Concurrent use of two dual-combination drenches containing monepantel/abamectin and oxfendazole/levamisole in sheep: effect on marker residues 21 and 28 days after administration

AIMS

To determine the concentration, in comparison with the maximum residue limit (MRL), of anthelmintic marker residues in the target tissues (liver and fat) of sheep treated concurrently with two oral drenches, one containing monepantel and abamectin and the other oxfendazole and levamisole.

METHODS

On day 0 of the study, 12 sheep (six male and six female; 8-9-months old) were dosed according to individual body weight determined the day prior. Zolvix Plus (dual-active oral drench containing 25 g/L monepantel and 2 g/L abamectin) was administered to all animals prior to administration of Scanda (dual-active oral drench containing 80 g/L levamisole hydrochloride and 45.3 g/L oxfendazole). Six sheep (three male and three female) were slaughtered 21 and 28 days after treatment and renal fat and liver samples were collected.Using validated methods, analyses for monepantel sulfone, abamectin, levamisole and oxfendazole (expressed as total fenbendazole sulfone following conversion of the combined concentrations of oxfendazole, fenbendazole and fenbendazole sulfone) were performed on liver samples while renal fat specimens were analysed for monepantel sulfone and abamectin residues only. Detected concentrations were compared to the established MRL in sheep for each analyte determined by the Ministry for Primary Industries.

RESULTS

All residues detected in samples of liver and fat collected 21 and 28 days after treatment were below the MRL for each analyte. All liver samples collected on day 21 had detectable monepantel sulfone (mean 232 (min 110, max 388) μg/kg) and oxfendazole (mean 98.7 (min 51.3, max 165) μg/kg) residues below the MRL (5,000 and 500 μg/kg, respectively). Monepantel sulfone (mean 644 (min 242, max 1,119) μg/kg; MRL 7,000 μg/kg) residues were detected in 6/6 renal fat samples. Levamisole residues were detected in 3/6 livers (mean 40.0 (min 14.3, max 78.3) μg/kg; MRL 100 μg/kg), and abamectin residues in 1/6 livers (0.795 μg/kg; MRL 25 μg/kg) and 2/6 fat samples, (mean 0.987 (min 0.514, max 1.46) μg/kg; MRL 50 μg/kg) 21 days after treatment.

CONCLUSION AND CLINICAL RELEVANCE

These results suggest that concurrent administration of Zolvix Plus and Scanda to sheep is unlikely to result in an extended residue profile for any of the active ingredients, with all analytes measured being under the approved New Zealand MRL 21 days after treatment. This work was not completed in line with guidance for establishing official residue profiles, nor is it sufficient to propose a new withholding period.

A novel treatment to enhance survival for end stage triple negative breast cancer using repurposed veterinary anthelmintics combined with gut‑supporting/immune enhancing molecules

Patients with end‑stage metastatic disease have limited treatment options and those diagnosed with triple negative breast cancer (Her2, Estrogen receptor, Progesterone receptor) have a poor prognosis. Using a triple negative mammary tumor model selected for brain metastasis (4T1Br4) in the mouse, treatment options that may increase survival when therapeutics are applied at post‑metastasis were assessed. Anti‑parasitic benzimidazoles (BZs) destabilize microtubules, inhibit metabolic pathways, reduce cell proliferation, and induce apoptosis in tumor cells. Co‑administration of two BZs was selected, oxfendazole (OFZ) and parbendazole (PBZ), shown to overcome resistance development in anthelmintic effects by imposing metabolic delay to assess if multiple BZ approach is also suitable to enhance anticancer effects. It has been previously reported that treatment of mammary tumor‑bearing mice at an early stage with chitin microparticles (CMPs) decreased tumor growth and metastases by enhancing both innate M1 macrophage and TH1 adaptive immune response. Oral administration of CMPs was previously revealed to affect the gut in intestinal inflammation. A combination BZ (OFZ/PBZ) and CMP treatment was tested to target tumor development and metastasis and effects were compared in response to monotherapies of the same compounds or to untreated mice. The results demonstrated increased survival, decreased tumor cell proliferation, decreased metastasis in lungs and brain, increased levels of fecal SCFAs butyric, acetic, propionic and valeric acids with increased butyric and propionic acid levels in brain biopsies in combination treated compared with untreated mice. At the primary tumor, SCFA receptor FFAR2 expression was increased in combination treatment compared with untreated mice, suggestive of a non‑invasive cancer phenotype. The superior cytotoxic effects of OFZ/PBZ were confirmed as opposed to single treatment with OFZ or PBZ using 3D spheroids generated from a human breast cancer cell line, MDA‑MB‑468. These data are compelling for treatment option possibility even at late stages of metastasized breast cancer.

