A modified multiparametric assay using HepaRG cells for predicting the degree of drug-induced liver injury risk

Control compounds for preclinical drug-induced liver injury assessment: Consensus-driven systematic review by the ProEuroDILI network

BACKGROUND & AIMS

Idiosyncratic drug-induced liver injury (DILI) is a complex and unpredictable event caused by drugs, and herbal or dietary supplements. Early identification of human hepatotoxicity at preclinical stages remains a major challenge, in which the selection of validated in vitro systems and test drugs has a significant impact. In this systematic review, we analyzed the compounds used in hepatotoxicity assays and established a list of DILI-positive and -negative control drugs for validation of in vitro models of DILI, supported by literature and clinical evidence and endorsed by an expert committee from the COST Action ProEuroDILI Network (CA17112).

METHODS

Following 2020 PRISMA guidelines, original research articles focusing on DILI which used in vitro human models and performed at least one hepatotoxicity assay with positive and negative control compounds, were included. Bias of the studies was assessed by a modified 'Toxicological Data Reliability Assessment Tool'.

RESULTS

A total of 51 studies (out of 2,936) met the inclusion criteria, with 30 categorized as reliable without restrictions. Although there was a broad consensus on positive compounds, the selection of negative compounds lacked clarity. 2D monoculture, short exposure times and cytotoxicity endpoints were the most tested, although there was no consensus on drug concentrations.

CONCLUSIONS

Extensive analysis highlighted the lack of agreement on control compounds for in vitro DILI assessment. Following comprehensive in vitro and clinical data analysis together with input from the expert committee, an evidence-based consensus-driven list of 10 positive and negative control drugs for validation of in vitro models of DILI is proposed.

IMPACT AND IMPLICATIONS

Prediction of human toxicity early in the drug development process remains a major challenge, necessitating the development of more physiologically relevant liver models and careful selection of drug-induced liver injury (DILI)-positive and -negative control drugs to better predict the risk of DILI associated with new drug candidates. Thus, this systematic study has crucial implications for standardizing the validation of new in vitro models of DILI. By establishing a consensus-driven list of positive and negative control drugs, the study provides a scientifically justified framework for enhancing the consistency of preclinical testing, thereby addressing a significant challenge in early hepatotoxicity identification. Practically, these findings can guide researchers in evaluating safety profiles of new drugs, refining in vitro models, and informing regulatory agencies on potential improvements to regulatory guidelines, ensuring a more systematic and efficient approach to drug safety assessment.

Relationships between the Structure and Severe Drug-Induced Liver Injury for Low, Medium, and High Doses of Drugs

Assessment of structure-activity relationships (SARs) for predicting severe drug-induced liver injury (DILI) is essential since in vivo and in vitro preclinical methods cannot detect many druglike compounds disrupting liver functions. To date, plenty of SAR models for the prediction of DILI have been developed; however, none of them considered the route of drug administration and daily dose, which may introduce significant bias into prediction results. We have created a dataset of 617 drugs with parenteral and oral administration routes and consistent information on DILI severity. We have found a clear relationship between route, dose, and DILI severity. According to SAR, nearly 40% of moderate- and non-DILI-causing drugs would cause severe DILI if they were administered at high oral doses. We have proposed the following approach to predict severe DILI. New compounds recommended to be used at low oral doses (<∼10 mg daily), or parenterally, can be considered not causing severe DILI. DILI for compounds administered at medium oral doses (∼10-100 mg daily; 22.2% of drugs under consideration) can be considered unpredictable because reasonable SAR models were not obtained due to the small size and heterogeneity of the corresponding dataset. The DILI potential of the compounds recommended to be used at high oral doses (more than ∼100 mg daily) can be estimated using SAR modeling. The balanced accuracy of the approach calculated by a 10-fold cross-validation procedure is 0.803. The developed approach can be used to estimate severe DILI for druglike compounds proposed to use at low and high oral doses or parenterally at the early stages of drug development.

