Nifurtimox

Nitroreductase-Mediated Bioactivation Pathways in Parasitic Organisms

Nifurtimox, as a prodrug, requires enzymatic activation within the parasite to exert its cytotoxic effects. pnas.orgmdpi.com This activation is catalyzed by nitroreductases (NTRs), enzymes that reduce the nitro group of the this compound molecule. patsnap.comacs.org The type of nitroreductase involved dictates the subsequent metabolic fate and the nature of the toxic species generated. acs.orgnih.gov

Parasitic Cellular and Molecular Targets of this compound

The toxic metabolites generated from this compound bioactivation exert their effects through various mechanisms, primarily by disrupting essential cellular processes and structures within the parasite.

Differential Selectivity Mechanisms between Parasitic and Mammalian Cells

The selectivity of this compound for parasites over human cells is partly attributed to differences in metabolic pathways and antioxidant defenses. patsnap.comnih.gov Parasites, particularly Trypanosoma cruzi, rely heavily on specific nitroreductase enzymes for the activation of this compound, enzymes that are either absent or present at much lower levels in human cells. patsnap.comnih.govacs.org This differential expression of nitroreductases leads to the preferential formation of toxic metabolites within the parasite. patsnap.comnih.govacs.org

Furthermore, the antioxidant systems of trypanosomatids are less robust compared to those of human cells, rendering the parasites more vulnerable to the oxidative damage induced by this compound's reactive metabolites. patsnap.compnas.org While human cells possess robust defenses like catalase, glutathione, peroxidases, and superoxide dismutase to neutralize ROS, parasites have a distinct trypanothione-dependent system. wikipedia.orgnih.gov The less effective antioxidant capacity in parasites contributes to the accumulation of cytotoxic levels of hydrogen peroxide and other radicals, leading to parasite death while sparing host cells to a greater extent. wikipedia.org

Efficacy Studies in Trypanosoma cruzi Infection Models

Research into the effectiveness of Nifurtimox against Trypanosoma cruzi has included both in vitro assessments across different parasite stages and in vivo studies utilizing animal models of Chagas disease.

Efficacy Studies in Trypanosoma brucei Infection Models

This compound has also been investigated for its activity against Trypanosoma brucei, the parasite responsible for Human African Trypanosomiasis (HAT).

Exploratory Research into Novel Therapeutic Applications

Beyond its established use for trypanosomiasis, exploratory research has investigated novel therapeutic applications for this compound, particularly in the field of oncology. This compound has been explored as a potential treatment for various cancers, with a notable focus on neuroblastoma. mdpi.combocsci.comgoogle.com Preclinical studies have investigated this compound's effects on neuroblastoma cells in vitro and in vivo. bocsci.commdpi.com In vitro studies have shown that this compound can reduce cell viability, induce apoptosis, and cause cell cycle arrest in neuroblastoma cell lines. bocsci.com It has also been suggested that this compound may influence lactate dehydrogenase (LDH) enzyme activity in neuroblastoma cells. bocsci.com In vivo preclinical studies have indicated that this compound can slow tumor growth in neuroblastoma models and may enhance the therapeutic efficacy of radiation in medulloblastoma models by inducing reactive oxygen species (ROS). bocsci.commdpi.comaacrjournals.org Research suggests this compound inhibits neuroblastoma cell growth, potentially via the inhibition of ROS production. mdpi.com this compound has also been investigated for its potential to inhibit angiogenesis and for its activity against other types of cancer in preclinical settings. mdpi.comgoogle.com

Clinical Trials in Chagas Disease

Nifurtimox is a recommended treatment for Chagas disease. plos.orgasm.orgnih.gov

Clinical Trials in Human African Trypanosomiasis (HAT)

This compound has shown some efficacy against second-stage HAT caused by Trypanosoma brucei gambiense. dndi.org

Observational Studies and Real-World Evidence of Therapeutic Effectiveness

Observational studies and real-world evidence have provided additional support for the effectiveness of this compound, particularly in the treatment of Chagas disease. This compound has been used for over 50 years to treat Chagas disease, a neglected tropical disease caused by the parasite Trypanosoma cruzi. researchgate.netresearchgate.net

A retrospective cohort study analyzed data from patients treated with this compound for Chagas disease between 1980 and 2019. nih.govplos.org This study included children, with a significant proportion having congenitally transmitted infections. nih.gov The CHICO study, a prospective, historically controlled study, evaluated the efficacy and safety of this compound in pediatric patients with Chagas disease. nih.gov The study confirmed the efficacy of a 60-day this compound treatment regimen compared to historical placebo treatment at 12 months. nih.govplos.org Serological response, defined as seronegative conversion or seroreduction, was observed in 32.9% of treated patients in the 60-day regimen at 12 months. nih.govplos.org At the end of a 4-year follow-up, seronegative conversion was observed in 8.12% and 8.16% of patients in the 60-day and 30-day regimens, respectively. nih.gov Exploratory analysis suggested that the highest rate of seronegative conversion occurred in the youngest age group (2 years or younger). nih.gov

