Survey of Pharmaceutical Industry's Best Practices around In Vitro Transporter Assessment and Implications for Drug Development: Considerations from the International Consortium for Innovation and Quality for Pharmaceutical Development Transporter Working Group.

The International Consortium for Innovation and Quality in Pharmaceutical Development Transporter Working Group had a rare opportunity to analyze a crosspharma collation of in vitro data and assay methods for the evaluation of drug transporter substrate and inhibitor potential. Experiments were generally performed in accordance with regulatory guidelines. Discrepancies, such as not considering the impact of preincubation for inhibition and free or measured in vitro drug concentrations, may be due to the retrospective nature of the dataset and analysis. Lipophilicity was a frequent indicator of crosstransport inhibition (P-gp, BCRP, OATP1B, and OCT1), with high molecular weight (MW ≥500 Da) also common for OATP1B and BCRP inhibitors. A high level of overlap in in vitro inhibition across transporters was identified for BCRP, OATP1B1, and MATE1, suggesting that prediction of DDIs for these transporters will be common. In contrast, inhibition of OAT1 did not coincide with inhibition of any other transporter. Neutrals, bases, and compounds with intermediate-high lipophilicity tended to be P-gp and/or BCRP substrates, whereas compounds with MW <500 Da tended to be OAT3 substrates. Interestingly, the majority of in vitro inhibitors were not reported to be followed up with a clinical study by the submitting company, whereas those compounds identified as substrates generally were. Approaches to metabolite testing were generally found to be similar to parent testing, with metabolites generally being equally or less potent than parent compounds. However, examples where metabolites inhibited transporters in vitro were identified, supporting the regulatory requirement for in vitro testing of metabolites to enable integrated clinical DDI risk assessment. SIGNIFICANCE STATEMENT: A diverse dataset showed that transporter inhibition often correlated with lipophilicity and molecular weight (>500 Da). Overlapping transporter inhibition was identified, particularly that inhibition of BCRP, OATP1B1, and MATE1 was frequent if the compound inhibited other transporters. In contrast, inhibition of OAT1 did not correlate with the other drug transporters tested.

Human Pharmacokinetic and CYP3A Drug-Drug Interaction Prediction of GDC-2394 Using Physiologically Based Pharmacokinetic Modeling and Biomarker Assessment.

Physiologically based pharmacokinetic (PBPK) modeling was used to predict the human pharmacokinetics and drug-drug interaction (DDI) of GDC-2394. PBPK models were developed using in vitro and in vivo data to reflect the oral and intravenous PK profiles of mouse, rat, dog, and monkey. The learnings from preclinical PBPK models were applied to a human PBPK model for prospective human PK predictions. The prospective human PK predictions were within 3-fold of the clinical data from the first-in-human study, which was used to optimize and validate the PBPK model and subsequently used for DDI prediction. Based on the majority of PBPK modeling scenarios using the in vitro CYP3A induction data (mRNA and activity), GDC-2394 was predicted to have no-to-weak induction potential at 900 mg twice daily (BID). Calibration of the induction mRNA and activity data allowed for the convergence of DDI predictions to a narrower range. The plasma concentrations of the 4ß-hydroxycholesterol (4ß-HC) were measured in the multiple ascending dose study to assess the hepatic CYP3A induction risk. There was no change in plasma 4ß-HC concentrations after 7 days of GDC-2394 at 900 mg BID. A dedicated DDI study found that GDC-2394 has no induction effect on midazolam in humans, which was reflected by the totality of predicted DDI scenarios. This work demonstrates the prospective utilization of PBPK for human PK and DDI prediction in early drug development of GDC-2394. PBPK modeling accompanied with CYP3A biomarkers can serve as a strategy to support clinical pharmacology development plans. SIGNIFICANCE STATEMENT: This work presents the application of physiologically based pharmacokinetic modeling for prospective human pharmacokinetic (PK) and drug-drug interaction (DDI) prediction in early drug development. The strategy taken in this report represents a framework to incorporate various approaches including calibration of in vitro induction data and consideration of CYP3A biomarkers to inform on the overall CYP3A-related DDI risk of GDC-2394.

