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Sotorasib is a small molecule that irreversibly inhibits the Kirsten rat sarcoma viral oncogene homolog (KRAS) protein with a G12C amino acid substitution mutant protein. The impact of cytochrome P450 (CYP) 3A4 inhibition and induction on sotorasib pharmacokinetics (PKs) was evaluated in 2 separate studies in healthy volunteers (N = 14/study). The impact of CYP3A4 inhibition was interrogated utilizing repeat doses of 200 mg of itraconazole, a strong CYP3A4 inhibitor, on 360 mg of sotorasib PKs. The impact of CYP3A4 induction was interrogated utilizing multiple doses of 600 mg of rifampin, a strong CYP3A4 inducer. Additionally, the impact of organic anion transporting polypeptide (OATP) 1B1/3 inhibition on 960 mg of sotorasib PKs was interrogated after a single dose of 600 mg of rifampin. CYP3A4 inhibition did not significantly impact sotorasib Cmax but did lead to a 26% increase in sotorasib AUCinf. CYP3A4 induction decreased sotorasib Cmax by 35% and AUCinf by 51%. OATP1B1/3 inhibition decreased sotorasib Cmax and AUCinf by 16% and 23%, respectively. These results support that sotorasib can be given together with strong CYP3A4 and OATP1B1/3 inhibitors but the co‐administration of sotorasib and strong CYP3A4 inducers should be avoided. [ABSTRACT FROM AUTHOR]

Cost and availability have often dictated the use of heterologous/alien prolactins in experiments, particularly in vivo. The assumption has been that what is initiated in the target cell is representative of the homologous hormone since many heterologous mammalian prolactins bind to and activate rodent receptors. Here, we examined gene expression in mouse liver in response to a 7‐day treatment with recombinant mouse prolactin (mRecPRL), recombinant ovine prolactin (oRecPRL) and pituitary extract ovine prolactin (oPitPRL). Having established mouse ribosomal protein S9 as the most stable reference gene in the liver in the absence and presence of prolactin treatment, we examined expression of the two most highly expressed prolactin receptors (PRLRs) and three members of the Cyp3a group of cytochrome P450 isoenzymes by qRTPCR. For short form (SF) 3 PRLR, mRecPRL doubled expression while for oRecPRL and oPitPRL expression was only 1.3‐fold control. For the long form (LF) PRLR, changes were similar to those seen for SF 3 PRLR, such that the SF3:LF PRLR ratio remained the same. Expression of the Cyp3as was also dependent on the prolactin origin and, although mRecPRL always stimulated, the other PRLs caused varying results. Compared to control, Cyp3a16 was stimulated 12‐fold by mRecPRL, 3‐fold by oRecPRL, and 6‐fold by oPitPRL. For Cyp3a41, mRecPRL was 3.7‐fold control, oRecPRL was without effect, and oPitPRL was 2‐fold control. Importantly, for Cyp3a44, mRecPRL stimulated 2‐fold, whereas both oRecPRL and oPitPRL had an opposite, inhibitory effect, with expression at 0.5‐fold control. We conclude that homologous hormone had the largest stimulatory effect on expression of all measured genes and that by contrast heterologous hormone showed reduced activity, no activity, or opposite activity, depending on the gene being analyzed. Thus, experimentation using alien heterologous PRL may lead to inaccurate conclusions. [ABSTRACT FROM AUTHOR]

OATP1B facilitates the uptake of xenobiotics into hepatocytes and is a prominent target for drug–drug interactions (DDIs). Reduced systemic exposure of OATP1B substrates has been reported following multiple‐dose rifampicin; one explanation for this observation is OATP1B induction. Non‐uniform hepatic distribution of OATP1B may impact local rifampicin tissue concentrations and rifampicin‐mediated protein induction, which may affect the accuracy of transporter‐ and/or metabolizing enzyme‐mediated DDI predictions. We incorporated quantitative zonal OATP1B distribution data from immunofluorescence imaging into a PBPK modeling framework to explore rifampicin interactions with OATP1B and CYP substrates. PBPK models were developed for rifampicin, two OATP1B substrates, pravastatin and repaglinide (also metabolized by CYP2C8/CYP3A4), and the CYP3A probe, midazolam. Simulated hepatic uptake of pravastatin and repaglinide increased from the periportal to the pericentral region (approximately 2.1‐fold), consistent with OATP1B distribution data. Simulated rifampicin unbound intracellular concentrations increased in the pericentral region (1.64‐fold) compared to simulations with uniformly distributed OATP1B. The absolute average fold error of the rifampicin PBPK model for predicting substrate maximal concentration (Cmax) and area under the plasma concentration–time curve (AUC) ratios was 1.41 and 1.54, respectively (nine studies). In conclusion, hepatic OATP1B distribution has a considerable impact on simulated zonal substrate uptake clearance values and simulated intracellular perpetrator concentrations, which regulate transporter and metabolic DDIs. Additionally, accounting for rifampicin‐mediated OATP1B induction in parallel with inhibition improved model predictions. This study provides novel insight into the effect of hepatic OATP1B distribution on site‐specific DDI predictions and the impact of accounting for zonal transporter distributions within PBPK models. [ABSTRACT FROM AUTHOR]

Genetic variation among inhaled corticosteroid (ICS)-metabolizing enzymes may affect asthma control, but evidence is limited. This study tested the hypothesis that single-nucleotide polymorphisms (SNPs) in Cytochrome P450 3A5 (CYP3A5) would affect asthma outcomes. Patients aged 2–18 years with persistent asthma were recruited to use the electronic AsthmaTracker (e-AT), a self-monitoring tool that records weekly asthma control, medication use, and asthma outcomes. A subset of patients provided saliva samples for SNP analysis and participated in a pharmacokinetic study. Multivariable regression analysis adjusted for age, sex, race, and ethnicity was used to evaluate the impact of CYP3A5 SNPs on asthma outcomes, including asthma control (measured using the asthma symptom tracker, a modified version of the asthma control test or ACT), exacerbations, and hospital admissions. Plasma corticosteroid and cortisol concentrations post-ICS dosing were also assayed using liquid chromatography–tandem mass spectrometry. Of the 751 patients using the e-AT, 166 (22.1%) provided saliva samples and 16 completed the PK study. The e-AT cohort was 65.1% male, and 89.6% White, 6.0% Native Hawaiian, 1.2% Black, 1.2% Native American, 1.8% of unknown race, and 15.7% Hispanic/Latino; the median age was 8.35 (IQR: 5.51–11.3) years. CYP3A5*3/*3 frequency was 75.8% in White subjects, 50% in Native Hawaiians and 76.9% in Hispanic/Latino subjects. Compared with CYP3A5*3/*3, the CYP3A5*1/*x genotype was associated with reduced weekly asthma control (OR: 0.98; 95% CI: 0.97–0.98; p < 0.001), increased exacerbations (OR: 6.43; 95% CI: 4.56–9.07; p < 0.001), and increased asthma hospitalizations (OR: 1.66; 95% CI: 1.43–1.93; p < 0.001); analysis of 3/*3, *1/*1 and *1/*3 separately showed an allelic copy effect. Finally, PK analysis post-ICS dosing suggested muted changes in cortisol concentrations for patients with the CYP3A5*3/*3 genotype, as opposed to an effect on ICS PK. Detection of CYP3A5*3/3, CYPA35*1/*3, and CYP3A5*1/*1 could impact inhaled steroid treatment strategies for asthma in the future. [ABSTRACT FROM AUTHOR]

Mammalian cytochrome P450 drug‐metabolizing enzymes rarely cleave carbon–carbon (C−C) bonds and the mechanisms of such cleavages are largely unknown. We identified two unusual cleavages of non‐polar, unstrained C(sp2)−C(sp3) bonds in the FDA‐approved tyrosine kinase inhibitor pexidartinib that are mediated by CYP3A4/5, the major human phase I drug metabolizing enzymes. Using a synthetic ketone, we rule out the Baeyer–Villiger oxidation mechanism that is commonly invoked to address P450‐mediated C−C bond cleavages. Our studies in 18O2 and H218O enriched systems reveal two unusual distinct mechanisms of C−C bond cleavage: one bond is cleaved by CYP3A‐mediated ipso‐addition of oxygen to a C(sp2) site of N‐protected pyridin‐2‐amines, and the other occurs by a pseudo‐retro‐aldol reaction after hydroxylation of a C(sp3) site. This is the first report of CYP3A‐mediated C−C bond cleavage in drug metabolism via ipso‐addition of oxygen mediated mechanism. CYP3A‐mediated ipso‐addition is also implicated in the regioselective C−C cleavages of several pexidartinib analogs. The regiospecificity of CYP3A‐catalyzed oxygen ipso‐addition under environmentally friendly conditions may be attractive and inspire biomimetic or P450‐engineering methods to address the challenging task of C−C bond cleavages. [ABSTRACT FROM AUTHOR]

Carbamazepine (CBZ) is commonly prescribed for epilepsy and frequently used in polypharmacy. However, concerns arise regarding its ability to induce the metabolism of other drugs, including itself, potentially leading to the undertreatment of co-administered drugs. Additionally, CBZ exhibits nonlinear pharmacokinetics (PK), but the root causes have not been fully studied. This study aims to investigate the mechanisms behind CBZ's nonlinear PK and its induction potential on CYP3A4 and CYP2C9 enzymes. To achieve this, we developed and validated a physiologically based pharmacokinetic (PBPK) parent–metabolite model of CBZ and its active metabolite Carbamazepine-10,11-epoxide in GastroPlus®. The model was utilized for Drug–Drug Interaction (DDI) prediction with CYP3A4 and CYP2C9 victim drugs and to further explore the underlying mechanisms behind CBZ's nonlinear PK. The model accurately recapitulated CBZ plasma PK. Good DDI performance was demonstrated by the prediction of CBZ DDIs with quinidine, dolutegravir, phenytoin, and tolbutamide; however, with midazolam, the predicted/observed DDI AUClast ratio was 0.49 (slightly outside of the two-fold range). CBZ's nonlinear PK can be attributed to its nonlinear metabolism caused by autoinduction, as well as nonlinear absorption due to poor solubility. In further applications, the model can help understand DDI potential when CBZ serves as a CYP3A4 and CYP2C9 inducer. [ABSTRACT FROM AUTHOR]

