Novel triclabendazole prodrug: A highly water soluble alternative for the treatment of fasciolosis

Fosfatriclaben: Effective dose determination and comparative efficacy assessment with closantel, triclabendazole+ivermectin, triclabendazole+albendazole in artificially infected cattle

Two controlled efficacy studies were conducted to determine the effective dose of fosfatriclaben (FTCB) and compare its fasciolicidal efficacy with that of three commercial products against eggs and adult stages of Fasciola hepatica in artificially infected cattle. In study 1, 20 trematode-free Holstein Friesian steers were infected on day 0 with 500 F. hepatica metacercariae. Ten weeks after infection and the steers were confirmed to be positive for trematode eggs through a modified sedimentation method. On day 75, they were divided into five groups of four animals each for treatment. Group 1 (G1) served as the untreated control; G2, G3, and G4 received FTCB at 4, 6, and 8 mg/kg/intramuscularly (IM), respectively. G5 received a combined treatment of triclabendazole (TCBZ) (12 mg/kg IM + ivermectin (0.2 mg/kg IM). Individual faecal analyses were performed on days -8, 0, 70, 75, and 105 to evaluate the reduction in trematode eggs. Four weeks after treatment, the steers were humanely slaughtered to harvest the livers and remove the parasites present in the bile ducts. Efficacy was evaluated by the reduction in fecal egg counts or in number of adult parasites, compared to the untreated control. The effective FTCB dose was 6 mg/kg. Once the effective dose was determined, study 2 was conducted on another 20 steers infected with 500 F. hepatica metacercariae, to compare the effectiveness of FTCB with three commercials fasciolicides. All procedures were performed as described in study 1, and treatments were as follows: Group 1 (G1), closantel (5 mg/kg subcutaneously (SC)); G2, TCBZ (12 mg/kg IM) + ivermectin (0.2 mg/kg IM); G3, FTCB (6 mg/kg IM); G4, triclabendazole (12 mg/kg) + albendazole (5 mg/kg/PO (orally); and G5 served as an untreated control. The results indicated that all tested compounds were highly effective in the reduction of faecal egg excretion (99.7-100%) and adult parasites (98.9-100%), except closantel, which exhibited low efficacy (74.4%) when tested against adult trematodes. We concluded that the effective dose of FTCB for cattle was 6 mg/kg IM, which is half the recommended clinical dose of the commercial combination of TCBZ and ivermectin. The fasciolicidal efficacy of FTCB was like the other three flukicides in reducing adult F. hepatica and Fasciola eggs; however, closantel was not sufficiently efficient against adult flukes.

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.

Field study on the determination of the effective dose of injectable fosfatriclaben prodrug in sheep naturally infected with Fasciola hepatica

The aim of the present study was to determine the effective dose of fosfatriclaben through a field study in sheep naturally infected with F. hepatica. Thirty crossbred sheep positive for fluke eggs were selected for inclusion in the trial. On day 0, 5 groups of 6 animals each were formed for treatments: group 1 (G1), G2, and G3 received fosfatriclaben at 4, 6, and 8 mg/kg/IM, respectively. G4 received triclabendazole at 10 mg/kg/PO, and G5 was the untreated control group. Fecal samples of the sheep were analyzed to count the number of fluke eggs to evaluate the percentage of egg reduction. Twenty-one days after treatment, all sheep were humanely euthanized to extract the flukes from the bile ducts. They were counted to assess the percentage of fluke reduction. Fosfatriclaben reduced fluke eggs by 99.6, 99.6, and 100% and flukes by 94.3, 100, and 100%, respectively. Triclabendazole reduced fluke eggs by 95.2% and flukes by 100%. The fosfatriclaben injectable prodrug showed a high fasciolicidal efficacy similar to triclabendazole, with advantages over its predecessor, since only half the dose as compared to triclabendazole was required to remove eggs and flukes in the sheep that were studied.

