Relationship between daily dose of oral medications and idiosyncratic drug-induced liver injury: search for signals

Worldwide Use of RUCAM for Causality Assessment in 81,856 Idiosyncratic DILI and 14,029 HILI Cases Published 1993-Mid 2020: A Comprehensive Analysis

Background: A large number of idiosyncratic drug induced liver injury (iDILI) and herb induced liver injury(HILI) cases of variable quality has been published but some are a matter of concern if the cases were not evaluated for causality using a robust causality assessment method (CAM) such as RUCAM (Roussel Uclaf Causality Assessment Method) as diagnostiinjuryc algorithm. The purpose of this analysis was to evaluate the worldwide use of RUCAM in iDILI and HILI cases. Methods: The PubMed database (1993-30 June 2020) was searched for articles by using the following key terms: Roussel Uclaf Causality Assessment Method; RUCAM; Idiosyncratic drug induced liver injury; iDILI; Herb induced liver injury; HILI. Results: Considering reports published worldwide since 1993, our analysis showed the use of RUCAM for causality assessment in 95,885 cases of liver injury including 81,856 cases of idiosyncratic DILI and 14,029 cases of HILI. Among the top countries providing RUCAM based DILI cases were, in decreasing order, China, the US, Germany, Korea, and Italy, with China, Korea, Germany, India, and the US as the top countries for HILI. Conclusion: Since 1993 RUCAM is certainly the most widely used method to assess causality in IDILI and HILI. This should encourage practitioner, experts, and regulatory agencies to use it in order to reinforce their diagnosis and to take sound decisions.

Drug-Induced Liver Injury After Liver Transplantation

Drug-induced liver injury (DILI) is an adverse reaction to many drugs in common use that in a liver transplantation (LT) recipient may cause graft dysfunction and may even lead to graft loss and the need for retransplantation. However, several potential clinical scenarios, such as graft rejection and infection, can confound the diagnosis of suspected DILI in the setting of LT. This makes causal assessment of a new liver injury more uncertain and has traditionally precluded collection of bona fide cases of DILI affecting LT patients in prospective DILI registries and cohorts. Although no studies have yet determined a greater susceptibility of the transplant patient to DILI, these patients nevertheless present certain risk factors that can theoretically increase the risk of DILI. These include the fact that these patients are polymedicated, use drugs that are potentially hepatotoxic, and can have coexisting hepatitis B or C viruses in addition to other factors found in nontransplant patients, such as genetic variants. Therefore, awareness is crucial of any potential hepatotoxic effect of drugs used in the LT recipient and their possible implication in any case of liver dysfunction. In the present article, we review the most common drugs used in LT recipients from a liver safety perspective and address the main pitfalls in attributing causality in this clinical setting. We also affirm the need for further research and collaboration in this somewhat neglected topic in the field of DILI.

Mechanistic insights into antiretroviral drug-induced liver injury

All classes of antiretroviral therapy (ART) have been implicated to induce adverse drug reactions such drug-induced liver injury (DILI) and immune-mediated adverse reactions in Human Immunodeficiency Virus (HIV) infected individuals. Patients that develop adverse drug reactions tend to have prolonged stays in hospital and may require to change to alternative regimens if reactions persist upon rechallenge or if rechallenge is contraindicated due to severity of the adverse reaction. Diagnosis of DILI remains a huge obstacle that delays timely interventions, since it is still based largely on exclusion of other causes. There is an urgent need to develop robust diagnostic and predictive biomarkers that could be used alongside the available tools (biopsy, imaging, and serological tests for liver enzymes) to give a specific diagnosis of DILI. Crucial to this is also achieving consensus in the definition of DILI so that robust studies can be undertaken. Importantly, it is crucial that we gain deeper insights into the mechanism of DILI so that patients can receive appropriate management. In general, it has been demonstrated that the mechanism of ART-induced liver injury is driven by four main mechanisms: mitochondrial toxicity, metabolic host-mediated injury, immune reconstitution, and hypersensitivity reactions. The focus of this review is to discuss the type and phenotypes of DILI that are caused by the first line ART regimens. Furthermore, we will summarize recent studies that have elucidated the cellular and molecular mechanisms of DILI both in vivo and in vitro.

Ligandrol (LGD-4033)-Induced Liver Injury

We described a 32-year-old man who developed severe drug-induced liver injury after using Ligandrol (LGD-4033). The diagnosis was confirmed by a liver biopsy that showed cholestatic hepatitis with a mild portal, periportal, and perisinusoidal fibrosis. Ligandrol is a selective androgen receptor modulator that is available over the counter and via the internet.

