Influence of chronic hepatitis C infection on cytochrome P450 3A4 activity using midazolam as an in vivo probe substrate

Population toxicokinetics of carbamazepine and its metabolite carbamazepine-10,11-epoxide in adults

BACKGROUND

Carbamazepine is one of the most commonly used antiseizure medications. Although carbamazepine pharmacokinetics in epileptic patients is well described, much less is known about these processes in the patients who experienced self-poisoning episode by this drug. Therefore, the aim of our investigation was to perform population toxicokinetics of carbamazepine and its metabolite carbamazepine-10,11-epoxide in adults.

RESEARCH DESIGN AND METHODS

Software program NONMEM and the ADVAN2 TRANS2 subroutine were used for establishing a population toxicokinetic model for the estimation of clearance and volume of distribution based on of the sum values of carbamazepine and carbamazepine-10,11-epoxide concentrations.

RESULTS

Our results indicated that the adult patients' ability to eliminate carbamazepine and carbamazepine-10,11-epoxide following acute carbamazepine self-poisoning was strongly associated with the high levels of CRP and ASP, as well as by the treatment with sedation.

CONCLUSIONS

Our study should provide better understanding of the toxicokinetics of carbamazepine taken in overdose and better management of patient population admitted to hospital.

Oxysterols as Biomarkers of Aging and Disease

Oxysterols derive from either enzymatic or non-enzymatic oxidation of cholesterol. Even though they are produced as intermediates of bile acid synthesis pathway, they are recognised as bioactive compounds in cellular processes. Therefore, their absence or accumulation have been shown to be associated with disease phenotypes. This chapter discusses the contribution of oxysterol to ageing, age-related diseases such as neurodegeneration and various disorders such as cancer, cardiovascular disease, diabetes, metabolic and ocular disorders. It is clear that oxysterols play a significant role in development and progression of these diseases. As a result, oxysterols are being investigated as suitable markers for disease diagnosis purposes and some drug targets are in development targeting oxysterol pathways. However, further research will be needed to confirm the suitability of these potentials.

Comparison and summary of in silico prediction tools for CYP450-mediated drug metabolism

The cytochrome P450 (CYP450) enzyme system is responsible for the metabolism of more than two-thirds of xenobiotics. This review summarizes reports of a series of in silico tools for CYP450 enzyme-drug interaction predictions, including the prediction of sites of metabolism (SOM) of a drug and the identification of inhibitor/substrates for CYP subtypes. We also evaluated four prediction tools to identify CYP inhibitors utilizing 52 of the most frequently prescribed drugs. ADMET Predictor and CYPlebrity demonstrated the best performance. We hope that this review provides guidance for choosing appropriate enzyme prediction tools from a variety of in silico platforms to meet individual needs. Such predictions are useful for medicinal chemists to prioritize their designed compounds for further drug discovery.

Idiopathic pulmonary fibrosis therapy development: a clinical pharmacology perspective

Drug development for idiopathic pulmonary fibrosis (IPF) has been challenging due to poorly understood disease etiology, unpredictable disease progression, highly heterogeneous patient populations, and a lack of robust pharmacodynamic biomarkers. Moreover, because lung biopsy is invasive and dangerous, making the extent of fibrosis as a direct longitudinal measurement of IPF disease progression unfeasible, most clinical trials studying IPF can only assess progression of fibrosis indirectly through surrogate measures. This review discusses current state-of-art practices, identifies knowledge gaps, and brainstorms development opportunities for preclinical to clinical translation, clinical populations, pharmacodynamic endpoints, and dose optimization strategies. This article highlights clinical pharmacology perspectives in leveraging real-world data as well as modeling and simulation, special population considerations, and patient-centric approaches for designing future studies.

Pre-procedural Preparation and Sedation for Gastrointestinal Endoscopy in Patients with Advanced Liver Disease

Gastrointestinal endoscopy in patients with advanced liver disease poses various challenges, a major one being procedural sedation and its associated considerations. While sedation during endoscopy can improve patient comfort, decrease anxiety, and facilitate procedural completion, in patients with advanced liver disease, it is also associated with substantial and unique risks due to alterations in drug metabolism and other factors. As such, the choice of sedative agent(s) and related logistics may require careful inter-disciplinary planning and individualized considerations. Furthermore, a large proportion of agents require dose reductions and particular monitoring of the vital signs, level of consciousness, and other indices. In the present review, we provide a contemporary overview of procedural sedation considerations, commonly used intravenous sedatives, and second-line as well as novel sedatives for gastrointestinal endoscopy in patients with advanced liver disease.

Benign course of residual inflammation at end of treatment of liver transplant recipients after sofosbuvir based therapy

BACKGROUND

Persistent inflammation on histology after successful hepatitis C (HCV) treatment has been reported. However, data regarding the long-term impact in liver transplant recipients is limited, particularly after using direct-acting antiviral (DAA) therapies.

AIM

To evaluate the impact of successful treatment with DAAs on histological changes and occult HCV and to describe the clinical course of residual inflammation in liver transplant recipients.

METHODS

We conducted a case series of 13 chronic HCV infected liver transplant recipients successfully treated with DAAs between December 2013 and May 2014. All patients were treated for 24 wk and had non-detectable serum HCV RNA by the time of biopsy. Only patients with at least one liver biopsy at or after treatment were included. We examined liver biopsies for evidence of residual inflammation and the presence of intrahepatic HCV RNA.

