC50 47.06 µM and 36.76 µM, respectively. In silico studies also revealed that compounds 8a and 8j showed highest interaction with 2OH4 protein of VEGFR-2 tyrosine kinase. Substantial antibacterial and antifungal activities against the tested microorganism were observed for compounds 8j and 8g.

Conclusion:

Potent anticancer property has been observed with 1,3,4-Oxadiazole linked tetrafluro substituted benzene ring 8j indicating that future research on these type of molecules can be continued to improve the anticancer activity.

Lead optimization of selective tubulin inhibitors as anti-trypanosomal agents

Previously synthesized tubulin inhibitors showed promising in vitro selectivity and activity against Human African Trypanosomiasis. Current aim is to improve the ligand efficiency and reduce overall hydrophobicity of the compounds, by lead optimization. Via combinatorial chemistry, 60 new analogs were synthesized. For biological assay Trypanosoma brucei brucei Lister 427 cell line were used as the parasite model and for the host model human embryonic kidney cell line HEK-293 and mouse macrophage cell line RAW 264.7 were used to test efficacy. Of the newly synthesized compounds 5, 39, 40, and 57 exhibited IC₅₀s below 5 µM inhibiting the growth of trypanosome cells and not harming the mammalian cells at equipotent concentration. Comparably, the newly synthesized compounds have a reduced amount of aromatic moieties resulting in a decrease in molecular weight. Due to importance of tubulin polymerization during protozoan life cycle its activity was assessed by western blot analyses. Our results indicated that compound 5 had a profound effect on tubulin function. A detailed structure activity relationship (SAR) was summarized that will be used to guide future lead optimization.

Recombinant α- and β-tubulin from Echinococcus granulosus: expression, purification and polymerization

Echinococcosis, which causes a high disease burden and is of great public health significance, is caused by the larval stage of Echinococcus species. It has been suggested that tubulin is the target of benzimidazoles, the only drugs for the treatment of echinococcosis. This study evaluated the characteristics of tubulins from Echinococcus granulosus. The full-length cDNAs of E. granulosus α- and β-tubulin isoforms were cloned by reverse transcription PCR from protoscolex RNA. Then, these two tubulin isoforms (α₉ and β₄) were recombinantly expressed as insoluble inclusion bodies in Escherichia coli. Nickel affinity chromatography was used to purify and refold the contents of these inclusion bodies as active proteins. The polymerization of tubulins was monitored by UV spectrophotometry (A₃₅₀) and confirmed by confocal microscopy and transmission electron microscopy (TEM). Nucleotide sequence analysis revealed that E. granulosus 1356 bp α₉-tubulin and 1332 bp β₄-tubulin encode corresponding proteins of 451 and 443 amino acids. The average yields of α₉- and β₄-tubulin were 2.0–3.0 mg/L and 3.5–5.0 mg/L of culture, respectively. Moreover, recombinant α₉- and β₄-tubulin were capable of polymerizing into microtubule-like structures under appropriate conditions in vitro. These recombinant tubulins could be helpful for screening anti-Echinococcus compounds targeting the tubulins of E. granulosus.

Effectiveness and Tolerability of 3-Day Mebendazole Treatment of Giardia duodenalis Infection in Adults and Children: Two Prospective, Open-Label Phase IV Trials

BACKGROUND

Giardia duodenalis is the most common intestinal pathogenic protozoan infection reported in humans. Both in vitro studies and 4 separate, sequential, comparative clinical trials conducted by our group in Cuba demonstrated mebendazole activity against G. duodenalis infection in both children and adults.

OBJECTIVE

The 2 additional, prospective, open-label, Phase IV follow-up studies reported here were performed to further assess the effectiveness and safety profile of mebendazole in the outpatient treatment of G. duodenalis infection.

METHODS

Assenting children (n = 522) whose guardians gave permission and consenting adults (n = 423) diagnosed with G. duodenalis infection were given mebendazole (200 mg 3 times daily for 3 days). Medical histories and stool samples were obtained and physical/laboratory examinations were performed pretreatment then repeated on days 3, 5, and 7 after treatment completion. The evaluation of efficacy (ie, cure) was based on parasitologic response to therapy. Participants were considered cured, if no Giardia trophozoites or cysts were found in any of the 3 posttreatment fecal specimens evaluated by direct wet mounts and/or after Ritchie concentration techniques.

