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Introduction: Cardiotoxicity is one of the leading causes of compound attrition during drug development. Most in vitro screening platforms aim at detecting acute cardio-electrophysiological changes and drug-induced chronic functional alterations are often not studied in the early stage of drug development. Therefore, we developed an assay using human-induced pluripotent stem cellderived cardiomyocytes (hiPSC-CMs) that evaluates both drug-induced acute and delayed electrophysiological and cytotoxic effects of reference compounds with clinically known cardiac outcomes. Methods: hiPSC-CMs were seeded in 48-well multielectrode array (MEA) plates and were treated with four doses of reference compounds (covering and exceeding clinical free plasma peak concentrations -fCmax values) and MEA recordings were conducted for 4 days. Functional-electrophysiological (fieldpotentials) and viability (impedance) parameters were recorded with a MEA machine. Results: To assess this platform, we tested tyrosine-kinase inhibitors with highcardiac risk profile (sunitinib, vandetanib and nilotinib) and low-cardiac risk (erlotinib), as well as known classic cardiac toxic drugs (doxorubicin and BMS-986094), ion-channel trafficking inhibitors (pentamidine, probucol and arsenic trioxide) and compounds without known clinical cardiotoxicity (amoxicillin, cetirizine, captopril and aspirin). By evaluating the effects of these compounds on MEA parameters, the assay was mostly able to recapitulate different druginduced cardiotoxicities, represented by a prolongation of the field potential, changes in beating rate and presence of arrhythmic events in acute (<2 h) or delayed phase =24 h, and/or reduction of impedance during the delayed phase (=24 h). Furthermore, a few reference compounds were tested in hiPSC-CMs using fluorescence- and luminescence-based plate reader assays, confirming the presence or absence of cytotoxic effects, linked to changes of the impedance parameters measured in the MEA assay. Of note, some cardiotoxic effects could not be identified at acute time points (<2 h) but were clearly detected after 24 h, reinforcing the importance of chronic drug evaluation. Discussion: In conclusion, the evaluation of chronic drug-induced cardiotoxicity using a hiPSC-CMs in vitro assay can contribute to the early de-risking of compounds and help optimize the drug development process. [ABSTRACT FROM AUTHOR]

Myeloid cell leukemia-1 (MCL-1) is a member of the antiapoptotic BCL-2 proteins family and a key regulator of mitochondrial homeostasis. Overexpression of MCL-1 is found in many cancer cells and contributes to tumor progression, which makes it an attractive therapeutic target. Pursuing our previous study of macrocyclic indoles for the inhibition of MCL-1, we report herein the impact of both pyrazole and indole isomerism on the potency and overall properties of this family of compounds. We demonstrated that the incorporation of a fluorine atom on the naphthalene moiety was a necessary step to improve cellular potency and that, combined with the introduction of various side chains on the pyrazole, it enhanced solubility significantly. This exploration culminated in the discovery of compounds ( R a )- 10 and ( R a )- 15 , possessing remarkable cellular potency and properties., Competing Interests: The authors declare no competing financial interest., (© 2023 American Chemical Society.)

Human induced pluripotent stem cell derived cardiomyocytes (hiPSC-CMs) are currently used following the Comprehensive in vitro Proarrhythmic Assay (CiPA) initiative and subsequent recommendations in the International Council for Harmonization (ICH) guidelines S7B and E14 Q&A, to detect drug-induced cardiotoxicity. Monocultures of hiPSC-CMs are immature compared to adult ventricular cardiomyocytes and might lack the native heterogeneous nature. We investigated whether hiPSC-CMs, treated to enhance structural maturity, are superior in detecting drug-induced changes in electrophysiology and contraction. This was achieved by comparing hiPSC-CMs cultured in 2D monolayers on the current standard (fibronectin matrix, FM), to monolayers on a coating known to promote structural maturity (CELLvo™ Matrix Plus, MM). Functional assessment of electrophysiology and contractility was made using a high-throughput screening approach involving the use of both voltage-sensitive fluorescent dyes for electrophysiology and video technology for contractility. Using 11 reference drugs, the response of the monolayer of hiPSC-CMs was comparable in the two experimental settings (FM and MM). The data showed no functionally relevant differences in electrophysiology between hiPSC-CMs in standard FM and MM, while contractility read-outs indicated an altered amplitude of contraction but not changes in time course. RNA profiling for cardiac proteins shows similarity of the RNA expression across the two forms of 2D culture, suggesting that cell-to-matrix adhesion differences may explain account for differences in contraction amplitude. The results support the view that hiPSC-CMs in both 2D monolayer FM and MM that promote structural maturity are equally effective in detecting drug-induced electrophysiological effects in functional safety studies.

