Evaluation of In Vitro Cytochrome P450 Inhibition and In Vitro Fate of Structurally Diverse N-Oxide Metabolites: Case Studies with Clozapine, Levofloxacin, Roflumilast, Voriconazole and Zopiclone

[Therapy of mental disorders in patients with hematological malignancies]

OBJECTIVE

To assess the possibilities of therapy with minimal effective doses (MED) of psychotropic drugs for mental disorders (MD) that manifest during the treatment of hematological malignancies (HM).

MATERIAL AND METHODS

A prospective study was conducted at the National Medical Research Center for Hematology of the Russian Ministry of Health (Moscow), which included 204 (39.4%) men and 314 (60.6%) women (518 patients in total), aged 17 to 83 years (median 45 years), with various HM, in which the manifestation of MD occurred during the treatment of the underlying disease. To minimize the side-effects of psychotropic drugs and given the relatively mild level of MD, psychopharmacotherapy of patients was carried out mainly at MED. The severity of MD, manifested in patients, was assessed by the illness severity scale of the Clinical Global Impression (CGI) scale, and the effectiveness of the treatment was assessed by the improvement scale (CGI-I).

RESULTS

Mainly mild (188, 36%) and moderately pronounced (270, 52%) MD were noted in patients with HM during the treatment of the underlying disease. Severe psychopathological disorders (60, 12%) were observed much less often. Because of psychopharmacotherapy with MED, patients experienced a very significant (97, 19%) and significant improvement (354, 68%) of their mental state, less often the improvement was regarded as minimal (67, 13%). Therefore, almost all patients showed a stable relief of MD; in 87% (95% CI 84-90) of patients, this improvement was significant.

CONCLUSION

The tactics of treatment MD that manifest in patients with HM with MED of psychotropic drugs turned out to be therapeutically effective according to the results of the assessment on CGI scales.

A Single-center, Open-label, Parallel Control Study Comparing the Pharmacokinetics and Safety of a Single Oral Dose of Roflumilast and Its Active Metabolite Roflumilast N-oxide in Healthy Chinese and Caucasian Volunteers

Roflumilast is a phosphodiesterase-4 inhibitor which treats chronic obstructive pulmonary disease (COPD). Roflumilast N-oxide is the major metabolite of roflumilast with a similar mechanism of action to roflumilast. Although racial differences in roflumilast drug disposition have been observed, the necessity of dose adjustment is subject to debate. This study compares the pharmacokinetics of a single 500 μg dose of roflumilast in healthy Chinese and Caucasian subjects under uniform conditions. Chinese subjects were found to have longer t_1/2 and higher AUC_0-t and C_max than Caucasian subjects. The point estimates on the geometric mean of AUC_0-t in Chinese subjects were 22% higher for roflumilast and 46% higher for roflumilast N-oxide. Point estimates on the geometric mean of C_max were 9% and 24% higher for roflumilast and roflumilast N-oxide, respectively. Total phosphodiesterase-4 (PDE4) inhibitory (tPDE4i) activity, a theoretical parameter that describes the combined contribution to PDE4 inhibitory activity of roflumilast and roflumilast N-oxide, was 44% higher in Chinese subjects than in Caucasian subjects. With about a 10-fold higher plasma AUC compared to the parent roflumilast and a much longer observed half-life, roflumilast N-oxide has been estimated to contribute about 90% of tPDE4i, with 10% attributed to the parent compound roflumilast. Following body weight normalization, these figures were lower but remained significant. Safety analysis showed signs of reduced tolerance or different pharmacodynamic response to roflumilast in Chinese recipients than in Caucasians. Our results suggest that Chinese patients should receive a dose of roflumilast lower than 500 μg daily during future clinical trials.

