Sandwich-cultured hepatocytes: an in vitro model to evaluate hepatobiliary transporter-based drug interactions and hepatotoxicity

Sandwich-cultured hepatocytes (SCH) are a powerful in vitro tool that can be utilized to study hepatobiliary drug transport, species differences in drug transport, transport protein regulation, drug-drug interactions, and hepatotoxicity. This review provides an up-to-date summary of the SCH model, including a brief history of, and introduction to, the use of SCH, as well as methodology to evaluate hepatobiliary drug disposition. A summary of the literature that has utilized this model to examine the interplay between drug-metabolizing enzymes and transport proteins, drug-drug interactions at the transport level, and hepatotoxicity as a result of altered hepatic transport also is provided.

Pitavastatin is a more sensitive and selective organic anion-transporting polypeptide 1B clinical probe than rosuvastatin

AIMS

Rosuvastatin and pitavastatin have been proposed as probe substrates for the organic anion-transporting polypeptide (OATP) 1B, but clinical data on their relative sensitivity and selectivity to OATP1B inhibitors are lacking. A clinical study was therefore conducted to determine their relative suitability as OATP1B probes using single oral (PO) and intravenous (IV) doses of the OATP1B inhibitor rifampicin, accompanied by a comprehensive in vitro assessment of rifampicin inhibitory potential on statin transporters.

METHODS

The clinical study comprised of two separate panels of eight healthy subjects. In each panel, subjects were randomized to receive a single oral dose of rosuvastatin (5 mg) or pitavastatin (1 mg) administered alone, concomitantly with rifampicin (600 mg) PO or IV. The in vitro transporter studies were performed using hepatocytes and recombinant expression systems.

RESULTS

Rifampicin markedly increased exposures of both statins, with greater differential increases after PO vs. IV rifampicin only for rosuvastatin. The magnitudes of the increases in area under the plasma concentration-time curve were 5.7- and 7.6-fold for pitavastatin and 4.4- and 3.3-fold for rosuvastatin, after PO and IV rifampicin, respectively. In vitro studies showed that rifampicin was an inhibitor of OATP1B1 and OATP1B3, breast cancer resistance protein and multidrug resistance protein 2, but not of organic anion transporter 3.

CONCLUSIONS

The results indicate that pitavastatin is a more sensitive and selective and thus preferred clinical OATP1B probe substrate than rosuvastatin, and that a single IV dose of rifampicin is a more selective OATP1B inhibitor than a PO dose.

Effect of pregnane X receptor ligands on transport mediated by human OATP1B1 and OATP1B3

The pregnane X receptor is a ligand-activated transcription factor that is abundantly expressed in hepatocytes. Numerous drugs are pregnane X receptor ligands. To bind to their receptor they must cross the sinusoidal membrane. Organic anion transporting polypeptides 1B1 and 1B3 (OATP1B1 and OATP1B3) are polyspecific transporters expressed at the sinusoidal membrane of human hepatocytes. They mediate transport of a variety of drugs including the pregnane X receptor ligands rifampicin and dexamethasone. To test whether additional pregnane X receptor ligands interact with OATP1B1- and 1B3-mediated transport, we developed Chinese Hamster Ovary (CHO) cell lines stably expressing OATP1B1 or 1B3 at high levels. OATP1B1- and 1B3-mediated estradiol-17beta-glucuronide uptake was inhibited by several pregnane X receptor ligands in a concentration dependent way. IC(50) values for rifampicin, paclitaxel, mifepristone, and troglitazone were within their respective pharmacological free plasma concentrations. Kinetic analysis revealed that clotrimazole inhibits OATP1B1-mediated estradiol-17beta-glucuronide transport with a K(i) of 7.7+/-0.3 microM in a competitive way. However, uptake of OATP1B3-mediated estradiol-17beta-glucuronide was stimulated and this stimulation was due to an increased apparent affinity. Transport of estrone-3-sulfate was hardly affected while all other substrates tested were inhibited. Additional azoles like fluconazole, ketoconazole and miconazole did not stimulate OATP1B3-mediated estradiol-17beta-glucuronide transport. In summary, these results demonstrate that pregnane X receptor ligands, by inhibiting or stimulating OATP-mediated uptake, can lead to drug-drug interactions at the transporter level.