Association Between Use of Pharmacokinetic-Interacting Drugs and Effectiveness and Safety of Direct Acting Oral Anticoagulants: Nested Case-Control Study.

Concomitant use of direct oral anticoagulants (DOACs) and medications with inhibition/induction effect on P-gp/CYP3A might increase risk of bleeding/treatment failure, respectively. We designed a nested case-control study within a Clalit cohort of patients with atrial fibrillation (AF) and a cohort of patients with venous thromboembolism, new users of a DOAC (January 1, 2010 to August 24, 2020). Propensity scores were constructed from demographic/clinical characteristics, and medications at cohort entry. Each case of: (i) serious bleeding event; (ii) stroke/systemic emboli (SE) in patients with AF; (iii) recurrent thromboembolism in patients with thromboembolism, was matched by age, sex, length of follow-up, year of cohort entry, DOAC type, and DOAC indication, to up to 20 controls. Within 89,284 patients with AF and venous thromboembolism and 126,302 patient-years of follow-up, there were 1,587 serious bleeding events. Risk of serious bleeding increased in association with concurrent prescription of P-gp/CYP3A4 inhibitors. Specifically, higher bleeding risk was associated with dabigatran-verapamil, rivaroxaban-verapamil, and rivaroxaban-amiodarone concurrent prescriptions: adjusted odds ratios (ORs) 2.29 (1.13-4.60), 2.18 (1.07-4.40), and 1.68 (1.14-2.49), respectively. There were 1,116 events of stroke/SE, in 79,302 DOAC-treated patients with AF and 118,124 patient-years of follow-up. Concomitant use of phenytoin, carbamazepine, valproic acid, or levetiracetam was associated with risk for stroke/SE: adjusted OR 2.18 (1.55-3.10). Risk of recurrent venous thromboembolism could not be assessed due to the low number of cases. Concurrent prescriptions of dabigatran or rivaroxaban with verapamil, and of rivaroxaban with amiodarone, are associated with increased risk for serious bleeding. Higher risk for stroke/SE in patients with AF is associated with concurrent prescriptions of DOACs with phenytoin, carbamazepine, valproic acid, or levetiracetam.

Quantitative Benefit-Risk Assessment of P-gp-Mediated Drug-Drug Interactions of Dabigatran Coadministered With Pharmacokinetic Enhancers in Patients With Renal Impairment.

Drug-drug interactions (DDIs) between dabigatran and ritonavir/cobicistat are of major concern in people living with HIV, particularly in those with impaired renal function, because they can result in increased dabigatran exposure and thus an increased risk of major bleeding events. However, the extent of this interaction and subsequent need for dose adjustment in subjects with varying degrees of renal function is currently not yet fully understood. To close this knowledge gap, we conducted an integrated population physiologically-based pharmacokinetic/pharmacodynamic analysis linking changes in dabigatran exposure due to DDIs and varying degrees of renal function to the probability of experiencing an ischemic stroke or major bleeding event within 1 year. The results of our analysis suggest that coadministration of dabigatran etexilate (dabigatran prodrug) and ritonavir/cobicistat should be avoided in subjects with severe renal impairment. A 2-hour dose separation or dabigatran etexilate dose reduction to 110 mg b.i.d. (twice daily) should be considered in subjects with moderate renal impairment when coadministered with ritonavir, while the dabigatran etexilate dose should be further reduced to 75 mg b.i.d. when coadministered with cobicistat. No dabigatran etexilate dose adjustment is needed in subjects with normal renal function receiving ritonavir, but dabigatran etexilate dose reduction to 110 mg b.i.d. should be considered when coadministered with cobicistat.

Identification of Appropriate Endogenous Biomarker for Risk Assessment of Multidrug and Toxin Extrusion Protein-Mediated Drug-Drug Interactions in Healthy Volunteers.

