The benzimidazole anthelmintic agents--a review

Superb bio-effectiveness of Cobalt (II) phthalocyanine and Ag NPs adorned Sm-doped ZnO nanorods/cuttlefish bone to annihilate Trichinella spiralis muscle larvae and adult worms: In-vitro evaluation

Herein, innovative biocides are designed for the treatment of Trichinella spiralis muscle larvae (ML) and adult worms. Samarium-doped ZnO nanorods (Sm-doped ZnO) are stabilized onto the laminar structure of cuttlefish bone (CB) matrix and adorned by either Ag NPs or cobalt phthalocyanine (CoPc) species. Physicochemical characteristics of such nanocomposites are scrutinised. Adorning of Sm-doped ZnO/CB with Ag NPs shortens rod-like shaped Sm-doped ZnO nanoparticles and accrues them, developing large-sized detached patches over CB moiety. Meanwhile, adorning of Sm-doped ZnO/CB by CoPc species degenerates CB lamellae forming semi-rounded platelets and encourages invading of Sm-doped ZnO nanorods deeply inside gallery spacings of CB. Both nanocomposites possess advanced parasiticidal activity, displaying quite intoxication for ML and adult worms (≥88% mortality) within an incubation period of <48 h at concentrations around 200 μg/ml. CoPc@Sm-doped ZnO/CB nanocomposite exhibits faster killing efficiency of adult worms than that of Ag@Sm-doped ZnO/CB at a concentration of ∼75 μg/ml showing entire destruction of parasite after 24 h incubation with the former nanocomposite and just 60% worm mortality after 36 h exposure to the later one. Morphological studies of the treated ML and adult worms show that CoPc@Sm-doped ZnO/CB exhibits a destructive impact on the parasite body, creating featureless and sloughed fragments enriched with intensive vacuoles. Hybridization of cuttlefish bone lamellae by CoPc species is considered a springboard for fabrication of futuristic aggressive drugs against various food- and water-borne parasites.

Proteomics reveals that the antifungal activity of fenbendazole against Cryptococcus neoformans requires protein kinases

Cryptococcus neoformans is responsible for over 100 000 deaths annually, and the treatment of this fungal disease is expensive and not consistently effective. Unveiling new therapeutic avenues is crucial. Previous studies have suggested that the anthelmintic drug fenbendazole is an affordable and nontoxic candidate to combat cryptococcosis. However, its mechanism of anticryptococcal activity has been only superficially investigated. In this study, we examined the global cellular response of C. neoformans to fenbendazole using a proteomic approach (data are available via ProteomeXchange with identifier PXD047041). Fenbendazole treatment mostly impacted the abundance of proteins related to metabolic pathways, RNA processing, and intracellular traffic. Protein kinases, in particular, were significantly affected by fenbendazole treatment. Experimental validation of the proteomics data using a collection of C. neoformans mutants led to the identification of critical roles of five protein kinases in fenbendazole's antifungal activity. In fact, mutants lacking the expression of genes encoding Chk1, Tco2, Tco3, Bub1, and Sch9 kinases demonstrated greater resistance to fenbendazole compared to wild-type cells. In combination with the standard antifungal drug amphotericin B, fenbendazole reduced the cryptococcal burden in mice. These findings not only contribute to the elucidation of fenbendazole's mode of action but also support its use in combination therapy with amphotericin B. In conclusion, our data suggest that fenbendazole holds promise for further development as an anticryptococcal agent.

Fosfatriclaben, a prodrug of triclabendazole: Preparation, stability, and fasciolicidal activity of three new intramuscular formulations

In this study, we present the preparation, stability, and in vivo fasciolicidal activity of three new intramuscular formulations in sheep of a prodrug based on triclabendazole, named fosfatriclaben. The new formulations were ready-to-use aqueous solutions with volumes recommended for intramuscular administration in sheep. The use of poloxamers (P-407 and P-188) and polysorbates (PS-20 and PS-80) in the new formulations improved the aqueous solubility of fosfatriclaben by 8-fold at pH 7.4. High-performance liquid chromatography with UV detection was used to evaluate the stability of fosfatriclaben in the three formulations. High recovery (> 90%) of fosfatriclaben was found for all formulations after exposure at 57 ± 2 °C for 50 h. The three intramuscular formulations showed high fasciolicidal activity at a dose of 6 mg/kg, which was equivalent to the triclabendazole content. The fasciolicidal activity of fosfatriclaben was similar to commercial oral (Fasimec®) and intramuscular (Endovet®) triclabendazole formulations at a dose of 12 mg/kg. In the in vivo experiments, all formulations administered intramuscularly reduced egg excretion by 100%, and formulations F1, F2, and F3 presented fasciolicidal activities of 100%, 100%, and 99.6%, respectively.

Development and validation of stability indicating UPLC methods for related substances and assay analyses of ricobendazole hydrochloride

Ricobendazole hydrochloride is an active ingredient of a veterinary antiparasitic drug. The aim of this study was to investigate the degradation of ricobendazole hydrochloride under stress and stability testing conditions, for which we developed and validated the first stability indicating, specific, precise, accurate, and robust assay and related substances UPLC methods. The Acquity UPLC BEH C18 column was used for the related substances and assay analyses of ricobendazole hydrochloride, and the analyses were performed at 25 °C sample and 30 °C column temperatures with a 2 µL injection volume. In both methods, a mixture of water and methanol (60:40, v/v) was used as the diluent, mobile phase A was a phosphate buffer (50 mM potassium dihydrogen phosphate solution, pH 3.2 ± 0.05, adjusted with 10% o-phosphoric acid), and mobile phase B was a mixture of mobile phase A and acetonitrile (50:50, v/v). For the analysis of related substances, a gradient elution system was used at a flow rate of 0.4 mL/min for 35 min with a detection wavelength of 220 nm, while for the assay analysis; a gradient elution system was used at a flow rate of 0.3 mL/min for 15 min with a detection wavelength of 290 nm. The calibration curves showed excellent linearity with high R-squared (R2) values for each compound, ricobendazole (0.9998, 0.249 - 3.740 µg/mL), ricobendazole amine (0.9998, 0.255 - 3.819 µg/mL), albendazole (0.9998, 0.255 - 7.646 µg/mL), and albendazole sulfone (1.0000, 0.251 - 15.090 µg/mL) indicating a strong correlation between the concentrations of the compounds and their respective peak areas in the UPLC analysis. The method showed excellent accuracy with relative standard deviation values of less than 2.5%. The stress and photostability studies showed that ricobendazole hydrochloride was insensitive to daylight and UV radiation and showed significant degradation at elevated temperature (85 °C, 9 days) and under all hydrolysis and oxidation conditions. The major impurity was ricobendazole amine under thermal and hydrolysis conditions, while albendazole sulfone was the major oxidative impurity.