Excretion, Mass Balance, and Metabolism of [14C]LY3202626 in Humans: An Interplay of Microbial Reduction, Reabsorption, and Aldehyde Oxidase Oxidation That Leads to an Extended Excretion Profile

The mass balance, excretion, and metabolism of LY3202626 were determined in healthy subjects after oral administration of a single dose of 10 mg of (approximately 100 μCi) [¹⁴C]LY3202626. Excretion of radioactivity was slow and incomplete, with approximately 75% of the dose recovered after 504 hours of sample collection. The mean total recovery of the radioactive dose was 31% and 44% in the feces and urine, respectively. Because of low plasma total radioactivity, plasma metabolite profiling was conducted by accelerator mass spectrometry. Metabolism of LY3202626 occurred primarily via O-demethylation (M2) and amide hydrolysis (M1, M3, M4, and M5). Overall, parent drug, M1, M2, and M4 were the largest circulating components in plasma, and M2 and M4 were the predominant excretory metabolites. The slow elimination of total radioactivity was proposed to result from an unusual enterohepatic recirculation pathway involving microbial reduction of metabolite M2 to M16 in the gut and reabsorption of M16, followed by hepatic oxidation of M16 back to M2. Supporting in vitro experiments showed that M2 is reduced to M16 anaerobically in fecal homogenate and that M16 is oxidized in the liver by aldehyde oxidase to M2. LY3202626 also showed a potential to form a reactive sulfenic acid intermediate. A portion of plasma radioactivity was unextractable and presumably bound covalently to plasma proteins. In vitro incubation of LY3202626 in human liver microsomes in the presence of NADPH with dimedone as a trapping agent implicated the formation of the proposed sulfenic acid intermediate. SIGNIFICANCE STATEMENT: The excretion of radioactivity in humans after oral administration of a single dose of 10 mg of [¹⁴C]LY3202626 was very slow. The results from in vitro experiments suggested that an interplay between microbial reduction, reabsorption, and aldehyde oxidase oxidation (M2 → M16 → M2) could be a reason for extended radioactivity excretion profile. In vitro metabolism also showed that LY3202626 has the potential to form a reactive sulfenic acid intermediate that could potentially covalently bind to plasma protein and result in the observed unextractable radioactivity from plasma.

Drug-Induced Liver Injury in GI Practice

Although drug-induced liver injury (DILI) is a rare clinical event, it carries significant morbidity and mortality, leaving it as the leading cause of acute liver failure in the United States. It is one of the most challenging diagnoses encountered by gastroenterologists. The development of various drug injury networks has played a vital role in expanding our knowledge regarding drug-related and herbal and dietary supplement-related liver injury. In this review, we discuss what defines liver injury, epidemiology of DILI, its biochemical and pathologic patterns, and management.

Ashwagandha-induced liver injury: A case series from Iceland and the US Drug-Induced Liver Injury Network

BACKGROUND & AIMS

Ashwagandha (Withania somnifera) is widely used in Indian Ayurvedic medicine. Several dietary supplements containing ashwagandha are marketed in the US and Europe, but only one case of drug-induced liver injury (DILI) due to ashwagandha has been published. The aim of this case series was to describe the clinical phenotype of suspected ashwagandha-induced liver injury.

METHODS

Five cases of liver injury attributed to ashwagandha-containing supplements were identified; three were collected in Iceland during 2017-2018 and two from the Drug-Induced Liver Injury Network (DILIN) in 2016. Other causes for liver injury were excluded. Causality was assessed using the DILIN structured expert opinion causality approach.

RESULTS

Among the five patients, three were males; mean age was 43 years (range 21-62). All patients developed jaundice and symptoms such as nausea, lethargy, pruritus and abdominal discomfort after a latency of 2-12 weeks. Liver injury was cholestatic or mixed (R ratios 1.4-3.3). Pruritus and hyperbilirubinaemia were prolonged (5-20 weeks). No patient developed hepatic failure. Liver tests normalized within 1-5 months in four patients. One patient was lost to follow-up. One biopsy was performed, showing acute cholestatic hepatitis. Chemical analysis confirmed ashwagandha in available supplements; no other toxic compounds were identified. No patient was taking potentially hepatotoxic prescription medications, although four were consuming additional supplements, and in one case, rhodiola was a possible causative agent along with ashwagandha.

CONCLUSIONS

These cases illustrate the hepatotoxic potential of ashwagandha. Liver injury is typically cholestatic or mixed with severe jaundice and pruritus, but self-limited with liver tests normalizing in 1-5 months.

Immune dysregulation increases the incidence of delayed-type drug hypersensitivity reactions

Delayed-type, T cell-mediated, drug hypersensitivity reactions are a serious unwanted manifestation of drug exposure that develops in a small percentage of the human population. Drugs and drug metabolites are known to interact directly and indirectly (through irreversible protein binding and processing to the derived adducts) with HLA proteins that present the drug-peptide complex to T cells. Multiple forms of drug hypersensitivity are strongly linked to expression of a single HLA allele, and there is increasing evidence that drugs and peptides interact selectively with the protein encoded by the HLA allele. Despite this, many individuals expressing HLA risk alleles do not develop hypersensitivity when exposed to culprit drugs suggesting a nonlinear, multifactorial relationship in which HLA risk alleles are one factor. This has prompted a search for additional susceptibility factors. Herein, we argue that immune regulatory pathways are one key determinant of susceptibility. As expression and activity of these pathways are influenced by disease, environmental and patient factors, it is currently impossible to predict whether drug exposure will result in a health benefit, hypersensitivity or both. Thus, a concerted effort is required to investigate how immune dysregulation influences susceptibility towards drug hypersensitivity.

