Cytochrome P450 3A4 Substrate Research Articles

Hepatic drug metabolism in older people with body composition changes.

Dosage adjustment is essential in older individuals because they are prone to experience a decline in liver function and changes in body composition. However, quantitative tests or equations for evaluating the activity of hepatic drug metabolism have not yet been clearly established. We examined hepatic drug metabolism activities in older individuals, focusing on changes in body composition parameters. Lansoprazole and nifedipine, substrates of the metabolic enzymes cytochrome P450 (CYP) 2C19 and 3A4, respectively, were selected to study hepatic drug metabolism. Residual samples from blood test for older patients were evaluated to determine drug metabolism. The body composition of relevant patients was determined by analyzing characteristic parameters of skeletal muscle mass index (SMI), handgrip strength (HGS) and hepatic steatosis index (HSI). The differences in hepatic drug metabolism were studied statistically among categories in terms of the cut-off value of these parameters. Older male patients receiving lansoprazole and nifedipine in the low SMI (<7.0 kg/m2 ) category showed an 85-90% reduction in respective CYP2C19 and CYP3A4 metabolic activities compared with the normal SMI category. For the female patients, CYP2C19 and CYP3A4 metabolic activities showed no significant correlation with SMI and HGS. Fatty liver disease (HSI ≥36) was found to reduce CYP2C19 metabolic activity particularly in older female patients. Low CYP2C19 metabolic activity was statistically correlated with low SMI in male patients and high HSI in female patients, whereas low CYP3A4 metabolic activity was statistically correlated with low HGS in male patients. Geriatr Gerontol Int 2022; 22: 449-454.

Combined Use of Calcium-channel Blockers With Ombitasvir/Paritaprevir/Ritonavir Exacerbates Peripheral Edema in Elderly Japanese Patients

The antiviral agent ritonavir is a substrate for cytochrome P450 3A4 (CYP3A4); therefore, concomitant use of CYP3A4-metabolising drugs might cause adverse reactions to this drug. We investigated the plasma level of calcium channel blockers (CCBs) as CYP3A4 substrates and peripheral edema as a potential adverse drug reaction possibly caused by the anti-hepatitis C virus (HCV) regimen of ombitasvir/paritaprevir/ritonavir (OPR) and CCBs. We enrolled Japanese patients prescribed OPR for HCV infection. Peripheral edema was graded according to the Common Terminology Criteria for Adverse Events ver. 4. Plasma samples were collected on days 0, 7, 14, 28, and 42 after antiviral treatment, at the trough level. Out of 52 patients, 64% experienced grade 1 or grade 2 peripheral edema, but not grade 3. Concomitant use of CCBs significantly increased the emergence of grade 2 edema (62%), compared with patients treated solely with OPR (48%). The use of OPR significantly increased the plasma concentration of amlodipine. Peripheral edema in patients treated with OPR and CCBs, although tolerable, should be closely monitored.

Direct and Sequential Bioactivation of Pemigatinib to Reactive Iminium Ion Intermediates Culminates in Mechanism-Based Inactivation of Cytochrome P450 3A.

We recently established the mechanism-based inactivation (MBI) of cytochrome P450 3A (CYP3A) by the fibroblast growth factor receptor (FGFR) inhibitors erdafitinib and infigratinib. Serendipitously, our preliminary data have also revealed that pemigatinib (PEM), another clinically approved FGFR1-3 inhibitor, similarly elicited time-dependent inhibition of CYP3A. This was rather unexpected, as it was previously purported that PEM did not pose any metabolism-dependent liabilities due to the absence of glutathione-related conjugates in metabolic profiling experiments conducted in human liver microsomes. Here, we confirmed that PEM inhibited both CYP3A isoforms in a time-, concentration-, and cofactor-dependent manner consistent with MBI, with inactivator concentration at half-maximum rate constant, maximum inactivation rate constant, and partition ratio of 8.69 and 11.95 μM, 0.108 and 0.042 min-1, and approximately 44 and approximately 47 for CYP3A4 and CYP3A5, respectively. Although the rate of inactivation was diminished by coincubation with an alternative substrate or direct inhibitor of CYP3A, the inclusion of nucleophilic trapping agents afforded no such protection. Furthermore, the lack of catalytic activity recovery following dialysis and oxidation with potassium ferricyanide coupled with the absence of a spectrally resolvable peak in the Soret region collectively implied that the underlying mechanism of inactivation was not elicited via the formation of pseudo-irreversible metabolite-intermediate complexes. Finally, utilizing cyanide trapping and high-resolution mass spectrometry, we illuminated the direct and sequential oxidative bioactivation of PEM and its major O-desmethylated metabolite at its distal morpholine moiety to reactive iminium ion hard electrophilic species that could covalently inactivate CYP3A via MBI. SIGNIFICANCE STATEMENT: This study reports for the first time the covalent MBI of CYP3A by PEM and deciphered its bioactivation pathway involving the metabolic activation of PEM and its major O-desmethylated metabolite to reactive iminium ion intermediates. Following which, a unique covalent docking methodology was harnessed to unravel the structural and molecular determinants underpinning its inactivation. Findings from this study lay the foundation for future investigation of clinically relevant drug-drug interactions between PEM and concomitant substrates of CYP3A.