Structure-Based Optimization of Carbendazim-Derived Tubulin Polymerization Inhibitors through Alchemical Free Energy Calculations

Carbendazim derivatives, commonly used as antiparasitic drugs, have shown potential as anticancer agents due to their ability to induce cell cycle arrest and apoptosis in human cancer cells by inhibiting tubulin polymerization. Crystallographic structures of α/β-tubulin multimers complexed with nocodazole and mebendazole, two carbendazim derivatives with potent anticancer activity, highlighted the possibility of designing compounds that occupy both benzimidazole- and colchicine-binding sites. In addition, previous studies have demonstrated that the incorporation of a phenoxy group at position 5/6 of carbendazim increases the antiproliferative activity in cancer cell lines. Despite the significant progress made in identifying new tubulin-targeting anticancer compounds, further modifications are needed to enhance their potency and safety. In this study, we explored the impact of modifying the phenoxy substitution pattern on antiproliferative activity. Alchemical free energy calculations were used to predict the binding free energy difference upon ligand modification and define the most viable path for structure optimization. Based on these calculations, seven compounds were synthesized and evaluated against lung and colon cancer cell lines. Our results showed that compound 5a, which incorporates an α-naphthyloxy substitution, exhibits the highest antiproliferative activity against both cancer lines (SK-LU-1 and SW620, IC50 < 100 nM) and induces morphological changes in the cells associated with mitotic arrest and mitotic catastrophe. Nevertheless, the tubulin polymerization assay showed that 5a has a lower inhibitory potency than nocodazole. Molecular dynamics simulations suggested that this low antitubulin activity could be associated with the loss of the key H-bond interaction with V236. This study provides insights into the design of novel carbendazim derivatives with anticancer activity.

Isolation of soil bacteria able to degrade the anthelminthic compound albendazole

Anthelmintic (AHs) veterinary drugs constitute major environmental contaminants. The use of AH-contaminated fecal material as manures in agricultural settings constitutes their main route of environmental dispersal. Once in soils, these compounds induce toxic effects to soil fauna and soil microbiota, both having a pivotal role in soil ecosystem functioning. Therefore, it is necessary to identify mitigation strategies to restrict the environmental dispersal of AHs. Bioaugmentation of AH-contaminated manures or soils with specialized microbial inocula constitutes a promising remediation strategy. In the present study, we aimed to isolate microorganisms able to actively transform the most widely used benzimidazole anthelminthic albendazole (ABZ). Enrichment cultures in minimal growth media inoculated with a soil known to exhibit rapid degradation of ABZ led to the isolation of two bacterial cultures able to actively degrade ABZ. Two oxidative products of ABZ, ABZSO and ABZSO2, were detected at low amounts along its degradation. This suggested that the oxidation of ABZ is not a major transformation process in the isolated bacteria which most probably use other biotic pathways to degrade ABZ leading to the formation of products not monitored in this study. Full length sequencing of their 16S rRNA gene and phylogenetic analysis assigned both strains to the genus Acinetobacter. The sequences were submitted in GeneBank NCBI, database with the accession numbers OP604271 to OP604273. Further studies will employ omic tools to identify the full transformation pathway and the associated genetic network of Acinetobacter isolates, information that will unlock the potential use of these isolates in the bioaugmentation of contaminated manures.

Interactions of anthelmintic veterinary drugs with the soil microbiota: Toxicity or enhanced biodegradation?

Anthelmintic (AH) compounds are used to control gastrointestinal nematodes (GINs) in livestock production. They are only partially metabolized in animals ending in animal excreta whose use as manures leads to AH dispersal in agricultural soils. Once in soil, AHs interact with soil microorganisms, with the outcome being either detrimental, or beneficial. We aimed to disentangle the mechanisms of these complex interactions. Two soils previously identified as « fast » or « slow», regarding the degradation of albendazole (ABZ), ivermectin (IVM), and eprinomectin (EPM), were subjected to repeated applications at two dose rates (1, 2 mg kg-1and 10, 20 mg kg-1). We hypothesized that this application scheme will lead to enhanced biodegradation in «fast » soils and accumulation and toxicity in «slow » soils. Repeated application of ABZ resulted in different transformation pathways in the two soils and a clear acceleration of its degradation in the «fast » soil only. In contrast residues of IVM and EPM accumulated in both soils. ABZ was the sole AH that induced a consistent reduction in the abundance of total fungi and crenarchaea. In addition, inhibition of nitrification and reduction in the abundance of ammonia-oxidizing bacteria (AOB) and archaea (AOA) by all AHs was observed, while commamox bacteria were less responsive. Amplicon sequencing analysis showed dose-depended shifts in the diversity of bacteria, fungi, and protists in response to AHs application. ABZ presented the most consistent effect on the abundance and diversity of most microbial groups. Our findings provide first evidence for the unexpected toxicity of AHs on key soil microbial groups that might have to be considered in a regulatory context.

Triclabendazole resistance in Fasciola hepatica: First report in sheep from the Santa Cruz province, Argentinian Patagonia

In the fall of 2022, decreased triclabendazole (TCBZ) efficacy against F. hepatica was suspected in a sheep farm located in the Santa Cruz province, Argentinian Patagonia. Since TCBZ-resistance in F. hepatica has never been reported in this province, this study aimed to confirm potential TCBZ-resistance in F. hepatica and to evaluate the efficacy of closantel (CLO) and nitroxinil (NTX), through faecal egg count reduction test (FECRT), and the efficacy of albendazole (ABZ) through the in vitro egg hatch test (EHT) in sheep. Sixty-eight (68) animals were selected from a herd of eighty (80) female Merino naturally infected with F. hepatica based on eggs per gram of F. hepatica (EPGFh) counts and assigned into four (4) groups (n = 17 per group): Group Control, animals did not receive anthelmintic treatment; Group TCBZ, animals were orally treated with TCBZ (12 mg/kg); Group CLO, animals were orally treated with CLO (10 mg/kg); and Group NTX, animals were subcutaneously treated with NTX (10 mg/kg). The fluke egg output was monitored on days 0 and 21 post-treatment. For the EHT, liver fluke eggs were isolated from faecal samples (approx. 50 g) collected from animals of the control group. TCBZ efficacy against liver fluke was 53.4%, confirming the presence of TCBZ-resistant isolates on the farm. CLO and NTX were highly effective (100%) for the treatment of F. hepatica on this farm. The EHT was carried out in two different laboratories, in which was observed an ABZ efficacy of 95.8 (Bariloche) and 96.5% (Tandil). These results indicate the ABZ susceptibility of this F. hepatica isolate and the inter-laboratory precision of the test.

Horse and donkey parasitology: differences and analogies for a correct diagnostic and management of major helminth infections

In June 2022, at the XXXII Conference of the Italian Society of Parasitology, the parallels of the main endoparasitic infections of horses and donkeys were discussed. Although these 2 species are genetically different, they can be challenged by a similar range of parasites (i.e. small and large strongyles, and Parascaris spp.). Although equids can demonstrate some level of resilience to parasites, they have quite distinct helminth biodiversity, distribution and intensity among different geographical locations and breeds. Heavily infected donkeys may show fewer clinical signs than horses. Although parasite control is primarily provided to horses, we consider that there may be a risk of drug-resistance parasitic infection through passive infection in donkeys when sharing the same pasture areas. Knowing the possible lack of drug efficacy (<90 or 80%), it is advocated the use of selective treatment for both species based on fecal egg counts. Adult horses should receive treatment when the threshold exceeds 200–500 eggs per gram (EPG) of small strongyles. Moreover, considering that there are no precise indications in donkeys, a value >300 EPG may be a safe recommendation. We have highlighted the main points of the discussion including the dynamics of helminth infections between the 2 species.

