CYP3A4 Inhibitor Research Articles

Static Versus Dynamic Model Predictions of Competitive Inhibitory Metabolic Drug-Drug Interactions via Cytochromes P450: One Step Forward and Two Steps Backwards.

Predicting metabolic drug-drug interactions (DDIs) via cytochrome P450 enzymes (CYP) is essential in drug development, but controversy has reemerged recently about whether in vitro-in vivo extrapolation (IVIVE) using static models can replace dynamic models for some regulatory filings and label recommendations. The aim of this study was to determine if static and dynamic models are equivalent for the quantitative prediction of metabolic DDIs arising from competitive CYP inhibition. Drug parameter spaces were varied to simulate 30,000 DDIs between hypothetical substrates and inhibitors of CYP3A4. Predicted area under the plasma concentration-time profile ratios for substrates (AUCr = AUC(presence of precipitant)/AUC(absence of precipitant)) were compared between dynamic simulations (Simcyp® V21) and corresponding static calculations, giving an inter-model discrepancy ratio (IMDR = AUCrdynamic/AUCrstatic). Dynamic simulations were conducted using a 'population' representative and a 'vulnerable patient' representative with maximal concentration (Cmax) or average steady-state concentration (Cavg,ss) as the inhibitor driver concentrations. IMDRs outside the interval 0.8-1.25 were defined as discrepancy between models. The highest rate of IMDR <0.8 and IMDR >1.25 discrepancies in the 'population' representative was 85.9% and 3.1%, respectively, when using Cavg,ss as the inhibitor driver concentration. Using the 'vulnerable patient' representative showed the highest rate of IMDR >1.25 discrepancies at 37.8%. Static models are not equivalent to dynamic models for predicting metabolic DDIs via competitive CYP inhibition across diverse drug parameter spaces, particularly for vulnerable patients. Caution is warranted in drug development if static IVIVE approaches are used alone to evaluate metabolic DDI risks.

In Vitro and In Silico Biological Activities Investigation of Ethyl Acetate Extract of Rubus ulmifolius Schott Leaves Collected in Algeria

This investigation aimed to assess the in vitro and in silico biological properties of the ethyl acetate (EtOAc) extract obtained from leaves of Rubus ulmifolius Schott collected in Algeria. The phytochemical screening data disclosed that flavonoids, tannins, coumarins, saponins, and anthocyanins were abundant. High levels of total phenolics, total flavonoids and flavonols (523.25 ± 3.53 µg GAE/mg, 20.41 ± 1.80, and 9.62 ± 0.51 µg QE/mg respectively) were detected. Furthermore, GC-MS analysis was performed to identify low molecular weight compounds. d-(-)-Fructofuranose, gallic acid, caffeic acid, and catechin were detected as main metabolites of the EtOAc extract. The outcomes revealed that the extract exerted a potent antioxidant apt, and ensured significant bacterial growth inhibitory capacity, where the inhibition zone diameters ranged from 20.0 ± 0.5 to 24.5 ± 0.3 mm. These outcomes were confirmed through molecular docking against key bacterial enzymes that revealed significant interactions and binding affinities. d-(-)-Fructofuranose was identified as the most polar and flexible compound. Gallic acid and caffeic acid demonstrated higher unsaturation. Caffeic acid was well absorbed in the blood–brain barrier (BBB) and human intestine. Catechin was well absorbed in CaCO3, and can act as an inhibitor of CYP1A2. These results highlight how crucial it is to keep looking into natural substances in the quest for more potent and targeted pathology therapies.