An observational comparative study in Argentina reviewed long-term follow-up data from adults with chronic Chagas disease diagnosed between 1967 and 1980. researchgate.net The study compared outcomes in patients treated with this compound versus untreated patients. researchgate.net Accounting for potential confounders, patients treated with this compound were estimated to be at least twice as likely to achieve negative seroconversion compared to untreated patients. researchgate.net

Research on this compound Exposure During Pregnancy and Associated Outcomes

Research on this compound exposure during pregnancy and its associated outcomes is an area of ongoing investigation. While animal studies have indicated that this compound may cause fetal harm, there is insufficient data from human pregnancies to definitively inform the drug-related risk. drugs.com

Published data from case-control and observational studies on chronic Chagas disease during pregnancy have yielded inconsistent results regarding the risk of pregnancy loss, prematurity, and neonatal mortality in pregnant women with the disease. drugs.com Some studies have shown an increased risk of these outcomes, while others have not observed them. drugs.com

Due to the potential for embryofetal toxicity suggested by animal studies and the inconsistent results from human observational data, treatment of chronic Chagas disease with this compound is generally not recommended during pregnancy. drugs.com However, the underlying condition of the mother should also be considered. drugs.com

An observational pregnancy safety study is currently planned to collect data on the safety of this compound use in pregnant women with Chagas disease and the impact on their babies. clinicaltrial.be This study aims to gather information on birth defects, pregnancy outcomes (such as live birth, preterm birth, stillbirth, miscarriage, or abortion), and certain health problems in the child up to 12 months of age. clinicaltrial.be

Research has also investigated this compound exposure through breast milk during maternal treatment for Chagas disease. A study found that the presence of this compound in breast milk is limited, and breastfed infants had normal clinical evaluations with no observable adverse events. plos.orgnih.gov The median relative infant dose through breast milk was estimated to be low. plos.org These findings suggest that maternal this compound treatment during breastfeeding is unlikely to lead to clinically relevant exposures in breastfed infants. plos.orgnih.gov

Absorption and Distribution Studies

Following oral administration, nifurtimox is absorbed through the gastrointestinal tract and distributed via the bloodstream to various tissues. patsnap.com Animal studies in rats and dogs have shown that this compound is 80-90% orally bioavailable, with maximum plasma concentrations typically occurring within 3 hours. fda.gov this compound exhibits low plasma protein binding, ranging from 28% to 43% across different species, including humans, and is primarily bound to albumin. fda.govdrugbank.com Mass balance studies in rats have demonstrated extensive tissue distribution, with the highest concentrations of radioactivity observed in the kidneys and liver, followed by the lung, adrenal and thyroid glands, testes, brain, and spinal cord. fda.gov

Data on this compound Absorption and Distribution:

Metabolic Pathways and Metabolite Characterization

This compound undergoes extensive metabolism, primarily mediated by nitroreductase enzymes. plos.orgfda.govdrugbank.com Metabolism in liver microsomes via CYP450 enzymatic activity appears to be limited. fda.gov In vivo biotransformation of this compound can yield more than 30 metabolites, with molecular structures provisionally identified for the majority. plos.org Analysis of urine from rats dosed with radiolabeled this compound identified at least 30 radiolabeled products, although most were in trace amounts. nih.gov Leveraging this information, 18 products were identified in urine from participants in a Phase 1 clinical trial at levels sufficient for structural proposal based on high-resolution mass spectrometry fragmentation patterns. nih.gov Six predominant metabolites (M-1 to M-6) have been identified in urine and plasma. nih.gov Of these, M-4 and M-6 are the only metabolites that have shown relevant plasma exposure levels in humans, exceeding or approaching the guideline threshold of 10% of total exposure. researchgate.netplos.orgresearchgate.net

Data on this compound Metabolites:

Excretion Routes and Mass Balance Studies

Research into the excretion of this compound indicates that the parent drug is minimally excreted unchanged, with the majority of the dose eliminated as metabolites. Studies using radiolabeled this compound in rats have shown that almost all of the administered radioactivity is rapidly excreted, highlighting the extensive metabolism of the compound. researchgate.netacs.org

In rats, orally administered [14C]-nifurtimox was largely excreted within 24 hours, with nearly complete excretion (92.4% of the dose) within 120 hours. nih.gov Excretion occurred in approximately equal amounts via the renal (48.6% of dose) and fecal (43.8% of dose) routes following oral administration. nih.gov Only trace amounts of unchanged this compound were detected in excreta from rats, likely due to its instability. researchgate.netnih.gov

Studies in humans have also shown that a significant portion of the administered dose is recovered in urine as metabolites. Following administration of this compound, approximately 44% of the dose was recovered in urine as metabolites in the fed state, compared to about 27% in the fasted state. drugbank.comascpt.org This suggests that food intake influences the extent of urinary excretion of metabolites. While urinary excretion of metabolites has been quantified, detailed mass balance studies evaluating fecal and biliary excretion in humans have not been extensively reported. drugbank.comascpt.org However, based on animal studies, it is likely that both urine and feces are the main excretion routes in humans. plos.orgnih.gov

