Limited contribution of common genetic variants to risk for liver injury due to a variety of drugs

Clinical Features and Outcomes of Complementary and Alternative Medicine Induced Acute Liver Failure and Injury

OBJECTIVES

The increasing use of complementary and alternative medicines (CAMs) has been associated with a rising incidence of CAM-induced drug-induced liver injury (DILI). The aim of this study was to examine the clinical features and outcomes among patients with acute liver failure (ALF) and acute liver injury (ALI) enrolled in the Acute Liver Failure Study Group database, comparing CAM-induced with prescription medicine (PM)-induced DILI.

METHODS

A total of 2,626 hospitalized patients with ALF/ALI of any etiology were prospectively enrolled between 1998 and 2015 from 32 academic transplant centers. Only those with CAM or PM-induced ALI/ALF were selected for analysis.

RESULTS

A total of 253 (9.6%) subjects were found to have idiosyncratic DILI, of which 41 (16.3%) were from CAM and 210 (83.7%) were due to PM. The fraction of DILI-ALF/ALI cases due to CAM increased from 1998-2007 to 2007-2015 (12.4 vs. 21.1%, P=0.047). There was no difference in the type of liver injury-hepatocellular, cholestatic, or mixed-between groups as determined by R score (P=0.26). PM-induced DILI showed higher serum alkaline phosphatase levels compared with the CAM group (median IU/L, 171 vs. 125, P=0.003). The CAM population had fewer comorbid conditions (1.0 vs. 2.0, P<0.005), higher transplantation rates (56 vs. 32%, P<0.005), and a lower ALF-specific 21-day transplant-free survival (17 vs. 34%, P=0.044).

CONCLUSIONS

CAM-induced DILI is at least as severe in presentation as that observed due to PM with higher rates of transplantation and lower transplant-free survival in those who progress to ALF. This study highlights the increasing incidence of CAM-induced liver injury and emphasizes the importance of early referral and evaluation for liver transplantation when CAM-induced liver injury is suspected.

Characterization of cytochrome P450 isoforms involved in sequential two-step bioactivation of diclofenac to reactive p-benzoquinone imines

Idiosyncratic drug-induced lever injury (IDILI) is a rare but severe side effect of diclofenac (DF). Several mechanisms have been proposed as cause of DF-induced toxicity including the formation of protein-reactive diclofenac-1',4'-quinone imine (DF-1',4'-QI) and diclofenac-2,5-quinone imine (DF-2,5-QI). Formation of these p-benzoquinone imines result from two-step oxidative metabolism involving aromatic hydroxylation to 4'-hydroxydiclofenac and 5-hydroxydiclofenac followed by dehydrogenation to DF-1',4'-QI and DF-2,5-QI, respectively. Although the contribution of individual cytochrome P450s (CYPs) in aromatic hydroxylation of DF is well studied, the enzymes involved in the dehydrogenation reactions have been poorly characterized. The results of the present study show that both formation of 4'-hydroxydiclofenac and it subsequent bioactivation to DF-1',4'-QI is selectively catalyzed by CYP2C9. However, the two-step bioactivation to DF-2,5-QI appears to be catalyzed with highest activity by two different CYPs: 5-hydroxylation of DF is predominantly catalyzed by CYP3A4, whereas its subsequent bioactivation to DF-2,5-QI is catalyzed with 14-fold higher intrinsic clearance by CYP2C9. The fact that both CYPs involved in two-step bioactivation of DF show large interindividual variability may play a role in different susceptibility of patients to DF-induced IDILI. Furthermore, expression levels of these enzymes and protective enzymes might be important factors determining sensitivity of in vitro models for hepatotoxicity.

Liver injury from nonsteroidal anti-inflammatory drugs in the United States

BACKGROUND & AIMS

Nonsteroidal anti-inflammatory drugs (NSAIDs) are commonly used and have been associated with hepatotoxicity. Studies of liver injury from NSAIDs have been retrospective and prospective data are lacking. The aim was to report the features and outcomes of the subjects with severe drug-induced liver injury from NSAIDS.

METHODS

The U.S. Drug Induced Liver Injury Network is a prospective registry of idiosyncratic drug hepatotoxicity. All patients are evaluated in a standard fashion and followed up for at least 6 months.

RESULTS

Of 1221 Drug Induced Liver Injury Network cases that were adjudicated, 30 cases were attributed to eight different NSAIDs. The mean age was 52 years old, 24 (80%) were women, and 21 (70%) were Caucasian. The mean latency was 67 days. Common signs and symptoms at presentation were nausea (73%), jaundice (67%) and dark urine (67%). Mean peak serum aspartate aminotransferase, alanine aminotransferase, total bilirubin and alkaline phosphatase were 898 U/L, 1060 U/L, 12.2 mg/dl and 326 U/L. The most common pattern of injury was hepatocellular (70%) and autoantibodies were detected in 33% of cases. Diclofenac, was the most frequently implicated NSAID (16/30 cases), and characterized by hepatocellular injury. Seventeen cases resulted in hospitalization or prolongation of hospitalization and one patient died from complications of Stevens-Johnson syndrome because of diclofenac.