Evaluation of hepatic CYP3A enzyme activity using endogenous markers in lung cancer patients treated with cisplatin, dexamethasone, and aprepitant.

Aprepitant is used with dexamethasone and 5-HT3 receptor antagonists as an antiemetic treatment for chemotherapy, including cisplatin. Aprepitant is a substrate of cytochrome P450 (CYP) 3A4 and is known to cause its inhibition and induction. In addition, dexamethasone is a CYP3A4 substrate that induces CYP3A4 and CYP3A5 expression. In this study, we aimed to quantitatively evaluate the profile of CYP3A activity using its endogenous markers in non-small cell lung cancer patients receiving a standard cisplatin regimen with antiemetics, including aprepitant. Urinary 11β-hydroxytestosterone (11β-OHT)/testosterone concentration ratio and plasma 4β-hydroxycholesterol (4β-OHC) concentrations were measured before and after cisplatin treatment (days 1, 4, and 8). CYP3A5 was genotyped, and plasma aprepitant concentrations were measured on day 4 to examine its influence on CYP3A endogenous markers. The urinary 11β-OHT/testosterone concentration ratio in the 35 patients included in this study increased by 2.65-fold and 1.21-fold on days 4 and 8 compared with day 1, respectively. Their plasma 4β-OHC concentration increased by 1.46-fold and 1.66-fold, respectively. The mean plasma aprepitant concentration on day 4 was 1,451ng/mL, which is far lower than its inhibitory constant. The allele frequencies of CYP3A5*1 and CYP3A5*3 were 0.229 and 0.771, respectively. In patients with the CYP3A5*1 allele, the plasma 4β-OHC concentration was significantly lower at baseline but more potently increased with chemotherapy. CYP3A activity was significantly induced from day 4 to day 8 in patients receiving cisplatin and three antiemetic drugs.

Pharmacokinetic and Safety Profile of the Novel HIV Nonnucleoside Reverse Transcriptase Inhibitor MK-8507 in Adults without HIV.

ABSTRACTMK-8507 is a novel HIV-1 nonnucleoside reverse transcriptase inhibitor in clinical development with potential for once-weekly oral administration for the treatment of HIV-1 infection. Two randomized, double-blind, placebo-controlled phase 1 studies in adults without HIV-1 evaluated the safety, tolerability, and pharmacokinetics of single and multiple doses of MK-8507; drug interaction with midazolam (a cytochrome P450 3A4 substrate) and food effect were also assessed. In study 1, 16 participants received oral ascending single doses of MK-8507 (2 to 400 mg) or placebo in an alternating fashion. In study 2, 24 participants received ascending single doses of MK-8507 (400 to 1,200 mg) or placebo and multiple doses (once weekly for 3 weeks) of MK-8507 (100 to 400 mg) or placebo. MK-8507 pharmacokinetics were approximately dose proportional at 2 to 1,200 mg. MK-8507 had a time to maximum concentration of 2 to 7 h and a mean terminal half-life of ∼58 to 84 h. MK-8507 doses of ≥100 mg achieved a plasma concentration at 168 h postdose (7 days) associated with antiviral efficacy. A high-fat meal had no clinically meaningful effect on MK-8507 pharmacokinetics, and MK-8507 400 mg once weekly had no clinically meaningful effect on midazolam pharmacokinetics. Single and multiple doses of MK-8507 were generally well tolerated. No trends with dose and no clinically meaningful changes were observed in vital signs, electrocardiograms, and laboratory safety tests. The pharmacokinetics and safety data are supportive of once-weekly oral administration and support further clinical investigation of MK-8507 for the treatment of HIV-1 infection.

Abstract CT125: Evaluation of potential drug-drug interactions (DDIs) between futibatinib and CYP3A inhibitors/inducers, CYP3A substrates, or proton pump inhibitors (PPIs)