Despite the extensive metabolism, mass balance studies in bile duct cannulated rats following intravenous administration of [14C]-nifurtimox showed that approximately 49.6% of the dose was excreted in urine and 17.7% in bile within 24 hours. nih.gov An additional 6.9% was secreted directly into the gut. nih.gov The total recovery of radioactivity in these studies was high, indicating that the excretion routes were well-accounted for. nih.gov

The complex metabolic profile of this compound results in the excretion of numerous metabolites. In rat urine, over 30 radiolabeled products were detected after oral administration of [14C]-nifurtimox, although most were in trace amounts. acs.orgnih.gov In humans, approximately 20 metabolites have been identified in plasma and/or urine. fda.gov The most abundant metabolites detected in human plasma are M-4 and M-6. nih.govplos.orgnih.gov

Data on Excretion of Radiolabeled this compound in Rats:

Data on Urinary Recovery of this compound Metabolites in Humans:

Pharmacokinetic Modeling and Simulation Methodologies

Pharmacokinetic modeling and simulation methodologies have been applied to better understand the disposition of this compound and predict its behavior under various conditions. Non-linear mixed-effects modeling (NONMEM) has been utilized in pharmacokinetic analyses of this compound, particularly in the context of pooled data from individual participants. e-lactancia.orgiddo.org This approach allows for the characterization of population pharmacokinetic parameters and their variability. iddo.org

Population pharmacokinetic (popPK) modeling has been employed to characterize the pharmacometric properties of this compound. iddo.org Such models can be used to simulate plasma concentration-time profiles for different dosing regimens. plos.org Model evaluation typically involves graphical and statistical methods, including visual predictive checks (VPC) and bootstrap resampling techniques to assess model stability and robustness. iddo.orggu.se

Physiologically based pharmacokinetic (PBPK) modeling is another methodology that shows promise in predicting drug behavior, including potential exposure in specific populations. fda.govresearchgate.net While the development of a comprehensive PBPK model for this compound requires specific input parameters like tissue-to-plasma concentration ratios, which can be challenging to determine experimentally, PBPK models offer the possibility of scaling up and predicting human pharmacokinetics. gu.se

Studies have utilized population PK modeling to assess the impact of factors like food on this compound absorption. scispace.com A population PK model was established to describe the highly variable, multiple-peak absorption phase and the less variable disposition phase of this compound exposure in adult patients with chronic Chagas disease. scispace.com This model incorporated two parallel transit compartment absorption model (TCAM) components to characterize the absorption process, noting that food affected the amount absorbed via these components. scispace.com

Population pharmacokinetic modeling has also been applied to pediatric patients to evaluate exposure based on age and body weight-based dosing scenarios. researchgate.net These models can predict steady-state exposure based on single-dose simulations, assuming linear pharmacokinetics over time. researchgate.net

Pharmacokinetic modeling and simulation methodologies provide valuable tools for expanding the understanding of this compound disposition, evaluating the impact of various factors on exposure, and informing dosing strategies, particularly in diverse patient populations.

Molecular Basis of Nifurtimox Resistance in Trypanosomes

Resistance to this compound in trypanosomes is primarily linked to alterations in the parasite's ability to metabolize the drug. As a prodrug, this compound requires reductive activation to exert its cytotoxic effects. This activation is largely carried out by a specific enzyme within the parasite.

Cross-Resistance Patterns with Other Nitroheterocyclic Compounds

A significant consequence of NTR-mediated resistance is the observation of cross-resistance between this compound and other nitroheterocyclic compounds that are also activated by this enzyme. Studies have consistently shown that this compound-resistant trypanosomes are cross-resistant to benznidazole, another frontline drug for Chagas disease, as both are activated by the same type I NTR nih.govresearchgate.netnih.govcambridge.orgcapes.gov.brredalyc.org.

In T. brucei, this compound-resistant parasites have demonstrated cross-resistance to fexinidazole, a nitroimidazole currently used for HAT treatment, both in vitro and in vivo oup.comnih.gov. This reciprocal cross-resistance between this compound and fexinidazole has important implications for treatment strategies nih.gov.

The extent of cross-resistance can vary. For instance, T. brucei selected for resistance to this compound showed approximately 6-fold resistance to this compound and around 11-fold resistance to fexinidazole in one study oup.com. Conversely, fexinidazole-resistant lines were about 10-fold more resistant to this compound nih.gov.

Table 1: Cross-Resistance in Trypanosoma brucei Resistant Clones

Note: Data are approximate based on reported fold resistance values in selected studies oup.comnih.gov. WT = Wild Type.

Research into Strategies to Overcome or Mitigate Resistance

Given the challenge of drug resistance, research efforts are directed towards developing strategies to maintain the effectiveness of this compound and other nitroheterocyclic drugs.