Roles of selected non-P450 human oxidoreductase enzymes in protective and toxic effects of chemicals: review and compilation of reactions

This is an overview of the metabolic reactions of drugs, natural products, physiological compounds, and other (general) chemicals catalyzed by flavin monooxygenase (FMO), monoamine oxidase (MAO), NAD(P)H quinone oxidoreductase (NQO), and molybdenum hydroxylase enzymes (aldehyde oxidase (AOX) and xanthine oxidoreductase (XOR)), including roles as substrates, inducers, and inhibitors of the enzymes. The metabolism and bioactivation of selected examples of each group (i.e., drugs, "general chemicals," natural products, and physiological compounds) are discussed. We identified a higher fraction of bioactivation reactions for FMO enzymes compared to other enzymes, predominately involving drugs and general chemicals. With MAO enzymes, physiological compounds predominate as substrates, and some products lead to unwanted side effects or illness. AOX and XOR enzymes are molybdenum hydroxylases that catalyze the oxidation of various heteroaromatic rings and aldehydes and the reduction of a number of different functional groups. While neither of these two enzymes contributes substantially to the metabolism of currently marketed drugs, AOX has become a frequently encountered route of metabolism among drug discovery programs in the past 10-15 years. XOR has even less of a role in the metabolism of clinical drugs and preclinical drug candidates than AOX, likely due to narrower substrate specificity.

ZY12201, A Potent TGR5 Agonist: Identification of a Novel Pan CYP450 Inhibitor Tool Compound for In-Vitro Assessment

BACKGROUND

Identification of clinical drug-drug interaction (DDI) risk is an important aspect of drug discovery and development owing to poly-pharmacy in present-day clinical therapy. Drug metabolizing enzymes (DME) plays important role in the efficacy and safety of drug candidates. Hence evaluation of a New Chemical Entity (NCE) as a victim or perpetrator is very crucial for DDI risk mitigation. ZY12201 (2-((2-(4-(1H-imidazol-1-yl) phenoxy) ethyl) thio)-5-(2-(3, 4- dimethoxy phenyl) propane-2-yl)-1-(4-fluorophenyl)-1H-imidazole) is a novel and potent Takeda-G-protein-receptor-5 (TGR-5) agonist. ZY12201 was evaluated in-vitro to investigate the DDI liabilities.

OBJECTIVE

The key objective was to evaluate the CYP inhibition potential of ZY12201 for an opportunity to use it as a tool compound for pan CYP inhibition activities.

METHOD

In-vitro drug metabolizing enzymes (DME) inhibition potential of ZY12201 was evaluated against major CYP isoforms (1A2, 2B6, 2C8, 2C9, 2C19, 2D6, 2E1, and 3A4/5), aldehyde oxidase (AO), monoamine oxidase (MAO), and flavin-containing monooxygenase (FMO in human liver cytosol/mitochondrial preparation/ microsomes using probe substrates and Liquid Chromatography with tandem mass spectrometry (LC-MS-MS) method.

RESULTS

The study conducted on ZY12201 at 100 µM ZY12201 was found to reduce the metabolism of vanillin (AO probe substrate), tryptamine (MAO probe substrate), and benzydamine (FMO probe substrate) by 49.2%, 14.7%, and 34.9%, respectively. ZY12201 Ki values were 0.38, 0.25, 0.07, 0.01, 0.06, 0.02, 7.13, 0.03 and 0.003 μM for CYP1A2, CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2D6, CYP2E1, CYP3A4/5 (substrate: testosterone) and CYP3A4/5 (substrate: midazolam), respectively. Time-dependant CYP inhibition potential of ZY12201 was assessed against CYP1A2, CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2D6, CYP2E1, and CYP3A4/5 and no apparent IC50 shift was observed.

CONCLUSIONS

ZY12201, at 100 µM concentration showed low inhibition potential of AO, MAO, and FMO. ZY12201 was found as a potent inhibitor of CYP1A2, 2B6, 2C8, 2C9, 2C19, 2D6, and 3A4/5 while moderately inhibits to CYP2E1. Inhibition of CYP1A2, CYP2B6, CYP2C19, and CYP2E1 by ZY12201 was competitive, while inhibition of CYP2C8, CYP2C9, CYP2D6, and CYP3A4/5 was of mixed-mode. ZY12201 is a non-time-dependent inhibitor of CYP1A2, CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2D6, CYP2E1, CYP3A4/5. In summary, the reported Ki values unequivocally support that ZY12201 has a high potential to inhibit all major CYP isoforms. ZY12201 can be effectively used as a tool compound for in-vitro evaluation of CYP-based metabolic contribution to total drug clearance in the lead optimization stage of Drug Discovery Research.