CYP3A4 drug metabolism considerations in pediatric pharmacotherapy

AbstractCytochrome P450 3A4 (CYP3A4) is a crucial enzyme involved in the Phase I metabolism of numerous medications used in clinical practice. Its potential significance in pediatric pharmacotherapy is underscored by the unique metabolic profile of children, which differs markedly from adults, especially in neonates, infants, and young children due to developmental changes in enzyme activity. This review explores the critical role of CYP3A4 in the metabolism of drugs used in the pediatric population, with a particular focus on combination drug therapies. Given the high potential for drug-drug interactions in combination therapies, understanding the modulation of CYP3A4 activity is essential for optimizing therapeutic outcomes and minimizing adverse effects. This paper further examines the structural similarities between these medications and bergamottin, a known CYP3A4 inhibitor found in citric fruits such as grapefruit. Variability in CYP3A4 activity, influenced by genetic polymorphisms, developmental stage, and external factors, necessitates careful consideration in the prescribing and management of drugs in children. This review corroborates the need for personalized medicine approaches and enhanced pharmacovigilance to ensure the safe and effective use of CYP3A4-metabolized drugs in the pediatric population. Graphical Abstract

A novel in vivo approach to monitoring Cyp3a induction and inhibition by bioluminescent urinalysis

ABSTRACT Background Adverse drug–drug interactions (DDI) may occur when one drug accelerates or slows a second drug’s metabolism by, respectively, inducing or inhibiting a cytochrome P450 (CYP) that metabolizes that second drug. We developed an in vivo method employing urinalysis to complement in vitro CYP induction and inhibition measurements widely used to predict DDIs. Research design and methods Focusing on Cyp3a enzymes, the major mammalian drug metabolizers, we applied luciferin-IPA, a selective Cyp3a probe substrate to mice after Cyp3a inducers and inhibitor treatments. Cyp3a converts the probe to a metabolite that is eliminated in urine and drives light output when mixed with a luciferase reaction mixture. We hypothesized that urine from an initial renal elimination phase would, respectively, drive elevated or reduced light output as a reflection of Cyp3a induction or inhibition. Results Luciferase mixed with urine from Cyp3a-induced mice showed enhanced signals, while a Cyp3a inhibitor diminished induced and basal signals versus vehicle. Conclusions A Cyp3a-selective luminogenic probe substrate enables rapid urinalysis-based testing for detecting Cyp3a induction and inhibition and predicting Cyp3a-dependent DDIs. The study serves as a proof of concept for using caged luciferins for in vivo enzyme activity tests with a readily accessible sample type.

Clinical Pharmacology and Side Effects of Venetoclax in Hematologic Malignancies

Venetoclax is a first-in-class B-cell lymphoma/lymphoma-2 (BCL-2) inhibitor that induces apoptosis in malignant cells through the inhibition of BCL-2. The clinical response to venetoclax exhibits heterogeneity, and its sensitivity and resistance may be intricately linked to genetic expression. Pharmacokinetic studies following doses of venetoclax (ranging from 100 to 1200mg) revealed a time to maximum observed plasma concentration of 5-8 hours, with a maximum blood concentration of 1.58-3.89 μg/mL, and a 24-hour area under the concentration-time curve of 12.7-62.8 μg·h/mL. Population-based pharmacokinetic investigations highlighted that factors such as low-fat diet, race, and severe hepatic impairment play pivotal roles in influencing venetoclax dose selection. Being a substrate for CYP3A4, P-glycoprotein, and breast cancer resistance protein, venetoclax undergoes primary metabolism and clearance in the liver, displaying low accumulation in the body.The significance of dose modifications (a 50% decrease with moderate and a 75% reduction with strong CYP3A inhibitors) and a cautious two-hour interval when co-administered with P-glycoprotein inhibitors are highlighted by insights from clinical medication interaction studies. Moreover, an exposure-response relationship analysis indicates that venetoclax exposure significantly correlates not only with overall survival and total response rate but also with the occurrence of ≥ 3-grade neutropenia. In real-world studies, common or severe side effects of venetoclax include tumor lysis syndrome, myelosuppression, nausea, diarrhea, constipation, infection, autoimmune hemolytic anemia, and cardiac toxicity, among others. In this review, we summarize the current clinical pharmacology studies and side effects of venetoclax, which showed that the approved dosage of venetoclax is relatively wide, and the dosage for different hematologic populations can be streamlined in the future.

A Phase I Trial of the Pharmacokinetic Interaction Between Cannabidiol and Tacrolimus.