Micropatterned Coculture With 3T3-J2 Fibroblasts Enhances Hepatic Functions and Drug Screening Utility of HepaRG Cells

Human liver models are useful for assessing compound metabolism/toxicity; however, primary human hepatocyte (PHH) lots are limited and highly variable in quality/viability. In contrast, cell lines, such as HepaRG, are cheaper and more reproducible surrogates for initial compound screening; however, hepatic functions and sensitivity for drug outcomes need improvement. Here, we show that HepaRGs cocultured with murine embryonic 3T3-J2 fibroblasts, previously shown to induce PHH functions, could address such limitations. We either micropatterned HepaRGs or seeded them "randomly" onto collagen-coated plates before 3T3-J2 coculture. Micropatterned cocultures (HepaRG-MPCCs) secreted 2- to 4-fold more albumin and displayed more stable cytochrome P450 activities than HepaRG conventional confluent monocultures (HepaRG-CCs) and HepaRG micropatterned hepatocytes (HepaRG-MPHs) for 4 weeks, even when excluding dimethyl sulfoxide from the medium. Furthermore, HepaRG-MPCCs had the most albumin-only positive cells (hepatic), lowest cytokeratin 19 (CK19)-only positive cells (cholangiocytic), and highest mean albumin intensity per cell than HepaRG random cocultures and monocultures; however, 80%-84% of HepaRGs remained bipotential (albumin+/CK19+) across all models. The 3T3-J2s also induced higher albumin in HepaRG spheroids than HepaRG-only spheroids. Additionally, although rifampin induced CYP3A4 in HepaRG-MPCCs and HepaRG-CCs, only HepaRG-MPCCs showed the dual omeprazole-mediated CYP1A2/3A4 induction as with PHHs. Lastly, when treated for 6 days with 47 drugs and evaluated for albumin and ATP to make binary hepatotoxicity calls, HepaRG-MPCCs displayed a sensitivity of 54% and specificity of 100% (70%/100% in PHH-MPCCs), whereas HepaRG-CCs misclassified several hepatotoxins. Ultimately, HepaRG-MPCCs could be a more cost-effective and reproducible model than PHHs for executing a tier 1 compound screen.

Evaluation of Parent- and Metabolite-Induced Mitochondrial Toxicities Using CYP-Introduced HepG2 cells

Mitochondrial toxicity is an important factor to predict drug-induced liver injury (DILI). Previous studies have focused predominantly on mitochondrial toxicities due to parent forms, and no study has adequately evaluated metabolite-induced mitochondrial toxicity. Moreover, previous studies have used HepG2 cells, which lack many cytochrome P450 (CYP) genes. To overcome this problem, CYP-introduced HepG2 cells were constructed using several gene transfer technologies, including adenoviruses and plasmids. However, these methods only led to a transient expression of CYP genes. In the present study, usefulness of four CYPs introduced-HepG2 (TC-Hep) cells previously constructed through mammalian artificial chromosome technology were examined, especially from the perspective of mitochondrial toxicity. First, we evaluated the effects of known compounds, such as rotenone and flutamide, on mitochondrial toxicity and cell death in TC-Hep cells cultured in galactose conditions. Expectedly, rotenone-induced cell death ameliorated because rotenone was metabolized by CYPs into inactive form(s) and flutamide-induced cell death increased in TC-Hep cells. Second, we evaluated five compounds that caused liver injury in clinical phase and were discontinued during pharmaceutical development. The present in vitro tool suggested that three of the five compounds caused metabolite-induced mitochondrial toxicities. In conclusion, the present in vitro tool could easily and inexpensively detect metabolite-induced mitochondrial toxicity; hence, it can be useful for predicting DILI in preclinical phase.

Models of Idiosyncratic Drug-Induced Liver Injury

Drug-induced liver injury (DILI) is a leading cause of attrition during the early and late stages of drug development and after a drug is marketed. DILI is generally classified as either intrinsic or idiosyncratic. Intrinsic DILI is dose dependent and predictable (e.g., acetaminophen toxicity). However, predicting the occurrence of idiosyncratic DILI, which has a very low incidence and is associated with severe liver damage, is difficult because of its complex nature and the poor understanding of its mechanism. Considering drug metabolism and pharmacokinetics, we established experimental animal models of DILI for 14 clinical drugs that cause idiosyncratic DILI in humans, which is characterized by the formation of reactive metabolites and the involvement of both innate and adaptive immunity. On the basis of the biomarker data obtained from the animal models, we developed a cell-based assay system that predicts the potential risks of drugs for inducing DILI. These findings increase our understanding of the mechanisms of DILI and may help predict and prevent idiosyncratic DILI due to certain drugs.

