The metabolic fate of fenclozic acid in chimeric mice with a humanized liver

Investigation of Biotransformation Pathways in a Chimeric Mouse with a Humanized Liver

Xenobiotics, including drugs, undergo metabolism to facilitate detoxification and excretion. Predicting a compound's metabolic fate before clinical trials is crucial for efficacy and safety. The existing methods rely on in vitro systems and in vivo animal testing. In vitro systems do not replicate the complexity of in vivo systems, and differences in biotransformation pathways between humans and nonclinical species may occur; thus, accurate predictions of human-specific drug metabolism are not always achieved. The aim of this study was to evaluate whether a chimeric mouse with a humanized liver, specifically the PXB-mouse, can mimic human metabolic profiles. PXB-mice have livers engrafted with up to 95% human hepatocytes. The biotransformation of 12 different small-molecule drugs were evaluated in PXB-mice (through analysis of blood and urine) and compared with the metabolism by hepatocytes from humans and mice and, when available, literature reports on human in vivo metabolism. The detected metabolites included major Phase I and II transitions, such as hydroxylation, and N- and O-dealkylation and glucuronidation. The metabolic patterns of the PXB-mice closely matched human in vivo data. It is also worth noting that the human hepatocytes formed most of the circulating metabolites, indicating that hepatocytes provide reliable predictions of human metabolic pathways. Thus, for drugs with human biotransformation pathways that are not observed in nonclinical species, the PXB-mouse model can be valuable in predicting human-specific metabolism.

The Disposition and Metabolism of Bempedoic Acid, a Potent Inhibitor of ATP Citrate Lyase, in Healthy Human Subjects

The disposition and metabolism of bempedoic acid, a selective inhibitor of ATP citrate lyase, were examined in healthy male subjects. After a single administration of [14C] bempedoic acid (240 mg, 113 μCi) oral solution, mean concentrations of total radioactivity in plasma as a function of time indicated absorption was rapid with peak concentrations achieved at 1 hour after dose administration. Radioactivity was decreased in a multiexponential fashion with an estimated elimination half-life of 26.0 hours. Radiolabeled dose was predominantly recovered in urine (62.1% of dose) and a smaller amount in feces (25.4% of dose). Bempedoic acid was extensively metabolized with 1.6%-3.7% of dose excreted unchanged in urine and feces combined. Overall, the major clearance route of bempedoic acid is metabolism by uridine 5'-diphosphate glucuronosyltransferases. Metabolism in hepatocyte cultures of human and nonclinical species were generally in agreement with clinical metabolite profiles. Pooled plasma samples were characterized by the presence of bempedoic acid (ETC-1002), which accounted for 59.3% of total plasma radioactivity, ESP15228 (M7; a reversible keto metabolite of bempedoic acid), and their respective glucuronide conjugates. The acyl glucuronide of bempedoic acid (M6) represented 23%-36% of radioactivity in plasma and accounted for approximately 37% of dose excreted in urine. In feces, the majority of radioactivity was associated with a co-eluting mixture of a carboxylic acid metabolite of bempedoic acid (M2a), a taurine conjugate of bempedoic acid (M2c), and hydroxymethyl-ESP15228 (M2b), which collectively accounted for 3.1%-22.9% of bempedoic acid dose across subjects. SIGNIFICANCE STATEMENT: This study characterizes the disposition and metabolism of bempedoic acid, an inhibitor of ATP citrate lyase for hypercholesterolemia. This work provides further understanding of bempedoic acid clinical pharmacokinetics and clearance pathways in adult subjects.

Investigation of the Pharmacokinetics and Metabolic Fate of Fasiglifam (TAK-875) in Male and Female Rats Following Oral and Intravenous Administration

The metabolism and pharmacokinetics of fasiglifam (TAK-875, 2-[(3S)-6-[[3-[2,6-dimethyl-4-(3-methylsulfonylpropoxy)phenyl]phenyl]methoxy]-2,3-dihydro-1-benzofuran-3-yl]acetic acid), a selective free fatty acid receptor 1 (FFAR1)/GPR40 agonist, were studied following intravenous (5 mg/kg) and oral administration (10 and 50 mg/kg) to male and female Sprague Dawley rats.Following intravenous dosing at 5 mg/kg, peak observed plasma concentrations of 8.8/9.2 μg/ml were seen in male and female rats respectively.Following oral dosing, peak plasma concentrations at 1 h of ca. 12.4/12.9 μg/ml for 10 mg/kg and 76.2/83.7 μg/ml for 50 mg/kg doses were obtained for male and female rats respectively. Drug concentrations then declined in the plasma of both sexes with t_1/2's of 12.4 (male) and 11.2 h (female). Oral bioavailability was estimated to be 85-120% in males and females at both dose levels.Urinary excretion was low, but in a significant sex-related difference, female rats eliminated ca. 10-fold more drug-related material by this route.Fasiglifam was the principal drug-related compound in plasma, with 15 metabolites, including the acyl glucuronide, also detected. In addition to previously identified metabolites, a novel biotransformation, that produced a side-chain shortened metabolite via elimination of CH₂ from the acetyl side chain was noted with implications for drug toxicity.

