P450 3A4 Research Articles

Effect of Clarithromycin, a Strong CYP3A and P-glycoprotein Inhibitor, on the Pharmacokinetics of Edoxaban in Healthy Volunteers and the Evaluation of the Drug Interaction with Other Oral Factor Xa Inhibitors by a Microdose Cocktail Approach

PurposeWe assessed the differential effect of clarithromycin, a strong inhibitor of cytochrome P450 (CYP) 3A4 and P-glycoprotein, on the pharmacokinetics of a regular dose of edoxaban and on a microdose cocktail of factor Xa inhibitors (FXaI). Concurrently, CYP3A activity was determined with a midazolam microdose.MethodsIn an open-label fixed-sequence trial in 12 healthy volunteers, the pharmacokinetics of a microdosed FXaI cocktail (μ-FXaI; 25 μg apixaban, 50 μg edoxaban, and 25 μg rivaroxaban) and of 60 mg edoxaban before and during clarithromycin (2 x 500 mg/d) dosed to steady-state was evaluated. Plasma concentrations of study drugs were quantified using validated ultra-performance liquid chromatography–tandem mass spectrometry methods.ResultsTherapeutic clarithromycin doses increased the exposure of a therapeutic 60 mg dose of edoxaban with a geometric mean ratio (GMR) of the area under the plasma concentration-time curve (AUC) of 1.53 (90 % CI: 1.37–1.70; p < 0.0001). Clarithromycin also increased the GMR (90% CI) of the exposure of microdosed FXaI apixaban to 1.38 (1.26–1.51), edoxaban to 2.03 (1.84–2.24), and rivaroxaban to 1.44 (1.27–1.63). AUC changes observed for the therapeutic edoxaban dose were significantly smaller than those observed with the microdose (p < 0.001).ConclusionClarithromycin increases FXaI exposure. However, the magnitude of this drug interaction is not expected to be clinically relevant. The edoxaban microdose overestimates the extent of the drug interaction with the therapeutic dose, whereas AUC ratios for apixaban and rivaroxaban were comparable to the interaction with therapeutic doses as reported in the literature.Trial RegistrationEudraCT Number: 2018-002490-22

Development of a Simultaneous Liquid Chromatography-Tandem Mass Spectrometry Analytical Method for Urinary Endogenous Substrates and Metabolites for Predicting Cytochrome P450 3A4 Activity.

CYP3A4, which contributes to the metabolism of more than 30% of clinically used drugs, exhibits high variation in its activity; therefore, predicting CYP3A4 activity before drug treatment is vital for determining the optimal dosage for each patient. We aimed to develop and validate an LC-tandem mass spectrometry (LC-MS/MS) method that simultaneously measures the levels of CYP3A4 activity-related predictive biomarkers (6β-hydroxycortisol (6β-OHC), cortisol (C), 1β-hydroxydeoxycholic acid (1β-OHDCA), and deoxycholic acid (DCA)). Chromatographic separation was achieved using a YMC-Triart C18 column and a gradient flow of the mobile phase comprising deionized water/25% ammonia solution (100 : 0.1, v/v) and methanol/acetonitrile/25% ammonia solution (50 : 50 : 0.1, v/v/v). Selective reaction monitoring in the negative-ion mode was used for MS/MS, and run times of 33 min were used. All analytes showed high linearity in the range of 3-3000 ng/mL. Additionally, their concentrations in urine samples derived from volunteers were analyzed via treatment with deconjugation enzymes, ignoring inter-individual differences in the variation of other enzymatic activities. Our method satisfied the analytical validation criteria under clinical conditions. Moreover, the concentrations of each analyte were quantified within the range of calibration curves for all urine samples. The conjugated forms of each analyte were hydrolyzed to accurately examine CYP3A4 activity. Non-invasive urine sampling employed herein is an effective alternative to invasive plasma sampling. The analytically validated simultaneous quantification method developed in this study can be used to predict CYP3A4 activity in precision medicine and investigate the potential clinical applications of CYP3A4 biomarkers (6β-OHC/C and 1β-OHDCA/DCA ratios).

Robust protein-based engineering of hepatocyte-like cells from human mesenchymal stem cells.