Effect of ketoconazole and diltiazem on the pharmacokinetics of apixaban, an oral direct factor Xa inhibitor

AIM

Apixaban is an orally active inhibitor of coagulation factor Xa and is eliminated by multiple pathways, including renal and non-renal elimination. Non-renal elimination pathways consist of metabolism by cytochrome P450 (CYP) enzymes, primarily CYP3A4, as well as direct intestinal excretion. Two single sequence studies evaluated the effect of ketoconazole (a strong dual inhibitor of CYP3A4 and P-glycoprotein [P-gp]) and diltiazem (a moderate CYP3A4 inhibitor and a P-gp inhibitor) on apixaban pharmacokinetics in healthy subjects.

METHOD

In the ketoconazole study, 18 subjects received apixaban 10 mg on days 1 and 7, and ketoconazole 400 mg once daily on days 4-9. In the diltiazem study, 18 subjects received apixaban 10 mg on days 1 and 11 and diltiazem 360 mg once daily on days 4-13.

RESULTS

Apixaban maximum plasma concentration and area under the plasma concentration-time curve extrapolated to infinity increased by 62% (90% confidence interval [CI], 47, 78%) and 99% (90% CI, 81, 118%), respectively, with co-administration of ketoconazole, and by 31% (90% CI, 16, 49%) and 40% (90% CI, 23, 59%), respectively, with diltiazem.

CONCLUSION

A 2-fold and 1.4-fold increase in apixaban exposure was observed with co-administration of ketoconazole and diltiazem, respectively.

The challenge of HIV treatment in an era of polypharmacy

INTRODUCTION

The availability of potent antiretroviral therapy has transformed HIV infection into a chronic disease such that people living with HIV (PLWH) have a near normal life expectancy. However, there are continuing challenges in managing HIV infection, particularly in older patients, who often experience age-related comorbidities resulting in complex polypharmacy and an increased risk for drug-drug interactions. Furthermore, age-related physiological changes may affect the pharmacokinetics and pharmacodynamics of both antiretrovirals and comedications thereby predisposing elderly to adverse drug reactions. This review provides an overview of the therapeutic challenges when treating elderly PLWH (i.e. >65 years). Particular emphasis is placed on drug-drug interactions and other common prescribing issues (i.e. inappropriate drug use, prescribing cascade, drug-disease interaction) encountered in elderly PLWH.

DISCUSSION

Prescribing issues are common in elderly PLWH due to the presence of age-related comorbidities, organ dysfunction and physiological changes leading to a higher risk for drug-drug interactions, drugs dosage errors and inappropriate drug use.

CONCLUSIONS

The high prevalence of prescribing issues in elderly PLWH highlights the need for ongoing education on prescribing principles and the optimal management of individual patients. The knowledge of adverse health outcomes associated with polypharmacy and inappropriate prescribing should ensure that there are interventions to prevent harm including medication reconciliation, medication review and medication prioritization according to the risks/benefits for each patient.

2019 update of the European AIDS Clinical Society Guidelines for treatment of people living with HIV version 10.0

BACKGROUND

The European AIDS Clinical Society (EACS) Guidelines cover key aspects of HIV management with major updates every two years.

GUIDELINE HIGHLIGHTS

The 2019 Guidelines were extended with a new section focusing on drug-drug interactions and other prescribing issues in people living with HIV (PLWH). The recommendations for treatment-naïve PLWH were updated with four preferred regimens favouring unboosted integrase inhibitors. A two-drug regimen with dolutegravir and lamivudine, and a three-drug regimen including doravirine were also added to the recommended initial regimens. Lower thresholds for hypertension were expanded to all PLWH and for cardiovascular disease prevention, the 10-year predicted risk threshold for consideration of antiretroviral therapy (ART) modification was lowered from 20% to 10%. Frailty and obesity were added as new topics. It was specified to use urine albumin to creatinine ratio to screen for glomerular disease and urine protein to creatinine ratio for tubular diseases, and thresholds were streamlined with the Kidney Disease: Improving Global Outcomes (KDIGO) recommendations. Hepatitis C virus (HCV) treatment recommendations were split into preferred and alternative treatment options. The algorithm for management of recently acquired HCV infection was updated and includes recommendations for early chronic infection management. Treatment of resistant tuberculosis (TB) was streamlined with the World Health Organization (WHO) recommendations, and new tables on immune reconstitution inflammatory syndrome, on when to start ART in the presence of opportunistic infections and on TB drug dosing were included.

CONCLUSIONS

The EACS Guidelines underwent major revisions of all sections in 2019. They are available in four different formats including a new interactive web-based version and are translated into Chinese, French, German, Japanese, Portuguese, Russian and Spanish.

Allosteric P450 mechanisms: multiple binding sites, multiple conformers or both?