Vitamin D hydroxylation in the liver/kidney results in conversion to its physiologically active form of 1,25-dihydroxyvitamin D3 [1,25(OH)2D3]. 1,25(OH)2D3 controls gene expression through the nuclear vitamin D receptor (VDR) mainly expressed in intestinal epithelial cells. Cytochrome P450 (CYP) 24A1 is a catabolic enzyme expressed in the kidneys. Interestingly, a recently identified mutation in another CYP enzyme, CYP3A4 (gain-of-function), caused type III vitamin D-dependent rickets. CYP3A are also expressed in the intestine, but their hydroxylation activities towards vitamin D substrates are unknown. We evaluated CYP3A or CYP24A1 activities on vitamin D action in cultured cells. In addition, we examined the expression level and regulation of CYP enzymes in intestines from mice. The expression of CYP3A or CYP24A1 significantly reduced 1,25(OH)2D3-VDRE activity. Moreover, in mice, Cyp24a1 mRNA was significantly induced by 1,25(OH)2D3 in the intestine, but a mature form (approximately 55 kDa protein) was also expressed in mitochondria and induced by 1,25(OH)2D3, and this mitochondrial enzyme appears to hydroxylate 25OHD3 to 24,25(OH)2D3. Thus, CYP3A or CYP24A1 could locally attenuate 25OHD3 or 1,25(OH)2D3 action, and we suggest the small intestine is both a vitamin D target tissue, as well as a newly recognized vitamin D-metabolizing tissue. [ABSTRACT FROM AUTHOR]

Cytochrome P450 (CYP)3A4 induction by drugs and pesticides plays a critical role in the enhancement of pyrrolizidine alkaloid (PA) toxicity as it leads to increased formation of hepatotoxic dehydro-PA metabolites. Addressing the need for a quantitative analysis of this interaction, we developed a physiologically-based toxicokinetic (PBTK) model. Specifically, the model describes the impact of the well-characterized CYP3A4 inducer rifampicin on the kinetics of retrorsine, which is a prototypic PA and contaminant in herbal teas. Based on consumption data, the kinetics after daily intake of retrorsine were simulated with concomitant rifampicin treatment. Strongest impact on retrorsine kinetics (plasma AUC 24 and C max reduced to 67% and 74% compared to the rifampicin-free reference) was predicted directly after withdrawal of rifampicin. At this time point, the competitive inhibitory effect of rifampicin stopped, while CYP3A4 induction was still near its maximum. Due to the impacted metabolism kinetics, the cumulative formation of intestinal retrorsine CYP3A4 metabolites increased to 254% (from 10 to 25 nmol), while the cumulative formation of hepatic CYP3A4 metabolites was not affected (57 nmol). Return to baseline PA toxicokinetics was predicted 14 days after stop of a 14-day rifampicin treatment. In conclusion, the PBTK model showed to be a promising tool to assess the dynamic interplay of enzyme induction and toxification pathways. [ABSTRACT FROM AUTHOR]

Pseudoginsenoside DQ (PDQ), an ocotillol-type ginsenoside, is synthesized with protopanaxadiol through oxidative cyclization. PDQ exhibits good anti-arrhythmia activity. However, the inhibitory effect of PDQ on the cytochrome 450 (CYP450) enzymes and major drug transporters is still unclear. Inhibition of CYP450 and drug transporters may affect the efficacy of the drugs being used together with PDQ. These potential drug–drug interactions (DDIs) are essential for the clinical usage of drugs. In this study, we investigated the inhibitory effect of PDQ on seven CYP450 enzymes and seven drug transporters with in vitro models. PDQ has a significant inhibitory effect on CYP2C19 and P-glycoprotein (P-gp) with a half-inhibitory concentration (IC50) of 0.698 and 0.41 μM, respectively. The inhibition of CYP3A4 and breast cancer-resistant protein (BCRP) is less potent, with IC50 equal to 2.02–6.79 and 1.08 μM, respectively. [ABSTRACT FROM AUTHOR]

Humantenmine, koumine, and gelsemine are three indole alkaloids found in the highly toxic plant Gelsemium. Humantenmine was the most toxic, followed by gelsemine and koumine. The aim of this study was to investigate and analyze the effects of these three substances on tissue distribution and toxicity in mice pretreated with the Cytochrome P450 3A4 (CYP3A4) inducer ketoconazole and the inhibitor rifampicin. The in vivo test results showed that the three alkaloids were absorbed rapidly and had the ability to penetrate the blood-brain barrier. At 5 min after intraperitoneal injection, the three alkaloids were widely distributed in various tissues and organs, the spleen and pancreas were the most distributed, and the content of all tissues decreased significantly at 20 min. Induction or inhibition of CYP3A4 in vivo can regulate the distribution and elimination effects of the three alkaloids in various tissues and organs. Additionally, induction of CYP3A4 can reduce the toxicity of humantenmine, and vice versa. Changes in CYP3A4 levels may account for the difference in toxicity of humantenmine. These findings provide a reliable and detailed dataset for drug interactions, tissue distribution, and toxicity studies of Gelsemium alkaloids. • Cytochrome P450 3A4 crucially impacts the tissue distribution and elimination of the three Gelsemium alkaloids. • The three Gelsemium alkaloids were mainly distributed in the spleen and pancreas after administration. • The difference in cytochrome P450 3A4 content may account for the difference in humantenmine toxicity. [ABSTRACT FROM AUTHOR]

Human cytochrome P450 3A4 (CYP3A4) is a drug‐metabolizing enzyme that is abundantly expressed in the liver and intestine. It is an important issue whether compounds of interest affect the expression of CYP3A4 because more than 30% of commercially available drugs are metabolized by CYP3A4. In this study, we examined the effects of cholesterol and cholic acid on the expression level and activity of CYP3A4 in hCYP3A mice that have a human CYP3A gene cluster and show human‐like regulation of the coding genes. A normal diet (ND, CE‐2), CE‐2 with 1% cholesterol and 0.5% cholic acid (HCD) or CE‐2 with 0.5% cholic acid was given to the mice. The plasma concentrations of cholesterol, cholic acid and its metabolites in HCD mice were higher than those in ND mice. In this condition, the expression levels of hepatic CYP3A4 and the hydroxylation activities of triazolam, a typical CYP3A4 substrate, in liver microsomes of HCD mice were higher than those in liver microsomes of ND mice. Furthermore, plasma concentrations of triazolam in HCD mice were lower than those in ND mice. In conclusion, our study suggested that hepatic CYP3A4 expression and activity are influenced by the combination of cholesterol and cholic acid in vivo. [ABSTRACT FROM AUTHOR]

In this article, we introduce a proof-of-concept strategy, Computational Predictive and Electrochemical Detection of Metabolites (CP-EDM), to expedite the discovery of drug metabolites. The use of a bioactive natural product, piperine, that has a well-curated metabolite profile but an unpredictable computational metabolism (Biotransformer v3.0) was selected. We developed an electrochemical reaction to oxidize piperine into a range of metabolites, which were detected by LC-MS. A series of chemically plausible metabolites were predicted based on ion fragmentation patterns. These metabolites were docked into the active site of CYP3A4 using Autodock4.2. From the clustered low-energy profile of piperine in the active site, it can be inferred that the most likely metabolic position of piperine (based on intermolecular distances to the Fe-oxo active site) is the benzo[d][1,3]dioxole motif. The metabolic profile was confirmed by comparison with the literature, and the electrochemical reaction delivered plausible metabolites, vide infra, thus, demonstrating the power of the hyphenated technique of tandem electrochemical detection and computational evaluation of binding poses. Taken together, we outline a novel approach where diverse data sources are combined to predict and confirm a metabolic outcome for a bioactive structure. [ABSTRACT FROM AUTHOR]

Human liver organoids are in vitro three dimensionally (3D) cultured cells that have a bipotent stem cell phenotype. Translational research of human liver organoids for drug discovery has been limited by the challenge of their low hepatic function compared to primary human hepatocytes (PHHs). Various attempts have been made to develop functional hepatocyte-like cells from human liver organoids. However, none have achieved the same level of hepatic functions as PHHs. We here attempted to culture human liver organoids established from cryopreserved PHHs (PHH-derived organoids), using HYDROX, a chemically defined 3D nanofiber. While the proliferative capacity of PHH-derived organoids was lost by HYDROX-culture, the gene expression levels of drug-metabolizing enzymes were significantly improved. Enzymatic activities of cytochrome P450 3A4 (CYP3A4), CYP2C19, and CYP1A2 in HYDROX-cultured PHH-derived organoids (Org-HYDROX) were comparable to those in PHHs. When treated with hepatotoxic drugs such as troglitazone, amiodarone and acetaminophen, Org-HYDROX showed similar cell viability to PHHs, suggesting that Org-HYDROX could be applied to drug-induced hepatotoxicity tests. Furthermore, Org-HYDROX maintained its functions for up to 35 days and could be applied to chronic drug-induced hepatotoxicity tests using fialuridine. Our findings demonstrated that HYDROX could possibly be a novel biomaterial for differentiating human liver organoids towards hepatocytes applicable to pharmaceutical research. [ABSTRACT FROM AUTHOR]