RESULTS

Persistent inflammation was seen in 12/13 patients on end of treatment biopsy. Inflammation was still seen in the available five follow-up biopsies (range 38-48 wk after the end of treatment). Intrahepatic HCV RNA was undetectable in all biopsies. All patients had preserved graft function for a mean follow-up of 2.5 years, except one that developed chronic rejection.

CONCLUSION

After successful HCV treatment with DAAs, liver transplant recipients may have persistent inflammation on biopsy without evidence of intracellular RNA. The clinical outcome remained favorable in most patients. Further studies with a larger number and longer follow-up are needed to establish the implication of this finding on long-term graft function.

Influence of Inflammation on Cytochromes P450 Activity in Adults: A Systematic Review of the Literature

Background: Available in-vitro and animal studies indicate that inflammation impacts cytochromes P450 (CYP) activity via multiple and complex transcriptional and post-transcriptional mechanisms, depending on the specific CYP isoforms and the nature of inflammation mediators. It is essential to review the current published data on the impact of inflammation on CYP activities in adults to support drug individualization based on comorbidities and diseases in clinical practice. Methods: This systematic review was conducted in PubMed through 7th January 2021 looking for articles that investigated the consequences of inflammation on CYP activities in adults. Information on the source of inflammation, victim drugs (and CYPs involved), effect of disease-drug interaction, number of subjects, and study design were extracted. Results: The search strategy identified 218 studies and case reports that met our inclusion criteria. These articles were divided into fourteen different sources of inflammation (such as infection, autoimmune diseases, cancer, therapies with immunomodulator…). The impact of inflammation on CYP activities appeared to be isoform-specific and dependent on the nature and severity of the underlying disease causing the inflammation. Some of these drug-disease interactions had a significant influence on drug pharmacokinetic parameters and on clinical management. For example, clozapine levels doubled with signs of toxicity during infections and the concentration ratio between clopidogrel's active metabolite and clopidogrel is 48-fold lower in critically ill patients. Infection and CYP3A were the most cited perpetrator of inflammation and the most studied CYP, respectively. Moreover, some data suggest that resolution of inflammation results in a return to baseline CYP activities. Conclusion: Convincing evidence shows that inflammation is a major factor to be taken into account in drug development and in clinical practice to avoid any efficacy or safety issues because inflammation modulates CYP activities and thus drug pharmacokinetics. The impact is different depending on the CYP isoform and the inflammatory disease considered. Moreover, resolution of inflammation appears to result in a normalization of CYP activity. However, some results are still equivocal and further investigations are thus needed.

Clinical and Molecular Perspectives on Inflammation-Mediated Regulation of Drug Metabolism and Transport

Inflammation is a possible cause of variability in drug response and toxicity due to altered regulation in drug-metabolizing enzymes and transporters (DMETs) in humans. Here, we evaluate the clinical and in vitro evidence on inflammation-mediated modulation of DMETs, and the impact on drug metabolism in humans. Furthermore, we identify and discuss the gaps in our current knowledge. A systematic literature search on PubMed, Embase, and grey literature was performed in the period of February to September 2020. A total of 203 papers was included. In vitro studies in primary human hepatocytes revealed strong evidence that CYP3A4 is strongly downregulated by inflammatory cytokines IL-6 and IL-1β. CYP1A2, CYP2C9, CYP2C19, and CYP2D6 were downregulated to a lesser extent. In clinical studies, acute and chronic inflammatory diseases were observed to cause downregulation of CYP enzymes in a similar pattern. However, there is no clear correlation between in vitro studies and clinical studies, mainly because most in vitro studies use supraphysiological cytokine doses. Moreover, clinical studies demonstrate considerable variability in terms of methodology and inconsistencies in evaluation of the inflammatory state. In conclusion, we find inflammation and pro-inflammatory cytokines to be important factors in regulation of drug-metabolizing enzymes and transporters. The observed downregulation is clinically relevant, and we emphasize caution when treating patients in an inflammatory state with narrow therapeutic index drugs. Further research is needed to identify the full extent of inflammation-mediated changes in DMETs and to further support personalized medicine.

A Broad Range High-Throughput Assay for Lenvatinib Using Ultra-High Performance Liquid Chromatography Coupled to Tandem Mass Spectrometry With Clinical Application in Patients With Hepatocellular Carcinoma

BACKGROUND

Lenvatinib is increasingly being selected as the first-line treatment for unresectable hepatocellular carcinoma (HCC) based on the results of the REFLECT trial. However, early discontinuation of lenvatinib because of adverse effects is a frequent occurrence. Hence, lenvatinib is a difficult drug for use in the clinical setting. One of the causes is that the dose of lenvatinib is mainly determined by body weight alone, despite high interindividual variability. To overcome this problem, a dosing regimen of lenvatinib based on a population pharmacokinetic (PPK) model for HCC patients is proposed. The aim of this study was to develop a high-throughput quantification method for lenvatinib using ultra-high performance liquid chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS) that can be applied to a PPK analysis of HCC patients in the future.

METHODS

After a simple solid-phase extraction step using a 96-well plate, lenvatinib was analyzed by UHPLC-MS/MS in a positive electrospray ionization mode.