Investigation into Gastrointestinal and Neurological Adverse Event Mechanisms

Gastrointestinal and neurological disturbances are among the most frequently reported adverse effects of nifurtimox nih.govlampit.com. While the precise mechanisms are not fully elucidated, the generation of reactive metabolites and oxidative stress are believed to play a role patsnap.compatsnap.com. Long-term use of this compound has been associated with an increased incidence of these effects wikipedia.orgportico.org. Common gastrointestinal adverse reactions include vomiting, abdominal pain, decreased appetite, and nausea nih.govlampit.com. Neurological effects can include headache, dizziness, insomnia, irritability, disorientation, and in rare cases, polyneuropathy, paresthesia, and peripheral neuritis nih.govwikipedia.org. Patients with a history of brain injury, seizures, psychiatric disease, or serious behavioral alterations may experience a worsening of their conditions while receiving this compound medicinenet.comlampit.comdrugs.com.

Research on Potential for Genotoxicity and Carcinogenicity in Preclinical Models

Studies have investigated the potential of this compound to induce genotoxicity and carcinogenicity in preclinical models nih.govlampit.com. This compound is considered to be genotoxic based on the weight of evidence from various in vitro and in vivo studies lampit.comfda.gov. It has shown positive results in Ames assays, inducing dose-dependent increases in mutants with and without S9 activation fda.gov. In vitro micronucleus assays have indicated that this compound is clastogenic in human lymphocytes fda.gov. In vivo studies in mice have also shown positive results for clastogenesis in micronucleus and sister chromatid exchange assays fda.gov. A study in pediatric patients with Chagas disease demonstrated a 13-fold increase in chromosomal aberrations lampit.combinasss.sa.crfda.gov.

Carcinogenicity has been observed in mice and rats treated chronically with nitrofuran agents structurally similar to this compound lampit.combinasss.sa.crfda.gov. While similar data have not been specifically reported for this compound in some contexts lampit.comfda.gov, other preclinical research has assessed its chronic toxicity and carcinogenicity nih.gov. An accelerated cancer bioassay in Wistar rats investigated this compound's potential initiating activity in organs like the liver, kidneys, urinary bladder, and mammary gland nih.gov. In this specific study, this compound, when given alone or followed by promoters, did not demonstrate chronic toxicity or carcinogenicity, and showed no neoplastic initiating activity in the studied organs nih.gov. However, it is not definitively known whether this compound is associated with carcinogenicity in humans lampit.combinasss.sa.crfda.gov.

Embryo-fetal Toxicity Research and Clinical Implications

Research in animal models has indicated that this compound can cause embryo-fetal toxicity lampit.comfda.govfda.govoup.com. Studies in pregnant mice, rats, and rabbits during organogenesis have shown associations with reduced fetal body weights in rodents and abortions, fetal death, and smaller litter sizes in rabbits at doses approximately equivalent to and 2 times the maximum recommended human dose lampit.comfda.govoup.com. Fetal malformations, specifically an increased incidence of a skeletal malformation (fusion of caudal vertebral bodies), were observed in rabbits at doses lower than the maximum recommended human dose drugs.comfda.govoup.com.

Based on these animal findings, this compound may cause fetal harm when administered to a pregnant woman fda.govfda.govoup.com. Due to the potential risk, pregnancy testing is recommended for females of reproductive potential prior to initiating treatment binasss.sa.crfda.gov. Effective contraception is advised for females of reproductive potential during treatment and for a period after the final dose binasss.sa.crfda.govoup.com. Similarly, due to the potential for genotoxicity, male patients with female partners of reproductive potential are advised to use condoms during treatment and for a period after the final dose binasss.sa.croup.com. While published postmarketing reports on this compound use during pregnancy are insufficient to definitively inform a drug-associated risk of birth defects and miscarriage, there are known risks to the fetus associated with Chagas disease itself fda.govfda.govoup.com. Treatment of chronic Chagas disease during pregnancy is generally not recommended due to the risk of embryofetal toxicity from this compound binasss.sa.croup.com.

Mechanistic and Clinical Studies of Hepatotoxicity

The mechanism by which this compound might cause liver injury is not fully understood nih.gov. This compound is a prodrug that is activated to a reactive metabolite by parasites, but this activation is less significant in human cells nih.gov. While this compound has many adverse effects that can limit therapy, clinically apparent liver injury has not been frequently associated with its use in recommended regimens for Chagas disease nih.gov. Multiple prospective controlled trials have not shown associations with elevations in aminotransferase or bilirubin levels or instances of clinically apparent liver injury nih.gov. Since the approval of this compound for American trypanosomiasis, there have been no individual reports of liver injury associated with its use nih.gov. The likelihood score for this compound being a cause of clinically apparent liver injury when used for Chagas disease is considered low nih.gov.