Design, synthesis, antimicrobial activity and molecular docking study of cationic bis-benzimidazole-silver(I) complexes

Two series of bis(1-alkylbenzimidazole)silver(I) nitrate and bis(1-alkyl-5,6-dimethylbenzimidazole)silver(I) nitrate complexes, in which the alkyl substituent is either an allyl, a 2-methylallyl, an isopropyl or a 3-methyloxetan-3-yl-methyl chain, were synthesized and fully characterized. The eight N-coordinated silver(I) complexes were screened for both antimicrobial activities against Gram-negative (Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae, and Acinetobacter baumannii) and Gram-positive (Staphylococcus aureus, Staphylococcus aureus MRSA, and Enterococcus faecalis) bacteria and antifungal activities against Candida albicans and Candida glabrata strains. Moderate minimal inhibitory concentrations (MIC) of 0.087 μmol/mL were found when the Gram-negative and Gram-positive bacteria were treated with the silver complexes. Nevertheless, MIC values of 0.011 μmol/mL, twice lower than for the well-known fluconazole, against the two fungi were measured. In addition, molecular docking was carried out with the structure of Escherichia coli DNA gyrase and CYP51 from the pathogen Candida glabrata with the eight organometallic complexes, and molecular reactivity descriptors were calculated with the density functional theory-based calculation methods.

Pharmacokinetics of mebendazole in plasma and cerebrospinal fluid following a single oral dose in healthy dogs

Novel therapies are needed for treatment of gliomas. Mebendazole previously demonstrated anti-neoplastic effects on canine glioma cell lines at in vitro mean inhibitory concentrations (IC50) of 10 ng/mL. Our study aimed to titrate the oral dose of mebendazole necessary to achieve concentrations ≥10 ng/mL in cerebrospinal fluid (CSF) of healthy dogs. We hypothesized that an oral dose up to 200 mg/kg would be necessary. Phase one was a dose titration study using a total of 6 mixed breed dogs that described dose vs. plasma concentrations for 72 h after single oral dosing of either 50 mg/kg (n = 2), 100 mg/kg (n = 2), or 200 mg/kg (n = 2). Based on phase one, phase two dogs (total of 9) received 100 mg/kg (n = 4) or 200 mg/kg (n = 5) orally and blood samples were collected intermittently for 60 h with CSF samples collected intermittently for 24 h. Mebendazole was quantitated in plasma and CSF using high performance liquid chromatography. Median peak plasma concentrations (Cmax) were reached at 7 ± 2 h (100 mg/kg) of 220 ng/mL (81, 283) and at 15 ± 4 h (200 mg/kg) of 147 ng/ml (112, 298). The respective area under the curve (AUC: ng/ml/h) reported as a median was 2,119 (1,876, 3,288) vs. 3,115 (1,559, 4,972). Median plasma concentrations (ng/ml) for 100 vs. 200 mg/kg were 47 (32, 52) vs. 65 (35, 104), respectively. For CSF, the median value for Cmax (at 100 mg/kg vs. 200 mg/kg) was 8 (2, 28) vs. 21 (12, 27) and AUC was 87 (22, 157) vs. 345 (92, 372), respectively. Relative bioavailability in CSF vs. plasma was 4 to 10%. Although several animals demonstrated clinical signs indicative of gastrointestinal upset [i.e., vomiting (n = 2), diarrhea (n = 2), or both (n = 1)], these events were not considered serious. The in vitro IC50 for gliomas can be reached in CSF at 100 mg/kg (n = 1), however a 200 mg/kg dose yielded more consistent concentrations.

Analysis, Occurrence and Exposure Evaluation of Antibiotic and Anthelmintic Residues in Whole Cow Milk from China

An optimized QuEChERS method for the simultaneous extraction of 26 antibiotics and 19 anthelmintics in whole cow milk was established, followed by UHPLC-MS/MS analysis. Briefly, 20 mL acetonitrile with 1 g disodium hydrogen citrate, 2 g sodium citrate, 4 g anhydrous MgSO₄, and 1 g sodium chloride were added to 10 g milk for target chemical extraction, followed by 50 mg anhydrous MgSO₄ for purification. Satisfactory recoveries were obtained using the modified QuEChERS method, with recoveries of the antibiotics ranging from 79.7 to 117.2%, with the exception of norfloxacin, which was at 53.4%, while those for anthelmintics were in the range of 73.1-105.1%. The optimized QuEChERS method presented good precision, with relative standard deviations ranging from 7.2 to 18.6% for both antibiotics and anthelmintics. The method was successfully applied to analyze the antibiotics and anthelmintics in 56 whole cow milk samples from China. Briefly, the detection frequencies and concentrations of most of the antibiotics and anthelmintics were low in the whole cow milk samples, with concentrations ranging from below LOD to 4296.8 ng/kg. Fenbendazole, febantel, enrofloxacin, levofloxacin, sulfadiazine, and sulfamethoxazole were the predominant drug residues in the whole cow milk samples. Spatial distribution was found for those antibiotics and anthelmintics with detection frequency higher than 50%, especially for the antibiotics, indicating regional differences in drug application. Based on the current study, exposure to antibiotics and anthelmintics through whole cow milk consumption are lower than the acceptable daily intake values suggested by the China Institute of Veterinary Drug Control. However, long-term exposure to low doses of antibiotics and anthelmintics still needs attention and merits further study.

Artemisia vulgaris anthelmintic activities to ova and adult stages of Fasciola gigantica in vitro

Background and Aim

Fasciolosis due to Fasciola gigantica is endemic to tropical countries and Fasciola hepatica in temperate climates, highly detrimental to livestock and known as foodborne zoonotic diseases. The strategic control of the disease is mainly the use of chemical anthelmintic. This study aimed to evaluate the anthelmintic properties of Artemisia vulgaris extract on the ova and adult stages of F. gigantica.

Materials and Methods

Samples were collected from the Ampel Abbatoir, Boyolali District, Central Java, Indonesia. The ova from 20-gallbladders of cattle which were naturally infected with F. gigantica and 270 living F. gigantica worms were used in this study. The ovicidal assay was performed by incubating the ova with A. vulgaris in different concentrations, that is, 5%, 2.5%, and 1.25% for 5, 9, 11, 14, and 16 days. The efficacies were evaluated by quantification of ova degeneration during developmental stages in different time points and egg-hatch assay. The flukicidal effects were observed by mortality assay in 5, 10, 20, 40, 80, 160, 320, and 640 min incubations followed by scanning electron microscopy for surface morphology and histology of the fluke's transversal sections.

Results

The concentration of 5% A. vulgaris showed the strongest ovicidal activities. The percentage of hatching ova on day 16 at concentrations of 5%, 2.5%, and 1.25% were 3.33%, 6.67%, and 16.67%. These ova hatch assay showed a significant reduction (p < 0.001) compared to untreated control. The flukicidal effect was significant (p < 0.001) at a concentration of 20%, with a mortality rate reaching 66.67% in the 40 min of incubation time. The surface properties of the adult worms, including the spine, tegument, acetabulum, intestine, and vitelline follicles, were disintegrated.

Conclusion

The results showed that A. vulgaris has the potential ovicidal and flukicidal properties to F. gigantica. The active compounds remained necessary to be elucidated further and its modes of action would be interesting to be predicted by molecular docking modeling.