Purpose: Midostaurin, approved for treating FLT-3-mutated acute myeloid leukemia and advanced systemic mastocytosis, is metabolized by cytochrome P450 (CYP) 3A4 to two major metabolites, and may inhibit and/or induce CYP3A, CYP2B6, and CYP2C8. Two studies investigated the impact of midostaurin on CYP substrate drugs and oral contraceptives in healthy participants. Methods: Using sentinel dosing for participants' safety, the effects of midostaurin at steady state following 25-day (Study 1) or 24-day (Study 2) dosing with 50 mg twice daily were evaluated on CYP substrates, midazolam (CYP3A4), bupropion (CYP2B6), and pioglitazone (CYP2C8) in Study 1; and monophasic oral contraceptives (containing ethinylestradiol [EES] and levonorgestrel [LVG]) in Study 2. Results: In Study 1, midostaurin resulted in a 10% increase in midazolam peak plasma concentrations (Cmax), and 3–4% decrease in total exposures (AUC). Bupropion showed a 55% decrease in Cmax and 48–49% decrease in AUCs. Pioglitazone showed a 10% decrease in Cmax and 6% decrease in AUC. In Study 2, midostaurin resulted in a 26% increase in Cmax and 7–10% increase in AUC of EES; and a 19% increase in Cmax and 29–42% increase in AUC of LVG. Midostaurin 50 mg twice daily for 28 days ensured that steady-state concentrations of midostaurin and the active metabolites were achieved by the time of CYP substrate drugs or oral contraceptive dosing. No safety concerns were reported. Conclusion: Midostaurin neither inhibits nor induces CYP3A4 and CYP2C8, and weakly induces CYP2B6. Midostaurin at steady state has no clinically relevant PK interaction on hormonal contraceptives. All treatments were well tolerated. [ABSTRACT FROM AUTHOR]

Simple Summary: Traditional cancer treatments have long struggled with issues such as toxicity, drug resistance, and financial burdens. However, there is growing interest in using natural compounds, like those found in complementary alternative medicine, due to their ability to influence various molecular pathways with fewer side effects. In our study, we focused on understanding how active components of Cordia myxa could potentially treat liver cancer (LC). By employing network pharmacology techniques, we identified key molecular targets and pathways involved. Through a combination of data analysis and computational modeling, we found that certain genes, including HSP90AA1, ESR1, CYP3A4, CDK1, and MMP9, play crucial roles in LC patient survival. Specifically, our findings suggest that compounds like cosmosiin, rosmarinic acid, quercetin, and rubinin may interact with HSP90AA1, offering a promising avenue for therapeutic intervention. Molecular dynamics simulations further validated these interactions, highlighting the stability of the drug–protein complexes. Overall, our integrated approach underscores the potential of C. myxa in combating LC by modulating cancer-related signaling pathways. Traditional treatments of cancer have faced various challenges, including toxicity, medication resistance, and financial burdens. On the other hand, bioactive phytochemicals employed in complementary alternative medicine have recently gained interest due to their ability to control a wide range of molecular pathways while being less harmful. As a result, we used a network pharmacology approach to study the possible regulatory mechanisms of active constituents of Cordia myxa for the treatment of liver cancer (LC). Active constituents were retrieved from the IMPPAT database and the literature review, and their targets were retrieved from the STITCH and Swiss Target Prediction databases. LC-related targets were retrieved from expression datasets (GSE39791, GSE76427, GSE22058, GSE87630, and GSE112790) through gene expression omnibus (GEO). The DAVID Gene Ontology (GO) database was used to annotate target proteins, while the Kyoto Encyclopedia and Genome Database (KEGG) was used to analyze signaling pathway enrichment. STRING and Cytoscape were used to create protein–protein interaction networks (PPI), while the degree scoring algorithm of CytoHubba was used to identify hub genes. The GEPIA2 server was used for survival analysis, and PyRx was used for molecular docking analysis. Survival and network analysis revealed that five genes named heat shot protein 90 AA1 (HSP90AA1), estrogen receptor 1 (ESR1), cytochrome P450 3A4 (CYP3A4), cyclin-dependent kinase 1 (CDK1), and matrix metalloproteinase-9 (MMP9) are linked with the survival of LC patients. Finally, we conclude that four extremely active ingredients, namely cosmosiin, rosmarinic acid, quercetin, and rubinin influence the expression of HSP90AA1, which may serve as a potential therapeutic target for LC. These results were further validated by molecular dynamics simulation analysis, which predicted the complexes with highly stable dynamics. The residues of the targeted protein showed a highly stable nature except for the N-terminal domain without affecting the drug binding. An integrated network pharmacology and docking study demonstrated that C. myxa had a promising preventative effect on LC by working on cancer-related signaling pathways. [ABSTRACT FROM AUTHOR]

Several commonly used opioid analgesics, such as fentanyl, sufentanil, alfentanil, and hydrocodone, are by report primarily metabolized by the CYP3A4 enzyme. The concurrent use of ritonavir, a potent CYP3A4 inhibitor, can lead to significant drug interactions. Using physiologically based pharmacokinetic (PBPK) modeling and simulation, this study examines the effects of different dosing regimens of ritonavir on the pharmacokinetics of these opioids. The findings reveal that co-administration of ritonavir significantly increases the exposure of fentanyl analogs, with over a 10-fold increase in the exposure of alfentanil and sufentanil when given with ritonavir. Conversely, the effect of ritonavir on fentanyl exposure is modest, likely due to additional metabolism pathways. Additionally, the study demonstrates that the steady-state exposure of hydrocodone and its active metabolite hydromorphone can be increased by up to 87% and 95%, respectively, with concurrent use of ritonavir. The extended-release formulation of hydrocodone is particularly affected. These insights from PBPK modeling provide valuable guidance for optimizing opioid dosing and minimizing the risk of toxicity when used in combination with ritonavir-containing prescriptions. [ABSTRACT FROM AUTHOR]

Tacrolimus (Tac) is pivotal in preventing acute graft-versus-host disease (GVHD) after allogeneic hematopoietic stem cell transplantation (alloHSCT). It has been reported that genetic factors, including CYP3A5*3 and CYP3A4*22 polymorphisms, have an impact on Tac metabolism, dose requirement, and response to Tac. There is limited information regarding this topic in alloHSCT. The CYP3A5 genotype and a low Tac trough concentration/dose ratio (Tac C0/D ratio) can be used to identify fast metabolizers and predict the required Tac dose to achieve target concentrations earlier. We examined 62 Caucasian alloHSCT recipients with a fast metabolizer phenotype (C0/dose ratio ≤ 1.5 ng/mL/mg), assessing CYP3A5 genotypes and acute GVHD incidence. Forty-nine patients (79%) were poor metabolizers (2 copies of the variant *3 allele) and 13 (21%) were CYP3A5 expressers (CYP3A5*1/*1 or CYP3A5*1/*3 genotypes). CYP3A5 expressers had lower C0 at 48 h (3.7 vs. 6.2 ng/mL, p = 0.03) and at 7 days (8.6 vs. 11.4 ng/mL, p = 0.04) after Tac initiation, tended to take longer to reach Tac therapeutic range (11.8 vs. 8.9 days, p = 0.16), and had higher incidence of both global (92.3% vs. 38.8%, p < 0.001) and grade II-IV acute GVHD (61.5% vs. 24.5%, p = 0.008). These results support the adoption of preemptive pharmacogenetic testing to better predict individual Tac initial dose, helping to achieve the therapeutic range and reducing the risk of acute GVHD earlier. [ABSTRACT FROM AUTHOR]

Various cytochrome P450 enzymes (CYPs) that contribute to drug metabolism are expressed in the skin. However, variation among individuals in CYP expression profiles is not well-understood. To investigate CYPs related to the metabolism of transdermal preparations in Japan, multiple skin tissue specimens of individuals of Japanese descent were prepared, and the mRNA expression levels of CYP1A2, CYP3A4, and CYP3A5 were measured. Associations between the expression patterns of these CYPs and body mass index (BMI) were also investigated. There were considerable individual differences in epidermal CYP1A2 mRNA expression levels, and CYP1A2 showed a weak positive correlation with CYP3A4 mRNA expression levels. In contrast to previous results for other organs, epidermal CYP3A4 mRNA expression levels showed a weak positive correlation with BMI. CYP3A4 in the epidermis may have been locally enhanced as a defence mechanism against xenobiotics in response to impaired barrier function. These differences in mRNA expression in the skin may affect the transdermal absorption of drugs, such as lidocaine and fentanyl, which are metabolised by multiple overlapping CYPs. Our study provides new insights into drug metabolism in the skin. These results are valuable for predicting drug effects and transdermal drug transfer rates in Japanese patients. [ABSTRACT FROM AUTHOR]

Intentional and unintentional organophosphorus pesticide exposure is a public health concern. Organothiophosphate compounds require metabolic bioactivation by the cytochrome P450 system to their corresponding oxon analogues to act as potent inhibitors of acetylcholinesterase. It is known that interactions between cytochrome P450 and pesticides include the inhibition of major xenobiotic metabolizing cytochrome P450 enzymes and changes on the genetic level. In this in vitro study, the influence of the pesticides parathion and paraoxon on human cytochrome P450 and associated oxygenases was investigated with a metabolically competent cell line (HepaRG cells). First, the viability of the cells after exposure to parathion and paraoxon was evaluated. The inhibitory effect of both pesticides on cytochrome P450 3A4, which is a pivotal enzyme in the metabolism of xenobiotics, was examined by determining the dose-response curve. Changes on the transcription level of 92 oxygenase associated genes, including those for important cytochrome P450 enzymes, were evaluated. The exposure of HepaRG cells to parathion and paraoxon at concentrations up to 100 µM resulted in a viability of 100 per cent. After exposure for 24 hours, pronounced inhibition of cytochrome P450 3A4 enzyme activity was shown, indicating 50 per cent effective concentrations of 1.2 µM (parathion) and 2.1 µM (paraoxon). The results revealed that cytochrome P450 involved in parathion metabolism were significantly upregulated. Relevant changes of the cytochrome P450 3A4 enzyme activity and significant alteration of genes associated with cytochrome P450 suggest an interference of pesticide exposure with numerous metabolic processes. The major limitations of the work involve the use of a single pesticide and the in vitro model as surrogate to human hepatocytes. The data of this study might be of relevance after survival of acute, life-threatening intoxications with organophosphorus compounds, particularly for the co-administration of drugs, which are metabolized by the affected cytochrome P450. [ABSTRACT FROM AUTHOR]

