Evidence-based selection of training compounds for use in the mechanism-based integrated prediction of drug-induced liver injury in man

The current test systems employed by pharmaceutical industry are poorly predictive for drug-induced liver injury (DILI). The ‘MIP-DILI’ project addresses this situation by the development of innovative preclinical test systems which are both mechanism-based and of physiological, pharmacological and pathological relevance to DILI in humans. An iterative, tiered approach with respect to test compounds, test systems, bioanalysis and systems analysis is adopted to evaluate existing models and develop new models that can provide validated test systems with respect to the prediction of specific forms of DILI and further elucidation of mechanisms. An essential component of this effort is the choice of compound training set that will be used to inform refinement and/or development of new model systems that allow prediction based on knowledge of mechanisms, in a tiered fashion. In this review, we focus on the selection of MIP-DILI training compounds for mechanism-based evaluation of non-clinical prediction of DILI. The selected compounds address both hepatocellular and cholestatic DILI patterns in man, covering a broad range of pharmacologies and chemistries, and taking into account available data on potential DILI mechanisms (e.g. mitochondrial injury, reactive metabolites, biliary transport inhibition, and immune responses). Known mechanisms by which these compounds are believed to cause liver injury have been described, where many if not all drugs in this review appear to exhibit multiple toxicological mechanisms. Thus, the training compounds selection offered a valuable tool to profile DILI mechanisms and to interrogate existing and novel in vitro systems for the prediction of human DILI

Investigative safety strategies to improve success in drug development

Understanding and reducing attrition rate remains a key challenge in drug development. Preclinical and clinical safety issues still represent about 40% of drug discontinuation, of which cardiac and liver toxicities are the leading reasons. Reducing attrition rate can be achieved by various means, starting with a comprehensive evaluation of the potential safety issues associated to the primary target followed by an evaluation of undesirable secondary targets. To address these risks, a risk mitigation plan should be built at very early development stages, using a panel of in silico, in vitro, and in vivo models. While most pharmaceutical companies have developed robust safety strategies to de-risk genotoxicity and cardiotoxicity issues, partly driven by regulatory requirements; safety issues affecting other organs or systems, such as the central nervous system, liver, kidney, or gastro-intestinal system are less commonly addressed during early drug development. This paper proposes some de-risking strategies that can be applied to these target organ systems, including the use of novel biomarkers that can be easily integrated in both preclinical and clinical studies. Experiments to understand the mechanisms’ underlying toxicity are also important. Two examples are provided to demonstrate how such mechanistic studies can impact drug development. Novel trends in investigative safety are reviewed, such as computational modeling, mitochondrial toxicity assessment, and imaging technologies. Ultimately, understanding the predictive value of non-clinical safety testing and its translatability to humans will enable to optimize assays in order to address the key objectives of the drug discovery process, i.e., hazard identification, risk assessment, and mitigation

Managing the challenge of drug-induced liver injury: a roadmap for the development and deployment of preclinical predictive models

Drug-induced liver injury (DILI) is a patient-specific, temporal, multifactorial pathophysiological process that cannot yet be recapitulated in a single in vitro model. Current preclinical testing regimes for the detection of human DILI thus remain inadequate. A systematic and concerted research effort is required to address the deficiencies in current models and to present a defined approach towards the development of new or adapted model systems for DILI prediction. This Perspective defines the current status of available models and the mechanistic understanding of DILI, and proposes our vision of a roadmap for the development of predictive preclinical models of human DILI

Distribution of pituitary adenylate cyclase-activating polypeptide and pituitary adenylate cyclase-activating polypeptide type I receptor mRNA in the chicken brain

To map in detail the brain areas in which pituitary adenylate cyclase-activating polypeptide (PACAP) may play a significant role in birds, the distribution of PACAP and PACAP type I receptor (PAC(1)-R) mRNA was examined throughout the entire chicken brain by using in situ hybridization histochemistry. Widespread distribution of both PACAP and its receptor mRNA was found. The telencephalic areas where the most intense signals for PACAP mRNA were found included the hyperstriatum accessorium, the hippocampus, and the archistriatum. In the diencephalon, a group of neurons that highly expressed PACAP mRNA was observed from the anterior medial hypothalamic nucleus to the inferior hypothalamic nucleus. Moderate expression was found in the paraventricular nucleus and the preoptic region. A second large group of neurons containing PACAP message was found within the nucleus dorsolateralis anterior thalami and extended caudally to the area around the nucleus ovoidalis and the nucleus paramedianus internus thalami. Furthermore, expression of PACAP message was observed within the bed nucleus of the pallial commissure, nucleus spiriformis medialis, optic tectum, cerebellar cortex, olfactory bulbs, and several nuclei within the brainstem (dorsal vagal and parabrachial complex, reticular formation). The highest expression of PAC(1)-R mRNA was found in the dorsal telencephalon, olfactory bulbs, lateral septum, optic tectum, cerebellum, and throughout the hypothalamus and thalamus. The presence of PACAP and PAC(1)-R mRNA in a variety of brain areas in birds suggests that PACAP mediates several physiologically important processes in addition to regulating the activity of the pituitary gland.status: publishe

