Evaluation of the safety of fenbendazole in cats

[Feline and canine giardiosis: An Update]

Giardia duodenalis is a facultative pathogenic intestinal parasite. Giardiosis in dogs and cats may appear with or without clinical signs. Typical signs include diarrhea with or without vomiting. The prevalence in young animals is high and may amount to up to 50%. There are 8 different genotypes (A - H), which are called assemblages. Assemblages C and D are most common in dogs and assemblage F most frequent in cats. However, animals may also be infected with the zoonotically effective assemblages A and B or exhibit mixed infections. The immunofluorescence test (IFA), the enzyme-linked immunosorbent assay (ELISA) and fecal centrifugation using zinc sulphate solution are currently recommended as diagnostic methods. Polymerase chain reaction (PCR) may be used to determine the corresponding assemblage. Approved treatments for giardiosis include fenbendazole and metronidazole. In addition, undertaking specific hygiene measures is warranted. Only animals showing clinical signs or those living in the same household with high-risk patients (e. g. immunosuppressed humans) are recommended to receive medication. The aim of treatment is clinical improvement of the diseased dogs and cats. Frequently, complete elimination of Giardia is not attained.

Fenbendazole Exhibits Differential Anticancer Effects In Vitro and In Vivo in Models of Mouse Lymphoma

Fenbendazole (FBZ) has been safely used as an antiparasitic agent in animals for decades, and the anticancer effects of FBZ have been studied through various mechanisms. However, there is a lack of in vivo studies that include lymphoma. Therefore, this study examined the effects of FBZ on EL-4 cells and a mouse T lymphoma model. FBZ induced G2/M phase arrest in EL-4 cells, resulting in cell death and decreased metabolic activity. However, FBZ had no anticancer effects on an EL-4 mouse lymphoma model in vivo, as evident by rapid weight loss and tumor growth comparable to the control. The FBZ-treated EL-4 cells expressed higher levels of PD-L1 and CD86, which are associated with T cell immunity in the tumor microenvironment (TME), than the controls. Furthermore, the hematoxylin and eosin staining of the FBZ-treated tumor tissues showed a starry sky pattern, which is seen in actively proliferating cancer tissues, and an immunohistochemical analysis revealed a high percentage of immunosuppressive M2 macrophages. These changes in the immune activity in the TME contradict the results of the in vitro experiments, and further studies are needed to determine the detailed mechanisms by which FBZ induces these responses.

Anticancer Evaluation of Methoxy Poly(Ethylene Glycol)-b-Poly(Caprolactone) Polymeric Micelles Encapsulating Fenbendazole and Rapamycin in Ovarian Cancer

Purpose

We aimed to inhibit ovarian cancer (OC) development by interfering with microtubule polymerization and inhibiting mTOR signaling. To achieve this, previously developed micelles containing fenbendazole and rapamycin were applied.

Methods

Herein, we prepared micelles for drug delivery using fenbendazole and rapamycin at a 1:2 molar ratio and methoxy poly(ethylene glycol)-b-poly(caprolactone)(mPEG-b-PCL) via freeze-drying. We revealed their long-term storage capacity of up to 120 days. Furthermore, a cytotoxicity test was performed on the OC cell line HeyA8, and an orthotopic model was established for evaluating in vivo antitumor efficacy.

Results

Fenbendazole/rapamycin-loaded mPEG-b-PCL micelle (M-FR) had an average particle size of 37.2 ± 1.10 nm, a zeta potential of -0.07 ± 0.09 mV, and a polydispersity index of 0.20 ± 0.02. Additionally, the average encapsulation efficiency of fenbendazole was 75.7 ± 4.61% and that of rapamycin was 98.0 ± 1.97%. In the clonogenic assay, M-FR was 6.9 times more effective than that free fenbendazole/rapamycin. The in vitro drug release profile showed slower release in the combination formulation than in the single formulation.

