The implementation of the ICH S7B and E14 guidelines has been successful in preventing the introduction of potentially torsadogenic drugs to the market, but it has also unduly constrained drug ...development by focusing on hERG block and QT prolongation as essential determinants of proarrhythmia risk. The Comprehensive in Vitro Proarrhythmia Assay (CiPA) initiative was established to develop a new paradigm for assessing proarrhythmic risk, building on the emergence of new technologies and an expanded understanding of torsadogenic mechanisms beyond hERG block. An international multi-disciplinary team of regulatory, industry and academic scientists are working together to develop and validate a set of predominantly nonclinical assays and methods that eliminate the need for the thorough-QT study and enable a more precise prediction of clinical proarrhythmia risk. The CiPA effort is led by a Steering Team that provides guidance, expertise and oversight to the various working groups and includes partners from US FDA, HESI, CSRC, SPS, EMA, Health Canada, Japan NIHS, and PMDA. The working groups address the three pillars of CiPA that evaluate drug effects on: 1) human ventricular ionic channel currents in heterologous expression systems, 2) in silico integration of cellular electrophysiologic effects based on ionic current effects, the ion channel effects, and 3) fully integrated biological systems (stem-cell-derived cardiac myocytes and the human ECG). This article provides an update on the progress of the initiative towards its target date of December 2017 for completing validation.
Keeping track of conceptual and methodological developments is a critical skill for research scientists, but this task is increasingly difficult due to the high rate of academic publication. As a ...crisis discipline, conservation science is particularly in need of tools that facilitate rapid yet insightful synthesis. We show how a common text‐mining method (latent Dirichlet allocation, or topic modeling) and statistical tests familiar to ecologists (cluster analysis, regression, and network analysis) can be used to investigate trends and identify potential research gaps in the scientific literature. We tested these methods on the literature on ecological surrogates and indicators. Analysis of topic popularity within this corpus showed a strong emphasis on monitoring and management of fragmented ecosystems, while analysis of research gaps suggested a greater role for genetic surrogates and indicators. Our results show that automated text analysis methods need to be used with care, but can provide information that is complementary to that given by systematic reviews and meta‐analyses, increasing scientists’ capacity for research synthesis.
Systemic inflammation co-activates coagulation, which unchecked culminates in a lethal syndrome of multi-organ microvascular thrombosis known as disseminated intravascular coagulation (DIC). We ...studied an endotoxin-induced inflammatory state in rats to identify biomarkers of hemostatic imbalance favoring hypercoagulability. Intraperitoneal injection of LPS at 15 mg/kg body weight resulted in peripheral leukopenia and widespread neutrophilic sequestration characteristic of an acute systemic inflammatory response. Early indicators of hemostatic pathway activation developed within 4 hours, including increased circulating concentrations of procoagulant extracellular vesicles (EVs), EVs expressing endothelial cell and platelet membrane markers, and high concentration of soluble intercellular adhesion molecule-1 (sICAM-1), plasminogen activator inhibitor-1 (PAI-1), and D-dimers. Inflammation persisted throughout the 48-hour observation period; however, increases were found in a subset of serum microRNA (miRNA) that coincided with gradual resolution of hemostatic protein abnormalities and reduction in EV counts. Dose-adjusted LPS treatment in rats provides a time-course model to develop biomarker profiles reflecting procoagulant imbalance and rebalance under inflammatory conditions.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
To assess the utility of human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) as an in vitro proarrhythmia model, we evaluated the concentration dependence and sources of ...variability of electrophysiologic responses to 28 drugs linked to low, intermediate, and high torsades de pointes (TdP) risk categories using two commercial cell lines and standardized protocols in a blinded multisite study using multielectrode array or voltage-sensing optical approaches. Logistical and ordinal linear regression models were constructed using drug responses as predictors and TdP risk categories as outcomes. Three of seven predictors (drug-induced arrhythmia-like events and prolongation of repolarization at either maximum tested or maximal clinical exposures) categorized drugs with reasonable accuracy (area under the curve values of receiver operator curves ∼0.8). hiPSC-CM line, test site, and platform had minimal influence on drug categorization. These results demonstrate the utility of hiPSC-CMs to detect drug-induced proarrhythmic effects as part of the evolving Comprehensive In Vitro Proarrhythmia Assay paradigm.
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•28 drugs classified by torsadesproarrhythmic risk studied in blinded experiments•Two commercial human cardiomyocyte lines used with 5 devices across 10 sites•Repolarization effects evaluated using microelectrode array and voltage-sensing dyes•Statistical model predicted proarrhythmic risk from electrophysiologic responses
Blinova et al. tested human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) for improving torsades de pointes arrhythmia risk prediction of drugs in the Comprehensive In Vitro Proarrhythmia Assay (CiPA) initiative. This validation study confirms their utility based on electrophysiologic responses to 28 blinded drugs, with minimal influence from cell lines, test sites, and electrophysiological platforms.