The efficacy of the benzimidazoles oxfendazole and flubendazole against Litomosoides sigmodontis is dependent on the adaptive and innate immune system

Filarial nematodes can cause debilitating diseases such as lymphatic filariasis and onchocerciasis. Oxfendazole (OXF) is one promising macrofilaricidal candidate with improved oral availability compared to flubendazole (FBZ), and OXF is currently under preparation for phase 2 clinical trials in filariasis patients. This study aimed to investigate the immune system's role during treatment with OXF and FBZ and explore the potential to boost the treatment efficacy via stimulation of the immune system. Wild type (WT) BALB/c, eosinophil-deficient ΔdblGata1, IL-4r/IL-5^-/-, antibody-deficient μMT and B-, T-, NK-cell and ILC-deficient Rag2/IL-2rγ^-/- mice were infected with the rodent filaria Litomosoides sigmodontis and treated with an optimal and suboptimal regimen of OXF and FBZ for up to 5 days. In the second part, WT mice were treated for 2-3 days with a combination of OXF and IL-4, IL-5, or IL-33. Treatment of WT mice reduced the adult worm burden by up to 94% (OXF) and 100% (FBZ) compared to vehicle controls. In contrast, treatment efficacy was lower in all immunodeficient strains with a reduction of up to 90% (OXF) and 75% (FBZ) for ΔdblGata1, 50 and 92% for IL-4r/IL-5^-/-, 64 and 78% for μMT or 0% for Rag2/IL-2rγ^-/- mice. The effect of OXF on microfilariae and embryogenesis displayed a similar pattern, while FBZ's ability to prevent microfilaremia was independent of the host's immune status. Furthermore, flow cytometric analysis revealed strain-and treatment-specific immunological changes. The efficacy of a shortened 3-day treatment of OXF (-33% adult worms vs. vehicle) could be boosted to a 91% worm burden reduction via combination with IL-5, but not IL-4 or IL-33. Our results suggest that various components of the immune system support the filaricidal effect of benzimidazoles in vivo and present an opportunity to boost treatment efficacy.

Oxfendazole Induces Apoptosis in Ovarian Cancer Cells by Activating JNK/MAPK Pathway and Inducing Reactive Oxygen Species Generation

Ovarian cancer (OC) is one of the most common and high mortality type of cancer among women worldwide. The majority of patients with OC respond to chemotherapy initially; however, most of them become resistant to chemotherapy and results in a high level of treatment failure in OC. Therefore, novel agents for the treatment of OC are urgently required. Benzimidazole anthelmintics might have the promising efficacy for cancer therapy as their selectively binding activity to β-tubulin. Recent study has shown that one of the benzimidazole anthelmintics oxfendazole inhibited cell growth of non-small cell lung cancer cells, revealing its anti-cancer activity; however, the pharmacological action and detailed mechanism underlying the effects of oxfendazole on OC cells remain unclear. Therefore, the present study investigated the cytotoxic effects of oxfendazole on OC cells. Our results demonstrated that oxfendazole significantly decreased the viability of OC cells. Oxfendazole inhibited the proliferation, induced G2/M phase arrest and apoptotic cell death in A2780 cells. The c-Jun N-terminal kinase (JNK)/mitogen-activated protein kinase (MAPK) pathway was activated and reactive oxygen species (ROS) generation was increased in OC cells treated with oxfendazole; oxfendazole-induced apoptosis was notably abrogated when co-treated with JNK inhibitor SP600125 and ROS scavenger N-acetyl-L-cysteine (NAC), indicating that JNK/MAPK pathway activation and ROS accumulation was associated with the oxfendazole-induced apoptosis of OC cells. Moreover, oxfendazole could also induce the proliferation inhibition and apoptosis of cisplatin resistant cells. Collectively, these results revealed that oxfendazole may serve as a potential therapeutic agent for the treatment of OC.

Pharmacokinetics and pharmacokinetic interactions of orally administered oxfendazole and oxyclozanide tablet formulation to sheep