Abstract Background Futibatinib is an oral, irreversible FGFR1-4 inhibitor with clinical activity in cholangiocarcinoma and other FGFR-aberrant tumors. The recommended futibatinib dosage is 20 mg once daily (QD). In vitro studies have shown that futibatinib is predominantly metabolized by and inhibits cytochrome p450 3A (CYP3A); futibatinib is also a P-glycoprotein substrate. Two phase 1 studies were performed in healthy volunteers to evaluate potential DDIs between futibatinib and CYP3A substrates (midazolam; study 1) or CYP3A inhibitors/inducers (itraconazole/rifampin; study 2). As the solubility of futibatinib is pH dependent, study 3 assessed the effect of PPI (lansoprazole) coadministration on futibatinib pharmacokinetics (PK). Methods All 3 studies, conducted in adult nonsmokers, were open-label, fixed-sequence, 2-period cross-over studies with a 1- or 2-d washout between each period. In study 1, midazolam 2 mg was given on d1 of period 1 (-futibatinib) and on d7 of period 2 (+futibatinib 20 mg QD d1-7). In study 2, futibatinib 20 mg was given on d1 of period 1 (alone) and on d5 (+itraconazole 200 mg QD d1-6) or d8 (+rifampin 600 mg QD d1-9) of period 2. In study 3, futibatinib 20 mg was given on d1 of period 1 (-lansoprazole) and d5 of period 2 (+lansoprazole 60 mg QD d1-5). Plasma samples for PK assessment were collected predose through 24 h post-midazolam dosing (study 1) and predose through 48 h post-futibatinib dosing (studies 2 and 3). Results In study 1 (N=24), coadministration of futibatinib did not result in clinically significant changes in midazolam PK, based on the area under the concentration curve extrapolated to the last measurable time (AUC0-t; -9%) or infinity (AUC0-inf; -9%) or maximum plasma concentration (Cmax; -5%), compared with midazolam alone. In study 2 (N=40), relative to futibatinib administered alone, coadministration with itraconazole increased futibatinib Cmax (+51%) and plasma exposure (AUC0-t and AUC0-inf +41% each), whereas coadministration with rifampin decreased futibatinib Cmax (-53%) and plasma exposure (AUC0-t and AUC0-inf -64% each). In study 3 (N=20), coadministration of lansoprazole did not result in clinically significant changes in futibatinib PK parameters vs futibatinib alone (AUC0-t +5%; AUC0-inf +5%; Cmax +8%). Agents were well tolerated, and all 3 studies were completed with no clinically relevant safety signals. Conclusions Futibatinib is not expected to affect the exposure of concomitant medications metabolized via CYP3A, the most common drug metabolism pathway. Caution should be exercised when coadministering strong CYP3A inducers or inhibitors with futibatinib, as significant DDIs were observed with itraconazole and rifampin. Futibatinib can be concomitantly administered with PPIs with no clinically relevant impact on futibatinib exposure. Citation Format: Ikuo Yamamiya, John Laabs, Allen Hunt, Toru Takenaka, Daryl Sonnichsen, Mark Mina, Yaohua He, Karim Benhadji. Evaluation of potential drug-drug interactions (DDIs) between futibatinib and CYP3A inhibitors/inducers, CYP3A substrates, or proton pump inhibitors (PPIs) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr CT125.

Effect of naringenin on the pharmacokinetics of metoprolol succinate in rats

The aim of the present study was to investigate the effect of naringenin (4,5,7-trihydroxy flavonone) on the pharmacokinetics of metoprolol, a substrate of Cytochrome P-450 3A4 (CYP3A4), CYP2C9, and CYP2D6 in rats. Male Wistar rats were treated orally with metoprolol (30 mg/kg) alone and in combination with naringenin (25, 50, and 100 mg/kg) once daily for 15 consecutive days. The plasma concentrations of metoprolol were determined using Reverse Phase-High Performance Liquid Chromatography (RP-HPLC) on the 1st day in single-dose pharmacokinetic (PK) study (SDS) and on the 15th day in multiple dosing PK studies (MDS). Compared to the metoprolol control group, the C max, AUC, and half-life (T 1/2) of metoprolol increased in rats pre-treated with naringenin, while there was no significant change in T max. There is a significant decrease in clearance and volume of distribution. The present study results revealed that naringenin significantly enhanced the C max, AUC, MRT, t 1/2, and decreased the clearance of metoprolol possibly through the inhibition of CYP enzymes involved in the metabolism of metoprolol.

CYP3A4⁎22 gene polymorphism and risk of ischemic stroke in south Iran population: A case control study

Cytochrome P450 3A4 (CYP3A4), the main drug-metabolizing enzyme in the liver, has a functional SNP in intron six named CYP3A4⁎22. Given the CYP3A4⁎22 polymorphism effect on the reduced CYP3A4 mRNA/protein expression, this study aimed to evaluate the prevalence of CYP3A4⁎22 polymorphism in Iranian patients with stroke compared to the control group. A total of 175 patients with stroke and 236 control age-sex matched ones have been examined for CYP3A4⁎22 polymorphism by Tetra ARMS-PCR methods. The results were confirmed by the PCR-RFLP technique and the sequencing of DNA. This study is the first report of CYP3A4⁎22 polymorphism from Iran. The frequency of the CYP3A4⁎22 wild-type (GG genotype) and heterozygous genotypes (GA genotype) was 93.1% and 6.9% in patients, and 92.8% and 7.2% in the controls, respectively. None of the participants was the recessive model for this polymorphism. There were no statistical differences between the patient and control groups (p > 0.05). Also, the GA genotype was not associated with increased risk of stroke compared with the GG genotype (OR = 0.95, 95% CI: 0.44–2.04, P = 0.892). Since CYP3A4⁎22 polymorphism may result in reduced CYP3A4 activity in vivo, due to the large number of drugs that are CYP3A4 substrates, individuals with this polymorphism may experience unusual drug effects. To clarify these impacts, further investigations are, therefore, needed to be done.