Background and Purpose
Translation of non‐clinical markers of delayed ventricular repolarization to clinical prolongation of the QT interval corrected for heart rate (QTc) (a biomarker for torsades ...de pointes proarrhythmia) remains an issue in drug discovery and regulatory evaluations. We retrospectively analysed 150 drug applications in a US Food and Drug Administration database to determine the utility of established non‐clinical in vitro IKr current human ether‐à‐go‐go‐related gene (hERG), action potential duration (APD) and in vivo (QTc) repolarization assays to detect and predict clinical QTc prolongation.
Experimental Approach
The predictive performance of three non‐clinical assays was compared with clinical thorough QT study outcomes based on free clinical plasma drug concentrations using sensitivity and specificity, receiver operating characteristic (ROC) curves, positive (PPVs) and negative predictive values (NPVs) and likelihood ratios (LRs).
Key Results
Non‐clinical assays demonstrated robust specificity (high true negative rate) but poor sensitivity (low true positive rate) for clinical QTc prolongation at low‐intermediate (1×–30×) clinical exposure multiples. The QTc assay provided the most robust PPVs and NPVs (ability to predict clinical QTc prolongation). ROC curves (overall test accuracy) and LRs (ability to influence post‐test probabilities) demonstrated overall marginal performance for hERG and QTc assays (best at 30× exposures), while the APD assay demonstrated minimal value.
Conclusions and Implications
The predictive value of hERG, APD and QTc assays varies, with drug concentrations strongly affecting translational performance. While useful in guiding preclinical candidates without clinical QT prolongation, hERG and QTc repolarization assays provide greater value compared with the APD assay.
Contractility of the myocardium engines the pumping function of the heart and is enabled by the collective contractile activity of its muscle cells: cardiomyocytes. The effects of drugs on the ...contractility of human cardiomyocytes
in vitro
can provide mechanistic insight that can support the prediction of clinical cardiac drug effects early in drug development. Cardiomyocytes differentiated from human-induced pluripotent stem cells have high potential for overcoming the current limitations of contractility assays because they attach easily to extracellular materials and last long in culture, while having human- and patient-specific properties. Under these conditions, contractility measurements can be non-destructive and minimally invasive, which allow assaying sub-chronic effects of drugs. For this purpose, the function of cardiomyocytes
in vitro
must reflect physiological settings, which is not observed in cultured cardiomyocytes derived from induced pluripotent stem cells because of the fetal-like properties of their contractile machinery. Primary cardiomyocytes or tissues of human origin fully represent physiological cellular properties, but are not easily available, do not last long in culture, and do not attach easily to force sensors or mechanical actuators. Microengineered cellular systems with a more mature contractile function have been developed in the last 5 years to overcome this limitation of stem cell–derived cardiomyocytes, while simultaneously measuring contractile endpoints with integrated force sensors/actuators and image-based techniques. Known effects of engineered microenvironments on the maturity of cardiomyocyte contractility have also been discovered in the development of these systems. Based on these discoveries, we review here design criteria of microengineered platforms of cardiomyocytes derived from pluripotent stem cells for measuring contractility with higher physiological relevance. These criteria involve the use of electromechanical, chemical and morphological cues, co-culture of different cell types, and three-dimensional cellular microenvironments. We further discuss the use and the current challenges for developing and improving these novel technologies for predicting clinical effects of drugs based on contractility measurements with cardiomyocytes differentiated from induced pluripotent stem cells. Future research should establish contexts of use in drug development for novel contractility assays with stem cell–derived cardiomyocytes.
Can We Panelize Seizure? Roberts, Ruth; Authier, Simon; Mellon, R Daniel ...
Toxicological sciences,
01/2021, Letnik:
179, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Abstract
Seizure liability remains a significant cause of attrition in drug discovery and development, leading to loss of competitiveness, delays, and increased costs. Current detection methods rely ...on observations made in in vivo studies intended to support clinical trials, such as tremors or other abnormal movements. These signs could be missed or misinterpreted; thus, definitive confirmation of drug-induced seizure requires a follow-up electroencephalogram study. There has been progress in in vivo detection of seizure using automated video systems that record and analyze animal movements. Nonetheless, it would be preferable to have earlier prediction of seizurogenic risk that could be used to eliminate liabilities early in discovery while there are options for medicinal chemists making potential new drugs. Attrition due to cardiac adverse events has benefited from routine early screening; could we reduce attrition due to seizure using a similar approach? Specifically, microelectrode arrays could be used to detect potential seizurogenic signals in stem-cell-derived neurons. In addition, there is clear evidence implicating neuronal voltage-gated and ligand-gated ion channels, GPCRs and transporters in seizure. Interactions with surrounding glial cells during states of stress or inflammation can also modulate ion channel function in neurons, adding to the challenge of seizure prediction. It is timely to evaluate the opportunity to develop an in vitro assessment of seizure linked to a panel of ion channel assays that predict seizure, with the aim of influencing structure-activity relationship at the design stage and eliminating compounds predicted to be associated with pro-seizurogenic state.