Endogenous biomarkers are emerging to advance clinical drug-drug interaction (DDI) risk assessment in drug development. Twelve healthy subjects received a multidrug and toxin exclusion protein (MATE) inhibitor (pyrimethamine, 10, 25, and 75 mg) in a crossover fashion to identify an appropriate endogenous biomarker to assess MATE1/2-K-mediated DDI in the kidneys. Metformin (500 mg) was also given as reference probe drug for MATE1/2-K. In addition to the previously reported endogenous biomarker candidates (creatinine and N1 -methylnicotinamide (1-NMN)), N1 -methyladenosine (m1 A) was included as novel biomarkers. 1-NMN and m1 A presented as superior MATE1/2-K biomarkers since changes in their renal clearance (CLr ) along with pyrimethamine dose were well-correlated with metformin CLr changes. The CLr of creatinine was reduced by pyrimethamine, however, its changes poorly correlated with metformin CLr changes. Nonlinear regression analysis (CLr vs. mean total concentration of pyrimethamine in plasma) yielded an estimate of the inhibition constant (Ki ) of pyrimethamine and the fraction of the clearance pathway sensitive to pyrimethamine. The in vivo Ki value thus obtained was further converted to unbound Ki using plasma unbound fraction of pyrimethamine, which was comparable to the in vitro Ki for MATE1 (1-NMN) and MATE2-K (1-NMN and m1 A). It is concluded that 1-NMN and m1 A CLr can be leveraged as quantitative MATE1/2-K biomarkers for DDI risk assessment in healthy volunteers.

Prescription of Colchicine with Other Dangerous Concomitant Medications: A Nation-Wide Survey Using the Japanese Claims Database.

The anti-inflammatory agent colchicine may cause toxic effects such as rhabdomyolysis, pancytopenia, and acute respiratory distress syndrome in cases of overdose and when patients have renal or liver impairment. As colchicine is a substrate for CYP3A4 and P-glycoprotein (P-gp), drug-drug interactions are important factors that cause fatal colchicine-related side effects. Thus, we conducted a nation-wide survey to determine the status of inappropriate colchicine prescriptions in Japan. Patients prescribed the regular use of colchicine from April 2014 to March 2017 were identified using the Japanese large health insurance claims database. As the primary endpoint, we evaluated the concomitant prescription proportions of strong CYP3A4 and/or P-gp inhibitors classified as "contraindications for co-administration" with colchicine in patients with renal or liver impairment. We defined these cases as "inappropriate colchicine prescriptions." Additionally, factors affecting inappropriate colchicine prescriptions were analyzed. Among the 3302 enrolled patients, 43 (1.30%) were inappropriately prescribed colchicine. Of these 43 patients, 11 had baseline renal and/or liver impairment. By multiple regression analysis, the primary diseases "gout" and "Behçet's disease" were extracted as independent factors for inappropriate colchicine prescriptions with odds ratios of 0.40 (95% confidence interval: 0.19-0.84) and 4.93 (95% confidence interval: 2.12-11.5), respectively. We found that approximately 1% of patients had important colchicine interactions. Particularly, Behçet's disease was a risk factor for inappropriate prescriptions, with approximately 25% of patients showing renal and/or liver impairment (classified as "contraindications for co-administration"). These findings may be useful for medical professionals who prescribe colchicine therapy.

Assessment of patient knowledge on warfarin: An item response theory approach.