Ritonavir is a potent inhibitor of the cytochrome P450 3A4 enzyme and is commonly used as a pharmacokinetic (PK) enhancer in antiviral therapies because it increases bioavailability of concomitantly administered antivirals. Decades of experience with ritonavir-enhanced HIV therapies and, more recently, COVID-19 therapies demonstrate that boosting doses of ritonavir are well tolerated, with an established safety profile. The mechanisms of PK enhancement by ritonavir result in the potential for drug–drug interactions (DDIs) with several classes of drugs, thus making co-medication management an important consideration with enhanced antiviral therapies. However, rates of DDIs with contraindicated medications are low, suggesting these risks are manageable by infectious disease specialists who have experience with the use of PK enhancers. In this review, we provide an overview of ritonavir's mechanisms of action and describe approaches and resources available to mitigate adverse events and manage concomitant medication in both chronic and short-term settings. [ABSTRACT FROM AUTHOR]

Avacopan, a complement 5a receptor (C5aR) antagonist approved for treating severe active antineutrophil cytoplasmic autoantibody (ANCA)‐associated vasculitis, was evaluated in 2 clinical drug‐drug interaction studies. The studies assessed the impact of avacopan on the pharmacokinetics (PK) of CYP3A4 substrates midazolam and simvastatin and CYP2C9 substrate celecoxib, and the influence of CYP3A4 inhibitor itraconazole and inducer rifampin on the PKs of avacopan. The results indicated that twice‐daily oral administration of 30 mg of avacopan increased the area under the curve (AUC) of midazolam by 1.81‐fold and celecoxib by 1.15‐fold when administered without food, and twice‐daily oral administration of 30 or 60 mg of avacopan increased the AUC of simvastatin by approximately 2.6‐3.5‐fold and the AUC of the active metabolite β‐hydroxy‐simvastatin acid by approximately 1.4‐1.7‐fold when co‐administered with food. Furthermore, the AUC of avacopan increased by approximately 2.19‐fold when co‐administered with itraconazole and decreased by approximately 13.5‐fold when co‐administered with rifampin. These findings provide critical insights into the potential drug‐drug interactions involving avacopan, which could have significant implications for patient care and treatment planning. (NCT06207682) [ABSTRACT FROM AUTHOR]

Cedirogant (ABBV‐157) is an orally bioavailable inverse agonist of retinoic acid‐related orphan receptor gamma thymus. Data from 2 Phase 1 studies were used to characterize cedirogant pharmacokinetics and evaluate target engagement. Cedirogant plasma concentrations and ex vivo interleukin 17A (IL‐17A) concentrations from healthy participants and participants with moderate to severe psoriasis (PsO) were analyzed in a population pharmacokinetic and pharmacodynamic modeling framework to characterize cedirogant pharmacokinetics following single and multiple doses and assess ex vivo IL‐17A inhibition in relation to cedirogant exposure. Cedirogant population pharmacokinetics were best described by a 2‐compartment pharmacokinetic model with delayed absorption and an enzyme turnover compartment to describe cytochrome P450 3A autoinduction. The pharmacokinetics of cedirogant were comparable between healthy participants and participants with PsO. Cedirogant steady‐state average and maximum plasma concentrations were predicted to be 7.56 and 11.8 mg/L, respectively, for participants with PsO for the 375 mg once‐daily regimen on Day 14. The apparent clearance and apparent volume of distribution for cedirogant were estimated to be 24.5 L/day and 28.2 L, respectively. A direct maximum inhibition model adequately characterized the exposure‐response relationship of cedirogant and ex vivo IL‐17A inhibition, indicating no temporal delay between exposure and response with a saturable inhibition of IL‐17A. Model‐estimated half‐maximal inhibitory concentration and maximum inhibition values for cedirogant inhibition of ex vivo IL‐17A were 0.56 mg/L and 0.76, respectively. The established relationship between cedirogant exposure and biomarker effect supported dose selection for the Phase 2 dose‐ranging study in patients with PsO. [ABSTRACT FROM AUTHOR]

Background: Despite efforts made to reduce morbidity and mortality associated with malaria, especially in sub-Saharan Africa, malaria continues to be a public health concern that requires innovative efforts to reach the WHO-set zero malaria agenda. Among the innovations is the use of artemisinin-based combination therapy (ACT) that is effective against Plasmodium falciparum. Generic artemether–lumefantrine (AL) is used to treat uncomplicated malaria after appropriate diagnosis. AL is metabolized by the cytochrome P450 family of enzymes, such as CYP2B6, CYP3A4 and CYP3A5, which can be under pharmacogenetic influence. Pharmacogenetics affecting AL metabolism, significantly influence the overall anti-malarial activity leading to variable therapeutic efficacy. This study focused on generic AL drugs used in malarial treatment as prescribed at health facilities and evaluated pharmacogenomic influences on their efficacy. Methods: Patients who have been diagnosed with malaria and confirmed through RDT and microscopy were recruited in this study. Blood samples were taken on days 1, 2, 3 and 7 for parasite count and blood levels of lumefantrine, artemisinin, desbutyl-lumefantrine (DBL), and dihydroartemisinin (DHA), the active metabolites of lumefantrine and artemether, respectively, were analysed using established methods. Pharmacogene variation analysis was undertaken using iPLEX microarray and PCR–RFLP. Results: A total of 52 patients completed the study. Median parasite density from day 1 to 7 ranged from 0–2666/μL of blood, with days 3 and 7 recording 0 parasite density. Highest median plasma concentration for lumefantrine and desbutyl lumefantrine, which are the long-acting components of artemisinin-based combinations, was 4123.75 ng/mL and 35.87 ng/mL, respectively. Day 7 plasma lumefantrine concentration across all generic ACT brands was ≥ 200 ng/mL which potentially accounted for the parasitaemia profile observed. Monomorphism was observed for CYP3A4 variants, while there were observed variations in CYP2B6 and CYP3A5 alleles. Among the CYP3A5 genotypes, significant differences in genotypes and plasma concentration for DBL were seen on day 3 between 1/*1 versus *1/*6 (p = 0.002), *1/*3 versus *1/*6 (p = 0.006) and *1/*7 versus *1/*6 (p = 0.008). Day 7 plasma DBL concentrations showed a significant difference between *1/*6 and *1/*3 (p = 0.026) expressors. Conclusions: The study findings show that CYP2B6 and CYP3A5 pharmacogenetic variations may lead to higher plasma exposure of AL metabolites. [ABSTRACT FROM AUTHOR]

There is great interindividual difference in the plasma concentration of quetiapine, and optimizing quetiapine therapy to achieve a balance between efficacy and safety is still a challenge. In our study, a population pharmacokinetic (PPK) model considering genetic information was developed with the expectation of comprehensively explaining this observation in Chinese patients with bipolar disorder. Patients who were dispensed quetiapine and underwent the therapeutic drug monitoring (TDM) were included. The genotypes of CYP3A5*3 , CYP2D6*10 , and ABCB1 C3435T/G2677T were analyzed. Finally, a multivariable linear regression model was applied to describe the PPK of quetiapine considering the covariates weight, height and genotype information. A total of 175 TDM points from 107 patients were adopted for PPK model development. Resultantly, the CL/F of quetiapine in CYP3A5 expressers was 81.1 CL/h, whereas it was 43.6 CL/h in CYP3A5 nonexpressers. The interindividual variability in CL/F was 47.7 %. However, neither the ABCB1 nor CYP2D6 genotype was significantly associated with the predictor of quetiapine clearance in our study. Only trough concentrations were collected, and the span between different points was relatively wide, impeding the application of the typical nonlinear compartment model for PPK analysis. In addition, this was a single-center study which limited the sample of wild-type CYP3A5 carriers. The currently established PPK model of quetiapine considering the contribution of the CYP3A5 genotype could efficiently predict the population and individual pharmacokinetic parameters of Chinese bipolar disorder patients, which could better guide the personalized therapy with quetiapine, thus to achieve the best clinical response. [ABSTRACT FROM AUTHOR]

Breast cancer (BC) is the most prevalent malignancy in women globally. At time of diagnosis, premenopausal BC is considered more aggressive and harder to treat than postmenopausal cases. Cytochrome P450 (CYP) enzymes are responsible for phase I of estrogen metabolism and thus, they are prominently involved in the pathogenesis of BC. Moreover, CYP subfamily 2C and 3A play a pivotal role in the metabolism of taxane anticancer agents. To understand genetic risk factors that may have a role in pre-menopausal BC we studied the genotypic variants of CYP2C8, rs11572080 and CYP3A4, rs2740574 in female BC patients on taxane-based therapy and their association with menopausal status. Our study comprised 105 female patients with histologically proven BC on paclitaxel-therapy. They were stratified into pre-menopausal (n = 52, 49.5%) and post-menopausal (n = 53, 50.5%) groups. Genotyping was done using TaqMan assays and employed on Quantstudio 12 K flex real-time platform. Significant increased frequencies of rs11572080 heterozygous CT genotype and variant T allele were established in pre-menopausal group compared to post-menopausal group (p = 0.023, 0.01, respectively). Moreover, logistic regression analysis revealed a significant association between rs11572080 CT genotype and premenopausal BC. However, regarding rs2740574, no significant differences in genotypes and allele frequencies between both groups were detected. We reported a significant association between CYP2C8 genotypic variants and premenopausal BC risk in Egyptian females. Further studies on larger sample sizes are still needed to evaluate its importance in early prediction of BC in young women and its effect on treatment outcome. [ABSTRACT FROM AUTHOR]

