Hepatic failure and lactic acidosis due to fialuridine (FIAU), an investigational nucleoside analogue for chronic hepatitis B

Challenges and opportunities of translating animal research into human trials in Ethiopia

BACKGROUND AND OBJECTIVES

Although the goal of translational research is to bring biomedical knowledge from the laboratory to clinical trial and therapeutic products for improving health, this goal has not been well achieved as often as desired because of many barriers documented in different countries. Therefore, the aim of this study was to investigate the challenges and opportunities of translating animal research into human trials in Ethiopia.

METHODS

A descriptive qualitative study, using in-depth interviews, was conducted in which preclinical and clinical trial researchers who have been involved in animal research or clinical trials as principal investigator were involved. Data were analyzed using inductive thematic process.

RESULTS

Six themes were emerged for challenges: lack of financial and human capacity, inadequate infrastructure, operational obstacles and poor research governance, lack of collaboration, lack of reproducibility of results and prolonged ethical and regulatory approval processes. Furthermore, three themes were synthesized for opportunities: growing infrastructure and resources, improved human capacity and better administrative processes and initiatives for collaboration.

CONCLUSION AND RECOMMENDATIONS

The study found that the identified characteristics/features are of high importance either to hurdle or enable the practice of translating animal research into human trials. The study suggests that there should be adequate infrastructure and finance, human capacity building, good research governance, improved ethical and regulatory approval process, multidisciplinary collaboration, and incentives and recognition for researchers to overcome the identified challenges and allow translating of animal research into human trials to proceed more efficiently.

Role of liver biopsy in the management of idiosyncratic DILI

Drug-induced liver injury (DILI) presents unique challenges in clinical practice. While some types of DILI are mild and resolve quickly after removing the drug, other situations are more complex, with competing aetiologies or underlying liver disease. Guidelines from professional societies agree that the liver biopsy retains a role in understanding and managing DILI in certain situations. Liver biopsy allows characterization of the histological pattern of injury as well as assessment of severity. Inflammatory infiltrates, bile duct injury or loss and vascular injury are all revealed by liver biopsy. Communication between the hepatopathologist and clinical team with clinicopathological correlation of the findings is necessary for the best determination of causality and differentiation from other diseases of exclusion, like autoimmune hepatitis and graft-versus-host disease. This review highlights important aspects of the role of liver biopsy in DILI evaluation.

Beyond the hype and toward application: liver complex in vitro models in preclinical drug safety

INTRODUCTION

Drug induced Liver-Injury (DILI) is a leading cause of drug attrition and complex in vitro models (CIVMs), including three dimensional (3D) spheroids, 3D bio printed tissues and flow-based systems, could improve preclinical prediction. Although CIVMs have demonstrated good sensitivity and specificity in DILI detection their adoption remains limited.

AREAS COVERED

This article describes DILI, the challenges with its prediction and the current strategies and models that are being used. It reviews data from industry-FDA collaborations and strategic partnerships and finishes with an outlook of CIVMs in preclinical toxicity testing. Literature searches were performed using PubMed and Google Scholar while product information was collected from manufacturer websites.

EXPERT OPINION

Liver CIVMs are promising models for predicting DILI although, a decade after their introduction, routine use by the pharmaceutical industry is limited. To accelerate their adoption, several industry-regulator-developer partnerships or consortia have been established to guide the development and qualification. Beyond this, liver CIVMs should continue evolving to capture greater immunological mimicry while partnering with computational approaches to deliver systems that change the paradigm of predicting DILI.

Creatine kinase elevation in chronic hepatitis B patients with telbivudine therapy: influence of telbivudine plasma concentration and single nucleotide polymorphisms of TK2, RRM2B, and NME4

PURPOSE

To study the correlations of genetic variants of telbivudine phosphorylase kinases and telbivudine plasma concentration with creatine kinase elevation in chronic hepatitis B patients who received telbivudine.

METHODS

An observational study was performed in China chronic hepatitis B patients receiving telbivudine therapy at 600 mg once daily. Plasma concentration was measured 12 h after taking telbivudine using ultra-performance liquid chromatography-tandem mass spectrometry and SNPs located in RRM2B, TK2, and NME4 was detected by MALDI-TOF mass spectrometry. All statistical analyses were performed with R 4.3.1 and all graphs were drawn by Origin 2023b and P value < 0.05 was considered statistically significant.

RESULTS

A total of 140 patients receiving telbivudine therapy were recruited with a median plasma concentration of 952.49 (781.07-1238.98) ng/mL. The value of plasma concentration was proportional to the grade of creatine kinase elevation and the best telbivudine plasma concentration threshold to discriminate the grade 3/4 CK elevation was 1336.61 ng/mL. Multivariate analysis revealed that plasma concentration and rs3826160 were the independent risk factor of telbivudine-induced creatine kinase elevation. Patients with TC and CC genotype in rs3826160 not only had a higher incidence of creatine kinase elevation but also a higher plasma concentration than TT genotype carriers.

CONCLUSION

Chronic hepatitis B patients with TC and CC genotype in rs3826160 have high telbivudine plasma concentration are at risk of elevated creatine kinase.

Innovative therapeutic strategies to overcome radioresistance in breast cancer

Despite a comparatively favorable prognosis relative to other malignancies, breast cancer continues to significantly impact women's health globally, partly due to its high incidence rate. A critical factor in treatment failure is radiation resistance - the capacity of tumor cells to withstand high doses of ionizing radiation. Advancements in understanding the cellular and molecular mechanisms underlying radioresistance, coupled with enhanced characterization of radioresistant cell clones, are paving the way for the development of novel treatment modalities that hold potential for future clinical application. In the context of combating radioresistance in breast cancer, potential targets of interest include long non-coding RNAs (lncRNAs), micro RNAs (miRNAs), and their associated signaling pathways, along with other signal transduction routes amenable to pharmacological intervention. Furthermore, technical, and methodological innovations, such as the integration of hyperthermia or nanoparticles with radiotherapy, have the potential to enhance treatment responses in patients with radioresistant breast cancer. This review endeavors to provide a comprehensive survey of the current scientific landscape, focusing on novel therapeutic advancements specifically addressing radioresistant breast cancer.

Efficient hepatocyte differentiation of primary human hepatocyte-derived organoids using three dimensional nanofibers (HYDROX) and their possible application in hepatotoxicity research

Human liver organoids are in vitro three dimensionally (3D) cultured cells that have a bipotent stem cell phenotype. Translational research of human liver organoids for drug discovery has been limited by the challenge of their low hepatic function compared to primary human hepatocytes (PHHs). Various attempts have been made to develop functional hepatocyte-like cells from human liver organoids. However, none have achieved the same level of hepatic functions as PHHs. We here attempted to culture human liver organoids established from cryopreserved PHHs (PHH-derived organoids), using HYDROX, a chemically defined 3D nanofiber. While the proliferative capacity of PHH-derived organoids was lost by HYDROX-culture, the gene expression levels of drug-metabolizing enzymes were significantly improved. Enzymatic activities of cytochrome P450 3A4 (CYP3A4), CYP2C19, and CYP1A2 in HYDROX-cultured PHH-derived organoids (Org-HYDROX) were comparable to those in PHHs. When treated with hepatotoxic drugs such as troglitazone, amiodarone and acetaminophen, Org-HYDROX showed similar cell viability to PHHs, suggesting that Org-HYDROX could be applied to drug-induced hepatotoxicity tests. Furthermore, Org-HYDROX maintained its functions for up to 35 days and could be applied to chronic drug-induced hepatotoxicity tests using fialuridine. Our findings demonstrated that HYDROX could possibly be a novel biomaterial for differentiating human liver organoids towards hepatocytes applicable to pharmaceutical research.