In vivo evaluation of intestinal human CYP3A inhibition by macrolide antibiotics in CYP3A-humanised mice

It is important to predict drug-drug interactions via inhibition of intestinal cytochrome P450 3A (CYP3A) which is a determinant of bioavailability of orally administered CYP3A substrates. However, inhibitory effects of macrolide antibiotics on CYP3A-mediated metabolism are not entirely identical between humans and rodents. We investigated the effects of macrolide antibiotics, clarithromycin and erythromycin, on in vitro and in vivo metabolism of triazolam, a CYP3A substrate, in CYP3A-humanised mice generated by using a mouse artificial chromosome vector carrying a human CYP3A gene. Metabolic activities of triazolam were inhibited by macrolide antibiotics in liver and intestine microsomes of CYP3A-humanised mice. The area under the plasma concentration-time curve ratios of 4-hydroxytriazolam to triazolam after oral dosing of triazolam were significantly decreased by multiple administration of macrolide antibiotics. The plasma concentrations ratios of α-hydroxytriazolam and 4-hydroxytriazolam to triazolam in portal blood were significantly decreased by multiple administration of clarithromycin in CYP3A-humanised mice. These results suggest that intestinal CYP3A activity was inhibited by macrolide antibiotics in CYP3A-humanised mice in vitro and in vivo. The plasma concentrations of triazolam and its metabolites in the portal blood of CYP3A-humanised mice would be useful for direct evaluation of intestinal CYP3A-mediated drug-drug interactions.

Pharmacokinetics of the CYP3A4 and CYP2B6 Inducer Carbamazepine and Its Drug-Drug Interaction Potential: A Physiologically Based Pharmacokinetic Modeling Approach.

The anticonvulsant carbamazepine is frequently used in the long-term therapy of epilepsy and is a known substrate and inducer of cytochrome P450 (CYP) 3A4 and CYP2B6. Carbamazepine induces the metabolism of various drugs (including its own); on the other hand, its metabolism can be affected by various CYP inhibitors and inducers. The aim of this work was to develop a physiologically based pharmacokinetic (PBPK) parent−metabolite model of carbamazepine and its metabolite carbamazepine-10,11-epoxide, including carbamazepine autoinduction, to be applied for drug–drug interaction (DDI) prediction. The model was developed in PK-Sim, using a total of 92 plasma concentration−time profiles (dosing range 50–800 mg), as well as fractions excreted unchanged in urine measurements. The carbamazepine model applies metabolism by CYP3A4 and CYP2C8 to produce carbamazepine-10,11-epoxide, metabolism by CYP2B6 and UDP-glucuronosyltransferase (UGT) 2B7 and glomerular filtration. The carbamazepine-10,11-epoxide model applies metabolism by epoxide hydroxylase 1 (EPHX1) and glomerular filtration. Good DDI performance was demonstrated by the prediction of carbamazepine DDIs with alprazolam, bupropion, erythromycin, efavirenz and simvastatin, where 14/15 DDI AUClast ratios and 11/15 DDI Cmax ratios were within the prediction success limits proposed by Guest et al. The thoroughly evaluated model will be freely available in the Open Systems Pharmacology model repository.

Drug–Drug Interactions of the Nonsteroidal Mineralocorticoid Receptor Antagonist Apararenone With Midazolam, Warfarin, and Digoxin: A Phase 1 Studies in Healthy Volunteers

PurposeTo characterize the clinical relevance of in vitro drug–drug interaction findings with apararenone (MT-3995), the effects of apararenone on the sensitive substrates of cytochrome P450 3A4 (midazolam) and 2C9 (warfarin), and P-glycoprotein (digoxin), were assessed through a series of studies conducted in healthy volunteers. MethodsThree studies were conducted in 56 healthy adults. Study 1 investigated the effects of the administration of apararenone with midazolam; apararenone was administered on days 2 (320 mg) and days 3–15 (20 mg/d), and midazolam 2 mg, on days 1 and 15. Study 2 investigated the effects of the administration of apararenone with warfarin; apararenone was administered on days 8–11 (40 mg/d) and days 12–27 (10 mg/d), and warfarin 25 mg, on days 1 and 21. Study 3 assessed the effects of the administration of apararenone with digoxin; apararenone was administered on days 11 (160 mg) and days 12–28 (10 mg/d), and digoxin 0.5 mg, on days 1 and 24. Pharmacokinetic parameters included Cmax, AUC0–t, and AUC0–∞. The safety profile was evaluated based on adverse events from spontaneous reports and clinical findings. FindingsAfter the administration of midazolam together with apararenone, compared with midazolam alone, the midazolam ± apararenone treatment ratios (90% CIs) of the geometric least squares (LS) mean Cmax, AUC0–t, and AUC0–∞ values were 1.263 (1.147–1.392), 1.342 (1.220–1.477), and 1.370 (1.225–1.534), respectively. After the administration of warfarin ± apararenone, the R-warfarin ± apararenone treatment ratios (90% CIs) of the geometric LS mean Cmax, AUC0–t, and AUC0–∞ values were 1.008 (0.934–1.089), 1.078 (1.029–1.129), and 1.110 (1.056–1.166). Corresponding values for S-warfarin were 1.025 (0.941–1.117), 1.024 (0.979–1.071), and 1.031 (0.984–1.080). After the administration of digoxin ± apararenone, the digoxin ± apararenone treatment ratios (90% CIs) of the geometric LS mean Cmax, AUC0–t, and AUC0–∞ values were 0.929 (0.789–1.093), 0.894 (0.797–1.033), and 0.887 (0.805–0.977), respectively. Treatment-emergent adverse events were generally of mild to moderate intensity, and no serious adverse events of any kind were reported. ImplicationsThe findings from this analysis of data from healthy volunteers suggest minimal risk for potential drug–drug interactions between apararenone and other drugs that are likely to be used concurrently in patients. ClinicalTrials.gov identifier: NCT02531568.