RESULTS

No participant refused to be enrolled and all returned for follow-up examinations. At the end of the treatment, stool samples were negative in 450 out of 522 children (86.2%) and 392 of 423 adults (92.7%). Treatment was well tolerated. In adults, the only adverse effect reported was abdominal pain (6.2%). Side effects reported in children included abdominal pain (5.6%), nausea (2.9%), and vomiting (2.3%). Reported side effects were all mild, transient, and self-limited and did not require discontinuation of treatment or additional medication.

CONCLUSIONS

Mebendazole may be an effective alternative treatment of G. duodenalis infections in both children and adults.

Therapeutic targets for the treatment of microsporidiosis in humans

INTRODUCTION

Microsporidia have been increasingly reported to infect humans. The most common presentation of microsporidiosis is chronic diarrhea, a significant mortality risk in immune-compromised patients. Albendazole, which inhibits tubulin, and fumagillin, which inhibits methionine aminopeptidase type 2 (MetAP2), are the two main therapeutic agents used for treatment of microsporidiosis. In addition, to their role as emerging pathogens in humans, microsporidia are important pathogens in insects, aquaculture, and veterinary medicine. New therapeutic targets and therapies have become a recent focus of attention for medicine, veterinary, and agricultural use. Areas covered: Herein, we discuss the detection and symptoms of microsporidiosis in humans and the therapeutic targets that have been utilized for the design of new drugs for the treatment of this infection, including triosephosphate isomerase, tubulin, MetAP2, topoisomerase IV, chitin synthases, and polyamines. Expert opinion: Enterocytozoon bieneusi is the most common microsporidia in human infection. Fumagillin has a broader anti-microsporidian activity than albendazole and is active against both Ent. bieneusi and Encephaliozoonidae. Microsporidia lack methionine aminopeptidase type 1 and are, therefore, dependent on MetAP2, while mammalian cells have both enzymes. Thus, MetAP2 is an essential enzyme in microsporidia and new inhibitors of this pathway have significant promise as therapeutic agents.

Chemotherapeutic options for the treatment of human trichomoniasis

Trichomonas vaginalis is the causative agent of the most common non-viral sexually transmitted disease worldwide. The infection may be associated with severe complications, including infertility, preterm labour, cancer and an increased risk of human immunodeficiency virus (HIV) transmission. Treatment remains almost exclusively based on 5-nitroimidazoles, but resistance is on the rise. This article provides an overview of clinically evaluated systemic and topical treatment options for human trichomoniasis and summarises the current state of knowledge on various herbal, semisynthetic and synthetic compounds evaluated for their anti-Trichomonas efficacy in vitro.

The novel microtubule-associated CAP-glycine protein Cgp1 governs growth, differentiation, and virulence of Cryptococcus neoformans

Microtubules are involved in mechanical support, cytoplasmic organization, and several cellular processes by interacting with diverse microtubule-associated proteins such as plus-end tracking proteins, motor proteins, and tubulin-folding cofactors. A number of the cytoskeleton-associated proteins (CAPs) contain the CAP-glycine-rich (CAP-Gly) domain, which is evolutionarily conserved and generally considered to bind to α-tubulin to regulate the function of microtubules. However, there has been a dearth of research on CAP-Gly proteins in fungal pathogens, including Cryptococcus neoformans, which is a global cause of fatal meningoencephalitis in immunocompromised patients. In this study, we identified five CAP-Gly protein-encoding genes in C. neoformans. Among these, Cgp1 encoded by CNAG_06352 has a unique domain structure containing CAP-Gly, SPEC, and Spc7 domains that is not orthologous to CAPs in other eukaryotes. Supporting the role of Cgp1 in microtubule-related function, we demonstrate that deletion or overexpression of CGP1 alters cellular susceptibility to thiabendazole, a microtubule destabilizer and that Cgp1 is co-localized with cytoplasmic microtubules. Related to the cellular function of microtubules, Cgp1 governs the maintenance of membrane stability and genotoxic stress responses. Deletion of CGP1 also reduces production of melanin pigment and attenuates the virulence of C. neoformans. Furthermore, we demonstrate that Cgp1 uniquely regulates the sexual differentiation of C. neoformans with distinct roles in the early and late stage of mating. Domain analysis revealed that the CAP-Gly domain plays a major role in all Cgp1 functions examined. In conclusion, this novel CAP-Gly protein, Cgp1, has pleotropic roles in regulating growth, stress responses, differentiation, and virulence in C. neoformans.