Cells of interest can be prepared from somatic cells by forced expression of lineage-specific transcription factors, but it is required to establish a vector-free system for their clinical use. Here, we report a protein-based artificial transcription system for engineering hepatocyte-like cells from human umbilical cord-derived mesenchymal stem cells (MSCs). MSCs were treated for 5 days with 4 artificial transcription factors (4F), which targeted hepatocyte nuclear factor (HNF)1α, HNF3γ, HNF4α, and GATA-binding protein 4 (GATA4). Then, engineered MSCs (4F-Heps) were subjected to epigenetic analysis, biochemical analysis and flow cytometry analysis with antibodies to marker proteins of mature hepatocytes and hepatic progenitors such as delta-like homolog 1 (DLK1) and trophoblast cell surface antigen 2 (TROP2). Functional properties of the cells were also examined by injecting them to mice with lethal hepatic failure. Epigenetic analysis revealed that a 5-day treatment of 4F upregulated the expression of genes involved in hepatic differentiation, and repressed genes related to pluripotency of MSCs. Flow cytometry analysis detected that 4F-Heps were composed of small numbers of mature hepatocytes (at most 1%), bile duct cells (~19%) and hepatic progenitors (~50%). Interestingly, ~20% of 4F-Heps were positive for cytochrome P450 3A4, 80% of which were DLK1-positive. Injection of 4F-Heps significantly increased survival of mice with lethal hepatic failure, and transplanted 4F-Heps expanded to more than 50-fold of human albumin-positive cells in the mouse livers, well consistent with the observation that 4F-Heps contained DLK1-positive and/or TROP2-positive cells. Taken together with observations that 4F-Heps were not tumorigenic in immunocompromised mice for at least 2 years, we propose that this artificial transcription system is a versatile tool for cell therapy for hepatic failures.

Chia Seeds Oil Suppresses the Resistance of Hepatocellular Carcinoma Cells to Liposomal-doxorubicin and Upregulates the Tumor Suppressor miRNAs.

Chia seed is an oil seed with multiple biological activities. Doxorubicin is effective chemotherapy for liver cancer. Resistance and adverse effects are doxorubicin limitations. This study aimed to investigate the effect of chia seeds oil (CSO) on the resistance of HepG2 cells to liposomal-doxorubicin (DOX). The objective were investigated through measuring cytotoxicity, doxorubicin-metabolizing enzyme Cytochrome P450 3A4 (CYP-3A4), multidrug resistance-associated protein (MRP1), and the expression of multiple tumor suppressor microRNAs. The findings indicated that low concentration of CSO increased HepG2 cells' sensitivity to DOX, as concluded from its higher cytotoxicity. DOX-induced mRNAs of CYP-3A4 and MRP1 and their protein levels. CSO inhibited both in DOX-treated cells. CSO-induced tumor suppressor miRNAs. Doxorubicin inhibited miR-122 and let-7/b/e expression, while it led to overexpression of let- 7a. CSO/DOX upregulated let-7/b/e, miR-34a, and miR-122 (which inhibits MRP1) and downregulated let-7a, which may lead to increased apoptosis. CSO effectively re-sensitized HepG2 cells to liposomal-doxorubicin via inhibiting MRP1 and CYP-3A4, which may increase in vivo doxorubicin bioavailability and decrease its therapeutic dose to diminish its adverse effects.