RESULTS

The novel method fulfilled the requirements of the US Food and Drug Administration guidance on bioanalytical method validation. The calibration curve was linear over the 0.2-1000 ng/mL concentration range. The average recovery rate was 98.63 ± 4.55% (mean ± SD). The precision was below 6.05%, and the accuracy was within 12.96% for all quality control levels. The matrix effect varied between 103.33% and 134.61%. This assay was successfully applied to the measurement of plasma concentrations in 6 HCC patients receiving lenvatinib.

CONCLUSIONS

A novel high-throughput UHPLC-MS/MS assay for quantification of lenvatinib in human plasma was successfully developed. This method can be applied to PPK analysis for patients receiving lenvatinib in the clinical setting.

Inflammation Induces Changes in the Functional Expression of P-gp, BCRP, and MRP2: An Overview of Different Models and Consequences for Drug Disposition

The ATP-binding cassette (ABC) transporters play a key role in drug pharmacokinetics. These membrane transporters expressed within physiological barriers can be a source of pharmacokinetic variability. Changes in ABC transporter expression and functionality may consequently affect the disposition of substrate drugs, resulting in different drug exposure. Inflammation, present in several acute and chronic diseases, has been identified as a source of modulation in drug transporter expression leading to variability in drug response. Its regulation may be particularly dangerous for drugs with a narrow therapeutic index. In this context, numerous in vitro and in vivo models have shown up- or downregulation in the expression and functionality of ABC transporters under inflammatory conditions. Nevertheless, the existence of contradictory data and the lack of standardization for the models used have led to a less conclusive interpretation of these data.

Clinical treatment for hepatitis C reverses CYP2C19 inhibition

AIMS

Infection by the hepatitis C virus (HCV) generates inflammatory response selectively modulating cytochrome P450 protein (CYP) activities. This study assessed the effect of chronic hepatitis C on CYP2C19 activity in patients with HCV.

METHODS

Patients with HCV infection (n = 23) at different fibrosis stages were allocated into groups 1 (F0/F1 and F2, mild to moderate fibrosis) and 2 (F3 and F4, advanced fibrosis stages). Phase 1 was conducted before the treatment with direct-acting antivirals (DAAs) and phase 2 after the sustained virological response. Participants were administered 2 mg of a single oral dose of omeprazole (OME) as probe drug in both phases. Metabolic ratios (MRs) (plasma samples collected at 4 h after OME administration) were calculated by dividing plasma concentrations of 5-hydroxyomeprazole by OME.

RESULTS

The MRs for group 1 were 0.45 (0.34-0.60, 90% confidence interval) and 0.69 (0.50-0.96) for phases 1 and 2, respectively, while the MRs for group 2 were 0.25 (0.21-0.31) and 0.41 (0.30-0.56) for phases 1 and 2, respectively. MRs were different (P < .05) between phases 1 and 2 for both groups, as well as between groups 1 and 2 in phase 1, but not in phase 2 (P > .05).

CONCLUSIONS

Both groups presented different MRs before and after treatment with DAAs, evidencing that CYP2C19 inhibition during inflammation was at least partially reversed after DAA treatment. Groups 1 and 2 were also found to be different in phase 1 but not phase 2, showing that CYP2C19 metabolic activity does not differ between groups after DAA treatment.

Impact of Acute Inflammation on Cytochromes P450 Activity Assessed by the Geneva Cocktail

Cytochromes P450 (CYP) are subject to important interindividual variability in their activity due to genetic and environmental factors and some diseases. Limited human data support the idea that inflammation downregulates CYP activities. Our study aimed to evaluate the impact of orthopedic surgery (acute inflammation model) on the activity of six human CYP. This prospective observational study was conducted in 30 patients who underwent elective hip surgery at the Geneva University Hospitals in Switzerland. The Geneva phenotyping cocktail containing caffeine, bupropion, flurbiprofen, omeprazole, dextromethorphan, and midazolam as probe drugs respectively assessing CYP1A2, 2B6, 2C9, 2C19, 2D6, and 3A activities was administered orally before surgery, day 1 (D1) and 3 (D3) postsurgery and at discharge. Capillary blood samples were collected 2 hours after cocktail intake to assess metabolic ratios (MRs). Serum inflammatory markers (CRP, IL‐6, IL‐1β, TNF‐α, and IFN‐γ) were also measured in blood. CYP1A2 MRs decreased by 53% (P < 0.0001) between baseline and the nadir at D1. CYP2C19 and CYP3A activities (MRs) decreased by 57% (P = 0.0002) and 61% (P < 0.0001), respectively, with the nadir at D3. CYP2B6 and CYP2C9 MRs increased by 120% (P < 0.0001) and 79% (P = 0.018), respectively, and peaked at D1. Surgery did not have a significant impact on CYP2D6 MR. Hip surgery was a good acute inflammation model as CRP, IL‐6, and TNF‐α peak levels were reached between D1 and day 2 (D2). Acute inflammation modulated CYP activity in an isoform‐specific manner, with different magnitudes and kinetics. Acute inflammation may thus have a clinically relevant impact on the pharmacokinetics of these CYP substrates.