Understanding Hypersensitivity Reactions: Underlying Mechanisms

Cases of hypersensitivity reactions have been reported in patients receiving this compound medicinenet.comdrugs.combinasss.sa.crfda.gov. These reactions could be directly induced by this compound or triggered by an immune response related to the underlying Chagas disease during treatment medicinenet.comdrugs.combinasss.sa.crfda.gov. Hypersensitivity reactions can manifest with symptoms such as hypotension, angioedema (including laryngeal or facial edema), dyspnea, pruritus, rash, or other severe skin reactions medicinenet.comdrugs.combinasss.sa.crfda.gov.

Impact of this compound on Specific Organ System Function: Research Insights (e.g., Liver Enzymes)

Research insights into the impact of this compound on specific organ system function include observations related to liver enzymes. As mentioned previously, multiple prospective controlled trials have not associated this compound therapy with elevations in aminotransferase or bilirubin levels nih.gov. This suggests that, at recommended doses for Chagas disease, this compound does not commonly lead to significant alterations in standard liver enzyme markers indicative of overt liver injury nih.gov.

Here is a summary of some preclinical findings regarding this compound toxicity:

Development of Age-Appropriate and Patient-Friendly Formulations (e.g., Dispersible Tablets)

Historically, nifurtimox was primarily available as a 120 mg tablet, which posed challenges for accurate, weight-adjusted dosing, especially in children. Manual division of these tablets could lead to inaccurate dosing. plos.orgdndial.orgthemedicinemaker.com To address this, a new formulation of this compound tablets has been developed and is available in two dose strengths: 30 mg and 120 mg. plos.orgnih.gov

These new tablets feature a functional score line, facilitating accurate division. plos.orgnih.gov Furthermore, the new formulation is designed to be rapidly and easily dispersible in water, forming a slurry. plos.orgnih.govnih.gov This dispersibility is particularly beneficial for patients who have difficulty swallowing tablets, including young children and infants weighing at least 2.5 kg. plos.orgnih.govasm.org The development of these divisible and dispersible tablets allows for more accurate body-weight-based and age-appropriate dosing. plos.orgnih.gov

Studies have confirmed the efficacy and safety of these new pediatric formulations administered in age- and weight-adjusted regimens. asm.orgplos.orgresearchgate.net For instance, a prospective study (CHICO) evaluated the new formulations in children aged 0 to 17 years. asm.orgplos.org The study utilized the divisible, dispersible 30 mg and 120 mg tablets. plos.org

Research into Novel Drug Delivery Systems

Beyond conventional tablets, research has explored novel drug delivery systems for this compound to potentially improve its pharmacokinetic profile, reduce dosing frequency, and enhance efficacy, particularly in the chronic phase of Chagas disease where current treatments have variable efficacy. mdpi.comnih.govresearchgate.net

Bioequivalence and Bioavailability Studies of New Formulations

Bioequivalence and bioavailability studies are crucial in evaluating new drug formulations to ensure they perform comparably to existing approved formulations. For the new this compound tablet formulation, pharmacokinetic studies have been conducted in adult patients with Chagas disease. plos.orgnih.govresearchgate.net

One study compared the biopharmaceutical features of the new 30 mg tablet with the existing 120 mg tablet, demonstrating that four 30 mg tablets of the new formulation were bioequivalent to one existing 120 mg tablet. plos.orgnih.govresearchgate.net Another study confirmed that the bioavailability of the new 30 mg formulation remained unaffected whether administered as a tablet or as an aqueous slurry. plos.orgnih.govresearchgate.net The dissolution profile of the new tablet formulation has also been confirmed to comply with regulatory specifications. researchgate.net

The FDA's guidance for generic this compound also recommends conducting two in vivo bioequivalence studies with pharmacokinetic endpoints: one under fasting conditions and one under fed conditions, typically using the 120 mg strength in healthy subjects. fda.gov

Impact of Formulation on Therapeutic Efficacy and Patient Tolerability

The development of new this compound formulations, particularly the age-appropriate and patient-friendly tablets, has a significant impact on therapeutic efficacy and patient tolerability. The availability of divisible and dispersible tablets in multiple strengths facilitates accurate, weight-adjusted dosing, which is crucial for achieving optimal drug exposure and efficacy, especially in the pediatric population. plos.orgnih.govnih.gov Accurate dosing helps ensure that patients receive the correct amount of medication needed to effectively treat the infection.

Furthermore, the dispersible nature of the new formulation improves ease of administration, particularly for young children or those with swallowing difficulties, potentially leading to improved patient adherence to the treatment regimen. plos.orgnih.govnih.gov Improved adherence is critical for the successful treatment of Chagas disease, which requires a prolonged course of medication.