Bosentan effect on Teneligliptin’s Antidiabetic effect in Animal Model

Due to a variety of comorbidities, Patients with type 2 diabetes usually require a multifaceted approach to therapy. A large number of medications taken at the same time increase the risk of undesirable drug effects or drug interactions in the patient. It's vital to think about cytochrome P-450 (CYP) enzyme interactions while using a multifactorial pharmacotherapy approach. The cytochrome P450 enzymes CYP2C9 and CYP3A4 metabolize bosentan in the liver similarly, teneligliptin is metabolized by flavin-containing monooxygenase 3 (FMO3) and cytochrome P450 (CYP) 3A4. This study was conducted to investigate a possible pharmacokinetic interaction between bosentan and teneligliptin. Interaction of teneligliptin, the known dipeptidyl peptidase-4 inhibitors or gliptins anti diabetic drugs with bosentan, a pulmonary antihypertensive agent, in healthy and alloxan-induced diabetic rats, was tested. Blood samples were taken from rats at various intervals up to 24 hours and blood glucose levels were calculated. The parameters considered for the analysis of the effect on teneligliptin induced hypoglycemia were the onset of hypoglycemia (duration required to reduce blood glucose level by 15% - 20%), duration of hypoglycemia (duration of time in which more than 15 % -20 % decrease in blood glucose level is managed to maintained), and peak hypoglycemia. In both healthy albino rats and diabetic rats, a single dose of bosentan did not affect blood glucose levels. These results suggest that bosentan has no hypoglycemic effect, implying that the drug-drug interaction with teneligliptin is of the pharmacokinetic kind.

Bone marrow niche chemoprotection of metastatic solid tumors mediated by CYP3A4.

The bone/bone marrow is one of the most common sites for metastatic solid tumors. Moreover, the tumor microenvironment is an essential part of cancer homeostasis. Previously, it was shown that cytochrome P450 enzymes (CYPs) are present in the bone marrow (BM) microenvironment, particularly in the mesenchymal stroma cells, at levels comparable to those of hepatocytes. It was found that the CYPs play important roles in nurturing and maintaining normal hematopoietic stem cells as well as multiple myeloma and leukemia cells, including protecting them from toxic insults. It was hypothesized that the CYPs in the BM microenvironment might play a similar role in solid tumors metastatic to bone. The interaction between the BM microenvironment and malignant cells that routinely metastasize to the bone (lung, breast, and prostate cancer) was modeled. Via genetic engineering and pharmacological approaches, the role of stromal cytochrome P450 3A4 (CYP3A4) in drug resistance promoted by the BM microenvironment in niche-cancer models in vitro and in vivo was interrogated. BM stroma protected prostate, breast, and lung cancer cells from cytotoxic chemotherapy. Stromal CYP3A4 was at least partially responsible for this protection in vitro and in vivo. Moreover, inhibiting CYP3A4 with clarithromycin overcame the stroma-mediated chemoresistance toward prostate, breast, and lung cancer cells. These results suggest that, similar to observations from hematologic malignancies, the BM microenvironment, through expression of CYPs, creates a sanctuary site from chemotherapy for metastatic solid tumors. Targeting these sanctuaries holds promise for eradicating bone metastasis in solid tumors.

Lower sertraline plasma concentration in patients co-medicated with clozapine-Implications for pharmacological augmentation strategies in schizophrenia.

Augmentation of antipsychotic treatment with antidepressants represents a common and beneficial treatment strategy in patients suffering from schizophrenia. Combining clozapine and the selective serotonin reuptake inhibitor (SSRI) sertraline represents a clinically important strategy in patients with therapy-resistant schizophrenia, but there is limited knowledge about mutual pharmacokinetic interactions. In the present study, we assessed the impact of clozapine on sertraline plasma concentrations. Based on a therapeutic drug monitoring (TDM) database, sertraline plasma concentrations were compared between two groups: patients receiving a combined treatment with sertraline and clozapine (N= 15) and a matched control group receiving sertraline but no clozapine (N= 17). Group differences with respect to raw and dose-adjusted concentrations were assessed using nonparametric tests. Comedication with clozapine was associated with 67% lower median sertraline plasma concentrations (16 vs. 48 ng/mL; p= .022) and 28% lower median dose-adjusted plasma concentrations (C/D; 0.21 vs. 0.29 (ng/mL)/(mg/day); p= .049) as compared to the control group. Scatter plots revealed a complex relationship between the dosage of clozapine and dose-adjusted sertraline concentrations composed of an initial decrease at clozapine doses below 300 mg, an increase between 300 and 600 mg and a final decrease at 800 mg which was best modeled by a third order polynomial term. Cotreatment with clozapine may lead to reduced sertraline plasma concentrations which may be explained by clozapine-induced gastrointestinal hypo-mobility already present at low doses and cytochrome P450 3A4 inducing properties at high clozapine doses. For this drug combination, clinicians should consider TDM to confirm therapeutically effective plasma concentrations of sertraline.