Chlorzoxazone (CZX), a benzoxazolone derivative, has been approved for the treatment of musculoskeletal disorders to relieve localized muscle spasm. However, its idiosyncratic toxicity reported in patients brought attention, particularly for hepatotoxicity. The present study for the first time aimed at the relationship between CZX-induced hepatotoxicity and identification of oxirane intermediate resulting from metabolic activation of CZX. Two N-acetylcysteine (NAC) conjugates (namely M1 and M2) and two glutathione (GSH) conjugates (namely M3 and M4) were detected in rat & human microsomal incubations with CZX (200 μM) fortified with NAC or GSH, respectively. The formation of M1-M4 was NADPH-dependent and these metabolites were also observed in urine or bile of SD rats given CZX intragastrically at 10 mg/kg or 25 mg/kg. NAC was found to attach at C-6' of the benzo group of M1 by sufficient NMR data. CYPs3A4 and 3A5 dominated the metabolic activation of CZX. The two GSH conjugates were also observed in cultured rat primary hepatocytes after exposure to CZX. Inhibition of CYP3A attenuated the susceptibility of hepatocytes to the cytotoxicity of CZX (10–400 μM). The in vitro and in vivo studies provided solid evidence for the formation of oxirane intermediate of CZX. This would facilitate the understanding of the underlying mechanisms of toxic action of CZX. [ABSTRACT FROM AUTHOR]

Background: This study examines the impact of CYP3A4 and CYP 3A5 genotypes on tacrolimus (Tac) pharmacokinetics in Romanian kidney transplanted patients. Methods: We included 112 kidney recipients genotyped for CYP3A5*3, CYP3A4*1.001, and CYP3A4*22. Patients were categorized into poor, intermediate, rapid, and ultra-rapid metabolizers based on the functional defects linked to CYP3A variants. Results: Predominantly male (63.4%) with an average age of 40.58 years, the cohort exhibited a high prevalence of the CYP3A4*1/*1 (86.6%) and CYP3A5*3/*3 (77.7%) genotypes. CYP3A4*1.001 and CYP3A5*1 alleles significantly influenced the Tac concentration-to-dose (C0/D) ratio in various post-transplant periods, while the CYP3A4*22 allele showed no such effect (p = 0.016, p < 0.001). Stepwise regression highlighted the CYP3A4*1.001's impact in early post-transplant phases, with hematocrit and age also influencing Tac variability. Conclusions: The study indicates a complex interaction of CYP3A4 and CYP3A5 genotypes on Tac metabolism, suggesting the necessity for personalized medication approaches based on genetic profiling in kidney transplant recipients. [ABSTRACT FROM AUTHOR]

Pralsetinib, a potent and selective inhibitor of oncogenic RET fusion and RET mutant proteins, is a substrate of the drug metabolizing enzyme CYP3A4 and a substrate of the efflux transporter P‐gp based on in vitro data. Therefore, its pharmacokinetics (PKs) may be affected by co‐administration of potent CYP3A4 inhibitors and inducers, P‐gp inhibitors, and combined CYP3A4 and P‐gp inhibitors. With the frequent overlap between CYP3A4 and P‐gp substrates/inhibitors, pralsetinib is a challenging and representative example of the need to more quantitatively characterize transporter‐enzyme interplay. A physiologically‐based PK (PBPK) model for pralsetinib was developed to understand the victim drug–drug interaction (DDI) risk for pralsetinib. The key parameters driving the magnitude of pralsetinib DDIs, the P‐gp intrinsic clearance and the fraction metabolized by CYP3A4, were determined from PBPK simulations that best captured observed DDIs from three clinical studies. Sensitivity analyses and scenario simulations were also conducted to ensure these key parameters were determined with sound mechanistic rationale based on current knowledge, including the worst‐case scenarios. The verified pralsetinib PBPK model was then applied to predict the effect of other inhibitors and inducers on the PKs of pralsetinib. This work highlights the challenges in understanding DDIs when enzyme‐transporter interplay occurs, and demonstrates an important strategy for differentiating enzyme/transporter contributions to enable PBPK predictions for untested scenarios and to inform labeling. [ABSTRACT FROM AUTHOR]

Lefamulin is being evaluated as a treatment for bacterial exacerbations in cystic fibrosis (CF). Ivacaftor is approved for the treatment of patients with CF. Lefamulin is a moderate CYP3A inhibitor and co‐administration with ivacaftor may result in a drug–drug interaction (DDI). A CF population was built based on literature using the Simcyp Simulator. A previously developed and validated physiologically‐based pharmacokinetic (PBPK) model for ivacaftor was used. A PBPK model for lefamulin was developed and verified. Predicted concentrations and pharmacokinetic (PK) parameters for both ivacaftor and lefamulin in healthy subjects and patients with CF were in reasonable agreement with observed data (within 1.4‐fold, majority within 1.25‐fold). The lefamulin model as a CYP3A4 perpetrator was validated using a different Ki value for oral (p.o.) and intravenous (i.v.) routes. The simulated changes in area under the curve of ivacaftor in patients with CF when co‐administered with p.o. and i.v. lefamulin were weak‐to‐moderate. The predicted change in ivacaftor PK when co‐administered with oral lefamulin was less than observed between ivacaftor and fluconazole. These results suggest a low liability for a DDI between lefamulin and ivacaftor in patients with CF. [ABSTRACT FROM AUTHOR]

Brigatinib is an oral anaplastic lymphoma kinase (ALK) inhibitor approved for the treatment of ALK‐positive metastatic non‐small cell lung cancer. In vitro studies indicated that brigatinib is primarily metabolized by CYP2C8 and CYP3A4 and inhibits P‐gp, BCRP, OCT1, MATE1, and MATE2K. Clinical drug–drug interaction (DDI) studies with the strong CYP3A inhibitor itraconazole or the strong CYP3A inducer rifampin demonstrated that CYP3A‐mediated metabolism was the primary contributor to overall brigatinib clearance in humans. A physiologically‐based pharmacokinetic (PBPK) model for brigatinib was developed to predict potential DDIs, including the effect of moderate CYP3A inhibitors or inducers on brigatinib pharmacokinetics (PK) and the effect of brigatinib on the PK of transporter substrates. The developed model was able to predict clinical DDIs with itraconazole (area under the plasma concentration–time curve from time 0 to infinity [AUC∞] ratio [with/without itraconazole]: predicted 1.86; observed 2.01) and rifampin (AUC∞ ratio [with/without rifampin]: predicted 0.16; observed 0.20). Simulations using the developed model predicted that moderate CYP3A inhibitors (e.g., verapamil and diltiazem) may increase brigatinib AUC∞ by ~40%, whereas moderate CYP3A inducers (e.g., efavirenz) may decrease brigatinib AUC∞ by ~50%. Simulations of potential transporter‐mediated DDIs predicted that brigatinib may increase systemic exposures (AUC∞) of P‐gp substrates (e.g., digoxin and dabigatran) by 15%–43% and MATE1 substrates (e.g., metformin) by up to 29%; however, negligible effects were predicted on BCRP‐mediated efflux and OCT1‐mediated uptake. The PBPK analysis results informed dosing recommendations for patients receiving moderate CYP3A inhibitors (40% brigatinib dose reduction) or inducers (up to 100% increase in brigatinib dose) during treatment, as reflected in the brigatinib prescribing information. [ABSTRACT FROM AUTHOR]

Momelotinib—approved for treatment of myelofibrosis in adults with anemia—and its major active metabolite, M21, were assessed as drug–drug interaction (DDI) victims with a strong cytochrome P450 (CYP) 3A4 inhibitor (multiple‐dose ritonavir), an organic anion transporting polypeptide (OATP) 1B1/1B3 inhibitor (single‐dose rifampin), and a strong CYP3A4 inducer (multiple‐dose rifampin). Momelotinib DDI perpetrator potential (multiple‐dose) was evaluated with CYP3A4 and breast cancer resistance protein (BCRP) substrates (midazolam and rosuvastatin, respectively). DDI was assessed from changes in maximum plasma concentration (Cmax), area under the concentration–time curve (AUC), time to reach Cmax, and half‐life. The increase in momelotinib (23% Cmax, 14% AUC) or M21 (30% Cmax, 24% AUC) exposure with ritonavir coadministration was not clinically relevant. A moderate increase in momelotinib (40% Cmax, 57% AUC) and minimal change in M21 was observed with single‐dose rifampin. A moderate decrease in momelotinib (29% Cmax, 46% AUC) and increase in M21 (31% Cmax, 15% AUC) were observed with multiple‐dose rifampin compared with single‐dose rifampin. Due to potentially counteracting effects of OATP1B1/1B3 inhibition and CYP3A4 induction, multiple‐dose rifampin did not significantly change momelotinib pharmacokinetics compared with momelotinib alone (Cmax no change, 15% AUC decrease). Momelotinib did not alter the pharmacokinetics of midazolam (8% Cmax, 16% AUC decreases) or 1′‐hydroxymidazolam (14% Cmax, 16% AUC decreases) but increased rosuvastatin Cmax by 220% and AUC by 170%. Safety findings were mild in this short‐term study in healthy volunteers. This analysis suggests that momelotinib interactions with OATP1B1/1B3 inhibitors and BCRP substrates may warrant monitoring for adverse reactions or dose adjustments. [ABSTRACT FROM AUTHOR]