Towards the Elucidation of the Pharmacokinetics of Voriconazole: A Quantitative Characterization of Its Metabolism

The small-molecule drug voriconazole (VRC) shows a complex and not yet fully understood metabolism. Consequently, its in vivo pharmacokinetics are challenging to predict, leading to therapy failures or adverse events. Thus, a quantitative in vitro characterization of the metabolism and inhibition properties of VRC for human CYP enzymes was aimed for. The Michaelis-Menten kinetics of voriconazole N-oxide (NO) formation, the major circulating metabolite, by CYP2C19, CYP2C9 and CYP3A4, was determined in incubations of human recombinant CYP enzymes and liver and intestine microsomes. The contribution of the individual enzymes to NO formation was 63.1% CYP2C19, 13.4% CYP2C9 and 29.5% CYP3A4 as determined by specific CYP inhibition in microsomes and intersystem extrapolation factors. The type of inhibition and inhibitory potential of VRC, NO and hydroxyvoriconazole (OH-VRC), emerging to be formed independently of CYP enzymes, were evaluated by their effects on CYP marker reactions. Time-independent inhibition by VRC, NO and OH-VRC was observed on all three enzymes with NO being the weakest and VRC and OH-VRC being comparably strong inhibitors of CYP2C9 and CYP3A4. CYP2C19 was significantly inhibited by VRC only. Overall, the quantitative in vitro evaluations of the metabolism contributed to the elucidation of the pharmacokinetics of VRC and provided a basis for physiologically-based pharmacokinetic modeling and thus VRC treatment optimization.

Efficacy, Safety, and Drug–Drug Interactions for Insomnia Therapy in COVID-19 Patients

Coronavirus disease-19 (COVID-19) is a systemic viral infection. COVID-19 patients show diverse clinical presentations ranging from asymptomatic, mild symptoms to severe symptoms characterized by severe respiratory distress. Sleep disorders or insomnia is one of the psychiatric problems that arise during the COVID-19 pandemic. The term used to define this particular insomnia is coronasomnia or COVID-19 insomnia. Data show that the prevalence of this problem is increasing, especially in the confirmed COVID-19 patient group. Anti-insomnia drugs such as hypnotics, sedatives, and anxiolytics are the easiest option. As with drugs generally, anti-insomnia drugs are associated with various safety issues, especially in people with COVID-19. Therefore, their use may be hazardous. The literature review aims to make health practitioners aware of the anti-insomnia drugs that have the best efficacy and safety issues that are clinically relevant from the use of anti-insomnia drugs and the interactions of anti-insomnia drugs with various drugs used in the treatment of COVID-19. The articles were explored on PubMed and Cochrane Library, whereas the drug–drug interactions between the anti-insomnia and COVID-19 drugs were searched on Drugs.com Interaction Checker and Lexiomp-interact. Overall anti-insomnia drugs have efficacy in improving sleep parameters. Orexin receptor antagonist drugs have good efficacy in increasing WASO, LPS, and SE with an acceptable safety profile. Meanwhile, the combination of zolpidem, lorazepam, and diphenhydramine improved TST parameters better than other drugs. Side effects such as drowsiness and dizziness were among the most commonly reported effects. Therefore, attention and monitoring of the use of anti-insomnia drugs in COVID-19 patients need to be carried out by considering the side effects and interactions that are very risky.

