CYP3A4-mediated Metabolism Research Articles

Abstract P4-08-13: Evaluating CYP3A4-Mediated Drug Interaction Risks for Vepdegestrant, a PROteolysis TArgeting Chimera (PROTAC) Estrogen Receptor (ER) Degrader, in Combination With Cyclin-Dependent Kinase (CDK)4/6 Inhibitors and Everolimus

Abstract Background: Vepdegestrant (ARV-471) is an oral PROTAC ER degrader that has shown a manageable safety profile and signals of clinical efficacy as a single agent and in combination with the CDK4/6 inhibitor palbociclib in a phase 1/2 study in patients with ER+/human epidermal growth factor receptor 2 (HER2)- advanced breast cancer who had received prior treatments (NCT04072952). Ongoing studies are evaluating vepdegestrant in combination with other anticancer therapies in patients with ER+/HER2- advanced breast cancer, including with abemaciclib (NCT05548127) or ribociclib (NCT05573555) in the phase 1b/2 TACTIVE-U umbrella study and with everolimus in the phase 1b TACTIVE-E study (NCT05501769). We performed a clinical study in healthy female adults to evaluate the effect of multiple doses of vepdegestrant on the pharmacokinetics (PK) of midazolam, a sensitive index substrate of CYP3A4. Based on the clinical study results, we assessed the potential risk of CYP3A4-mediated drug interactions with anticancer agents currently being tested in combination with vepdegestrant. Method: A phase 1, open-label, 2-period, fixed-sequence study was conducted in 15 healthy female adults of non-childbearing potential (NCT06256510). In period 1, participants received a single oral dose of midazolam 2 mg alone, followed by a ≥1 day washout period. In period 2, participants received vepdegestrant 200 mg orally once daily (QD) under fed condition on days 1-15, and a single oral dose of midazolam 2 mg on days 1 and 15 ≈1 hour after vepdegestrant dosing. Serial plasma samples were analyzed to estimate the effect of vepdegestrant on midazolam PK. Static mechanistic models1,2,3, incorporating findings of this clinical study and drug interaction mechanisms as victim of CYP3A4-mediated metabolism for each combination partner, were used to calculate the predicted effect of vepdegestrant 200 mg QD administration on the PK of palbociclib, abemaciclib, ribociclib, and everolimus, represented as the ratio of area under the concentration-time curve (AUC) in the presence and absence of vepdegestrant (AUCr). Results: A total of 14 participants were eligible for evaluation of the effect of vepdegestrant 200 mg QD on the plasma AUC from time 0 extrapolated to infinite time (AUCinf) of midazolam. Midazolam AUCinf was approximately 74% higher when midazolam was given after multiple doses of vepdegestrant compared to when midazolam was given alone. Multiple doses of vepdegestrant were generally well tolerated by all participants; no serious or severe adverse events, and no discontinuations or dose reductions due to adverse events were reported. Based on the observed changes in midazolam AUC, the predicted effect of vepdegestrant on combination partners, expressed as AUCr, ranged from 1.13–1.29 for palbociclib, 1.37–1.55 for abemaciclib, 1.00–1.04 for ribociclib, and 1.38–1.63 for everolimus. These predicted effects based on CYP3A4 metabolism are considered negligible or minor and unlikely to have major impact in clinical combinations. Conclusions: Vepdegestrant shows a weak inhibitory effect on CYP3A4-mediated metabolism in the clinical study with midazolam. The study results, combined with mathematical modeling, suggest low potential of meaningful drug interactions for vepdegestrant in combination with CDK4/6 inhibitors and everolimus. Clinical data are anticipated from ongoing studies of vepdegestrant in combination with other anticancer therapies in patients with ER+/HER2- advanced breast cancer. Citations: 1. Fahmi OA, Maurer TS, et al (2008) Drug Metab Dispos, 36 2. Fahmi, OA, S Hurst, et al (2009) Drug Metab Dispos, 37 3. FDA Guidance for Industry (2020) In Vitro Drug Interaction Studies Citation Format: Stefanie Drescher, Weiwei Tan, Yuanyuan Zhang, Julia Perkins Smith. Evaluating CYP3A4-Mediated Drug Interaction Risks for Vepdegestrant, a PROteolysis TArgeting Chimera (PROTAC) Estrogen Receptor (ER) Degrader, in Combination With Cyclin-Dependent Kinase (CDK)4/6 Inhibitors and Everolimus [abstract]. In: Proceedings of the San Antonio Breast Cancer Symposium 2024; 2024 Dec 10-13; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2025;31(12 Suppl):Abstract nr P4-08-13.