CONCLUSIONS

Hepatocellular injury is the most common pattern seen with NSAID hepatotoxicity, and diclofenac is the most frequently implicated agent. Given the number of NSAID alternatives, diclofenac should be reserved for patients who fail other NSAIDs and a high level of suspicion for hepatotoxicity should be maintained.

Adverse drug reactions and organ damage: The liver

Drug-induced liver injury (DILI) is among the most challenging acute or chronic liver conditions to be handled by physicians. Despite its low incidence in the general population, DILI is a frequent cause of acute liver failure. As such, the possibility of DILI should be considered in all patients who present with acute liver damage, independent of any known pre-existing liver disease. DILI can be classified as intrinsic/dose-dependent (e.g., acetaminophen toxicity) or idiosyncratic/dose-independent, with the latter form being relatively uncommon. Amoxicillin-clavulanate is the antimicrobial that is most frequently associated with idiosyncratic DILI. Large, ongoing, prospective studies in western countries have reported other drugs associated with DILI, including nonsteroidal anti-inflammatory drugs, statins, and herbal and dietary supplements. An important safety issue, DILI is one of the most frequently cited reasons for cessation of drug development during or after preclinical studies and for withdrawal of a drug from the market. This review summarizes the epidemiology, risk factors, commonly implicated drugs, clinical features, and diagnosis of DILI, with the aim of aiding physicians in the management of this debated problem. Old and new biomarkers for DILI and pharmacogenetic studies are also described.

Current and future directions in the treatment and prevention of drug-induced liver injury: a systematic review

While the pace of discovery of new agents, mechanisms and risk factors involved in drug-induced liver injury (DILI) remains brisk, advances in the treatment of acute DILI seems slow by comparison. In general, the key to treating suspected DILI is to stop using the drug prior to developing irreversible liver failure. However, predicting when to stop is an inexact science, and commonly used ALT monitoring is an ineffective strategy outside of clinical trials. The only specific antidote for acute DILI remains N-acetylcysteine (NAC) for acetaminophen poisoning, although NAC is proving to be beneficial in some cases of non-acetaminophen DILI in adults. Corticosteroids can be effective for DILI associated with autoimmune or systemic hypersensitivity features. Ursodeoxycholic acid, silymarin and glycyrrhizin have been used to treat DILI for decades, but success remains anecdotal. Bile acid washout regimens using cholestyramine appear to be more evidenced based, in particular for leflunomide toxicity. For drug-induced acute liver failure, the use of liver support systems is still investigational in the United States and emergency liver transplant remains limited by its availability. Primary prevention appears to be the key to avoiding DILI and the need for acute treatment. Pharmacogenomics, including human leukocyte antigen genotyping and the discovery of specific DILI biomarkers offers significant promise for the future. This article describes and summarizes the numerous and diverse treatment and prevention modalities that are currently available to manage DILI.

The chemical, genetic and immunological basis of idiosyncratic drug–induced liver injury

Idiosyncratic drug reactions can be extremely severe and are not accounted for by the regular pharmacology of a drug. Thus, the mechanism of idiosyncratic drug–induced liver injury (iDILI), a phenomenon that occurs with many drugs including β-lactams, anti-tuberculosis drugs and non-steroidal anti-inflammatories, has been difficult to determine and remains a pressing issue for patients and drug companies. Evidence has shown that iDILI is multifactorial and multifaceted, which suggests that multiple cellular mechanisms may be involved. However, a common initiating event has been proposed to be the formation of reactive drug metabolites and covalently bound adducts. Although the fate of these metabolites are unclear, recent evidence has shown a possible link between iDILI and the adaptive immune system. This review highlights the role of reactive metabolites, the recent genetic innovations which have provided molecular targets for iDILI, and the current literature which suggests an immunological basis for iDILI.

The Art and Science of Diagnosing and Managing Drug-induced Liver Injury in 2015 and Beyond

Drug-induced liver injury (DILI) remains a leading reason why new compounds are dropped from further study or are the subject of product warnings and regulatory actions. Hy's Law of drug-induced hepatocellular jaundice causing a case-fatality rate or need for transplant of 10% or higher has been validated in several large national registries, including the ongoing, prospective U.S. Drug-Induced Liver Injury Network. It serves as the basis for stopping rules in clinical trials and in clinical practice. Because DILI can mimic all known causes of acute and chronic liver disease, establishing causality can be difficult. Histopathologic findings are often nonspecific and rarely, if ever, considered pathognomonic. A daily drug dose >50-100 mg is more likely to be hepatotoxic than does <10 mg, especially if the compound is highly lipophilic or undergoes extensive hepatic metabolism. The quest for a predictive biomarker to replace alanine aminotransferase is ongoing. Markers of necrosis and apoptosis such as microRNA-122 and keratin 18 may prove useful in identifying patients at risk for severe injury when they initially present with a suspected acetaminophen overdose. Although a number of drugs causing idiosyncratic DILI have HLA associations that may allow for pre-prescription testing to prevent hepatotoxicity, the cost and relatively low frequency of injury among affected patients limit the current usefulness of such genome-wide association studies. Alanine aminotransferase monitoring is often recommended but has rarely been shown to be an effective method to prevent serious DILI. Guidelines on the diagnosis and management of DILI have recently been published, although specific therapies remain limited. The LiverTox Web site has been introduced as an interactive online virtual textbook that makes the latest information on more than 650 agents available to clinicians, regulators, and drug developers alike.