PET/CT and SPECT/CT for Infection in Joints and Bones: An Overview and Future Directions

Infections of the bones and joints, if misdiagnosed, may result in serious morbidity and even mortality. A prompt diagnosis followed by appropriate management may reduce the socioeconomic impact of bone and joint infections. Morphologic imaging such as ultrasound and plain radiographs form the first line investigations, however, in early infections findings may be negative or nonspecific. Nuclear medicine imaging techniques play a complementary role to morphologic imaging in the diagnosis of bone and joint infections. The availability of hybrid systems (SPECT/CT, SPECT/MRI, PET/CT or PET/MRI) offers improved specificity with ability to assess the extent of infection. Bone scans are useful as a gatekeeper wherein negative scans rule out sepsis with a good accuracy, however positive scans are nondiagnostic and more specific tracers should be considered. These include the use of labeled white blood cells and antigranulocyte antibodies. Various qualitative and quantitative interpretation criteria have been suggested to improve the specificity of the scans. PET has better image resolution and 18F-FDG is the major tracer for PET imaging with applications in oncology and inflammatory/infective disorders. It has demonstrated improved sensitivity over the SPECT based tracers, however, still suffers from lack of specificity. 18F-FDG PET has been used to monitor therapy in bone and joint infections. Other less studied, noncommercialized SPECT and PET tracers such as 111In-Biotin, 99mTc-Ubiquicidin, 18F-Na-Fluoride, 18F-labeled white blood cells and 124I-Fialuridine to name a few have shown great promise, however, their role in various bone and joint infections has not been established. Hybrid imaging with PET or PET/MRI offers huge potential for improving diagnostics in infections of the joints and bones.

Under-representation of the WHO African region in clinical trials of interventions against hepatitis B virus infection

The WHO African region bears a disproportionate burden of morbidity and mortality related to chronic hepatitis B virus (HBV) infection and accounts for an estimated 70% of new HBV infections worldwide. We investigated the extent to which HBV clinical trials represented populations in this region by searching the WHO International Clinical Trials Registry Platform and ClinicalTrials.gov for interventional clinical trials published in English between database inception and May 29, 2023, using the search term "Hepatitis B". We identified 1804 unique clinical trials, of which 18 (1·0%) recorded involvement of the WHO African region. There is no evidence that the number of HBV clinical trials in this region has improved over time. The diversity of new interventions and industry sponsorship in the WHO African region were low, with trials of HBV comparing poorly with those of other endemic infectious diseases (eg, malaria, HIV, and SARS-CoV-2). HBV research and clinical trial investigations have neglected the WHO African region, leading to profound health inequities. HBV clinical trials are urgently needed to evaluate the efficacy of newly discovered therapeutics and to ensure that interventions can be equitably distributed and deployed as they become available.

RNA interference in the era of nucleic acid therapeutics

Two decades of research on RNA interference (RNAi) have transformed a breakthrough discovery in biology into a robust platform for a new class of medicines that modulate mRNA expression. Here we provide an overview of the trajectory of small-interfering RNA (siRNA) drug development, including the first approval in 2018 of a liver-targeted siRNA interference (RNAi) therapeutic in lipid nanoparticles and subsequent approvals of five more RNAi drugs, which used metabolically stable siRNAs combined with N-acetylgalactosamine ligands for conjugate-based liver delivery. We also consider the remaining challenges in the field, such as delivery to muscle, brain and other extrahepatic organs. Today's RNAi therapeutics exhibit high specificity, potency and durability, and are transitioning from applications in rare diseases to widespread, chronic conditions.

Shaping the future of antiviral Treatment: Spotlight on Nucleobase-Containing drugs and their revolutionary impact

Nucleobases serve as essential molecular frameworks present in both natural and synthetic compounds that exhibit notable antiviral activity. Through molecular modifications, novel nucleobase-containing drugs (NCDs) have been developed, exhibiting enhanced antiviral activity against a wide range of viruses, including the recently emerged SARS‑CoV‑2. This article provides a detailed examination of the significant advancements in NCDs from 2015 till current, encompassing various aspects concerning their mechanisms of action, pharmacology and antiviral properties. Additionally, the article discusses antiviral prodrugs relevant to the scope of this review. It fills in the knowledge gap by examining the structure-activity relationship and trend of NCDs as therapeutics against a diverse range of viral diseases, either as approved drugs, clinical candidates or as early-stage development prospects. Moreover, the article highlights on the status of this field of study and addresses the prevailing limitations encountered.

Protecting Human and Animal Health: The Road from Animal Models to New Approach Methods

Animals and animal models have been invaluable for our current understanding of human and animal biology, including physiology, pharmacology, biochemistry, and disease pathology. However, there are increasing concerns with continued use of animals in basic biomedical, pharmacological, and regulatory research to provide safety assessments for drugs and chemicals. There are concerns that animals do not provide sufficient information on toxicity and/or efficacy to protect the target population, so scientists are utilizing the principles of replacement, reduction, and refinement (the 3Rs) and increasing the development and application of new approach methods (NAMs). NAMs are any technology, methodology, approach, or assay used to understand the effects and mechanisms of drugs or chemicals, with specific focus on applying the 3Rs. Although progress has been made in several areas with NAMs, complete replacement of animal models with NAMs is not yet attainable. The road to NAMs requires additional development, increased use, and, for regulatory decision making, usually formal validation. Moreover, it is likely that replacement of animal models with NAMs will require multiple assays to ensure sufficient biologic coverage. The purpose of this manuscript is to provide a balanced view of the current state of the use of animal models and NAMs as approaches to development, safety, efficacy, and toxicity testing of drugs and chemicals. Animals do not provide all needed information nor do NAMs, but each can elucidate key pieces of the puzzle of human and animal biology and contribute to the goal of protecting human and animal health. SIGNIFICANCE STATEMENT: Data from traditional animal studies have predominantly been used to inform human health safety and efficacy. Although it is unlikely that all animal studies will be able to be replaced, with the continued advancement in new approach methods (NAMs), it is possible that sometime in the future, NAMs will likely be an important component by which the discovery, efficacy, and toxicity testing of drugs and chemicals is conducted and regulatory decisions are made.

Assessing the mitochondrial safety profile of the molnupiravir active metabolite, β-d-N4-hydroxycytidine (NHC), in the physiologically relevant HepaRG model

Background

β-d-N4-Hydroxycytidine (NHC) is the active metabolite of molnupiravir, a broad-spectrum antiviral approved by the MHRA for COVID-19 treatment. NHC induces lethal mutagenesis of the SARS-CoV-2 virus, undergoing incorporation into the viral genome and arresting viral replication. It has previously been reported that several nucleoside analogues elicit off-target inhibition of mitochondrial DNA (mtDNA) or RNA replication. Although NHC does not exert these effects in HepG2 cells, HepaRG are proven to be advantageous over HepG2 for modelling nucleoside analogue-induced mitochondrial dysfunction. Therefore, the objective of this work was to assess the mitotoxic potential of NHC in HepaRG cells, a model more closely resembling physiological human liver.