Impact of CYP2C19 genotype on voriconazole exposure and effect of voriconazole on the activity of CYP3A in patients with haematological malignancies

Voriconazole (VRC) is a first-line drug for the treatment of invasive fungal infections (IFIs) and an inhibitor of CYP3A activity. The aims of this study are to investigate the influence of related factors on the plasma concentration of voriconazole and the effect of voriconazole on the activity of CYP3A in patients with haematological malignancies.A total of 89 patients received an initial dose of 6 mg/kg followed by 4 mg/kg every 12 h were included in the study. Blood samples were collected before and 2 h after administration for subsequent testing and for the extraction of DNA samples. Voriconazole and voriconazole N-oxide in the plasma were detected by LC-MS/MS. The effect of voriconazole on CYP3A activity was evaluated by the ratio of the endogenous biomarkers 6β-hydroxycortisol and cortisol.During the study period, the overall incidence of adverse reactions was 33.6% (with no deaths). The metabolite type of CYP2C19 and combined use of CYP2C19 enzyme inhibitors both had a significant impact on voriconazole exposure. Voriconazole has a long-lasting and potent inhibitory effect on CYP3A activity. The exposure of CYP3A substrate in combination with metabolic enzyme inhibitors voriconazole could increase. Therefore, the combination uses with voriconazole need to be considered carefully and assessed adequately.

Physiologically Based Pharmacokinetic Modeling of Bupropion and Its Metabolites in a CYP2B6 Drug-Drug-Gene Interaction Network

The noradrenaline and dopamine reuptake inhibitor bupropion is metabolized by CYP2B6 and recommended by the FDA as the only sensitive substrate for clinical CYP2B6 drug-drug interaction (DDI) studies. The aim of this study was to build a whole-body physiologically based pharmacokinetic (PBPK) model of bupropion including its DDI-relevant metabolites, and to qualify the model using clinical drug-gene interaction (DGI) and DDI data. The model was built in PK-Sim® applying clinical data of 67 studies. It incorporates CYP2B6-mediated hydroxylation of bupropion, metabolism via CYP2C19 and 11β-HSD, as well as binding to pharmacological targets. The impact of CYP2B6 polymorphisms is described for normal, poor, intermediate, and rapid metabolizers, with various allele combinations of the genetic variants CYP2B6*1, *4, *5 and *6. DDI model performance was evaluated by prediction of clinical studies with rifampicin (CYP2B6 and CYP2C19 inducer), fluvoxamine (CYP2C19 inhibitor) and voriconazole (CYP2B6 and CYP2C19 inhibitor). Model performance quantification showed 20/20 DGI ratios of hydroxybupropion to bupropion AUC ratios (DGI AUCHBup/Bup ratios), 12/13 DDI AUCHBup/Bup ratios, and 7/7 DDGI AUCHBup/Bup ratios within 2-fold of observed values. The developed model is freely available in the Open Systems Pharmacology model repository.

Differential inhibition of human CYP2C8 and molecular docking interactions elicited by sorafenib and its major N-oxide metabolite

The tyrosine kinase inhibitor sorafenib (SOR) is being used increasingly in combination with other anticancer agents like paclitaxel, but this increases the potential for drug toxicity. SOR inhibits several human CYPs, including CYP2C8, which is a major enzyme in the elimination of oncology drugs like paclitaxel and imatinib. It has been reported that CYP2C8 inhibition by SOR in human liver microsomes is potentiated by NADPH-dependent biotransformation. This implicates a SOR metabolite in enhanced inhibition, although the identity of that metabolite is presently unclear. The present study evaluated the capacity of the major N-oxide metabolite of SOR (SNO) to inhibit CYP2C8-dependent paclitaxel 6α-hydroxylation. The IC₅₀ of SNO against CYP2C8 activity was found to be 3.7-fold lower than that for the parent drug (14 μM versus 51 μM). In molecular docking studies, both SOR and SNO interacted with active site residues in CYP2C8, but four additional major hydrogen and halogen bonding interactions were identified between SNO and amino acids in the B-B' loop region and helixes F' and I that comprise the catalytic region of the enzyme. In contrast, the binding of both SOR and SNO to active site residues in the closely related human CYP2C9 enzyme was similar, as were the IC₅₀s determined against CYP2C9-mediated losartan oxidation. These findings suggest that the active metabolite SNO could impair the elimination of coadministered drugs that are substrates for CYP2C8, and mediate toxic adverse events, perhaps in those individuals in whom SNO is formed extensively.