Inflammation is a major regulator of drug metabolizing enzymes and transporters: Consequences for the personalization of drug treatment

Inflammation is an evolutionary process that allows survival against acute infection or injury. Inflammation is also a pathophysiological condition shared by numerous chronic diseases. In addition, inflammation modulates important drug-metabolizing enzymes and transporters (DMETs), thus contributing to intra- and interindividual variability of drug exposure. A better knowledge of the impact of inflammation on drug metabolism and its related clinical consequences would help to personalize drug treatment. Here, we summarize the kinetics of inflammatory mediators and the underlying transcriptional and post-transcriptional mechanisms by which they contribute to the inhibition of important DMETs. We also present an updated overview of the effect of inflammation on the pharmacokinetic parameters of most of the drugs that are DMET substrates, for which therapeutic drug monitoring is recommended. Furthermore, we provide opinions on how to integrate the inflammatory status into pharmacogenetics, therapeutic drug monitoring, and population pharmacokinetic strategies to improve the personalization of drug treatment for each patient.

Cytochrome P450-mediated drug interactions in COVID-19 patients: Current findings and possible mechanisms

At the end of 2019, the entire world has witnessed the birth of a new member of coronavirus family in Wuhan, China. Ever since, the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) has swiftly invaded every corner on the planet. By the end of April 2020, almost 3.5 million cases have been reported worldwide, with a death toll of about 250,000 deaths. It is currently well-recognized that patient’s immune response plays a pivotal role in the pathogenesis of Coronavirus Disease 2019 (COVID-19). This inflammatory element was evidenced by its elevated mediators that, in severe cases, reach their peak in a cytokine storm. Together with the reported markers of liver injury, such hyperinflammatory state may trigger significant derangements in hepatic cytochrome P450 metabolic machinery, and subsequent modulation of drug clearance that may result in unexpected therapeutic/toxic response. We hypothesize that COVID-19 patients are potentially vulnerable to a significant disease-drug interaction, and therefore, suitable dosing guidelines with therapeutic drug monitoring should be implemented to assure optimal clinical outcomes.

Raltegravir pharmacokinetics before and during treatment with ombitasvir, paritaprevir/ritonavir plus dasabuvir in adults with human immunodeficiency virus-1 and hepatitis C virus coinfection: AIDS Clinical Trials Group sub-study A5334s

AIMS

AIDS Clinical Trials Group study A5334s evaluated the pharmacokinetics of raltegravir before and during combined administration of ombitasvir, paritaprevir/ritonavir, plus dasabuvir (OBV/PTV/r + DSV) and weight-based ribavirin in human immunodeficiency virus (HIV) and hepatitis C virus (HCV) coinfected adults. The pharmacokinetics of OBV/PTV/r + DSV during raltegravir coadministration were also characterized.

METHODS

Adults living with HIV/HCV coinfection receiving steady-state raltegravir (400 mg twice daily) with 2 nucleos(t)ide analogues were enrolled. Pharmacokinetics of raltegravir were assessed prior to HCV therapy, and 4 weeks later following initiation of OBV/PTV/r (25/150/100 mg) once daily + DSV (250 mg) twice daily. Geometric mean ratios (GMRs) and 90% confidence intervals (CIs) were used to compare the following: raltegravir pharmacokinetics with HCV therapy (week 4) vs before HCV therapy (week 0); OBV/PTV/r and DSV pharmacokinetics vs historical healthy controls; raltegravir pharmacokinetics at week 0 vs historical control adults living with HIV.

RESULTS

Eight of 11 participants had decreased raltegravir exposures after initiation of HCV therapy. The GMRs (90% CI) for maximum concentration and area under the concentration-time curve of raltegravir with vs without HCV therapy were 0.68 (0.38-1.19) and 0.82 (0.58-1.17), respectively. Comparing OBV/PTV/r pharmacokinetics in healthy controls, A5334s study participants demonstrated generally lower maximum concentration and area under the concentration-time curve values by 41-82% and 4-73%, respectively. Raltegravir exposures tended to be higher in A5334s study participants compared to adults living with HIV.

CONCLUSIONS

The majority of participants' plasma raltegravir exposures were lower after initiation of HCV therapy in coinfected adults; however, confidence intervals were wide.

Review article: clinical pharmacology of current and investigational hepatitis B virus therapies

BACKGROUND

Treatment of hepatitis B virus (HBV) infection with current therapy suppresses HBV DNA, but loss of hepatitis B surface antigen (HBsAg; functional cure), is rare. Multiple compounds are under investigation.

AIMS

To describe the pharmacology, including drug interactions, efficacy, safety and mechanisms of action of investigational compounds for HBV infection.

METHODS

Descriptive review using PubMed and Google to identify literature/conference papers on investigational compounds (≥Phase 2) with data on efficacy and safety in HBV-infected patients.

RESULTS

Bulevirtide, JNJ-56136379, ABI-H0731, REP-2139, and inarigivir decrease HBV DNA/RNA, with greater potency than current nucleos(t)ide analogues. REP-2139 (25%-75% of patients, 20-48 weeks treatment) and inarigivir (26% of patients, 12-24 weeks treatment) induce HBsAg loss. ARO-HBV reduced (>1.5 log₁₀ UI/mL) HBsAg in 85% of patients (12 weeks treatment). There are some safety concerns with investigational agents (e.g., increased bile acids with bulevirtide, and liver enzyme flares with REP-2139) which will require a risk benefit assessment compared with current therapies. Single and multidose pharmacokinetic data are available for bulevirtide, JNJ-56136379, ABI-H0731; no such data are available for REP-2139, ARO-HBV, inarigivir. Initial drug interaction assessments have been performed with bulevirtide and inarigivir (only in vitro).