Research into novel delivery systems like SEDDS and PCL implants also aims to enhance therapeutic efficacy and tolerability. SEDDS formulations have shown enhanced anti-T. cruzi activity in vitro. mdpi.comnih.govresearchgate.netnih.gov PCL implants have demonstrated sustained efficacy and improved tolerability in animal models, delivering a prolonged effect and potentially improving adherence by reducing the frequency of administration. mdpi.comnih.govresearchgate.netnih.gov

Studies have evaluated the efficacy of different this compound regimens using the new formulations. The CHICO study confirmed the efficacy of age- and weight-adjusted 60-day treatment with this compound in pediatric patients, showing a superior serological response compared to historical placebo. asm.orgplos.orgresearchgate.netplos.org

Genomic and Proteomic Approaches in Mechanism of Action and Resistance Studies

Genomic and proteomic studies play a vital role in unraveling the molecular mechanisms underlying nifurtimox's action against parasites like Trypanosoma cruzi and Trypanosoma brucei, as well as investigating the development of drug resistance. Comparative genomic hybridization assays (CGH) using DNA microarrays have successfully identified karyotypic alterations in drug-resistant parasites. mdpi.com Experimentally selected resistant strains, often obtained through in vitro selection under increasing drug pressure, are central to these studies. mdpi.com

Transcriptomic and proteomic analyses compare sensitive and resistant parasite strains to identify differentially expressed genes and proteins. plos.orgresearchgate.net These "omics" strategies contribute complementary insights into the mode of action (MoA) and mode of resistance (MoR). mdpi.com For instance, studies have implicated the enzyme nitroreductase I (NTRI) as a primary factor in resistance to both benznidazole and this compound in T. cruzi, with loss of function due to gene deletion or mutations leading to reduced prodrug activation. plos.org However, research also indicates that resistance can be a multigenic process involving mechanisms independent of NTRI. plos.orgresearchgate.net Transcriptome analysis has revealed the regulation of various genes with diverse functions and metabolic pathways in resistant parasites. researchgate.net Proteomic studies have been utilized to understand parasite differentiation, identify biomarkers, and elucidate drug MoA/MoR, often employing techniques like 2D differential gel electrophoresis (2D-DIGE), stable isotope labeling of amino acids in cell culture (SILAC), or isobaric tags for relative and absolute quantitation (iTRAQ) to compare protein expression. mdpi.com

Advanced Spectroscopic and Chromatographic Techniques in Metabolism Research

Advanced spectroscopic and chromatographic techniques are indispensable for the analysis of this compound and its metabolites in various matrices, including biological samples. These methods enable the separation, identification, and quantification of the parent drug and its transformation products, providing crucial data for understanding its metabolism and disposition.

Techniques such as Gas Chromatography coupled to Mass Spectrometry (GC-MS), Liquid Chromatography coupled to Mass Spectrometry (LC-MS), and Capillary Electrophoresis coupled to Mass Spectrometry (CE-MS) are widely used in metabolomic investigations. sysrevpharm.org High-resolution mass spectrometry techniques like Time-of-Flight, Orbitrap, and FT-ICR enhance the sensitive detection and identification of hundreds of metabolites. monash.edu Coupling MS with chromatographic separation techniques further improves analytical capabilities. monash.edu Reversed-phase chromatography is commonly applied in global metabolite profiling studies, although it may be less suitable for highly polar compounds. monash.edu Nuclear Magnetic Resonance (NMR) spectroscopy is another valuable tool for metabolite analysis, offering complementary information to mass spectrometry. sysrevpharm.orgmonash.edu

Untargeted metabolomics analysis of this compound treatment has confirmed its metabolic activation by nitroreductase to a reactive intermediate and revealed changes in endogenous metabolites involved in nucleotide and carbohydrate metabolism in parasites. monash.eduplos.org Spectroscopic methods like FT-IR, FT-Raman, and UV-vis spectroscopy, combined with theoretical calculations, are used to characterize the structural and vibrational properties of this compound. ejtas.com

In Silico Modeling and Computational Chemistry Applications

In silico modeling and computational chemistry play a significant role in studying this compound, particularly in understanding its interactions with biological targets, predicting its properties, and designing potential new therapeutic agents. Techniques such as molecular docking are used to investigate the binding affinity of compounds to specific protein targets in parasites. chemrxiv.org For example, in silico studies have explored the interaction of potential new compounds with trypanothione reductase, an enzyme in T. cruzi. chemrxiv.org

Computational chemistry, including ligand-based drug design (LBDD), allows for the screening of large chemical libraries to identify molecules with potential anti-parasitic activity and favorable properties, potentially with reduced toxicity compared to existing drugs like this compound and benznidazole. chemrxiv.org Density Functional Theory (DFT) calculations are employed to study the electronic structure and physicochemical properties of this compound and its analogs, providing insights into their reactivity and stability in different environments. ejtas.com These computational approaches complement experimental studies by providing theoretical frameworks and predictions that can guide further research into this compound's mechanism and the development of improved treatments.