Methods

Differentiated HepaRG cells were exposed to 1-60 μM NHC for 3-14 days to investigate effects of sub-, supra-, and clinically-relevant exposures (in the UK, molnupiravir for COVID-19 is indicated for 5 days and reported Cmax is 16 μM). Following drug incubation, cell viability, mtDNA copy number, mitochondrial protein expression, and mitochondrial respiration were assessed.

Results

NHC induced minor decreases in cell viability at clinically relevant exposures, but did not decrease mitochondrial protein expression. The effects on mtDNA were variable, but typically copy number was increased. At supra-clinical concentrations (60 μM), NHC reduced mitochondrial respiration, but did not appear to induce direct electron transport chain dysfunction.

Conclusions

Overall, NHC does not cause direct mitochondrial toxicity in HepaRG cells at clinically relevant concentrations, but may induce minor cellular perturbations. As HepaRG cells have increased physiological relevance, these findings provide additional assurance of the mitochondrial safety profile of NHC.

A mechanistic biomarker investigation of fialuridine hepatotoxicity using the chimeric TK-NOG Hu-liver mouse model and in vitro micropatterned hepatocyte cocultures

Fialuridine (FIAU) is a nucleoside-based drug that caused liver failure and deaths in a human clinical trial that were not predicted by nonclinical safety studies. A recent report concluded that a TK-NOG humanized liver (hu-liver) mouse model detected human-specific FIAU liver toxicity, and broader use of that model could improve drug safety testing. We further evaluated this model at similar dose levels to assess FIAU sensitivity and potential mechanistic biomarkers. Although we were unable to reproduce the marked acute liver toxicity with two separate studies (including one with a "sensitized" donor), we identified molecular biomarkers reflecting the early stages of FIAU mitochondrial toxicity, which were not seen with its stereoisomer (FIRU). Dose dependent FIAU-induced changes in hu-liver mice included more pronounced reductions in mitochondrial to nuclear DNA (mtDNA/nucDNA) ratios in human hepatocytes compared to mouse hepatocytes and kidneys of the same animals. FIAU treatment also triggered a p53 transcriptional response and opposing changes in transcripts of nuclear- and mitochondrial-encoded mitochondrial proteins. The time dependent accumulation of FIAU into mtDNA is consistent with the ≥9-week latency of liver toxicity observed for FIAU in the clinic. Similar changes were observed in an in vitro micro-patterned hepatocyte coculture system. In addition, FIAU-dependent mtDNA/nucDNA ratio and transcriptional alterations, especially reductions in mitochondrially encoded transcripts, were seen in livers of non-engrafted TK-NOG and CD-1 mice dosed for a shorter period. Conclusion: These mechanistic biomarker findings can be leveraged in an in vitro model and in a more routine preclinical model (CD-1 mice) to identify nucleosides with such a FIAU-like mitochondrial toxicity mechanistic liability potential. Further optimization of the TK-NOG hu-liver mouse model is necessary before broader adoption for drug safety testing.

Corydalis and Drug-Induced Liver Injury: A Series of 2 Cases

Corydalis is an herbal plant found in Asian countries. Research has demonstrated multiple health benefits. It has also been implicated in drug-induced liver injury. Cannabis dispensaries market a sleep aid which has corydalis as an active ingredient. We present 2 cases of corydalis-induced hepatotoxicity. An asymptomatic female patient exhibited a rise and fall of her transaminases coinciding with the consumption and rechallenge of this sleep aid. A man with symptoms consistent with liver dysfunction began taking the same sleep aid. With discontinuance, his liver function returned to normal. These 2 clinical cases provide evidence for corydalis-induced liver injury.

3D bioprinting of dECM-incorporated hepatocyte spheroid for simultaneous promotion of cell-cell and -ECM interactions

The cell spheroid technology, which greatly enhances cell-cell interactions, has gained significant attention in the development of in vitro liver models. However, existing cell spheroid technologies still have limitations in improving hepatocyte-extracellular matrix (ECM) interaction, which have a significant impact on hepatic function. In this study, we have developed a novel bioprinting technology for decellularized ECM (dECM)-incorporated hepatocyte spheroids that could enhance both cell-cell and -ECM interactions simultaneously. To provide a biomimetic environment, a porcine liver dECM-based cell bio-ink was developed, and a spheroid printing process using this bio-ink was established. As a result, we precisely printed the dECM-incorporated hepatocyte spheroids with a diameter of approximately 160-220 μm using primary mouse hepatocyte (PMHs). The dECM materials were uniformly distributed within the bio-printed spheroids, and even after more than 2 weeks of culture, the spheroids maintained their spherical shape and high viability. The incorporation of dECM also significantly improved the hepatic function of hepatocyte spheroids. Compared to hepatocyte-only spheroids, dECM-incorporated hepatocyte spheroids showed approximately 4.3- and 2.5-fold increased levels of albumin and urea secretion, respectively, and a 2.0-fold increase in CYP enzyme activity. These characteristics were also reflected in the hepatic gene expression levels of ALB, HNF4A, CPS1, and others. Furthermore, the dECM-incorporated hepatocyte spheroids exhibited up to a 1.8-fold enhanced drug responsiveness to representative hepatotoxic drugs such as acetaminophen, celecoxib, and amiodarone. Based on these results, it can be concluded that the dECM-incorporated spheroid printing technology has great potential for the development of highly functional in vitro liver tissue models for drug toxicity assessment.

Addressing the Clinical Importance of Equilibrative Nucleoside Transporters in Drug Discovery and Development

The US Food and Drug Administration (FDA), European Medicines Agency (EMA), and Pharmaceuticals and Medical Devices Agency (PMDA) guidances on small-molecule drug-drug interactions (DDIs), with input from the International Transporter Consortium (ITC), recommend the evaluation of nine drug transporters. Although other clinically relevant drug uptake and efflux transporters have been discussed in ITC white papers, they have been excluded from further recommendation by the ITC and are not included in current regulatory guidances. These include the ubiquitously expressed equilibrative nucleoside transporters (ENT) 1 and ENT2, which have been recognized by the ITC for their potential role in clinically relevant nucleoside analog drug interactions for patients with cancer. Although there is comparatively limited clinical evidence supporting their role in DDI risk or other adverse drug reactions (ADRs) compared with the nine highlighted transporters, several in vitro and in vivo studies have identified ENT interactions with non-nucleoside/non-nucleotide drugs, in addition to nucleoside/nucleotide analogs. Some noteworthy examples of compounds that interact with ENTs include cannabidiol and selected protein kinase inhibitors, as well as the nucleoside analogs remdesivir, EIDD-1931, gemcitabine, and fialuridine. Consequently, DDIs involving the ENTs may be responsible for therapeutic inefficacy or off-target toxicity. Evidence suggests that ENT1 and ENT2 should be considered as transporters potentially involved in clinically relevant DDIs and ADRs, thereby warranting further investigation and regulatory consideration.

Remdesivir increases mtDNA copy number causing mild alterations to oxidative phosphorylation

SARS-CoV-2 causes the severe respiratory disease COVID-19. Remdesivir (RDV) was the first fast-tracked FDA approved treatment drug for COVID-19. RDV acts as an antiviral ribonucleoside (adenosine) analogue that becomes active once it accumulates intracellularly. It then diffuses into the host cell and terminates viral RNA transcription. Previous studies have shown that certain nucleoside analogues unintentionally inhibit mitochondrial RNA or DNA polymerases or cause mutational changes to mitochondrial DNA (mtDNA). These past findings on the mitochondrial toxicity of ribonucleoside analogues motivated us to investigate what effects RDV may have on mitochondrial function. Using in vitro and in vivo rodent models treated with RDV, we observed increases in mtDNA copy number in Mv1Lu cells (35.26% increase ± 11.33%) and liver (100.27% increase ± 32.73%) upon treatment. However, these increases only resulted in mild changes to mitochondrial function. Surprisingly, skeletal muscle and heart were extremely resistant to RDV treatment, tissues that have preferentially been affected by other nucleoside analogues. Although our data suggest that RDV does not greatly impact mitochondrial function, these data are insightful for the treatment of RDV for individuals with mitochondrial disease.