Evaluation of Impedance-Based Label-Free Technology as a Tool for Pharmacology and Toxicology Investigations

The use of label-free technologies based on electrical impedance is becoming more and more popular in drug discovery. Indeed, such a methodology allows the continuous monitoring of diverse cellular processes, including proliferation, migration, cytotoxicity and receptor-mediated signaling. The objective of the present study was to further assess the usefulness of the real-time cell analyzer (RTCA) and, in particular, the xCELLigence platform, in the context of early drug development for pharmacology and toxicology investigations. In the present manuscript, four cellular models were exposed to 50 compounds to compare the cell index generated by RTCA and cell viability measured with a traditional viability assay. The data revealed an acceptable correlation (ca. 80%) for both cell lines (i.e., HepG2 and HepaRG), but a lack of correlation (ca. 55%) for the primary human and rat hepatocytes. In addition, specific RTCA profiles (signatures) were generated when HepG2 and HepaRG cells were exposed to calcium modulators, antimitotics, DNA damaging and nuclear receptor agents, with a percentage of prediction close to 80% for both cellular models. In a subsequent experiment, HepG2 cells were exposed to 81 proprietary UCB compounds known to be genotoxic or not. Based on the DNA damaging signatures, the RTCA technology allowed the detection of ca. 50% of the genotoxic compounds (n = 29) and nearly 100% of the non-genotoxic compounds (n = 52). Overall, despite some limitations, the xCELLigence platform is a powerful and reliable tool that can be used in drug discovery for toxicity and pharmacology studies

Sequence and distribution of pro-opiomelanocortin in the pituitary and the brain of the chicken (Gallus gallus)

Although pro-opiomelanocortin (POMC) is a well-known hormone precursor in many species, molecular information about avian POMCs is still relatively scarce. In a former study (Berghman et al., [1998] Mol Cell Endocrinol. 142:119-130) the nucleotide and amino acid sequence of N-terminal POMC in the chicken were reported. To complete the nucleotide sequence of the precursor, rapid amplification of 3' and 5' cDNA end reactions were performed and the polymerase chain reaction (PCR) products were cloned and sequenced. The chicken POMC coding region appears to consist of 678 base pairs in the pituitary and also in the hypothalamus, as assessed by reverse transcriptase PCR. Overall nucleotide sequence homology with other species ranges from 41% (in bovine) to 57% (in rat). The distribution of the POMC mRNA in pituitary and brain was analyzed by in situ hybridization by using 33P-labelled oligonucleotides. Expression of POMC mRNA in the pituitary was restricted to the cephalic lobe, whereas in the brain, the signal was limited to the hypothalamic region. As assessed by Northern blot analysis, the length of the POMC mRNA in both the pituitary and the hypothalamus was approximately 1,200 nucleotides. By using antisera to N-terminal POMC, alpha-melanotropin and beta-endorphin, POMC-containing cells were observed in the cephalic lobe of the pituitary and immunopositive perikarya were localized in the infundibular nucleus and median eminence of the hypothalamus. Immunoreactive fibers were found in the preoptic area and in the medial basal hypothalamus surrounding the third ventricle and more dorsally in the thalamus. Double-staining experiments in the pituitary clearly indicated a complete overlap of the signals generated by these antisera.status: publishe

Molecular cloning and differential expression of the cat immediate early gene c-fos

Recently, the effect of binocular central retinal lesions on the expression of immediate early genes in the visual system of adult cats was demonstrated using in situ hybridization and immunocytochemistry. The present study was undertaken to quantify cat c-fos mRNA expression differences in the cat primary visual cortex after sensory deafferentation. Prior to quantification, DNA fragments obtained using reverse transcription-polymerase chain reaction (RT-PCR) in combination with rapid amplification of complementary DNA ends (RACE) were cloned and sequenced. This provided us with the necessary sequence(1) information to prepare cat-specific c-fos primers for the development of a new quantitative RT-PCR assay. We optimized a reverse transcription-competitive polymerase chain reaction (RT-cPCR) method with a heterologous DNA fragment (competitor) as external standard to quantify relative amounts of cat c-fos mRNA expression levels. Internal standardization was accomplished by quantifying, in a parallel RT-cPCR, a well-characterized housekeeping gene, glyceraldehyde-3-phosphate dehydrogenase (GAPDH). This cat-specific RT-cPCR assay allowed us to measure c-fos mRNA expression levels in central and peripheral regions of primary visual cortex in normal and retinal lesion cats.status: publishe

A cross-industry survey on photosafety evaluation of pharmaceuticals after implementation of ICH S10.