Population Pharmacokinetic (PopPK) Modeling and Simulations

Population pharmacokinetic (PopPK) modeling is a powerful tool used to characterize the pharmacokinetic properties of this compound in diverse patient populations, such as adults and children with Chagas disease. nih.govresearchgate.net These models analyze pooled data from multiple individuals to understand the variability in drug exposure and identify factors influencing pharmacokinetics. nih.govresearchgate.netiddo.org

PopPK studies on this compound have aimed to confirm clinical dosing regimens, particularly in pediatric patients, by assessing whether age- and weight-based dosing achieves comparable exposure to effective doses in adults. nih.govresearchgate.net Significant covariates influencing this compound pharmacokinetics identified through PopPK modeling include food intake, tablet formulation, study-specific factors, body weight, and age. nih.govresearchgate.net For instance, studies have shown that children older than 2 years may have a higher apparent clearance of this compound compared to adults. nih.govresearchgate.net

PopPK modeling and simulations can also be used to estimate potential infant exposure to this compound through breast milk, providing valuable data for informing treatment decisions in lactating mothers. e-lactancia.org Simulations allow for the prediction of drug exposure under different dosing scenarios and in various subpopulations. researchgate.nete-lactancia.org

Quantitative Polymerase Chain Reaction (qPCR) for Parasite Load Assessment

Quantitative Polymerase Chain Reaction (qPCR) is a sensitive molecular technique widely used to detect and quantify parasite DNA in biological samples, making it a crucial tool for assessing parasite load in patients with Chagas disease. nih.govplos.orgnih.govfrontiersin.org qPCR directed at repetitive sequences in the parasite genome, such as kinetoplast DNA (kDNA) or satellite DNA (Sat DNA), offers high sensitivity for detecting T. cruzi. nih.gov

qPCR is considered a preferable alternative to traditional parasitological methods for determining parasitic load after treatment and evaluating treatment efficacy. nih.gov Studies have demonstrated that this compound treatment leads to a substantial decrease in the frequency of T. cruzi-positive qPCR results, indicating its parasiticidal effects. plos.org Clearance of parasitemia measured by qPCR has been observed in the majority of this compound-treated patients. plos.org

While qPCR is a valuable tool, the clinical sensitivity in the chronic phase of Chagas disease can vary, and fluctuations in PCR positivity can occur due to low parasitic burden. frontiersin.org Serial sampling can be employed to increase the sensitivity of PCR for detecting parasitic loads in chronically infected patients. frontiersin.org qPCR also plays a role in monitoring parasite load in specific patient populations, such as those co-infected with HIV. nih.gov

Development and Validation of Serological Assays and Biomarkers for Treatment Efficacy

Evaluating the efficacy of this compound treatment, particularly in the chronic phase of Chagas disease, is challenging due to the slow decline of anti-T. cruzi antibodies after successful treatment. Conventional serological tests can remain positive for years or even decades. scielo.brscienceopen.com This has driven the search for more sensitive and earlier biomarkers of treatment response.

The development and validation of new serological assays and biomarkers are crucial for the early monitoring of treatment efficacy. Studies have explored the use of enzyme-linked immunosorbent assays (ELISAs) utilizing specific recombinant T. cruzi antigens, such as the flagellar calcium-binding protein F29 (ELISA F29). scielo.brnih.gov Research suggests that seronegativity to certain antigens, like F29, may occur earlier than conventional seroconversion, indicating their potential as early biomarkers of treatment success in children. nih.gov

Elucidation of Remaining Unclear Mechanistic Aspects of Action and Toxicity

The precise mechanisms of action and toxicity of nifurtimox are not yet fully elucidated, despite over 40 years of research drugbank.compnas.orgacs.org. It is understood that this compound acts as a prodrug, requiring activation by T. cruzi nitroreductase enzymes to produce reactive metabolites nih.govdrugbank.compnas.orgacs.org. These metabolites are thought to induce cytotoxic effects, including oxidative damage through the generation of radical species, leading to thiol depletion, DNA damage, and lipid peroxidation nih.gov. Inhibition of parasite dehydrogenase activity is also a purported mode of action that warrants further investigation drugbank.com. While its antiparasitic activity is attributed to biotransformation catalyzed by nitroreductases, the specific pathways and enzymes involved in this compound metabolism in preclinical models and humans remain largely unknown acs.org. The potential toxicological impact of certain metabolic pathways, such as those involving thiol-containing macromolecules and covalent binding, also remains unclear acs.org. Research into the structural and mechanistic aspects of its unusual metabolism is ongoing to gain a more complete understanding acs.org.

Development of Improved and Early Efficacy Markers for Chronic Chagas Disease

Determining the success of antitrypanosomal therapy for Chagas disease, particularly in the chronic phase, is challenging because seropositivity can persist for a significant time after successful treatment frontiersin.orgresearchgate.net. Seroconversion to negative results by two or more conventional serologic tests is the currently accepted measure of efficacy, but this can take a long time and is influenced by the duration of T. cruzi infection frontiersin.org. There is a lack of validated, sensitive, specific, and easy-to-use markers for the early monitoring of antitrypanosomal treatment efficacy frontiersin.orgresearchgate.net. While seroreduction, defined as at least a 20% reduction in mean optical density measured by two conventional ELISA tests, has been used as a surrogate parameter for efficacy in pediatric trials, there is no specific guidance for the industry on how to establish the effectiveness of Chagas disease drugs frontiersin.orgresearchgate.net. Further research is needed to identify and validate early efficacy markers that can provide a more timely assessment of treatment response in chronic Chagas disease frontiersin.orgresearchgate.net. Studies like the CHICO trial are providing valuable information regarding biomarkers of treatment response nih.govplos.org.