An unusual case of heart failure due to ANCA-negative vasculitis: A case report and focused review of the literature

Key Clinical Message

Heart failure due to ANCA-negative vasculitis, is a rare potentially life-threatening manifestation of ANCA vasculitis. Therefore, physicians must always pay attention to this manifestation for proper disease diagnosis and treatment.

Abstract

Less than 10% of primary vasculitides cause cardiac dysfunction, with Takayasu's arteritis, polyarteritis nodosa, and eosinophilic granulomatosis with polyangiitis being the most common cases. However, any cardiac tissue can be affected by ANCA vasculitis. We present a case of heart failure with reduced ventricular ejection fraction due to ANCA negative-vasculitis.

In vitro to in vivo extrapolation and high-content imaging for simultaneous characterization of chemically induced liver steatosis and markers of hepatotoxicity

Chemically induced steatosis is characterized by lipid accumulation associated with mitochondrial dysfunction, oxidative stress and nucleus distortion. New approach methods integrating in vitro and in silico models are needed to identify chemicals that may induce these cellular events as potential risk factors for steatosis and associated hepatotoxicity. In this study we used high-content imaging for the simultaneous quantification of four cellular markers as sentinels for hepatotoxicity and steatosis in chemically exposed human liver cells in vitro. Furthermore, we evaluated the results with a computational model for the extrapolation of human oral equivalent doses (OED). First, we tested 16 reference chemicals with known capacities to induce cellular alterations in nuclear morphology, lipid accumulation, mitochondrial membrane potential and oxidative stress. Then, using physiologically based pharmacokinetic modeling and reverse dosimetry, OEDs were extrapolated from data of any stimulated individual sentinel response. The extrapolated OEDs were confirmed to be within biologically relevant exposure ranges for the reference chemicals. Next, we tested 14 chemicals found in food, selected from thousands of putative chemicals on the basis of structure-based prediction for nuclear receptor activation. Amongst these, orotic acid had an extrapolated OED overlapping with realistic exposure ranges. Thus, we were able to characterize known steatosis-inducing chemicals as well as data-scarce food-related chemicals, amongst which we confirmed orotic acid to induce hepatotoxicity. This strategy addresses needs of next generation risk assessment and can be used as a first chemical prioritization hazard screening step in a tiered approach to identify chemical risk factors for steatosis and hepatotoxicity-associated events.

Modeling drug-induced liver injury and screening for anti-hepatofibrotic compounds using human PSC-derived organoids

Preclinical models that can accurately predict the toxicity and efficacy of candidate drugs to human liver tissue are in urgent need. Human liver organoid (HLO) derived from human pluripotent stem cells offers a possible solution. Herein, we generated HLOs, and demonstrated the utility of these HLOs in modeling a diversity of phenotypes associated with drug-induced liver injury (DILI), including steatosis, fibrosis, and immune responses. Phenotypic changes in HLOs after treatment with tool compounds such as acetaminophen, fialuridine, methotrexate, or TAK-875 showed high concordance with human clinical data in drug safety testings. Moreover, HLOs were able to model liver fibrogenesis induced by TGFβ or LPS treatment. We further devised a high-content analysis system, and established a high-throughput anti-fibrosis drug screening system using HLOs. SD208 and Imatinib were identified that can significantly suppress fibrogenesis induced by TGFβ, LPS, or methotrexate. Taken together, our studies demonstrated the potential applications of HLOs in drug safety testing and anti-fibrotic drug screening.

Molnupiravir: From Hope to Epic Fail?

Molnupiravir has been the first oral antiviral authorized for COVID-19 outpatients, reporting extraordinary sales and preserved in vitro efficacy against Omicron sublineages so far. However, it has recently been associated with very poor clinical efficacy, the risk of creating novel SARS-CoV-2 variants of concern, and long-term risk for mutagenicity in humans. The latter two are severe concerns, especially in the indicated population, i.e., long-replicating, immunodeficient patients. We conclude that, at this point, alternative antivirals should be preferred over molnupiravir.

Human Immunodeficiency Virus Infection-Associated Cardiomyopathy and Heart Failure

The landscape of human immunodeficiency virus (HIV) epidemiology and treatment is ever-changing, with the widespread and evolving use of antiretroviral therapy (ART). With timely ART, people living with HIV (PLWH) are nearing the life expectancies and the functionality of the general population; nevertheless, the effects of HIV and ART on cardiovascular health remain under investigation. The pathophysiology of HIV-related cardiomyopathy and heart failure (HF) have historically been attributed to systemic inflammation and changes in cardiometabolic function and cardiovascular architecture. Importantly, newer evidence suggests that ART also plays a role in modulating the process of HIV-related cardiomyopathy and HF. In the short term, newer highly active ART (HAART) seems to have cardioprotective effects; however, emerging data on the long-term cardiovascular outcomes of certain HAART medications, i.e., protease inhibitors, raise concerns about the potential adverse effects of these drugs in the clinical course of HIV-related HF. As such, the traditional phenotypes of dilated cardiomyopathy and left ventricular systolic failure that are associated with HIV-related heart disease are incrementally being replaced with increasing rates of diastolic dysfunction and ischemic heart disease. Moreover, recent studies have found important links between HIV-related HF and other clinical and biochemical entities, including depression, which further complicate cardiac care for PLWH. Considering these trends in the era of ART, the traditional paradigms of HIV-related cardiomyopathy and HF are being called into question, as is the therapeutic role of interventions such as ventricular assist devices and heart transplantation. In all, the mechanisms of HIV-related myocardial damage and the optimal approaches to the prevention and the treatment of cardiomyopathy and HF in PLWH remain under investigation.

Mechanisms of Post-critical Illness Cardiovascular Disease

Prolonged critical care stays commonly follow trauma, severe burn injury, sepsis, ARDS, and complications of major surgery. Although patients leave critical care following homeostatic recovery, significant additional diseases affect these patients during and beyond the convalescent phase. New cardiovascular and renal disease is commonly seen and roughly one third of all deaths in the year following discharge from critical care may come from this cluster of diseases. During prolonged critical care stays, the immunometabolic, inflammatory and neurohumoral response to severe illness in conjunction with resuscitative treatments primes the immune system and parenchymal tissues to develop a long-lived pro-inflammatory and immunosenescent state. This state is perpetuated by persistent Toll-like receptor signaling, free radical mediated isolevuglandin protein adduct formation and presentation by antigen presenting cells, abnormal circulating HDL and LDL isoforms, redox and metabolite mediated epigenetic reprogramming of the innate immune arm (trained immunity), and the development of immunosenescence through T-cell exhaustion/anergy through epigenetic modification of the T-cell genome. Under this state, tissue remodeling in the vascular, cardiac, and renal parenchymal beds occurs through the activation of pro-fibrotic cellular signaling pathways, causing vascular dysfunction and atherosclerosis, adverse cardiac remodeling and dysfunction, and proteinuria and accelerated chronic kidney disease.