WHAT IS KNOWN AND OBJECTIVE: There are no instruments to assess the patient's knowledge of oral anticoagulation with warfarin, in which the performance of the items has been evaluated through the item response theory. To evaluate psychometric properties of the Brazilian version of the Oral Anticoagulation Knowledge Test, using the item response theory. METHODS: This methodological study was developed in an anticoagulation clinic of a university hospital with a sample of 201 patients treated with warfarin. The item response theory was used to evaluate questions regarding psychometric properties and the performance of the Brazilian version of the Oral Anticoagulation Knowledge Test items. The unidimensionality hypothesis was analysed by decomposing the polychoric correlation and the Cronbach's alpha coefficient. An item characteristic curve of the 20 items of the instrument was made to identify the discrimination power of each item of the performance scale. RESULTS AND DISCUSSION: Correlations were positive and statistically significant among the 20 items, with a Cronbach's alpha coefficient of 0.82. The difficulty parameter ranged from -4.14 to 0.42. The discrimination parameter ranged from 0.41 to 1.89. The items regarding drug-drug/drug-food interactions were able to differentiate knowledge about oral anticoagulation with greater accuracy. WHAT IS NEW AND CONCLUSION: This study is the first that uses this methodology to evaluate the knowledge on oral anticoagulation therapy with warfarin. The evaluation using item response theory showed that the Brazilian version of the Oral Anticoagulation Knowledge Test is suitable for assessing the patient's knowledge of oral anticoagulation with warfarin. Thus, our findings confirmed the utility of this instrument and provided an essential point of reference for the structuring of health education activities that ensure the individualization of educational interventions in patients on warfarin.

Prevalence and risk factors of drug-related problems identified in pharmacy-based medication reviews.

Background Medication safety is a major health concern, especially for older patients, in whom drug-related problems occur frequently as a consequence of polypharmacy and frailty, increasing the risk of adverse drug events. Objective To investigate the prevalence and types of drug-related problems in community pharmacies and to identify associated risk factors in order to adjust the focus of care. Setting 300 German community pharmacies in Saxony-Anhalt (Germany). Method In April 2015, community pharmacists conducted brown bag medication reviews for primary care patients, in which they identified and solved drug-related problems with patients or their physicians. Data from these reviews were analyzed, including frequency and nature of problems and their respective resolutions. Potentially inappropriate medications according to the PRISCUS list were identified by post hoc analysis. Risk factors for drug-related problems were determined using bivariate and multivariate logistic regression analysis. Main outcome measure Prevalence and risk factors of drug-related problems. Results 1090 medication reviews were conducted. On average, patients were 72.0 ± 9.1 years old and had 10.6 ± 3.7 medications, 62.0% (n = 676) presented a medication plan. Knowledge gaps about medications were detected in almost a third of patients (n = 345). Drug-related problems were identified in 84.2% (n = 918) of patients (in 3836 medications). Frequent problems concerned drug-drug-interactions (53.7%, n = 585) as well as drug use and adherence (46.7%, n = 509). Most problems (72.2%, n = 2769) were resolved between pharmacist and patient. Knowledge gaps and the number of drugs were independently associated with a higher risk of drug-related problems. For older patients, potentially inappropriate medications were a risk factor in bivariate, but not in multivariate analysis. Conclusion Pharmacists identified and resolved considerable rates of drug-related problems, suggesting that they are capable and well-positioned to conduct medication reviews. Knowledge gaps, the number of drugs, patient age and, in older patients, potentially inappropriate medications may indicate an increased risk for drug-related problems.

Therapeutic drug monitoring of antiepileptic drugs: current status and future prospects.

Introduction: Antiepileptic drugs (AEDs) are the cornerstone of treatment of patients with epilepsy, and there are presently 27 licensed AEDs making AEDs among the most common medications for which therapeutic drug monitoring (TDM) is performed. The aim of this review is to provide an overview of the current evidence of the use and implementation of AED TDM in patients with epilepsy and other non-epilepsy conditions.Areas covered: The pharmacokinetic variability of AEDs is extensive, resulting in pronounced variability in serum concentrations between patients. TDM may thus be useful to individualize the treatment of patients with epilepsy and also in non-epilepsy conditions. Indications for TDM include settings where pharmacokinetic variability is anticipated (e.g. in children, the elderly, during pregnancy, and patients prescribed polytherapy resulting in drug interactions) and drug adherence. TDM contributes to provide a quality assurance of the treatment. Patient management is, therefore, best guided by the determination of individual therapeutic concentrations.Expert opinion: Because of pharmacokinetic variability is prevalent among AEDs, TDM allows a bespoke approach to epilepsy care allowing dose adjustments based on measured drug concentrations so as to optimize clinical outcome. Future advances include the use of additional markers of toxicity and genetic variability so as to further aid individualization and optimize AED treatment.