CONCLUSIONS

There are promising investigational therapies for HBV infection. Increasing the potential for HBsAg loss may result in more patients achieving functional cure. However, many knowledge gaps remain such as pharmacokinetics in those with HBV, cirrhosis and renal impairment but also the interaction potential between investigational therapies, risk-benefit profiles, and potential for drug interactions with medications used to treat comorbidities associated with aging.

Effects of Sofosbuvir-Based Hepatitis C Treatment Regimens on Calcineurin Inhibitor Dosing in Liver and Kidney Transplant Recipients

OBJECTIVES

Available data have suggested that directacting antivirals for hepatitis C virus may decrease calcineurin inhibitor concentrations. In this study, our aim was to determine the effects of hepatitis C directacting antivirals on calcineurin inhibitor doses and trough levels.

MATERIALS AND METHODS

This retrospective, singlecenter study included 52 abdominal transplant recipients treated with sofosbuvir-based regimens between 2014 and 2017. The primary outcome was percent change in calcineurin inhibitor troughs and total daily doses between the week before treatment with direct-acting antivirals, days 21 to 35 oftreatment, and days 21 to 35 aftertreatment. Secondary outcomes included sustained virologic response and biopsyproven acute rejection rates.

RESULTS

The median percent difference in calcineurin inhibitor troughs from pretreatment to during treatment was -20.5% (interquartile range, -36.2% to 13.1%) and from pretreatment to posttreatment was -13.5% (interquartile range, -33.7% to 10.7%). Corresponding percent changes in calcineurin inhibitor doses were 0% (interquartile range, 0%-0%) and 0% (interquartile range, -10.5% to 33.3%), respectively. Patients on tacrolimus experienced statistically significant changes in troughs but not doses. During treatment, 65% of patients required no dose change, 23% underwent a dose increase, and 12% had a dose decrease. The sustained virologic response rate was 98%, and the biopsy-proven acute rejection rate was 0%.

CONCLUSIONS

Hepatitis C direct-acting antiviraltherapy may decrease calcineurin inhibitor levels, but this was not associated with clinically different dosing requirements or rejection rates.

A Pharmacology Perspective of Simultaneous Tuberculosis and Hepatitis C Treatment

Tuberculosis (TB) and hepatitis C virus (HCV) infection are both major public health problems. Despite high rates of co-infection there is scarce literature addressing the convergence of the two diseases. One particularly unexplored area is the potential for simultaneous treatment of TB and HCV which would allow for leveraging an extensive global TB treatment infrastructure to help scale up HCV treatment. We review the drug metabolism of anti-TB and HCV drugs and the known and potential drug-drug interactions between recommended HCV regimens and individual anti-TB drugs. Rifampin is the only anti-TB drug to have been formally studied for potential drug interactions with anti-HCV direct-acting antivirals (DAAs) and existing data precludes these combinations. However, based on known pathways of drug metabolism and enzyme effects, the combination of HCV DAA regimens with all other anti-TB drugs may be feasible. Pharmacokinetic studies are needed next to help move co treatment regimens forward for clinical use among patients coinfected with TB and HCV.

Single nucleotide polymorphisms associated with elevated alanine aminotransferase in patients receiving asunaprevir plus daclatasvir combination therapy for chronic hepatitis C

Aims

Drug-induced liver damage characterized by serum alanine aminotransferase (ALT) elevation often occurs in direct-acting antiviral (DAA) combination therapy for chronic hepatitis C virus (HCV) infection. This study explored single nucleotide polymorphisms (SNPs) at drug metabolism- or transport-related genes that were associated with ALT elevation in asunaprevir plus daclatasvir therapy.

Methods

Subjects were 185 Japanese patients with chronic HCV genotype 1b infection who received asunaprevir plus daclatasvir therapy. Tag SNPs at possible metabolizing enzyme and transporter genes, which were involved in the pharmacokinetics of asunaprevir and daclatasvir, were selected.

Results

Among the tag SNPs analyzed, CYP3A4 rs4646437 was significantly associated with ALT elevation (p = 0.013): maximum ALT values in patients with genotype CC were higher than those in patients with genotype non-CC (allele T). The proportion of grades 2–4 in genotype CC patients were significantly greater than those in genotype non-CC patients (p = 0.028). No patients with genotype non-CC showed grade ≥2 ALT elevation. In multivariate analysis, rs4646437 genotype CC and cirrhosis were significant, independent factors associated with grade ≥1 ALT elevation (odds ratio, 2.83 and 1.88; p = 0.040 and 0.045, respectively). In exploratory analyses, although serum concentrations of asunaprevir and daclatasvir were not correlated with maximum ALT values or rs4646437 genotypes, asunaprevir concentrations in patients with grade ≥1 ALT elevation were significantly higher than those in patients with grade <1 ALT elevation (P = 0.023).

Conclusions

CYP3A4 rs4646437 was found to be significantly and independently associated with ALT elevation in Japanese patients receiving ASV plus DCV therapy. Notably, none of the patients with rs4646437 genotype non-CC (allele T) had grade ≥2 ALT elevation. SNP genotyping prior to treatment might be useful for carefully monitoring patients to complete treatment safely.