An Engineered Protein-Based Building Block (Albumin Methacryloyl) for Fabrication of a 3D In Vitro Cryogel Model

Drug-induced liver injury (DILI) is a leading cause of attrition in drug development or withdrawal; current animal experiments and traditional 2D cell culture systems fail to precisely predict the liver toxicity of drug candidates. Hence, there is an urgent need for an alternative in vitro model that can mimic the liver microenvironments and accurately detect human-specific drug hepatotoxicity. Here, for the first time we propose the fabrication of an albumin methacryloyl cryogel platform inspired by the liver’s microarchitecture via emulating the mechanical properties and extracellular matrix (ECM) cues of liver. Engineered crosslinkable albumin methacryloyl is used as a protein-based building block for fabrication of albumin cryogel in vitro models that can have potential applications in 3D cell culture and drug screening. In this work, protein modification, cryogelation, and liver ECM coating were employed to engineer highly porous three-dimensional cryogels with high interconnectivity, liver-like stiffness, and liver ECM as artificial liver constructs. The resulting albumin-based cryogel in vitro model provided improved cell–cell and cell–material interactions and consequently displayed excellent liver functional gene expression, being conducive to detection of fialuridine (FIAU) hepatotoxicity.

Three-dimensional (3D) liver cell models - a tool for bridging the gap between animal studies and clinical trials when screening liver accumulation and toxicity of nanobiomaterials

Despite the exciting properties and wide-reaching applications of nanobiomaterials (NBMs) in human health and medicine, their translation from bench to bedside is slow, with a predominant issue being liver accumulation and toxicity following systemic administration. In vitro 2D cell-based assays and in vivo testing are the most popular and widely used methods for assessing liver toxicity at pre-clinical stages; however, these fall short in predicting toxicity for NBMs. Focusing on in vitro and in vivo assessment, the accurate prediction of human-specific hepatotoxicity is still a significant challenge to researchers. This review describes the relationship between NBMs and the liver, and the methods for assessing toxicity, focusing on the limitations they bring in the assessment of NBM hepatotoxicity as one of the reasons defining the poor translation for NBMs. We will then present some of the most recent advances towards the development of more biologically relevant in vitro liver methods based on tissue-mimetic 3D cell models and how these could facilitate the translation of NBMs going forward. Finally, we also discuss the low public acceptance and limited uptake of tissue-mimetic 3D models in pre-clinical assessment, despite the demonstrated technical and ethical advantages associated with them.

Engineering complexity in human tissue models of cancer

Major progress in the understanding and treatment of cancer have tremendously improved our knowledge of this complex disease and improved the length and quality of patients' lives. Still, major challenges remain, in particular with respect to cancer metastasis which still escapes effective treatment and remains responsible for 90% of cancer related deaths. In recent years, the advances in cancer cell biology, oncology and tissue engineering converged into the engineered human tissue models of cancer that are increasingly recapitulating many aspects of cancer progression and response to drugs, in a patient-specific context. The complexity and biological fidelity of these models, as well as the specific questions they aim to investigate, vary in a very broad range. When selecting and designing these experimental models, the fundamental question is "how simple is complex enough" to accomplish a specific goal of cancer research. Here we review the state of the art in developing and using the human tissue models in cancer research and developmental drug screening. We describe the main classes of models providing different levels of biological fidelity and complexity, discuss their advantages and limitations, and propose a framework for designing an appropriate model for a given study. We close by outlining some of the current needs, opportunities and challenges in this rapidly evolving field.

An in silico pipeline for the discovery of multitarget ligands: A case study for epi-polypharmacology based on DNMT1/HDAC2 inhibition

The search for novel therapeutic compounds remains an overwhelming task owing to the time-consuming and expensive nature of the drug development process and low success rates. Traditional methodologies that rely on the one drug-one target paradigm have proven insufficient for the treatment of multifactorial diseases, leading to a shift to multitarget approaches. In this emerging paradigm, molecules with off-target and promiscuous interactions may result in preferred therapies. In this study, we developed a general pipeline combining machine learning algorithms and a deep generator network to train a dual inhibitor classifier capable of identifying putative pharmacophoric traits. As a case study, we focused on dual inhibitors targeting DNA methyltransferase 1 (DNMT) and histone deacetylase 2 (HDAC2), two enzymes that play a central role in epigenetic regulation. We used this approach to identify dual inhibitors from a novel large natural product database in the public domain. We used docking and atomistic simulations as complementary approaches to establish the ligand-interaction profiles between the best hits and DNMT1/HDAC2. By using the combined ligand- and structure-based approaches, we discovered two promising novel scaffolds that can be used to simultaneously target both DNMT1 and HDAC2. We conclude that the flexibility and adaptability of the proposed pipeline has predictive capabilities of similar or derivative methods and is readily applicable to the discovery of small molecules targeting many other therapeutically relevant proteins.

Can preclinical drug development help to predict adverse events in clinical trials?

The development of novel therapeutics is associated with high rates of attrition, with unexpected adverse events being a major cause of failure. Serious adverse events have led to organ failure, cancer development and deaths that were not expected outcomes in clinical trials. These life-threatening events were not identified during therapeutic development due to the lack of preclinical safety tests that faithfully represented human physiology. We highlight the successful application of several novel technologies, including high-throughput screening, organs-on-chips, microbiome-containing drug-testing platforms and humanised mouse models, for mechanistic studies and prediction of toxicity. We propose the incorporation of similar preclinical tests into future drug development to reduce the likelihood of hazardous therapeutics entering later-stage clinical trials.

Of men and mice: Human X-linked retinoschisis and fidelity in mouse modeling

X-linked Retinoschisis (XLRS) is an early-onset transretinal dystrophy, often with a prominent macular component, that affects males and generally spares heterozygous females because of X-linked recessive inheritance. It results from loss-of-function RS1 gene mutations on the X-chromosome. XLRS causes bilateral reduced acuities from young age, and on clinical exam and by ocular coherence tomography (OCT) the neurosensory retina shows foveo-macular cystic schisis cavities in the outer plexiform (OPL) and inner nuclear layers (INL). XLRS manifests between infancy and school-age with variable phenotypic presentation and without reliable genotype-phenotype correlations. INL disorganization disrupts synaptic signal transmission from photoreceptors to ON-bipolar cells, and this reduces the electroretinogram (ERG) bipolar b-wave disproportionately to photoreceptor a-wave changes. RS1 gene expression is localized mainly to photoreceptors and INL bipolar neurons, and RS1 protein is thought to play a critical cell adhesion role during normal retinal development and later for maintenance of retinal structure. Several independent XLRS mouse models with mutant RS1 were created that recapitulate features of human XLRS disease, with OPL-INL schisis cavities, early onset and variable phenotype across mutant models, and reduced ERG b-wave to a-wave amplitude ratio. The faithful phenotype of the XLRS mouse has assisted in delineating the disease pathophysiology. Delivery to XLRS mouse retina of an AAV8-RS1 construct under control of the RS1 promoter restores the retinal structure and synaptic function (with increase of b-wave amplitude). It also ameliorates the schisis-induced inflammatory microglia phenotype toward a state of immune quiescence. The results imply that XLRS gene therapy could yield therapeutic benefit to preserve morphological and functional retina particularly when intervention is conducted at earlier ages before retinal degeneration becomes irreversible. A phase I/IIa single-center, open-label, three-dose-escalation clinical trial reported a suitable safety and tolerability profile of intravitreally administered AAV8-RS1 gene replacement therapy for XLRS participants. Dose-related ocular inflammation occurred after dosing, but this resolved with topical and oral corticosteroids. Systemic antibodies against AAV8 increased in dose-dependent fashion, but no antibodies were observed against the RS1 protein. Retinal cavities closed transiently in one participant. Technological innovations in methods of gene delivery and strategies to further reduce immune responses are expected to enhance the therapeutic efficacy of the vector and ultimate success of a gene therapy approach.