Strategies for Addressing and Preventing Drug Resistance in Endemic Settings

Drug resistance is a significant concern for Chagas disease treatment, and strategies are needed to address and prevent its emergence and spread in endemic settings nih.gov. While widespread and indiscriminate use of this compound and benznidazole has not occurred, treatment failures are reported, and the extent to which these are due to acquired resistance versus non-compliance is unclear nih.gov. Down-regulation of the NADH-dependent, mitochondrially localized, bacterial-like type I nitroreductase (NTR) in trypanosomes has been identified as a mechanism for resistance to nitroheterocyclic drugs like this compound and benznidazole pnas.orgacs.org. Loss of a single copy of the gene encoding this enzyme in T. cruzi can lead to significant cross-resistance to a range of nitroheterocyclic compounds pnas.org. The potential for drug resistance through such a simple mechanism has important implications, especially as this compound is used in combination therapies for other trypanosomiasis pnas.org. Research into the genetic and molecular basis of resistance in different T. cruzi strains is crucial nih.gov.

Exploration and Evaluation of New Therapeutic Combinations

The exploration and evaluation of new therapeutic combinations involving this compound is an important area for future research researchgate.netresearchgate.netplos.orgfrontiersin.org. This compound is already part of the this compound-eflornithine combination therapy (NECT) for second-stage Trypanosoma brucei gambiense HAT, which has shown comparable cure rates to eflornithine monotherapy with lower side effects taylorandfrancis.comacs.orgmdpi.com. NECT allowed for a reduction in the dose and duration of eflornithine infusion taylorandfrancis.com. While NECT has been a significant achievement, its administration can be challenging in low-resource settings due to the need for intravenous infusion and hospitalization researchgate.nettaylorandfrancis.comacs.org. Exploring new oral combinations or fixed-dose combinations could improve treatment accessibility and adherence acs.org. Research into combining this compound with other novel or existing compounds with different mechanisms of action could potentially improve efficacy, reduce treatment duration, and mitigate the development of resistance in both Chagas disease and HAT researchgate.netresearchgate.netplos.orgfrontiersin.org.

Investigation into Broader Therapeutic Applications Beyond Trypanosomiasis

While primarily known for its use in trypanosomiasis, there is ongoing investigation into broader therapeutic applications of this compound researchgate.nettandfonline.com. The cytotoxic effects of this compound on neuroblastoma cell lines and its possible anti-tumor activity in neuroblastoma patients have been reported researchgate.net. Although the detailed mechanism of its anti-tumor activity remains unclear, even in its application against trypanosomes, preclinical studies and early phase clinical trials have shown that this compound can inhibit neuroblastoma cell growth and demonstrate responses both as a single agent and in combination with chemotherapy researchgate.net. A phase II study on the efficacy of this compound in patients with relapsed or refractory neuroblastoma and medulloblastoma has been conducted researchgate.net. Further research is needed to fully understand the potential of this compound in treating cancers and other conditions beyond parasitic infections researchgate.nettandfonline.comresearchgate.net.

Long-Term Safety and Pharmacovigilance Studies in Diverse Patient Populations

Despite its long history of use, published data on the long-term safety and tolerance of this compound, particularly in adults, are scarce nih.govoup.comoup.com. While studies support the safety of this compound for Chagas disease treatment in children, with adverse drug reactions occurring less frequently than in adults, more data are needed across diverse patient populations, including different age groups, those with comorbidities, and pregnant women (although currently contraindicated) nih.govplos.orgtandfonline.comnih.govoup.comdndi.orgresearchgate.net. Long-term pharmacovigilance studies are crucial to monitor for rare or delayed adverse events and to better understand the drug's safety profile in real-world settings tandfonline.com. Retrospective studies and ongoing follow-up of clinical trial participants are contributing to this understanding plos.orgresearchgate.netasm.orgnih.gov.

Research into Optimization of Treatment Regimens and Patient Adherence Strategies

Research into optimizing treatment regimens and strategies to improve patient adherence is essential to maximize the effectiveness of this compound nih.govplos.orgdndi.org. The standard treatment duration for Chagas disease is often long (e.g., 60 days), which can contribute to poor compliance and high dropout rates due to adverse effects dndi.orgmdpi.com. Investigating shorter treatment durations or lower doses that maintain efficacy while improving tolerability is an important area of research nih.govplos.orgmdpi.com. The development of new, divisible tablet formulations in different dose strengths has improved dosing accuracy, particularly for young children, which can enhance safety and adherence nih.govdndi.org. Strategies to support patient adherence, such as counseling, education, and simplified regimens, are also critical, especially in resource-limited settings dndi.orgmdpi.com.