Drug-induced seizure liability is a significant safety issue and the basis for attrition in drug development. Occurrence in late development results in increased costs, human risk, and delayed market availability of novel therapeutics. Therefore, there is an urgent need for biologically relevant, in vitro high-throughput screening assays (HTS) to predict potential risks for drug-induced seizure early in drug discovery. We investigated drug-induced changes in neural Ca 2+ oscillations, using fluorescent dyes as a potential indicator of seizure risk, in hiPSC-derived neurons co-cultured with human primary astrocytes in both 2D and 3D forms. The dynamics of synchronized neuronal calcium oscillations were measured with an FDSS kinetics reader. Drug responses in synchronized Ca 2+ oscillations were recorded in both 2D and 3D hiPSC-derived neuron/primary astrocyte co-cultures using positive controls (4-aminopyridine and kainic acid) and negative control (acetaminophen). Subsequently, blinded tests were carried out for 25 drugs with known clinical seizure incidence. Positive predictive value (accuracy) based on significant changes in the peak number of Ca 2+ oscillations among 25 reference drugs was 91% in 2D vs. 45% in 3D hiPSC-neuron/primary astrocyte co-cultures. These data suggest that drugs that alter neuronal activity and may have potential risk for seizures can be identified with high accuracy using an HTS approach using the measurements of Ca 2+ oscillations in hiPSC-derived neurons co-cultured with primary astrocytes in 2D.

Aims: Human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) have proven valuable for studies in drug discovery and safety, although limitations regarding their structural and electrophysiological characteristics persist. In this study, we investigated the electrophysiological properties of Pluricyte® CMs, a commercially available hiPSC-CMs line with a ventricular phenotype, and assessed arrhythmia incidence by IKr block at the single-cell and 2D monolayer level., Methods and Results: Action potentials were measured at different pacing frequencies, using dynamic clamp. Through voltage-clamp experiments, we determined the properties of INa, IKr, and ICaL. Intracellular Ca2+ measurements included Ca2+-transients at baseline and during caffeine perfusion. Effects of IKr block were assessed in single hiPSC-CMs and 2D monolayers (multi-electrode arrays). Action-potential duration (APD) and its rate dependence in Pluricyte® CMs were comparable to those reported for native human CMs. INa, IKr, and ICaL revealed amplitudes, kinetics, and voltage dependence of activation/inactivation similar to other hiPSC-CM lines and, to some extent, to native CMs. Near-physiological Ca2+-induced Ca2+ release, response to caffeine and excitation-contraction coupling gain characterized the cellular Ca2+-handling. Dofetilide prolonged the APD and field-potential duration, and induced early afterdepolarizations. Beat-to-beat variability of repolarization duration increased significantly before the first arrhythmic events in single Pluricyte® CMs and 2D monolayers, and predicted pending arrhythmias better than action-potential prolongation., Conclusion: Taking their ion-current characteristics and Ca2+ handling into account, Pluricyte® CMs are suitable for in vitro studies on action potentials and field potentials. Beat-to-beat variability of repolarization duration proved useful to evaluate the dynamics of repolarization instability and demonstrated its significance as proarrhythmic marker in hiPSC-CMs during IKr block., (© The Author(s) 2020. Published by Oxford University Press on behalf of the European Society of Cardiology.)