Risk factors for severe or fatal drug-induced liver injury from amoxicillin-clavulanic acid

AIM

To identify risk factors for severe liver injury or mortality from drug-induced liver injury (DILI) from amoxicillin-clavulanic acid. To determine if co-administration of potentially hepatotoxic drugs was associated with an increased risk of DILI from amoxicillin-clavulanic acid.

METHODS

We conducted a systematic review of the published work and data extraction of articles on DILI injury from amoxicillin-clavulanic acid. Potentially hepatotoxic drugs were defined as medications with DILI listed in the package insert or reported in the published work. Individual patient data were entered into an SPSS (version 17.0; Chicago, IL, USA) database and were analyzed using the χ(2) -test or Fisher's exact test; Student's t-test; and non-parametric tests such as Mann-Whitney U-test as appropriate.

RESULTS

We identified 3932 articles of which 41 publications with 255 reported cases met inclusion criteria. Mortality from DILI from amoxicillin-clavulanic acid was increased among patients receiving concomitant potentially hepatotoxic drugs compared with patients not on concomitant potential hepatotoxic drugs (21.4% [3/14] vs 2.3% [2/89], P = 0.017]. The most common classes of concomitant drugs were: antimicrobials, analgesics and hormonal therapy. Female patients were more likely to receive a concomitant potentially hepatotoxic medication (25% vs 9.1% for men, P = 0.05).

CONCLUSION

Patients who developed severe or fatal DILI from amoxicillin-clavulanic acid were more likely to be on concomitant hepatotoxic medications. Female patients were more likely to receive concomitant hepatotoxic drugs. Further studies are needed to investigate drug interaction between amoxicillin-clavulanic acid and concomitant potentially hepatotoxic drugs.

Nuclear receptor variants in liver disease

This snapshot reviews the current state of knowledge on genetic variants of nuclear receptors (NRs) involved in regulating various aspects of liver metabolism. Interindividual differences in responses to diet and other 'in-' and environmental stressors can be caused by variants in components of the NR regulatory gene network. We recapitulate recent evidence for the application of NRs in genetic diagnosis of monogenic liver disease. Genetic analysis of multifactorial liver diseases, such as nonalcoholic fatty liver disease and diabetes mellitus, pinpoints key players in disease predisposition and progression. In particular, NR1H4 variants have been associated with intrahepatic cholestasis of pregnancy and gallstone disease. Other examples include studies of NR1I2 and NR1I3 polymorphisms in patients with drug-induced liver injury and NR5A2 variation in cholangiocarcinoma. Associations of NR gene variants have been identified in patients with dyslipidemia and other metabolic syndrome-associated traits by genome-wide studies. Evidence from these analyses confirms a role for NR variation in common diseases, linking regulatory networks to complex and variable phenotypes. These new insights into the impact of NR variants offer perspectives for their future use in diagnosis and treatment of common diseases.

Genetics of liver disease: From pathophysiology to clinical practice

Paralleling the first 30 years of the Journal of Hepatology we have witnessed huge advances in our understanding of liver disease and physiology. Genetic advances have played no small part in that. Initial studies in the 1970s and 1980s identified the strong major histocompatibility complex associations in autoimmune liver diseases. During the 1990 s, developments in genomic technologies drove the identification of genes responsible for Mendelian liver diseases. Over the last decade, genome-wide association studies have allowed for the dissection of the genetic susceptibility to complex liver disorders, in which also environmental co-factors play important roles. Findings have allowed the identification and elaboration of pathophysiological processes, have indicated the need for reclassification of liver diseases and have already pointed to new disease treatments. In the immediate future genetics will allow further stratification of liver diseases and contribute to personalized medicine. Challenges exist with regard to clinical implementation of rapidly developing technologies and interpretation of the wealth of accumulating genetic data. The historical perspective of genetics in liver diseases illustrates the opportunities for future research and clinical care of our patients.

Analysis of IL-6, STAT3 and HSPA1L gene polymorphisms in anti-tuberculosis drug-induced hepatitis in a nested case-control study

OBJECTIVES

To investigate the association of IL-6, STAT3 and HSPA1L polymorphisms with the risk of anti-tuberculosis drug-induced hepatitis (ATDH) in Chinese Han population.

METHODS

The study was designed as a nested case-control study within a prospective cohort. Each case was matched with four controls by sex, age at baseline (±5 years), treatment history, disease severity, drug dosage and place of sample collection. Genetic polymorphisms of IL-6, STAT3 and HSPA1L were determined blindly by TaqMan single-nucleotide polymorphism (SNP) genotyping assay. Odds ratio (OR) with 95% confidence intervals (CIs) was estimated by conditional logistic regression model to measure the association between selected SNPs and the risk of ATDH.