Conclusion

There was no toxicity, and tumor growth was suppressed substantially by our formulation compared with that seen with the control. The findings of our study lay a foundation for using fenbendazole and rapamycin for OC treatment.

Structural features, dissolution performance and anthelmintic efficacy of multicomponent solid forms of fenbendazole with maleic and oxalic acids

Two new multicomponent crystalline phases of fenbendazole (FNB), a benzimidazole anthelmintic agent, with maleic and oxalic acids have been prepared, and their structural and physicochemical properties carefully investigated.

Exceptional Repositioning of Dog Dewormer: Fenbendazole Fever

Fenbendazole (FZ) is a benzimidazole carbamate drug with broad-spectrum antiparasitic activity in humans and animals. The mechanism of action of FZ is associated with microtubular polymerization inhibition and glucose uptake blockade resulting in reduced glycogen stores and decreased ATP formation in the adult stages of susceptible parasites. A completely cured case of lung cancer became known globally and greatly influenced the cancer community in South Korea. Desperate Korean patients with cancer began self-administering FZ without their physician’s knowledge, which interfered with the outcome of the cancer treatment planned by their oncologists. On the basis of presented evidence, this review provides valuable information from PubMed, Naver, Google Scholar, and Social Network Services (SNS) on the effects of FZ in a broad range of preclinical studies on cancer. In addition, we suggest investigating the self-administration of products, including supplements, herbs, or bioactive compounds, by patients to circumvent waiting for long and costly FZ clinical trials.

Untargeted metabolomics-assisted comparative cytochrome P450-dependent metabolism of fenbendazole in human and dog liver microsomes

Fenbendazole (FBZ), a benzimidazole carbamate anthelmintic, has attracted attention for its antitumor activity. This study examined the metabolic characteristics of FBZ in humans compared with those in dogs. The phase I metabolites were identified in liver microsomal incubates using liquid chromatography-mass spectrometry (MS)-based untargeted metabolomics approaches. Seven metabolites of FBZ were identified by principal component analysis and orthogonal partial least square-discriminant analysis based on the global ion variables of the FBZ incubation groups. The chemical structure of the FBZ metabolites was suggested by examining the MS/MS spectrum and isotope distribution pattern. Cytochrome P450 (CYP) 1A1, CYP2D6, and CYP2J2 were the major isozymes responsible for the FBZ metabolism. No differences in the types of metabolites produced by the two species were noted. Multivariate analysis of human and dog incubation groups showed that five metabolites were relatively abundant in humans and the other two were not. In summary, the phase I metabolic profile of FBZ and the comparative metabolism between humans and dogs were examined using an untargeted metabolomics approach. This study suggests a successful investigation of FBZ metabolism in humans for conducting safety assessments regarding drug repositioning.

The characteristics of Raman spectroscopy of fenbendazole-gold nanoparticles based on the chemical adsorption effect

Fenbendazole, a benzimidazole derivative with anti-tubulin polymerization properties, has been widely used in the treatment of parasitic infections. Because of its anticancer activity similar to that of many anticancer drugs, low cost and few side effects, fenbendazole has attracted wide research attention. The chemical adsorption of fenbendazole and gold nanoparticles are studied by the UV-Vis spectrophotometry, density functional method, Raman spectroscopy and surface-enhanced Raman spectroscopy. By comparing and analyzing the theoretical and experimental Raman spectra, this paper explains the reasons for the difference between the theoretical and experimental Raman spectra. Meanwhile, it is also found that the frequencies at 851 cm^-1, 1222 cm^-1, 1425 cm^-1 and 1566 cm^-1 are greatly enhanced. It is found that imidazole is adsorbed vertically to the surface of the substrate. It is concluded that Fenbendazole is vertically adsorbed on the surface of AuNPs through imidazole.