One in six Americans uses cannabidiol-based or cannabis-derived products. Cannabidiol is a substrate of CYP3A, but its role as a potential CYP3A inhibitor remains unclear. We hypothesized that cannabidiol would inhibit CYP3A-mediated metabolism of tacrolimus. This report is an interim analysis of an open-label, three-period, fixed-sequence, crossover study in healthy participants. Participants first received a single dose of tacrolimus 5 mg orally. After washout, participants later received cannabidiol titrated to 5 mg/kg twice daily for 14 days to reach a steady state, followed by a second single dose of tacrolimus 5 mg orally. Tacrolimus concentrations in whole blood were measured by UHPLC-MS/MS method. Pharmacokinetic parameters were calculated by noncompartmental analysis. Twelve participants completed all periods of the study. The maximum concentration (Cmax) of tacrolimus increased 4.2-fold (P < 0.0001) with cannabidiol (40.2 ± 13.5 ng/mL) compared with without cannabidiol (9.85 ± 4.63 ng/mL). The area under the concentration-vs.-time curve (AUC0-∞) increased 3.1-fold (P < 0.0001). No change in half-life (t1/2) was observed. This study demonstrates that cannabidiol increases tacrolimus exposure. Our data suggest the need for dose reduction in tacrolimus and frequent therapeutic dose monitoring in transplant patients taking cannabidiol concomitantly. Whether this observed interaction occurred due to the inhibition of CYP3A4 and/or CYP3A5 in the liver, intestine, or both, or intestinal drug transporters (e.g., p-glycoprotein) during the first-pass elimination remains to be elucidated.

Clinical and Physiologically Based Pharmacokinetic Model Evaluations of Adagrasib Drug-Drug Interactions.

Adagrasib is a potent, highly selective, orally available, small molecule, covalent inhibitor of G12C mutated KRAS. As both a substrate and strong inhibitor of cytochrome P450 (CYP) 3A4, adagrasib inhibits its own CYP3A4-mediated metabolism following multiple dosing, resulting in time-dependent drug-drug interaction (DDI) liabilities. A physiologically-based pharmacokinetic (PBPK) model was developed and verified using a combination of physicochemical, in vitro and clinical pharmacokinetic (PK) data from healthy volunteers and cancer patients. The PBPK model well-described the single and multiple-dose adagrasib PK data as well as DDI data with itraconazole, rifampin, midazolam, warfarin, dextromethorphan, and digoxin, with model predictions within 1.5-fold of the observed clinical data. The PBPK model was used to predict untested scenarios including the clinical victim and perpetrator DDI liabilities at the approved dosing regimen of 600 mg twice daily (b.i.d.) in cancer patients. Strong, moderate, and weak inhibitors of CYP3A4 are predicted to have a negligible effect on the steady-state exposure of adagrasib 600 mg b.i.d. resulting from the significant inactivation of CYP3A4 by adagrasib. Additionally, strong and moderate inducers of CYP3A4 are predicted to decrease adagrasib exposure by 68% and 22%, respectively. As a perpetrator, adagrasib 600 mg b.i.d. is predicted to be a strong inhibitor of CYP3A4, a moderate inhibitor of CYP2C9 and CYP2D6, and an inhibitor of P-glycoprotein (P-gp). These results successfully supported regulatory interactions with the United States Food and Drug Administration regarding dosing recommendations for when adagrasib is used concomitantly with other medications, supporting a range of label claims in lieu of clinical trials.

MANAGEMENT OF ANTICOAGULATION IN ATRIAL FIBRILLATION: MINIMIZING DRUG INTERACTIONS WITH DOACS

Introduction: Atrial fibrillation (AF) is a common cardiac arrhythmia that elevates the risk of thromboembolic events, necessitating effective anticoagulation strategies. Direct oral anticoagulants (DOACs) have become the preferred choice due to their safety profiles; however, drug interactions can compromise their efficacy and safety. Objective: This study aims to assess the impact of drug interactions on the efficacy and safety of DOACs in patients with AF. Method: A literature review was conducted using databases such as the Virtual Health Library, LILACS Plus, and Medline, focusing on articles published from 2019 to 2024. Inclusion criteria emphasized studies related to drug interactions involving DOACs and AF, resulting in the selection of 13 relevant articles. Results: The analysis revealed a significant prevalence of drug interactions among patients treated with DOACs. Co-prescription with CYP3A4 inhibitors and P-glycoprotein modulators was linked to increased bleeding risks. Factors such as age, renal function, and the presence of comorbidities were crucial in determining appropriate dosing and the risk of adverse events. Conclusion: Careful management of AF patients on DOACs is vital to mitigate risks associated with drug interactions. Personalized treatment approaches that consider individual clinical profiles and ongoing education for healthcare providers are essential to optimize anticoagulation therapy.