RESULTS

A total of 89 incident ATDH cases and 356 ATDH-free controls were genotyped for IL-6 (rs2066992, rs2069837, rs1524107), STAT3 (rs1053004, rs1053023, rs1053005) and HSPA1L (rs2227956). In genotype analysis, no significant difference was observed in genotypes frequencies of the seven selected SNPs between case and control group after Bonferroni correction. In haplotype analysis, carriers with STAT3 GAT and AGC (rs1053023-rs1053005-rs1053004) haplotypes had a significantly higher risk of ATDH compared with wild-type haplotype (P<0.0001).

CONCLUSION

This study suggested that genetic variants of STAT3 might contribute to ATDH susceptibility in Chinese Han population. Studies in larger, varied populations are required to confirm these findings.

Signal transducer and activator of transcription 4 in liver diseases

STAT4 is a member of the signal transducer and activator of transcription (STAT) family of molecules that localizes to the cytoplasm. STAT4 regulates various genes expression as a transcription factor after it is phosphorylated, dimerizes and translocates to the nucleus. STAT4 activation is detected virtually in the liver of several mouse models of liver injury, as well as the human liver of chronic liver diseases. STAT4 gene polymorphism has been shown to be associated with the antiviral response in chronic hepatitis C and drug-induced liver injury (DILI), primary biliary cirrhosis (PBC), HCV-associated liver fibrosis and in hepatocellular carcinoma (HCC). However, the roles of STAT4 in the pathogeneses of liver diseases are still not understood entirely. This review summarizes the recent advances on the functional roles of STAT4 and its related cytokines in liver diseases, especially in regulating hepatic anti-viral responses, inflammation, proliferation, apoptosis and tumorigenesis. Targeting STAT4 signaling pathway might be a promising strategy in developing therapeutic approaches for treating hepatitis in order to prevent further injury like cirrhosis and liver cancer.

Key factors of susceptibility to anti-tuberculosis drug-induced hepatotoxicity

Anti-tuberculosis drug-induced hepatotoxicity (ATDH) is one of the leading adverse drug reactions during the course of tuberculosis treatment and poses a considerable challenge to clinicians and researchers. Previous studies have revealed the important contribution of drug metabolism and transporter enzymes to the complexity of ATDH. The emerging roles of immune response and oxidative stress resulting from reactive metabolite in the development of ATDH have also gained attention recently. Both non-genetic and genetic factors can have a significant impact on the susceptibility to ATDH, consequently altering the risk of hepatotoxicity in susceptible individuals. Non-genetic risk factors associated with ATDH include host factors, environment factors and drug-related factors. Genetic factors contributing to the susceptibility of ATDH involve genetic variations in bioactivation/toxification pathways via the cytochrome P450 enzymes (phase I), detoxification reactions by N-acetyl transferase 2, glutathione S-transferase and uridine diphosphate glucuronosyltransferase (phase II) and hepatic transport (phase III), together with immunological factors and antioxidant response. Better understanding of these factors may help to predict and prevent the occurrence of ATDH and develop more effective treatments. This review focuses on the mechanisms of ATDH and the key factors of susceptibility associated with drug metabolism, hepatic transport, immune response and oxidative stress.

Mechanisms of drug-induced liver injury

PURPOSE OF REVIEW

Idiosyncratic drug-induced liver injury (iDILI) is a relatively rare condition, but can have serious consequences for the individual patient, public health, regulatory agencies and the pharmaceutical industry. Despite increased awareness of iDILI, its underlying mechanism is still not fully understood. This review summarizes the current understanding of the molecular mechanism behind iDILI.

RECENT FINDINGS

Genetic variations in drug metabolizing genes are in line with proposed mechanisms based on acetaminophen hepatotoxicity, whereby reactive metabolites covalently bind to cellular proteins and disturb the redox balance. In addition, immune-mediated effects have been reported for flucloxacillin hepatotoxicity, demonstrating both haptenization and direct binding between the drug and immune receptors.

SUMMARY

Idiosyncratic DILI development is believed to be orchestrated by multiple events, such as reactive metabolite formations, oxidative stress and signalling pathway inductions, with the mitochondria taking centre stage. Evidence also points towards the immune system (innate and adaptive responses) as important components in iDILI. Interindividual differences in one or more of these events, due to genetic variations and environmental factors, are likely to contribute to the idiosyncratic nature of this condition and subsequently distinguish between patient susceptibility and tolerance.

Toward predictive models for drug-induced liver injury in humans: are we there yet?

Drug-induced liver injury (DILI) is a frequent cause for the termination of drug development programs and a leading reason of drug withdrawal from the marketplace. Unfortunately, the current preclinical testing strategies, including the regulatory-required animal toxicity studies or simple in vitro tests, are insufficiently powered to predict DILI in patients reliably. Notably, the limited predictive power of such testing strategies is mostly attributed to the complex nature of DILI, a poor understanding of its mechanism, a scarcity of human hepatotoxicity data and inadequate bioinformatics capabilities. With the advent of high-content screening assays, toxicogenomics and bioinformatics, multiple end points can be studied simultaneously to improve prediction of clinically relevant DILIs. This review focuses on the current state of efforts in developing predictive models from diverse data sources for potential use in detecting human hepatotoxicity, and also aims to provide perspectives on how to further improve DILI prediction.