Understanding Idiosyncratic Toxicity: Lessons Learned from Drug-Induced Liver Injury

Idiosyncratic adverse drug reactions (IADRs) encompass a diverse group of toxicities that can vary by drug and patient. The complex and unpredictable nature of IADRs combined with the fact that they are rare makes them particularly difficult to predict, diagnose, and treat. Common clinical characteristics, the identification of human leukocyte antigen risk alleles, and drug-induced proliferation of lymphocytes isolated from patients support a role for the adaptive immune system in the pathogenesis of IADRs. Significant evidence also suggests a requirement for direct, drug-induced stress, neoantigen formation, and stimulation of an innate response, which can be influenced by properties intrinsic to both the drug and the patient. This Perspective will provide an overview of the clinical profile, mechanisms, and risk factors underlying IADRs as well as new approaches to study these reactions, focusing on idiosyncratic drug-induced liver injury.

Drug-Induced Liver Injury in the Setting of Chronic Liver Disease

Drug-induced liver injury (DILI) is an uncommon but significant cause of liver injury and need for liver transplant. DILI in the setting of chronic liver disease (CLD) is poorly understood. Clinical features of patients presenting with DILI in the setting of CLD are similar to those without CLD with the exception of a higher incidence of diabetes among those with CLD and DILI. Diagnosis of DILI in CLD is difficult because there are no objective biomarkers and current causality assessments have not been studied in this population. Differentiating DILI from exacerbation of underlying liver disease is even more challenging.

Epidemiology, Predisposing Factors, and Outcomes of Drug-Induced Liver Injury

Idiosyncratic drug-induced liver injury (DILI) is an underreported and underestimated adverse drug reaction. A recent population-based study found a crude incidence of approximately 19 cases per 100,000 a year. Amoxicillin-clavulanate continues to be the most commonly implicated agent in most Western countries, reported to occur in approximately 1 of 2300 users. In patients with drug-induced autoimmune hepatitis, liver tests often do not normalize with cessation of the drugs and require corticosteroids. DILI associated with jaundice can lead to death from liver failure or require liver transplantation in at least 10% of cases.

Dose Predictions for Drug Design

The efficacious dose of a drug is perhaps the most holistic metric reflecting its therapeutic potential. Dose is predicted at many stages in drug discovery and development. Prior to the 1990s, dose prediction was limited to the drug "working" at a reasonable dose and dose regimen in an animal model. Through the early 2000s, dose predictions were generated at candidate nomination and then refined during clinical development. Currently, dose predictions can be made early in drug discovery to enable drug design. Dose predictions at this stage can identify critical drug properties for a viable dose regimen and provide clinically relevant context to lead optimization. In this paper, we give an overview of the opportunities and challenges associated with dose prediction for drug design. A number of general considerations, approaches, and case examples are discussed.

T-Cell Activation by Low Molecular Weight Drugs and Factors That Influence Susceptibility to Drug Hypersensitivity

Drug hypersensitivity reactions adversely affect treatment outcome, increase the length of patients' hospitalization, and limit the prescription options available to physicians. In addition, late stage drug attrition and the withdrawal of licensed drugs cost the pharmaceutical industry billions of dollars. This significantly increases the overall cost of drug development and by extension the price of licensed drugs. Drug hypersensitivity reactions are characterized by a delayed onset, and reactions tend to be more serious upon re-exposure. The role of drug-specific T-cells in the pathogenesis of drug hypersensitivity reactions and definition of the nature of the binding interaction of drugs with HLA and T-cell receptors continues to be the focus of intensive research, primarily because susceptibility is associated with expression of one or a small number of HLA alleles. This review critically examines the mechanisms of T-cell activation by drugs. Specific examples of drugs that activate T-cells via the hapten, the pharmacological interaction with immune receptors and the altered self-peptide repertoire pathways, are discussed. Furthermore, the impacts of drug metabolism, drug-protein adduct formation, and immune regulation on the development of drug antigen-responsive T-cells are highlighted. The knowledge gained from understanding the pathways of T-cell activation and susceptibility factors for drug hypersensitivity will provide the building blocks for the development of predictive in vitro assays that will prevent or help to minimize the incidence of these reactions in clinic.

Strategies for Early Prediction and Timely Recognition of Drug-Induced Liver Injury: The Case of Cyclin-Dependent Kinase 4/6 Inhibitors

The idiosyncratic nature of drug-induced liver injury (DILI) represents a current challenge for drug developers, regulators and clinicians. The myriad of agents (including medications, herbals, and dietary supplements) with recognized DILI potential not only strengthens the importance of the post-marketing phase, when urgent withdrawal sometimes occurs for rare unanticipated liver toxicity, but also shows the imperfect predictivity of pre-clinical models and the lack of validated biomarkers beyond traditional, non-specific liver function tests. After briefly reviewing proposed key mechanisms of DILI, we will focus on drug-related risk factors (physiochemical and pharmacokinetic properties) recently proposed as predictors of DILI and use cyclin-dependent kinase 4/6 inhibitors, relatively novel oral anticancer medications approved for breast cancer, as a case study to discuss the feasibility of early detection of DILI signals during drug development: published data from pivotal clinical trials, unpublished post-marketing reports of liver adverse events, and pharmacokinetic properties will be used to provide a comparative evaluation of their liver safety and gain insight into drug-related risk factors likely to explain the observed differences.