Fenbendazole treatment against Dentostomella translucida in Syrian golden hamsters

Dentostomella translucida is an oxyurid nematode that was first discovered in the Mongolian gerbil but has also been detected in other wild and housed rodents. In conventional laboratory animals, oxyurid nematode parasites are widespread infections. A proven treatment strategy for pinworm eradication is the oral application of benzimidazoles, such as fenbendazole. In general, this drug is regarded as safe with minimal side effects. Nevertheless, in Sprague Dawley rats, a significantly reduced litter size could be seen after longer treatment with fenbendazole. Even though Dentostomella translucida was already described in Syrian golden hamsters (Mesocricetus auratus), data on treatment with fenbendazole and its effects on reproduction is lacking. Therefore, the main purposes of the study were (1) the verification of the effectiveness of fenbendazole as medicated feed (150 ppm) against this parasite in naturally infected Syrian golden hamsters in conventional husbandry and (2) monitoring of possible effects on reproduction during the treatment. Results show that fenbendazole treatment was highly effective against Dentostomella translucida, as numbers of pinworm eggs in the faeces were significantly reduced already after the first week of treatment in all animals. After four weeks of treatment, eggs were eradicated entirely. Interestingly, the average weaning weight was significantly reduced during treatment, but the litters were in good health.

Feeding Management and Albendazole Pharmacokinetics in Pigs

Albendazole (ABZ) is a methylcarbamate benzimidazole anthelmintic used to control gastrointestinal parasites in several animal species and humans. The type of diet has been identified as a major determinant for ABZ pharmacokinetics in different animal species and humans. The work described here assesses the pattern of the absorption and the systemic availability of ABZ and its metabolites after its oral administration to pigs under different feed management plans. Eighteen pigs (5 months old, local ecotype breeds) were distributed into three experimental groups. In the fasting group, the animals fasted for 8 h prior to treatment. In the pellet + oil and pellet groups, the animals were fed ad libitum with a commercial pelleted-based diet with or without the addition of soya oil. An ABZ suspension was orally administered at 10 mg/kg. Blood samples were taken over the 48 h post-treatment. The plasma samples were analyzed by HPLC. Under the described experimental conditions, the ingestion of the pellet-based diet with or without the soya oil before ABZ treatment did not significantly (p < 0.05) modify the plasma disposition kinetics of the ABZ sulfoxide (ABZSO, the main ABZ metabolite) compared to that observed in the fasting pigs. Both ABZ metabolites (ABZSO and ABZ sulphone) reached similar peak concentrations and systemic exposures in all the experimental groups regardless of the feeding management. However, the addition of oil to the pelleted food enhanced the pattern of ABZ absorption, which was reflected in the higher (p < 0.05) concentration profiles of the active ABZSO metabolite measured between 12 and 48 h post-treatment compared to the pigs fed with the pelleted food alone. Although this effect may not be therapeutically relevant after ABZ administration as a single oral dose, the overall impact of the type and feeding conditions when ABZ is supplemented with food for several days should be cautiously evaluated.

Enteropathy and bone marrow hypoplasia associated with presumptive albendazole toxicosis in a juvenile Boer goat

Albendazole is a widely used anthelmintic drug that is labeled for the treatment of specific nematodes and flukes in ruminants. Albendazole is approved for the treatment of liver flukes in goats (10 mg/kg PO for a single dose), but is commonly used extra-label in situations in which parasite resistance is an issue. Albendazole toxicosis has been reported in pigeons, doves, alpacas, humans, dogs, and cats. Here we report an adverse event in a 6-mo-old goat associated with extra-label use of albendazole (35.7 mg/kg PO daily for 3 d). Clinicopathologic findings included severe diarrhea and death, with small intestinal crypt necrosis and dysplasia, and severe bone marrow hypoplasia. Microbial and molecular testing and transmission electron microscopy ruled out infectious organisms. The described pathologic changes are similar to those reported in other species that have experienced toxicosis associated with albendazole. To our knowledge, bone marrow and intestinal lesions associated with albendazole use in the goat have not been reported previously. Veterinarians should be aware of potential adverse events and toxicoses associated with anthelmintic drugs, especially as parasite resistance increases, and extra-label usage, and the use of such drugs without veterinary supervision, becomes more common.

Biodegradation of anthelmintics in soils: does prior exposure of soils to anthelmintics accelerate their dissipation?

Anthelmintics (AHs) control animal infections with gastrointestinal nematodes. They reach soil through animal faeces deposited on soils or through manuring. Although soil constitutes a major AH sink, we know little about the mechanisms controlling their soil dissipation. We employed studies with fumigated and non-fumigated soils collected from 12 sheep farms with a variable record of albendazole (ABZ), ivermectin (IVM) and eprinomectin (EPM) use. From each farm, we collected soils from inside small ruminant barn facilities (series A, high exposure) and the associated grazing pastures (series B, low exposure). We asked the following questions: (a) What is the role of soil microorganisms in AH dissipation? (b) Does repeated exposure of soils to AHs lead to their accelerated biodegradation? (c) Which soil physicochemical properties control AH dissipation? Soil fumigation significantly retarded ABZ (DT₅₀ 1.9 and 4.33 days), IVM (34.5 and 108.7 days) and EPM dissipation (30 and 121 days) suggesting a key role of soil microorganisms in AH dissipation. No significant acceleration in AH dissipation was evident in soils from units with a record of the administration of AHs or in soil series A vs series B, suggesting that the level of prior exposure was not adequate to induce their enhanced biodegradation. Significant positive and negative correlations of soil total organic carbon (TOC) and ABZ and IVM dissipation, respectively, were observed. Soil adsorption of AHs increased in the order IVM > ABZ > EPM. TOC controlled soil adsorption of IVM and EPM, but not of ABZ, in support of the contrasting effect of TOC on IVM and ABZ dissipation.

Teaching an old dog new tricks: The case of Fenbendazole

The objective of this study is the assessment of the cytotoxic effect of fenbendazole and its commercially available formulation, which is used for its antihelmintic properties. The formulation was tested for its efficacy as well as the determination of the ingredients with proliferation assays and analytical techniques. HPLC, LC-MS and NMR confirmed the stated amount of active ingredient on the label. Dissolution studies were performed to simulate the ability of fenbendazole to dissolve adequately in the fluids of the Gastrointestinal tract, be absorbed in the circulation and reach certain areas of the human body. However, dissolution studies showed that both brands possess issues in their distribution. The in vitro drug screening exhibited potential cytotoxic effect in different types of human cancer cell lines and MDA-MB-231 human breast adenocarcinoma cells appeared to be the most sensitive with IC₅₀ value lower than 10 μM.

