Triclabendazole

Synthetic Routes and Reaction Conditions

Triclabendazole can be synthesized using various methods. One common method involves starting with 1,2,3-trichlorobenzene, which undergoes hydrolysis in high-concentration alkali liquor to form 2,3-dichlorophenol sodium . This intermediate reacts with 4,5-dichloro-2-nitroaniline in a methylbenzene aqueous solution to form 4-chloro-5-(2,3-dichlorophenoxy)-2-nitroaniline . The nitro group is then reduced using a hydrogen catalytic transfer method, and the resulting compound undergoes methylation to yield this compound .

Another method involves using 3,4-dichloroaniline as the starting material, followed by acylation, nitration, hydrolysis, condensation, reduction with hydrazine hydrate, and ring-closure with S-methylisothiourea sulfate . This method avoids the use of hazardous reagents and high-pressure reactions, making it safer and more environmentally friendly .

Industrial Production Methods

Industrial production of this compound typically follows the synthetic routes mentioned above, with optimizations for large-scale manufacturing. The use of inexpensive and readily available starting materials, along with environmentally friendly reagents, makes the process cost-effective and suitable for large-scale production .

Types of Reactions

Triclabendazole undergoes various chemical reactions, including:

Oxidation: This compound is metabolized in the liver to form sulfone and sulfoxide metabolites.

Reduction: The nitro group in the intermediate compound is reduced to an amine group during synthesis.

Substitution: The synthesis involves nucleophilic aromatic substitution reactions to introduce the dichlorophenoxy group.

Common Reagents and Conditions

Oxidation: Liver enzymes catalyze the oxidation of this compound to its metabolites.

Reduction: Hydrogen catalytic transfer or hydrazine hydrate is used for the reduction of the nitro group

Substitution: High-concentration alkali liquor and methylbenzene aqueous solution are used for nucleophilic aromatic substitution.

Major Products Formed

Sulfone and sulfoxide metabolites: Formed during the oxidation of this compound in the liver.

4-chloro-5-(2,3-dichlorophenoxy)-2-nitroaniline: An intermediate in the synthesis of this compound.

Treatment of Fascioliasis

Clinical Efficacy

Triclabendazole is the drug of choice for treating fascioliasis. Studies have demonstrated high cure rates following treatment:

• Cure Rates by Dosage :

  Dosage Regimen	Cure Rate (%)	Study Reference
  10 mg/kg (single dose)	70% - 100%
  20 mg/kg (two doses)	96%
  10 mg/kg (multiple doses)	63% - 88%

In a retrospective cohort study involving children in Peru, the initial treatment with this compound resulted in a 55% cure rate , which decreased with subsequent treatments, indicating potential resistance or treatment failure in endemic areas .

Case Studies

• Case Study Example : In a report involving multiple cases of chronic fascioliasis, patients underwent several rounds of treatment with varying dosages of this compound. Despite initial improvements, many continued to shed Fasciola eggs post-treatment, highlighting challenges in achieving complete parasitological cure .

Potential Applications in Schistosomiasis

Recent studies have evaluated this compound's efficacy against Schistosoma mansoni , particularly in patients with co-infections of fascioliasis and schistosomiasis. A field survey showed that:

• Cure Rate for Schistosomiasis :
  • After two doses of this compound, the cure rate was 32.7% for schistosomiasis compared to 96% for fascioliasis .
• In Vitro Studies : this compound demonstrated significant effects on adult schistosomes, leading to rapid destruction of their tegument within hours .

Cancer Research

Emerging research suggests that this compound may have applications in oncology:

• Mechanism of Action : It has been shown to induce pyroptosis—a form of programmed cell death—in breast cancer cells by activating caspase-3 pathways. This mechanism involves the elevation of reactive oxygen species and the regulation of apoptotic proteins .
• Tumor Volume Reduction : In xenograft models, this compound significantly reduced tumor volumes, indicating its potential as an anti-cancer agent .

Resistance and Treatment Challenges

Despite its efficacy, there are growing concerns regarding resistance to this compound:

• A study reported that higher baseline egg counts and lower socioeconomic status were associated with treatment failure in children with chronic fascioliasis . This underscores the need for ongoing surveillance and research into alternative treatments or combination therapies to combat resistance.