Investigating a new C2-symmetric testosterone dimer and its dihydrotestosterone analog: Synthesis, antiproliferative activity on prostate cancer cell lines and interaction with CYP3A4

The synthesis of a 17α-linked C2-symmetric testosterone dimer and its dihydrotestosterone analog is reported. The dimers were synthesized using a short five-step reaction sequence with 28% and 38% overall yield for the testosterone and dihydrotestosterone dimer, respectively. The dimerization reaction was achieved by an olefin metathesis reaction with 2nd generation Hoveyda-Grubbs catalyst. The dimers and their corresponding 17α-allyl precursors were tested for the antiproliferative activity on androgen–dependent (LNCaP) and androgen–independent (PC3) prostate cancer cell lines. The effects on cells were compared with that of the antiandrogen cyproterone acetate (CPA). The results showed that the dimers were active on both cell lines, with an increased activity towards androgen–dependent LNCaP cells. However, the testosterone dimer (11) was fivefold more active than the dihydrotestosterone dimer (15), with an IC50 of 11.7 μM vs. 60.9 μM against LNCaP cells, respectively, and more than threefold more active than the reference drug CPA (IC50 of 40.7 μM). Likewise, studies on the interaction of new compounds with drug-metabolizing cytochrome P450 3A4 (CYP3A4) showed that 11 was a fourfold stronger inhibitor than 15 (IC50 of 3 μM and 12 μM, respectively). This suggests that changes in the chemical structure of sterol moieties and the manner of their linkage could largely affect both the antiproliferative activity of androgen dimers and their crossreactivity with CYP3A4.

Identification of PXR Activators from Uncaria Rhynchophylla (Gou Teng) and Uncaria Tomentosa (Cat's Claw).

Uncaria rhynchophylla (Gou Teng) and Uncaria tomentosa (cat's claw) are frequently used herbal supplements in Asia and America, respectively. Despite their common usage, information is limited regarding potential herb-drug interactions associated with Gou Teng and cat's claw. The pregnane X receptor (PXR) is a ligand-dependent transcription factor that regulates cytochrome P450 3A4 (CYP3A4) expression and contributes to some known herb-drug interactions. A recent study found that Gou Teng induces CYP3A4 expression, but its mechanism is unknown. Cat's claw has been determined as a PXR-activating herb, but the PXR activators in cat's claw have not been identified. Using a genetically engineered PXR cell line, we found that the extracts of Gou Teng and cat's claw can dose-dependently activate PXR and induce CYP3A4 expression. We next used a metabolomic approach to profile the chemical components in the extracts of Gou Teng and cat's claw followed by screening for PXR activators. Four compounds, isocorynoxeine, rhynchophylline, isorhynchophylline, and corynoxeine, were identified as PXR activators from both Gou Teng and cat's claw extracts. In addition, three more PXR activators were identified from the extracts of cat's claw, including isopteropodine, pteropodine, and mitraphylline. All seven of these compounds showed the half-maximal effective concentration <10 µM for PXR activation. In summary, our work determined Gou Teng as a PXR-activating herb and discovered novel PXR activators from Gou Teng as well as cat's claw. SIGNIFICANCE STATEMENT: This study's data can be used to guide the safe use of Gou Teng and cat's claw by avoiding PXR-mediated herb-drug interactions.

Dynamic Ir(III) Photosensors for the Major Human Drug-Metabolizing Enzyme Cytochrome P450 3A4.

Probing the activity of cytochrome P450 3A4 (CYP3A4) is critical for monitoring the metabolism of pharmaceuticals and identifying drug-drug interactions. A library of Ir(III) probes that detect occupancy of the CYP3A4 active site were synthesized and characterized. These probes show selectivity for CYP3A4 inhibition, low cellular toxicity, Kd values as low as 9 nM, and are highly emissive with lifetimes up to 3.8 μs in cell growth media under aerobic conditions. These long emission lifetimes allow for time-resolved gating to distinguish probe from background autofluorescence from growth media and live cells. X-ray crystallographic analysis revealed structure-activity relationships and the preference or indifference of CYP3A4 toward resolved stereoisomers. Ir(III)-based probes show emission quenching upon CYP3A4 binding, then emission increases following displacement with CYP3A4 inhibitors or substrates. Importantly, the lead probes inhibit the activity of CYP3A4 at concentrations as low as 300 nM in CYP3A4-overexpressing HepG2 cells that accurately mimic human hepatic drug metabolism. Thus, the Ir(III)-based agents show promise as novel chemical tools for monitoring CYP3A4 active site occupancy in a high-throughput manner to gain insight into drug metabolism and drug-drug interactions.