According to the initial hypothesis on the mechanisms of cooperativity in drug-metabolizing cytochromes P450, a loose fit of a single substrate molecule in the P450 active site results in a requirement for the binding of multiple ligand molecules for efficient catalysis. Although simultaneous occupancy of the active site by multiple ligands is now well established, there is increasing evidence that the mechanistic basis of cooperativity also involves an important ligand-induced conformational transition. Moreover, recent studies demonstrate that the conformational heterogeneity of the enzyme is stabilized by ligand-dependent interactions of several P450 molecules. Application of the concept of an oligomeric allosteric enzyme to microsomal cytochromes P450 in combination with a general paradigm of multiple ligand occupancy of the active site provides an excellent explanation for complex manifestations of the atypical kinetic behavior of the enzyme.

Identification of Febuxostat as a New Strong ABCG2 Inhibitor: Potential Applications and Risks in Clinical Situations

ATP-binding cassette transporter G2 (ABCG2) is a plasma membrane protein that regulates the pharmacokinetics of a variety of drugs and serum uric acid (SUA) levels in humans. Despite the pharmacological and physiological importance of this transporter, there is no clinically available drug that modulates ABCG2 function. Therefore, to identify such drugs, we investigated the effect of drugs that affect SUA levels on ABCG2 function. This strategy was based on the hypothesis that the changes of SUA levels might caused by interaction with ABCG2 since it is a physiologically important urate transporter. The results of the in vitro screening showed that 10 of 25 drugs investigated strongly inhibited the urate transport activity of ABCG2. Moreover, febuxostat was revealed to be the most promising candidate of all the potential ABCG2 inhibitors based on its potent inhibition at clinical concentrations; the half-maximal inhibitory concentration of febuxostat was lower than its maximum plasma unbound concentrations reported. Indeed, our in vivo study demonstrated that orally administered febuxostat inhibited the intestinal Abcg2 and, thereby, increased the intestinal absorption of an ABCG2 substrate sulfasalazine in wild-type mice, but not in Abcg2 knockout mice. These results suggest that febuxostat might inhibit human ABCG2 at a clinical dose. Furthermore, the results of this study lead to a proposed new application of febuxostat for enhancing the bioavailability of ABCG2 substrate drugs, named febuxostat-boosted therapy, and also imply the potential risk of adverse effects by drug-drug interactions that could occur between febuxostat and ABCG2 substrate drugs.

Cooperative properties of cytochromes P450

Cytochromes P450 form a large and important class of heme monooxygenases with a broad spectrum of substrates and corresponding functions, from steroid hormone biosynthesis to the metabolism of xenobiotics. Despite decades of study, the molecular mechanisms responsible for the complex non-Michaelis behavior observed with many members of this superfamily during metabolism, often termed 'cooperativity', remain to be fully elucidated. Although there is evidence that oligomerization may play an important role in defining the observed cooperativity, some monomeric cytochromes P450, particularly those involved in xenobiotic metabolism, also display this behavior due to their ability to simultaneously bind several substrate molecules. As a result, formation of distinct enzyme-substrate complexes with different stoichiometry and functional properties can give rise to homotropic and heterotropic cooperative behavior. This review aims to summarize the current understanding of cooperativity in cytochromes P450, with a focus on the nature of cooperative effects in monomeric enzymes.

A Human Renal Proximal Tubule Cell Line with Stable Organic Anion Transporter 1 and 3 Expression Predictive for Antiviral-Induced Toxicity

Drug-induced nephrotoxicity still hampers drug development, because current translation from in vitro or animal studies to human lacks high predictivity. Often, renal adverse effects are recognized only during clinical stages of drug development. The current study aimed to establish a robust and a more complete human cell model suitable for screening of drug-related interactions and nephrotoxicity. In addition to endogenously expressed renal organic cation transporters and efflux transporters, conditionally immortalized proximal tubule epithelial cells (ciPTEC) were completed by transduction of cells with the organic anion transporter (OAT) 1 or OAT3. Fluorescence-activated cell sorting upon exposure to the OAT substrate fluorescein successfully enriched transduced cells. A panel of organic anions was screened for drug-interactions in ciPTEC-OAT1 and ciPTEC-OAT3. The cytotoxic response to the drug-interactions with antivirals was further examined by cell viability assays. Upon subcloning, concentration-dependent fluorescein uptake was found with a higher affinity for ciPTEC-OAT1 (K_m = 0.8 ± 0.1 μM) than ciPTEC-OAT3 (K_m = 3.7 ± 0.5 μM). Co-exposure to known OAT1 and/or OAT3 substrates (viz. para-aminohippurate, estrone sulfate, probenecid, furosemide, diclofenac, and cimetidine) in cultures spanning 29 passage numbers revealed relevant inhibitory potencies, confirming the robustness of our model for drug-drug interactions studies. Functional OAT1 was directly responsible for cytotoxicity of adefovir, cidofovir, and tenofovir, while a drug interaction with zidovudine was not associated with decreased cell viability. Our data demonstrate that human-derived ciPTEC-OAT1 and ciPTEC-OAT3 are promising platforms for highly predictive drug screening during early phases of drug development.