Effectiveness of an experimental injectable prodrug formulation against Fasciola hepatica of different ages in experimentally infected sheep

In this work, we present an evaluation of the fasciolicidal efficacy of a new injectable formulation of fosfatriclaben in comparison with the subcutaneous closantel and oral triclabendazole formulations currently used in veterinary practice as fasciolicides. The study was carried out in vivo on Fasciola hepatica at 2, 4, 6 and 8 weeks of age in experimentally infected sheep. To evaluate the formulation, the percent reduction of the parasite load was measured and the number of fluke eggs. Fosfatriclaben was used at 6 mg/kg/IM (dose equivalent to triclabendazole content), closantel at 5% at 10 mg/kg/SC, and triclabendazole at 10 mg/kg/PO; the control group received no treatment. Fosfatriclaben showed fasciolicidal efficacies of 95.5 %, 100 %, 100 % and 100 %, and triclabendazole showed similar efficacies of 97.4 %, 100 %, 100 % and 100 %, at the different treatment weeks (P > 0.05). Closantel showed limited efficacy against 2-, 4- and 6-week-old flukes but 100 % efficacy in adult flukes. All three evaluated formulations eliminated all 8-week-old F. hepatica trematode eggs. Although fosfatriclaben and triclabendazole showed similar fasciolicidal efficacy, the intramuscular administration of fosfatriclaben has several advantages over the oral administration of triclabendazole, such as ease of administration for veterinary use and a reduced risk of accidents for both the operator and the animals. In addition, the dose used in this injectable formulation is only 60 % of the oral dose, which reduces environmental contamination.

Current Status for Controlling the Overlooked Caprine Fasciolosis

The disease fasciolosis is caused by the liver flukes Fasciola hepatica and F. gigantica, which infect a wide range of mammals and production livestock, including goats. These flatworm parasites are globally distributed and predicted to cost the livestock industry a now conservative USD 3 billion per year in treatment and lowered on-farm productivity. Infection poses a risk to animal welfare and results in lowered fertility rates and reduced production yields of meat, milk and wool. This zoonotic disease is estimated to infect over 600 million animals and up to 2.4 million humans. Current and future control is threatened with the global emergence of flukes resistant to anthelmintics. Drug resistance calls for immediate on-farm parasite management to ensure treatments are effective and re-infection rates are kept low, while a sustainable long-term control method, such as a vaccine, is being developed. Despite the recent expansion of the goat industry, particularly in developing countries, there are limited studies on goat-focused vaccine control studies and the effectiveness of drug treatments. There is a requirement to collate caprine-specific fasciolosis knowledge. This review will present the current status of liver fluke caprine infections and potential control methods for application in goat farming.

Anthelmintics for drug repurposing: Opportunities and challenges

Drug repositioning is defined as a process to identify a new application for drugs. This approach is critical as it takes advantage of well-known pharmacokinetics, pharmacodynamics, and toxicity profiles of the drugs; thus, the chance of their future failure decreases, and the cost of their development and the required time for their approval are reduced. Anthelmintics, which are antiparasitic drugs, have recently demonstrated promising anticancer effects in vitro and in vivo. This literature review focuses on the potential of anthelmintics for repositioning in the treatment of cancers. It also discusses their pharmacokinetics and pharmacodynamics as antiparasitic drugs, proposed anticancer mechanisms, present development conditions, challenges in cancer therapy, and strategies to overcome these challenges.

Efficiency comparison of experimental fosfatriclaben with three commercial fasciolicides in experimentally infected sheep