Robust and Comprehensive Targeted Metabolomics Method for Quantification of 50 Different Primary, Secondary, and Sulfated Bile Acids in Multiple Biological Species (Human, Monkey, Rabbit, Dog, and Rat) and Matrices (Plasma and Urine) Using Liquid Chromatography High Resolution Mass Spectrometry (LC-HRMS) Analysis

Bile acids (BAs) are biomolecules synthesized in the liver from cholesterol and are constituents of bile. The in-vivo BA pool includes more than 50 known diverse BAs which are unconjugated, amino acid conjugated, sulfated, and glucuronidated metabolites. Hemostasis of bile acids is known to be highly regulated and an interplay between liver metabolism, gut microbiome function, intestinal absorption, and enterohepatic recirculation. Interruption of BA homeostasis has been attributed to several metabolic diseases and drug induced liver injury (DILI), and their use as potential biomarkers is increasingly becoming important. Speciated quantitative and comprehensive profiling of BAs in various biomatrices from humans and preclinical animal species are important to understand their significance and biological function. Consequently, a versatile one single bioanalytical method for BAs is required to accommodate quantitation in a broad range of biomatrices from human and preclinical animal species. Here we report a versatile, comprehensive, and high throughput liquid chromatography-high resolution mass spectrometry (LC-HRMS) targeted metabolomics method for quantitative analysis of 50 different BAs in multiple matrices including human serum, plasma, and urine and plasma and urine of preclinical animal species (rat, rabbit, dog, and monkey). The method has been sufficiently qualified for accuracy, precision, robustness, and ruggedness and addresses the issue of nonspecific binding of bile acids to plastic for urine samples. Application of this method includes comparison for BA analysis between matched plasma and serum samples, human and animal species differences in BA pools, data analysis, and visualization of complex BA data using BA indices or ratios to understand BA biology, metabolism, and transport.

Assessing Toxicity in Drug Trials in Liver Disease

Since the early trials in viral hepatitis, more and more new drugs are being tested for use in various liver diseases. Since drug hepatotoxicity is a major cause of drugs under investigation not making it to market, the assessment of drug-induced liver injury in clinical trials of new drugs is crucial. This review will focus on the systems that are used to assess drug-induced liver injury in clinical trials and will discuss how some of these criteria are inappropriate or inaccurate in this function together with suggestions for improvement.

Application of human liver organoids as a patient-derived primary model for HBV infection and related hepatocellular carcinoma

The molecular events that drive hepatitis B virus (HBV)-mediated transformation and tumorigenesis have remained largely unclear, due to the absence of a relevant primary model system. Here we propose the use of human liver organoids as a platform for modeling HBV infection and related tumorigenesis. We first describe a primary ex vivo HBV-infection model derived from healthy donor liver organoids after challenge with recombinant virus or HBV-infected patient serum. HBV-infected organoids produced covalently closed circular DNA (cccDNA) and HBV early antigen (HBeAg), expressed intracellular HBV RNA and proteins, and produced infectious HBV. This ex vivo HBV-infected primary differentiated hepatocyte organoid platform was amenable to drug screening for both anti-HBV activity and drug-induced toxicity. We also studied HBV replication in transgenically modified organoids; liver organoids exogenously overexpressing the HBV receptor sodium taurocholate co-transporting polypeptide (NTCP) after lentiviral transduction were not more susceptible to HBV, suggesting the necessity for additional host factors for efficient infection. We also generated transgenic organoids harboring integrated HBV, representing a long-term culture system also suitable for viral production and the study of HBV transcription. Finally, we generated HBV-infected patient-derived liver organoids from non-tumor cirrhotic tissue of explants from liver transplant patients. Interestingly, transcriptomic analysis of patient-derived liver organoids indicated the presence of an aberrant early cancer gene signature, which clustered with the hepatocellular carcinoma (HCC) cohort on The Cancer Genome Atlas Liver Hepatocellular Carcinoma dataset and away from healthy liver tissue, and may provide invaluable novel biomarkers for the development of HCC and surveillance in HBV-infected patients.

Idiosyncratic Drug-Induced Liver Injury: Mechanistic and Clinical Challenges

Idiosyncratic drug-induced liver injury (IDILI) remains a significant problem for patients and drug development. The idiosyncratic nature of IDILI makes mechanistic studies difficult, and little is known of its pathogenesis for certain. Circumstantial evidence suggests that most, but not all, IDILI is caused by reactive metabolites of drugs that are bioactivated by cytochromes P450 and other enzymes in the liver. Additionally, there is overwhelming evidence that most IDILI is mediated by the adaptive immune system; one example being the association of IDILI caused by specific drugs with specific human leukocyte antigen (HLA) haplotypes, and this may in part explain the idiosyncratic nature of these reactions. The T cell receptor repertoire likely also contributes to the idiosyncratic nature. Although most of the liver injury is likely mediated by the adaptive immune system, specifically cytotoxic CD8+ T cells, adaptive immune activation first requires an innate immune response to activate antigen presenting cells and produce cytokines required for T cell proliferation. This innate response is likely caused by either a reactive metabolite or some form of cell stress that is clinically silent but not idiosyncratic. If this is true it would make it possible to study the early steps in the immune response that in some patients can lead to IDILI. Other hypotheses have been proposed, such as mitochondrial injury, inhibition of the bile salt export pump, unfolded protein response, and oxidative stress although, in most cases, it is likely that they are also involved in the initiation of an immune response rather than representing a completely separate mechanism. Using the clinical manifestations of liver injury from a number of examples of IDILI-associated drugs, this review aims to summarize and illustrate these mechanistic hypotheses.

3D human liver organoids: An in vitro platform to investigate HBV infection, replication and liver tumorigenesis

Hepatitis B Virus (HBV) infection is a leading cause of chronic liver cirrhosis and hepatocellular carcinoma (HCC) with an estimated 400 million people infected worldwide. The precise molecular mechanisms underlying HBV replication and tumorigenesis have remained largely uncharacterized due to the lack of a primary cell model to study HBV, a virus that exhibits stringent host species and cell-type specificity. Organoid technology has recently emerged as a powerful tool to investigate human diseases in a primary 3D cell-culture system that maintains the organisation and functionality of the tissue of origin. In this review, we describe the utilisation of human liver organoid platforms to study HBV. We first present the different categories of liver organoids and their demonstrated ability to support the complete HBV replication cycle. We then discuss the potential applications of liver organoids in investigating HBV infection and replication, related tumorigenesis and novel HBV-directed therapies. Liver organoids can be genetically modified, patient-derived, expanded and biobanked, thereby serving as a clinically-relevant, human, primary cell-derived platform to investigate HBV. Finally, we provide insights into the future applications of this powerful technology in the context of HBV-infection and HCC.