Significance of a clinical pharmacist-led comprehensive medication management program for hospitalized oncology patients.

Background The use of highly toxic drugs in cancer treatment and supportive care medications exposes patients to an increased number of drug-related problems (DRPs). Clinical pharmacists contribute to the optimal use of medications by intervening in identified drug-related problems. Objective To evaluate the relevance of a comprehensive medication management service in oncology patients. Setting Marmara University Teaching and Research Hospital Medical Oncology Ward, Istanbul, Turkey. Methods This prospective study was carried out between December 2015 and April 2016 with adult patients with confirmed malignancy. Comprehensive medication management was performed by the clinical pharmacist throughout the patient's hospital stay. The medication-related data as well as data regarding demographic and general health status of the patients were reviewed for the presence of drug-related problems. The identified problems, interventions and acceptance rate by physicians were recorded with the help of the Pharmaceutical Care Network Europe V6.0 (PCNE) classification. Main outcome measures Number and causes of drug-related problems, nature and acceptance rate of clinical pharmacist interventions and rate of problems solved. Results The study included 137 patients. The mean (SD) age of the patients was 58 (14.6) years. A total of 481 drug-related problems were recorded. The most frequent drug-related problems were 'adverse drug events [including drug interactions]' (n = 376), 'untreated indications' (n = 59) and 'unnecessary drug treatment' (n = 25). Inappropriate combination of drugs was the cause of 73.2% of the total problems. Interventions were made to stop administration of a suitable drug if the combination with another drug was contraindicated while prescribers were mostly informed about major drug interactions. The prescribers approved 93% of the total intervention proposals. The majority (90.9%) of the identified problems were totally solved. Conclusion Integration of clinical pharmacy services through a comprehensive medication management program in oncology will help to reduce the number of drug-related problems.

Come Dance With Me: Transformative Changes in the Science and Practice of Drug-Drug Interactions.

The past 2 decades have witnessed transformative changes in our approach to drug-drug interactions (DDIs) from scientific research to clinical practice. Collaborative cooperation across the sectors of academia, pharmaceutical industry, providers of translational research tools and services, global regulatory agencies, and healthcare providers has created and galvanized a science-informed and patient-centered approach. Multidisciplinary innovations in mechanistic assessment of absorption, distribution, metabolism, and excretion (ADME), population pharmacology and pharmacogenetics, physiologically based modeling, and regulatory science have enabled a profound shift in mindset from risk aversion to informative prescribing guidance for optimal risk management. Foundational to this transformation is a commitment to maximizing the value of innovative therapeutics for all patients and across clinical contexts of use through rational knowledge management and translation based on the totality of best available evidence, thereby removing the void that can lead to arbitrary decisions in clinical therapeutics.

Factors predicting home medication management practices among chronically ill older population of selected districts of Nepal.

BACKGROUND: Older population often have multiple and complex needs that are consequently challenged by the presence of polypharmacy, adverse drug reactions and drug-drug interaction. We aimed to determine home medication management practices (MMP) and its associated factors among chronically ill older population of selected districts of Nepal. METHODS: A community based cross-sectional survey was conducted among 386 chronically ill older individuals from selected areas of Nepal between April to September 2016. Appropriateness of MMP was assessed through scores of questions using interview method. Multivariate logistic regression analysis using potential variables from bivariate analysis were used to determine factors affecting MMP. RESULTS: The overall home MMP was mostly inappropriate (80.1%). Most participants had multiple prescribers for single disease (202, 52.3%) and inappropriate medication storage (188, 48.7%). Though the majority of them had drug administration schedule (378, 97.9%), expired medicines were also used (2, 0.5%). Regression analysis showed less than one year duration of disease (odds ratio [OR] = 3.901, 95% confidence interval [CI] = 1.528 to 9.959, P = 0.004), 1-2 years duration of disease (OR = 2.415, 95% CI = 1.210 to 4.821, P = 0.012) and smokers (OR = 2.025, 95% CI = 1.036 to 3.956, P = 0.039) as the major factors affecting appropriate home MMP. CONCLUSIONS: The home MMP was associated with duration of disease and smoking status among chronically ill older patients living in selected districts of Nepal. Proper counselling and monitoring of such patients might be necessary to improve the practice.