Liver injury from herbals and dietary supplements in the U.S. Drug-Induced Liver Injury Network

The Drug-Induced Liver Injury Network (DILIN) studies hepatotoxicity caused by conventional medications as well as herbals and dietary supplements (HDS). To characterize hepatotoxicity and its outcomes from HDS versus medications, patients with hepatotoxicity attributed to medications or HDS were enrolled prospectively between 2004 and 2013. The study took place among eight U.S. referral centers that are part of the DILIN. Consecutive patients with liver injury referred to a DILIN center were eligible. The final sample comprised 130 (15.5%) of all subjects enrolled (839) who were judged to have experienced liver injury caused by HDS. Hepatotoxicity caused by HDS was evaluated by expert opinion. Demographic and clinical characteristics and outcome assessments, including death and liver transplantation (LT), were ascertained. Cases were stratified and compared according to the type of agent implicated in liver injury; 45 had injury caused by bodybuilding HDS, 85 by nonbodybuilding HDS, and 709 by medications. Liver injury caused by HDS increased from 7% to 20% (P < 0.001) during the study period. Bodybuilding HDS caused prolonged jaundice (median, 91 days) in young men, but did not result in any fatalities or LT. The remaining HDS cases presented as hepatocellular injury, predominantly in middle-aged women, and, more frequently, led to death or transplantation, compared to injury from medications (13% vs. 3%; P < 0.05).

CONCLUSIONS

The proportion of liver injury cases attributed to HDS in DILIN has increased significantly. Liver injury from nonbodybuilding HDS is more severe than from bodybuilding HDS or medications, as evidenced by differences in unfavorable outcomes (death and transplantation). (Hepatology 2014;60:1399-1408).

Effect of drug transporter pharmacogenetics on cholestasis

INTRODUCTION

The liver is the central place for the metabolism of drugs and other xenobiotics. In the liver cell, oxidation and conjugation of compounds take place, and at the same time, bile formation helps in extrusion of these compounds via the biliary route. A large number of transporters are responsible for drug uptake into the liver cell and excretion into bile or efflux to the sinusoidal blood.

AREAS COVERED

Genetic variants of these transporters and their transactivators contribute to changes in drug handling and are also responsible for cholestatic syndromes of different severity. This review summarizes the current knowledge regarding the influence of these genetic changes. The review covers progressive hereditary cholestatic syndromes as well as recurrent or transient cholestatic syndromes such as drug-induced liver injury, intrahepatic cholestasis of pregnancy, and benign recurrent intrahepatic cholestasis.

EXPERT OPINION

Polymorphisms in transporter genes are frequent. For clinically relevant cholestatic syndromes, it often requires a combination of genetic variants or acquired triggers such as pregnancy or drug treatment. In combination with other pathogenetic aspects, genetic variants in drug transporters may contribute to our understanding of not only cholestatic diseases such as primary sclerosing cholangitis or primary biliary cirrhosis, but also the natural course of chronic liver disease in general.

Acetaminophen-induced Liver Injury: from Animal Models to Humans

Drug-induced liver injury is an important clinical problem and a challenge for drug development. Whereas progress in understanding rare and unpredictable (idiosyncratic) drug hepatotoxicity is severely hampered by the lack of relevant animal models, enormous insight has been gained in the area of predictable hepatotoxins, in particular acetaminophen-induced liver injury, from a broad range of experimental models. Importantly, mechanisms of toxicity obtained with certain experimental systems, such as in vivo mouse models, primary mouse hepatocytes, and metabolically competent cell lines, are being confirmed in translational studies in patients and in primary human hepatocytes. Despite this progress, suboptimal models are still being used and experimental data can be confusing, leading to controversial conclusions. Therefore, this review attempts to discuss mechanisms of drug hepatotoxicity using the most studied drug acetaminophen as an example. We compare the various experimental models that are used to investigate mechanisms of acetaminophen hepatotoxicity, discuss controversial topics in the mechanisms, and assess how these experimental findings can be translated to the clinic. The success with acetaminophen in demonstrating the clinical relevance of experimental findings could serve as an example for the study of other drug toxicities.

Predicting idiosyncratic drug-induced liver injury: some recent advances

Drug-induced liver injury (DILI) is a major challenge for the pharmaceutical industry, regulatory authorities, and clinicians. It is usually categorized into 'intrinsic' and 'idiosyncratic', but DILI caused by most drugs is of an idiosyncratic nature and usually cannot be predicted from the regulatory required animal toxicity studies. Unfortunately, some individuals exposed to therapeutic dose will develop idiosyncratic DILI that might involve severe clinical outcome, and no biomarker is available to identify the susceptible patients prior to drug treatment. In this editorial, we summarized the recent advances in predicting idiosyncratic DILI and provided the perspectives to improve the prediction.

