Moving towards better predictors of drug-induced torsades de pointes

Human Cardiac Ventricular-Like Organoid Chambers and Tissue Strips From Pluripotent Stem Cells as a Two-Tiered Assay for Inotropic Responses

Traditional drug discovery is an inefficient process. Human pluripotent stem cell-derived cardiomyocytes can potentially fill the gap between animal and clinical studies, but conventional two-dimensional cultures inadequately recapitulate the human cardiac phenotype. Here, we systematically examined the pharmacological responses of engineered human ventricular-like cardiac tissue strips (hvCTS) and organoid chambers (hvCOC) to 25 cardioactive compounds covering various drug classes. While hvCTS effectively detected negative and null inotropic effects, the sensitivity to positive inotropes was modest. We further quantified the predictive capacity of hvCTS in a blinded screening, with accuracies for negative, positive, and null inotropic effects at 100%, 86%, and 80%, respectively. Interestingly, hvCOC, with a pro-maturation milieu that yields physiologically complex parameters, displayed enhanced positive inotropy. Based on these results, we propose a two-tiered screening system for avoiding false positives and negatives. Such an approach would facilitate drug discovery by leading to better overall success.

Finding the rhythm of sudden cardiac death: new opportunities using induced pluripotent stem cell-derived cardiomyocytes

Sudden cardiac death is a common cause of death in patients with structural heart disease, genetic mutations, or acquired disorders affecting cardiac ion channels. A wide range of platforms exist to model and study disorders associated with sudden cardiac death. Human clinical studies are cumbersome and are thwarted by the extent of investigation that can be performed on human subjects. Animal models are limited by their degree of homology to human cardiac electrophysiology, including ion channel expression. Most commonly used cellular models are cellular transfection models, which are able to mimic the expression of a single-ion channel offering incomplete insight into changes of the action potential profile. Induced pluripotent stem cell-derived cardiomyocytes resemble, but are not identical, adult human cardiomyocytes and provide a new platform for studying arrhythmic disorders leading to sudden cardiac death. A variety of platforms exist to phenotype cellular models, including conventional and automated patch clamp, multielectrode array, and computational modeling. Induced pluripotent stem cell-derived cardiomyocytes have been used to study long QT syndrome, catecholaminergic polymorphic ventricular tachycardia, hypertrophic cardiomyopathy, and other hereditary cardiac disorders. Although induced pluripotent stem cell-derived cardiomyocytes are distinct from adult cardiomyocytes, they provide a robust platform to advance the science and clinical care of sudden cardiac death.

ILSI Health and Environmental Sciences Institute (HESI), global leader in advancing translational science to create science-based solutions for a sustainable, healthier world

The Health and Environmental Sciences Institute (HESI) is a non-profit scientific research organization based in Washington, D.C., U.S.A. HESI was established in 1989 as a global branch of the International Life Sciences Institute (ILSI) to provide an international forum to advance the understanding of scientific issues related to human health, toxicology, risk assessment and the environment. For the last 25 years, HESI has been the global leader to advance application of new science and technologies in the areas of human health, toxicology, risk assessment and environment. The core principle of “tripartite approach” and the multi-sector operational model have successfully supported HESI’s scientific programs to create science-based solutions for a sustainable and healthier world. HESI’s achievements include the dataset to guide the selection of appropriate supporting assays for carcinogenicity testing, a new testing framework for agricultural chemicals with enhanced efficacy, predictivity, and reduced animal usage, novel biomarkers of nephrotoxicity which provide data on the location of timing of drug effects in the kidney allowing for enhanced drug development, etc.

A public-private consortium advances cardiac safety evaluation: achievements of the HESI Cardiac Safety Technical Committee

INTRODUCTION

The evaluation of cardiovascular side-effects is a critical element in the development of all new drugs and chemicals. Cardiac safety issues are a major cause of attrition and withdrawal due to adverse drug reactions (ADRs) in pharmaceutical drug development.

METHODS

The evolution of the HESI Technical Committee on Cardiac Safety from 2000-2013 is presented as an example of an effective international consortium of academic, government, and industry scientists working to improve cardiac safety.

RESULTS AND DISCUSSION

The HESI Technical Committee Working Groups facilitated the development of a variety of platforms for resource sharing and communication among experts that led to innovative strategies for improved drug safety. The positive impacts arising from these Working Groups are described in this article.

hERG-related drug toxicity and models for predicting hERG liability and QT prolongation

BACKGROUND

hERG K(+) channels have been recognized as a primary antitarget in safety pharmacology. Their blockade, caused by several drugs with different therapeutic indications, may lead to QT prolongation and, eventually, to potentially fatal arrhythmia, namely torsade de pointes. Therefore, a number of preclinical models have been developed to predict hERG liability early in the drug development process.

OBJECTIVE

The aim of this review is to outline the present state of the art on drug-induced hERG blockade, providing insights on the predictive value of in vitro and in silico models for hERG liability.

METHODS

On the basis of latest reports, high-throughput preclinical models have been discussed outlining advantages and limitations.

CONCLUSION

Although no single model has an absolute value, an integrated risk assessment is recommended to predict the pro-arrhythmic risk of a given drug. This prediction requires expertise from different areas and should encompass emerging issues such as interference with hERG trafficking and QT shortening.