The evolution of strategies to minimise the risk of human drug-induced liver injury (DILI) in drug discovery and development

Early identification of toxicity associated with new chemical entities (NCEs) is critical in preventing late-stage drug development attrition. Liver injury remains a leading cause of drug failures in clinical trials and post-approval withdrawals reflecting the poor translation between traditional preclinical animal models and human clinical outcomes. For this reason, preclinical strategies have evolved over recent years to incorporate more sophisticated human in vitro cell-based models with multi-parametric endpoints. This review aims to highlight the evolution of the strategies adopted to improve human hepatotoxicity prediction in drug discovery and compares/contrasts these with recent activities in our lab. The key role of human exposure and hepatic drug uptake transporters (e.g. OATPs, OAT2) is also elaborated.

A head-to-head Caco-2 assay comparison of the mechanisms of action of the intestinal permeation enhancers: SNAC and sodium caprate (C10)

Salcaprozate sodium (SNAC) and sodium caprate (C₁₀) are the two leading intestinal permeation enhancers (PEs) in oral peptide formulations in clinical trials. There is debate over their mechanism of action on intestinal epithelia. The aims were: (i) to compare their effects on the barrier function by measuring transepithelial electrical resistance (TEER), permeability of FITC-4000 (FD4) across Caco-2 monolayers, and on immunohistochemistry of tight junction (TJ)-associated proteins; and (ii) to compare cellular parameters using conventional end-point cytotoxicity assays and quantitative high content analysis (HCA) of multiple sub-lethal parameters in Caco-2 cells. C₁₀ (8.5 mM) reversibly reduced TEER and increased FD4 permeability across monolayers, whereas SNAC had no effects on either parameter except at cytotoxic concentrations. C₁₀ exposure induced reorganization of three TJ proteins, whereas SNAC only affected claudin-5 localization. High concentrations of C₁₀ and SNAC were required to cause end-point toxicology changes in vitro. SNAC was less potent than C₁₀ at inducing lysosomal and nuclear changes and plasma membrane perturbation. In parallel, HCA revealed that both agents displayed detergent-like features that reflect initial membrane fluidization followed by changes in intracellular parameters. In conclusion, FD4 permeability increases in monolayers in response to C₁₀ were in the range of concentrations that altered end-point cytotoxicity and HCA parameters. For SNAC, while HCA parameters were also altered in a similar overall pattern as C₁₀, they did not lead to increased paracellular flux. These assays show that both agents are primarily surfactants, but C₁₀ has additional TJ-opening effects. While these in vitro assays illucidate their epithelial mechanism of action, clinical experience suggests that they over-estimate their toxicology in the dynamic intestinal environment.

Dr. Daniel Acosta and In Vitro toxicology at the U.S. Food and Drug Administration's National Center for Toxicological Research

For the past five years, Dr. Daniel Acosta has served as the Deputy Director of Research at the National Center for Toxicological Research (NCTR), a principle research laboratory of the U.S. Food and Drug Administration (FDA). Over his career at NCTR, Dr. Acosta has had a major impact on developing and promoting the use of in vitro assays in regulatory toxicity and product safety assessments. As Dr. Acosta nears his retirement we have dedicated this paper to his many accomplishments at the NCTR. Described within this paper are some of the in vitro studies that have been conducted under Dr. Acosta's leadership. These studies include toxicological assessments involving developmental effects, and the development and application of in vitro reproductive, heart, liver, neurological and airway cell and tissue models.