In Vitro Evaluation of CYP-Mediated Metabolism of Fezolinetant and Pharmacokinetic Interaction Between Fezolinetant and Fluvoxamine in Healthy Postmenopausal Smokers and Nonsmokers.

Fezolinetant is an oral, nonhormonal, neurokinin 3 receptor antagonist treatment option for moderate to severe vasomotor symptoms associated with menopause. An in vitro study using human recombinant cytochrome P450 (CYP) enzymes and human liver microsomes showed that fezolinetant is metabolized to its major but inactive metabolite, ES259564, predominantly through CYP1A2, with minor contributions from CYP2C9 and CYP2C19. The clinical impact of CYP1A2 inhibition and induction on single-dose pharmacokinetics of fezolinetant was assessed in an open-label, single-sequence, phase 1 study in healthy postmenopausal women, where the impact of fluvoxamine, a strong CYP1A2 inhibitor, and smoking, a moderate CYP1A2 inducer, were evaluated. In total, 18 participants, 9 of whom were smokers, were enrolled. Fezolinetant pharmacokinetics were evaluated after a single 30-mg dose on Day 1 and Day 7. Fluvoxamine 50 mg was administered as a single dose on Days 3 and 10 and twice daily from Days 4 to 9. Fluvoxamine increased geometric mean ratio of fezolinetant maximum plasma concentrations (Cmax) and area under the curve from time of dosing extrapolated to infinity (AUCinf) to 182% and 939%, respectively, while ES259564 Cmax decreased to 20.1% with no significant change in AUC. In smokers versus nonsmokers, when fezolinetant was administered alone, fezolinetant Cmax and AUCinf decreased to 71.7% and 48.3%, respectively, while ES259564 Cmax increased to 130.2% and AUCinf decreased to 81.8%. A single oral 30-mg dose of fezolinetant was considered safe and well tolerated when co-administered with fluvoxamine in healthy postmenopausal women.

Metabolic Activation and Cytotoxicity of Donepezil Induced by CYP3A4.

Donepezil (DNP) is a selective cholinesterase inhibitor widely used for the therapy of Alzheimer's disease. Instances of liver injury correlated with DNP treatment have been reported, yet the underlying hepatotoxic mechanism remains to be elucidated. This study aimed to explore the contribution of metabolic activation to the hepatotoxicity of DNP. The structure of 6-O-desmethyl DNP (M1), the oxidative metabolite of DNP, was characterized by chemical synthesis, LC-MS/MS, and nuclear magnetic resonance. A reactive quinone methide resulting from the metabolism of DNP was captured by glutathione (GSH) fortified in liver microsomal incubations after exposure to DNP, and the resulting GSH conjugate (M2) was detected in the bile of rats receiving DNP. Recombinant human P450 enzyme incubation studies demonstrated that CYP3A4 was the principal enzyme responsible for the production of M1 and M2. The generation of M2 declined in rat primary hepatocytes pretreated with ketoconazole, an inhibitor of CYP3A4, which also decreased the vulnerability of rat primary hepatocytes to DNP-caused cytotoxicity. These findings suggest that the quinone methide metabolite may contribute to the cytotoxicity and hepatotoxicity caused by the DNP.

Drug-induced cholestasis (DIC) predictions based on in vitro inhibition of major bile acid clearance mechanisms.