To assess the effect of Rehmannioside A on CYP450s activity and to estimate its inhibitory properties. The effect of Rehmannioside A on the activity of major CYP450s in human liver microsomes (HLMs) was assessed with the corresponding substrates and marker reactions, and compared with a blank control and the respective inhibitors. Suppression of CYP3A4, 2C9 and 2D6 was assessed by the dose-dependent assay and fitted with non-competitive or competitive inhibition models. The inhibition of CYP3A4 was determined in a time-dependent manner. Rehmannioside A suppressed the activity of CYP3A4, 2C9, and 2D6 with IC50 values of 10.08, 12.62, and 16.43 μM, respectively. Suppression of CYP3A4 was fitted to a non-competitive model with Ki value of 5.08 μM, whereas CYP2C9 and 2D6 were fitted to a competitive model with Ki values of 6.25 and 8.14 μM. Additionally, the inhibitory effect on CYP3A4 was time-dependent with KI value of 8.47 μM−1 and a Kinact of 0.048 min−1. In vitro suppression of CYP3A, 2C9 and 2D6 by Rehmannioside A indicated that Rehmannioside A or its source herbs may interact with drugs metabolised by these CYP450s, which could guide the clinical application. [ABSTRACT FROM AUTHOR]

Aims: To develop a semi-mechanistic hepatic compartmental model to predict the effects of rifampicin, a known inducer of CYP3A4 enzyme, on the metabolism of five drugs, in the hope of informing dose adjustments to avoid potential drug-drug interactions. Methods: A search was conducted for DDI studies on the interactions between rifampicin and CYP substrates that met specific criteria, including the availability of plasma concentration–time profiles, physical and absorption parameters, pharmacokinetic parameters, and the use of healthy subjects at therapeutic doses. The semi-mechanistic model utilized in this study was improved from its predecessors, incorporating additional parameters such as population data (specifically for Chinese and Caucasians), virtual individuals, gender distribution, age range, dosing time points, and coefficients of variation. Results: Optimal parameters were identified for our semi-mechanistic model by validating it with clinical data, resulting in a maximum difference of approximately 2-fold between simulated and observed values. PK data of healthy subjects were used for most CYP3A4 substrates, except for gilteritinib, which showed no significant difference between patients and healthy subjects. Dose adjustment of gilteritinib co-administered with rifampicin required a 3-fold increase of the initial dose, while other substrates were further tuned to achieve the desired drug exposure. Conclusions: The pharmacokinetic parameters AUCR and CmaxR of drugs metabolized by CYP3A4, when influenced by Rifampicin, were predicted by the semi-mechanistic model to be approximately twice the empirically observed values, which suggests that the semi-mechanistic model was able to reasonably simulate the effect. The doses of four drugs adjusted via simulation to reduce rifampicin interaction. [ABSTRACT FROM AUTHOR]

Aim: A less invasive evaluation method of cytochrome P450 3A (CYP3A) activity provides an important tool for personalized medicine. We aimed to clarify the usefulness of the plasma 6β‐hydroxycortisol to cortisol concentration (6β‐OHF/F) ratio as a minimally invasive CYP3A phenotyping method. Methods: Plasma 6β‐OHF and cortisol concentrations were measured via liquid chromatography/tandem mass spectrometry. The plasma 6β‐OHF/F ratio was compared with 6β‐hydroxylation clearance of endogenous cortisol (CLm(6β); which we previously developed as an index of CYP3A activity) before, during and after oral contraceptive administration in 3 healthy women. The plasma 6β‐OHF/F ratio was observed during oral clarithromycin administration. The plasma 6β‐OHF/F ratio was also measured in 39 healthy participants. Results: The plasma 6β‐OHF/F ratio in 3 healthy women on Day 21 of starting oral contraceptive administration decreased by 39, 49 and 61% compared with Day 0. These values were similar to CLm(6β) values (43, 54 and 59%, respectively). Plasma 6β‐OHF/F ratio and CLm(6β) exhibited a good correlation (r =.9053). The 6β‐OHF/F ratio decreased from 0.00921 to 0.00577 only 3 h following clarithromycin administration. The plasma 6β‐OHF/F ratio ranged 0.00565–0.01556 in 39 healthy participants. Conclusion: Based on its close relationship with CLm(6β) and its decrease upon inhibition by clarithromycin, the plasma 6β‐OHF/F ratio serves as an index of CYP3A activity. Using this minimally invasive index, we can identify patients with extremely low CYP3A activity before treatment initiation and optimize the initial drug dose, thereby mitigating the risk of severe adverse reactions. [ABSTRACT FROM AUTHOR]

Aims: Asundexian is an oral, direct and reversible inhibitor of activated factor XI (FXIa) in development for the treatment of thromboembolic events. This article summarizes results from preclinical and clinical studies, including identification of enzymes involved in asundexian pharmacokinetics, and evaluation of potential target drug–drug interactions. Methods: In vitro studies investigated the substrate characteristics of asundexian towards several cytochrome P450 (CYP) isoforms, hydrolytic enzymes and drug transporters. Inhibition of the amide hydrolysis of asundexian was investigated in vitro for several relevant drugs. Phase 1 studies in healthy male participants investigated the pharmacokinetics (PK) of asundexian upon co‐administration of combined inhibitors or an inducer of P‐gp and CYP3A4 (itraconazole, verapamil or carbamazepine, respectively, or the moderate CYP3A4 inhibitor fluconazole). The pharmacodynamic (PD) markers are activated partial thromboplastin time and FXIa inhibition. Results: Asundexian was predominantly metabolized via carboxylesterase 1 and, to a lesser extent, via CYP3A4 and is a substrate of P‐gp. The asundexian area under the plasma concentration–time curve (AUC) increased by 103% and 75.6% upon combined inhibition of P‐gp and strong or moderate inhibition of CYP3A4, respectively, but was unaffected by moderate CYP3A4 inhibition. Combined P‐gp and CYP3A4 induction by carbamazepine decreased asundexian AUC by 44.4%. PD is concentration‐dependent, thus no differences in maximum responses and recovery commensurate with PK effect(s) were observed. Adverse events were mild and asundexian was well tolerated. Conclusions: The presented studies confirmed that CYP3A4 and P‐gp contribute to asundexian metabolism and excretion. Observed effects were in line with data from a previous mass balance study. [ABSTRACT FROM AUTHOR]

Aims: The pharmacokinetics of doravirine has been studied in clinical trials but not in real‐world settings. Our study aims to characterize and identify factors influencing doravirine (a CYP3A4 substrate) pharmacokinetics in real‐world people with HIV (PWH). Methods: A total of 174 doravirine concentrations measured in 146 PWH followed up in the therapeutic drug monitoring (TDM) program at the University Hospital of Lausanne (Switzerland) between 2019 and 2023 were included in the analysis. Demographic data, clinical information and comedications were recorded during the routine SHCS visits (every 3–6 months). Population pharmacokinetic analysis and Monte Carlo simulations to investigate the clinical significance of the covariates retained in the final model were performed using NONMEM. Results: A one‐compartment model with first‐order absorption and linear elimination best described doravirine pharmacokinetics. Potent CYP3A4 inhibitors and, to a lesser extent age, were the only tested covariates to significantly impact doravirine clearance (CL). Potent CYP3A4 inhibitors reduced CL by 50%, and a 30% decrease in CL was observed in an 80‐year‐old compared with a 55‐year‐old PWH. The effect of potent CYP3A4 inhibitors was prominent, explaining 59% of between‐subject variability in CL. Model‐based simulations predicted 2.8‐fold and 1.6‐fold increases in median steady‐state trough and maximum doravirine concentrations, respectively, when a potent CYP3A4 inhibitor was co‐administered. Conclusions: Our findings show that potent CYP3A4 inhibitors and age influence doravirine pharmacokinetics. However, given the good tolerability of doravirine, dosing adjustment of doravirine is probably not mandatory in those situations. TDM remains useful essentially in specific clinical situations, such as hepatic impairment, suspected nonadherence or pregnancy. [ABSTRACT FROM AUTHOR]

Background: The antiviral letermovir has been increasingly used as off‐label cytomegalovirus prophylaxis in solid organ transplant recipients. Observational studies have reported notable increases in tacrolimus (FK) exposure following letermovir; however, whether a significant interaction occurs in the setting of existing moderate‐to‐strong CYP3A4 inhibition is unknown. Therefore, the purpose of this study was to evaluate FK trough changes before and after letermovir among lung transplant recipients receiving azole antifungal prophylaxis. Methods: This retrospective cohort study included lung transplant recipients newly initiated on letermovir between 2019–2022 following valganciclovir intolerance. Tacrolimus doses and concentrations were collected up to 30 days before and after the letermovir start date. No pre‐emptive FK dose adjustments occurred prior to letermovir initiation. Patients admitted to the hospital or lacking an appropriately timed trough in the pre‐ or post‐period were excluded. Results: A total of 78 lung transplant recipients receiving FK (1.5 mg median total daily dose) and itraconazole (56.4%), isavuconazole (25.6%) or posaconazole (17.9%) prophylaxis were included. Letermovir was started at a median of 8.4 months post‐transplant. The pre‐/post‐letermovir median FK trough was 9.6/9.0 ng/mL (p =.151), median dose‐corrected trough was 4.2/4.7 ng/mL/mg (+11.9%, p =.032), and median weight‐based dose‐corrected trough was 362/326 [ng/mL]/[mg/kg/day] (‐9.9%, p =.036). There was no significant difference in the proportion of patients within their goal trough range before and after letermovir initiation (62% vs. 72%, p =.229). Conclusion: Empiric FK dose adjustments do not appear warranted before letermovir initiation in lung transplant recipients receiving antifungal prophylaxis with moderate‐to‐strong CYP3A4 inhibitors. [ABSTRACT FROM AUTHOR]