Salvage Therapy for Alveolar Echinococcosis—A Case Series

Benzimidazoles are the only approved drugs for the treatment of inoperable human alveolar echinococcosis but may be limited due to intolerance or, rarely, ineffectiveness. A medical second-line or salvage therapy is not available, though it is urgently needed. We report long-term follow-up data from 14 patients who underwent salvage therapy with repurposed drugs with cumulatively 53.25 patient-years. Treatment response was evaluated by both clinical outcome and image studies, preferably PET/CT. Eleven patients received amphotericin B, and 70% of evaluable cases showed some positive treatment response, but side effects often limited therapy. Five patients received nitazoxanide, of which two showed clear progression but one achieved a lasting stable disease. One patient was treated with mefloquine combination therapy in advanced disease, and overall, a positive treatment response could not be assessed. Furthermore, we report on one patient receiving pembrolizumab for a concomitant malignancy, which did not result in a reduction of echinococcal manifestation. In summary, current options of salvage therapy can sometimes induce persistent disease control, although with potentially significant side effects and high treatment costs, and mortality remains high. No clear recommendation for a salvage therapy can be given; treatment remains highly experimental, and non-pharmaceutical interventions have to be considered.

Fenbendazole Suppresses Growth and Induces Apoptosis of Actively Growing H4IIE Hepatocellular Carcinoma Cells via p21-Mediated Cell-Cycle Arrest

Bendimidazole anthelmintics (BAs) have gained interest for their anticancer activity. The anticancer activity is mediated via multiple intracellular changes, which are not consistent under different conditions even in the same cells. We investigated the anticancer activity of fenbendazole (FZ, one of BAs) under two different growth conditions. The growth rate of H4IIE cells was dose-dependently decreased by FZ only in actively growing cells but not in fully confluent quiescent cells. Apoptosis-associated changes were also induced by FZ in actively growing cells. Markers of autophagy were not changed by FZ. The number of cells was markedly increased in sub-G1 phase but decreased in S- and G2/M phases by FZ. FZ up-regulated p21 (an inhibitor of cyclin-CDK) but suppressed the expression of cell cycle-promoting proteins (cyclin D1 and cyclin B1). FZ did not affect integrin αV or n-cadherin expression as well as cell migration. Glycolytic changes (glucose consumption and lactate production) and the generation of reactive oxygen species (ROS) were not affected by FZ. Although the activity of mitogen-activated protein kinases (MAPKs) was altered by FZ, the inhibition of MAPKs did not affect the pro-apoptotic activity of FZ. Taken together, FZ selectively suppressed the growth of cells via p21-mediated cell cycle arrest at G1/S and G2/M, and resulted in apoptosis only in actively growing cells but not in quiescent cells. Glucose metabolism, ROS generation, and MAPKs are unlikely targets of FZ at least in H4IIE rat hepatocellular carcinoma cells used in this study.

Floating Ricobendazole Delivery Systems: A 3D Printing Method by Co-Extrusion of Sodium Alginate and Calcium Chloride

At present, the use of benzimidazole drugs in veterinary medicine is strongly limited by both pharmacokinetics and formulative issues. In this research, the possibility of applying an innovative semi-solid extrusion 3D printing process in a co-axial configuration was speculated, with the aim of producing a new gastro-retentive dosage form loaded with ricobendazole. To obtain the drug delivery system (DDS), the ionotropic gelation of alginate in combination with a divalent cation during the extrusion was exploited. Two feeds were optimized in accordance with the printing requirements and the drug chemical properties: the crosslinking ink, i.e., a water ethanol mixture containing CaCl₂ at two different ratios 0.05 M and 0.1 M, hydroxyethyl cellulose 2% w/v, Tween 85 0.1% v/v and Ricobendazole 5% w/v; and alginate ink, i.e., a sodium alginate solution at 6% w/v. The characterization of the dried DDS obtained from the extrusion of gels containing different amounts of calcium chloride showed a limited effect on the ink extrudability of the crosslinking agent, which on the contrary strongly influenced the final properties of the DDS, with a difference in the polymeric matrix toughness and resulting effects on floating time and drug release.

Coumarin-benzimidazole hybrids: A review of developments in medicinal chemistry

Coumarin and benzimidazole are privileged structures in medicinal chemistry and are widely used in drug discovery and development due to their vast biological properties. The pharmacokinetic and pharmacodynamic properties of the individual scaffolds can be improved by developing coumarin-benzimidazole chimeric molecules via molecular hybridization approach. The three major classes of coumarin-benzimidazole hybrids are merged, fused and spacer-linked hybrids. Depending on the substitution position, fused hybrids and spacer-linked hybrids can be further classified as coumarin-C3 hybrids, coumarin-C4 hybrids and coumarin-C5/6/7/8 hybrids. Most of the coumarin-benzimidazole hybrid molecules exhibited potent anticancer, antiviral, antimicrobial, antitubercular, anthelmintic, anti-inflammatory, antioxidant, anticonvulsant and carbonic anhydrase inhibitory activities. The fused coumarin-C3 hybrid (2), thiomethylene-linked coumarin-C3 hybrid (45), N-glucoside substituted thiomethylene-linked coumarin-C3 hybrid (37c), amide-linked coumarin-C3 hybrid (50a), and sulfonylmethylene-linked coumarin-C4 hybrid (63) were identified as the representative potent anticancer, antimicrobial, antiviral, antioxidant and antitubercular agents respectively. The biological properties of the different classes of coumarin-benzimidazole hybrids with their structure-activity relationship studies and the mechanism of action studies were presented in this review, aiming to help the researchers across the globe to generate future hybrid molecules as potential drug candidates.

Assessing the Efficacy of Albendazole against Fasciola hepatica in Naturally Infected Cattle by In Vivo and In Vitro Methods

This study was performed on a cattle farm with a long-term use of albendazole (ABZ) and a permanent history of fasciolosis for comparing in vivo and in vitro methods for the detection of anthelmintic resistance and drug efficacy. A selected group of 10 Charolais cows was treated in autumn 2020 with ABZ at a dose of 7.5 mg/kg body weight. Another group of 10 cows remained untreated as a control. The faecal egg count reduction test was used to determine in vivo efficacy. The percentage reduction of eggs on day 14 after treatment ranged from 77 to 81.8%, depending on the formula used for calculation. The in vitro egg hatch test (EHT) was used as a second diagnostic method. F. hepatica eggs for the EHT were isolated from faecal samples. The test was performed in two versions differing in the length of incubation with ABZ (12 h and 15 d). The percentage of eggs with inhibited development at a concentration of 0.5 μM in both versions of the EHT agreed with the in vivo results. Ovicidal activity at a concentration of 0.5 μM in the 12-h version suggested a reduced efficacy of ABZ (65.40%). An EHT prepared using pooled faecal samples was a prospective method for the detection of efficacy and ABZ resistance in F. hepatica.

Characterization of Microtubule Destabilizing Drugs: A Quantitative Cell-Based Assay That Bridges the Gap between Tubulin Based- and Cytotoxicity Assays

Simple Summary

The characterization of new microtubule depolymerizing agents relies mainly on purified tubulin assays in vitro and on cytotoxicity tests. However, the relationship between the in vitro effects of drugs and their effect on cell viability may not be direct. Here, we have systematically compared the effect of four reference drugs on tubulin polymerization in vitro and in cells, using a recently-developed quantitative assay of the cellular microtubule content. By comparing these results with cell viability assays, we found that this new cellular microtubule content test better predicts cellular drug toxicity than the in vitro tubulin polymerization assay. This test can thus be easily implemented in the process of discovery and characterization of novel microtubule poisons.