Drug-induced cholestasis (DIC) is recognized as a major safety concern in drug development, as it represents one of the three types of drug-induced liver injury (DILI). Cholestasis is characterized by the disruption of bile flow, leading to intrahepatic accumulation of toxic bile acids. Bile acid regulation is a multifarious process, orchestrated by several hepatic mechanisms, namely sinusoidal uptake and efflux, canalicular secretion and intracellular metabolism. In the present study, we developed a prediction model of DIC using in vitro inhibition data for 47 marketed drugs on nine transporters and five enzymes known to regulate bile acid homeostasis. The resulting model was able to distinguish between drugs with or without DILI concern (p-value = 0.039) and demonstrated a satisfactory predictive performance, with the area under the precision-recall curve (PR AUC) measured at 0.91. Furthermore, we simplified the model considering only two processes, namely reversible inhibition of OATP1B1 and time-dependent inhibition of CYP3A4, which provided an enhanced performance (PR AUC = 0.95). Our study supports literature findings suggesting a contribution not only from a single process inhibition, but a rather synergistic effect of the key bile acid clearance processes in the development of cholestasis. The use of a quantitative model in the preclinical investigations of DIC is expected to reduce attrition rate in advanced development programs and guide the discovery and development of safe medicines.

The Effect of Ketoconazole and Quinestrol Combination on Reproductive Physiology in Male Mice.

This study investigates whether ketoconazole, a CYP3A4 inhibitor, can enhance the suppressive effects of quinestrol on reproductive capacity, potentially allowing for a reduced quinestrol dosage while maintaining its efficacy. A total of 104 healthy adult male mice were divided into two groups, assessed at 10 and 30 days. Within each group, six treatment categories were tested: the control (CK), quinestrol alone (Q1, Q5), and quinestrol combined with varying doses of ketoconazole (Q1 + K0.4, Q1 + K2, Q5 + K0.4). The key parameters measured included internal and reproductive organ weights, sperm density, sperm motility, sperm abnormalities, and CYP3A4 enzyme content in intestinal and liver tissues. After 10 days, the combination of a low dose of quinestrol with ketoconazole (Q1 + K0.4) showed the most significant pronounced effects in reducing reproductive potential, with notable reductions in epididymal weight, sperm density, sperm abnormality rate and vitality, serum hormone levels, and CYP3A4 content in the small intestine and liver. Although some reproductive parameters returned to near-baseline levels after 30 days, the Q1 + K0.4 regimen continued to exhibit reduced seminal vesicle weight and testosterone levels. Importantly, the combination did not significantly increase CYP3A4 enzyme content, indicating effective metabolic inhibition. The combination of quinestrol and ketoconazole, especially the Q1 + K0.4 regimen, demonstrated the most noticeable impact on reducing reproductive capacity. This regimen significantly reduced key reproductive parameters and showed strong metabolic inhibition, suggesting that ketoconazole substantially enhances the efficacy of quinestrol in fertility control.

The Effect of Metformin and Hydrochlorothiazide on Cytochrome P450 3A4 Metabolism of Ivermectin: Insights from In Silico Experimentation.

The spread of SARS-CoV-2 has led to an interest in using ivermectin (a potent antiparasitic agent) as an antiviral agent despite the lack of convincing in vivo clinical data for its use against COVID-19. The off-target prophylactic use of ivermectin adds a substantial risk of drug-drug interactions with pharmaceutical medications used to treat chronic conditions like diabetes and hypertension (metformin and hydrochlorothiazide, respectively). Therefore, this study aims to evaluate the potential drug-drug interactions between ivermectin with either metformin or hydrochlorothiazide. In silico experiments and high-throughput screening assays for CYP3A4 were conducted to understand how metformin and hydrochlorothiazide might affect CYP3A4's role in metabolizing ivermectin. The study findings indicated that hydrochlorothiazide is more stable than both ivermectin and metformin. This conclusion was further supported by root mean square fluctuation analysis, which showed that hydrochlorothiazide is more flexible. The variation in the principal component analysis scatter plot across the first three normal modes suggests hydrochlorothiazide has a more mobile conformation than ivermectin and metformin. Additionally, a strong inhibition of CYP3A4 by hydrochlorothiazide was observed, suggesting that hydrochlorothiazide's regulatory effects could significantly impede CYP3A4 activity, potentially leading to a reduced metabolism and clearance of ivermectin in the body. Concurrent administration of these drugs may result in drug-drug interactions and hinder the hepatic metabolism of ivermectin.