In this work, we compare and evaluate the efficiency of fosfatriclaben with three commercial fasciolicides in experimentally infected sheep. Fosfatriclaben is a novel prodrug derived from triclabendazole; it is highly water-soluble with excellent aqueous stability at pH 7, properties that make it ideal for developing intramuscular pharmaceutical compositions in the form of solutions. In order to compare, 30 mixed breed sheep, previously diagnosed negative to fluke eggs, were infected with 200 metacercariae of Fasciola hepatica, twice. Five groups of six animals/each were formed for treatments. Group 1 (G1) was treated with closantel 5% injectable at 5 mg/kg subcutaneously, G2 with clorsulon at 2 mg/kg subcutaneously, G3 with triclabendazole at 12 mg/kg per os, G4 with fosfatriclaben at 6 mg/kg intramuscularly (dose equivalent to triclabendazole content), and G5 remained as the non-treated control. On day 110, fecal samples were examined to determine the percentage of egg reduction after treatment, and sheep were humanely euthanized. The livers were collected, the flukes were extracted, measured, and counted. Efficiency in egg reduction was of 86.8, 90.5, 98.4, and 97.3% for closantel, clorsulon, triclabendazole, and fosfatriclaben, respectively, and efficiency against flukes was of 96.2, 91.9, 99.4, and 95.7%, respectively. No statistical differences were found between treatments. It is concluded that fosfatriclaben at 6 mg/kg intramuscularly presented a high fasciolicide efficiency, similar to the best commercial fasciolicides, having advantage over its predecessor since it uses half of the dose required by triclabendazole to remove flukes in sheep under study.

Drug resistance in liver flukes

Liver flukes include Fasciola hepatica, Fasciola gigantica, Clonorchis sinensis, Opisthorchis spp., Fascioloides magna, Gigantocotyle explanatum and Dicrocoelium spp. The two main species, F. hepatica and F. gigantica, are major parasites of livestock and infections result in huge economic losses. As with C. sinensis, Opisthorchis spp. and Dicrocoelium spp., they affect millions of people worldwide, causing severe health problems. Collectively, the group is referred to as the Food-Borne Trematodes and their true significance is now being more widely recognised. However, reports of resistance to triclabendazole (TCBZ), the most widely used anti-Fasciola drug, and to other current drugs are increasing. This is a worrying scenario. In this review, progress in understanding the mechanism(s) of resistance to TCBZ is discussed, focusing on tubulin mutations, altered drug uptake and changes in drug metabolism. There is much interest in the development of new drugs and drug combinations, the re-purposing of non-flukicidal drugs, and the development of new drug formulations and delivery systems; all this work will be reviewed. Sound farm management practices also need to be put in place, with effective treatment programmes, so that drugs can be used wisely and their efficacy conserved as much as is possible. This depends on reliable advice being given by veterinarians and other advisors. Accurate diagnosis and identification of drug-resistant fluke populations is central to effective control: to determine the actual extent of the problem and to determine how well or otherwise a treatment has worked; for research on establishing the mechanism of resistance (and identifying molecular markers of resistance); for informing treatment options; and for testing the efficacy of new drug candidates. Several diagnostic methods are available, but there are no recommended guidelines or standardised protocols in place and this is an issue that needs to be addressed.

Minor chemical modifications of the aminosteroid derivative RM-581 lead to major impact on its anticancer activity, metabolic stability and aqueous solubility

The aminosteroid (AM) RM-581 is built around a mestranol backbone and has recently emerged as this family's lead candidate, showing in vitro and in vivo potency over different types of cancer, including high fatality pancreatic cancer. To extend the structure-activity relationships (SAR) to other estrane analogs, we synthesized a focused series of RM-581 derivatives at position C3 or C2 of its steroidal core. These new AM derivatives were first tested on a large selection of prostate, breast, pancreatic and ovarian cancer cell lines. The impact of these modifications on metabolic stability (human liver microsomes) was also measured. A SAR study revealed a fine regulation of anticancer activity related to the nature of the substituent. Indeed, the addition of potential prodrug groups like acetate, sulfamate or phosphate (compounds 8, 9 and 10) at C3 of the phenolic counterpart provided better antiproliferative activities than RM-581 in breast and pancreatic cancer cell types while maintaining activity in other cancer cell lines. Also, the phosphate group was highly beneficial on water solubility. However, the bulkier carbamate prodrugs 6 (N,N-dimethyl) and 7 (N,N-diethyl) were less active. Otherwise, carbon homologation (CH₂) at C2 (compound 33) was beneficial to metabolic stability and, in the meantime, this AM conserved the same anticancer activity as RM-581. However, the replacement of the hydroxy or methoxy at C3 by a hydrogen or an acetyl (compound 17 or 21b) was detrimental for anticancer activity, pointing to a crucial molecular interaction of the aromatic oxygen atom at this position. Overall, this work provided a better knowledge of the structural requirements to maintain RM-581's anticancer activity, and also identified minor structural modifications to increase both metabolic stability and water solubility, three important parameters of pharmacological development.