Optimization and Pharmacokinetic Evaluation of Synergistic Fenbendazole and Rapamycin Co-Encapsulated in Methoxy Poly(Ethylene Glycol)-b-Poly(Caprolactone) Polymeric Micelles

Purpose

We aimed to develop a nanocarrier formulation incorporating fenbendazole (FEN) and rapamycin (RAPA) with strong efficacy against A549 cancer cells. As FEN and RAPA are poorly soluble in water, it is difficult to apply them clinically in vivo. Therefore, we attempted to resolve this problem by encapsulating these drugs in polymeric micelles.

Methods

We evaluated drug synergy using the combination index (CI) values of various molar ratios of FEN and RAPA. We formed and tested micelles composed of different polymers. Moreover, we conducted cytotoxicity, stability, release, pharmacokinetic, and biodistribution studies to investigate the antitumor effects of FEN/RAPA-loaded mPEG-b-PCL micelles.

Results

We selected mPEG-b-PCL-containing FEN and RAPA at a molar ratio of 1:2 because these particles were consistent in size and had high encapsulation efficiency (EE, %) and drug loading (DL, %) capacity. The in vitro cytotoxicity was assessed for various FEN, RAPA, and combined FEN/RAPA formulations. After long-term exposures, both the solutions and the micelles had similar efficacy against A549 cancer cells. The in vivo pharmacokinetic study revealed that FEN/RAPA-loaded mPEG-b-PCL micelles had a relatively higher area under the plasma concentration–time curve from 0 to 2 h (AUC_{0–2 h}) and 0 to 8 h (AUC_{0–8 h}) and plasma concentration at time zero (C_o) than that of the FEN/RAPA solution. The in vivo biodistribution assay revealed that the IV injection of FEN/RAPA-loaded mPEG-b-PCL micelles resulted in lower pulmonary FEN concentration than the IV injection of the FEN/RAPA solution.

Conclusion

When FEN and RAPA had a 1:2 molar ratio, they showed synergism. Additionally, using data from in vitro cytotoxicity, synergism between a 1:2 molar ratio of FEN and RAPA was observed in the micelle formulation. The FEN/RAPA-loaded mPEG-b-PCL micelle had enhanced bioavailability than the FEN/RAPA solution.

Fenbendazole acts as a moderate microtubule destabilizing agent and causes cancer cell death by modulating multiple cellular pathways

Drugs that are already clinically approved or experimentally tested for conditions other than cancer, but are found to possess previously unrecognized cytotoxicity towards malignant cells, may serve as fitting anti-cancer candidates. Methyl N-(6-phenylsulfanyl-1H benzimidazol-2-yl) carbamate [Fenbendazole, FZ], a benzimidazole compound, is a safe and inexpensive anthelmintic drug possessing an efficient anti-proliferative activity. In our earlier work, we reported a potent growth-inhibitory activity of FZ caused partially by impairment of proteasomal function. Here, we show that FZ demonstrates moderate affinity for mammalian tubulin and exerts cytotoxicity to human cancer cells at micromolar concentrations. Simultaneously, it caused mitochondrial translocation of p53 and effectively inhibited glucose uptake, expression of GLUT transporters as well as hexokinase (HK II) - a key glycolytic enzyme that most cancer cells thrive on. It blocked the growth of human xenografts in nu/nu mice model when mice were fed with the drug orally. The results, in conjunction with our earlier data, suggest that FZ is a new microtubule interfering agent that displays anti-neoplastic activity and may be evaluated as a potential therapeutic agent because of its effect on multiple cellular pathways leading to effective elimination of cancer cells.

Techniques for Monitoring Drug Efficacy

The efficacy of drugs can vary greatly between species and individuals. Establishing efficacious drug doses for a species requires integration of population pharmacokinetic and pharmacodynamic data into a dose-response curve. Unfortunately, these data sets are rarely available for exotic species. The use of alternative monitoring techniques is required to determine drug efficacy and safety. This article discusses methods to integrate efficacy monitoring into clinical practice, including the use of diagnostic testing and therapeutic drug monitoring.