1. Pathogen emergence can drive major changes in host population demography, with implications for population dynamics and sensitivity to environmental fluctuations. The amphibian disease ...chytridiomycosis, caused by infection with the fungal pathogen Batrachochytrium dendrobatidis (Bd), is implicated in the severe decline of over 200 amphibian species. In species that have declined but not become extinct, Bd persists and can cause substantial ongoing mortality. High rates of mortality associated with Bd may drive major changes in host demography, but this process is poorly understood. 2. Here, we compared population age structure of Bd-infected populations, Bd-free populations and museum specimens collected prior to Bd emergence for the endangered Australian frog, Litoria verreauxii alpina (alpine tree frog). We then used population simulations to investigate how pathogen-associated demographic shifts affect the ability of populations to persist in stochastic environments. 3. We found that Bd-infected populations have a severely truncated age structure associated with very high rates of annual adult mortality. Near-complete annual adult turnover in Bd-infected populations means that individuals breed once, compared with Bd-free populations where adults may breed across multiple years. 4. Our simulations showed that truncated age structure erodes the capacity of populations to withstand periodic recruitment failure; a common challenge for species reproducing in uncertain environments. 5. We document previously undescribed demographic shifts associated with a globally emerging pathogen and demonstrate how these shifts alter host ecology. Truncation of age structure associated with Bd effectively reduces host niche width and can help explain the contraction of L. v. alpina to perennial waterbodies where the risk of drought-induced recruitment failure is low. Reduced capacity to tolerate other sources of mortality may explain variation in decline severity among other chytridiomycosis-challenged species and highlights the potential to mitigate disease impacts through minimizing other sources of mortality.
Revegetation and reproduction Belder, Donna J.; Pierson, Jennifer C.; Ikin, Karen ...
Oecologia,
04/2020, Letnik:
192, Številka:
4
Journal Article
Recenzirano
Odprti dostop
Restoration plantings are frequently occupied by native wildlife, but little is known about how planting attributes influence breeding by, and persistence of, fauna populations. We monitored breeding ...success of woodland birds in restoration plantings in a fragmented agricultural landscape in south-eastern Australia. We documented nest fate and daily nest survival (DSR) in plantings and remnant woodland sites. We analysed the influence on breeding success of patch attributes (size, shape, type) compared to other potentially influential predictors such as nest-site and microhabitat variables. We found that, in general, patch attributes did not play a significant role in determining breeding success for woodland birds. However, we examined a subset of species of conservation concern, and found higher DSR for these species in restoration plantings than in similarly sized woodland remnants. We also found negative effects of patch size and linearity on DSR in species of conservation concern. The primary cause of nest failure was predation (91%). We used camera trap imagery to identify the most common nest predators in our study sites: native predatory bird species, and the introduced red fox (Vulpes vulpes). Our findings are further evidence of the value of restoration plantings and small habitat patches for bird populations in fragmented agricultural landscapes. We recommend controlling for foxes to maximise the likelihood that restoration plantings and other woodland patches in Australia support breeding populations of woodland birds. More broadly, our study highlights the importance of taking a detailed, population-oriented approach to understanding factors that influence habitat suitability for fauna of conservation concern.
Australia's arid shrublands have been impacted by a variety of threatening processes since European settlement, and changes to ecosystem structure and function have been observed at multiple levels. ...The lack of recruitment and regeneration of the perennial shrub and tree layer in these communities has implications for many shrubland birds, including species of conservation concern such as the Chestnut‐rumped Thornbill (Acanthiza uropygialis: Acanthizidae). We documented foraging behaviour and habitat selection of the Chestnut‐rumped Thornbill at the Arid Recovery Reserve in South Australia and surveyed vegetation characteristics within the Reserve and in an adjacent pastoral property. We found that Chestnut‐rumped Thornbills preferentially use certain plant species: Callitris glaucophylla, Acacia aneura, Acacia ligulata and Acacia tetragonophylla, and that these species were significantly less abundant at our study sites outside the Reserve than inside. Major differences in the structure and composition of the vegetation inside and outside the Reserve suggest that changes in habitat structure and composition occurring in the broader landscape (outside the fenced area) decrease the suitability of arid shrubland habitat for the Chestnut‐rumped Thornbill and may contribute to their absence in unprotected areas. Our study indicates that deterioration of the perennial shrub layer could have significant consequences for the persistence of the Chestnut‐rumped Thornbill in arid rangelands. Our findings highlight the importance of rangeland management and restoration of Australia's arid shrublands in preventing declines of the Chestnut‐rumped Thornbill and other insectivorous birds.
We documented foraging behaviour and habitat selection of the Chestnut‐rumped Thornbill at the Arid Recovery Reserve in South Australia. We found that Chestnut‐rumped Thornbills preferentially use certain plant species, which were significantly less abundant outside the Reserve than inside. Changes in habitat structure and composition occurring in response to threatening processes may decrease the suitability of arid shrubland habitat for the Chestnut‐rumped Thornbill.
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