Erlotinib-A substrate and inhibitor of OATP2B1: pharmacokinetics and CYP3A-mediated metabolism in rSlco2b1-/- and SLCO2B1+/+ rats.

Erlotinib-A substrate and inhibitor of OATP2B1: pharmacokinetics and CYP3A-mediated metabolism in rSlco2b1-/- and SLCO2B1+/+ rats.

Abstract CT176: Pharmacokinetics (PK) of the novel nonsteroidal CYP11A1 inhibitor opevesostat (ODM-208/MK-5684): Interaction potential with midazolam and effect of food

Abstract Background: Opevesostat is an oral, nonsteroidal small molecule that selectively inhibits the mitochondrial cholesterol side-chain cleavage enzyme cytochrome P450 11A1 (CYP11A1). In vitro, the active metabolite M1 of opevesostat showed a time-dependent inhibition of CYP3A4. It is crucial to investigate factors that may influence the PK of this novel drug. We present two such PK analyses: first, opevesostat’s potential drug-drug interaction (DDI) with midazolam (a sensitive CYP3A4 substrate) in a dedicated cohort of the phase 1/2 CYPIDES trial in participants (pts) with previously treated metastatic castration-resistant prostate cancer (mCRPC); and second, the effect of food in healthy pts in the open-label, 2-period crossover, single-dose, single-site phase 1 5684-007 study. Methods: In the DDI cohort of CYPIDES, 14 males with progressive mCRPC received oral midazolam 1 mg 1 day before and again 7 days after continuous opevesostat 5 mg BID dosing. In the 5684-007 study, 14 healthy males were allocated to receive a single dose of opevesostat 5 mg after a high-fat meal (n=7) or in a fasted state (n=7). After a ≥7-day washout period, pts crossed over to the opposite treatment. Safety was monitored in both studies. Validated liquid chromatography-tandem mass spectrometry of blood samples was used to determine midazolam and opevesostat concentrations. All PK parameters were calculated by a noncompartmental method. The effect of opevesostat on Cmax, AUCt and AUCinf of midazolam and the effect of food on Cmax, AUCinf and AUClast of opevesostat are presented as geometric mean ratios (GMR; 90% CI). Results: Among pts with mCRPC, midazolam PK were not altered by opevesostat. The AUCs had similar ratios between midazolam with opevesostat vs midazolam alone, with a GMR for AUCt of 0.88 (90% CI 0.75-1.03) and for AUCinf of 0.85 (90% CI 0.72-1.00). For Cmax, the GMR was 0.92 (90% CI 0.73-1.16). Among healthy pts, food did not affect the total exposure to opevesostat. The GMR for fed vs fasted state was 0.97 (90% CI 0.93-1.02) for AUCinf and 0.97 (90% CI 0.92-1.02) for AUClast. A high-fat meal was associated with a decrease in Cmax, with a GMR for fed vs fasted state of 0.59 (90% CI 0.52-0.68), and a delay in median Tmax from 0.50 hr to 2.00 hr. In both studies, opevesostat plasma concentration-time profiles and PK parameters were consistent with previous results. Safety findings in both cohorts were consistent with previous experience. Conclusions: Opevesostat and its metabolite M1 did not inhibit CYP3A4-mediated metabolism and can be safely co-administered with other drugs metabolized through this pathway. Total exposure for opevesostat was not impacted by food. A decrease in opevesostat Cmax and delay in Tmax with a high-fat meal was not unexpected; this observation is unlikely to impact clinical practices around opevesostat administration. Citation Format: Natalie Cook, Jan de Hoon, Arif Hussain, Robert H. Jones, Robert J. Jones, Alice Bernard-Tessier, Ruiyang Yan, Magdalena Meissner, Tarja Naukkarinen, Jonathan Belman, Zhiqing Xu, An Bautmans, Aubrey Stoch, Virpi Mononen, Pasi Pohjanjousi, Chris Garratt, Christian Poehlein, Karim Fizazi. Pharmacokinetics (PK) of the novel nonsteroidal CYP11A1 inhibitor opevesostat (ODM-208/MK-5684): Interaction potential with midazolam and effect of food [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_2):Abstract nr CT176.