Liver dysfunction induced by Levothyroxine Sodium Tablets (Euthyrox®) in a hypothyroid patient with Hashimoto's thyroiditis: case report and literature review

A 49-year-old woman with hypothyroidism developed liver dysfunction after increasing dose of levothyroxine (L-T4) (Euthyrox^®) from 25 μg to 50 μg. Viral hepatitis, autoimmune hepatitis and non-alcoholic steatohepatitis (NASH) were ruled out with examinations. She had no concurrent medication and had no history of infectious, chronic or any other autoimmune diseases. After cessation of Levothyroxine Sodium Tablets (Euthyrox^®), liver enzymes gradually returned to normal. She was diagnosed levothyroxine-induced liver injury, based on criteria proposed in "Diagnosis and treatment guideline on drug-induced liver injury" issued by the Chinese Medical Association (2015). As an alternative 25 μg qod of Levothyroxine Sodium Tablets (Letrox^®) was tried and increased gradually up to 75 μg daily. Since then liver enzymes have remained within normal range. The main difference of additive for both tablets is whether it contains lactose or not: Euthyrox^® contains lactose which caused no liver injury, thus excluding the possibility that an additive of Euthyrox^® contributed to liver injury. The relatively quicker and larger replacement with synthetic T4 for hypothyroidism inducing transient thyrotoxicosis was suspected, although thyroid function was normal. Immune-mediated drug-induced liver injury (DILI) was also not excluded. This is a rare case of drug-induced liver injury due to levothyroxine tablets. It reminded us that when replacement with synthetic T4 for hypothyroidism is done, smaller-dose initiation and slower-speed increase may be useful for treatment of cases similar to genetically susceptible individuals.

Designing around Structural Alerts in Drug Discovery

Cumulative research over several decades has implicated the involvement of reactive metabolites in many idiosyncratic adverse drug reactions (IADRs). Consequently, "avoidance" strategies have been inserted into drug discovery paradigms, which include the exclusion of structural alerts and possible termination of reactive metabolite-positive compounds. Several noteworthy examples where reactive metabolite-related liabilities have been resolved through structure-metabolism studies are presented herein. Considerable progress has also been made in addressing the limitations of the avoidance strategy and further refining the process of managing reactive metabolite issues in drug development. These efforts primarily stemmed from the observation that numerous drugs, which contain structural alerts and/or form reactive metabolites, are devoid of ADRs. The Perspective also dwells into an analysis of the structural alert/reactive metabolite concept with a discussion of risk mitigation tactics to support the progression of reactive metabolite-positive drug candidates.

Acute liver failure

Acute liver failure is a rare and severe consequence of abrupt hepatocyte injury, and can evolve over days or weeks to a lethal outcome. A variety of insults to liver cells result in a consistent pattern of rapid-onset elevation of aminotransferases, altered mentation, and disturbed coagulation. The absence of existing liver disease distinguishes acute liver failure from decompensated cirrhosis or acute-on-chronic liver failure. Causes of acute liver failure include paracetamol toxicity, hepatic ischaemia, viral and autoimmune hepatitis, and drug-induced liver injury from prescription drugs, and herbal and dietary supplements. Diagnosis requires careful review of medications taken, and serological testing for possible viral exposure. Because of its rarity, acute liver failure has not been studied in large, randomised trials, and most treatment recommendations represent expert opinion. Improvements in management have resulted in lower mortality, although liver transplantation, used in nearly 30% of patients with acute liver failure, still provides a life-saving alternative to medical management.

Drug-induced liver injury

Drug-induced liver injury (DILI), including herbal and dietary supplement hepatotoxicity, is often passed lightly; however, it can lead to the requirement of a liver transplant or may even cause death because of liver failure. Recently, the American College of Gastroenterology, Chinese Society of Hepatology and European Association for the Study of the Liver guidelines for the diagnosis and treatment of DILI have been established, and they will be helpful for guiding clinical treatment decisions. Roussel Uclaf Causality Assessment Method scoring is the most commonly used method to diagnose DILI; however, it has some limitations, such as poor validity and reproducibility. Recently, studies on new biomarkers have been actively carried out, which will help diagnose DILI and predict the prognosis of DILI. It is expected that the development of new therapies such as autophagy inducers and various other technologies of the fourth industrial revolution will be applicable to DILI research.

EASL Clinical Practice Guidelines: Drug-induced liver injury

Idiosyncratic (unpredictable) drug-induced liver injury is one of the most challenging liver disorders faced by hepatologists, because of the myriad of drugs used in clinical practice, available herbs and dietary supplements with hepatotoxic potential, the ability of the condition to present with a variety of clinical and pathological phenotypes and the current absence of specific biomarkers. This makes the diagnosis of drug-induced liver injury an uncertain process, requiring a high degree of awareness of the condition and the careful exclusion of alternative aetiologies of liver disease. Idiosyncratic hepatotoxicity can be severe, leading to a particularly serious variety of acute liver failure for which no effective therapy has yet been developed. These Clinical Practice Guidelines summarize the available evidence on risk factors, diagnosis, management and risk minimization strategies for drug-induced liver jury.

Dyslipidemia is a Risk Factor for the Incidence and Severity of Drug-Induced Liver Injury (DILI): A Retrospective Population-Based Study in China

Background

A Chinese population-based study aimed to investigate the risk factors for the incidence and severity of drug-induced liver injury (DILI) from Chinese herbal medicines and conventional Western medicines.

Material/Methods

Liver biopsy and routine laboratory testing, including serum lipid measurements, was performed on 465 patients, including 168 patients with DILI and 297 patients without DILI. Histological grading of DILI used the METAVIR scoring system and the severity of DILI was graded as levels 0–5. Multivariate and univariate regression analysis were used to compare the two study groups, using a risk-adjusted odds ratio (AOR).