Characterization of the Human Intestinal Drug Transport with Ussing Chamber System Incorporating Freshly Isolated Human Jejunum

Intestinal permeability is a critical factor for orally administered drugs. It can be facilitated by uptake transporters or limited by efflux transporters and metabolic enzymes in the intestine. The present study aimed to characterize the Ussing chamber system incorporating human intestinal tissue as an in vitro model for investigating the impact of intestinal uptake/efflux transporters on the intestinal absorption of substrate drugs in humans. We confirmed the functions of major intestinal uptake/efflux drug transporters in freshly isolated human jejunum sections by demonstrating a significant decrease in the mucosal uptake of cefadroxil (peptide transporter 1) and methotrexate (proton-coupled folate transporter), mucosal-to-serosal permeability of ribavirin (concentrative nucleoside transporters/equilibrative nucleoside transporters), and serosal-to-mucosal permeability of P-glycoprotein and breast cancer resistance protein substrates in the presence of their typical inhibitors. The mucosal-to-serosal apparent permeability coefficients (Papp) of 19 drugs, including substrates of drug transporters and cytochrome P450 3A, ranged from 0.60 × 10-6 to 29 × 10-6 cm/s and showed a good correlation with reported fraction of an oral dose that enters the gut wall and passes into the portal circulation with escaping intestinal metabolism (FaFg) values in humans. Furthermore, the Papp values for cefadroxil, methotrexate, and ribavirin in the presence of the corresponding transporter inhibitors underestimated the FaFg of these drugs, which clearly showed that intestinal uptake transporters facilitate their intestinal absorption in humans. In conclusion, the functions of major intestinal uptake/efflux drug transporters could be maintained in freshly isolated human jejunum sections. The Ussing chamber system incorporating human intestinal tissue would be useful for evaluating the impact of intestinal uptake/efflux transporters on the intestinal absorption of various types of drugs in humans. SIGNIFICANCE STATEMENT: Although previous studies have predicted the intestinal absorption of drugs in humans using the Ussing chamber system incorporating human intestinal tissue, there is little systematic information about drug transport mediated by multiple transporters in this system. We confirmed the functions of major intestinal uptake/efflux transporters in freshly isolated human jejunum sections and demonstrated that the mucosal-to-serosal apparent permeability coefficient of various types of drugs showed a good correlation with reported human FaFg values.

Drug interactions between emergency contraceptive drugs and cytochrome inducers: literature review and quantitative prediction.

The emergency contraceptive drugs (EC), levonorgestrel (LNG) and ulipristal acetate (UPA), are sensitive substrates of cytochrome P450 3A4 (CYP3A4). In 2016, the label of LNG was updated based on a drug-drug interaction (DDI) study showing a significant decrease in LNG exposure when co-administered with efavirenz, a known CYP3A4 inducer. DDI between UPA and CYP3A4 inducers are poorly characterized. The aims of this study were to review quantitative data from the literature on DDI with EC, to provide quantitative predictions of DDI between UPA and CYP3A4 inducers, and to identify moderate and severe DDI that may require a dose adjustment. A literature search was performed on pharmacokinetic DDI of LNG and UPA. Quantitative prediction of DDI with UPA was carried out by using the in vivo mechanistic static model (IMSM). Limited information was available on DDI with emergency contraception drugs. For LNG, data from eleven studies were retrieved, including five known CYP3A4 inducers that confirmed a risk of underexposure to LNG when co-administered with inducers. For UPA, only three studies were identified, including only one CYP3A4 inducer. The IMSM approach indicated that UPA is a sensitive substrate of CYP3A4, with an estimated contribution of 86% of CYP3A4 to oral clearance. Moderate to severe DDI were predicted in 17 cases with CYP3A4 inducers, and dosage adjustments were suggested. This study illustrates the ability of the IMSM approach to inform about the DDI profile of old and new drugs.

An Adaptive Physiologically Based Pharmacokinetic-Driven Design to Investigate the Effect of Itraconazole and Rifampicin on the Pharmacokinetics of Molibresib (GSK525762) in Healthy Female Volunteers.