Predictors of Adverse Events and Determinants of the Voriconazole Trough Concentration in Kidney Transplantation Recipients

Voriconazole is the mainstay for the treatment of invasive fungal infections in patients who underwent a kidney transplant. Variant CYP2C19 alleles, hepatic function, and concomitant medications are directly involved in the metabolism of voriconazole. However, the drug is also associated with numerous adverse events. The purpose of this study was to identify predictors of adverse events using binary logistic regression and to measure its trough concentration using multiple linear modeling. We conducted a prospective analysis of 93 kidney recipients cotreated with voriconazole and recorded 213 trough concentrations of it. Predictors of the adverse events were voriconazole trough concentration with the odds ratios (OR) of 2.614 (P = 0.016), cytochrome P450 2C19 (CYP2C19), and hemoglobin (OR 0.181, P = 0.005). The predictive power of these three factors was 91.30%. We also found that CYP2C19 phenotypes, hemoglobin, platelet count, and concomitant use of ilaprazole had quantitative relationships with voriconazole trough concentration. The fit coefficient of this regression equation was R²  = 0.336, demonstrating that the model explained 33.60% of interindividual variability in the disposition of voriconazole. In conclusion, predictors of adverse events are CYP2C19 phenotypes, hemoglobin, and voriconazole trough concentration. Determinants of the voriconazole trough concentration were CYP2C19 phenotypes, platelet count, hemoglobin, concomitant use of ilaprazole. If we consider these factors during voriconazole use, we are likely to maximize the treatment effect and minimize adverse events.

Alginate-based drug oral targeting using bio-micro/nano encapsulation technologies

INTRODUCTION

Oral delivery is the most common administrated drug delivery path. However, oral administration of lipophilic drugs has some limitations: they have poor dose-response due to low and varied dissolution kinetics and oral bioavailability with sub-optimal dissolution within the aqueous gastrointestinal microenvironment. Therefore, there is a need for robust formulating methods that protect the drug until it reaches to its optimum absorption site, allowing its optimum pharmacological effects via increasing its intestinal permeation and bioavailability.

AREA COVERED

Herein, we provide insights on orally administered lipophilic drug delivery systems. The detailed description of the obstacles associated with the oral bioavailability of lipophilic drugs are also discussed. Following this, techniques to overcome these obstacles with much emphasis on optimal safety and efficacy are addressed. Newly designed ionic vibrational jet flow encapsulation technology has enormous growth in lipophilic drug delivery systems, which is discussed thereafter.

EXPERT OPINION

Researchers have shown interest in drug's encapsulation. A combination of drug-bile acid and microencapsulation methods can be one promising strategy to improve the oral delivery of lipophilic drugs. However, the most critical aspect of this approach is the selection of bile acids, polymer, and encapsulation technology.

Inhibition of Hepatic CYP2D6 by the Active N-Oxide Metabolite of Sorafenib

The multikinase inhibitor sorafenib (SOR) is used to treat patients with hepatocellular and renal carcinomas. SOR undergoes CYP-mediated biotransformation to a pharmacologically active N-oxide metabolite (SNO) that has been shown to accumulate to varying extents in individuals. Kinase inhibitors like SOR are frequently coadministered with a range of other drugs to improve the efficacy of anticancer drug therapy and to treat comorbidities. Recent evidence has suggested that SNO is more effective than SOR as an inhibitor of CYP3A4-mediated midazolam 1'-hydroxylation. CYP2D6 is also reportedly inhibited by SOR. The present study assessed the possibility that SNO might contribute to CYP2D6 inhibition. The inhibition kinetics of CYP2D6-mediated dextromethorphan O-demethylation were analyzed in human hepatic microsomes, with SNO found to be ~ 19-fold more active than SOR (K_is 1.8 ± 0.3 μM and 34 ± 11 μM, respectively). Molecular docking studies of SOR and SNO were undertaken using multiple crystal structures of CYP2D6. Both molecules mediated interactions with key amino acid residues in putative substrate recognition sites of CYP2D6. However, a larger number of H-bonding interactions was noted between the N-oxide moiety of SNO and active site residues that account for its greater inhibition potency. These findings suggest that SNO has the potential to contribute to pharmacokinetic interactions involving SOR, perhaps in those individuals in whom SNO accumulates.