Results

There was no significant association between age, alcohol status, cardiovascular disease (CVD), hypertension, or type 2 diabetes mellitus and development of DILI. However, when compared with controls, patients with dyslipidemia (AOR, 2.173; 95% CI, 1.388–3.401; P=0.001) had an increased incidence of DILI, and men had a reduced incidence of DILI when compared with women (AOR, 0.276; 95% CI, 0.169–0.450; P<0.001). Risk factors for severe DILI (≥level 3) included drinking alcohol (AOR, 6.506; 95% CI, 2.184–19.384; P=0.001), and dyslipidemia (AOR, 3.095; 95% CI, 1.345–7.123; P=0.008). Patients with an increased duration of drug treatment of >1 year had a reduced risk of developing severe DILI compared with patients with a medication duration of ≤1 month (AOR, 0.259; 95% CI, 0.084–0.802).

Conclusions

Increased risk of the incidence of DILI was significantly associated with female gender and dyslipidemia, and the risk of developing severe DILI was associated with drinking alcohol and dyslipidemia.

Tools for causality assessment in drug-induced liver disease

PURPOSE OF REVIEW

There are three liver-specific causality assessment tools currently available to guide clinical diagnosis of Drug-Induced Liver Injury (DILI): Roussel-Uclaf Causality Assessment Method (RUCAM), Digestive-Disease-Week Japan 2004 scale (DDW-J), and Clinical Diagnostic Scale (CDS). The purpose of this review is to assess these tools and discuss how to improve the causality assessment process as a whole.

RECENT FINDINGS

Existing DILI-specific causality assessment tools are surprisingly similar and exhibit only minor differences in point allocation. But difference in threshold for likelihood of being DILI. We reviewed the literature on currently used causality assessment tools, identified areas for future improvement, and herein propose approaches for refinement. Opportunities to improve current models, as well as the assessment process, in general, include in particular provision of more precise clinical detail and to perhaps add new components to scoring systems. For example, the incorporation of drug-specific clinical signature patterns, accounting for a drug's inherent hepatotoxicity potential, and/or incorporation of other drug properties to scoring systems may allow enhancement. Further, more systemic exclusion of competing diagnoses is needed. Finally, causality assessment processes will likely benefit from a data-driven and computer-assisted approach.

SUMMARY

Current tools used for DILI adjudication are imperfect. Avenues to improve these tools are described.

Measures of BSEP Inhibition In Vitro Are Not Useful Predictors of DILI

Inhibition of the bile salt export pump (BSEP) by a drug has been implicated as a risk factor for a drug's potential to cause drug-induced liver injury (DILI) and is thought to be an important mechanism leading to DILI. For a wide variety of drugs a correlation has been observed between the potency of in vitro BSEP inhibition and its propensity to cause DILI in humans. These findings were interpreted to suggest that BSEP inhibition could be an important mechanism to help explain how some drugs initiate DILI. Because the Biopharmaceutics Drug Disposition Classification System (BDDCS) can be useful in characterizing and predicting some important transporter effects in terms of drug-drug interactions, we evaluated the information provided by BDDCS in order to understand the inhibition propensity of BSEP. Here we analyze the relationship between a compound's ability to inhibit BSEP function and cause liver injury in humans using a compilation of published DILI datasets that have screened for BSEP inhibitors, other hepatic transporters and other mechanism-based toxicity key events. Our results demonstrate that there is little support for in vitro BSEP inhibition being universally DILI predictive. Rather we show that most potent BSEP inhibitors are BDDCS class 2 drugs, which we have demonstrated previously is the BDDCS class most likely to be DILI related. Since BDDCS class is not related to any proposed DILI mechanistic hypotheses, we maintain that if measures of BSEP inhibition alone or together with inhibition of other transporters cannot be differentiated from class 2 assignment, there is no support for in vitro BSEP inhibition being DILI predictive.

Discovery of a GPR40 Superagonist: The Impact of Aryl Propionic Acid α-Fluorination

GPR40 is a G-protein-coupled receptor which mediates fatty acid-induced glucose-stimulated insulin secretion from pancreatic beta cells and incretion release from enteroendocrine cells of the small intestine. GPR40 full agonists exhibit superior glucose lowering compared to partial agonists in preclinical species due to increased insulin and GLP-1 secretion, with the added benefit of promoting weight loss. In our search for potent GPR40 full agonists, we discovered a superagonist which displayed excellent in vitro potency and superior efficacy in the Gαs-mediated signaling pathway. Most synthetic GPR40 agonists have a carboxylic acid headgroup, which may cause idiosyncratic toxicities, including drug-induced-liver-injury (DILI). With a methyl group and a fluorine atom substituted at the α-C of the carboxylic acid group, 19 is not only highly efficacious in lowering glucose and body weight in rodent models but also has a low DILI risk due to its stable acylglucuronide metabolite.