The combination of oxfendazole and oxyclozanide is used to provide activity against fluke and gastrointestinal nematodes. This study aimed to determine both the pharmacokinetics of oxfendazole (7.5 mg/kg) and oxyclozanide (15 mg/kg) tablet formulation administered orally to sheep and whether there is a pharmacokinetic interaction between these two drugs. The study was conducted in a three-period, crossover pharmacokinetic design and on six healthy Awassi sheep 1-3 years of age. The plasma concentrations of oxfendazole and its metabolites (fenbendazole and fenbendazole sulphone) and oxyclozanide were determined by high-performance liquid chromatography using an ultraviolet detector. Compounds recovered in plasma when oxfendazole was administered alone or combined with oxyclozanide were oxfendazole, fenbendazole sulphone, and fenbendazole, respectively. When oxfendazole was administered alone and co-administered with oxyclozanide, the AUC_FBZ /AUC_OFZ was 0.26 and 0.23, respectively, and the AUC_FBZSO2 /AUC_OFZ was 0.35 and 0.32, respectively. The volume of distribution (Vz/F) of oxfendazole was large in both groups. Oxyclozanide did not change the plasma disposition of oxfendazole. When the oxyclozanide tablet formulation was administered alone, the elimination half-life (21.35 h) and the Vz/F (940.17 ml/kg) were long and large, respectively. The area under the curve (AUC) and the maximum plasma concentration of oxyclozanide were significantly larger and higher, respectively, in the oxyclozanide plus oxfendazole group (1146.61 h × μg/ml and 29.80 μg/ml) compared with the oxyclozanide group (491.44 h × μg/ml and 14.24 μg/ml) while a significant decrease in apparent Vz/F (940.17 vs 379.14 ml/kg) and total clearance (30.52 vs 13.08 ml/h/kg) was detected. In conclusion, co-administration with oxfendazole causing an increase in the plasma profile of oxyclozanide may increase the antiparasitic activity of oxyclozanide.

Current perspective of new anti-Wolbachial and direct-acting macrofilaricidal drugs as treatment strategies for human filariasis

Filarial diseases like lymphatic filariasis and onchocerciasis belong to the Neglected Tropical Diseases and remain a public health problem in endemic countries. Lymphatic filariasis and onchocerciasis can lead to stigmatizing pathologies and present a socio-economic burden for affected people and their endemic countries. Current treatment recommendations by the WHO include mass drug administration with ivermectin for the treatment of onchocerciasis and a combination of ivermectin, albendazole and diethylcarbamazine (DEC) for the treatment of lymphatic filariasis in areas that are not co-endemic for onchocerciasis or loiasis. Limitations of these treatment strategies are due to potential severe adverse events in onchocerciasis and loiasis patients following DEC or ivermectin treatment, respectively, the lack of a macrofilaricidal efficacy of those drugs and the risk of drug resistance development. Thus, to achieve the elimination of transmission of onchocerciasis and the elimination of lymphatic filariasis as a public health problem by 2030, the WHO defined in its roadmap that new alternative treatment strategies with macrofilaricidal compounds are required. Within a collaboration of the non-profit organizations Drugs for Neglected Diseases initiative (DNDi), the Bill & Melinda Gates Foundation, and partners from academia and industry, several new promising macrofilaricidal drug candidates were identified, which will be discussed in this review.

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.

Pharmacokinetics, Safety, and Tolerability of Oxfendazole in Healthy Adults in an Open-Label Phase 1 Multiple Ascending Dose and Food Effect Study

Neurocysticercosis and trichuriasis are difficult-to-treat parasitic infections that affect more than 1.5 billion people worldwide. Oxfendazole, a potent broad-spectrum benzimidazole anthelmintic approved for use in veterinary medicine, has shown substantial antiparasitic activity against neurocysticercosis and intestinal helminths in preclinical studies. As part of a program to transition oxfendazole from veterinary medicine to human use, phase I multiple ascending dose and food effect studies were conducted. Thirty-six healthy adults were enrolled in an open-label study which evaluated (i) the pharmacokinetics and safety of oxfendazole following multiple ascending doses of oxfendazole oral suspension at 3, 7.5, and 15 mg/kg once daily for 5 days and (ii) the effect of food on oxfendazole pharmacokinetics and safety after a single 3-mg/kg dose administered following an overnight fast or the consumption of a fatty breakfast. Following multiple oral dose administration, the intestinal absorption of oxfendazole was rapid, with the time to maximum concentration of drug in serum (Tmax) ranging from 1.92 to 2.56 h. A similar half-life of oxfendazole (9.21 to 11.8 h) was observed across all dose groups evaluated, and oxfendazole exhibited significantly less than a dose-proportional increase in exposure. Oxfendazole plasma exposures were higher in female subjects than in male subjects. Following daily administration, oxfendazole reached a steady state in plasma on study day 3, with minimal accumulation. Food delayed the oxfendazole Tmax by a median of 6.88 h and resulted in a 49.2% increase in the maximum observed drug concentration in plasma (Cmax) and an 86.4% increase in the area under the concentration-time curve (AUC). Oxfendazole was well tolerated in all study groups, and there were no major safety signals identified in this study. (This study has been registered at ClinicalTrials.gov under identifier NCT03035760.).