Ritonavir is the best alternative to ketoconazole as an index inhibitor of cytochrome P450-3A in drug-drug interaction studies

AIMS

The regulatory prohibition of ketoconazole as a CYP3A index inhibitor in drug-drug interaction (DDI) studies has compelled consideration of alternative inhibitors.

METHODS

The biomedical literature was searched to identify DDI studies in which oral midazolam (MDZ) was the victim, and the inhibitory perpetrator was either ketoconazole, itraconazole, clarithromycin, or ritonavir. The ratios (RAUC ) of total area under the curve (AUC) for MDZ with inhibitor divided by MDZ AUC in the control condition were aggregated across individual studies for each inhibitor.

RESULTS

Mean (± SE) RAUC values were: ketoconazole (15 studies, 131 subjects), 11.5 (±1.2); itraconazole (five studies, 48 subjects), 7.3 (±1.0); clarithromycin (five studies, 73 subjects), 6.5 (±10.9); and ritonavir (13 studies, 159 subjects), 14.5 (±2.0). Differences among inhibitors were significant (F = 5.31, P < 0.005). RAUC values were not significantly related to inhibitor dosage or to duration of inhibitor pre-exposure prior to administration of MDZ.

CONCLUSIONS

Ritonavir produces CYP3A inhibition equivalent to or greater than ketoconazole, and is the best index CYP3A inhibitor alternative to ketoconazole. Cobicistat closely resembles ritonavir in structure and function, and can also be considered. Itraconazole and clarithromycin are not suitable alternatives since they do not produce inhibition comparable with ketoconazole or ritonavir, and have other significant disadvantages as well.

Application of PBPK Modeling and Simulation for Regulatory Decision Making and Its Impact on US Prescribing Information: An Update on the 2018-2019 Submissions to the US FDA's Office of Clinical Pharmacology

Since 2016, results from physiologically based pharmacokinetic (PBPK) analyses have been routinely found in the clinical pharmacology section of regulatory applications submitted to the US Food and Drug Administration (FDA). In 2018, the Food and Drug Administration's Office of Clinical Pharmacology published a commentary summarizing the application of PBPK modeling in the submissions it received between 2008 and 2017 and its impact on prescribing information. In this commentary, we provide an update on the application of PBPK modeling in submissions received between 2018 and 2019 and highlight a few notable examples.

Pharmacokinetic and pharmacodynamic drug interactions with new oral anticoagulants: what do they mean for patients with atrial fibrillation?

OBJECTIVE

To review pharmacokinetic and pharmacodynamic drug-drug interactions (DDIs) involving new oral anticoagulants for atrial fibrillation.

DATA SOURCES

A literature search was conducted via PubMed and the Cochrane database to identify DDI studies using the terms drug interactions, dabigatran, rivaroxaban, and apixaban. Prescribing information and Food and Drug Administration briefing documents were used to supplement published data.

STUDY SELECTION AND DATA EXTRACTION

English publications identified on Medline from 2005 up to August 2013 and US prescribing information for approved oral anticoagulants.

DATA SYNTHESIS

Articles reviewed focused on drugs affecting the permeability glycoprotein (P-gp) efflux transporter protein and/or cytochrome P (CYP) 450 3A4 enzymes, and pharmacodynamic DDIs when drugs are administered concomitantly. Phase I DDI studies have reported pharmacokinetic DDIs mediated by P-gp alone (dabigatran etexilate) or in combination with CYP3A4 enzymes (rivaroxaban and apixaban). Dabigatran etexilate should not be administered with any P-gp inhibitor in patients with severe renal impairment. Briefing documents indicate that rivaroxaban and apixaban should not be used with drugs that are strong inhibitors of both P-gp and CYP3A4. DDI studies involving rifampicin suggest that rivaroxaban and apixaban should be avoided when strong inducers of P-gp and CYP3A4 are used concurrently. Concomitant use of apixaban and strong dual inhibitors of P-gp and CYP3A4 should be avoided or the dose reduced. Five randomized clinical trials report additive effects with rivaroxaban, dabigatran, and apixaban when used concomitantly with antiplatelet agents; bleeding rates have been found to be higher, especially with dual antiplatelet therapy.