Relationship between characteristics of medications and drug-induced liver disease phenotype and outcome

BACKGROUND & AIMS

It is not known whether specific characteristics of medication are associated with type of drug-induced liver injury (DILI) or outcome. We examined the relationships among select characteristics of medications and DILI phenotype and outcome.

METHODS

We analyzed 383 cases of DILI caused by a single orally administered prescription agent from the DILI Network Prospective Study with causalities of definite, highly likely, or probable. Relationship of daily dosage (≥50 mg vs ≤49 mg), preponderance of hepatic metabolism (≥50% vs <50%), or Biopharmaceutics Drug Disposition Classification System (BDDCS) class (1-4, based on solubility and metabolism of the drug) were compared with clinical characteristics and outcomes.

RESULTS

Compared with cases of DILI in the ≤49 mg/day group, those associated with daily dosages ≥50 mg had shorter latency (median, 38 days vs 56 days; P = .03) and a different biochemical pattern of liver injury (P = .04); no differences in recovery, severity, or outcome were observed. Patients with DILI caused by medications with or without preponderant hepatic metabolism did not differ in clinical characteristics or outcomes. Compared with other classes of BDDCS, DILI caused by BDDCS class 1 medications had significantly longer latency (P < .001) and greater proportion of hepatocellular injury (P = .001). However, peak liver biochemical values and patients' time to recovery, disease severity, and outcomes did not differ among the 4 BDDCS classes.

CONCLUSIONS

Characteristics of medications (dosage, hepatic metabolism, and solubility) are associated with features of DILI such as latency and pattern of liver injury, but not with recovery, severity, or outcome.

N-acetyltransferase 2 (NAT2) genotype as a risk factor for development of drug-induced liver injury relating to antituberculosis drug treatment in a mixed-ethnicity patient group

PURPOSE

This study aims to assess whether NAT2 genotype affects susceptibility to moderate to severe liver injury in patients undergoing drug treatment for tuberculosis with isoniazid-containing regimens.

METHODS

Twenty-six patients of European or South Asian ethnicity, who had suffered liver injury during treatment with isoniazid-containing drug regimens and 101 ethnically matched controls were genotyped for the NAT2*5, NAT2*6, and NAT2*7 alleles. Genotyping for additional polymorphisms in the NAT gene region was also performed on 20 of the 26 cases. NAT2 genotype frequency between cases and controls was compared.

RESULTS

NAT2 genotypes predicting a slow acetylator phenotype were found to be associated with an increased risk of isoniazid-related liver injury (odds ratio (OR) = 4.25 (95% confidence interval (CI), 1.36-13.22); p = 0.012) with 85% of the cases being slow acetylators compared with 56% of the controls. There was no evidence for an increased risk for the slow acetylator genotype in patients with the most severe cases of liver injury, who underwent liver transplantation.

CONCLUSIONS

The NAT2 slow acetylator genotype appears to be a significant risk factor for moderate and severe drug- induced liver injury. However, the overall effect size is modest and generally in line with effects described previously for this genotype in milder drug-induced liver injury. Additional genetic risk factors may also contribute.

Selected ABCB1, ABCB4 and ABCC2 polymorphisms do not enhance the risk of drug-induced hepatotoxicity in a Spanish cohort

Background and Aims

Flawed ABC transporter functions may contribute to increased risk of drug-induced liver injury (DILI). We aimed to analyse the influence of genetic variations in ABC transporters on the risk of DILI development and clinical presentations in a large Spanish DILI cohort.

Methods

A total of ten polymorphisms in ABCB1 (1236T>C, 2677G>T,A, 3435T>C), ABCB4 (1954A>G) and ABCC2 (−1774G>del, −1549A>G, −24C>T, 1249G>A, 3972C>T and 4544G>A) were genotyped using Taqman 5′ allelic discrimination assays or sequencing in 141 Spanish DILI patients and 161 controls. The influence of specific genotypes, alleles and haplotypes on the risk of DILI development and clinical presentations was analysed.

Results

None of the individual polymorphisms or haplotypes was found to be associated with DILI development. Carriers homozygous for the ABCC2 −1774del allele were however only found in DILI patients. Hence, this genotype could potentially be associated with increased risk, though its low frequency in our Spanish cohort prevented a final conclusion. Furthermore, carriers homozygous for the ABCC2 −1774G/−1549A/−24T/1249G/3972T/4544G haplotype were found to have a higher propensity for total bilirubin elevations when developing DILI.

Conclusions

Our findings do not support a role for the analysed polymorphisms in the ABCB1, ABCB4 and ABCC2 transporter genes in DILI development in Spanish patients. The ABCC2 −1774deldel genotype was however restricted to DILI cases and could potentially contribute to enhanced DILI susceptibility.

Pharmacogenovigilance: a pharmacogenomics pharmacovigilance program

In this report, we review the importance of pharmacovigilance in detecting postmarketing adverse drug events and the potential for developing pharmacogenovigilance programs by integrating pharmacogenomics with pharmacovigilance. We propose to start developing such a program in primary healthcare systems that use basic features of electronic medical records and have access to large numbers of patients commonly prescribed drugs. Such programs, if carefully designed, may grow over time and hopefully enhance the collection and interpretation of useful data for the clinical applications of pharmacogenomics testing.