Advances in Nucleoside and Nucleotide Analogues in Tackling Human Immunodeficiency Virus and Hepatitis Virus Infections

Nucleoside and nucleotide analogues are structurally similar antimetabolites and are promising small-molecule chemotherapeutic agents against various infectious DNA and RNA viruses. To date, these analogues have not been documented in-depth as anti-human immunodeficiency virus (HIV) and anti-hepatitis virus agents, these are at various stages of testing ranging from pre-clinical, to those withdrawn from trials, or those that are approved as drugs. Hence, in this review, the importance of these analogues in tackling HIV and hepatitis virus infections is discussed with a focus on the viral genome and the mechanism of action of these analogues, both in a mutually exclusive manner and their role in HIV/hepatitis coinfection. This review encompasses nucleoside and nucleotide analogues from 1987 onwards, starting with the first nucleoside analogue, zidovudine, and going on to those in current clinical trials and even the drugs that have been withdrawn. This review also sheds light on the prospects of these nucleoside analogues in clinical trials as a treatment option for the COVID-19 pandemic.

Consensus Guidelines: Best Practices for Detection, Assessment and Management of Suspected Acute Drug-Induced Liver Injury During Clinical Trials in Adults with Chronic Viral Hepatitis and Adults with Cirrhosis Secondary to Hepatitis B, C and Nonalcoholic Steatohepatitis

With the widespread development of new drugs to treat chronic liver diseases (CLDs), including viral hepatitis and nonalcoholic steatohepatitis (NASH), more patients are entering trials with abnormal baseline liver tests and with advanced liver injury, including cirrhosis. The current regulatory guidelines addressing the monitoring, diagnosis, and management of suspected drug-induced liver injury (DILI) during clinical trials primarily address individuals entering with normal baseline liver tests. Using the same laboratory criteria cited as signals of potential DILI in studies involving patients with no underlying liver disease and normal baseline liver tests may result in premature and unnecessary cessation of a study drug in a clinical trial population whose abnormal and fluctuating liver tests are actually due to their underlying CLD. This position paper focuses on defining best practices for the detection, monitoring, diagnosis, and management of suspected acute DILI during clinical trials in patients with CLD, including hepatitis C virus (HCV) and hepatitis B virus (HBV), both with and without cirrhosis and NASH with cirrhosis. This is one of several position papers developed by the IQ DILI Initiative, comprising members from 16 pharmaceutical companies in collaboration with DILI experts from academia and regulatory agencies. It is based on an extensive literature review and discussions between industry members and experts from outside industry to achieve consensus regarding the recommendations. Key conclusions and recommendations include (1) the importance of establishing laboratory criteria that signal potential DILI events and that fit the disease indication being studied in the clinical trial based on knowledge of the natural history of test fluctuations in that disease; (2) establishing a pretreatment value that is based on more than one screening determination, and revising that baseline during the trial if a new nadir is achieved during treatment; (3) basing rules for increased monitoring and for stopping drug for potential DILI on multiples of baseline liver test values and/or a threshold value rather than multiples of the upper limit of normal (ULN) for that test; (4) making use of more sensitive tests of liver function, including direct bilirubin (DB) or combined parameters such as aspartate transaminase:alanine transaminase (AST:ALT) ratio or model for end-stage liver disease (MELD) to signal potential DILI, especially in studies of patients with cirrhosis; and (5) being aware of potential confounders related to complications of the disease being studied that may masquerade as DILI events.

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.

Antisense technology: A review

Antisense technology is beginning to deliver on the broad promise of the technology. Ten RNA-targeted drugs including eight single-strand antisense drugs (ASOs) and two double-strand ASOs (siRNAs) have now been approved for commercial use, and the ASOs in phase 2/3 trials are innovative, delivered by multiple routes of administration and focused on both rare and common diseases. In fact, two ASOs are used in cardiovascular outcome studies and several others in very large trials. Interest in the technology continues to grow, and the field has been subject to a significant number of reviews. In this review, we focus on the molecular events that result in the effects observed and use recent clinical results involving several different ASOs to exemplify specific molecular mechanisms and specific issues. We conclude with the prospective on the technology.

Recent Progress in Prediction Systems for Drug-induced Liver Injury Using in vitro Cell Culture

BACKGROUND

In order to avoid drug-induced liver injury (DILI), in vitro assays, which enable the assessment of both metabolic activation and immune reaction processes that ultimately result in DILI, are needed.

OBJECTIVE

In this study, the recent progress in the application of in vitro assays using cell culture systems is reviewed for potential DILI-causing drugs/xenobiotics and a mechanistic study on DILI, as well as for the limitations of in vitro cell culture systems for DILI research.

METHODS

Information related to DILI was collected through a literature search of the PubMed database.

RESULTS

The initial biological event for the onset of DILI is the formation of cellular protein adducts after drugs have been metabolically activated by drug metabolizing enzymes. The damaged peptides derived from protein adducts lead to the activation of CD4+ helper T lymphocytes and recognition by CD8+ cytotoxic T lymphocytes, which destroy hepatocytes through immunological reactions. Because DILI is a major cause of drug attrition and drug withdrawal, numerous in vitro systems consisting of hepatocytes and immune/inflammatory cells, or spheroids of human primary hepatocytes containing non-parenchymal cells have been developed. These cellular-based systems have identified DILIinducing drugs with approximately 50% sensitivity and 90% specificity.

CONCLUSION

Different co-culture systems consisting of human hepatocyte-derived cells and other immune/inflammatory cells have enabled the identification of DILI-causing drugs and of the actual mechanisms of action.

Probing the Mechanism of Hepatotoxicity of Hexabromocyclododecanes through Toxicological Network Analysis

The prediction and mechanism analysis of hepatotoxicity of contaminants, because of their various phenotypes and complex mechanisms, is still a key problem in environmental research. We applied a toxicological network analysis method to predict the hepatotoxicity of three hexabromocyclododecane (HBCD) diastereoisomers (α-HBCD, β-HBCD, and γ-HBCD) and explore their potential mechanisms. First, we collected the hepatotoxicity related genes and found that those genes were significantly localized in the human interactome. Therefore, these genes form a disease module of hepatotoxicity. We also collected targets of α-, β-, and γ-HBCD and found that their targets overlap with the hepatotoxicity disease module. Then, we trained a model to predict hepatotoxicity of three HBCD diastereoisomers based on the relationship between the hepatotoxicity disease module and targets of compounds. We found that 593 genes were significantly located in the hepatotoxicity disease module (Z = 11.9, p < 0.001) involved in oxidative stress, cellular immunity, and proliferation, and the accuracy of hepatotoxicity prediction of HBCD was 0.7095 ± 0.0193 and the recall score was 0.8355 ± 0.0352. HBCD mainly affects the core disease module genes to mediate the adenosine monophosphate-activated kinase, p38MAPK, PI3K/Akt, and TNFα pathways to regulate the immune reaction and inflammation. HBCD also induces the secretion of IL6 and STAT3 to lead hepatotoxicity by regulating NR3C1. This approach is transferable to other toxicity research studies of environmental pollutants.