CYP3A4 activity variations can lead to stratified metabolism of abemaciclib.

CYP3A4 activity variations can lead to stratified metabolism of abemaciclib.

Determination and Disposition of the Aromatase Inhibitor Exemestane in CYP3A-Deficient Mice.

Exemestane, a steroidal aromatase inhibitor prescribed for post-menopausal women with estrogen receptor-positive breast cancer, is associated with debilitating musculoskeletal side effects and exhibits considerable interindividual variability in systemic exposure. Although exemestane is metabolized mainly by cytochrome P-450 3A4, the contribution of this metabolic pathway to the elimination of exemestane and its drug-drug interaction liabilities remains uncertain. Here, we developed a novel quantification method for exemestane and applied it to evaluate the role of CYP3A-mediated metabolism in the pharmacokinetics of exemestane using wild-type and Cyp3a-deficient mice. Liquid chromatography-mass spectrometry was used to quantify exemestane in selective reaction monitoring (SRM) mode, in which precursor ion and fragment ion data were obtained simultaneously. Validation results demonstrated that the developed method was accurate and precise, and sufficiently sensitive to be applied to murine pharmacokinetic studies involving serial blood sampling strategies. Although in vitro studies indicate that exemestane undergoes extensive metabolism in the liver to inactive metabolites by CYP3A4, complete Cyp3a deficiency in mice did not influence the systemic exposure to exemestane. This unequivocal evidence from genetic approaches using preclinical mouse models confirms that the potential for such DDI liabilities is very low. Our newly developed method provides a robust platform for further pharmacokinetic studies with exemestane in mice to delineate DDI liabilities and define the mechanisms of elimination.

Drug-drug interaction between letermovir and ciclosporin in allogeneic haematopoietic cell transplantation recipients.

Letermovir, a cytomegalovirus prophylactic agent, is widely used in allogeneic HSCT recipients. As an inhibitor of cytochrome P450 3A4 (CYP3A4) and P-glycoprotein (P-gp), it may interact with ciclosporin A (CsA), potentially impacting its pharmacokinetics. Inflammation can impair CYP3A-mediated drug metabolism, with severe inflammation reducing CsA metabolism. However, current data on the drug-drug interaction (DDI) between CsA and letermovir as a perpetrator are limited to healthy volunteers and lack evaluation in HSCT patients, particularly under minimal inflammation conditions, where such DDIs may occur. This retrospective, observational, single-centre study included seven adult HSCT recipients who received CsA and letermovir concurrently with no-to-mild inflammation (C-reactive protein ≤40 mg/L). CsA concentration/dose (C/D) ratios were calculated before and after letermovir initiation. Changes in CsA pharmacokinetics were analysed using Wilcoxon signed-rank tests. A 240 mg dose of letermovir once daily significantly increased the median CsA C/D ratio from 0.39 to 0.90 (P = 0.0156) and the median CsA trough concentration from 136 µg/L to 240 µg/L (P = 0.0156). These changes were attributed to CYP3A4 inhibition by letermovir, given the stable no-to-mild inflammatory status and the lack of additional DDI. Letermovir significantly decreased CsA metabolism in HSCT patients through CYP3A4 inhibition, with clinical implications for dosing precision. Close therapeutic drug monitoring (generally twice weekly) is therefore recommended during letermovir initiation and discontinuation to mitigate risks of subtherapeutic levels or toxicity. This study highlights the significance of assessing DDIs in HSCT, where inflammation modulates metabolic interactions resulting in a complex interplay such as a disease-drug-drug interaction (D-DDI).

Preclinical Evidence for a Drug-Drug Interaction Between Cannabinol and Melatonin.