Efficacy of a combination of febantel, pyrantel, and praziquantel for the treatment of kittens experimentally infected with Giardia species

This study evaluated the effect of two combination products containing febantel, pyrantel, and praziquantel (FPP) for the treatment of Giardia species in experimentally infected kittens. In experiment 1, five kittens were administered the United States (US) formulation of FPP at doses of 37.8 mg/kg, 7.56 mg/kg, and 7.56 mg/kg, respectively, PO, q24h, for 5 days and four kittens remained as controls. In experiment 2, five kittens were administered the European formulation of FPP at the doses of 12.5 mg/kg, 12 mg/kg, and 4.16 mg/kg, respectively, PO, q24h, for 5 days and four kittens remained as controls. In experiment 3, six kittens were administered the US formulation of FPP at 56.5 mg/kg, 11.3 mg/kg, 11.3 mg/kg, respectively, PO, q24h, for 5 days and five kittens remained as controls. Thirteen days after treatment, kittens testing negative for Giardia species cysts were administered 20 mg/kg methylprednisolone acetate, IM, weekly for a maximum of two injections. Feces were analyzed for Giardia species cysts using a direct immunofluorescence test. After experiment 3, four of the six treated kittens, but no control kittens, remained negative for Giardia species after the administration of methylprednisolone acetate.

Thrombo-ischaemic pinnal necrosis associated with fenbendazole treatment in a dog

An 11-week-old, female West Highland white terrier was presented with necrosis of the distal third of both pinnae. Haematology, biochemistry and urinalysis, Coombs test, antinuclear antibody and cold autoagglutinin antibody tests were normal. A drug reaction to fenbendazole was diagnosed. The necrotic ear tips were surgically removed. Histopathology revealed extensive coagulative necrosis of the epidermis and superficial to mid-dermis, a moderate interstitial neutrophilic infiltrate and complete thrombotic occlusion and necrosis of blood vessels. There was also endothelial cell activation and proliferation with endothelial cell cushions protruding into the vascular lumen. Immunohistochemistry for factor VIII-related antigen confirmed endothelial cell involvement. This case represents an unusual, drug-induced, thrombo-ischaemic necrosis of the pinnae. It is also, to the authors' knowledge, the first report of fenbendazole sensitivity in a dog. The histopathology is similar to previous cases of proliferative thrombovascular pinnal necrosis, suggesting that drug reactions should be considered in this condition.

Veterinary pharmacovigilance. Part 6. Predictability of adverse reactions in animals from laboratory toxicology studies

Toxicological studies are conducted on constituents of veterinary medicinal products for a number of reasons. Aside from being a requirement of legislation, they are carried out for predictive purposes in the assessment of user safety or for the determination of consumer safety, for example, in the elaboration of maximum residue limits or tolerances. Alternatively, the results of toxicology studies may be available as they have been generated for registration of the drug for human medicinal purposes. This paper examines if the results of such studies have any predictive value for adverse reactions, which might occur during clinical use in animals. A number of adverse reactions, notably the Type A (toxicology or pharmacology dependent) should be predictable from these laboratory studies. However, as with human pharmaceutical products, they have less utility in predicting Type-B reactions (idiosyncratic in nature).

Metronidazole for the treatment of feline giardiasis

There are several drugs available for the treatment of giardiasis in cats, including metronidazole. The purpose of this study was to determine whether metronidazole benzoate administered at a dose of 25 mg/kg, orally, twice a day for 7 days lessens or eliminates Giardia cyst shedding in cats with chronic infection. Twenty-six, adult, laboratory-reared cats were used in this study. Sixteen cats had been inoculated orally with cysts of a human Giardia sp. isolate and had completed a Giardia vaccine study in one animal holding room. The other ten cats were infected with the same Giardia sp. presumably by contamination from the adjacent room where the Giardia vaccine study cats were located. From each cat, a fecal sample was collected within 1 week of the start of treatment and then every 2 to 4 days for 15 days after treatment was completed. Fecal samples were analyzed for the presence of Giardia cysts using a commercially available direct immunofluorescence test (IFA). Clinical signs of drug toxicity were not detected during the study.