Clozapine Toxicity Predictor: Deep neural network model predicting clozapine toxicity and its therapeutic dose range

Clozapine is the gold standard for treatment-resistant schizophrenia; however, its superior efficacy is accompanied by potentially serious adverse events (neutropenia, seizures, constipations, pneumonia), many of which are also concentration-dependent. As such, clozapine dose titration should be guided by therapeutic drug monitoring (TDM). However, access to TDM is often limited. The present study describes a new deep neural network that can predict the concentrations, toxicity and therapeutic dose range for clozapine and norclozapine. The model was trained on basic clinical data (biological sex, age, clozapine daily dose, BMI, CRP and number of CYP 1A2 and 3A4 substrates, inhibitors and inducers) from 69 patients with treatment-refractory patients treated with different clozapine doses. Our findings provide the training efficacy data for the model, as well as an analysis of clozapine and norclozapine blood concentrations in a test group of three additional patients, to demonstrate its practical capabilities. The model is licensed on a free and permissive 2-Clause BSD license and is available to all clinicians; it can be accessed as a web application, available at https://csk.umed.pl/clotop.

Evaluation of drug-drug interactions of a novel potent FLT3 inhibitor SKLB1028 in healthy subjects.

SKLB1028 is a novel multi-target protein kinase inhibitor under investigation for the treatment of FLT3-ITD mutated acute myeloid leukemia. Based on the preclinical characterization of SKLB1028 metabolism, three drug-drug interaction clinical studies were performed to investigate the effects of itraconazole, rifampin (CYP3A4 inhibitor and inducer, respectively), and gemfibrozil (CYP2C8 inhibitor) on the metabolism of SKLB1028. Fourteen healthy Chinese male subjects were enrolled in each study. In Study 1, subjects were administered a single dose of SKLB1028 (100 mg on days 1 and 11) and multiple doses of itraconazole (200 mg twice daily on day 8 and 200 mg once daily from days 9 to 18). Itraconazole was given with a loading dose on Day 8 and the total administration of itraconazole was 11 days. In Study 2, subjects were administered a single dose of SKLB1028 (100 mg on days 1 and 12) and multiple doses of gemfibrozil (600 mg twice daily from days 8 to 19). In Study 3, subjects were administered a single dose of SKLB1028 (150 mg on days 1 and 15) and multiple doses of rifampin (600 mg once daily from day 8 to 22). Itraconazole increased the AUC and Cmax of SKLB1028 by approximately 28% and 41%, respectively. Compared to the single drug, co-administration with gemfibrozil increased the AUC of SKLB1028 by ~26% and the Cmax by ~21%. Co-administration with rifampin reduced the AUC of SKLB1028 by ~30%, while the Cmax did not change significantly. All treatments were well tolerated in all three studies.

Drug-Drug Interaction Management with the Novel Anti-Cytomegalovirus Agents Letermovir and Maribavir: Guidance for Clinicians.

Letermovir and maribavir have demonstrated efficacy in the prevention and treatment, respectively, of immunosuppressed patients with cytomegalovirus (CMV) infection and disease. These patients often have polypharmacy making them at risk for drug-drug interactions. Both letermovir and maribavir can be perpetrators and victims of drug-drug interactions. Letermovir is a moderate inhibitor of CYP3A, CYP2C8 and OATP1B1/3, and a moderate inducer of CYP2C19. It is a substrate of UGT1A1/3, BCRP, P-gp and OATP1B1/3. Maribavir is a moderate CYP2C9 inhibitor and a substrate of CYP3A. Drug-drug interactions between these anti-CMV agents and a number of therapeutic classes, such as immunosuppressants, antifungal agents, and hemato-oncological agents, can have clinical consequences and deserve dose modification or close monitoring. In a number of examples, three-way drug interactions need to be assessed. The objective of this review is to provide clinicians with guidance for drug-drug interaction management, based on existing data from drug-drug interaction studies, and extrapolation to other relevant co-medications that have not (yet) been studied but that are frequently used in these patient populations.