A cross-industry survey was conducted by EFPIA/IQ DruSafe in 2018 to provide information on photosafety evaluation of pharmaceuticals after implementation of ICH S10. This survey focused on the strategy utilized for photosafety risk assessment, the design of nonclinical (in vitro and in vivo) and clinical evaluations, the use of exposure margins in risk assessment, and regulatory interactions. The survey results indicated that a staged approach for phototoxicity assessment has been widely accepted by regulatory authorities globally. The OECD-based 3T3 NRU Phototoxicity Test is the most frequently used in vitro approach. Modifications to this assay suggested by ICH S10 are commonly applied. For in-vitro-positives, substantial margins from in vitro IC50 values under irradiation to Cmax (clinical) have enabled further development without the need for additional photosafety data. In vivo phototoxicity studies typically involve dosing rodents and exposing skin and eyes to simulated sunlight, and subsequently evaluating at least the skin for erythema and edema. However, no formal guidelines exist and protocols are less standardized across companies. A margin-of-safety approach (based on Cmax at NOAEL) has been successfully applied to support clinical development. Experience with dedicated clinical phototoxicity studies was limited, perhaps due to effective de-risking approaches employed based on ICH S10

Investigative safety strategies to improve success in drug development

Understanding and reducing attrition rate remains a key challenge in drug development. Preclinical and clinical safety issues still represent about 40% of drug discontinuation, of which cardiac and liver toxicities are the leading reasons. Reducing attrition rate can be achieved by various means, starting with a comprehensive evaluation of the potential safety issues associated to the primary target followed by an evaluation of undesirable secondary targets. To address these risks, a risk mitigation plan should be built at very early development stages, using a panel of in silico, in vitro, and in vivo models. While most pharmaceutical companies have developed robust safety strategies to de-risk genotoxicity and cardiotoxicity issues, partly driven by regulatory requirements; safety issues affecting other organs or systems, such as the central nervous system, liver, kidney, or gastro-intestinal system are less commonly addressed during early drug development. This paper proposes some de-risking strategies that can be applied to these target organ systems, including the use of novel biomarkers that can be easily integrated in both preclinical and clinical studies. Experiments to understand the mechanisms’ underlying toxicity are also important. Two examples are provided to demonstrate how such mechanistic studies can impact drug development. Novel trends in investigative safety are reviewed, such as computational modeling, mitochondrial toxicity assessment, and imaging technologies. Ultimately, understanding the predictive value of non-clinical safety testing and its translatability to humans will enable to optimize assays in order to address the key objectives of the drug discovery process, i.e. hazard identification, risk assessment, and mitigation.info:eu-repo/semantics/publishe

Investigative safety strategies to improve success in drug development

Understanding and reducing attrition rate remains a key challenge in drug development. Preclinical and clinical safety issues still represent about 40% of drug discontinuation, of which cardiac and liver toxicities are the leading reasons. Reducing attrition rate can be achieved by various means, starting with a comprehensive evaluation of the potential safety issues associated to the primary target followed by an evaluation of undesirable secondary targets. To address these risks, a risk mitigation plan should be built at very early development stages, using a panel of in silico, in vitro, and in vivo models. While most pharmaceutical companies have developed robust safety strategies to de-risk genotoxicity and cardiotoxicity issues, partly driven by regulatory requirements; safety issues affecting other organs or systems, such as the central nervous system, liver, kidney, or gastro-intestinal system are less commonly addressed during early drug development. This paper proposes some de-risking strategies that can be applied to these target organ systems, including the use of novel biomarkers that can be easily integrated in both preclinical and clinical studies. Experiments to understand the mechanisms’ underlying toxicity are also important. Two examples are provided to demonstrate how such mechanistic studies can impact drug development. Novel trends in investigative safety are reviewed, such as computational modeling, mitochondrial toxicity assessment, and imaging technologies. Ultimately, understanding the predictive value of non-clinical safety testing and its translatability to humans will enable to optimize assays in order to address the key objectives of the drug discovery process, i.e. hazard identification, risk assessment, and mitigation.info:eu-repo/semantics/publishe