Drug-Drug Interactions of Infectious Disease Treatments in Low-Income Countries: A Neglected Topic?

Despite recent advances in recognizing and reducing the risk of drug-drug interactions (DDIs) in developed countries, there are still significant challenges in managing DDIs in low-income countries (LICs) worldwide. In the treatment of major infectious diseases in these regions, multiple factors contribute to ineffective management of DDIs that lead to loss of efficacy or increased risk of adverse events to patients. Some of these difficulties, however, can be overcome. This review aims to evaluate the inherent complexities of DDI management in LICs from pharmacological standpoints and illustrate the unique barriers to effective management of DDIs, such as the challenges of co-infection and treatment settings. A better understanding of comprehensive drug-related properties, population-specific attributes, such as physiological changes associated with infectious diseases, and the use of modeling and simulation techniques are discussed, as they can facilitate the implementation of optimal treatments for infectious diseases at the individual patient level.

Lack of inhibition of CYP2C8 by saroglitazar magnesium: In vivo assessment using montelukast, rosiglitazone, pioglitazone, repaglinide and paclitaxel as victim drugs in Wistar rats.

Saroglitazar, a PPAR αÒ® agonist, is currently undergoing global development for the treatment of NASH and other indications. Saroglitazar showed CYP2C8 inhibition in human liver microsomes (IC50: 2.9 µM). The aim was to carry out drug-drug interaction (DDI) studies in Wistar rats using saroglitazar (perpetrator drug) with five CYP2C8 substrates. Also, the in vitro CYP2C8 inhibitory potential of saroglitazar in rat liver microsomes (RLM) was evaluated to justify use of preclinical model. The oral pharmacokinetics of various CYP2C8 substrates; montelukast, rosiglitazone, pioglitazone, repaglinide and intravenous pharmacokinetics of paclitaxel was assessed in the presence/absence of oral saroglitazar (4 mg/kg) in Wistar rats. A separate study was performed to assess the oral pharmacokinetics of saroglitazar. Serial blood samples were collected from all studies and the harvested plasma were stored frozen until bioanalysis. LC-MS/MS was used for the analysis of various analytes; concentration data was subjected to noncompartmental pharmacokinetic analysis. Statistical tests (unpaired t-test) were employed to judge the level of DDI. Generally, the pharmacokinetics of CYP2C8 substrates was not affected by the concomitant intake of saroglitazar as judged by the overall exposure (AUC0-last and AUC0-inf) and elimination half-life. The CYP2C8 IC50 of 4.5 µM in RLM for saroglitazar, supported the use of rats for this DDI study. In conclusion, pharmacokinetic data of diverse CYP2C8 substrates suggested that coadministration of saroglitazar did not cause clinically relevant DDI.

Direct assessment of adherence and drug interactions in patients with hypertensive crisis-A cross-sectional study in the Emergency Department.