Impact of direct-acting antivirals for hepatitis C virus therapy on tacrolimus dosing in liver transplant recipients

INTRODUCTION

Direct-acting antivirals (DAAs) have transformed hepatitis C virus (HCV) management post-liver transplant. As HCV clears during DAA treatment, hepatic metabolism improves, resulting in decreased tacrolimus concentrations that may require dose adjustment. The purpose of this study was to determine appropriate management of immunosuppression in liver transplant recipients during and following treatment of HCV.

METHODS

This study was a single-center retrospective analysis of 71 liver transplant recipients who were treated for HCV with DAAs. The primary outcome was change in dose-normalized tacrolimus concentrations from the start of DAA treatment to 12 weeks following therapy.

RESULTS

The mean change in log-transformed dose-normalized tacrolimus concentrations was a reduction of 0.43 ng/mL/mg (95% CI; 0.26-0.60, P < 0.0001). The greatest decrease occurred in the first 4 weeks of treatment, after which levels stabilized. The overall mean tacrolimus concentration was 4.8 ng/mL (±2.5). Two patients (3%) developed acute cellular rejection and two patients (3%) had graft loss and died.

CONCLUSION

From the start of treatment to 12 weeks post-DAA therapy, liver transplant recipients experienced a significant decrease in dose-normalized tacrolimus concentrations. In conclusion, close monitoring of tacrolimus concentrations is warranted during and following treatment with DAAs, as dose increases may be indicated in order to maintain therapeutic concentrations to prevent graft rejection.

Oxysterols and Gastrointestinal Cancers Around the Clock

This review focuses on the role of oxidized sterols in three major gastrointestinal cancers (hepatocellular carcinoma, pancreatic, and colon cancer) and how the circadian clock affects the carcinogenesis by regulating the lipid metabolism and beyond. While each field of research (cancer, oxysterols, and circadian clock) is well-studied within their specialty, little is known about the intertwining mechanisms and how these influence the disease etiology in each cancer type. Oxysterols are involved in pathology of these cancers, but final conclusions about their protective or damaging effects are elusive, since the effect depends on the type of oxysterol, concentration, and the cell type. Oxysterol concentrations, the expression of key regulators liver X receptors (LXR), farnesoid X receptor (FXR), and oxysterol-binding proteins (OSBP) family are modulated in tumors and plasma of cancer patients, exposing these proteins and selected oxysterols as new potential biomarkers and drug targets. Evidence about how cholesterol/oxysterol pathways are intertwined with circadian clock is building. Identified key contact points are different forms of retinoic acid receptor related orphan receptors (ROR) and LXRs. RORs and LXRs are both regulated by sterols/oxysterols and the circadian clock and in return also regulate the same pathways, representing a complex interplay between sterol metabolism and the clock. With this in mind, in addition to classical therapies to modulate cholesterol in gastrointestinal cancers, such as the statin therapy, the time is ripe also for therapies where time and duration of the drug application is taken as an important factor for successful therapies. The final goal is the personalized approach with chronotherapy for disease management and treatment in order to increase the positive drug effects.

Impact of anti-HCV direct antiviral agents on graft function and immunosuppressive drug levels in kidney transplant recipients: a call to attention in the mid-term follow-up in a single-center cohort study

The medium-term impact on graft function and immunosuppressive drug pharmacokinetics of direct antiviral agents (DAAs) among hepatitis C virus (HCV)-infected kidney transplant (KT) recipients remain unclear. We compared pre- and post-treatment 12-month trajectories of estimated glomerular filtration rate (ΔeGFR) and 24-h proteinuria (Δ24-h proteinuria) in 49 recipients treated with DAAs (mostly sofosbuvir plus ledipasvir). Among evaluable patients, 66.7% and 100.0% had undetectable viral load by week 4 and end of therapy (EoT). The sustained virologic response rate at 12 weeks was 95.8%. Overall, 80.6% of patients receiving tacrolimus required dose escalation while on DAA-based therapy (median increase of 66.7%) to maintain target levels. Tacrolimus levels resulted to be higher at 12 months compared to EoT (7.8 ± 2.1 vs. 6.7 ± 2.0 ng/ml; P-value = 0.002). No changes in graft function during the course of therapy were observed. However, eGFR significantly decreased (P-value <0.001) throughout the first 12 months after EoT. Median ΔeGFR and Δ24-h over pre- and post-treatment periods were 3.9% and -6.1% (P-value = 0.002) and -5.3% and 26.2% (P-value = 0.057). Caution should be exercised when adjusting immunosuppression in HCV-infected KT recipients upon initiation of DAAs, followed by mid-term monitoring of immunosuppressive drug levels and graft function.