A cell-based assay using HepaRG cells for predicting drug-induced phospholipidosis

The utility of HepaRG cells as an in vitro cell-based assay system for predicting drug-induced phospholipidosis (PLD) was investigated. In experiment 1, 10 PLD-positive compounds and 11 PLD-negative compounds were selected. HepaRG cells were treated with each compound for 48 hr. In experiment 2, loratadine and desloratadine, a major metabolite of loratadine, were used to assess metabolic activation for PLD. HepaRG cells were treated with loratadine and desloratadine in the presence or absence of 500 μM 1-aminobenzotriazole (ABT), a broad CYP inhibitor, for 48 hr. After treatment with compounds in experiments 1 and 2, the relative fluorescence intensity (RFI) was measured using LYSO-ID Red dye to assess the PLD induction. In experiment 1, our cell-based assay system using HepaRG cells exhibited 100% sensitivity and 100% specificity for predicting drug-induced PLD. In experiment 2, loratadine increased the RFI in the PLD assay. However, the increase in the RFI was not observed in co-treatment with loratadine and ABT. In addition, desloratadine increased the RFI in the presence and absence of ABT. These results suggested that metabolic activation of loratadine may contribute to PLD in HepaRG cells. We newly demonstrated that HepaRG cells have a high ability for predicting drug-induced PLD. In addition, we newly showed that HepaRG cells may predict drug-induced PLD mediated by metabolic activation of loratadine. Thus, a cell-based assay system using HepaRG cells is a useful model for predicting drug-induced PLD.

Aqueous extract of Phragmitis rhizoma ameliorates myelotoxicity of docetaxel in vitro and in vivo

Background

A variety of anticancer chemotherapeutics induce adverse side effects including myelotoxicity. Dried roots of Phragmites communis Trinius, Phragmitis rhizoma, have been clinically used in traditional folk medicine to relieve various symptoms like fever. In this study, we evaluated the protective effect of the aqueous extract of Phragmitis rhizoma (EPR) against docetaxel-induced myelotoxicity in vitro and in vivo.

Methods

The in vitro myelo-protective effect of EPR was evaluated using the colony forming unit (CFU) assay with hematopoietic progenitor cells. The in vivo efficacy of EPR was evaluated in myelosuppressed C57BL/6 male mice which were induced by repeated intraperitoneal injections of 30 mg/kg docetaxel for 3 times. EPR was orally administered for 4 days to docetaxel-induced myelosuppressed C57BL/6 male mice which were induced by intraperitoneal injection of 30 mg/kg docetaxel for 3 times: Group 1 (vehicle control, n = 10), Group 2 (docetaxel plus vehicle, n = 10), Group 3 (docetaxel plus EPR 30 mg/kg, n = 10), Group 4 (docetaxel plus EPR 100 mg/kg, n = 10) and Group 5 (docetaxel plus EPR 300 mg/kg, n = 10). Whole blood counts were measured automatically, and immune organs were histologically examined. Expression of immunomodulatory cytokines was measured by quantitative real-time polymerase chain reaction or enzyme-linked immunosorbent assay. The toxicity of EPR itself was evaluated in normal human cell lines including IMR-90, foreskin fibroblast and human umbilical vein endothelial cells. The hepatotoxicity of EPR was predicted by multi-parametric assays involving cell viability, caspase 3/7 activity, GSH contents and LDH leakage using the HepaRG hepatic cell line.

Results

Co-treatment of EPR or its major component, p-hydroxycinnamic acid, increased the numbers of hematopoietic CFU counts in the docetaxel-induced in vitro myelotoxicity assay system. The in vitro protective effect of EPR against docetaxel toxicity was replicated in a myelosuppressed animal model: white blood cells, neutrophils, lymphocytes and red blood cells rebounded; bone marrow niche and structural integrity of the thymus were preserved; and the expression of immune-stimulating cytokines including IL3, IL6, SCF and GM-CSF was enhanced. Furthermore, EPR and p-hydroxycinnamic acid promoted the proliferation of primary splenocytes and thymocytes. In the toxicity assays, no remarkable signs related with toxicity were observed in all tested normal human cells and HepaRG.

Conclusions

EPR has the potential to ameliorate docetaxel-mediated myelotoxicity in both in vitro and in vivo models. However, the identification of the responsible active components and the precise underlying myelo-protective mechanism of EPR need to be elucidated before novel drug development using EPR can precede.

Electronic supplementary material

The online version of this article (doi:10.1186/s12906-017-1890-1) contains supplementary material, which is available to authorized users.