Preclinical models of idiosyncratic drug-induced liver injury (iDILI): Moving towards prediction

Idiosyncratic drug-induced liver injury (iDILI) encompasses the unexpected harms that prescription and non-prescription drugs, herbal and dietary supplements can cause to the liver. iDILI remains a major public health problem and a major cause of drug attrition. Given the lack of biomarkers for iDILI prediction, diagnosis and prognosis, searching new models to predict and study mechanisms of iDILI is necessary. One of the major limitations of iDILI preclinical assessment has been the lack of correlation between the markers of hepatotoxicity in animal toxicological studies and clinically significant iDILI. Thus, major advances in the understanding of iDILI susceptibility and pathogenesis have come from the study of well-phenotyped iDILI patients. However, there are many gaps for explaining all the complexity of iDILI susceptibility and mechanisms. Therefore, there is a need to optimize preclinical human in vitro models to reduce the risk of iDILI during drug development. Here, the current experimental models and the future directions in iDILI modelling are thoroughly discussed, focusing on the human cellular models available to study the pathophysiological mechanisms of the disease and the most used in vivo animal iDILI models. We also comment about in silico approaches and the increasing relevance of patient-derived cellular models.

Advanced preclinical models for evaluation of drug-induced liver injury - consensus statement by the European Drug-Induced Liver Injury Network [PRO-EURO-DILI-NET]

Drug-induced liver injury (DILI) is a major cause of acute liver failure (ALF) and one of the leading indications for liver transplantation in Western societies. Given the wide use of both prescribed and over the counter drugs, DILI has become a major health issue for which there is a pressing need to find novel and effective therapies. Although significant progress has been made in understanding the molecular mechanisms underlying DILI, our incomplete knowledge of its pathogenesis and inability to predict DILI is largely due to both discordance between human and animal DILI in preclinical drug development and a lack of models that faithfully recapitulate complex pathophysiological features of human DILI. This is exemplified by the hepatotoxicity of acetaminophen (APAP) overdose, a major cause of ALF because of its extensive worldwide use as an analgesic. Despite intensive efforts utilising current animal and in vitro models, the mechanisms involved in the hepatotoxicity of APAP are still not fully understood. In this expert Consensus Statement, which is endorsed by the European Drug-Induced Liver Injury Network, we aim to facilitate and outline clinically impactful discoveries by detailing the requirements for more realistic human-based systems to assess hepatotoxicity and guide future drug safety testing. We present novel insights and discuss major players in APAP pathophysiology, and describe emerging in vitro and in vivo pre-clinical models, as well as advanced imaging and in silico technologies, which may improve prediction of clinical outcomes of DILI.

Advancements in stem cell-derived hepatocyte-like cell models for hepatotoxicity testing

Drug-induced liver injury (DILI) is one of the leading causes of clinical trial failures and high drug attrition rates. Currently, the commonly used hepatocyte models include primary human hepatocytes (PHHs), animal models, and hepatic cell lines. However, these models have disadvantages that include species-specific differences or inconvenient cell extraction methods. Therefore, a novel, inexpensive, efficient, and accurate model that can be applied to drug screening is urgently needed. Owing to their self-renewable ability, source abundance, and multipotent competence, stem cells are stable sources of drug hepatotoxicity screening models. Because 3D culture can mimic the in vivo microenvironment more accurately than can 2D culture, the former is commonly used for hepatocyte culture and drug screening. In this review, we introduce the different sources of stem cells used to generate hepatocyte-like cells and the models for hepatotoxicity testing that use stem cell-derived hepatocyte-like cells.

Acyl glucuronide reactivity in perspective

Acyl glucuronidation is a common metabolic fate for acidic drugs and their metabolites and, because these metabolites are reactive, they have been linked to adverse drug reactions (ADRs) and drug withdrawals. However, alternative routes of metabolism leading to reactive metabolites (e.g., oxidations and acyl-CoA thioesters) mean that unambiguous proof that acyl glucuronides are toxic is lacking. Here, we review the synthesis and reactivity of these metabolites, and describe the use of molecular modelling and in vitro and in vivo reactivity assessment of acyl glucuronide reactivity. Based on the emerging structure-dependent differences in reactivity and protein adduction methods for risk assessment for acyl glucuronide-forming acid drugs or drug candidates in drug discovery/development are suggested.

Art of Making Artificial Liver: Depicting Human Liver Biology and Diseases in Mice

Advancement in both bioengineering and cell biology of the liver led to the establishment of the first-generation humanized liver chimeric mouse (HLCM) model in 2001. The HLCM system was initially developed to satisfy the necessity for a convenient and physiologically representative small animal model for studies of hepatitis B virus and hepatitis C virus infection. Over the last two decades, the HLCM system has substantially evolved in quality, production capacity, and utility, thereby growing its versatility beyond the study of viral hepatitis. Hence, it has been increasingly employed for a variety of applications including, but not limited to, the investigation of drug metabolism and pharmacokinetics and stem cell biology. To date, more than a dozen distinctive HLCM systems have been established, and each model system has similarities as well as unique characteristics, which are often perplexing for end-users. Thus, this review aims to summarize the history, evolution, advantages, and pitfalls of each model system with the goal of providing comprehensive information that is necessary for researchers to implement the ideal HLCM system for their purposes. Furthermore, this review article summarizes the contribution of HLCM and its derivatives to our mechanistic understanding of various human liver diseases, its potential for novel applications, and its current limitations.