Development and verification of a physiologically based pharmacokinetic model of dronedarone and its active metabolite N-desbutyldronedarone: Application to prospective simulation of complex drug-drug interaction with rivaroxaban.

Despite potential enzyme- and transporter-mediated drug-drug interactions (DDIs) between dronedarone and rivaroxaban in atrial fibrillation (AF) patients, pharmacokinetic/pharmacodynamic data remain limited to guide clinical practice. We aimed to develop, verify and validate a physiologically based pharmacokinetic (PBPK) model of dronedarone and its major metabolite, N-desbutyldronedarone (NDBD), to prospectively interrogate this clinically relevant DDI in healthy and mild renal impairment populations. The middle-out development of our PBPK model combined literature-derived or in-house in vitro data, predicted in silico data and in vivo clinical data. Model verification was performed for intravenous and oral (single and multiple) dosing regimens. Model validation for the accurate prediction of cytochrome P450 (CYP)3A4- and P-glycoprotein-mediated DDI utilized simvastatin and digoxin as respective victim drugs. Rivaroxaban-specific inhibitory parameters of dronedarone and/or NDBD against CYP3A4, CYP2J2, OAT3 and P-glycoprotein were incorporated into the PBPK-DDI model for prospective dronedarone-rivaroxaban DDI simulation. Dronedarone and NDBD PK following clinically relevant doses of 400 mg dronedarone across single and multiple oral dosing were accurately simulated by incorporating effect of auto-inactivation on dose nonlinearities. Following successful model validation, nondose-adjusted rivaroxaban-dronedarone DDI in healthy and mild renal impairment populations revealed simulated rivaroxaban area under the plasma concentration-time curve up to 24 h fold change greater than dose exposure equivalence (0.70-1.43) at 1.65 and 1.84, respectively. Correspondingly, respective major bleeding risk was 4.24 and 4.70% compared with threshold of 4.5% representing contraindicated rivaroxaban-ketoconazole DDI. Our PBPK-DDI model predicted clinically significant dronedarone-rivaroxaban DDI in both healthy and mild renal impairment subjects. Greater benefit vs. risk could be achieved with rivaroxaban dose reductions to at least 15 mg in mild renal impairment subjects on concomitant dronedarone and rivaroxaban.

Treatment of autoimmune hepatitis: Budesonide does not solve our problems.

Treatment of autoimmune hepatitis: Budesonide does not solve our problems.

Activation/Inactivation of Anticancer Drugs by CYP3A4: Influencing Factors for Personalized Cancer Therapy.

Cytochrome P450 3A4 (CYP3A4), one of the most important members of the cytochrome P450 subfamily, is a crucial catalyst in the metabolism of numerous drugs. As it catalyzes numerous processes for drug activation or inactivation, the pharmacological activities and clinical outcomes of anticancer drugs metabolized by CYP3A4 are highly dependent on the enzyme's activity and expression. Due to the complexity of tumor microenvironments and various influencing factors observed in human in vitro models and clinical studies, the pharmacokinetics of most anticancer drugs are influenced by the extent of induction or inhibition of CYP3A4-mediated metabolism, and these details are not fully recognized and highlighted. Therefore, this interindividual variability due to genetic and nongenetic factors, together with the narrow therapeutic index of most anticancer drugs, contributes to their unique set of exposures and responses, which have important implications for achieving the expected efficacy and minimizing adverse events of chemotherapy for cancer in individuals. To elucidate the mechanisms of CYP3A4-mediated activation/inactivation of anticancer drugs associated with personalized therapy, this review focuses on the underlying determinants that contribute to differences in CYP3A4 metabolic activity and provides a comprehensive and valuable overview of the significance of these factors, which differs from current considerations for dosing regimens in cancer therapy. We also discuss knowledge gaps, challenges, and opportunities to explore optimal dosing regimens for drug metabolic activation/inactivation in individual patients, with particular emphasis on pooling and analyzing clinical information that affects CYP3A4 activity. SIGNIFICANCE STATEMENT: This review focuses on anticancer drugs that are activated/deactivated by CYP3A4 and highlights outstanding factors affecting the interindividual variability of CYP3A4 activity in order to gain a detailed understanding of CYP3A4-mediated drug metabolism mechanisms. A systematic analysis of available information on the underlying genetic and nongenetic determinants leading to variation in CYP3A4 metabolic activity to predict therapeutic response to drug exposure, maximize efficacy, and avoid unpredictable adverse events has clinical implications for the identification and development of CYP3A4-targeted cancer therapeutics.