Abstract

(1) Background: Microtubule depolymerizing agents (MDAs) are commonly used for cancer treatment. However, the therapeutic use of such microtubule inhibitors is limited by their toxicity and the emergence of resistance. Thus, there is still a sustained effort to develop new MDAs. During the characterization of such agents, mainly through in vitro analyses using purified tubulin and cytotoxicity assays, quantitative comparisons are mandatory. The relationship between the effect of the drugs on purified tubulin and on cell viability are not always direct. (2) Methods: We have recently developed a cell-based assay that quantifies the cellular microtubule content. In this study, we have conducted a systematic comparative analysis of the effect of four well-characterized MDAs on the kinetics of in vitro tubulin assembly, on the cellular microtubule content (using our recently developed assay) and on cell viability. (3) Conclusions: These assays gave complementary results. Additionally, we found that the drugs’ effect on in vitro tubulin polymerization is not completely predictive of their relative cytotoxicity. Their effect on the cellular microtubule content, however, is closely related to their effect on cell viability. In conclusion, the assay we have recently developed can bridge the gap between in vitro tubulin assays and cell viability assays.

Bioaugmentation of animal feces as a mean to mitigate environmental contamination with anthelmintic benzimidazoles

Anthelmintics are used to control infestations of ruminants by gastrointestinal nematodes. The limited metabolism of anthelmintics in animals result in their excretion in feces. These could be piled up in the floor of livestock farms, constituting a point source of environmental contamination, or used as manures in agricultural soils where they persist or move to water bodies. Hence the removal of anthelmintics from feces could mitigate environmental contamination. We hypothesized that a thiabendazole-degrading bacterial consortium would also degrade other benzimidazole anthelmintics like albendazole, fenbendazole, ricobendazole, mebendazole and flubendazole. In liquid culture tests the consortium was more effective in degrading compounds with smaller benzimidazole substituents (thiabendazole, albendazole, ricobendazole), rather than benzimidazoles with bulky substituents (fenbendazole, flubendazole, mebendazole). We then explored the bioaugmentation capacity of the consortium in sheep feces fortified with 5 and 50 mg kg^-1 of thiabendazole, albendazole and fenbendazole. Bioaugmentation enhanced the degradation of all compounds and its efficiency was accelerated upon fumigation of feces, in the absence of the indigenous fecal microbial community. The latter contributes to anthelmintics degradation as suggested by the significantly lower DT₅₀ values in fumigated vs non-fumigated, non-bioaugmented feces. Overall, bioaugmentation could be an efficient means to reduce environmental exposure to recalcitrant anthelmintic benzimidazoles.

Population pharmacokinetic-pharmacodynamic model of oxfendazole in healthy adults in a multiple ascending dose and food effect study and target attainment analysis

Oxfendazole is a potent veterinary antiparasitic drug undergoing development for human use to treat multiple parasitic infections. Results from two recently completed Phase I clinical trials conducted in healthy adults showed that the pharmacokinetics of oxfendazole is nonlinear, affected by food, and, after the administration of repeated doses, appeared to mildly affect hemoglobin concentrations. To facilitate oxfendazole dose optimization for its use in patient populations, the relationship among oxfendazole dose, pharmacokinetics and hemoglobin concentration was quantitatively characterized using population pharmacokinetic-pharmacodynamic modeling. In fasting subjects, oxfendazole pharmacokinetics was well described by a one-compartment model with first-order absorption and elimination. The change in oxfendazole pharmacokinetics when administered following a fatty meal was captured by an absorption model with one transit compartment and increased bioavailability. The effect of oxfendazole exposure on hemoglobin concentration in healthy adults was characterized by a lifespan indirect response model in which oxfendazole has positive but minor inhibitory effect on red blood cell synthesis. Further simulation indicated that oxfendazole has a low risk of posing a safety concern regarding hemoglobin concentration, even at a high oxfendazole dose of 60 mg/kg once daily. The final model was further used to perform comprehensive target attainment simulations for whipworm infection and filariasis at various dose regimens and target attainment criteria. The results of our modeling work, when adopted appropriately, have the potential to greatly facilitate oxfendazole dose regimen optimization in patient populations with different types of parasitic infections.

The Pattern of Blood-Milk Exchange for Antiparasitic Drugs in Dairy Ruminants

Simple Summary

This review article is focused on the description of the plasma–milk partition coefficients for different antiparasitic drug classes in dairy ruminants, and it contributes to rational pharmaco-therapy in lactating dairy animals, which is critical to understand the pattern of drug excretion in milk as well as the residual concentration patterns in dairy products elaborated by processing milk from drug-treated animals.

Abstract

The prolonged persistence of milk residual concentration of different antiparasitic drugs in lactating dairy animals should be considered before recommending their use (label or extra-label) for parasite control in dairy animals. The partition blood-to-milk ratio for different antiparasitic compounds depends on their ability to diffuse across the mammary gland epithelium. The high lipophilicity of some of the most widely used antiparasitic drugs explains their high partition into milk and the extended persistence of high residual concentrations in milk after treatment. Most of the antiparasitic drug compounds studied were shown to be stable in various milk-related industrial processes. Thus, the levels of residues detected in raw milk can be directly applicable to estimating consumer exposure and dietary intake calculations when consuming heat-processed fluid milk. However, after milk is processed to obtain milk products such as cheese, yogurt, ricotta, and butter, the residues of lipophilic antiparasitic drugs are higher than those measured in the milk used for their elaboration. This review article contributes pharmacokinetics-based information, which is useful to understand the relevance of rational drug-based parasite control in lactating dairy ruminants to avoid undesirable consequences of residual drug concentrations in milk and derived products intended for human consumption.

Assessment of Diet-Related Changes on Albendazole Absorption, Systemic Exposure, and Pattern of Urinary Excretion in Treated Human Volunteers

Soil-transmitted-helminth (STH) infections are a persistent global public health problem. Control strategies for STH have been based on the use of mass drug administration (MDA) mainly targeting preschool- and school-aged-children, although there is increasing interest in expanding treatment to include adults and others through community-wide MDA. Coverage assessment is critical to understanding the real effectiveness of albendazole (ALB) treatment in those MDA programs. The work described here aims to (i) evaluate the effect of type of diet (a heavy or light meal) and fasting before ALB treatment on the systemic disposition of ALB and its metabolites in treated human volunteers and (ii) evaluate the potential feasibility of detecting albendazole metabolites in urine. The data reported here demonstrate that the systemic availability of the active ALB-sulfoxide (ALBSO) metabolite was enhanced more than 2-fold after food ingestion (a heavy or light meal). ALB dissolution improvement related to the ingestion of food may modify the amount of drug/metabolites reaching the parasite, affecting drug efficacy and the overall success of MDA strategies. The measurement in urine samples of the amino-ALB-sulfone (NHALBSO₂) derivative and ALBSO for up to 96 h suggests that it may be feasible to develop a noninvasive tool to evaluate compliance/adherence to ALB treatment.