Comparative Transcriptomics Analyses in Livers of Mice, Humans, and Humanized Mice Define Human-Specific Gene Networks

Mouse is the most widely used animal model in biomedical research, but it remains unknown what causes the large number of differentially regulated genes between human and mouse livers identified in recent years. In this report, we aim to determine whether these divergent gene regulations are primarily caused by environmental factors or some of them are the result of cell-autonomous differences in gene regulation in human and mouse liver cells. The latter scenario would suggest that many human genes are subject to human-specific regulation and can only be adequately studied in a human or humanized system. To understand the similarity and divergence of gene regulation between human and mouse livers, we performed stepwise comparative analyses in human, mouse, and humanized livers with increased stringency to gradually remove the impact of factors external to liver cells, and used bioinformatics approaches to retrieve gene networks to ascertain the regulated biological processes. We first compared liver gene regulation by fatty liver disease in human and mouse under the condition where the impact of genetic and gender biases was minimized, and identified over 50% of all commonly regulated genes, that exhibit opposite regulation by fatty liver disease in human and mouse. We subsequently performed more stringent comparisons when a single specific transcriptional or post-transcriptional event was modulated in vitro or vivo or in liver-specific humanized mice in which human and mouse hepatocytes colocalize and share a common circulation. Intriguingly and strikingly, the pattern of a high percentage of oppositely regulated genes persists under well-matched conditions, even in the liver of the humanized mouse model, which represents the most closely matched in vivo condition for human and mouse liver cells that is experimentally achievable. Gene network analyses further corroborated the results of oppositely regulated genes and revealed substantial differences in regulated biological processes in human and mouse cells. We also identified a list of regulated lncRNAs that exhibit very limited conservation and could contribute to these differential gene regulations. Our data support that cell-autonomous differences in gene regulation might contribute substantially to the divergent gene regulation between human and mouse livers and there are a significant number of biological processes that are subject to human-specific regulation and need to be carefully considered in the process of mouse to human translation.

Cancer cell metabolism: Rewiring the mitochondrial hub

To adapt to tumoral environment conditions or even to escape chemotherapy, cells rapidly reprogram their metabolism to handle adversities and survive. Given the rapid rise of studies uncovering novel insights and therapeutic opportunities based on the role of mitochondria in tumor metabolic programing and therapeutics, this review summarizes most significant developments in the field. Taking in mind the key role of mitochondria on carcinogenesis and tumor progression due to their involvement on tumor plasticity, metabolic remodeling, and signaling re-wiring, those organelles are also potential therapeutic targets. Among other topics, we address the recent data intersecting mitochondria as of prognostic value and staging in cancer, by mitochondrial DNA (mtDNA) determination, and current inhibitors developments targeting mtDNA, OXPHOS machinery and metabolic pathways. We contribute for a holistic view of the role of mitochondria metabolism and directed therapeutics to understand tumor metabolism, to circumvent therapy resistance, and to control tumor development.

Radiation induced cardiovascular disease: An odyssey of bedside-bench-bedside approach

The journey to Mars will be an ambitious, yet arduous task as it will entail culmination of all the information we have gathered over many decades. While the mission is of utmost importance, preservation of astronaut's well-being is paramount also. To that end, mitigation of radiation risk especially afflicting cardiovascular disease (CVD) is of great interest and challenge. Current data from astronauts on low earth orbit and Apollo missions provides insight on the risk of CVD from radiation exposure. However, data is limited given the small cohort size of astronauts who embarked on just nine prolonged missions. Therefore, a cerebral approach to understanding and mitigating risks are essential. This paper discusses the need for a predictive preclinical model to help understand and mitigate the effects of radiation on astronauts. We will discuss strengths and limitations of preclinical models and the methods of validating and constructing a model to predict human clinical outcomes. Our bedside-bench-bedside approach focuses on adapting the preclinical model through common investigative tools used between humans and animals. The result will be an optimization of preclinical model to a point of being a surrogate clinical model capable of predicting CVD outcomes in astronauts exposed to radiation.

Orally efficacious broad-spectrum allosteric inhibitor of paramyxovirus polymerase

Paramyxoviruses such as human parainfluenza virus type-3 (HPIV3) and measles virus (MeV) are a substantial health threat. In a high-throughput screen for inhibitors of HPIV3 (a major cause of acute respiratory infection), we identified GHP-88309-a non-nucleoside inhibitor of viral polymerase activity that possesses unusual broad-spectrum activity against diverse paramyxoviruses including respiroviruses (that is, HPIV1 and HPIV3) and morbilliviruses (that is, MeV). Resistance profiles of distinct target viruses overlapped spatially, revealing a conserved binding site in the central cavity of the viral polymerase (L) protein that was validated by photoaffinity labelling-based target mapping. Mechanistic characterization through viral RNA profiling and in vitro MeV polymerase assays identified a block in the initiation phase of the viral polymerase. GHP-88309 showed nanomolar potency against HPIV3 isolates in well-differentiated human airway organoid cultures, was well tolerated (selectivity index > 7,111) and orally bioavailable, and provided complete protection against lethal infection in a Sendai virus mouse surrogate model of human HPIV3 disease when administered therapeutically 48 h after infection. Recoverees had acquired robust immunoprotection against reinfection, and viral resistance coincided with severe attenuation. This study provides proof of the feasibility of a well-behaved broad-spectrum allosteric antiviral and describes a chemotype with high therapeutic potential that addresses major obstacles of anti-paramyxovirus drug development.

The utility of a differentiated preclinical liver model, HepaRG cells, in investigating delayed toxicity via inhibition of mitochondrial-replication induced by fialuridine

During its clinical development fialuridine caused liver toxicity and the death of five patients. This case remains relevant due to the continued development of mechanistically-related compounds against a back-drop of simple in vitro models which remain limited for the preclinical detection of such delayed toxicity. Here, proteomic investigation of a differentiated, HepaRG, and proliferating, HepG2 cell model was utilised to confirm the presence of the hENT1 transporter, thymidine kinase-1 and -2 (TK1, TK2) and thymidylate kinase, all essential in order to reproduce the cellular activation and disposition of fialuridine in the clinic. Acute metabolic modification assays could only identify mitochondrial toxicity in HepaRG cells following extended dosing, 2 weeks. Toxic effects were observed around 10 μM, which is within a range of 10-15 X approximate Cmax. HepaRG cell death was accompanied by a significant decrease in mitochondrial DNA content, indicative of inhibition of mitochondrial replication, and a subsequent reduction in mitochondrial respiration and the activity of mitochondrial respiratory complexes, not replicated in HepG2 cells. The structural epimer of fialuridine, included as a pharmacological negative control, was shown to have no cytotoxic effects in HepaRG cells up to 4 weeks. Overall, these comparative studies demonstrate the HepaRG model has translational relevance for fialuridine toxicity and therefore may have potential in investigating the inhibition of mitochondrial replication over prolonged exposure for other toxicants.

Therapeutic potential of uracil and its derivatives in countering pathogenic and physiological disorders

Uracil is one of the most notable pharmacophores in medicinal chemistry as the pyrimidine nucleobase forms an integral part of many commercial drugs. Though the name uracil is usually associated with cancer drugs, there are many uracil-based compounds which can treat different diseases when they are employed. So far, there has been no in-depth review concerning uracil drugs in the market, or in the different stages of clinical trials, including those approved or discontinued. The current work focuses on the importance of uracil and its derivatives in treating different diseases. The use of uracil compounds in treating viral infections, cancer, diabetic, thyroid and autosomal recessive disorders are discussed in the review. The mechanism of action of each uracil drug with emphasis on their structure and properties are discussed in detail. The targeted action of these drugs on sites or on the different stages of a disorder/pathogenic life cycle are also discussed. This review encompasses uracil drugs approved as well as those in development from the 1950's onwards. The utility of uracil in drug discovery and its association with a wide range of diseases is brought forth within this review to demonstrate its potential to a wider audience.

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.