Though drug adherence is supposed to be low in hypertensive crisis (HTN-C), there are no data available from direct adherence assessments. The aim of the present study was to evaluate adherence to prescribed antihypertensives and potential interactions of concomitant drugs and foods with prescribed antihypertensives in patients with HTN-C by a direct evaluation via biochemical urine analysis. In the present cross-sectional study, 100 patients with HTN-C, admitted to the emergency department (ED), were included. A biochemical urine analysis using gas chromatography-tandem mass spectrometry was performed. Out of 100 patients, 86 received antihypertensives. Urine analyses could be evaluated unambiguously in 62 patients. In 15 of these 62 patients (24%), a nonadherence could be demonstrated, and in 21 patients (34%), a partial nonadherence could be demonstrated. Patients with nonadherence or partial nonadherence showed a longer hypertension history (15[5-22] vs 10[3-15] years, P = 0.04) were prescribed more general medication (number 7.1 ± 3.4 vs 3.4 ± 1.8; P < 0.01) as well as antihypertensive drugs (number 2.8 ± 1.1 vs 1.5 ± 0.7, P < 0.01). A potential BP-raising trigger by medications or food interaction was frequently detectable, predominantly with nonsteroidal anti-inflammatory drugs (NSAIDs; n = 38), glucocorticoids (n = 8), antidepressants (n = 10), and licorice (n = 10). Nonadherence and partial nonadherence to prescribed antihypertensives might play a crucial role for the occurrence of HTN-C. However, further case-controlled studies are needed to confirm the present findings. Ingestion of concurrent over-the-counter drugs such as NSAIDs but also prescribed drugs as well as aliments may lead to critical BP elevation. In order to prevent HTN-C, the present findings emphasize the importance for clinicians to pay attention to the issue of adherence and co-medication.

Assessment of Pharmacokinetic Drug-Drug Interactions in Humans: In Vivo Probe Substrates for Drug Metabolism and Drug Transport Revisited.

Pharmacokinetic parameters of selective probe substrates are used to quantify the activity of an individual pharmacokinetic process (PKP) and the effect of perpetrator drugs thereon in clinical drug-drug interaction (DDI) studies. For instance, oral caffeine is used to quantify hepatic CYP1A2 activity, and oral dagibatran etexilate for intestinal P-glycoprotein (P-gp) activity. However, no probe substrate depends exclusively on the PKP it is meant to quantify. Lack of selectivity for a given enzyme/transporter and expression of the respective enzyme/transporter at several sites in the human body are the main challenges. Thus, a detailed understanding of the role of individual PKPs for the pharmacokinetics of any probe substrate is essential to allocate the effect of a perpetrator drug to a specific PKP; this is a prerequisite for reliably informed pharmacokinetic models that will allow for the quantitative prediction of perpetrator effects on therapeutic drugs, also in respective patient populations not included in DDI studies.

Mechanistic Assessment of the Effect of Omeprazole on the In Vivo Pharmacokinetics of Itraconazole in Healthy Volunteers.

BACKGROUND AND OBJECTIVE: SUBA-itraconazole and Sporanox are two oral formulations of itraconazole. Drug-drug interactions with omeprazole have been previously reported; however, mechanistic understanding of the pharmacological and physiological interactions of omeprazole with orally administered itraconazole within a population modeling paradigm is lacking. The objective of this analysis was to mechanistically describe and quantify the effect of omeprazole on the pharmacokinetics of itraconazole and its major metabolite, hydroxyitraconazole from the SUBA itraconazole and Sporanox formulations. METHODS: An in vitro-in vivo (IVIV) pharmacokinetic model of itraconazole and hydroxyitraconazole was developed including data from an omeprazole interaction study with SUBA itraconazole. Meta-models of gastric pH for healthy subjects and subjects receiving omeprazole were integrated into the IVIV model to capture omeprazole-mediated gastric pH changes on itraconazole dissolution and absorption. RESULTS: Omeprazole influenced the kinetics of itraconazole through altering the dissolution and absorption due to the pH-dependent solubility of itraconazole, inhibition of efflux transporters, and inhibiting the metabolism of itraconazole and hydroxyitraconazole. The model-predicted population effects of omeprazole on itraconazole from SUBA-itraconazole were to increase the area under the concentration-time curve (AUC0-24) and maximum concentration (Cmax) by 35 and 31%, respectively, and to decrease AUC0-24 and Cmax from Sporanox by 68 and 76%, respectively. CONCLUSION: Unlike SUBA itraconazole, which requires basic pH for itraconazole release, the omeprazole-induced pH-mediated reduction in Sporanox dissolution overrides any increased exposure from the drug-drug interaction at hepatic metabolizing enzymes or efflux transporters. The model presented here is the most complete quantitative description of the pharmacokinetics of itraconazole and hydroxyitraconazole currently available.

