Polymorphisms in the organic anion transporting polypeptide genes influence liver parenchymal enhancement in gadoxetic acid-enhanced MRI

Predicting disruptions to drug pharmacokinetics and the risk of adverse drug reactions in non-alcoholic steatohepatitis patients

The liver plays a central role in the pharmacokinetics of drugs through drug metabolizing enzymes and transporters. Non-alcoholic steatohepatitis (NASH) causes disease-specific alterations to the absorption, distribution, metabolism, and excretion (ADME) processes, including a decrease in protein expression of basolateral uptake transporters, an increase in efflux transporters, and modifications to enzyme activity. This can result in increased drug exposure and adverse drug reactions (ADRs). Our goal was to predict drugs that pose increased risks for ADRs in NASH patients. Bibliographic research identified 71 drugs with reported ADRs in patients with liver disease, mainly non-alcoholic fatty liver disease (NAFLD), 54 of which are known substrates of transporters and/or metabolizing enzymes. Since NASH is the progressive form of NAFLD but is most frequently undiagnosed, we identified other drugs at risk based on NASH-specific alterations to ADME processes. Here, we present another list of 71 drugs at risk of pharmacokinetic disruption in NASH, based on their transport and/or metabolism processes. It encompasses drugs from various pharmacological classes for which ADRs may occur when used in NASH patients, especially when eliminated through multiple pathways altered by the disease. Therefore, these results may inform clinicians regarding the selection of drugs for use in NASH patients.

Gadoxetic acid-enhanced magnetic resonance imaging predicts hyperbilirubinemia induced by glecaprevir during hepatitis C virus treatment

Glecaprevir is a substrate for organic anion-transporting polypeptide (OATP) 1B1/1B3, which transports bilirubin. Hyperbilirubinemia is an adverse event during anti-hepatitis C virus treatment with glecaprevir and pibrentasvir. Gadoxetic acid is also transported by OATP1B1/1B3, and we aimed to evaluate whether gadoxetic acid-enhanced magnetic resonance (MR) imaging was associated with glecaprevir trough concentrations (C_trough). We further determined whether this was predictive of hyperbilirubinemia development in a cohort of 33 patients. The contrast enhancement index (CEI), a measure of hepatic enhancement effect on the hepatobiliary image, was assessed. Glecaprevir C_trough was determined 7 days after administration. Five of the 33 patients (15%) developed Common Terminology Criteria for Adverse Events grade ≥ 2 hyperbilirubinemia. We found a negative relationship between CEI and C_trough (r = − 0.726, p < 0.001). The partial correlation coefficient between CEI and C_trough was − 0.654 (p < 0.001), while excluding the effects of albumin, FIB-4 index, and indirect bilirubin at baseline. The C_trough was significantly higher in patients with hyperbilirubinemia than in those without (p = 0.008). In multivariate analysis, CEI ≤ 1.71 was an independent factor influencing the development of hyperbilirubinemia (p = 0.046). Our findings indicate that gadoxetic acid MR imaging can help predict glecaprevir concentration and development of hyperbilirubinemia.

Gadoxetate-Enhanced MRI as a Diagnostic Tool in the Management of Hepatocellular Carcinoma: Report from a 2020 Asia-Pacific Multidisciplinary Expert Meeting

Gadoxetate magnetic resonance imaging (MRI) is widely used in clinical practice for liver imaging. For optimal use, we must understand both its advantages and limitations. This article is the outcome of an online advisory board meeting and subsequent discussions by a multidisciplinary group of experts on liver diseases across the Asia-Pacific region, first held on September 28, 2020. Here, we review the technical considerations for the use of gadoxetate, its current role in the management of patients with hepatocellular carcinoma (HCC), and its relevance in consensus guidelines for HCC imaging diagnosis. In the latter part of this review, we examine recent evidence evaluating the impact of gadoxetate on clinical outcomes on a continuum from diagnosis to treatment decision-making and follow-up. In conclusion, we outline the potential future roles of gadoxetate MRI based on an evolving understanding of the clinical utility of this contrast agent in the management of patients at risk of, or with, HCC.