CONCLUSIONS

Awareness of drugs that alter the function of the P-gp efflux transporter protein and CYP3A4 enzymes and provide additive effects should enable prescribers to anticipate and avoid potential DDIs involving the new oral anticoagulants. To this end, briefing documents and prescribing information have applied cautionary measures for individuals treated with these newer anticoagulants.

Advancing Predictions of Tissue and Intracellular Drug Concentrations Using In Vitro, Imaging and Physiologically Based Pharmacokinetic Modeling Approaches

This white paper examines recent progress, applications, and challenges in predicting unbound and total tissue and intra/subcellular drug concentrations using in vitro and preclinical models, imaging techniques, and physiologically based pharmacokinetic (PBPK) modeling. Published examples, regulatory submissions, and case studies illustrate the application of different types of data in drug development to support modeling and decision making for compounds with transporter-mediated disposition, and likely disconnects between tissue and systemic drug exposure. The goals of this article are to illustrate current best practices and outline practical strategies for selecting appropriate in vitro and in vivo experimental methods to estimate or predict tissue and plasma concentrations, and to use these data in the application of PBPK modeling for human pharmacokinetic (PK), efficacy, and safety assessment in drug development.

The Fe-N-C Nanozyme with Both Accelerated and Inhibited Biocatalytic Activities Capable of Accessing Drug-Drug Interactions

Emerging as a cost-effective and robust enzyme mimic, nanozymes have drawn increasing attention with broad applications ranging from cancer therapy to biosensing. Developing nanozymes with both accelerated and inhibited biocatalytic properties in a biological context is intriguing to peruse more advanced functions of natural enzymes, but remains challenging, because most nanozymes are lack of enzyme-like molecular structures. By re-visiting and engineering the well-known Fe-N-C electrocatalyst that has a heme-like Fe-N_x active sites, herein, it is reported that Fe-N-C could not only catalyze drug metabolization but also had inhibition behaviors similar to cytochrome P450 (CYP), endowing it a potential replacement of CYP for preliminary evaluation of massive potential chemicals, drug dosing guide, and outcome prediction. In addition, in contrast to electrocatalysts, the highly graphitic framework of Fe-N-C may not be obligatory for a competitive CYP-like activity.

Rifampicin and rifapentine significantly reduce concentrations of bedaquiline, a new anti-TB drug

Objectives

Bedaquiline is the first drug of a new class approved for the treatment of TB in decades. Bedaquiline is metabolized by cytochrome P450 (CYP) 3A4 to a less-active M2 metabolite. Its terminal half-life is extremely long (5–6 months), complicating evaluations of drug–drug interactions. Rifampicin and rifapentine, two anti-TB drugs now being optimized to shorten TB treatment duration, are potent inducers of CYP3A4. This analysis aimed to predict the effect of repeated doses of rifampicin or rifapentine on the steady-state pharmacokinetics of bedaquiline and its M2 metabolite from single-dose data using a model-based approach.

Methods

Pharmacokinetic data for bedaquiline and M2 were obtained from a Phase I study involving 32 individuals each receiving two doses of bedaquiline, alone or together with multiple-dose rifampicin or rifapentine. Sampling was performed over 14 days following each bedaquiline dose. Pharmacokinetic analyses were performed using non-linear mixed-effects modelling. Models were used to simulate potential dose adjustments.

Results

Rifamycin co-administration increased bedaquiline clearance substantially: 4.78-fold [relative standard error (RSE) 9.10%] with rifampicin and 3.96-fold (RSE 5.00%) with rifapentine. Induction of M2 clearance was equally strong. Average steady-state concentrations of bedaquiline and M2 are predicted to decrease by 79% and 75% when given with rifampicin or rifapentine, respectively. Simulations indicated that increasing the bedaquiline dosage to mitigate the interaction would yield elevated M2 concentrations during the first treatment weeks.

Conclusions

Rifamycin antibiotics reduce bedaquiline concentrations substantially. In line with current treatment guidelines for drug-susceptible TB, concomitant use is not recommended, even with dose adjustment.