Novel insights into the complex pharmacokinetics of voriconazole: a review of its metabolism

Voriconazole, a second-generation triazole frequently used for the prophylaxis and treatment of invasive fungal infections, undergoes complex metabolism mainly involving various (polymorphic) cytochrome P450 enzymes in humans. Although high inter- and intraindividual variability in voriconazole pharmacokinetics have been observed and the therapeutic range for this compound is relatively narrow, the metabolism of voriconazole has not been fully elucidated yet. The available literature data investigating the multiple different pathways and metabolites are extremely unbalanced and thus the absolute or relative contribution of the different pathways and enzymes involved in the metabolism of voriconazole remains uncertain. Furthermore, other factors such as nonlinear pharmacokinetics caused by auto-inhibition or -induction and polymorphisms of the metabolizing enzymes hinder safe and effective voriconazole dosing in clinical practice and have not yet been studied sufficiently. This review aimed at amalgamating the available literature on the pharmacokinetics of voriconazole in vitro and in vivo, with a special focus on metabolism in adults and children, in order to congregate an overall landscape of the current body of knowledge and identify knowledge gaps, opening the way towards further research in order to foster the understanding, towards better therapeutic dosing decisions.

Assessment of the in vitro cytochrome P450 (CYP) inhibition potential of ZYTP1, a novel poly (ADP-ribose) polymerase inhibitor

ZYTP1 is a novel Poly (ADP-ribose) polymerase protein inhibitor being developed for cancer indications. The focus of the work was to determine if ZYTP1 had a perpetrator role in the in vitro inhibition of cytochrome P450 (CYP) enzymes to aid dosing decisions during the clinical development of ZYTP1. ZYTP1 IC₅₀ for CYP1A2, 2B6, 2C8, 2C9, 2C19, 2D6 and 3A4/5 was determined using human liver microsomes and LC-MS/MS detection. CYP3A4/5 IC₅₀ of depropylated metabolite of ZYTP1 was also determined. Time dependent inhibition of CYP3A4/5 by ZYTP1 was also assessed using substrates, testosterone and midazolam. The mean IC₅₀ values of ZYTP1 were >100 µM for CYP1A2, 2B6 and 2D6, while 56.1, 24.5, 39.5 and 23.3-58.7 µM for CYP2C8, 2C9, 2C19 and 3A4/5, respectively. The CYP3A4/5 IC₅₀ of depropylated metabolite was 11.95-24.51 µM. Time dependent CYP3A4/5 inhibition was noted for testosterone and midazolam with IC₅₀ shift of 10.9- and 39.9-fold, respectively. With midazolam, the kinact and KI values of ZYTP1 were 0.075 min^-1 and 4.47 µM for the CYP3A4/5 time dependent inhibition, respectively. Because of potent inhibition of CYP3A4/5, drugs that undergo metabolism via CYP3A4/5 pathway should be avoided during ZYTP1 therapy.