Concomitant Venetoclax and Imatinib for Comanaging Chronic Lymphocytic Leukemia and Chronic Myeloid Leukemia: A Case Report

Patients with synchronous malignancies can be problematic to diagnose and manage because workup and therapeutic targeting for each individual malignancy must be coordinated carefully. This report presents a patient with concurrent chronic myeloid leukemia (CML) and chronic lymphocytic leukemia (CLL) managed with concomitant venetoclax and imatinib. Because imatinib is a moderate cytochrome P450 3A4 inhibitor, close monitoring is required when using with a substrate of 3A4 such as venetoclax. Although the target dose of venetoclax is 400 mg, it was capped at 100 mg due to the interaction. Despite the interaction and possible enhancement of toxicities, the patient has tolerated therapy well, and both diseases have responded to this novel approach. In addition, because aberrant BCL-2 activity has been implicated in CML, the use of venetoclax may contribute to success in the management of this patient's CML. This case report represents the safe concomitant use of venetoclax and imatinib in a patient with synchronous CML and CLL.

Understanding the Risk of Drug Interactions Between Ritonavir-Containing COVID-19 Therapies and Small-Molecule Kinase Inhibitors in Patients With Cancer.

The introduction of COVID-19 therapies containing ritonavir has markedly expanded the scope of use for this medicine. As a strong cytochrome P450 3A4 inhibitor, the use of ritonavir is associated with a high drug interaction risk. There are currently no data to inform clinician regarding the likely magnitude and duration of interaction between ritonavir-containing COVID-19 therapies and small-molecule kinase inhibitors (KIs) in patients with cancer. Physiologically based pharmacokinetic modeling was used to conduct virtual clinical trials with a parallel group study design in the presence and absence of ritonavir (100 mg twice daily for 5 days). The magnitude and time course of changes in KI exposure when coadministered with ritonavir was evaluated as the primary outcome. Dosing of ritonavir resulted in a > 2-fold increase in steady-state area under the plasma concentration-time curve and maximal concentration for six of the 10 KIs. When the KI was coadministered with ritonavir, dose reductions to between 10% and 75% of the original dose were required to achieve an area under the plasma concentration-time curve within 1.25-fold of the value in the absence of ritonavir. To our knowledge, this study provides the first data to assist clinicians' understanding of the drug interaction risk associated with administering ritonavir-containing COVID-19 therapies to patients with cancer who are currently being treated with KIs. These data may support clinicians to make more informed dosing decisions for patients with cancer undergoing treatment with KIs who require treatment with ritonavir-containing COVID-19 antiviral therapies.