Fragment-Based Phenotypic Lead Discovery: Cell-Based Assay to Target Leishmaniasis

A rapid and practical approach for the discovery of new chemical matter for targeting pathogens and diseases is described. Fragment-based phenotypic lead discovery (FPLD) combines aspects of traditional fragment-based lead discovery (FBLD), which involves the screening of small-molecule fragment libraries to target specific proteins, with phenotypic lead discovery (PLD), which typically involves the screening of drug-like compounds in cell-based assays. To enable FPLD, a diverse library of fragments was first designed, assembled, and curated. This library of soluble, low-molecular-weight compounds was then pooled to expedite screening. Axenic cultures of Leishmania promastigotes were screened, and single hits were then tested for leishmanicidal activity against intracellular amastigote forms in infected murine bone-marrow-derived macrophages without evidence of toxicity toward mammalian cells. These studies demonstrate that FPLD can be a rapid and effective means to discover hits that can serve as leads for further medicinal chemistry purposes or as tool compounds for identifying known or novel targets.

Binding of Pollutants to Biomolecules: A Simulation Study

A number of cases around the world have been reported where animals were found dead or dying with symptoms resembling a thiamine (vitamin B) deficiency, and for some of these, a link to pollutants has been suggested. Here, we investigate whether biomolecules involved in thiamin binding and transport could be blocked by a range of different pollutants. We used in silico docking of five compound classes (25 compounds in total) to each of five targets (prion protein, ECF-type ABC transporter, thi-box riboswitch receptor, thiamin pyrophosphokinase, and YKoF protein) and subsequently performed molecular dynamics (MD) simulations to assess the stability of the complexes. The compound classes were thiamin analogues (control), pesticides, veterinary medicines, polychlorinated biphenyls, and dioxins, all of which are prevalent in the environment to some extent. A few anthropogenic compounds were found to bind the ECF-type ABC transporter, but none binds stably to prion protein. For the riboswitch, most compounds remained in their binding pockets during 50 ns of MD simulation, indicating that RNA provides a promiscuous binding site. In both YKoF and thiamin pyrophosphokinase (TPK), most compounds remain tightly bound. However, TPK biomolecules undergo pollutant-induced conformational changes. Although most compounds are found to bind to some of these targets, a larger data set is needed along with more quantitative methods like free energy perturbation calculations before firm conclusions can be drawn. This study is in part a test bed for large-scale quantitative computational screening of interactions between biological entities and pollutant molecules.

Antifungal and anthelmintic activity of novel benzofuran derivatives containing thiazolo benzimidazole nucleus: an in vitro evaluation

A novel series of thiazolo[3,2-a]benzimidazole derivatives containing benzofuran nucleus (5a-l) have been synthesized. The key intermediate, substituted benzimidazol-sulfanyl benzofuran ethanone (3a-d) was prepared by refluxing the mixture of substituted 2-acetyl benzofuran and substituted 2-mercaptobenzimidazole in acetic acid. The cyclisation of compounds (3a-d) using polyphosphoric acid furnished the corresponding 6-substituted benzofuran thiazolo[3,2-a]benzimidazoles (4a-d). Further, the cyclized compounds (4a-d) were subjected for Mannich reaction to give corresponding Mannich bases (5a-l). All newly synthesized compounds were screened for antifungal and anthelmintic activity. Amongst the tested compounds, 4b and 4d exhibited potential antifungal activity. From the anthelmintic activity data, it was found that the compounds 3a, 3b and 5i were found to be more effective against the tested earthworm Pheretima posthuma. In correlation to anthelmintic activity, the selected compounds were subjected for molecular docking studies and the compounds 3a and 5i have emerged as active anthelmintic agents with maximum binding affinity (-3.7 and -5.4 kcal/mol).

Novel drug design for Chagas disease via targeting Trypanosoma cruzi tubulin: Homology modeling and binding pocket prediction on Trypanosoma cruzi tubulin polymerization inhibition by naphthoquinone derivatives

Chagas disease, also called American trypanosomiasis, is a parasitic disease caused by Trypanosoma cruzi (T. cruzi). Recent findings have underscored the abundance of the causative organism, (T. cruzi), especially in the southern tier states of the US and the risk burden for the rural farming communities there. Due to a lack of safe and effective drugs, there is an urgent need for novel therapeutic options for treating Chagas disease. We report here our first scientific effort to pursue a novel drug design for treating Chagas disease via the targeting of T. cruzi tubulin. First, the anti T. cruzi tubulin activities of five naphthoquinone derivatives were determined and correlated to their anti-trypanosomal activities. The correlation between the ligand activities against the T. cruzi organism and their tubulin inhibitory activities was very strong with a Pearson's r value of 0.88 (P value <0.05), indicating that this class of compounds could inhibit the activity of the trypanosome organism via T. cruzi tubulin polymerization inhibition. Subsequent molecular modeling studies were carried out to understand the mechanisms of the anti-tubulin activities, wherein, the homology model of T. cruzi tubulin dimer was generated and the putative binding site of naphthoquinone derivatives was predicted. The correlation coefficient for ligand anti-tubulin activities and their binding energies at the putative pocket was found to be r=0.79, a high correlation efficiency that was not replicated in contiguous candidate pockets. The homology model of T. cruzi tubulin and the identification of its putative binding site lay a solid ground for further structure based drug design, including molecular docking and pharmacophore analysis. This study presents a new opportunity for designing potent and selective drugs for Chagas disease.