Molibresib (GSK525762), an orally bioavailable small molecule with 2 major equipotent active metabolites, is being developed for the treatment of cancers. Molibresib is a substrate of cytochrome P450 (CYP) 3A4 and P‐glycoprotein (P‐gp). To enable administering safe doses of molibresib to healthy volunteers, this 2‐part randomized, open‐label, crossover drug‐drug interaction trial was conducted as an adaptive design study using physiologically based pharmacokinetic (PBPK) modeling and simulation to predict the lowest doses of molibresib that could be safely administered alone (10 mg) or with itraconazole and rifampicin (strong inhibitors and inducers of CYP3A and P‐gp, respectively). PBPK simulation guided the molibresib dose (5 mg) to be administered along with itraconazole in part 1. Itraconazole increased total exposure (AUC) of molibresib by 4.15‐fold with a 66% increase in Cmax, whereas the total AUC and Cmax for the 2 major active metabolites of molibresib decreased by about 70% and 87%, respectively. A second PBPK simulation was conducted with part 1 data to also include the active metabolites to update the recommendation for the molibresib dose (20 mg) with rifampicin. With rifampicin, the AUC and Cmax of molibresib decreased by approximately 91% and 80%, respectively, whereas the AUC of the 2 active metabolites decreased to a lesser extent (8%), with a 2‐fold increase in Cmax. The results of this study confirmed the in vitro data that molibresib is a substrate for CYP3A4. The adaptive design, including Simcyp simulations, allowed evaluation of 2 drug interactions of an oncology drug in a single trial, thus minimizing time and exposures administered to healthy subjects.

Drug-Drug Interactions between Direct Oral Anticoagulants and Hepatitis C Direct-Acting Antiviral Agents: Looking for Evidence Through a Systematic Review.

BackgroundDirect oral anticoagulants (DOACs), as substrates of cytochrome P450 (CYP) 3A4 and/or P-glycoprotein, are susceptible to drug–drug interactions (DDIs). Hepatitis C direct-acting antiviral agents (DAAs), via P-glycoprotein or CYP3A4 inhibition, may increase DOAC exposure with relevant bleeding risk. We performed a systematic review on DDIs between DOACs and DAAs.MethodsTwo reviewers independently identified studies through electronic databases, until 7 July 2020, supplementing the search by reviewing conference abstracts and the ClinicalTrials.gov website.ResultsOf 1386 identified references, four articles were finally included after applying the exclusion criteria. Three phase I clinical studies in healthy volunteers assessed interactions between dabigatran and glecaprevir/pibrentasvir, odalasvir/simeprevir, or sofosbuvir/velpatasvir/voxilaprevir, showing an increase in the dabigatran area under the concentration–time curve (AUC) by 138%, 103%, and 161%, respectively.ConclusionsDOACs and DAAs are under-investigated for DDI risk. Real-world studies are needed to assess the clinical relevance of the pharmacokinetic interactions with dabigatran and describe the actual spectrum of possible DDIs between DAAs and other DOACs.

Central serous chorioretinopathy induced by drugs metabolized by cytochrome P450 3A4.

The purpose of this study was investigate whether replacing or discontinuing drugs that are inhibitors or substrates of cytochrome P450 3A4 (CYP3A4) may improve the clinical course of central serous chorioretinopathy (CSC). A retrospective observational study included 43 patients with active CSC. Twenty seven patients (32 eyes, group 1) were using drugs that act as substrates or inhibitors of CYP3A4. In 25 of these 27 patients, treatments including steroids, calcium channel blockers, anticoagulants, statins, beta-adrenolytics, angiotensin receptor antagonists, antidepressants, muscarinic receptor antagonists, phosphodiesterase type 5 inhibitors, and others were discontinued or replaced with medications not affecting CYP3A4. Sixteen patients (19 eyes, group 2) not using any medication that affects CYP3A4, were given eplerenone, rifampicin, or laser treatment. Main outcomes measures were assessed by functional and anatomical images obtained using multimodal imaging techniques. The average follow-up time was 12 months. In group I after discontinuing or replacing substrates or inhibitors of CYP3A4, improvements were observed in 18 patients (22 eyes). None of the patients that were using drugs affecting CYP3A4 improved with eplerenone therapy, however, all 18 patients improved after discontinuing the drugs. All these drugs had a blocking effect on eplerenone therapy. Best corrected visual acuity (BCVA) improved in 14 eyes, remained unchanged in 5 eyes, and worsened in 3 eyes. In 21 of the 22 eyes, subretinal fluid absorption was observed with optical coherence tomography (OCT). Mean central retinal thickness decreased from 361 μm to 219 μm. One patient (2 eyes) was unable to change treatment (due to neoplasm), one patient (1 eye) did not agree to change or stop treatment, and seven patients (7 eyes) were lost to follow-up. Of the 16 patients (19 eyes) who were treated with eplerenone, rifampicin, or laser, improvements were observed in 14 patients (16 eyes), two patients (2 eyes) were lost to follow-up, and CSC worsened in 1 eye. We concluded that patients with CSC should not take substrates or inhibitors of CYP3A4. These drugs should be replaced with alternatives that act through other metabolic pathways.