Neurotoxicants are substances that can lead to adverse structural or functional effects on the nervous system. These can be chemical, biological, or physical agents that can cross the blood brain barrier to damage neurons or interferewith complex interactions between the nervous system and other organs. With concerns regarding social policy, public health, andmedicine, there is a need to ensure rigorous testing for neurotoxicity. While the most common neurotoxicity tests involve using animal models, a shift towards stem cell-based platforms can potentially provide a more biologically accurate alternative in both clinical and pharmaceutical research. With this in mind, the objective of this article is to review both current technologies and recent advancements in evaluating neurotoxicants using stem cell-based approaches, with an emphasis on developmental neurotoxicants (DNTs) as these have the most potential to lead to irreversible critical damage on brain function. In the next section, attempts to develop novel predictive model approaches for the study of both neural cell fate and developmental neurotoxicity are discussed. Finally, this article concludes with a discussion of the future use of in silico methods within developmental neurotoxicity testing, and the role of regulatory bodies in promoting advancementswithin the space. [ABSTRACT FROM AUTHOR]

This document discusses the importance of calcium regulation in cardiac cells and its role in cardiac disease modeling and drug discovery. Calcium is essential for cell function and plays a critical role in excitation-contraction coupling in the heart. The document highlights several studies that explore the regulation of calcium in different cardiac diseases and the potential for targeting specific calcium regulators for therapeutic purposes. The studies also discuss the use of calcium imaging in assessing cardiomyocyte function and arrhythmia. Overall, the document emphasizes the significance of calcium regulation in understanding disease mechanisms and developing new treatment approaches. [Extracted from the article]

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Human induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) represent an in vitro model of cardiac function. Isolated iPSC-CMs, however, exhibit electrophysiological heterogeneity which hinders their utility in the study of certain cardiac currents. In the healthy adult heart, the current mediated by small conductance, calcium-activated potassium (SK) channels (ISK) is atrial-selective. Functional expression of ISK within atrial-like iPSC-CMs has not been explored thoroughly. The present study therefore aimed to investigate atrial-like iPSC-CMs as a model system for the study of ISK. iPSCs were differentiated using retinoic acid (RA) to produce iPSC-CMs which exhibited an atrial-like phenotype (RA-iPSC-CMs). Only 18% of isolated RA-iPSC-CMs responded to SK channel inhibition by UCL1684 and isolated iPSC-CMs exhibited substantial cell-to-cell electrophysiological heterogeneity. This variability was significantly reduced by patch clamp of RA-iPSC-CMs in situ as a monolayer (iPSC-ML). A novel method of electrical stimulation was developed to facilitate recording from iPSC-MLs via In situ Monolayer Patch clamp of Acutely Stimulated iPSC-CMs (IMPASC). Using IMPASC, > 95% of iPSC-MLs could be paced at a 1 Hz. In contrast to isolated RA-iPSC-CMs, 100% of RA-iPSC-MLs responded to UCL1684, with APD50 being prolonged by 16.0 ± 2.0 ms (p < 0.0001; n = 12). These data demonstrate that in conjunction with IMPASC, RA-iPSC-MLs represent an improved model for the study of ISK. IMPASC may be of wider value in the study of other ion channels that are inconsistently expressed in isolated iPSC-CMs and in pharmacological studies. [ABSTRACT FROM AUTHOR]

This editorial titled "Recent advances in cardiotoxicity testing, volume II" discusses the increasing number of cardiovascular complications associated with therapeutic interventions, particularly in cancer treatment. It emphasizes the importance of robust preclinical screening strategies to mitigate risks before human clinical trials. The editorial highlights the shift towards innovative in vitro models, such as human induced pluripotent stem cell-derived cardiomyocytes, organoids, and human heart slices, which offer a more physiologically relevant platform for cardiotoxicity assessment. The document also provides a summary of eight manuscripts included in the Research Topic, covering various breakthroughs and methodologies in cardiotoxicity testing. Additionally, the document includes a list of references for articles related to drug-induced cardiotoxicity, providing valuable information for researchers and healthcare professionals studying this topic. [Extracted from the article]