Drug target identification in protozoan parasites

INTRODUCTION

Despite the fact that diseases caused by protozoan parasites represent serious challenges for public health, animal production and welfare, only a limited panel of drugs has been marketed for clinical applications.

AREAS COVERED

Herein, the authors investigate two strategies, namely whole organism screening and target-based drug design. The present pharmacopoeia has resulted from whole organism screening, and the mode of action and targets of selected drugs are discussed. However, the more recent extensive genome sequencing efforts and the development of dry and wet lab genomics and proteomics that allow high-throughput screening of interactions between micromolecules and recombinant proteins has resulted in target-based drug design as the predominant focus in anti-parasitic drug development. Selected examples of target-based drug design studies are presented, and calcium-dependent protein kinases, important drug targets in apicomplexan parasites, are discussed in more detail.

EXPERT OPINION

Despite the enormous efforts in target-based drug development, this approach has not yet generated market-ready antiprotozoal drugs. However, whole-organism screening approaches, comprising of both in vitro and in vivo investigations, should not be disregarded. The repurposing of already approved and marketed drugs could be a suitable strategy to avoid fastidious approval procedures, especially in the case of neglected or veterinary parasitoses.

Detection of beta-tubulin in the cytoplasm of the interphasic Entamoeba histolytica trophozoites

It is known that the microtubules (MT) of Entamoeba histolytica trophozoites form an intranuclear mitotic spindle. However, electron microscopy studies and the employment of anti-beta-tubulin (β-tubulin) antibodies have not exhibited these cytoskeletal structures in the cytoplasm of these parasites. The purpose of this work was to detect β-tubulin in the cytoplasm of interphasic E. histolytica trophozoites. Activated or non-activated HMI-IMSS-strain E. histolytica trophozoites were used and cultured for 72 h at 37 °C in TYI-S-33 medium, and then these were incubated with the anti-β-tubulin antibody of E. histolytica. The anti-β-tubulin antibody reacted with the intranuclear mitotic spindle of E. histolytica-activated trophozoites as control. In contrast, in non-activated interphasic parasites, anti-β-tubulin antibody reacted with diverse puntiform structures in the cytoplasm and with ring-shaped structures localized in the cytoplasm, cellular membrane and endocytic stomas. In this work, for the first time, the presence of β-tubulin is shown in the cytoplasm of E. histolytica trophozoites.

Repositioning of drugs for intervention in tumor progression and metastasis: Old drugs for new targets

The increasing unraveling of the molecular basis of cancer offers manifold novel options for intervention strategies. However, the discovery and development of new drugs for potential clinical applications is a tremendously time-consuming and costly process. Translating a novel lead candidate compound into an approved clinical drug takes often more than a decade, and the success rate is very low due to versatile efforts including defining its pharmacokinetics, pharmacodynamics, side effects as well as lack of sufficient efficacy. Thus, strategies are needed to minimize time and costs, while maximizing success rates. A very attractive strategy for novel cancer therapeutic options is the repositioning of already approved drugs. These medicines, approved for the treatment of non-malignant disorders, have already passed some early costs and time, have been tested in humans and are ready for clinical trials as anti-cancer drugs. Here we discuss the repositioning of nonsteroidal anti-inflammatory drugs (NSAID), statins, anti-psychotic drugs, anti-helminthic drugs and vitamin D as anti-tumor agents. We focus on their novel actions and potential for inhibition of cancer growth and metastasis by interfering with target molecules and pathways, which drive these malignant processes. Furthermore, important pre-clinical and clinical data are reviewed herein, which elucidate their therapeutic mechanisms which enable their repositioning for cancer therapy and disruption of metastasis.