Pilot study of gadoxetate disodium-enhanced mri for localized and metastatic prostate cancers

OATP1B3 is expressed de novo in primary prostate cancer tissue and to a greater degree in prostate cancer metastases. Gadoxetate disodium is a substrate of OATP1B3, and its uptake has been shown to correlate with OATP1B3 expression in other cancers. We aimed to evaluate use of gadoxetate disodium to image prostate cancer and to track its utility as a biomarker. A single center open-label non-randomized pilot study recruited men with (1) localized, and (2) metastatic castration resistant prostate cancer (mCRPC). Gadoxetate disodium-enhanced MRI was performed at four timepoints post-injection. The Wilcoxon signed rank test was used to compare MRI contrast enhancement ratio (CER) pre-injection and post-injection. OATP1B3 expression was evaluated via immunohistochemistry (IHC) and a pharmacogenomic analysis of OATP1B3, NCTP and OATP1B1 was conducted. The mCRPC subgroup (n = 9) demonstrated significant enhancement compared to pre-contrast images at 20-, 40- and 60-min timepoints (p < 0.0078). The localized cancer subgroup (n = 11) demonstrated earlier enhancement compared to the mCRPC group, but no retention over time (p > 0.05). OATP1B3 expression on IHC trended higher contrast enhancement between 20–40 min (p ≤ 0.064) and was associated with contrast enhancement at 60 min (p = 0.0422). OATP1B1 haplotype, with N130D and V174A substitutions, impacted enhancement at 40–60 min (p ≤ 0.038). mCRPC lesions demonstrate enhancement after injection of gadoxetate disodium on MRI and retention over 60 min. As inter-individual variability in OATP1B3 expression and function has both predictive and prognostic significance, gadoxetate disodium has potential as a biomarker in prostate cancer.

Use of imaging to assess the activity of hepatic transporters

Introduction: Membrane transporters of the SLC and ABC families are abundantly expressed in the liver, where they control the transfer of drugs/drug metabolites across the sinusoidal and canalicular hepatocyte membranes and play a pivotal role in hepatic drug clearance. Noninvasive imaging methods, such as PET, SPECT or MRI, allow for measuring the activity of hepatic transporters in vivo, provided that suitable transporter imaging probes are available.Areas covered: We give an overview of the working principles of imaging-based assessment of hepatic transporter activity. We discuss different currently available PET/SPECT radiotracers and MRI contrast agents and their applications to measure hepatic transporter activity in health and disease. We cover mathematical modeling approaches to obtain quantitative parameters of transporter activity and provide a critical assessment of methodological limitations and challenges associated with this approach.Expert opinion: PET in combination with pharmacokinetic modeling can be potentially applied in drug development to study the distribution of new drug candidates to the liver and their clearance mechanisms. This approach bears potential to mechanistically assess transporter-mediated drug-drug interactions, to assess the influence of disease on hepatic drug disposition and to validate and refine currently available in vitro-in vivo extrapolation methods to predict hepatic clearance of drugs.

Gadoxetic acid-enhanced magnetic resonance imaging to predict paritaprevir-induced hyperbilirubinemia during treatment of hepatitis C

Background

Paritaprevir inhibits organic anion–transporting polypeptide (OATP)1B1 and OATP1B3, which transport bilirubin. Hyperbilirubinemia is an adverse event reported during hepatitis C treatment. Gadoxetic acid is also transported by OATP1B1/1B3. We evaluated whether the enhancement effect in gadoxetic acid–enhanced magnetic resonance (MR) imaging could predict the plasma concentration of paritaprevir and might anticipate the development of hyperbilirubinemia.

Methods

This prospective study evaluated 27 patients with hepatitis C who underwent gadoxetic acid–enhanced MR imaging prior to treatment with ombitasvir, paritaprevir, and ritonavir. The contrast enhancement index (CEI), a measure of liver enhancement during the hepatobiliary phase, was assessed. Plasma trough concentrations, and concentrations at 2, 4, and 6 h after dosing were determined 7 d after the start of treatment.

Results

Seven patients (26%) developed hyperbilirubinemia (≥ 1.6 mg/dl). Paritaprevir trough concentration (C_trough) was significantly higher in patients with hyperbilirubinemia than in those without (p = 0.022). We found an inverse relationship between CEI and C_trough (r = 0.612, p = 0.001), while there was not a significantly weak inverse relationship between AUC_{0–6 h} and CEI (r = −0.338, p = 0.085). The partial correlation coefficient between CEI and C_trough was −0.425 (p = 0.034), while excluding the effects of albumin and the FIB-4 index. Receiver operating characteristic (ROC) curve analysis showed that the CEI was relatively accurate in predicting hyperbilirubinemia, with area under the ROC of 0.882. Multivariate analysis showed that the CEI < 1.61 was the only independent predictor related to the development of hyperbilirubinemia, with an odds ratio of 9.08 (95% confidence interval 1.05–78.86, p = 0.046).

Conclusions

Hepatic enhancement with gadoxetic acid was independently related to paritaprevir concentration and was an independent pretreatment factor in predicting hyperbilirubinemia. Gadoxetic acid–enhanced MR imaging can therefore be useful in determining the risk of paritaprevir-induced hyperbilirubinemia.