Involvement of CYP3A4 and MDR1 in altered metabolism and transport of indinavir in 1,25(OH)2D3-treated Caco-2 cells

Altered drug concentrations may induce unexpected toxicity or treatment failure; thus, understanding the factors that alter the pharmacokinetic profiles of drugs is crucial for optimal disease treatment. Vitamin D receptor (VDR), a nuclear receptor, regulates the expression of cytochrome P450 3A4 (CYP3A4) and multidrug resistance protein 1 (MDR1), which are crucial determinants of drug pharmacokinetics. In this study, we investigated the effects of 1α,25-dihydroxyvitamin D3 [1,25(OH)2D3], a VDR ligand, on the metabolism, transport, and pharmacokinetics of indinavir, a dual substrate of CYP3A4 and MDR1. 1,25(OH)2D3 treatment for three days upregulated the expression levels of CYP3A4 and MDR1 in Caco-2 cells and consequently led to an increase in the level of a metabolite formed via CYP3A4 (indinavir M6) and the efflux ratio of indinavir in transport study. The increase in the metabolic reaction was also confirmed through a metabolism assay performed using the lysate of 1,25(OH)2D3-treated Caco-2 cells. In the Ussing chamber study conducted with the rat intestine, 1,25(OH)2D3 treatment did not alter the transport of indinavir into the basolateral side but increased indinavir M6 formation. Similarly, plasma levels of the metabolite increased in 1,25(OH)2D3-treated rats; however, systemic exposure to indinavir led to insignificant alterations. Considering the overlapping substrate specificities for CYP3A4 and MDR1 and their significant roles in drug pharmacokinetics, VDR may play an important role in drug interactions of CYP3A4 and MDR1 substrates for accessing more effective and safe disease treatments.

Cytochrome P450 3A4 suppression by epimedium and active compound kaempferol leads to synergistic anti-inflammatory effect with corticosteroid.

Introduction: Cytochrome P450 (CYP) 3A4 is a major drug metabolizing enzyme for corticosteroids (CS). Epimedium has been used for asthma and variety of inflammatory conditions with or without CS. It is unknown whether epimedium has an effect on CYP 3A4 and how it interacts with CS. We sought to determine the effects of epimedium on CYP3A4 and whether it affects the anti-inflammatory function of CS and identify the active compound responsible for this effect. Methods: The effect of epimedium on CYP3A4 activity was evaluated using the Vivid CYP high-throughput screening kit. CYP3A4 mRNA expression was determined in human hepatocyte carcinoma (HepG2) cells with or without epimedium, dexamethasone, rifampin, and ketoconazole. TNF-α levels were determined following co-culture of epimedium with dexamethasone in a murine macrophage cell line (Raw 264.7). Active compound (s) derived from epimedium were tested on IL-8 and TNF-α production with or without corticosteroid, on CYP3A4 function and binding affinity. Results: Epimedium inhibited CYP3A4 activity in a dose-dependent manner. Dexamethasone enhanced the expression of CYP3A4 mRNA, while epimedium inhibited the expression of CYP3A4 mRNA and further suppressed dexamethasone enhancement of CYP3A4 mRNA expression in HepG2 cells (p < 0.05). Epimedium and dexamethasone synergistically suppressed TNF-α production by RAW cells (p < 0.001). Eleven epimedium compounds were screened by TCMSP. Among the compounds identified and tested only kaempferol significantly inhibited IL-8 production in a dose dependent manner without any cell cytotoxicity (p < 0.01). Kaempferol in combination with dexamethasone showed complete elimination of TNF-α production (p < 0.001). Furthermore, kaempferol showed a dose dependent inhibition of CYP3A4 activity. Computer docking analysis showed that kaempferol significantly inhibited the catalytic activity of CYP3A4 with a binding affinity of -44.73kJ/mol. Discussion: Inhibition of CYP3A4 function by epimedium and its active compound kaempferol leads to enhancement of CS anti-inflammatory effect.

Drugs That Interact With Colchicine Via Inhibition of Cytochrome P450 3A4 and P-Glycoprotein: A Signal Detection Analysis Using a Database of Spontaneously Reported Adverse Events (FAERS).