Background: We investigated the effect of a 5-day low-dose ritonavir therapy, as it is used in the treatment of COVID-19 with nirmatrelvir/ritonavir, on the pharmacokinetics of three factor Xa inhibitors (FXaI). Concurrently, the time course of the activities of the cytochromes P450 (CYP) 3A4, 2C19, and 2D6 was assessed. Methods: In an open-label, fixed sequence clinical trial, the effect and duration of a 5-day oral ritonavir (100 mg twice daily) treatment on the pharmacokinetics of three oral microdosed FXaI (rivaroxaban 25 µg, apixaban 25 µg, and edoxaban 50 µg) and microdosed probe drugs (midazolam 25 µg, yohimbine 50 µg, and omeprazole 100 µg) was evaluated in eight healthy volunteers. The plasma concentrations of all drugs were quantified using validated liquid chromatography–tandem mass spectrometry (LC-MS/MS) methods and pharmacokinetics were analysed using non-compartmental analyses. Results: Ritonavir increased the exposure of apixaban, edoxaban, and rivaroxaban, but to a different extent the observed area under the plasma concentration–time curve (geometric mean ratio 1.29, 1.46, and 1.87, respectively). A strong CYP3A4 inhibition (geometric mean ratio > 10), a moderate CYP2C19 induction 2 days after ritonavir (0.64), and no alteration of CYP2D6 were observed. A CYP3A4 recovery half-life of 2.3 days was determined. Conclusion: This trial with three microdosed FXaI suggests that at most the rivaroxaban dose should be reduced during short-term ritonavir, and only in patients receiving high maintenance doses. Thorough time series analyses demonstrated differential effects on three different drug-metabolising enzymes over time with immediate profound inhibition of CYP3A4 and only slow recovery after discontinuation. Clinical Trial Registration: EudraCT number: 2021-006643-39. [ABSTRACT FROM AUTHOR]

Enfortumab vedotin is an antibody–drug conjugate comprised of a human monoclonal antibody directed to Nectin-4 and monomethyl auristatin E (MMAE), a microtubule-disrupting agent. The objectives of this review are to summarize the clinical pharmacology of enfortumab vedotin monotherapy and demonstrate that the appropriate dose has been selected for clinical use. Pharmacokinetics (PK) of enfortumab vedotin (antibody–drug conjugate and total antibody) and free MMAE were evaluated in five clinical trials of patients with locally advanced or metastatic urothelial carcinoma (n = 748). Intravenous enfortumab vedotin 0.5–1.25 mg/kg on days 1, 8, and 15 of a 28-day cycle showed linear, dose-proportional PK. No significant differences in exposure or safety of enfortumab vedotin and free MMAE were observed in mild, moderate, or severe renal impairment versus normal renal function. Patients with mildly impaired versus normal hepatic function had a 37% increase in area under the concentration-time curve (0–28 days), a 31% increase in maximum concentration of free MMAE, and a similar adverse event profile. No clinically significant PK differences were observed based on race/ethnicity with weight-based dosing, and no clinically meaningful QT prolongation was observed. Concomitant use with dual P-glycoprotein and strong cytochrome P450 3A4 inhibitors may increase MMAE exposure and the risk of adverse events. Approximately 3% of patients developed antitherapeutic antibodies against enfortumab vedotin 1.25 mg/kg. These findings support enfortumab vedotin 1.25 mg/kg monotherapy on days 1, 8, and 15 of a 28-day cycle. No dose adjustments are required for patients with renal impairment or mild hepatic impairment, or by race/ethnicity. [ABSTRACT FROM AUTHOR]

Tacrolimus (TAC) is an immunosuppressant drug that prevents organ rejection after transplantation. This drug is transported from cells via P-glycoprotein (ABCB1) and is a metabolic substrate for cytochrome P450 (CYP) 3A enzymes, particularly CYP3A4 and CYP3A5. Several single-nucleotide polymorphisms (SNPs) have been identified in the genes encoding CYP3A4, CYP3A5, and ABCB1, including CYP3A4-392A/G (rs2740574), CYP3A5 6986A/G (rs776746), and ABCB1 3435C/T (rs1045642). This study aims to evaluate the association among CYP3A4-392A/G, CYP3A5-6986A/G, and ABCB1-3435C/T polymorphisms and TAC, serum concentration, and biochemical parameters that may affect TAC pharmacokinetics in Mexican kidney transplant (KT) patients. Methods: Forty-six kidney transplant recipients (KTR) receiving immunosuppressive treatment with TAC in different combinations were included. CYP3A4, CYP3A5, and ABCB1 gene polymorphisms were genotyped using qPCR TaqMan. Serum TAC concentration (as measured) and intervening variables were assessed. Logistic regression analyses were performed at baseline and after one month to assess the extent of the association between the polymorphisms, intervening variables, and TAC concentration. Results: The GG genotype of CYP3A5-6986 A/G polymorphism is associated with TAC pharmacokinetic variability OR 4.35 (95%CI: 1.13–21.9; p = 0.0458) at one month of evolution; in multivariate logistic regression, CYP3A5-6986GG genotype OR 9.32 (95%CI: 1.54–93.08; p = 0.028) and the use of medications or drugs that increase serum TAC concentration OR 9.52 (95%CI: 1.79–88.23; p = 0.018) were strongly associated with TAC pharmacokinetic variability. Conclusion: The findings of this study of the Mexican population showed that CYP3A5-6986 A/G GG genotype is associated with a four-fold increase in the likelihood of encountering a TAC concentration of more than 15 ng/dL. The co-occurrence of the CYP3A5-6986GG genotype and the use of drugs that increase TAC concentration correlates with a nine-fold increased risk of experiencing a TAC at a level above 15 ng/mL. Therefore, these patients have an increased susceptibility to TAC-associated toxicity. [ABSTRACT FROM AUTHOR]

The Cytochrome P450 (CYP) enzymes metabolize a variety of drugs, which may potentially lead to toxicity or reduced efficacy when drugs are co-administered. These drug-drug interactions are often manifested by CYP3A4, the most prevalent of all CYP isozymes. We carried out multiple MD simulations employing CAVER to quantify the channels, and Hidden Markov Models (HMM) to characterize the behavior of the gating residues. We discuss channel properties, bottleneck residues with respect to their likelihood to deem the respective channel ingress or egress, gating residues regarding their open or closed states, and channel location relative to the membrane. Channels do not display coordinated motion and randomly transition between different conformations. Gateway residues also behave in a random fashion. Our findings shed light on the equilibrium behavior of the gating residues and channels in the apo state. [ABSTRACT FROM AUTHOR]

The microsomal enzyme system is responsible for the metabolism of pollutants, toxic agents and drugs. With regards to drug metabolism, the activity of the constituent microsomal enzymes results in the reduction of pharmacological and toxicological activity through conversion of hydrophilic (water soluble) compounds to allow urinary excretion. Microsomal enzymes oxidize drugs and steroid hormones in reactions that require adenine nucleotide diphosphate (NADPH). Reversible inhibition reduces enzyme activity through reversible interaction. A covalent bond between the inhibitor and the enzyme can promote the destruction of essential functional groups of the enzyme. Enzyme induction and inhibition are problematic in drug polytherapy. Often the lack of effect of a drug or the side effects that a certain drug exhibits are problems of interaction of drugs with each other in that individually they inhibit or stimulate enzyme activity. [ABSTRACT FROM AUTHOR]

Plasma 4β‐hydroxycholesterol (OHC) has drawn attention as an endogenous substrate indicating CYP3A activity. Plasma 4β‐OHC is produced by hydroxylation by CYP3A4 and CYP3A5 and by cholesterol autoxidation. Plasma 4α‐OHC is produced by cholesterol autoxidation and not affected by CYP3A activity. This study aimed to evaluate the usefulness of plasma 4β‐OHC concentration minus plasma 4α‐OHC concentration (4β‐OHC–4α‐OHC) compared with plasma 4β‐OHC concentration and 4β‐OHC/total cholesterol (TC) ratio in cross‐sectional evaluation of CYP3A activity. Four hundred sixteen general adults were divided into 191 CYP3A5*1 carriers and 225 non‐carriers. Twenty‐six patients with chronic kidney disease (CKD) with CYP3A5*1 allele were divided into 14 with CKD stage 3 and 12 with stage 4–5D. Area under the receiver operating characteristic curve (AUC) for the three indices were evaluated for predicting presence or absence of CYP3A5*1 allele in general adults, and for predicting CKD stage 3 or stage 4–5D in patients with CKD. There was no significant difference between AUC of 4β‐OHC–4α‐OHC and AUC of plasma 4β‐OHC concentration in general adults and in patients with CKD. AUC of 4β‐OHC–4α‐OHC was significantly smaller than that of 4β‐OHC/TC ratio in general adults (p = 0.025), but the two indices did not differ in patients with CKD. In conclusion, in the present cross‐sectional evaluation of CYP3A activity in general adults and in patients with CKD with CYP3A5*1 allele, the usefulness of 4β‐OHC–4α‐OHC was not different from plasma 4β‐OHC concentration or 4β‐OHC/TC ratio. However, because of the limitations in study design and subject selection of this research, these findings require verification in further studies. [ABSTRACT FROM AUTHOR]

Drug development teams must evaluate the risk/benefit profile of new drug candidates that perpetrate drug–drug interactions (DDIs). Real‐world data (RWD) can inform this decision. The purpose of this study was to develop a predicted impact score for DDIs perpetrated by three hypothetical drug candidates via CYP3A, CYP2D6, or CYP2C9 in type 2 diabetes mellitus (T2DM), obesity, or migraine. Optum Market Clarity was analyzed to estimate use of CYP3A, CYP2D6, or CYP2C9 substrates classified in the University of Washington Drug Interaction Database as moderate sensitive, sensitive, narrow therapeutic index, or QT prolongation. Scoring was based on prevalence of exposure to victim substrates and characteristics (age, polypharmacy, duration of exposure, and number of prescribers) of those exposed. The study population of 14,163,271 adults included 1,579,054 with T2DM, 3,117,753 with obesity, and 410,436 with migraine. For T2DM, 71.3% used CYP3A substrates, 44.3% used CYP2D6 substrates, and 44.3% used CYP2C9 substrates. For obesity, 57.1% used CYP3A substrates, 34.6% used CYP2D6 substrates, and 31.0% used CYP2C9 substrates. For migraine, 64.1% used CYP3A substrates, 44.0% used CYP2D6 substrates, and 28.9% used CYP2C9 substrates. In our analyses, the predicted DDI impact scores were highest for DDIs involving CYP3A, followed by CYP2D6, and CYP2C9 substrates, and highest for T2DM, followed by migraine, and obesity. Insights from RWD can be used to estimate a predicted DDI impact score for pharmacokinetic DDIs perpetrated by new drug candidates currently in development. This score can inform the risk/benefit profile of new drug candidates in a target patient population. [ABSTRACT FROM AUTHOR]