Pathogenesis of idiosyncratic drug-induced liver injury and clinical perspectives

Idiosyncratic drug-induced liver injury (DILI) is a rare disease that develops independently of drug dose, route, or duration of administration. Furthermore, idiosyncratic DILI is not a single disease entity but rather a spectrum of rare diseases with varying clinical, histological, and laboratory features. The pathogenesis of DILI is not fully understood. Standardization of the DILI nomenclature and methods to assess causality, along with the information provided by the LiverTox Web site, will harmonize and accelerate research on DILI. Studies of new serum biomarkers such as glutamate dehydrogenase, high mobility group box protein 1, and microRNA-122 could provide information for use in diagnosis and prognosis and provide important insights into the mechanisms of the pathogenesis of DILI. Single nucleotide polymorphisms in the HLA region have been associated with idiosyncratic hepatotoxicity attributed to flucloxacillin, ximelagatran, lapatinib, and amoxicillin-clavulanate. However, genome-wide association studies of pooled cases have not associated any genetic factors with idiosyncratic DILI. Whole genome and whole exome sequencing analyses are under way to study cases of DILI attributed to a single medication. Serum proteomic, transcriptome, and metabolome as well as intestinal microbiome analyses will increase our understanding of the mechanisms of this disorder. Further improvements to in vitro and in vivo test systems should advance our understanding of the causes, risk factors, and mechanisms of idiosyncratic DILI.

Risk of drug-induced liver injury with the new oral anticoagulants: systematic review and meta-analysis

OBJECTIVE

In recent years, safety alerts have been made warning of the risk of serious drug-induced liver injury (DILI) caused by cardiovascular drugs. The new oral anticoagulants (NOACs) have now reached the market. However, safety concerns have been raised about their hepatic safety. Therefore we aimed to evaluate NOAC liver-related safety.

METHODS

Systematic review and meta-analysis of phase III randomised controlled trials (RCTs). Medline and CENTRAL were searched to September 2013. Reviews and reference lists were also searched. Two reviewers independently searched for studies and retrieved data estimates. Primary outcome was DILI (transaminases elevations >3× upper limit of normal (ULN) with total bilirubin >2× ULN). NOACs were compared against any control group. Random-effects meta-analysis was performed, and pooled estimates were expressed as relative risk (RR) and 95% CI heterogeneity was evaluated with I(2) test.

RESULTS

Twenty-nine RCTs evaluating 152 116 patients (mean follow-up of 16 months) were included. All RCTs were rated as having low risk of bias. NOAC were not associated with an increased risk of DILI (RR 0.90, 95% CI 0.72 to 1.13, I(2)=0%). Similar results were obtained for individual NOAC (rivaroxaban, apixaban, dabigatran, darexaban, edoxaban) and considering the different control groups (vitamin K antagonists, low molecular weight heparin (LMWH) and placebo). The risk of transaminases elevations (>3×ULN) was lower among NOAC-treated patients, in particular in comparison with LMWH-treated patients (RR 0.71, 95% CI 0.59 to 0.85; I(2)=27%)

CONCLUSIONS

NOACs are not associated with an increased risk of DILI. The unexpected 'protective' effect of NOAC is probably due to LMWH-associated hepatotoxicity.

Emerging hepatotoxicity biomarkers and their potential to improve understanding and management of drug-induced liver injury

Biomarkers of drug-induced liver injury (DILI) are essential for the diagnosis of severe cases of DILI in clinical trials and clinical practice, but the currently used biomarker paradigm detects damage after it has occurred and has limited prognostic value. The development of new biomarker strategies that improve the diagnosis of DILI by providing increased specificity and/or by identifying individual patients who are at risk for DILI is therefore crucial.

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Serum acute phase reactants hallmark healthy individuals at risk for acetaminophen-induced liver injury

Background

Acetaminophen (APAP) is a commonly used analgesic. However, its use is associated with drug-induced liver injury (DILI). It is a prominent cause of acute liver failure, with APAP hepatotoxicity far exceeding other causes of acute liver failure in the United States. In order to improve its safe use this study aimed to identify individuals at risk for DILI prior to drug treatment by searching for non-genetic serum markers in healthy subjects susceptible to APAP-induced liver injury (AILI).

Methods

Healthy volunteers (n = 36) received either placebo or acetaminophen at the maximum daily dose of 4 g for 7 days. Blood samples were taken prior to and after APAP treatment. Serum proteomic profiling was done by 2D SDS-PAGE and matrix-assisted laser desorption/ionization-time of flight-mass spectrometry. Additionally, the proteins C-reactive protein, haptoglobin and hemopexin were studied by quantitative immunoassays.