The Beneficial Roles of SIRT1 in Drug-Induced Liver Injury

Drug-induced liver injury (DILI) is a major cause of acute liver failure (ALF) as a result of accumulated drugs in the human body metabolized into toxic agents and helps generate heavy oxidative stress, inflammation, and apoptosis, which induces necrosis in hepatocytes and ultimately damages the liver. Sirtuin 1 (SIRT1) is said to have multiple vital roles in cell proliferation, aging, and antistress systems of the human body. The levels of SIRT1 and its activation precisely modulate its critical role in the interaction between multiple step procedures of DILI. The nuclear factor kappa-light-chain-enhancer of activated B cell- (NF-κB-) mediated inflammation signaling pathway, reactive oxygen species (ROS), DNA damage, mitochondrial membrane potential collapse, and endoplasmic reticulum (ER) stress also contribute to aggravate DILI. Apoptosis is regarded as the terminal reaction followed by multiple signaling cascades including caspases, p53, and mitochondrial dysfunction which have been said to contribute in DILI. The SIRT1 activator is regarded as a potential candidate for DILI, because the former could inhibit signaling of p53, NF-κB, and ER stress. On the other hand, overexpression of SIRT1 also enhances the activation of antioxidant responses via Kelch-like ECH-associated protein 1- (Keap1-) nuclear factor- (erythroid-derived 2-) like 2 (Nrf2) signaling. The current manuscript will highlight the mechanism of DILI and the interaction of SIRT1 with various cytoplasmic factors leading to DILI along with the summary of potent SIRT1 agonists.

Pharmacogenomics of drug-induced liver injury (DILI): Molecular biology to clinical applications

A 21-year old woman was admitted to hospital with a two-week history of painless jaundice, fatigue and anorexia having previously been fit and well. One month prior to presentation, the patient had taken a five-day course of amoxicillin-clavulanic acid for an infected skin cyst. Otherwise, she was only on the oral contraceptive pill and reported minimal alcohol intake. On examination, she was deeply jaundiced, but alert and oriented with no asterixis. She had no stigmata of chronic liver disease, but hepatomegaly extending 3 cm from below the right subcostal margin was evident. Investigations showed: white cell count 13.4 × 10⁹/L (normal 3.6-9.3), haemoglobin 11.8 g/dl (normal 11-15), platelet count 356 × 10⁹/L (normal 170-420), sodium 138 mmol/L (normal 134-144), potassium 3.5 mmol/L (normal 3.5-5.0), creatinine 32 µmol/L (normal 40-75), albumin 30 g/L (normal 35-48), alanine aminotransferase 707 IU/L (normal 15-54), alkaline phosphatase 151 IU/L (normal 30-130), bilirubin 384 µmol/L (normal 7-31) and prothrombin time 27.2 s (normal 11.7-14). Screening for hepatitis A, B, C, E, Epstein-Barr virus, cytomegalovirus and autoimmune hepatitis was negative. Tests for anti-smooth muscle, antinuclear, and anti-liver-kidney microsomal-1 antibodies were negative; immunoglobulin levels and ceruloplasmin levels were normal. Liver ultrasonography demonstrated a liver of normal contour with no biliary dilatation, a normal spleen size and patent vessels. Liver biopsy revealed severe portal interface hepatitis with lobular inflammation and scant plasma cells. Her clinical condition deteriorated in the following days with prothrombin time and bilirubin rising to 56.6 s and 470 µmol/L, respectively. At follow-up after 11 days, her alanine aminotransferase level was 1,931 IU/L. She developed grade 2 hepatic encephalopathy 14 days after presentation, and was listed for a super-urgent liver transplant. Human leucocyte antigen (HLA) typing was performed as a part of preparatory investigations and showed the patient carried the HLA haplotype HLA-DRB1∗15:02-DQB1∗06:01. Following orthotopic transplantation of a deceased donor graft her explant histology revealed severe ongoing hepatitis with multi-acinar necrosis (Fig. 1A and B). This case raised a number of important questions about the diagnosis of drug-induced liver injury and tools available for clinicians to make the best decisions for patient care: In this Grand Rounds article, we will explore these questions, describing the pathophysiology, diagnostic and prognostic biomarkers, and clinical management of drug-induced liver injury. We will also discuss ongoing areas of uncertainty.

Animal models of drug-induced liver injury

Drug-induced liver injury (DILI) presents unique challenges for consumers, clinicians, and regulators. It is the most common cause of acute liver failure in the US. It is also one of the most common reasons for termination of new drugs during pre-clinical testing and withdrawal of new drugs post-marketing. DILI is generally divided into two forms: intrinsic and idiosyncratic. Many of the challenges with DILI are due in large part to poor understanding of the mechanisms of toxicity. Although useful models of intrinsic DILI are available, they are frequently misused. Modeling idiosyncratic DILI presents greater challenges, but promising new models have recently been developed. The purpose of this manuscript is to provide a critical review of the most popular animal models of DILI, and to discuss the future of DILI research.