Nivasorexant was the first orexin-1 selective receptor antagonist entering clinical development. Despite encouraging preclinical evidence in animal models, a proof-of-concept trial in binge-eating patients recently failed to demonstrate its clinical utility in this population. Across species, nivasorexant clearance was driven by metabolism along seven distinct pathways, five of which were hydroxylation reactions in various locations of the molecule. The exact sites of metabolism were identified by means of mass spectrometry, the use of deuterated analogues, and finally confirmed by chemical references. CYP3A4 was the main cytochrome P450 enzyme involved in nivasorexant metabolism in vitro and accounting for about 90% of turnover in liver microsomes. Minor roles were taken by CYP2C9 and CYP2C19 but individually did not exceed 3–7%. In the rat, nivasorexant was mostly excreted via the bile after extensive metabolism, while urinary excretion was negligible. Only traces of the parent drug were detected in urine, bile, or faeces. [ABSTRACT FROM AUTHOR]

Aims: Previously, retinoids have decreased CYP2D6 mRNA expression in vitro and induced CYP3A4 in vitro and in vivo. This study aimed to determine whether isotretinoin administration changes CYP2D6 and CYP3A activities in patients with severe acne. Methods: Thirty‐three patients (22 females and 11 males, 23.5 ± 6.0 years old) expected to receive isotretinoin treatment completed the study. All participants were genotyped for CYP2D6 and CYP3A5. Participants received dextromethorphan (DM) 30 mg orally as a dual‐probe substrate of CYP2D6 and CYP3A activity at two study timepoints: pre‐isotretinoin treatment and with isotretinoin for at least 1 week. The concentrations of isotretinoin, DM and their metabolites were measured in 2‐h postdose plasma samples and in cumulative 0‐4‐h urine collections using liquid chromatography‐mass spectrometry. Results: In CYP2D6 extensive metabolizers, the urinary dextrorphan (DX)/DM metabolic ratio (MR) (CYP2D6 activity marker) was numerically, but not significantly, lower with isotretinoin administration compared to pre‐isotretinoin (geometric mean ratio [GMR] [90% confidence interval (CI)] 0.78 [0.55, 1.11]). The urinary 3‐hydroxymorphinan (3HM)/DX MR (CYP3A activity marker) was increased (GMR 1.18 [1.03, 1.35]) and the urinary DX‐O‐glucuronide/DX MR (proposed UGT2B marker) was increased (GMR 1.22 [1.06, 1.39]) with isotretinoin administration compared to pre‐isotretinoin. Conclusions: Administration of isotretinoin did not significantly reduce CYP2D6 activity in extensive metabolizers, suggesting that the predicted downregulation of CYP2D6 based on in vitro data does not translate into humans. We observed a modest increase in CYP3A activity (predominantly CYP3A4) with isotretinoin treatment. The data also suggest that DX glucuronidation is increased following isotretinoin administration. [ABSTRACT FROM AUTHOR]

Background and Objective: Esmethadone (dextromethadone; d-methadone; S-methadone (+)-methadone; REL-1017) is the opioid inactive dextro-isomer of racemic methadone. Esmethadone is a low potency N-methyl-D-aspartate (NMDA) receptor channel blocker with higher affinity for GluN2D subtypes. Esmethadone showed robust, rapid, and sustained antidepressant effects in patients with major depressive disorder (MDD) with inadequate response to ongoing serotonergic antidepressant treatment. Methods: Here we described the results of in vitro and phase 1 clinical trials aimed at investigating the esmethadone metabolism and possible drug-drug interactions. Results: Esmethadone is primarily metabolized to EDDP (2-ethylene-1,5-dimethyl-3,3-diphenylpyrrolidine) by multiple enzymes, including CYP3A4/5 and CYP2B6. In vitro studies showed that esmethadone inhibits CYP2D6 with IC50 of 9.6 μM and is an inducer of CYP3A4/5. The clinical relevance of the inhibition of CYP2D6 and the induction of CYP3A4 were investigated by co-administering esmethadone and dextromethorphan (a substrate for CYP2D6) or midazolam (a substrate for CYP3A4) in healthy volunteers. The administration of esmethadone at the dosage of 75 mg (which is the loading dose administered to patients in MDD clinical trials) significantly increased the exposure (AUC) of both dextromethorphan and its metabolite dextrorphan by 2.71 and 3.11-fold, respectively. Esmethadone did not modify the pharmacokinetic profile of midazolam, while it increased Cmax and AUC of its metabolite 1′-hydroxymidazolam by 2.4- and 3.8-fold, respectively. A second study evaluated the effect of the CYP3A4 inhibitor cobicistat on the pharmacokinetics of esmethadone. Cobicistat slightly increase (+32%) the total exposure (AUC0–inf) of esmethadone. Conclusions: In summary, esmethadone demonstrated a negligible effect on CYP3A4 induction and its metabolism was not meaningfully affected by strong CYP3A4 inhibitors while it increased exposure of CYP2D6-metabolized drugs. [ABSTRACT FROM AUTHOR]

Introduction. Tacrolimus is an immunosuppressive drug widely used in liver transplantation, which presents great interindividual variability, which is considered associated with the frequency of CYP3A5 and MDR-1 polymorphisms. The objective of this study was to evaluate the frequency of the rs776746, rs2032582 and rs1045642 polymorphisms and their association with clinical rejection and drug toxicity. Methods. Seventeen immunosuppressed patients with tacrolimus who underwent a liver transplant at the Hospital San Vicente Fundación Rionegro between 2020 and 2022 were included, with survival of more than one month. Clinical variables, acute rejection and pharmacological toxicity were evaluated. The study genes were sequenced by PCR, comparing their expression or not in each of the patients. Results. 43% of the patients were classified as CYP3A5*1/*1 and CYP3A5*1/*3, among which an association was found with increased rates of clinical acute rejection when compared with non-expressive patients (100% vs. 44%, p=0.05). There were no differences in drug toxicity or other outcomes. The rs2032582 polymorphism was found in 50% and rs1045642 in 23.5% of patients; however, no association with rejection or other clinical events was identified. Conclusions. An association was found between the CYP3A5*1/*1 and CYP3A5*1/*3 genotype and the clinical rejection rate. However, a larger sample is required to validate these data and propose models of personalized medicine. [ABSTRACT FROM AUTHOR]

CYP3A4 is a major hepatic enzyme essential for metabolizing diverse chemical entities. The development of CYP3A4 substrate and inhibitor classifier models is a valuable research strategy to prevent toxicokinetics. Currently, no molecular docking model is available to classify the substrates and inhibitors for a wide range of chemical entities. This study generated a CYP3A4 substrate-inhibitor classifier model using multivariate analysis of selected variables from site of metabolism (SOM)-based docking results and molecular descriptors. CYP3A4 SOM-based molecular docking experiment was performed on the substrates and inhibitors from the DrugBank database. The relevant descriptors were selected using the area under the receiving operating curve (AUROC) and boxplot analysis. The selected variables were used to generate a CYP3A4 substrate-inhibitor classifier model using multivariate analysis. Two complexes were selected for molecular dynamic simulations. A total of 326 substrates and 154 inhibitors were successfully docked. The SOM-based docking model predicted 78.5% SOM correctly of the substrates. The CDOCKER energy, improper dihedral energy, potential energy, initial RMS (root mean square) gradient, and RMS gradient demonstrated acceptable AUROC, sensitivity, specificity, and Youden's index results. The selected variables were subjected to multivariate analysis, and the PLS-DA analysis classification model showed promising performance in predicting chemical entities' behavior as substrates or inhibitors. This model classified the external samples correctly with over 70.0% prediction accuracy. Molecular dynamic simulations showed that the selected complexes obtained from the docking model produced stable complexes. The classifier model is applicable as a research tool for the early stages of drug discovery. In silico structure-based analysis of new chemical entities toward CYP3A4 metabolism and inhibitory activity is helpful in pharmacokinetic research. This study analysed the results of SOM-based molecular docking and relevant descriptors using multivariate analysis to generate CYP3A4 substrate-inhibitor classifier model. [ABSTRACT FROM AUTHOR]

Tacrolimus is metabolized by cytochrome P450 3A (CYP3A) and is susceptible to interactions with the CYP3A and P‐glycoprotein inducer St. John's Wort (SJW). CYP3A isozymes are predominantly expressed in the small intestine and liver. Prolonged‐release tacrolimus (PR‐Tac) is largely absorbed in distal intestinal segments and is less susceptible to CYP3A inhibition. The effect of induction by SJW is unknown. In this randomized, crossover trial, 18 healthy volunteers received single oral tacrolimus doses (immediate‐release [IR]‐Tac or PR‐Tac, 5 mg each) alone and during induction by SJW. Concentrations were quantified using ultra‐high performance liquid chromatography coupled with tandem mass spectrometry and non‐compartmental pharmacokinetics were evaluated. SJW decreased IR‐Tac exposure (area under the concentration‐time curve) to 73% (95% confidence interval 60%‐88%) and maximum concentration (Cmax) to 61% (52%‐73%), and PR‐Tac exposure to 67% (55%‐81%) and Cmax to 69% (58%‐82%), with no statistical difference between the 2 formulations. The extent of interaction appeared to be less pronounced in volunteers with higher baseline CYP3A4 activity and in CYP3A5 expressors. In contrast to CYP3A inhibition, CYP3A induction by SJW showed a similar extent of interaction with both tacrolimus formulations. A higher metabolic baseline capacity appeared to attenuate the extent of induction by SJW. [ABSTRACT FROM AUTHOR]