Measuring the risk of torsades de pointes: electrocardiographic evaluation of PNU-142093 in conscious cynomolgus non-human primates using restraint and non-restraint procedures

OBJECTIVE

Drug-induced torsades de pointes (TdP) arrhythmia is a serious public health concern that has significantly slowed the advancement of promising new therapeutic agents to the marketplace. Modeling for the potential to produce TdP has relied in part on the surrogate biomarker QT interval prolongation, measured in vivo in animals and in the clinic in man. This study was a comparison of the effects of PNU-142093, a selective 5HT1D-serotonin receptor agonist, on QT interval prolongation under restraint and non-restraint conditions in conscious cynomolgus non-human primates.

METHODS

Lead II electrocardiograms (ECG) were collected following an oral single-dose (non-restraint conditions using radio-telemetry) and single- and multiple-doses for 14 days (restraint conditions using electrodes applied to the surface) at doses of 0, 5, 15, and 25 mg/kg. ECG were collected from non-restrained animals predose and for up to 5 hrs, and again at 7 hrs, postdose on 4 different days in a Latin-square crossover design; N=4/sex/dose level. ECG were collected from restrained animals on days 1, 7, and 13, predose and at approximately 4 hrs postdose; N=2/sex/group.

RESULTS

Non-restrained animal heart rate ranged from 159+/-22.1 to 168+/-21.4 beats/minute when compared to restrained animal heart rate (ranging from 242+/-17.2 to 246+/-11.5 beats/minute), suggesting that non-restrained animals were under less stress. In non-restrained animals, PNU-142093 produced a non-dose related decrease in heart rate, associated with a dose-related increase in QT and QTc (QT interval corrected for changes in heart rate) intervals, which was accompanied by alterations in T-wave morphology (e.g., widening and notching of the T wave). In restrained non-human primates, PNU-142093 had no effect on heart rate or ECG morphology on any day of dosing and no statistically significant effect on QT or QTc intervals on days 1 or 7 of dosing. By day 13 there were statistically significant increases in QT and QTc intervals at 15 and 25 mg/kg. The increase in QTc interval in restrained animals on day 13 was 29+/-12 and 30+/-19 msec at 15 and 25 mg/kg/day, respectively, and that in non-restrained animals was 65+/-23 and 73+/-28 msec.

DISCUSSION

These data demonstrate an ability to detect problematic drugs in conscious cynomolgus non-human primates using both restraint and non-restraint procedures. They further show that the sensitivity of these assays to identify this signal of cardiac risk is significantly improved under the condition of non-restraint.

A HESI consortium approach to assess the human predictive value of non-clinical repolarization assays

Drug-induced ventricular arrhythmia and Torsades de Pointes remain a serious public health issues in bringing safe new pharmaceuticals to the market place. Under the auspices of the International Life Science Institute (ILSI)-Health and Environmental Sciences Institute (HESI), a consortium involving representatives from pharmaceutical companies, regulatory agencies and opinion leaders from the scientific and medical research communities has been initiated. The objectives are (1) to assess the concordance between signals in non-clinical repolarization assays and clinical QT interval prolongation; (2) to investigate the mechanisms for any discrepancy identified between non-clinical and clinical results and to determine viable and successful alternative approaches to identify these compounds; and (3) to assess the proarrhythmic potential of such compounds. At present, the consortium is conducting a retrospective analysis of non-clinical and clinical data from both FDA and contributing companies' databases and supplementing with a literature review. The overall objectives of these initial efforts are to establish a quantitative integrated risk assessment for each compound; to define criteria for concordance and apply them to the database in order to identify non-concordant compounds.

International Life Sciences Institute (Health and Environmental Sciences Institute, HESI) initiative on moving towards better predictors of drug-induced torsades de pointes

Knowledge of the cardiac safety of emerging new drugs is an important aspect of assuring the expeditious advancement of the best candidates targeted at unmet medical needs while also assuring the safety of clinical trial subjects or patients. Present methodologies for assessing drug-induced torsades de pointes (TdP) are woefully inadequate in terms of their specificity to select pharmaceutical agents, which are human arrhythmia toxicants. Thus, the critical challenge in the pharmaceutical industry today is to identify experimental models, composite strategies, or biomarkers of cardiac risk that can distinguish a drug, which prolongs cardiac ventricular repolarization, but is not proarrhythmic, from one that prolongs the QT interval and leads to TdP. To that end, the HESI Proarrhythmia Models Project Committee recognized that there was little practical understanding of the relationship between drug effects on cardiac ventricular repolarization and the rare clinical event of TdP. It was on that basis that a workshop was convened in Virginia, USA at which four topics were introduced by invited subject matter experts in the following fields: Molecular and Cellular Biology Underlying TdP, Dynamics of Periodicity, Models of TdP Proarrhythmia, and Key Considerations for Demonstrating Utility of Pre-Clinical Models. Contained in this special issue of the British Journal of Pharmacology are reports from each of the presenters that set out the background and key areas of discussion in each of these topic areas. Based on this information, the scientific community is encouraged to consider the ideas advanced in this workshop and to contribute to these important areas of investigations over the next several years.