Importance of Hepatic Transporters in Clinical Disposition of Drugs and Their Metabolites

This review provides a practical clinical perspective on the relevance of hepatic transporters in pharmacokinetics and drug-drug interactions (DDIs). Special emphasis is placed on transporters with clear relevance to clinical DDIs, efficacy, and safety. Basolateral OATP1B1 and 1B3 emerged as important hepatic drug uptake pathways, sites for systemic DDIs, and sources of pharmacogenetic variability. As the first step in hepatic drug removal from the circulation, OATPs are an important determinant of systemic pharmacokinetics, specifically influencing systemic absorption, clearance, and hepatic distribution for subsequent metabolism and/or excretion. Biliary excretion of parent drugs is a less prevalent clearance pathway than metabolism or urinary excretion, but BCRP and MRP2 are critically important to biliary/fecal elimination of drug metabolites. Inhibition of biliary excretion is typically not apparent at the level of systemic pharmacokinetics but can markedly increase liver exposure. Basolateral efflux transporters MRP3 and MRP4 mediate excretion of parent drugs and, more commonly, polar metabolites from hepatocytes into blood. Basolateral excretion is an area in need of further clinical investigation, which will necessitate studies more complex than just systemic pharmacokinetics. Clinical relevance of hepatic uptake is relatively well appreciated, and clinical consequences of hepatic excretion (biliary and basolateral) modulation remain an active research area.

Validation of 4β-hydroxycholesterol and evaluation of other endogenous biomarkers for the assessment of CYP3A activity in healthy subjects

AIMS

This study aimed to assess changes in the plasma concentrationss of 4β-hydroxycholesterol (4βHC) against intravenous (i.v.) and oral midazolam (MDZ) pharmacokinetics (PK) after administration of a potent CYP3A inhibitor [ketoconazole (KETO)] and inducer [rifampicin (RIF)].

METHODS

Thirty-two healthy subjects (HS) were allocated into three groups of 12 each in KETO and RIF and 10 in a placebo group (PLB). All HS were randomized to receive oral and i.v. MDZ on day 1 or 2 and on day 15 or 16 after receiving RIF (600 mg once daily), KETO (400 mg once daily) or PLB for 2 weeks. Subjects were followed until day 30. The effect of treatments on 4βHC was assessed by analyzing % change from baseline using a linear spline mixed effects model.

RESULTS

Compared with PLB, KETO decreased 4βHC mean values up to 13% (P = 0.003) and RIF increased 4βHC mean values up to 220% (P < 0.001). Within 14 days of stopping KETO and RIF, 4βHC had either returned to baseline (KETO) or was still returning to baseline (RIF). Compared with baseline, mean oral MDZ AUC increased by 11-fold (90% CI ranging from 9-fold to 13-fold increase) and decreased by 92% (90% CI ranging from 90% to 95% decrease) after KETO and RIF, respectively. Similar trends were observed for 6β-hydroxycortisol : cortisol (6βHCL : CL) urinary ratios.

CONCLUSIONS

Changes in plasma 4βHC can be utilized as a surrogate for MDZ PK after multiple doses of potent CYP3A inducers. There is a more limited dynamic range for 4βHC for assessment of potential CYP3A inhibitors. 4βHC is a valuable tool for the assessment of potential CYP3A inducers in early drug development.

Select Drug-Drug Interactions With Direct Oral Anticoagulants: JACC Review Topic of the Week

Millions of individuals in the United States require long-term treatment with an oral anticoagulant. For decades, vitamin K antagonists were the only oral option available; however, they have a number of well-known limitations. Introduction of the direct oral anticoagulants (DOACs) has long been considered a major therapeutic advance, largely because they lack the need for therapeutic monitoring. Despite this, DOACs, like vitamin K antagonists, can still cause major and clinically relevant nonmajor bleeding, even when used appropriately. Drug-drug interactions (DDIs) involving the DOACs represent an important contributor to increased bleeding risk. Awareness of these DDIs and how best to address them is of critical importance in optimizing management while mitigating bleeding risk. This review provides an overview of DOAC metabolism, the most common drugs likely to contribute to DOAC DDIs, their underlying mechanisms, and how best to address them.

Drug-drug interactions between feminizing hormone therapy and pre-exposure prophylaxis among transgender women: the iFACT study

INTRODUCTION

Concerns over potential drug-drug interactions (DDI) between feminizing hormone therapy (FHT) and pre-exposure prophylaxis (PrEP) have hampered uptake and adherence of PrEP among transgender women (TGW). To determine DDI between FHT and PrEP, we measured the pharmacokinetic (PK) parameters of blood plasma estradiol (E2) and tenofovir (TFV) in Thai TGW.

METHODS

Twenty TGW who never underwent orchiectomy and had not received injectable FHT within six months were enrolled between January and March 2018. FHT (E2 valerate and cyproterone acetate) were prescribed to participants at baseline until week 5, and then from week 8 until the end of study. Daily PrEP (tenofovir disoproxil fumarate/emtricitabine) was initiated at week 3 and continued without interruption. Intensive E2 PK parameters and testosterone concentration at 24 hours (C24 ) were measured at weeks 3 (without PrEP) and 5 (with PrEP), and intensive TFV PK parameters were measured at weeks 5 (with FHT) and 8 (without FHT).