The worldwide legalization of medicinal cannabis has led to an increased use of products made by commercial operators. These products often contain minor cannabinoids such as cannabinol (CBN) which are advertised to improve sleep. Products are also available in which CBN is combined with conventional therapies, with a common product containing both CBN and the widely used sleep-aid melatonin. The combination of CBN and melatonin provides potential for a pharmacokinetic drug-drug interaction (DDI) given that cannabinoids are known to inhibit drug-metabolizing enzymes. Indeed, we recently reported that CBN potently inhibited the CYP1A2-mediated metabolism of caffeine. CYP1A2 is the major hepatic enzyme involved in the metabolism of melatonin; thus, in this study, we aimed to examine whether CBN inhibited CYP1A2-mediated metabolism of melatonin invitro and invivo. We found CBN potently inhibited CYP1A2-mediated metabolism of melatonin and increased the apparent oral bioavailability of melatonin in mice with a four-fold increase in the plasma melatonin exposure. Our results provide an additional example of a potential DDI involving melatonin.

Heterotropic Activation of Cytochrome P450 3A4 by Perillyl Alcohol.

Background/Objectives: Perillyl alcohol (POH), a monoterpene natural product derived from the essential oils of plants such as perilla (Perilla frutescens), is currently in phase I and II clinical trials as a chemotherapeutic agent. In this study, we investigated the effect of POH on cytochrome P450 (CYP) activity for evaluating POH-drug interaction potential. Methods: The investigation was conducted using pooled human liver microsomes (HLMs), recombinant CYP3A4 (rCYP3A4) enzymes, and human pluripotent stem cell-derived hepatic organoids (hHOs) employing liquid chromatography-tandem mass spectrometry. Results: POH inhibited the activities of CYP2A6 and CYP2B6 with Ki of 6.35 and 3.78 μM, respectively, whereas it stimulated CYP3A4 activity in pooled HLMs incubated with midazolam (MDZ). In a direct CYP inhibition assay using HLMs, activities of CYP2C9, CYP2C19, and CYP2E1 were also inhibited by POH, with IC50 values greater than 50 μM, but those of CYP1A2, CYP2C8, CYP2D6, and CYP3A4 (testosterone) were not significantly inhibited. In pooled HLMs, the Vmax/Km value of 1'-hydroxy MDZ, but not that of 4-hydroxy MDZ, was increased 2.7-fold by 100 μM POH compared with that in the absence of POH. Moreover, stimulation of MDZ 1'-hydroxylation by CYP3A4 was observed in hHOs and rCYP3A4 with cytochrome b5 but not rCYP3A4 without cytochrome b5. Furthermore, activation of CYP3A4-mediated metabolism by POH was observed in HLMs incubated with fimasartan but not atorvastatin, buspirone, donepezil, nifedipine, or tadalafil, suggesting a substrate-dependent activation of CYP3A4 by POH. Conclusions: POH inhibits CYP2A6 and CYP2B6, but it activates CYP3A4. These findings underscore the need for further evaluation of the interactions of clinical drugs with POH.

Interindividual variability in CYP3A-mediated venetoclax metabolism invitro and invivo in patients with chronic lymphocytic leukemia.

Venetoclax is a first-in-class orally administered B-cell lymphoma-2 inhibitor used to treat chronic lymphocytic leukemia (CLL). Venetoclax is primarily metabolized in the liver by cytochrome P450 (CYP) 3A4 to its major metabolite M27, via M5, and M2, M3, and M4 via oxidation. Although venetoclax is a breakthrough in CLL treatment, managing drug safety and toxicity remains a clinical challenge. The objectives of this study were to investigate how individual CYP3A activity and protein expression affect hepatic venetoclax metabolism invitro and examine whether plasma 4β-hydroxycholesterol (4β-HC)/cholesterol ratio can predict venetoclax metabolism invitro and invivo. In human liver microsomes (n = 20) and primary human hepatocytes (n = 15), venetoclax metabolite formation varied widely between donors and significantly correlated with CYP3A activity (midazolam 1'-hydroxylation) and CYP3A4 protein expression. Venetoclax metabolite formation positively correlated with 4β-HC/cholesterol ratio in plasma samples from the matched non-infant donors (n = 14, ages 3-63 years). In an observational pilot study of real-world patients with CLL (n = 12, ages 56-84 years) treated with venetoclax, the plasma M3/venetoclax metabolic ratio negatively correlated with plasma 4β-HC/cholesterol ratio and positively correlated with patient age. Plasma 4β-HC/cholesterol ratio negatively correlated with patient age. Differences between the invitro data, which showed a positive association between venetoclax metabolism, hepatic CYP3A markers, and plasma 4β-HC/cholesterol ratio, and the invivo findings in patients with CLL could be due to age or other factors regulating plasma 4β-HC/cholesterol and/or venetoclax disposition. Future studies with larger sample sizes are needed to investigate age-related changes in venetoclax metabolism and plasma 4β-HC/cholesterol ratio.