Purpose of Review: This review explores the cardiovascular toxicity associated with cancer therapies, emphasizing the significance of the growing field of cardio-oncology. It aims to elucidate the mechanisms of cardiotoxicity due to radiotherapy, chemotherapy, and targeted therapies, and to discuss the advancements in human induced pluripotent stem cell technology (hiPSC) for predictive disease modeling., Recent Findings: Recent studies have identified several chemotherapeutic agents, including anthracyclines and kinase inhibitors, that significantly increase cardiovascular risks. Advances in hiPSC technology have enabled the differentiation of these cells into cardiovascular lineages, facilitating more accurate modeling of drug-induced cardiotoxicity. Moreover, integrating hiPSCs into clinical trials holds promise for personalized cardiotoxicity assessments, potentially enhancing patient-specific therapeutic strategies. Cardio-oncology bridges oncology and cardiology to mitigate the cardiovascular side-effects of cancer treatments. Despite advancements in predictive models using hiPSCs, challenges persist in accurately replicating adult heart tissue and ensuring reproducibility. Ongoing research is essential for developing personalized therapies that balance effective cancer treatment with minimal cardiovascular harm., (© 2024. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

In the last 25 years, EP Europace has published more than 300 basic and translational science articles covering different arrhythmia types (ranging from atrial fibrillation to ventricular tachyarrhythmias), different diseases predisposing to arrhythmia formation (such as genetic arrhythmia disorders and heart failure), and different interventional and pharmacological anti-arrhythmic treatment strategies (ranging from pacing and defibrillation to different ablation approaches and novel drug-therapies). These studies have been conducted in cellular models, small and large animal models, and in the last couple of years increasingly in silico using computational approaches. In sum, these articles have contributed substantially to our pathophysiological understanding of arrhythmia mechanisms and treatment options; many of which have made their way into clinical applications. This review discusses a representative selection of EP Europace manuscripts covering the topics of pacing and ablation, atrial fibrillation, heart failure and pro-arrhythmic ventricular remodelling, ion channel (dys)function and pharmacology, inherited arrhythmia syndromes, and arrhythmogenic cardiomyopathies, highlighting some of the advances of the past 25 years. Given the increasingly recognized complexity and multidisciplinary nature of arrhythmogenesis and continued technological developments, basic and translational electrophysiological research is key advancing the field. EP Europace aims to further increase its contribution to the discovery of arrhythmia mechanisms and the implementation of mechanism-based precision therapy approaches in arrhythmia management. [ABSTRACT FROM AUTHOR]

Subtype-specific human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) are promising tools, e.g., to assess the potential of drugs to cause chronotropic effects (nodal hiPSC-CMs), atrial fibrillation (atrial hiPSC-CMs), or ventricular arrhythmias (ventricular hiPSC-CMs). We used single-cell patch-clamp reverse transcriptase-quantitative polymerase chain reaction to clarify the composition of the iCell cardiomyocyte population (Fujifilm Cellular Dynamics, Madison, WI, USA) and to compare it with atrial and ventricular Pluricytes (Ncardia, Charleroi, Belgium) and primary human atrial and ventricular cardiomyocytes. The comparison of beating and non-beating iCell cardiomyocytes did not support the presence of true nodal, atrial, and ventricular cells in this hiPSC-CM population. The comparison of atrial and ventricular Pluricytes with primary human cardiomyocytes showed trends, indicating the potential to derive more subtype-specific hiPSC-CM models using appropriate differentiation protocols. Nevertheless, the single-cell phenotypes of the majority of the hiPSC-CMs showed a combination of attributes which may be interpreted as a mixture of traits of adult cardiomyocyte subtypes: (i) nodal: spontaneous action potentials and high HCN4 expression and (ii) non-nodal: prominent INa-driven fast inward current and high expression of SCN5A. This may hamper the interpretation of the drug effects on parameters depending on a combination of ionic currents, such as beat rate. However, the proven expression of specific ion channels supports the evaluation of the drug effects on ionic currents in a more realistic cardiomyocyte environment than in recombinant non-cardiomyocyte systems. [ABSTRACT FROM AUTHOR]