Pharmacokinetic profile, tissue residue depletion and anthelmintic efficacy of supramolecular fenbendazole

A supramolecular complex of fenbendazole (SFBZ) with polyvinylpyrrolidone (PVP) was created by mechanochemical processing to increase its anthelmintic efficacy and to reduce the dose of applied drugs. The aim of our research was to study the pharmacokinetic profile and tissue residue depletion of fenbendazole (FBZ) and its metabolites: sulfoxide and sulfone in sheep after SFBZ treatment by high-performance liquid chromatography with tandem mass spectrometric detection and to evaluate its efficacy against gastrointestinal strongylatosis of sheep in field trials. The results revealed that FBZ and its metabolites were detected in blood serum in 2 h after SFBZ administration and in 4-6 h after the administration of the basic - FBZ. Pharmacokinetic parameters of SFBZ and its metabolites were characterized by higher rate of absorption, concentration of the drug and longer retention times in the blood serum. The maximum concentration of FBZ and its metabolites was detected on the 3rd day in the organs and tissues of sheep that received SFBZ. Thus, in the liver, the content of FBZ was 4878.0 ng/g, sulfoxide and sulfone - 18682.4 and 2483.6 ng/g respectively while the indicators of the basic FBZ and its metabolites were tenfold lower. FBZ and its metabolites were not detected in the organs and tissues of sheep on the 16th day in animals treated with the basic drug and on the 21st day after SFBZ administration. In field trials SFBZ demonstrated a high anthelmintic activity against nematodosis of sheep. It showed 98.2% efficacy against nematodirosis and 99.0 % against other types of gastrointestinal strongylatosis at a dose of 2 mg/kg of active substance (a.s.). Efficacy of mechanical mixture and efficacy of FBZ substance was in 3.1-3.4 times lower in the same dose.

In vivo exposure of Albendazole sulphoxide by Haemonchus contortus and correlation between plasma and target tissue or gastrointestinal content dispositions in goats

Sheep and goats are sharing different helminth parasites including Haemonchus contortus. Control of these helminths is based mainly on the use of anthelmintics. However, in goats, the application of anthelmintics is often carried out mainly at dosages determined for sheep without knowing the real effects and metabolism features. One of the several anthelmintic classes used against these parasites is (pro) benzimidazoles which are still widely in use in small ruminants in many countries. The objective of this study was to determine (i) the correlation between plasma and tissue or gastrointestinal content dispositions of ricobendazole (RBZ) in goats and (ii) the in vivo exposure of ricobendazole by H. contortus. Ten goats were experimentally infected with 10,000 larvae of H. contortus. Four weeks of post-infection, the animals received RBZ subcutaneously at 5 mg/kg body weight. Two goats were sacrificed per time at 1, 2, 4, 6 and 12 h after drug administration and, blood, bile, urine, liver, lung, muscle and kidney gastrointestinal tissues/fluids were collected. Adult H. contortus were collected from abomasum, and all samples were analysed by HPLC system. Ricobendazole (RBZ) and its sulphone metabolite were extensively excreted by urine and distributed to all tissues and digestive tract, mainly into the abomasum fluid. RBZ concentration in the lung and ABZSO₂ in the kidney were relatively higher than those of other tissues, respectively. The parent drug and its metabolite were recovered in both male and female H. contortus. This study indicates that in goats the plasma concentration profiles of RBZ are strongly correlated with those achieved in different target tissues or fluids, which in turn, reflect the amount of drug taken up by parasites.

Multi-omics phenotyping of the gut-liver axis reveals metabolic perturbations from a low-dose pesticide mixture in rats

Health effects of pesticides are not always accurately detected using the current battery of regulatory toxicity tests. We compared standard histopathology and serum biochemistry measures and multi-omics analyses in a subchronic toxicity test of a mixture of six pesticides frequently detected in foodstuffs (azoxystrobin, boscalid, chlorpyrifos, glyphosate, imidacloprid and thiabendazole) in Sprague-Dawley rats. Analysis of water and feed consumption, body weight, histopathology and serum biochemistry showed little effect. Contrastingly, serum and caecum metabolomics revealed that nicotinamide and tryptophan metabolism were affected, which suggested activation of an oxidative stress response. This was not reflected by gut microbial community composition changes evaluated by shotgun metagenomics. Transcriptomics of the liver showed that 257 genes had their expression changed. Gene functions affected included the regulation of response to steroid hormones and the activation of stress response pathways. Genome-wide DNA methylation analysis of the same liver samples showed that 4,255 CpG sites were differentially methylated. Overall, we demonstrated that in-depth molecular profiling in laboratory animals exposed to low concentrations of pesticides allows the detection of metabolic perturbations that would remain undetected by standard regulatory biochemical measures and which could thus improve the predictability of health risks from exposure to chemical pollutants.

Population Pharmacokinetic Model of Oxfendazole and Metabolites in Healthy Adults following Single Ascending Doses

Oxfendazole is a potent veterinary benzimidazole anthelmintic under transition to humans for the treatment of multiple parasitic infectious diseases. The first-in-human study evaluating the disposition of oxfendazole and its metabolites in healthy adults following single ascending oral doses from 0.5 to 60 mg/kg of body weight shows that oxfendazole pharmacokinetics is substantially nonlinear, which complicates correlating oxfendazole dose to exposure. To quantitatively capture the relation between oxfendazole dose and exposure, a population pharmacokinetic model for oxfendazole and its metabolites, oxfendazole sulfone and fenbendazole, in humans was developed using a nonlinear mixed-effect modeling approach. Our final model incorporated mechanistic characterization of dose-limited bioavailability as well as different oxfendazole metabolic processes and provided insight into the significance of presystemic metabolism in oxfendazole and metabolite disposition. Oxfendazole clinical pharmacokinetics was best described by a one-compartment model with nonlinear absorption and linear elimination. Oxfendazole apparent clearance and apparent volume of distribution were estimated to be 2.57 liters/h and 35.2 liters, respectively, at the lowest dose (0.5 mg/kg), indicating that oxfendazole is a low extraction drug with moderate distribution. The disposition of both metabolites was adequately characterized by a one-compartment model with formation rate-limited elimination. Fenbendazole formation from oxfendazole was primarily through systemic metabolism, while both presystemic and systemic metabolism were critical to the formation of oxfendazole sulfone. Our model adequately captured the concentration-time profiles of both oxfendazole and its two metabolites in healthy adults over a wide dose range. The model can be used to predict oxfendazole disposition under new dosing regimens to support dose optimization in humans.

Advances in the discovery and development of anthelmintics by harnessing natural product scaffolds

Widespread resistance to currently-used anthelmintics represents a major obstacle to controlling parasitic nematodes of livestock animals. Given the reliance on anthelmintics in many control regimens, there is a need for the continued discovery and development of new nematocides. Enabling such a focus are: (i) the major chemical diversity of natural products; (ii) the availability of curated, drug-like extract-, fraction- and/or compound-libraries from natural sources; (iii) the utility and practicality of well-established whole-worm bioassays for Haemonchus contortus-an important parasitic nematodes of livestock-to screen natural product libraries; and (iv) the availability of advanced chromatographic (HPLC), spectroscopic (NMR) and spectrometric (MS) techniques for bioassay-guided fractionation and structural elucidation. This context provides a sound basis for the identification and characterisation of anthelmintic candidates from natural sources. This chapter provides a background on the importance and impact of helminth infections/diseases, parasite control and aspects of drug discovery, and reviews recent work focused on (i) screening well-defined compound libraries to establish the methods needed for large-scale screening of natural extract libraries; (ii) discovering plant and marine extracts with nematocidal or nematostatic activity, and purifying bioactive compounds and assessing their potential for further development; and (iii) synthesising analogues of selected purified natural compounds for the identification of possible 'lead' candidates. The chapter describes some lessons learned from this work and proposes future areas of focus for drug discovery. Collectively, the findings from this recent work show potential for selected natural product scaffolds as candidates for future development. Developing such candidates via future chemical optimisation, efficacy and safety evaluations, broad spectrum activity assessments, and target identification represents an exciting prospect and, if successful, could pave the way to subsequent pre-clinical and clinical evaluations.