Physiologically Based Pharmacokinetic Modeling of CFTR Modulation in People with Cystic Fibrosis Transitioning from Mono or Dual Regimens to Triple-Combination Elexacaftor/Tezacaftor/Ivacaftor.

IntroductionThe triple-combination (TC) cystic fibrosis transmembrane conductance regulator (CFTR) modulator regimen elexacaftor, tezacaftor, and ivacaftor was shown to be safe and efficacious in phase 3 trials of people with cystic fibrosis (pwCF) ≥ 12 years of age with ≥ 1 F508del-CFTR allele. Here, a simulation study predicted ivacaftor, tezacaftor, and elexacaftor exposures and impacts on CFTR modulation following transition from ivacaftor [a cytochrome P450 3A (CYP3A) substrate], lumacaftor (a CYP3A inducer)/ivacaftor, or tezacaftor/ivacaftor to TC.MethodsPhysiologically based pharmacokinetic (PBPK) modeling was used to evaluate plasma exposures during transition from mono- or dual-combination CFTR modulator regimens to TC. PBPK models were parameterized using data from human hepatocytes to account for CYP3A induction by lumacaftor and validated to match clinical data from healthy volunteers and pwCF. Using dosing regimens for pwCF ≥ 12 years of age, simulations were performed for ivacaftor, lumacaftor/ivacaftor, and tezacaftor/ivacaftor dosing for 14 days followed by immediate transition to elexacaftor/tezacaftor/ivacaftor dosing for 14 days. Drug exposures during transitions were compared with respective half-maximal effective concentrations (EC50) estimated from efficacy endpoint data from clinical studies.ResultsIn simulations of immediate transition from ivacaftor or tezacaftor/ivacaftor to TC, the preceding treatment had no impact on ivacaftor, tezacaftor, or elexacaftor exposures. In simulations of immediate transition from lumacaftor/ivacaftor to TC, ivacaftor exposure decreased to 64% of maximum effective concentration (EC), due to reduction in ivacaftor dose and residual CYP3A4 induction, then returned to 90–95% of maximum EC. Lumacaftor-mediated CYP3A induction resolved within approximately 2 weeks. In all simulations, ivacaftor, tezacaftor, and elexacaftor exposures approached steady state within 2 weeks following transition and, at all times, ivacaftor and ≥ 1 CFTR corrector remained above EC50.ConclusionPBPK modeling indicates that immediate transition to the elexacaftor/tezacaftor/ivacaftor regimen from an ivacaftor, lumacaftor/ivacaftor, or tezacaftor/ivacaftor regimen results in sustained CFTR modulation in pwCF ≥ 12 years of age.Electronic supplementary materialThe online version of this article (10.1007/s41030-020-00124-7) contains supplementary material, which is available to authorized users.

Evaluation of the Effects of Maytenus ilicifolia on the Activities of Cytochrome P450 3A and P-glycoprotein

Maytenus ilicifolia is a Brazilian popular medicine commonly used to treat ulcer and gastritis. Despite the absence of toxicity regarding its consumption, possible interactions when co-administrated with conventional drugs, are unknown. This study aimed to evaluate the effects of M. ilicifolia extracts on Cytochrome P450 3A (CYP3A) and P-glycoprotein (P-gp) activities. The extracts were obtained by infusion (MI) or turbo-extraction using hydro-acetonic solvent (MT70). The content of polyphenols in each extract was determined. To assess the modulation of M. ilicifolia on P-gp activity, the uptake of fexofenadine (FEX) by Caco-2 cells was investigated in the absence or presence of MI or MT70. The effect on CYP3A activity was evaluated by the co-administration of midazolam (MDZ) with each extract in male Wistar rats. The pharmacokinetic parameters of the drug were determined and compared with those from the control group. The content of total phenolic compounds, tannins, and flavonoids on MT70 extract was about double of that found in MI. In the presence of the extracts, the uptake of the P-gp marker (FEX) by Caco-2 cells increased from 1.7 ± 0.4 ng.mg-1 protein (control) to 3.5 ± 0.2 ng.mg-1 protein (MI) and 4.4 ± 0.5 ng.mg-1 protein (MT70), respectively. When orally co-administrated with MDZ (substrate of CYP3A), the extracts augmented the AUC(0-∞) (Control: 911.7 ± 215.7 ng.h.mL-1; MI: 1947 ± 554.3 ng.h.mL-1; MT70: 2219.0 ± 506.3 ng.h.mL-1) and the Cmax (Control: 407.7 ± 90.4 ng.mL-1; MI: 1770.5 ± 764.5 ng.mL-1; MT70: 1987.2 ± 544.9 ng.mL-1) of the drug in rats indicating a 50% reduction of the oral Cl. No effect was observed when midazolam was given intravenously. The results suggest that M. ilicifolia can inhibit the intestinal metabolism and transport of drugs mediated by CYP3A and P-gp, respectively, however, the involvement of other transporters and the clinical relevance of such interaction still need to be clarified.