RESULTS

Median (interquartile range) age, body mass index, and creatinine clearance were 21.5 (21-26) years, 20.6 (19.0-22.4) kg/m2 , and 116 (101-126.5) mL/min, respectively. The geometric mean (%CV) of area under curve from time zero to 24 hours (AUC0-24 ), maximum concentration (Cmax ), and C24 of E2 at weeks 3 and 5 were 775.13 (26.2) pg h/mL, 51.47 (26.9) pg/mL, and 15.15 (42.0) pg/mL; and 782.84 (39.6), 55.76 (32.9), and 14.32 (67.4), respectively. The geometric mean (%CV) of TFV AUC0-24 , Cmax , and C24 at weeks 5 and 8 were 2242.1 (26.5) ng h/mL, 353.9 (34.0) ng/mL, and 40.9 (31.4) ng/mL; and 2530.2 (31.3), 311.4 (30.0), and 49.8 (29.6), respectively. The geometric mean of TFV AUC0-24 and C24 at week 5 were significantly less than that at week 8 by 12% (p = 0.03) and 18% (p < 0.001), respectively. There were no significant changes in E2 PK parameters and median C24 of bioavailable testosterone between week 3 and week 5.

CONCLUSIONS

Our study demonstrated lower blood plasma TFV exposure in the presence of FHT, suggesting that FHT may potentially affect PrEP efficacy among TGW; but E2 exposure was not affected by PrEP. Further studies are warranted to determine whether these reductions in TFV are clinically significant. Clinical Trial Number: NCT03620734.

Psychopharmacology and Cardiovascular Disease

This review discusses common mental health disorders and their associations with cardiovascular disease risks. Commonly found mental health disorders include depression, anxiety, and personality types. The link between depression and cardiovascular disease mortality has been established. Depression is also common in patients with heart failure. In addition to discussing psychological disorders, a review of psychotropic drugs is also included. Drugs are described for therapy for depression and anxiety, as well as associations with cardiovascular drug-drug interactions. Drug-drug interactions are more common and potentially dangerous in elderly patients, in whom the conditions often coexist. The most common drug-drug interactions involve the P450 system of enzymes.

Polypharmacy in patients with advanced cancer and pain: a European cross-sectional study of 2282 patients

CONTEXT

Patients with advanced cancer need multiple drugs to control symptoms and to treat cancer and concomitant diseases. At the same time, the goal of treatment changes as life expectancy becomes limited. This results in a risk for polypharmacy, maintained use of unneeded drugs, and drug-drug interactions (DDIs).

OBJECTIVES

The aim of the study was to analyze the use of medications and to identify unneeded drugs, and drugs and drug combinations with a risk for DDIs in a cohort of advanced cancer pain patients, defined by a need for a World Health Organization analgesic ladder Step III opioid.

METHODS

All drugs taken within a study day by cancer patients receiving opioids for moderate or severe pain (Step III opioids) were analyzed. Nonopioids and adjuvants were analyzed for their use across countries. Unneeded medications and drugs and drug combinations with a risk for pharmacodynamic and pharmacokinetic DDIs were identified on the basis of published literature and electronic resources.

RESULTS

In total, 2282 patients from 17 centers in 11 European countries were included. They received a mean of 7.8 drugs (range 1-20). Over one-quarter used 10 or more medications. The drugs and drug classes most frequently coadministered with opioids were proton pump inhibitors, laxatives, corticosteroids, paracetamol (acetaminophen), nonsteroidal anti-inflammatory drugs, metoclopramide, benzodiazepines, anticoagulants, antibiotics, anticonvulsants, diuretics, and antidepressants. The use of nonopioids and essential adjuvants varied across countries. Approximately 45% of patients received unnecessary or potentially unnecessary drugs, and about 7% were given duplicate or antagonizing agents. Exposures to DDIs were frequent and increased the risk of sedation, gastric ulcerations, bleedings, and neuropsychiatric and cardiac complications. Many patients were exposed to pharmacokinetic DDIs involving cytochrome P450, including about 58% who used a Step III opioid CYP3A4 (izoenzyme of cytochrome P450) substrate, and more than 10% who were given major CYP3A4 inhibitors or inducers.

CONCLUSION

Patients with cancer treated with a World Health Organization Step III opioid use a high number of drugs. Nonopioid analgesics and corticosteroids are frequently used, but different patterns of use between countries were found. Many patients receive unneeded drugs and are at risk of serious DDIs. These findings demonstrate that drug therapy in these patients needs to be evaluated continuously.