Triclabendazole and its metabolites are absorbed by the tegument of liver flukes, leading to a decrease in the resting membrane potential and inhibition of motility . This disruption affects the surface and ultrastructure of the flukes, ultimately leading to their death . This compound binds to beta-tubulin, preventing the polymerization of microtubules, which is essential for the survival of the flukes .

Triclabendazole is unique among benzimidazoles due to its efficacy against both immature and mature liver flukes . Similar compounds include:

Albendazole: Used to treat a variety of parasitic infections but less effective against liver flukes.

Thiabendazole: Another benzimidazole derivative with a different mechanism of action, primarily used to treat strongyloidiasis.

Closantel: Effective against immature liver flukes but not as broad-spectrum as this compound.

This compound’s unique structure, including a chlorinated benzene ring and the absence of a carbamate group, contributes to its distinct mechanism of action and efficacy .

Triclabendazole (TCBZ) is a benzimidazole derivative that is primarily used as an anthelmintic agent for the treatment of infections caused by Fasciola hepatica and Fasciola gigantica. This compound exhibits a range of biological activities, particularly against helminths, and has garnered attention for its potential applications beyond parasitic infections. This article delves into the biological activity of this compound, presenting research findings, case studies, and a comprehensive analysis of its mechanisms of action.

The precise mechanism of action of this compound remains partially understood; however, several key pathways have been identified:

• Microtubule Disruption : TCBZ disrupts microtubule formation in helminths, leading to tegumental damage and impaired motility. This effect has been demonstrated in studies involving F. hepatica, where TCBZ exposure resulted in autophagic changes and loss of tubulin immunoreactivity in the tegumental syncytium .
• Metabolite Activity : The sulphoxide metabolite of TCBZ is believed to play a significant role in its efficacy. This metabolite exhibits delayed but potent effects on parasite motility and may act through multiple targets, including inhibition of adenylate cyclase activity .
• Oxidative Phosphorylation : There is evidence suggesting that TCBZ may uncouple oxidative phosphorylation, which could contribute to its anthelmintic effects .

Efficacy in Treating Fascioliasis

This compound is notably effective against all stages of Fasciola infections. A review of clinical studies indicates high cure rates following treatment with TCBZ:

Despite these high efficacy rates, treatment failures have been documented, particularly in cases with high baseline egg counts or lower socioeconomic status . A retrospective cohort study in Peru found that only 55% of children achieved parasitologic cure after the first round of treatment, with cure rates declining significantly after multiple doses .

Case Studies

Several case studies highlight the variability in treatment outcomes with this compound:

• Case Study 1 : A 51-year-old female farmer experienced significant weight loss and abdominal pain due to Fasciola infection. After initial treatment with TCBZ (10 mg/kg), her symptoms improved; however, she relapsed after eight months and continued shedding Fasciola eggs despite subsequent treatments .
• Case Study 2 : In another case involving chronic fascioliasis, a patient received multiple courses of TCBZ but failed to achieve sustained parasitologic cure, emphasizing the need for ongoing research into resistance mechanisms and alternative treatments .

Broader Biological Activities

Recent studies have also explored the antibacterial properties of this compound. Research indicates that TCBZ exhibits activity against certain Gram-positive bacteria, including methicillin-resistant strains. In combination with other agents, it has demonstrated synergistic effects against Gram-negative pathogens like E. coli and Klebsiella pneumoniae .

Basic Research Questions

Q. What is the primary mechanism of action of triclabendazole against Fasciola species, and how can researchers validate this experimentally?

this compound, a benzimidazole derivative, disrupts microtubule polymerization in parasitic tegumental cells, leading to impaired nutrient absorption and paralysis. However, its exact molecular targets remain debated. To validate this:

• Use in vitro assays with Fasciola hepatica larvae, measuring microtubule integrity via immunofluorescence microscopy .
• Compare dose-response curves of this compound with known microtubule-disrupting agents (e.g., albendazole) to identify overlapping pathways .
• Conduct RNA sequencing post-treatment to identify differentially expressed genes linked to cytoskeletal regulation .