A Scoping Review of the Prevalence of Fascioliasis in Malaysia and Risk Factors for Infection

This review aimed to provide a comprehensive overview of ruminant and human fascioliasis in Malaysia and to identify research gaps in knowledge of the prevalence of fascioliasis in Malaysia and risk factors for the disease using available evidence-based data. We conducted a scoping review based on the framework of Arksey and O'Malley. The preferred reporting items for systematic reviews and meta-analyses were used to guide the review process. The citation search was performed between May and September 2018. Using specific keywords, literature published between 1998 to September 2018 was retrieved from electronic databases. Six articles related to fascioliasis in Malaysia were included in the final review from 1,932 screened articles and reports. Five studies focused on ruminants, including cattle, buffaloes, sheep and goats in the states of Terengganu and Perak. The most frequent ruminant fascioliasis outbreaks involved cattle and goats, with a prevalence of 82%-95% and these outbreaks occurred in Terengganu. Only one study examined the risk of fascioliasis in cattle. In the study, the age and sex of the cattle were important risk-related parameters. The search returned only one documented report of a suspected case of human fascioliasis with an atypical clinical presentation. At present, human fascioliasis in Malaysia remains under-reported and its prevalence remains unknown. The data summarised in this review based on existing evidence identifies research gaps on fascioliasis in ruminants and humans.

Improving the Dissolution of Triclabendazole from Stable Crystalline Solid Dispersions Formulated for Oral Delivery

Triclabendazole belongs to the class II/IV of the Biopharmaceuticals Classification System, and its low aqueous solubility represents a major drawback during the development of effective dosage forms. Therefore, the goal of this study was to elucidate whether polymeric solid dispersions would represent a suitable approach to overcome such disadvantage. Due to the lack of information on triclabendazole release, four different dissolution media were evaluated to analyze drug dissolution rate. The polymeric solid dispersions were characterized by X-ray diffraction and Fourier transform infrared spectroscopy. The selected final formulations were further stored for 24 months, and their physical stability was evaluated by means of X-ray diffraction and drug dissolution assays. Drug solubility studies indicated that poloxamer 407 (P407) solubilized a higher amount of drug than polyethylene glycol 6000. Drug-to-carrier ratio, nature of the selected carriers, and the type of dissolution media were important factors for increasing dissolution. By infrared spectroscopy, there were no specific interactions between the drug and polymers. The physicochemical characterization of the systems showed a detectable evidence of drug amorphization by increasing the carrier ratio. Micromeritic studies indicated that raw triclabendazole, physical mixtures, and reference formulation showed poor flow properties, in contrast to the triclabendazole:P407 solid dispersion sample. Both the crystalline properties and dissolution rate of selected samples were very similar after 24 months at room temperature. Thus, considering physical stability and dissolution studies, the development of the solid dispersion is a very suitable methodology to improve triclabendazole dissolution and, potentially, its biopharmaceutical performance.

Evaluation of nitazoxanide treatment following triclabendazole failure in an outbreak of human fascioliasis in Upper Egypt

Background

Fascioliasis is a neglected zoonosis with major public health implications in humans. Although triclabendazole (TCBZ) is the drug of choice, there are records of TCBZ failure worldwide. TCBZ-resistant fascioliasis is treated with alternative approved drugs including nitazoxanide (NTZ), with varying levels of efficacy. Data on NTZ efficacy after TCBZ failure in Egypt is scarce. This study evaluated the efficacy of NTZ in cases of TCBZ failure during an outbreak of fascioliasis in Assiut governorate of Upper Egypt.