In Vitro Assessment of Potential for CYP-Inhibition-Based Drug-Drug Interaction Between Vonoprazan and Clopidogrel.

BACKGROUND AND OBJECTIVES: It was recently proposed that CYP-mediated drug-drug interactions (DDIs) of vonoprazan with clopidogrel and prasugrel can attenuate the antiplatelet actions of the latter two drugs. Clopidogrel is metabolized to the pharmacologically active metabolite H4 and its isomers by multiple CYPs, including CYP2C19 and CYP3A4. Therefore, to investigate the possibility of CYP-based DDIs, in vitro metabolic inhibition studies using CYP probe substrates or radiolabeled clopidogrel and human liver microsomes (HLMs) were conducted in this work. METHODS: Reversible inhibition studies focusing on the effects of vonoprazan on CYP marker activities and the formation of the [14C]clopidogrel metabolite H4 were conducted with and without pre-incubation using HLMs. Time-dependent inhibition (TDI) kinetics were also measured. RESULTS: It was found that vonoprazan is not a significant direct inhibitor of any CYP isoforms (IC50 ≥ 16 µM), but shows the potential for TDI of CYP2B6, CYP2C19, and CYP3A4/5. This TDI was weaker than the inhibition induced by the corresponding reference inhibitors ticlopidine, esomeprazole, and verapamil, based on the measured potencies (kinact/KI ratio and the R2 value). In a more direct in vitro experiment, vonoprazan levels of up to 10 µM (a 100-fold higher concentration than the plasma Cmax of 75.9 nM after taking 20 mg once daily for 7 days) did not suppress the formation of the active metabolite H4 or other oxidative metabolites of [14C]clopidogrel in a reversible or time-dependent manner. Additionally, an assessment of clinical trials and post-marketing data suggested no evidence of a DDI between vonoprazan and clopidogrel. CONCLUSIONS: The body of evidence shows that the pharmacodynamic DDI reported between vonoprazan and clopidogrel is unlikely to be caused by the inhibition of CYP2B6, CYP2C19, or CYP3A4/5 by vonoprazan.

Considerations from the Innovation and Quality Induction Working Group in Response to Drug-Drug Interaction Guidances from Regulatory Agencies: Focus on CYP3A4 mRNA In Vitro Response Thresholds, Variability, and Clinical Relevance.

The Innovation and Quality Induction Working Group presents an assessment of best practice for data interpretation of in vitro induction, specifically, response thresholds, variability, application of controls, and translation to clinical risk assessment with focus on CYP3A4 mRNA. Single concentration control data and Emax/EC50 data for prototypical CYP3A4 inducers were compiled from many human hepatocyte donors in different laboratories. Clinical CYP3A induction and in vitro data were gathered for 51 compounds, 16 of which were proprietary. A large degree of variability was observed in both the clinical and in vitro induction responses; however, analysis confirmed in vitro data are able to predict clinical induction risk. Following extensive examination of this large data set, the following recommendations are proposed. a) Cytochrome P450 induction should continue to be evaluated in three separate human donors in vitro. b) In light of empirically divergent responses in rifampicin control and most test inducers, normalization of data to percent positive control appears to be of limited benefit. c) With concentration dependence, 2-fold induction is an acceptable threshold for positive identification of in vitro CYP3A4 mRNA induction. d) To reduce the risk of false positives, in the absence of a concentration-dependent response, induction ≥ 2-fold should be observed in more than one donor to classify a compound as an in vitro inducer. e) If qualifying a compound as negative for CYP3A4 mRNA induction, the magnitude of maximal rifampicin response in that donor should be ≥ 10-fold. f) Inclusion of a negative control adds no value beyond that of the vehicle control.