Pharmacokinetic Model of Drug Interaction of Tacrolimus with Combined Administration of CYP3A4 Inhibitors Voriconazole and Clarithromycin After Bone Marrow Transplantation.

A pharmacokinetic model has been developed to quantify the drug-drug interactions of tacrolimus with concentration-dependent inhibition of cytochrome P450 (CYP) 3A4 from voriconazole and clarithromycin based on the CYP3A5 and CYP2C19 genotypes. This retrospective study recruited unrelated bone marrow transplant recipients receiving oral tacrolimus concomitantly with voriconazole and clarithromycin. The published population pharmacokinetic model that implemented genotypes of CYP3A5 (tacrolimus) and CYP2C19 (voriconazole) was integrated. The tested CYP3A4 inhibition models (Sigmoid efficacy maximum [Emax], Emax, log-linear, and linear) were a function of competitive inhibition of voriconazole and mechanism-based inhibition of clarithromycin in a virtual enzyme compartment. The total tacrolimus trough concentrations were 119 points, with a median of 4.3 (range: 2.0-9.9) ng/mL (n = 3). The final model comprised the Sigmoid Emax model for voriconazole and clarithromycin, which depicted time-course alterations in tacrolimus concentration and clearance when given voriconazole and clarithromycin. These findings could facilitate the model-informed precision dosing of tacrolimus after unrelated bone marrow transplant.

Heterotropic Allosteric Modulation of CYP3A4 In Vitro by Progesterone: Evidence for Improvement in Prediction of Time Dependent Inhibition for Macrolides.

Predictions of drug-drug interactions resulting from time-dependent inhibition (TDI) of CYP3A4 have consistently overestimated or mis-predicted (i.e. false positives) the interaction that is observed in vivo. Recent findings demonstrated that the presence of the allosteric modulator progesterone (PGS) in the in vitro assay could alter the in vitro kinetics of CYP3A4 TDI with inhibitors that interact with the heme moiety, such as metabolic-intermediate complex (MIC) forming inhibitors. The impact of the presence of 100 µM PGS on the TDI of molecules in the class of macrolides typically associated with MIC formation was investigated. Presence of PGS resulted in varied responses across the inhibitors tested. The TDI signal was eliminated for five inhibitors, and unaltered in the case of one, fidaxomicin. The remaining molecules erythromycin, clarithromycin, and troleandomycin, were observed to have a decrease in both potency and maximum inactivation rate ranging from 1.7-fold to 6.7-fold. These changes in TDI kinetics led to a >90% decrease in inactivation efficiency. In order to determine in vitro conditions that could reproduce in vivo inhibition, varied concentrations of PGS were incubated with clarithromycin and erythromycin. Resulting in vitro TDI kinetics were incorporated into dynamic physiologically-based pharmacokinetic (PBPK) models to predict clinically observed interactions. The results suggested that a concentration of ~45 µM PGS would result in TDI kinetic values that could reproduce in vivo observations and could potentially improve predictions for CYP3A4 TDI. Significance Statement The impact of the allosteric heterotropic modulator progesterone on the CYP3A4 time-dependent inhibition kinetics was quantified for a set of metabolic-intermediate complex forming mechanism-based inhibitors. We identify the in vitro conditions that optimally predict time-dependent inhibition for in vivo drug-drug interactions through dynamic physiologically-based pharmacokinetic modeling. The optimized assay conditions improve in vitro to in vivo translation and prediction of time-dependent inhibition.

Effect of CYP3A5*3 genotype on exposure and efficacy of quetiapine: A retrospective, cohort study