Pharmacokinetics, Safety, and Tolerability of Oxfendazole in Healthy Volunteers: a Randomized, Placebo-Controlled First-in-Human Single-Dose Escalation Study

Cysticercosis is a parasitic disease that frequently involves the human central nervous system (CNS), and current treatment options are limited. Oxfendazole, a veterinary medicine belonging to the benzimidazole family of anthelmintic drugs, has demonstrated substantial activity against the tissue stages of Taenia solium and has potential to be developed as an effective therapy for neurocysticercosis. To accelerate the transition of oxfendazole from veterinary to human use, the pharmacokinetics, safety, and tolerability of oxfendazole were evaluated in healthy volunteers in this phase 1 first-in-human (FIH) study. Seventy subjects were randomly assigned to receive a single oral dose of oxfendazole (0.5, 1, 3, 7.5, 15, 30, or 60 mg oxfendazole/kg body weight) or placebo and were followed for 14 days. Blood and urine samples were collected, and the concentrations of oxfendazole were measured using a validated ultraperformance liquid chromatography mass spectrometry method. The pharmacokinetic parameters of oxfendazole were estimated using noncompartmental analysis. Oxfendazole was rapidly absorbed with a mean plasma half-life ranging from 8.5 to 11 h. The renal excretion of oxfendazole was minimal. Oxfendazole exhibited significant nonlinear pharmacokinetics with less than dose-proportional increases in exposure after single oral doses of 0.5 mg/kg to 60 mg/kg. This nonlinearity of oxfendazole is likely due to the dose-dependent decrease in bioavailability that is caused by its low solubility. Oxfendazole was found to be well tolerated in this study at different escalating doses without any serious adverse events (AEs) or deaths. There were no significant differences in the distributions of hematology, biochemistry, or urine parameters between oxfendazole and placebo recipients. (This study has been registered at ClinicalTrials.gov under identifier NCT02234570.).

A chromatographic study on the retention behavior of the amylose tris(3-chloro-5-methylphenylcarbamate) chiral stationary phase under aqueous conditions

In this study, the retention properties of the immobilized polysaccharide-derived Chiralpak IG-3 chiral stationary phase under aqueous-organic conditions were investigated. A systematic evaluation of the retention factors of the enantiomers of the chiral sulfoxide oxfendazole, endowed with anthelmintic activity and selected as test compound, was carried out changing progressively the water content in hydro-organic eluents containing methanol, ethanol or acetonitrile. From the results obtained with acetonitrile/water mobile phases and the associated retention plots, clear U-shape retention dependencies, indicative of the interplay of both hydrophilic interaction liquid chromatography and reversed-phase modes, were highlighted. A U-turn point of retention mechanism was recorded in correspondence of the acetonitrile/water 100:40 v/v mobile phase. Retention was significantly affected by small percentages of trifluoroacetic acid or diethylamine additives incorporated in the mobile phase. It is worth emphasizing that the basic additive was more effective in reducing retention in the reversed-phase region, while the action of acid additive was more pronounced in the hydrophilic interaction liquid chromatography region. Finally, either in the transition from hydrophilic interaction liquid chromatography to reversed-phase conditions or after additive addition, the enantioselectivity did not vary significantly.

Pharmacokinetic assessment of the monepantel plus oxfendazole combined administration in dairy cows

Monepantel (MNP) is a novel anthelmintic compound launched into the veterinary pharmaceutical market. MNP is not licenced for use in dairy animals due to the prolonged elimination of its metabolite monepantel sulphone (MNPSO₂ ) into milk. The goal of this study was to evaluate the presence of potential in vivo drug-drug interactions affecting the pattern of milk excretion after the coadministration of the anthelmintics MNP and oxfendazole (OFZ) to lactating dairy cows. The concentrations of both parent drugs and their metabolites were measured in plasma and milk samples by HPLC. MNPSO₂ was the main metabolite recovered from plasma and milk after oral administration of MNP. A high distribution of MNPSO₂ into milk was observed. The milk-to-plasma ratio (M/P ratio) for this metabolite was equal to 6.75. Conversely, the M/P ratio of OFZ was 1.26. Plasma concentration profiles of MNP and MNPSO₂ were not modified in the presence of OFZ. The pattern of MNPSO₂ excretion into milk was also unchanged in animals receiving MNP plus OFZ. The percentage of the total administered dose recovered from milk was 0.09 ± 0.04% (MNP) and 2.79 ± 1.54% (MNPSO₂ ) after the administration of MNP alone and 0.06 ± 0.04% (MNP) and 2.34 ± 1.38% (MNPSO₂ ) after the combined treatment. The presence of MNP did not alter the plasma and milk disposition kinetics of OFZ. The concentrations of the metabolite fenbendazole sulphone tended to be slightly higher in the coadministered group. Although from a pharmacodynamic point of view the coadministration of MNP and OFZ may be a useful tool, the presence of OFZ did not modify the in vivo pharmacokinetic behaviour of MNP and therefore did not result in reduced milk concentrations of MNPSO₂ .