Treatment strategies for cryptococcal infection: challenges, advances and future outlook

Cryptococcus spp., in particular Cryptococcus neoformans and Cryptococcus gattii, have an enormous impact on human health worldwide. The global burden of cryptococcal meningitis is almost a quarter of a million cases and 181,000 deaths annually, with mortality rates of 100% if infections remain untreated. Despite these alarming statistics, treatment options for cryptococcosis remain limited, with only three major classes of drugs approved for clinical use. Exacerbating the public health burden is the fact that the only new class of antifungal drugs developed in decades, the echinocandins, displays negligible antifungal activity against Cryptococcus spp., and the efficacy of the remaining therapeutics is hampered by host toxicity and pathogen resistance. Here, we describe the current arsenal of antifungal agents and the treatment strategies employed to manage cryptococcal disease. We further elaborate on the recent advances in our understanding of the intrinsic and adaptive resistance mechanisms that are utilized by Cryptococcus spp. to evade therapeutic treatments. Finally, we review potential therapeutic strategies, including combination therapy, the targeting of virulence traits, impairing stress response pathways and modulating host immunity, to effectively treat infections caused by Cryptococcus spp. Overall, understanding of the mechanisms that regulate anti-cryptococcal drug resistance, coupled with advances in genomics technologies and high-throughput screening methodologies, will catalyse innovation and accelerate antifungal drug discovery.

Nanocrystals of Novel Valerolactam-Fenbendazole Hybrid with Improved in vitro Dissolution Performance

Valero-fenbendazole (VAL-FBZ) is a novel hybrid compound with in vitro anthelmintic activity, designed and synthesized to address the global problem of resistance to anthelmintic compounds. This new molecule derives from fenbendazole (FBZ), a well-known commercially available benzimidazole used in veterinary medicine despite its poor water solubility. In this work, we report for the first time a strategy to solve the solubility problems of FBZ and VAL-FBZ by means of self-dispersible nanocrystals (SDNC). Nanocrystals were prepared by media milling followed by a spray-drying step, and a comprehensive and exhaustive structural and physicochemical characterization was carried out, in order to understand the systems and their behavior. The formulation poloxamer 188 (P188):FBZ 1:1 turned out with the best process yield (53%) and re-dispersability properties, particle size average of 258 nm, and polydispersity index of 0.2 after redispersion in water. The dissolution profile showed a markedly increased dissolution rate compared with the simple mixture of the components (80% FBZ dissolved in 15 min from the SDNC vs 14% from the control formulation). FTIR spectroscopy, thermal analysis, and X-Ray Powder Diffraction (XRPD) studies showed no chemical interactions between components and an extensive confocal Raman microscopy analysis of the formulations showed very homogeneous spatial distribution of components in the SDNC samples. This manufacturing process was then successfully transferred for preparing and characterizing VAL-FBZ:P188 (1:1) SDNC with similar results, suggesting the promising interest of a novel anthelmintic with improved biopharmaceutical behavior. In conclusion, new FBZ and VAL-FBZ SDNC with improved dissolution rate were successfully prepared and characterized. Graphical abstract.

Alvaxanthone, a Thymidylate Synthase Inhibitor with Nematocidal and Tumoricidal Activities

With the aim to identify novel inhibitors of parasitic nematode thymidylate synthase (TS), we screened in silico an in-house library of natural compounds, taking advantage of a model of nematode TS three-dimensional (3D) structure and choosing candidate compounds potentially capable of enzyme binding/inhibition. Selected compounds were tested as (i) inhibitors of the reaction catalyzed by TSs of different species, (ii) agents toxic to a nematode parasite model (C. elegans grown in vitro), (iii) inhibitors of normal human cell growth, and (iv) antitumor agents affecting human tumor cells grown in vitro. The results pointed to alvaxanthone as a relatively strong TS inhibitor that causes C. elegans population growth reduction with nematocidal potency similar to the anthelmintic drug mebendazole. Alvaxanthone also demonstrated an antiproliferative effect in tumor cells, associated with a selective toxicity against mitochondria observed in cancer cells compared to normal cells.

Ricobendazole nanocrystals obtained by media milling and spray drying: Pharmacokinetic comparison with the micronized form of the drug

Helminthic infections are produced by different types of worms and affect millions of people worldwide. Benzimidazole compounds such as ricobendazole (RBZ) are widely used to treat helminthiasis. However, their low aqueous solubility leads to poor gastrointestinal dissolution, absorption and potential lack of efficacy. The formulation of nanocrystals (NCs) have become the strategy of preference for hydrophobic drugs. In this work, we prepared RBZ NCs (RBZ-NCs) by an optimized combination of bead milling and spray-drying. Following the physicochemical characterization, a comparative pharmacokinetic evaluation of RBZ-NCs was performed in dogs using as controls a micronized powdered form of RBZ (mRBZ) and a physical mixture of drug and stabilizer 1:1 (PM). The particle size of the redispersed RBZ-NCs was 181.30 ± 5.93 nm, whereas DSC, PXRD and FTIR analyses demonstrated that the active ingredient RBZ remained physicochemically unchanged after the manufacture process. RBZ-NCs exhibited improved in vitro biopharmaceutical behaviour when compared to mRBZ. Consequently, the pharmacokinetic trial demonstrated a significant increase in the drug oral absorption, with an AUC_0-∞ 1.9-fold higher in comparison to that obtained in animals treated with mRBZ. This novel formulation holds substantial potential for the development of new/alternative treatments for helminth infections both in human and veterinary medicine.

Anthelmintic Efficacy and Pharmacokinetics of Ivermectin Paste after Oral Administration in Mules Infected by Cyathostomins

Ivermectin (IVM) is an anthelmintic compound commonly used off-label in mules due to its broad-spectrum of activity. Despite the general use of IVM in mules with the same dose and route of administration licensed for horses, significant pharmacokinetic differences might exist between horses and mules, as already observed for donkeys. The aim of the present study was to evaluate the pharmacokinetic profile and anthelmintic efficacy of an oral paste of IVM in mules naturally infected with cyathostomins. Fifteen adult mules with fecal egg counts (FEC) ≥200 eggs per gram (EPG), with exclusive presence of cyathostomins, were included in the study. All mules were orally treated with IVM according to the manufacturer's recommended horse dosage (200 µg/kg body weight). FECs were performed before (day-10 and day-3) and after treatment at days 14 and 28 by using a modified McMaster method. The FEC reduction (FECR%) was also calculated. Blood samples were collected from five animals at various times between 0.5 h up to 30 days post treatment to determine pharmacokinetic parameters. The maximum IVM serum concentration (Cmax) was 42.31 ± 10.20 ng/mL and was achieved at 16.80 ± 9.96 hours post-treatment (Tmax), area under the curve (AUC) was 135.56 ± 43.71 ng × day/mL. FECR% remained high (>95%) until the 28th day.