Anti-infectives and the risk of severe hypoglycemia in users of glipizide or glyburide

The objective of this study was to evaluate whether orally administered anti-infectives increase the risk of severe hypoglycemia in users of glipizide or glyburide. We performed two case-control studies and two case-crossover studies using US Medicaid data. All the anti-infectives examined were associated with an elevated risk of severe hypoglycemia. Using cephalexin as the reference category, in glipizide users, statistically significant associations were found with co-trimoxazole (odds ratio (OR) = 3.14; 95% confidence interval (CI): 1.83-5.37); clarithromycin (OR = 2.90; 95% CI: 1.69-4.98); fluconazole (OR = 2.53; 95% CI: 1.23-5.23); and levofloxacin (OR = 2.09; 95% CI: 1.35-3.25). In glyburide users, with cephalexin as the reference, statistically significant associations were found with clarithromycin (OR = 5.02; 95% CI: 3.35-7.54); levofloxacin (OR = 2.83; 95% CI: 1.73-4.62); co-trimoxazole (OR = 2.68; 95% CI: 1.59-4.52); fluconazole (OR = 2.20; 95% CI: 1.04-4.68); and ciprofloxacin (OR = 2.08; 95% CI: 1.23-3.52). In conclusion, exposure to all studied anti-infective agents were associated with subsequent severe hypoglycemia. Using cephalexin as the reference, drug-drug interactions were evident with ciprofloxacin (in glyburide users only), clarithromycin, co-trimoxazole, fluconazole, and levofloxacin.

Major revision version 11.0 of the European AIDS Clinical Society Guidelines 2021

BACKGROUND

The European AIDS Clinical Society (EACS) Guidelines were revised in 2021 for the 17th time with updates on all aspects of HIV care.

KEY POINTS OF THE GUIDELINES UPDATE

Version 11.0 of the Guidelines recommend six first-line treatment options for antiretroviral treatment (ART)-naïve adults: tenofovir-based backbone plus an unboosted integrase inhibitor or plus doravirine; abacavir/lamivudine plus dolutegravir; or dual therapy with lamivudine or emtricitabine plus dolutegravir. Recommendations on preferred and alternative first-line combinations from birth to adolescence were included in the new paediatric section made with Penta. Long-acting cabotegravir plus rilpivirine was included as a switch option and, along with fostemsavir, was added to all drug-drug interaction (DDI) tables. Four new DDI tables for anti-tuberculosis drugs, anxiolytics, hormone replacement therapy and COVID-19 therapies were introduced, as well as guidance on screening and management of anxiety disorders, transgender health, sexual health for women and menopause. The sections on frailty, obesity and cancer were expanded, and recommendations for the management of people with diabetes and cardiovascular disease risk were revised extensively. Treatment of recently acquired hepatitis C is recommended with ongoing risk behaviour to reduce transmission. Bulevirtide was included as a treatment option for the hepatitis Delta virus. Drug-resistant tuberculosis guidance was adjusted in accordance with the 2020 World Health Organization recommendations. Finally, there is new guidance on COVID-19 management with a focus on continuance of HIV care.

CONCLUSIONS

In 2021, the EACS Guidelines were updated extensively and broadened to include new sections. The recommendations are available as a free app, in interactive web format and as an online pdf.

Differential Regulation of CYP3A4 and CYP3A5 and its Implication in Drug Discovery

BACKGROUND

Cancer cells use several mechanisms to resist the cytotoxic effects of drugs, resulting in tumor progression and invasion. One such mechanism capitalizes on the body's natural defense against xenobiotics by increasing the rate of xenobiotic efflux and metabolic inactivation. Xenobiotic metabolism typically involves conversion of parent molecules to more soluble and easily excreted derivatives in reactions catalyzed by Phase I and Phase II drug metabolizing enzymes.

METHODS

We performed a structured search of peer-reviewed literature on P450 (CYP) 3A, with a focus on CYP3A4 and CYP3A5.

RESULTS

Recent reports indicate that components of the xenobiotic response system are upregulated in some diseases, including many cancers. Such components include the pregnane X receptor (PXR), CYP3A4 and CYP3A5 enzymes. The CYP3A enzymes are a subset of the numerous enzymes that are transcriptionally activated following the interaction of PXR and many ligands.

CONCLUSION

Intense research is ongoing to understand the functional ramifications of aberrant expression of these components in diseased states with the goal of designing novel drugs that can selectively target them.