Identification of a novel metabolite of vildagliptin in humans: Cysteine targets the nitrile moiety to form a thiazoline ring

The dipeptidyl peptidase-4 (DPP-4) inhibitor vildagliptin (VG) is used to treat type 2 diabetes. In rare cases, VG-induced liver injury has been reported. One case report suggested that immune responses were involved in the hepatotoxicity. However, the underlying mechanisms of VG-induced hepatotoxicity are uncertain. In the present study, we investigated whether VG has the potential to covalently bind to macromolecules in cells, a process that could initiate immune-mediated hepatotoxicity. For comparison, M20.7, a major metabolite of VG, and other DPP-4 inhibitors were also evaluated. We found that VG and anagliptin (ANG), which both contain a cyanopyrrolidine moiety, rapidly reacted in non-enzymatic manners on co-incubation with l-cysteine. Both VG and ANG had half-lives of 20-30 min. In contrast, incubation with GSH, rather than l-cysteine, failed to decrease the concentrations of VG or ANG. M20.7, sitagliptin, linagliptin, and alogliptin, having no cyanopyrrolidine moiety, were stable on incubation with l-cysteine or GSH. Structural analysis of the VG- and ANG-cysteine adducts, designated M407 and M487, respectively, revealed that the nitrile moieties of VG and ANG were irreversibly converted to a thiazoline acid. In conclusion, we found that VG and ANG have the potential to covalently bind to a thiol residue of l-cysteine in proteins. Such binding may lead to unpredictable immune responses in humans. l-Cysteine, rather than GSH, would likely be useful to detect the potential for covalent binding that could initiate immune-mediated hepatotoxicity.

Drug-induced liver injury: a safety review

INTRODUCTION

Idiosyncratic drug-induced liver injury (DILI) remains one of the most important causes of drug attrition both in the early phases of clinical drug development and in the postmarketing scenario. This is because, in spite of emerging data on genetic susceptibility variants associated to the risk of hepatotoxicity, the precise identification of the individual who will develop DILI when exposed to a given drug remains elusive.

AREAS COVERED

In this review, we have addressed recent progress made and initiatives taken in the field of DILI from a safety perspective through a comprehensive search of the literature.

EXPERT OPINION

Despite the substantial progress made over this century, new approaches using big data analysis to characterize the true incidence of DILI are needed and to categorize the drugs' hepatotoxic potential. Genetic studies have highlighted the role of the adaptive immune system yet the mechanisms leading adaptation versus progression remain to be elucidated. There is a compelling need for development and qualification of sensitive, specific, and affordable biomarkers in DILI to foster drug development, patient treatment stratification and, improvement of causality assessment methods. Gaining mechanistic insights in DILI is essential to uncover therapeutic targets and design prospective clinical trials with appropriate endpoints.

Biomarkers of drug-induced liver injury: progress and utility in research, medicine, and regulation

INTRODUCTION

The difficulty of understanding and diagnosing drug-induced liver injury (DILI) has led to proliferation of serum and genetic biomarkers. Many applications of these biomarkers have been proposed, including investigation of mechanisms, prediction of DILI during early trials or before initiation of therapy in patients, and diagnosis of DILI during therapy. Areas covered: We review the definition and categories of DILI, describe recent developments in DILI biomarker development, and provide guidance for future directions in DILI biomarker research. Expert commentary: There are major obstacles to DILI biomarker development and implementation, including the low prevalence of idiosyncratic DILI (IDILI), weak associations of IDILI with genetic variants, and lack of specificity of many biomarkers for the liver. Certain serum biomarkers, like miR-122, may have clinical utility in early-presenting patients with either intrinsic or idiosyncratic DILI in the future, while others likely will not find use. Future research should focus on implementation of biomarkers to predict later injury and outcome in early presenters with intrinsic DILI, and on development of biomarkers of adaptation and repair in the liver that can be used to determine if a liver test abnormality is likely to be clinically significant in IDILI.

The use of SAMe in chemotherapy-induced liver injury

Drug-induced liver injury (DILI) remains the most common cause of acute liver failure in the Western world. Chemotherapy is one of the major class of drugs most frequently associated with idiosyncratic DILI. For this reason, patients who receive chemotherapy require careful assessment of liver function prior to treatment to determine which drugs may not be appropriate and which drug doses should be modified. S-adenosylmethionine (SAMe) is an endogenous agent derived from methionine. Its supplementation is effective in the treatment of liver disease, in particular intrahepatic cholestasis (IHC). The target of this review is to analyze the mechanisms of hepatotoxicity of the principal anticancer agents and the role of SAMe in the prevention of this complication.

Advancing Predictive Hepatotoxicity at the Intersection of Experimental, in Silico, and Artificial Intelligence Technologies

Adverse drug reactions, particularly those that result in drug-induced liver injury (DILI), are a major cause of drug failure in clinical trials and drug withdrawals. Hepatotoxicity-mediated drug attrition occurs despite substantial investments of time and money in developing cellular assays, animal models, and computational models to predict its occurrence in humans. Underperformance in predicting hepatotoxicity associated with drugs and drug candidates has been attributed to existing gaps in our understanding of the mechanisms involved in driving hepatic injury after these compounds perfuse and are metabolized by the liver. Herein we assess in vitro, in vivo (animal), and in silico strategies used to develop predictive DILI models. We address the effectiveness of several two- and three-dimensional in vitro cellular methods that are frequently employed in hepatotoxicity screens and how they can be used to predict DILI in humans. We also explore how humanized animal models can recapitulate human drug metabolic profiles and associated liver injury. Finally, we highlight the maturation of computational methods for predicting hepatotoxicity, the untapped potential of artificial intelligence for improving in silico DILI screens, and how knowledge acquired from these predictions can shape the refinement of experimental methods.