BackgroundThe involvement of cytochrome P450 3A5 (CYP3A5) in the metabolism of quetiapine has been proposed, though conclusive evidence is lacking. This study aimed to quantitatively assess the impact of CYP3A5 genetic variability on quetiapine exposure in a Chinese patient population. MethodsPatient data were retrospectively collected from the database of the Mental Health Centre at the First Hospital of Hebei Medical University, covering the period from September 1, 2019, to July 1, 2023. The study included patients genotyped for CYP3A5 who were treated with quetiapine. Inclusion criteria for the analysis of pharmacokinetic parameters, such as serum concentrations of the drug and its metabolites, included oral administration of quetiapine, availability of information on the prescribed daily dose and concomitant medications, and the determination of steady-state blood levels at the time of sampling (after at least 3 days of continuous administration at the same dose). Exclusion criteria comprised polypharmacy with known CYP3A4 inducers or inhibitors, as well as patients with hepatic or renal insufficiency. The primary endpoint was the exposure to quetiapine and N-dealkylquetiapine, measured using dose-corrected concentrations (C/D). The secondary endpoint was the metabolism of quetiapine to N-dealkylquetiapine, assessed by the ratio of metabolite to parent drug concentrations. The third endpoint is the differences in adverse reactions, QTc intervals, and biochemical parameters among patients with different CYP3A5 genotypes. ResultBased on the inclusion and exclusion criteria, clinical data from 207 patients were ultimately included in the study. Of these, 20 patients had the CYP3A5*1/*1 genotype, 78 had the CYP3A5*1/*3 genotype, and 109 had the CYP3A5*3/*3 genotype. The CYP3A5*3 variant was found to significantly impact the metabolism of quetiapine. The C/D values for both quetiapine and N-dealkyl quetiapine were notably higher in individuals with the *3/*3 genotype compared to those with the *1/*1 and *1/*3 genotypes (P1 < 0.001 and P2 = 0.002, respectively). A comparison of the variability in metabolic ratios among different genotype groups revealed no significant difference (P = 0.067). However, a post hoc analysis indicated that the metabolic ratio in poor metabolizers was significantly lower than that in intermediate metabolizers (P = 0.021). The analysis of adverse reaction incidence and QTc intervals among different genotypes showed no statistically significant differences (P = 0.652, P = 0.486). However, comparison of biochemical parameters across different genotype groups revealed that alanine aminotransferase, uric acid, hemoglobin, and gamma-glutamyl transferase levels were significantly higher in patients with the CYP3A5*3/*3 genotype compared to those with the CYP3A5*1/*1 and CYP3A5*1/*3 genotypes. ConclusionThe results indicated that the genetic polymorphism of CYP3A5*3 significantly influences the metabolism of quetiapine. Specifically, carriers of the CYP3A5*3/*3 genotype exhibited higher blood levels of quetiapine, with a greater likelihood of these levels exceeding the therapeutic range. This finding underscores the need for clinicians to pay special attention to the efficacy and occurrence of adverse reactions when prescribing quetiapine to patients carrying the CYP3A5*3/*3 genotype.

Inhibitory effects characteristics of polysaccharide of Polygonati Rhizome on cytochrome P450 enzymes.

As the major active ingredient of Polygonatum sibriricum Red., polysaccharide of Polygonati Rhizome (PSP) has been reported to possess various pharmacological activities, especially for the treatment of chronic disorders in the elderly. This study evaluated the effect of PSP on the activities of major cytochrome P450 enzymes (CYP450) isoforms, aiming to provide theoretical reference for its co-prescription with other drugs and prevent the risk of adverse drug-drug interaction. The activities of CYP450 isoforms were assessed in human liver microsomes with specific probe substances. Through Lineweaver-Burk fitting models, the effect of PSP on the activity of inhibited CYP450 isoforms was characterized by competitive and non-competitive models. Dose-dependent and time-dependent experiments were also performed to completely understand the inhibition. Among experimental isoforms, PSP significantly inhibited the activities of CYP2C9, 2D6, and 3A4 in a concentration-dependent manner with IC50 values of 14.01, 17.63, and 5.33 μM. The inhibition of CYP2C9 and 2D6 was best fitted with the competitive model with the Ki values of 7.15 and 8.92 μM, respectively, while the inhibition of CYP3A4 was non-competitive with the Ki value of 2.63 μM. Additionally, the inhibition of CYP3A4 by PSP also showed time-dependent characteristics with the inhibition parameters, KI of 1.273 μM-1 and Kinact of 0.036 min-1. PSP exerted moderate inhibition on CYP2C9 and 2D6 and strong inhibition of CYP3A4. The dosage of CYP2C9-, 2D6-, and 3A4-metabolized drugs should be adjusted when co-administrated with PSP and its sourced herbs.