Results

One-third of study subjects presented more than four-fold increased alanine transaminase activity to evidence liver injury, while serum proteomics informed on 20 proteins as significantly regulated. These function primarily in acute phase and immune response. Pre-treatment associations included C-reactive protein, haptoglobin isoforms and retinol binding protein being up to six-fold higher in AILI susceptible individuals, whereas alpha1-antitrypsin, serum amyloid A, kininogen and transtyretin were regulated by nearly five-fold in AILI responders. When compared with published findings for steatohepatitis and cases of hepatocellular, cholestatic and mixed DILI, 10 proteins were identified as uniquely associated with risk for AILI, including plasminogen. Notably, this zymogen facilitates macrophage chemotactic migration and inflammatory response as reported for plasminogen-deficient mice shown to be resistant to APAP hepatotoxicity. Finally, analysis of a publicly available database of gene expression profiles of cultures of human hepatocytes treated with drugs labeled as no- (n = 8), low- (n = 45) or most-DILI-concern (n = 39) confirmed regulation of the identified biomarkers to demonstrate utility in predicting risk for liver injury.

Conclusions

The significant regulation of acute phase reactants points to an important link between AILI and the immune system. Monitoring of serum acute phase reactants prior to drug treatment may contribute to prevention and management of AILI, and may also be of utility for other drugs with known liver liabilities.

A collaborative approach to developing an electronic health record phenotyping algorithm for drug-induced liver injury

OBJECTIVE

To describe a collaborative approach for developing an electronic health record (EHR) phenotyping algorithm for drug-induced liver injury (DILI).

METHODS

We analyzed types and causes of differences in DILI case definitions provided by two institutions-Columbia University and Mayo Clinic; harmonized two EHR phenotyping algorithms; and assessed the performance, measured by sensitivity, specificity, positive predictive value, and negative predictive value, of the resulting algorithm at three institutions except that sensitivity was measured only at Columbia University.

RESULTS

Although these sites had the same case definition, their phenotyping methods differed by selection of liver injury diagnoses, inclusion of drugs cited in DILI cases, laboratory tests assessed, laboratory thresholds for liver injury, exclusion criteria, and approaches to validating phenotypes. We reached consensus on a DILI phenotyping algorithm and implemented it at three institutions. The algorithm was adapted locally to account for differences in populations and data access. Implementations collectively yielded 117 algorithm-selected cases and 23 confirmed true positive cases.

DISCUSSION

Phenotyping for rare conditions benefits significantly from pooling data across institutions. Despite the heterogeneity of EHRs and varied algorithm implementations, we demonstrated the portability of this algorithm across three institutions. The performance of this algorithm for identifying DILI was comparable with other computerized approaches to identify adverse drug events.

CONCLUSIONS

Phenotyping algorithms developed for rare and complex conditions are likely to require adaptive implementation at multiple institutions. Better approaches are also needed to share algorithms. Early agreement on goals, data sources, and validation methods may improve the portability of the algorithms.

Pharmacogenomics of severe cutaneous adverse reactions and drug-induced liver injury

Rare but severe adverse drug reactions (ADRs) are an important issue in drug development and in the proper usage of drugs during the post-approval phase. The ability to predict patient susceptibility to severe ADRs would prevent drug administration to high-risk patients. This would save lives and ensure the quality of life for these patients, but occurrence of idiosyncratic severe ADRs had been very difficult to predict for a long time. However, in this decade, genetic markers have been found for several ADRs, especially for severe cutaneous adverse reactions (SCARs) and drug-induced liver injury (DILI). In this review, we summarize recent progress in identifying genetic markers for SCARS and DILI, and discuss issues that remain unresolved. As for SCARs, associations of HLA-B*15:02 or HLA-A*31:01 and HLA-B*58:01 have been revealed for carbamazepine- and allopurinol-related Stevens-Johnson syndrome and toxic epidermal neclolysis, respectively. HLA-B*57:01 is strongly associated with abacavir-induced hypersensitivity syndrome. Several HLA alleles also demonstrate drug-specific associations with DILI, such as HLA-A*33:03 for ticlopidine, HLA-B*57:01 for flucloxacillin and HLA-DQA1*02:01 for lapatinib. Efforts should be continued to find other genetic markers to achieve high predictability for ADRs, with the goal being development of genetic tests for use in clinical settings.

Pharmacogenomics of adverse drug reactions

Considerable progress has been made in identifying genetic risk factors for idiosyncratic adverse drug reactions in the past 30 years. These reactions can affect various tissues and organs, including liver, skin, muscle and heart, in a drug-dependent manner. Using both candidate gene and genome-wide association studies, various genes that make contributions of varying extents to each of these forms of reactions have been identified. Many of the associations identified for reactions affecting the liver and skin involve human leukocyte antigen (HLA) genes and for reactions relating to the drugs abacavir and carbamazepine, HLA genotyping is now in routine use prior to drug prescription. Other HLA associations are not sufficiently specific for translation but are still of interest in relation to underlying mechanisms for the reactions. Progress on non-HLA genes affecting adverse drug reactions has been less, but some important associations, such as those of SLCO1B1 and statin myopathy, KCNE1 and drug-induced QT prolongation and NAT2 and isoniazid-induced liver injury, are considered. Future prospects for identification of additional genetic risk factors for the various adverse drug reactions are discussed.