480P - Drug-drug interaction profile of tepotinib with CYP3A and P-gp substrates

BackgroundTepotinib is an oral, highly selective MET inhibitor being investigated in MET-driven solid tumors. Cancer patients often receive co-medications, many of which are subject to cytochrome P450 3A (CYP3A) or P-glycoprotein (P-gp)-dependent pharmacokinetics.The potential of tepotinib to alter the exposure to such drugs was investigated in two clinical drug-drug interaction (DDI) trials. MethodsThe effect of multiple doses of the RP2D of tepotinib (500mg QD) on the exposure of single doses of the sensitive CYP3A4 substrate midazolam and the sensitive P-gp substrate dabigatran etexilate were tested in healthy subjects, using randomized single-sequence two-period cross-over designs. The primary endpoints were Cmax and AUC for the respective probe drugs; their corresponding ratios of the geometric least-squares means (GLSM) (90% CI) in the presence/absence of tepotinib were reported. Additional PK measures, safety and tolerability were also evaluated. ResultsMost participants were male (12/12 midazolam; 19/20 dabigatran etexilate); mean age 34 years (range 19–44). There was no increase in midazolam exposure with co-administration of tepotinib (Table), suggesting that no effect on the metabolism of CYP3A is to be expected. Co-administration of tepotinib led to a 39–45% increase in dabigatran etexilate exposure. No clinically relevant effects on laboratory values, vital signs or ECG parameters were observed or reported as an AE.Table480PTableCYP3A substrate (Midazolam) Ratio of GLSM% (90% CI)P-gp substrate (Dabigratan) Ratio of GLSM% (90% CI)Tepotinib + Midazolam / MidazolamTepotinib + Dabigatran etexilate / Dabigatran etexilateAUC0-t1.01 (0.89; 1.15)1.51 (1.27; 1.80)AUC0-∞1.01 (0.89; 1.15)1.45 (1.23; 1.70)Cmax1.04 (0.87;1.24)1.38 (1.22; 1.58)AUC0-t, area under the plasma concentration-time curve from time zero (= dosing time) to the last sampling time (tlast) at which the concentration is at or above the lower limit of quantification;AUC0-∞, area under the plasma concentration-time curve from time zero (= dosing time) extrapolated to infinity; Cmax, maximum plasma concentration observed; GLSM, geometric least-squares mean. ConclusionsAfter multiple doses of tepotinib at the RP2D (500mg QD), there was no relevant exposure increase of the sensitive CYP3A substrate midazolam, and a<2-fold mean exposure increase of the sensitive P-gp substrate dabigatran etexilate, indicating that tepotinib is a weak P-gp inhibitor. Tepotinib was considered safe and well tolerated in these studies of healthy volunteers. In summary, the potential of tepotinib to cause clinically relevant DDI with CYP3A4- or P-gp-dependent drugs at the intended posology is considered low. Clinical trial identificationNCT03492437 and NCT03628339. Editorial acknowledgementMedical writing assistance (funded by Merck KGaA, Darmstadt, Germany) was provided by Sandra Cuscó, PhD of Bioscript Group (Macclesfield, UK). Legal entity responsible for the studyMerck Healthcare KGaA. FundingMerck Healthcare KGaA. DisclosureÖ. Yalkinoglu: Full / Part-time employment: Merck Healthcare KGaA. A. Becker: Full / Part-time employment: Merck Healthcare KGaA. A. Krebs-Brown: Full / Part-time employment: Merck Healthcare KGaA. R. Strotmann: Full / Part-time employment: Merck Healthcare KGaA. All other authors have declared no conflicts of interest.

Functional characteristics of CYP3A4 allelic variants on the metabolism of loperamide in vitro.

BackgroundCytochrome P450 3A4 (CYP3A4) appears to be genetically polymorphic, which in turn contributes to interindividual variability in response to therapeutic drugs. Loperamide, identified as a CYP3A4 substrate, is prone to misuse and abuse and has high risks of life-threatening cardiotoxicity.MethodsThus, this study is designed to evaluate the enzymatic characteristics of 29 CYP3A4 alleles toward loperamide in vitro, including the 7 novel CYP3A4 variants (*28–*34). The incubation system (containing CYP3A4 enzyme, cytochrome b5, 0.5–20 μM loperamide, potassium phosphate buffer and nicotinamide adenine dinucleotide phosphate) was subject to 40-mins incubation at 37°C and the concentrations of N-demethylated loperamide were quantified by UPLC-MS/MS.ResultsAs a result, CYP3A4.6, .17, .20 and .30 showed extremely low activity or no activity and the rest of CYP3A4 variants presented varying degrees of decrements in catalytical activities when compared with CYP3A4.1.ConclusionAs the first study to identify the properties of these CYP3A4 variants toward loperamide metabolism, our investigation may establish the genotype–phenotype relationship for loperamide, predict an individual’s capability in response to loperamide, and provide some guidance of clinical medication and treatment for loperamide.