Imaging techniques to study drug transporter function in vivo

Transporter systems involved in the permeation of drugs and solutes across biological membranes are recognized as key determinants of pharmacokinetics. Typically, the action of membrane transporters on drug exposure to tissues in living organisms is inferred from invasive procedures, which cannot be applied in humans. In recent years, imaging methods have greatly progressed in terms of instruments, synthesis of novel imaging probes as well as tools for data analysis. Imaging allows pharmacokinetic parameters in different tissues and organs to be obtained in a non-invasive or minimally invasive way. The aim of this overview is to summarize the current status in the field of molecular imaging of drug transporters. The overview is focused on human studies, both for the characterization of transport systems for imaging agents as well as for the determination of drug pharmacokinetics, and makes reference to animal studies where necessary. We conclude that despite certain methodological limitations, imaging has a great potential to study transporters at work in humans and that imaging will become an important tool, not only in drug development but also in medicine. Imaging allows the mechanistic aspects of transport proteins to be studied, as well as elucidating the influence of genetic background, pathophysiological states and drug-drug interactions on the function of transporters involved in the disposition of drugs.

Gadoxetic Acid-Enhanced MR Imaging Predicts Simeprevir-Induced Hyperbilirubinemia During Hepatitis C Virus Treatment: A Pilot Study

Simeprevir is a substrate for organic anion-transporting polypeptides (OATPs) that transport bilirubin. Hyperbilirubinemia is an adverse event reported during treatment of chronic hepatitis C patients with simeprevir plus pegylated interferon and ribavirin. Because gadoxetic acid is also a substrate of OATPs, pretreatment gadoxetic acid-enhanced magnetic resonance imaging (MRI) may predict hyperbilirubinemia during treatment. This prospective study therefore evaluated 11 consecutive patients with chronic hepatitis C who underwent gadoxetic acid-enhanced MRI prior to treatment with simeprevir plus pegylated interferon and ribavirin for 12 weeks, followed by pegylated interferon and ribavirin for an additional 12 weeks. Their contrast enhancement index (CEI), an index of liver parenchymal enhancement during the hepatobiliary phase, was assessed before treatment. Plasma trough concentrations (C_trough ) of simeprevir were determined 7 days after its administration, and serum bilirubin concentrations were measured throughout the course of treatment. Six patients (55%) developed hyperbilirubinemia (≥1.6 mg/dL) during treatment. C_trough was significantly higher in patients with than without hyperbilirubinemia (P = .009), with a strong inverse relationship between CEI and C_trough (r = -0.911, P < .001). CEI was significantly lower in patients with than without hyperbilirubinemia (P = .009), but there were no significant differences between the 2 groups in pretreatment serum albumin concentrations and FIB-4 index, an index of liver fibrosis. Hepatic enhancement with gadoxetic acid was related to C_trough of simeprevir. Gadoxetic acid-enhanced magnetic resonance imaging may predict the development of hyperbilirubinemia during treatment of hepatitis C patients with simeprevir plus pegylated interferon and ribavirin.

Evaluation of hepatocellular carcinoma development in patients with chronic hepatitis C by EOB-MRI

AIM: To evaluate the efficacy of ethoxibenzyl-magnetic resonance imaging (EOB-MRI) as a predictor of hepatocellular carcinoma (HCC) development.

METHODS: Between August 2008 and 2009, we studied 142 hepatitis C virus-infected patients (male 70, female 72), excluding those with HCC or a past history, who underwent EOB-MRI in our hospital. The EOB-MRI index [liver-intervertebral disc ratio (LI)] was calculated as: (post-liver intensity/post-intervertebral disc intensity)/(pre-liver intensity/pre-intervertebral disc intensity).

RESULTS: The median follow-up period was 3.1 years and the patients were observed until the end of the study period (31 December, 2012). In the follow-up period, HCC occurred in 21 patients. The cumulative occurrence rates were 2.1%, 9.1%, and 14.1% at 1, 2, and 3 years, respectively. Using the optimal cut-off value of LI 1.46, on univariate analysis, age, aspartate amino transferase (AST), α-fetoprotein (AFP) ≥ 10, albumin, total cholesterol, prothrombin time, platelets, and LI < 1.46 were identified as independent factors, but on multivariate analysis, LI < 1.46: risk ratio 6.05 (1.34-27.3, P = 0.019) and AFP ≥ 10: risk ratio 3.1 (1.03-9.35, P = 0.045) were identified as independent risk factors. LI and Fib-4 index have higher area under the receiver operating characteristic curves than other representative fibrosis evaluation methods, such as Forn’s index and AST-to-platelet ratio index.

CONCLUSION: LI is associated with the risk of HCC occurrence in hepatitis C patients. LI may be a substitute for liver biopsy when evaluating this risk and its combined use with Fib-4 is a better predictive method of HCC progression.