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

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

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

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

DNA Methylation in the CYP3A Distal Regulatory Region (DRR) Is Associated with the Expression of CYP3A5 and CYP3A7 in Human Liver Samples.

CYP3As are important drug-metabolizing enzymes in the liver. The causes for large inter-person variability in CYP3A expression/activity remain poorly understood. DNA methylation broadly regulates gene expression and the developmental transition from fetal CYP3A7 to adult CYP3A4, and CpG methylation upstream of the CYP3A4 promoter is associated with its expression. However, because non-promoter CYP3A regulatory regions remain largely uncharacterized, how DNA methylation influences CYP3A expression has yet to be fully explored. We recently identified a distal regulatory region (DRR) that controls the expression of CYP3A4, CYP3A5, and CYP3A7. Here, we investigated the relationship between CYP3A expression and the methylation status of 16 CpG sites within the DRR in 70 liver samples. We found significant associations between DRR methylation and the expression of CYP3A5 and CYP3A7 but not CYP3A4, indicating differential CYP3A regulation by the DRR. Also, we observed a dynamic reduction in DRR DNA methylation during the differentiation of induced pluripotent stem cells to hepatocytes, which correlated with increased CYP3A expression. We then evaluated the relative contribution of genetic variants, TFs, and DRR DNA methylation on CYP3A expression in liver samples. Our results reinforce the DRR as a CYP3A regulator and suggest that DNA methylation may impact CYP3A-mediated drug metabolism.

CYP3A4-mediated metabolism of artemisinin to 10β-hydroxyartemisinin with comparable anti-malarial potency.

The most widely used anti-malarial drug artemisinin (ART) is metabolized extensively, but the therapeutic capacity of its major metabolite remains unknown. Whether the major metabolite of ART (ART-M) contributes to its antiplasmodial potency was investigated in this study. The metabolite identification and enzyme phenotyping of ART were performed using human liver microsomes (HLMs). The stereostructure of the major metabolite ART-M was elucidated by spectroscopic and X-ray crystallographic analysis. The anti-malarial activity of ART-M against two reference Plasmodium strains (Pf3D7 and PfDd2) was evaluated. The pharmacokinetic profiles of ART and its metabolite ART-M were investigated in healthy Chinese subjects after a recommended two-day oral dose of ART plus piperaquine. Pharmacodynamic parameters based on minimum inhibitory concentration (MIC50) and free plasma concentration were employed to evaluate the therapeutic potency of ART-M, including fAUC0-t/MIC50, fCmax/MIC50 and T > MIC50. A major metabolite 10β-hydroxyartemisinin (ART-M) was found for ART in human, and CYP3A4/3A5 was the major enzymes responsible for ART 10β-hydroxylation. Compared with ART (MIC50, 10.1nM against Pf3D7), weaker antiplasmodial activity was found for ART-M (MIC50, 61.4nM against Pf3D7). However, a 3.5-fold higher maximal free plasma concentration was achieved for ART-M (fCmax, 180.0nM vs. 51.8nM for ART). ART-M displayed comparable antiplasmodial potency to ART, in terms of fAUC0-t/MIC50 (12.5h), fCmax/MIC50 (2.8) and T > MIC50 (5h). The major metabolite 10β-hydroxyartemisinin contributes to the antiplasmodial efficacy of ART, which should be considered when evaluation of ART dosing regimens and/or clinical outcomes.

Ticagrelor and Statins: Dangerous Liaisons?