Methodology/Principal findings

This prospective study included 67 patients from the outpatient clinic in Manfalout locality of Assiut governorate with clinical manifestations of acute fascioliasis. These included high eosinophilia (> 6% eosinophils in peripheral blood), positive anti-Fasciola antibodies, and hepatic focal lesions (HFL) or ascites on abdominal ultrasound or computed tomography. All patients initially received TCBZ at recommended doses. Patients were followed up after 1 month to assess response. According to the responses, patients were categorized as non-responders and responders. The non-responders received a trial of NTZ and were re-assessed for response based on clinical manifestations, eosinophil count, and abdominal ultrasound. Patients not responding to NTZ received additional doses of TCBZ.

One month after initial TCBZ treatment, 37 patients responded well to TCBZ, while 30 patients failed to respond with persistence of fever, abdominal pain, high eosinophilia, and HFL. Most non-responders were male (56.7%); females predominated among TCBZ responders (62.2%). The mean age of the non-responders was relatively lower, at 20.57 ± 14.47 years (p = 0.004). Following NTZ therapy, HFL disappeared in 9/30 (30%) patients and eosinophil counts normalized in only 2 (6.7%) patients, indicating an overall efficacy of 36.6%. The remaining cases received additional doses of TCBZ with complete clinical, pathological, and radiological resolution.

Conclusions/Significance

Nitazoxanide was partially effective in TCBZ failure in acute human fascioliasis in Upper Egypt. Further studies with larger samples are highly encouraged and further research is urgently needed to find new therapeutic alternatives to TCBZ.

Fascioliasis is a neglected zoonosis with major public health implications in humans. Triclabendazole (TCBZ) is the drug of choice, but alternative approved drugs are necessary in cases of TCBZ failure. Nitazoxanide (NTZ) is an alternative used in such cases. However, the efficacy of NTZ in TCBZ-failure cases among patients in Egypt remains unclear. In this study, the efficacy of NTZ was evaluated in cases of TCBZ failure during an outbreak of human fascioliasis in Assiut governorate of Upper Egypt. This study enrolled 67 patients diagnosed with fascioliasis based on clinical, laboratory, and radiological findings. These patients were referred from the outpatient clinic in Manfalout locality of Assiut governorate in Egypt. All patients received TCBZ at recommended doses as initial treatment. Those failing to respond were treated with NTZ at standard doses; following therapy, lesions in the liver and high eosinophil counts were resolved in 30% and 6.7% patients, respectively, indicating an overall efficacy of 36.6%. Therefore, in this outbreak of human fascioliasis in Upper Egypt, NTZ was found to be partially effective in cases with TCBZ failure.

Recent developments in the epidemiology, diagnosis, and treatment of Fasciola infection

PURPOSE OF REVIEW

This review aims at describing the latest research in Fasciola epidemiology, diagnosis, treatment, and control in endemic countries.

RECENT FINDINGS

The geographic distribution and range of reservoirs for Fasciola hepatica continues to expand. The impact of fascioliasis goes beyond human disease to affect food security and income in developed and developing countries. Promising serologic and molecular methods to diagnose fascioliasis have been described, but are not widely available. Triclabendazole remains the only highly active medication to treat human and livestock infected with juvenile and adult forms of Fasciola spp. Efforts to control fascioliasis may be hindered by the emergence of resistance to triclabendazole among livestock and subsequently in humans.

SUMMARY

Increased awareness and surveillance are likely to uncover the real distribution and burden of fascioliasis in human. Research into new drugs or adjuvants to tackle the emerging resistance to triclabendazole is imperative to treat and control Fasciola infection.