Q. How can researchers design a robust in vitro model to assess this compound efficacy across Fasciola life stages?

• Experimental Design :

• Culture newly excysted juveniles (NEJs) and adult flukes in bile-containing media.
• Treat with this compound sulfoxide (active metabolite) at concentrations mimicking human pharmacokinetics (e.g., 0.1–10 µM) .
• Monitor motility inhibition (via video tracking) and tegument damage (scanning electron microscopy) over 72 hours .
  • Data Analysis : Use Kaplan-Meier survival curves and EC50 calculations to compare stage-specific susceptibility .

Q. What methodologies are recommended for quantifying this compound and its metabolites in biological samples?

• Analytical Techniques :

• High-performance liquid chromatography (HPLC) with UV detection for plasma/serum samples, validated per ICH guidelines (linearity: 0.1–50 µg/mL; recovery >85%) .
• Liquid chromatography-mass spectrometry (LC-MS) for low-concentration metabolite detection (e.g., sulfoxide and sulfone derivatives) .
  • Sample Preparation : Protein precipitation with acetonitrile followed by solid-phase extraction to minimize matrix interference .

Advanced Research Questions

Q. How can conflicting data on this compound’s efficacy in resistant Fasciola strains be systematically analyzed?

• Contradiction Resolution :

• Perform comparative genomics on resistant vs. susceptible strains to identify mutations in β-tubulin or other putative targets .
• Use isothermal titration calorimetry (ITC) to measure this compound binding affinity to purified tubulin isoforms .
• Validate resistance markers via CRISPR-Cas9 editing in model organisms (e.g., Caenorhabditis elegans) .
  • Triangulation : Combine phenotypic assays (egg hatch tests), molecular data, and clinical field studies to reconcile discrepancies .

Q. What experimental strategies can elucidate this compound’s role in modulating host-pathogen interactions beyond direct antiparasitic effects?

• Host-Centric Approaches :

• Transcriptomic profiling of human hepatocytes post-treatment to identify immunomodulatory pathways (e.g., cytokine signaling) .
• Co-culture Fasciola with host cells and measure this compound-induced changes in oxidative stress markers (e.g., glutathione levels) .
  • Parasite Adaptations : Track excretory-secretory product (ESP) composition using proteomics to detect evasion mechanisms .

Q. How can researchers optimize this compound dosing regimens to mitigate resistance while maintaining efficacy in human trials?

• Pharmacokinetic/Pharmacodynamic (PK/PD) Modeling :

• Develop compartmental models integrating patient covariates (e.g., liver function, age) using NONMEM or Monolix .
• Simulate resistance emergence under different dosing strategies (e.g., pulsed vs. continuous) .
  • Clinical Trial Design :
• Use adaptive trial designs with interim analyses to adjust dosing based on early efficacy/resistance data .
• Include coproantigen reduction as a primary endpoint to quantify parasitological response .

Q. What molecular pathways underlie this compound’s off-target effects, such as chronological lifespan extension in yeast?

• Mechanistic Studies :

• Deploy Saccharomyces cerevisiae knockout libraries to identify genes essential for this compound-induced lifespan extension (e.g., MSN2/4, RIM15) .
• Measure intracellular cAMP levels via ELISA after drug exposure to confirm adenylyl cyclase inhibition .
  • Comparative Analysis : Contrast this compound’s effects with rapamycin using RNA-seq to dissect TOR pathway crosstalk .

Q. Methodological Guidance

Q. How should researchers address ethical and logistical challenges in this compound clinical trials for fascioliasis in endemic regions?

• Participant Selection :

• Use stratified randomization based on infection severity (e.g., egg counts, imaging-confirmed liver damage) .
• Collaborate with local health authorities to ensure informed consent and post-trial access to treatment .
  • Data Integrity : Implement double-blinding and third-party monitoring to reduce bias in resource-limited settings .

Q. What statistical approaches are most effective for analyzing this compound’s time-dependent efficacy in longitudinal studies?

• Mixed-Effects Models : Account for repeated measures and inter-patient variability using R’s lme4 or SAS PROC MIXED .
• Survival Analysis : Apply Cox proportional hazards models to evaluate time-to-parasitological cure .

Q. How can researchers ensure reproducibility when studying this compound’s metabolic fate in preclinical models?

• Standardization :
• Use certified reference materials (e.g., Eurandom) for metabolite quantification .
• Publish raw LC-MS/MS data in public repositories (e.g., MetaboLights) .
• Cross-Validation : Replicate key findings in multiple models (e.g., rodents, sheep) and independent labs .