Flubendazole, FDA-approved anthelmintic, targets breast cancer stem-like cells

Cancer stem-like cell (CS-like cell) is considered to be responsible for recurrence and drug resistance events in breast cancer, which makes it a potential target for novel cancer therapeutic strategy. The FDA approved flubendazole, has been widely used in the treatment of intestinal parasites. Here, we demonstrated a novel effect of flubendazole on breast CS-like cells. Flubendazole inhibited breast cancer cells proliferation in dose- and time-dependent manner and delayed tumor growth in xenograft models by intraperitoneal injection. Importantly, flubendazole reduced CD44^high/CD24^low subpopulation and suppressed the formation of mammosphere and the expression of self-renewal related genes including c-myc, oct4, sox2, nanog and cyclinD1. Moreover, we found that flubendazole induced cell differentiation and inhibited cell migration. Consistently, flubendazole reduced mesenchymal markers (β-catenin, N-cadherin and Vimentin) expression and induced epithelial and differentiation marker (Keratin 18) expression in breast cancer cells. Mechanism study revealed that flubendazole arrested cell cycle at G2/M phase and induced monopolar spindle formation through inhibiting tubulin polymerization. Furthermore, flubendazole enhanced cytotoxic activity of conventional therapeutic drugs fluorouracil and doxorubicin against breast cancer cells. In conclusion, our findings uncovered a remarkable effect of flubendazole on suppressing breast CS-like cells, indicating a novel utilization of flubendazole in breast cancer therapy.

Synthesis and characterization of 2-substituted benzimidazoles and their evaluation as anticancer agent

In this work, we report a series of benzimidazole derivatives synthesized from benzene-1,2-diamine and aryl-aldehydes at room temperature. The synthesized compounds have been characterized on the basis of elemental analysis and various spectroscopic studies viz., IR, (1)H- and (13)C-NMR, ESI-MS as well by X-ray single X-ray crystallographic study. Interaction of these compounds with CT-DNA has been examined with fluorescence experiments and showed significant binding ability. All the synthesized compounds have been screened for their antitumor activities against various human cancer cell lines viz., Human breast adenocarcinoma cell line (MCF-7), Human leukemia cell line (THP-1), Human prostate cancer cell lines (PC-3) and adenocarcinomic human alveolar basal epithelial cell lines (A-549). Interestingly, all the compounds showed significant anticancer activity.

Analysis of the beta-tubulin gene and morphological changes of the microsporidium Anncaliia algerae both suggest albendazole sensitivity

The Microsporidium, Anncaliia algerae, an obligate intracellular parasite, has been identified as an opportunistic human pathogen, but treatment has not been evaluated for infections with this organism. Albendazole, an antitubulin polymerization drug used against parasitic worm infections, has been the medication of choice used to treat some microsporidial infections affecting humans, with varying results ranging from clearing infection (Encephalitozoon) to resistance (Enterocytozoon). This study illustrates the effect of albendazole treatment on A. algerae infection in Rabbit Kidney (RK13) cells and Human Fetal Lung (HFL-1) fibroblasts. Albendazole appears to have an attenuating effect on A. algerae infection and albendazole's IC50 in RK13 cells is 0.1 μg/ml. Long-term treatment inhibits up to 98% of spore production, but interrupting treatment reestablishes the infection without new exposure to the parasite as supported by microscopic observations. The parasite's beta-tubulin gene was purified, cloned, and sequenced. Five of the six specific amino acids, associated with benzimidazole sensitivity, are conserved in A. algerae. These findings suggest that A. algerae is sensitive to albendazole; however, the organism is not completely cleared from cultures.

JVG9, a benzimidazole derivative, alters the surface and cytoskeleton of Trypanosoma cruzi bloodstream trypomastigotes

Trypanosoma cruzi has a particular cytoskeleton that consists of a subpellicular network of microtubules and actin microfilaments. Therefore, it is an excellent target for the development of new anti-parasitic drugs. Benzimidazole 2-carbamates, a class of well-known broad-spectrum anthelmintics, have been shown to inhibit the in vitro growth of many protozoa. Therefore, to find efficient anti-trypanosomal (trypanocidal) drugs, our group has designed and synthesised several benzimidazole derivatives. One, named JVG9 (5-chloro-1H-benzimidazole-2-thiol), has been found to be effective against T. cruzi bloodstream trypomastigotes under both in vitro and in vivo conditions. Here, we present the in vitro effects observed by laser scanning confocal and scanning electron microscopy on T. cruzi trypomastigotes. Changes in the surface and the distribution of the cytoskeletal proteins are consistent with the hypothesis that the trypanocidal activity of JVG9 involves the cytoskeleton as a target.