Colchicine has a narrow therapeutic index. Its toxicity can be increased due to concomitant exposure to drugs inhibiting its metabolic pathway; these are cytochrome P450 3A4 (CYP3A4) and P-glycoprotein (P-gp). To examine clinical outcomes associated with colchicine drug interactions using the spontaneous reports of the US Food and Drug Administration (FDA) Adverse Event Reporting System (FAERS). We conducted a disproportionality analysis using FAERS data from January 2004 through June 2020. The reporting odds ratio (ROR) and observed-to-expected ratio (O/E) with shrinkage for adverse events related to colchicine's toxicity (ie, rhabdomyolysis/myopathy, agranulocytosis, hemorrhage, acute renal failure, hepatic failure, arrhythmias, torsade de pointes/QT prolongation, and cardiac failure) were compared between FAERS reports. A total of 787 reports included the combined mention of colchicine, an inhibitor of both CYP3A4 and P-gp drug, and an adverse event of interest. Among reports that indicated the severity, 61% mentioned hospitalization and 24% death. A total of 37 ROR and 34 O/E safety signals involving colchicine and a CYP3A4/P-gp inhibitor were identified. The strongest ROR signal was for colchicine + atazanavir and rhabdomyolysis/myopathy (ROR = 35.4, 95% CI: 12.8-97.6), and the strongest O/E signal was for colchicine + atazanavir and agranulocytosis (O/E = 3.79, 95% credibility interval: 3.44-4.03). This study identifies numerous safety signals for colchicine and CYP3A4/P-gp inhibitor drugs. Avoiding the interaction or monitoring for toxicity in patients when co-prescribing colchicine and these agents is highly recommended.

Prasugrel — gone, but not forgotten

AbstractHuman immunodeficiency virus (HIV) infection and certain retroviral therapies are associated with an increased risk of atherosclerosis with plaque rupture resulting in acute coronary syndromes. Therefore, there is often a need to co‐prescribe antiretroviral and cardiovascular therapies, including antiplatelet agents. Antiplatelet agents, such as the P2Y12 receptor antagonists clopidogrel and prasugrel, require activation by cytochrome P450 3A4 (CYP3A4). The P2Y12 receptor antagonist ticagrelor is also metabolised by CYP3A4. Pharmacokinetic enhancers, such as ritonavir and cobicistat, are utilised to increase the systemic exposure of certain agents within multidrug HIV regimens and are potent CYP3A4 inhibitors. Using these drugs together can result in unintended and undesirable drug–drug interactions. A 55‐year‐old male with a history of HIV presented to the emergency department with central chest pain. He was found to have had a non‐ST‐elevation myocardial infarction and was commenced on dual antiplatelet therapy including ticagrelor, anticoagulation and statin therapy, in addition to his usual HIV therapy, Genvoya (elvitegravir, cobicistat, emtricitabine, tenofovir alafenamide). A drug–drug interaction between Genvoya and ticagrelor was identified by the pharmacist, and the patient was switched to prasugrel on the pharmacist's recommendation. Although prasugrel was delisted from the Pharmaceutical Benefits Scheme (PBS) in July 2020, it remains accessible as a non‐PBS medicine. Prasugrel should be considered the P2Y12 antagonist of choice for patients who are on HIV regimens containing a pharmacokinetic enhancer such as ritonavir or cobicistat.

Beyond the Michaelis-Menten: Accurate Prediction of Drug Interactions Through Cytochrome P450 3A4 Induction.

The US Food and Drug Administration (FDA) guidance has recommended several model-based predictions to determine potential drug-drug interactions (DDIs) mediated by cytochrome P450 (CYP) induction. In particular, the ratio of substrate area under the plasma concentration-time curve (AUCR) under and not under the effect of inducers is predicted by the Michaelis-Menten (MM) model, where the MM constant ( ) of a drug is implicitly assumed to be sufficiently higher than the concentration of CYP enzymes that metabolize the drug ( ) in both the liver and small intestine. Furthermore, the fraction absorbed from gut lumen ( ) is also assumed to be one because is usually unknown. Here, we found that such assumptions lead to serious errors in predictions of AUCR. To resolve this, we propose a new framework to predict AUCR. Specifically, was re-estimated from experimental permeability values rather than assuming it to be one. Importantly, we used the total quasi-steady-state approximation to derive a new equation, which is valid regardless of the relationship between and , unlike the MM model. Thus, our framework becomes much more accurate than the original FDA equation, especially for drugs with high affinities, such as midazolam or strong inducers, such as rifampicin, so that the ratio between and becomes low (i.e., the MM model is invalid). Our work greatly improves the prediction of clinical DDIs, which is critical to preventing drug toxicity and failure.