Asunaprevir: An HCV Protease Inhibitor With Preferential Liver Distribution

Asunaprevir is an inhibitor of the hepatitis C virus (HCV) NS3/4A protease, demonstrating efficacy in clinical studies in patients infected with HCV genotype 1 or 4, with either peginterferon/ribavirin or combinations of direct-acting antivirals. Because of preferential distribution of asunaprevir to the liver via organic anion-transporting polypeptide (OATP)-mediated transport, asunaprevir demonstrates high apparent oral clearance and very low plasma concentrations. Asunaprevir plasma concentrations are markedly increased by single-dose rifampin (an OATP inhibitor) and in subjects with moderate to severe hepatic impairment. In addition, modestly higher plasma concentrations of asunaprevir have been noted in subjects infected with HCV relative to healthy subjects and in Asian subjects relative to whites. At the marketed dose, infrequent hepatic transaminase abnormalities were poorly predicted by plasma concentrations. For a compound with these characteristics, hepatic concentrations may have provided an improved understanding of the in vivo pharmacokinetic and pharmacodynamic data to support decision making during development.

Population Pharmacokinetic Analysis of Asunaprevir in Subjects with Hepatitis C Virus Infection

Introduction

Asunaprevir (ASV) is a potent, pangenotypic, twice-daily hepatitis C virus (HCV) NS3 inhibitor indicated for the treatment of chronic HCV infection.

Methods

A population pharmacokinetic (PPK) model was developed using pooled ASV concentration data from 1239 HCV-infected subjects who received ASV either as part of the DUAL regimen with daclatasvir or as part of the QUAD regimen with daclatasvir and peg-interferon/ribavirin.

Results

A two-compartment model with first-order elimination from the central compartment, an induction effect on clearance, and an absorption model consisted of zero-order release followed by first-order absorption adequately described ASV PK after oral administration. A typical value for ASV clearance (CL/F) was 50.8 L/h, increasing by 43% after 2 days to a CL/F of 72.5 L/h at steady-state, likely due to auto-induction of cytochrome P450 3A4 (CYP3A4). Factors indicative of hepatic function were identified as key influential covariates on ASV exposures. Subjects with cirrhosis had an 84% increase in ASV area under the concentration time curve (AUC) and subjects with baseline aspartate aminotransferase (AST) above 78 IU/L had a 58% increase in area under the concentration time curve (AUC). Asians subjects had a 46% higher steady-state AUC relative to White/Caucasian subjects. Other significant covariates were formulation, age, and gender.

Conclusion

The current PPK model provided a parsimonious description of ASV concentration data in HCV-infected subjects. Key covariates identified in the model help explain the observed variability in ASV exposures and may guide clinical use of the drug.

Funding

Bristol-Myers Squibb.

Electronic supplementary material

The online version of this article (10.1007/s40121-018-0197-y) contains supplementary material, which is available to authorized users.

Hepatitis C following liver transplantation: current approach and future research opportunities

PURPOSE OF REVIEW

The treatment of hepatitis C virus infection (HCV) in liver transplant recipients was very limited until direct-acting antivirals became widely available. We review the current approach to HCV treatment following liver transplantation and future research opportunities.

RECENT FINDINGS

Current treatment of HCV infection with all oral new direct-acting antivirals in the postliver transplant setting is easier, shorter, tolerable, and more effective with high-sustained virological response rates. However, some challenges remain, including the optimal timing of therapy, drug-drug interactions, renal insufficiency, and HIV coinfection.

SUMMARY

Patients with recurrent HCV following liver transplant will significantly benefit from all oral new direct acting antivirals. Ongoing studies will determine the optimal timing and combination in this unique population.

Decreased tacrolimus plasma concentrations during HCV therapy: a drug-drug interaction or is there an alternative explanation?

Chronic hepatitis C virus (HCV) infection can cause severe liver cirrhosis, for which liver transplantation is the only therapy. To prevent organ rejection, transplanted patients are treated with immunosuppressive agents. We describe two transplanted patients treated with tacrolimus who were simultaneously treated with direct-acting antivirals (DAAs) for their chronic HCV infection. No pharmacokinetic drug-drug interactions (DDIs) were expected between tacrolimus and the selected DAAs. However, in both patients, tacrolimus plasma concentrations decreased during HCV treatment. We hypothesise that decreased plasma concentrations were not caused by a DDI but were an indirect result of the clearance of the HCV infection. During chronic HCV infection, pro-inflammatory cytokines may inhibit cytochrome P450 (CYP) enzymes, which are primarily responsible for tacrolimus metabolism. If this is true, then with clearance of the virus the activity of these enzymes will normalise and tacrolimus metabolism will increase. These changes were clinically relevant because the tacrolimus dosage needed to be adjusted. Therefore, physicians should be aware that CYP substrates with narrow therapeutic ranges might require dose adaption during HCV therapy with DAAs.