Evaluation of the Relevance of DILI Predictive Hypotheses in Early Drug Development: Review of In Vitro Methodologies vs BDDCS Classification

Drug-induced liver injury (DILI) is a major safety concern; it occurs frequently; it is idiosyncratic; it cannot be adequately predicted; and a multitude of underlying mechanisms has been postulated. A number of experimental approaches to predict human DILI have been proposed utilizing in vitro screening such as inhibition of mitochondrial function, hepatobiliary transporter inhibition, reactive metabolite formation with and without covalent binding, and cellular health, but they have achieved only minimal success. Several studies have shown total administered dose alone or in combination with drug lipophilicity to be correlated with a higher risk of DILI. However, it would be best to have a predictive DILI methodology early in drug development, long before the clinical dose is known. Here we discuss the extent to which Biopharmaceutics Drug Disposition Classification System (BDDCS) defining characteristics, independent of knowing actual drug pharmacokinetics/pharmacodynamics and dose, can be used to evaluate prior published predictive proposals. Our results show that BDDCS Class 2 drugs exhibit the highest DILI severity, and that all of the short-lived published methodologies evaluated here, except when daily dose is known, do not yield markedly better predictions than BDDCS. The assertion that extensively metabolized compounds are at higher risk of developing DILI is confirmed, but can be enhanced by differentiating BDDCS Class 2 from Class 1 drugs.

CONCLUSION

Our published analyses suggest that comparison of proposed DILI prediction methodologies with BDDCS classification is a useful tool to evaluate the potential reliability of newly proposed algorithms, although BDDCS classification itself is not sufficiently predictive. Almost all of the predictive DILI metrics do no better than just avoiding BDDCS Class 2 drugs, although some early data with microliver platforms enabling long-enduring metabolic competency show promising results.

Phenylthiomethyl Ketone-Based Fragments Show Selective and Irreversible Inhibition of Enteroviral 3C Proteases

Lead structure discovery mainly focuses on the identification of noncovalently binding ligands. Covalent linkage, however, is an essential binding mechanism for a multitude of successfully marketed drugs, although discovered by serendipity in most cases. We present a concept for the design of fragments covalently binding to proteases. Covalent linkage enables fragment binding unrelated to affinity to shallow protein binding sites and at the same time allows differentiated targeted hit verification and binding location verification through mass spectrometry. We describe a systematic and rational computational approach for the identification of covalently binding fragments from compound collections inhibiting enteroviral 3C protease, a target with high therapeutic potential. By implementing reactive groups potentially forming covalent bonds as a chemical feature in our 3D pharmacophore methodology, covalent binders were discovered by high-throughput virtual screening. We present careful experimental validation of the virtual hits using enzymatic assays and mass spectrometry unraveling a novel, previously unknown irreversible inhibition of the 3C protease by phenylthiomethyl ketone-based fragments. Subsequent synthetic optimization through fragment growing and reactivity analysis against catalytic and noncatalytic cysteines revealed specific irreversible 3C protease inhibition.

Pediatric Intestinal Failure-Associated Liver Disease: Challenges in Identifying Clinically Relevant Biomarkers

BACKGROUND

Intestinal failure-associated liver disease (IFALD) is complex and diagnosed by concurrent use of parenteral nutrition, clinical presentation, and alterations in hepatic biomarkers exclusive of other causes of liver disease. In comparison with individual measures, composite biomarkers may provide a more effective means for assessing disease progression and response to treatment than single parameters. Since IFALD is considered by some to be a type of drug-induced liver injury (DILI), those diagnostic criteria could potentially be used in this population. Using a preexisting database of children treated for IFALD, our aim was to determine if a similar composite biomarker could be applied to this population.

STUDY DESIGN

Adult DILI criteria were applied at baseline, when treatment for IFALD (ie, direct bilirubin ≥2.0 mg/dL) was initiated.

RESULTS

A total of 214 patients with IFALD treated at Boston Children's Hospital were identified; 168 patients were eligible for analysis. Most patients analyzed were male (61%) and preterm (87%). Alkaline phosphatase (ALP) ≥2× upper limit of normal (ULN) captured the least amount of DILI (11%), while γ-glutamyltransferase (GGT) ≥1× ULN accounted for the most (62%). Using adult DILI criteria, 60 (39%) patients with IFALD were found to have DILI. Substituting GGT ≥1× ULN for ALP ≥2× ULN improved the sensitivity, with 105 (69%) of patients meeting at least 1 criterion for DILI.

CONCLUSION

Numerous challenges made it difficult to apply the DILI criteria to children with IFALD. Direct bilirubin, fractionated ALP, and perhaps GGT may be more suitable. Given its complex etiology and the age-based differences due to hepatic immaturity and growth, a more suitable composite marker needs to be developed to assess IFALD in this population.

Drug-Induced Liver Injury: An Institutional Case Series and Review of Literature

Drug-induced liver injury (DILI) is the most common cause of acute liver failure in the USA. DILI can be broadly classified as Intrinsic and Idiosyncratic. Identifying predictors and at-risk patients are challenging but can have a substantial clinical implication. This case report series demonstrates the importance of valproic acid, fluconazole, and amiodarone as potential hepatoxic agents of drug-induced liver injury leading to acute hepatic failure. The causality in all cases was established by Roussel Uclaf Causality Assessment Method/Council for International Organizations of Medical Sciences score and Naranjo Algorithm. Obesity, hypo-perfusion state, and concurrent hepatotoxic agent might identify at-risk patients. Further studies are required to understand the risk factors.