Polypharmacy is often necessary in complex, chronic, comorbid and cardiovascular patients and is a known risk factor for potential drug-drug interaction (DDI) that can cause adverse reactions (toxicity or therapeutic failure). Anti-thrombotic drugs (largely low-dose aspirin and a platelet P2Y12 receptor inhibitor) and statins are among the most co-administered drugs in cardiovascular patients. Ticagrelor is a selective antagonist of the platelet P2Y12-receptor, highly effective in inhibiting platelet aggregation and bio-transformed by the CYP3A4 and substrate of transporters, such as the breast cancer resistance protein (BCRP). Statins have different pharmacokinetic profiles; some undergo CYP3A4-mediated metabolism; rosuvastatin is primarily metabolized by the CYP2C9; and they have different affinities for drug transporters. Rhabdomyolysis is a very rare but severe adverse event, which is specific for statins which can be triggered by DDIs that increase statin’s concentrations through blockade of their biotransformation and/or elimination. Large pharmacovigilance and small observational studies reported increased rhabdomyolysis in patients treated with some statins and ticagrelor but not aspirin, clopidogrel or prasugrel. Recent studies in vitro, pharmacokinetic trials and in silico drug modelling identified and validated the BCRP inhibition by ticagrelor, as a mechanism contributing to the DDI with statins, as ‘victim’ drugs, leading to increased rhabdomyolysis. While the clinical impact of this DDI deserves further investigation, a careful evaluation should be advised when ticagrelor is co-prescribed with some statins.

Systematic Evaluation of Tyrosine Kinase Inhibitors as OATP1B1 Substrates Using a Competitive Counterflow Screen.

Despite the established exposure-pharmacodynamic relationships for many TKIs, the mechanisms underlying the agents' unpredictable pharmacokinetic profiles remain poorly understood. We report here that the disposition of many TKIs depends on hepatic transport by OATP1B1, a process that has toxicologic ramifications for agents that are associated with hepatotoxicity.

Role of Cytochrome P450 3A4 in Cancer Drug Resistance: Challenges and Opportunities.

One of the biggest obstacles to the treatment of diseases, particularly serious conditions like cancer, is therapeutic resistance. The process of drug resistance is influenced by a number of important variables, including MDR genes, drug efflux, low-quality medications, inadequate dosage, etc. Drug resistance must be addressed, and new combinations based on the pharmacokinetics/pharmacodynamics (PK-PD) characteristics of the partner pharmaceuticals must be developed in order to extend the half-lives of already available medications. The primary mechanism of drug elimination is hepatic biotransformation of medicines by cytochrome P450 (CYP) enzymes; of these CYPs, CYP3A4 makes up 30-40% of all known cytochromes that metabolize medications. Induction or inhibition of CYP3A4-mediated metabolism affects the pharmacokinetics of most anticancer drugs, but these details are not fully understood and highlighted because of the complexity of tumor microenvironments and various influencing patient related factors. The involvement of CYPs, particularly CYP3A4 and other drug-metabolizing enzymes, in cancer medication resistance will be covered in the current review.

Probe Substrate Dependencies in CYP3A4 Allosteric Inhibition: A Novel Molecular Mechanism Involving F-F' Loop Perturbations.

The biochemical basis for substrate dependences in apparent inhibition constant values (Ki) remains unknown. Our study aims to elucidate plausible structural determinants underpinning these observations. In vitro steady-state inhibition assays conducted using human recombinant CYP3A4 enzyme and testosterone substrate revealed that fibroblast growth factor receptor (FGFR) inhibitors erdafitinib and pemigatinib noncompetitively inhibited CYP3A4 with apparent Ki values of 10.2 ± 1.1 and 3.3 ± 0.9 μM, respectively. However, when rivaroxaban was adopted as the probe substrate, there were 2.0- and 3.2-fold decreases in its apparent Ki values. To glean mechanistic insights into this phenomenon, erdafitinib and pemigatinib were docked to allosteric sites in CYP3A4. Subsequently, molecular dynamics (MD) simulations of apo- and holo-CYP3A4 were conducted to investigate the structural changes induced. Comparative structural analyses of representative MD frames extracted by hierarchical clustering revealed that the allosteric inhibition of CYP3A4 by erdafitinib and pemigatinib did not substantially modulate its active site characteristics. In contrast, we discovered that allosteric binding of the FGFR inhibitors reduces the structural flexibility of the F-F' loop region, an important gating mechanism to regulate access of the substrate to the catalytic heme. We surmised that the increased rigidity of the F-F' loop engenders a more constrained entrance to the CYP3A4 active site, which in turn impedes access to the larger rivaroxaban molecule to a greater extent than testosterone and culminates in more potent inhibition of its CYP3A4-mediated metabolism. Our findings suggest a potential mechanism to rationalize probe substrate dependencies in Ki arising from the allosteric noncompetitive inhibition of CYP3A4.