Solving the Delivery Problems of Triclabendazole Using Cyclodextrins

Triclabendazole is the first-line drug of choice to treat and control fasciolasis, a neglected parasitic human disease. It is a class II/IV compound according to the Biopharmaceutics Classification System. Thus, the aim of this study was to improve aqueous solubility and dissolution rate of triclabendazole complexed with 2-hydroxylpropyl-β-cyclodextrin (HP-β-CD) and methyl-β-cyclodextrin (Me-β-CD) at 1:1 and 1:2 M ratio. The impact of storage on the solubility, dissolution profile, and solid-state properties of such complexes was also investigated. Drug-carrier interactions were characterized by infrared spectroscopy, differential scanning calorimetry, X-ray diffractometry, and scanning electron microscopy. The solubility of triclabendazole improved up to 256- and 341-fold using HP-β-CD and Me-β-CD, respectively. In particular, the drug complexed with Me-β-CD showed a positive deviation from linearity, suggesting that its solubility increases with an increasing concentration of Me-β-CD concentration in a nonlinear manner. The drug dissolution was found to be improved through complex formation with HP-β-CD and Me-β-CD. In particular, the 1:2 M ratio complexes exhibited higher dissolution than the corresponding 1:1 M ratio complexes. The physicochemical characterization of the systems showed strong evidence of amorphous phases and/or of the formation of an inclusion complex. Stored at 25 °C, 60% RH for 24 months, drug complexed with β-cyclodextrins (CDs) at 1:2 M ratio remained amorphous. Based on these findings, it is postulated that the formation of triclabendazole-CD inclusion complexes produced significant enhancement in both the dissolution and solid-state properties of the drug, which may lead to the development of triclabendazole novel formulations with improved biopharmaceutical characteristics.

Assessment of the effective dose of an experimental intramuscular formulation against immature and adult Fasciola hepatica in sheep

The effective dose of an injectable prodrug, named compound alpha prodrug, against immature and adult Fasciola hepatica in experimentally infected sheep was determined. In a first experiment, 30 sheep were infected with Fasciola hepatica on day 0 and 50. After microscopic detection of faecal eggs on day 80, groups (n = 6) 1 to 3 were treated with 6, 8 and 10 mg/kg of the experimental water-soluble prodrug compound alpha intramuscularly, respectively. Group 4 was treated with closantel and group 5 remained untreated. Copromicroscopical examinations were made on day 0, 80 and 108. On day 110, trematodes were collected from the bile ducts. Fasciolicide efficacy was assessed as a percentage of fluke-egg and adult-fluke reduction. Fluke length was also recorded. In a second experiment aimed to assess the fasciolicide activity of compound alpha prodrug against four-week-old flukes, 12 sheep were infected on day 0 and allocated into two groups (n = 6). On day 50 post infection, group A was treated with the experimental water-soluble prodrug compound alpha at 6 mg/kg/IM and B remained untreated. Fasciolicide activity was assessed on day 80 after collection, microscopic observation and measurement of flukes present in the parenchyma for immature stages and on day 108 for adults. Egg output decreased 91.2, 96.0, 98.8 and 94.9% for groups 1, 2, 3 and 4, respectively. Compound alpha prodrug cleared 97.6%, 98.51% and 100% of adult stages in a dose-dependent manner. Closantel killed 81.95% flukes. Regarding the second experiment, 81.2% efficacy was achieved. Immature flukes were significantly smaller in the treated group. It is concluded that the intramuscular application of compound alpha prodrug exerted fasciolicide efficacy against adults of Fasciola hepatica.

Species-Specific Inactivation of Triosephosphate Isomerase from Trypanosoma brucei: Kinetic and Molecular Dynamics Studies

Human African Trypanosomiasis (HAT), a disease that provokes 2184 new cases a year in Sub-Saharan Africa, is caused by Trypanosoma brucei. Current treatments are limited, highly toxic, and parasite strains resistant to them are emerging. Therefore, there is an urgency to find new drugs against HAT. In this context, T. brucei depends on glycolysis as the unique source for ATP supply; therefore, the enzyme triosephosphate isomerase (TIM) is an attractive target for drug design. In the present work, three new benzimidazole derivatives were found as TbTIM inactivators (compounds 1, 2 and 3) with an I₅₀ value of 84, 82 and 73 µM, respectively. Kinetic analyses indicated that the three molecules were selective when tested against human TIM (HsTIM) activity. Additionally, to study their binding mode in TbTIM, we performed a 100 ns molecular dynamics simulation of TbTIM-inactivator complexes. Simulations showed that the binding of compounds disturbs the structure of the protein, affecting the conformations of important domains such as loop 6 and loop 8. In addition, the physicochemical and drug-like parameters showed by the three compounds suggest a good oral absorption. In conclusion, these molecules will serve as a guide to design more potent inactivators that could be used to obtain new drugs against HAT.