Impact of collagen-induced arthritis on the pharmacokinetic disposition of voriconazole, a widely used antifungal agent: in vitro and in vivo investigations in DBA/1J mice

Pharmacokinetics of voriconazole, an anti-fungal agent, was determined in collagen-induced arthritic (CIA) and healthy DBA/1J mice. CIA was confirmed in DBA/1J mice by clinical scoring and histological analysis. In vivo oral pharmacokinetic study (3 mg/kg) and in vitro stability assessment in liver microsomes were performed in CIA vs. healthy DBA/1J mice. Additionally, hepatic portal vein cannulated (HPVC) CIA and healthy mice were used to clarify the role of gut first-pass effect. Voriconazole/N-oxide metabolite was measured in plasma and in vitro samples using liquid chromatography tandem-mass spectrometry method. Voriconazole exposure was reduced in CIA by 27% as compared to healthy mice. Formation of voriconazole N-oxide was higher in CIA mice as evidenced by higher molar C_max ratio (i.e. metabolite/parent) of 2.08 vs. 1.66 in healthy mice. Because voriconazole was stable in microsomes, involvement of presystemic gut metabolism was suspected for decreased voriconazole exposure and formation of higher molar ratio of metabolite. HPVC work revealed higher formation of voriconazole N-oxide in CIA relative to healthy mice resulting in C_max/AUC ratios of 0.41/0.54 and 0.08/0.17, respectively, confirming first-pass effect. The findings may have implications in the clinical therapy of arthritis patients who are concomitantly given voriconazole for the management of fungal infections.

In Vitro Drug-Drug Interaction Potential of Sulfoxide and/or Sulfone Metabolites of Albendazole, Triclabendazole , Aldicarb, Methiocarb, Montelukast and Ziprasidone

BACKGROUND

The use of polypharmacy in the present day clinical therapy has made the identification of clinical drug-drug interaction risk an important aspect of drug development process. Although many drugs can be metabolized to sulfoxide and/or sulfone metabolites, seldom is known on the CYP inhibition potential and/or the metabolic fate for such metabolites.

OBJECTIVE

The key objectives were: a) to evaluate the in vitro CYP inhibition potential of selected parent drugs with sulfoxide/sulfone metabolites; b) to assess the in vitro metabolic fate of the same panel of parent drugs and metabolites.

METHODS

In vitro drug-drug interaction potential of test compounds was investigated in two stages; 1) assessment of CYP450 inhibition potential of test compounds using human liver microsomes (HLM); and 2) assessment of test compounds as substrate of Phase I enzymes; including CYP450, FMO, AO and MAO using HLM, recombinant human CYP enzymes (rhCYP), Human Liver Cytosol (HLC) and Human Liver Mitochondrial (HLMit). All samples were analysed by LC-MS-MS method.

RESULTS

CYP1A2 was inhibited by methiocarb, triclabendazole, triclabendazole sulfoxide, and ziprasidone sulfone with IC50 of 0.71 µM, 1.07 µM, 4.19 µM, and 17.14 µM, respectively. CYP2C8 was inhibited by montelukast, montelukast sulfoxide, montelukast sulfone, tribendazole, triclabendazole sulfoxide, and triclabendazole sulfone with IC50 of 0.08 µM, 0.05 µM, 0.02 µM, 3.31 µM, 8.95 µM, and 1.05 µM, respectively. CYP2C9 was inhibited by triclabendazole, triclabendazole sulfoxide, triclabendazole sulfone, montelukast, montelukast sulfoxide and montelukast sulfone with IC50 of 1.17 µM, 1.95 µM, 0.69 µM, 1.34 µM, 3.61 µM and 2.15 µM, respectively. CYP2C19 was inhibited by triclabendazole and triclabendazole sulfoxide with IC50 of 0.25 and 0.22, respectively. CYP3A4 was inhibited by montelukast sulfoxide and triclabendazole with IC50 of 9.33 and 15.11, respectively. Amongst the studied sulfoxide/sulfone substrates, the propensity of involvement of CY2C9 and CYP3A4 enzyme was high (approximately 56% of total) in the metabolic fate experiments.

CONCLUSION

Based on the findings, a proper risk assessment strategy needs to be factored (i.e., perpetrator and/or victim drug) to overcome any imminent risk of potential clinical drug-drug interaction when sulfoxide/sulfone metabolite(s) generating drugs are coadministered in therapy.