Assessing the relative contribution of CYP3A-and P-gp-mediated pathways to the overall disposition and drug-drug interaction of dabigatran etexilate using a comprehensive mechanistic physiological-based pharmacokinetic model.

Dabigatran etexilate (DABE) is a clinical probe substrate for studying drug-drug interaction (DDI) through an intestinal P-glycoprotein (P-gp). A recent in vitro study, however, has suggested a potentially significant involvement of CYP3A-mediated oxidative metabolism of DABE and its intermediate monoester BIBR0951 in DDI following microdose administration of DABE. In this study, the relative significance of CYP3A- and P-gp-mediated pathways to the overall disposition of DABE has been explored using mechanistic physiologically based pharmacokinetic (PBPK) modeling approach. The developed PBPK model linked DABE with its 2 intermediate (BIBR0951 and BIBR1087) and active (dabigatran, DAB) metabolites, and with all relevant drug-specific properties known to date included. The model was successfully qualified against several datasets of DABE single/multiple dose pharmacokinetics and DDIs with CYP3A/P-gp inhibitors. Simulations using the qualified model supported that the intestinal CYP3A-mediated oxidation of BIBR0951, and not the gut P-gp-mediated efflux of DABE, was a key contributing factor to an observed difference in the DDI magnitude following the micro-versus therapeutic doses of DABE with clarithromycin. Both the saturable CYP3A-mediated metabolism of BIBR0951 and the solubility-limited DABE absorption contributed to the relatively modest nonlinearity in DAB exposure observed with increasing doses of DABE. Furthermore, the results suggested a limited role of the gut P-gp, but an appreciable, albeit small, contribution of gut CYP3A in mediating the DDIs following the therapeutic dose of DABE with dual CYP3A/P-gp inhibitors. Thus, a possibility exists for a varying extent of CYP3A involvement when using DABE as a clinical probe in the DDI assessment, across DABE dose levels.

In vitro demonstration of antedrug mechanism of a pharmacokinetic booster to improve CYP3A4 substrates by CYP3A4-mediated metabolism inhibition

In vitro demonstration of antedrug mechanism of a pharmacokinetic booster to improve CYP3A4 substrates by CYP3A4-mediated metabolism inhibition

Interplay of Ritonavir-Boosted Oral Cabazitaxel with the Organic Anion-Transporting Polypeptide (OATP) Uptake Transporters and Carboxylesterase 1 in Mice.

Intravenously administered chemotherapeutic cabazitaxel is used for palliative treatment of prostate cancer. An oral formulation would be more patient-friendly and reduce the need for hospitalization. We therefore study determinants of the oral pharmacokinetics of cabazitaxel in a ritonavir-boosted setting, which reduces the CYP3A-mediated first-pass metabolism of cabazitaxel. We here assessed the role of organic anion-transporting polypeptides (OATPs) in the disposition of orally boosted cabazitaxel and its active metabolites, using the Oatp1a/b-knockout and the OATP1B1/1B3-transgenic mice. These transporters may substantially affect plasma clearance and hepatic and intestinal drug disposition. The pharmacokinetics of cabazitaxel and DM2 were not significantly affected by Oatp1a/b and OATP1B1/1B3 activity. In contrast, the plasma AUC0-120min of DM1 in Oatp1a/b-/- was 1.9-fold (p < 0.05) higher than that in wild-type mice, and that of docetaxel was 2.4-fold (p < 0.05) higher. We further observed impaired hepatic uptake and intestinal disposition for DM1 and docetaxel in the Oatp-ablated strains. None of these parameters showed rescue by the OATP1B1 or -1B3 transporters in the humanized mouse strains, suggesting a minimal role of OATP1B1/1B3. Ritonavir itself was also a potent substrate for mOatp1a/b, showing a 2.9-fold (p < 0.0001) increased plasma AUC0-120min and 3.5-fold (p < 0.0001) decreased liver-to-plasma ratio in Oatp1a/b-/- compared to those in wild-type mice. Furthermore, we observed the tight binding of cabazitaxel and its active metabolites, including docetaxel, to plasma carboxylesterase (Ces1c) in mice, which may complicate the interpretation of pharmacokinetic and pharmacodynamic mouse studies. Collectively, these results will help to further optimize (pre)clinical research into the safety and efficacy of orally applied cabazitaxel.