Drug-Drug Interactions with the NS3/4A Protease Inhibitor Simeprevir

Simeprevir is an NS3/4A protease inhibitor approved for the treatment of hepatitis C infection, as a component of combination therapy. Simeprevir is metabolized by the cytochrome P450 (CYP) system, primarily CYP3A, and is a substrate for several drug transporters, including the organic anion transporting polypeptides (OATPs). It is susceptible to metabolic drug–drug interactions with drugs that are moderate or strong CYP3A inhibitors (e.g. ritonavir and erythromycin) or CYP3A inducers (e.g. rifampin and efavirenz); coadministration of these drugs may increase or decrease plasma concentrations of simeprevir, respectively, and should be avoided. Clinical studies have shown that simeprevir is a mild inhibitor of CYP1A2 and intestinal CYP3A but does not inhibit hepatic CYP3A. The effects of simeprevir on these enzymes are of clinical relevance only for narrow-therapeutic-index drugs that are metabolized solely by these enzymes (e.g. oral midazolam). Simeprevir does not have a clinically relevant effect on the pharmacokinetics of rilpivirine, tacrolimus, oral contraceptives and several other drugs metabolized by CYP enzymes. Simeprevir is a substrate and inhibitor of the transporters P-glycoprotein (P-gp), breast cancer resistance protein (BCRP) and OATP1B1/3. Cyclosporine is an inhibitor of OATP1B1/3, BCRP and P-gp, and a mild inhibitor of CYP3A; cyclosporine causes a significant increase in simeprevir plasma concentrations, and coadministration is not recommended. Clinical studies have demonstrated increases in coadministered drug concentrations for drugs that are substrates of the OATP1B1/3, BRCP (e.g. rosuvastatin) and P-gp (e.g. digoxin) transporters; these drugs should be administered with dose titration and or/close monitoring.

CYP3A activity: towards dose adaptation to the individual

INTRODUCTION

Co-medication, gene polymorphisms and co-morbidity are main causes for high variability in expression and function of the CYP3A isoenzymes. Pharmacokinetic variability is a major source of interindividual variability of drug effect and response of CYP3A substrates. While CYP3A genotyping is of limited use, direct testing of enzyme function ('phenotyping') may be more promising to achieve individualized dosing of CYP3A substrates.

AREAS COVERED

We will discuss available phenotyping strategies for CYP3A isoenzymes and causes of intra- and interindividual variability of CYP3A. The impact of phenotyping on the dose selection and pharmacokinetics of CYP3A substrates (docetaxel, irinotecan, tyrosine kinase inhibitors, ciclosporin, tacrolimus) are reviewed. Pubmed searches were conducted during March-November 2015 to retrieve articles related to CYP3A enzyme, phenotyping, drug interactions with CYP3A probe substrates, and phenotyping-guided dosing algorithms.

EXPERT OPINION

While ample data is available on the choice appropriate phenotyping drugs (midazolam, alfentanil, aplrazolam, buspirone, triazolam), less clinical trial data is available concerning strategies to usefully guide dosing in the clinical practice. Implementation into the clinical routine necessitates further research to identify (1) an easy-to-use and cheap test for CYP3A activity that (2) adequately predicts drug exposure to (3) allow a sound decision on dose adaptation and hence (4) improve clinical outcome and/or reduce the intensity or frequency of adverse drug effects.

Impact of fibrosis progression on clinical outcome in patients treated for post-transplant hepatitis C recurrence

BACKGROUND & AIMS

Patients who achieve sustained virological response (SVR) following the treatment of post-liver transplant (LT) recurrence of hepatitis C virus (HCV) infection have improved outcomes. The full impact of eradication of HCV on allograft histology is, however, not clearly known.

METHODS

We studied allograft histology in protocol-based paired liver biopsies in consecutive LT recipients who underwent post-LT treatment of recurrence of HCV.

RESULTS

A total of 116 patients were treated with interferon-based therapy for recurrent HCV. Paired pre-treatment baseline biopsies and post-treatment biopsies were available in 83.2% of patients. SVR was achieved in 37.9% of patients. Among the patients who achieved SVR, 20.5% had progression of fibrosis on post-treatment biopsies vs. 65.5% of patients with non-response/relapse (P < 0.001). The impact of virological response on fibrosis progression was sustained and a similar outcome was observed in the subset of patients who had 4-5 year post-treatment biopsies available. In the SVR group, 12.8% progressed to fibrosis stage ≥3 on post-treatment biopsies vs. 37.9% in the non-response/relapse group (P = 0.001). The 5-year survival in patients with progression of fibrosis 86% vs. 98% among patients who had improvement/stable fibrosis [P = 0.003; HR 3.8 (1.2-11.8)]. A small subset of patients who achieve SVR unfortunately still experience progression of fibrosis, most commonly associated with plasma cell hepatitis.

CONCLUSIONS

In post-transplant patients treated for HCV, SVR is associated with improved graft survival and also with sustained and significant improvement in histological outcome. Importantly, progression of fibrosis still occurred in a small subset of patients who achieved SVR.

Increased serum oxysterol concentrations in patients with chronic hepatitis C virus infection

Oxidative stress and dysregulated cholesterol metabolism are characteristic features of chronic hepatitis C virus infection (CHC). Therefore, we analyzed serum oxysterol profiles in CHC patients and examined the significance of oxysterols in CHC. The concentrations of 7α-hydroxycholesterol, 4β-hydroxycholesterol and 25-hydroxycholesterol as determined by LC-ESI-MS/MS were significantly elevated by +236%, +29% and +44%, respectively, in CHC patients compared with controls. Moreover, the elevated levels were significantly decreased by anti-viral therapy using PEGylated-interferon and ribavirin for 3 months. In contrast, 24S-hydroxycholesterol, 27-hydroxycholesterol and 7α-hydroxy-4-cholesten-3-one concentrations were not affected by CHC or anti-viral treatment. These results suggest that some oxysterols that are elevated in CHC are produced by cholesterol autoxidation due to oxidative stress or inflammation in the liver. Oxysterols may represent novel targets for the inhibition of disease progression and the prevention of hepatocarcinogenesis in CHC patients.