Rb+ Flux through hERG Channels Affects the Potency of Channel Blocking Drugs: Correlation with Data Obtained Using a High-Throughput Rb+ Efflux Assay

Rezazadeh, Saman; Hesketh, J. Christian; Fedida, David

doi:10.1177/1087057104264798

Cited by 57 publications

(32 citation statements)

References 23 publications

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“…This has been proposed to contribute to a right shift of IC 50 values for known compounds inhibiting hERG potassium channels. 40 In this case, using a higher concentration of testing compounds may yield a better overlap of hits identified by two different assays. Analysis of the Tl þ assay hits identified at 10 mM testing compound concentration ( Table 1 and Supplementary Fig.…”

Section: Discussionmentioning

confidence: 99%

“…Second, based on studies using known inhibitors of hERG potassium channels, it is clear that different compounds display varying degrees of right shift of potency, as large as 100-fold, in surrogate ion-based flux assays. 40 Therefore, the structural features of testing compounds may differentially affect the inhibitory potency in each assay. This factor may be especially more pronounced for hERG than for other channels because hERG is inhibited by a variety of structural classes.…”

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Profiling Diverse Compounds by Flux- and Electrophysiology-Based Primary Screens for Inhibition of Human Ether-à-go-go Related Gene Potassium Channels

Zou

Babcock

et al. 2010

ASSAY and Drug Development Technologies

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Compound effects on cloned human Ether-à-go-go related gene (hERG) potassium channels have been used to assess the potential cardiac safety liabilities of drug development candidate compounds. In addition to radioactive ligand displacement tests, two other common approaches are surrogate ion-based flux assays and electrophysiological recordings. The former has much higher throughput, whereas the latter measures directly the effects on ionic currents. Careful characterization in earlier reports has been performed to compare the relative effectiveness of these approaches for known hERG blockers, which often yielded good overall correlation. However, cases were reported showing significant and reproducible differences in potency and/or sensitivity by the two methods. This raises a question concerning the rationale and criteria on which an assay should be selected for evaluating unknown compounds. To provide a general basis for considering assays to profile large compound libraries for hERG activity, we have conducted parallel flux and electrophysiological analyses of 2,000 diverse compounds, representative of the 300,000 compound collection of NIH Molecular Library Small Molecular Repository (MLSMR). Our results indicate that at the conventional testing concentration 1.0 mM, the overlap between the two assays ranges from 32% to 50% depending on the hit selection criteria. There was a noticeable rate of false negatives by the thallium-based assay relative to electrophysiological recording, which may be greatly reduced under modified comparative conditions. As these statistical results identify a preferred method for cardiac safety profiling of unknown compounds, they suggest an efficient method combining flux and electrophysiological assays to rapidly profile hERG liabilities of large collection of naive compounds.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Profiling Diverse Compounds by Flux- and Electrophysiology-Based Primary Screens for Inhibition of Human Ether-à-go-go Related Gene Potassium Channels

Zou

Babcock

et al. 2010

ASSAY and Drug Development Technologies

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“…TOXICOLOGIC PATHOLOGY Another indirect approach employed to detect hERG channel-drug interactions is the ion flux assay. This assay measures reduced levels of radiolabeled Rb + efflux (reflecting diminished outward K + current through hERG channels) from hERG-transfected cells (Rezazadeh et al, 2004). Voltage-sensitive dyes have also been used to measure druginduced membrane depolarization of hERG transfected cells in which hERG/I Kr is the primary potassium current responsible for setting the resting membrane potential (Netzer et al, 2003).…”

Section: Approaches To Evaluate Drug Effects On Herg Indirect Techniqmentioning

confidence: 99%

Utility of hERG Assays as Surrogate Markers of Delayed Cardiac Repolarization and QT Safety

Gintant

Martin

et al. 2006

Toxicol Pathol

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HERG (human-ether-a-go-go-related gene) encodes for a cardiac potassium channel that plays a critical role in defining ventricular repolarization. Noncardiovascular drugs associated with a rare but potentially lethal ventricular arrhythmia (Torsades de Pointes) have been linked to delayed cardiac repolarization and block of hERG current. This brief overview will discuss the role of hERG current in cardiac electrophysiology, its involvement in drug-induced delayed repolarization, and approaches used to define drug effects on hERG current. In addition, examples of hERG blocking drugs acting differently (i.e., overt and covert hERG blockade due to multichannel block) together with the utility and limitations of hERG assays as tools to predict the risk of delayed repolarization and proarrhythmia are discussed.

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“…However those models have not yet produced satisfactory predictions given limited compounds and differential data quality caused by variations in detection methodologies. Several high-throughput screening approaches have been established for identification of hERG modulators, including ion flux assay (Rb + ) and fluorescence-based assay (Tl + ), etc [8,[35][36][37][38] . Although these assays could identify hERG modulators effectively and showed better correlation with electrophysiological assays, the interferences from the parental cells may interact with compounds, and thus cause higher false-positive or falsenegative hit rate [7] .…”

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confidence: 99%

Investigation of miscellaneous hERG inhibition in large diverse compound collection using automated patch-clamp assay

Zou

Wang

et al. 2016

Acta Pharmacol Sin

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Aim: hERG potassium channels display miscellaneous interactions with diverse chemical scaffolds. In this study we assessed the hERG inhibition in a large compound library of diverse chemical entities and provided data for better understanding of the mechanisms underlying promiscuity of hERG inhibition.Methods: Approximately 300 000 compounds contained in Molecular Library Small Molecular Repository (MLSMR) library were tested. Compound profiling was conducted on hERG-CHO cells using the automated patch-clamp platform-IonWorks Quattro TM .Results: The compound library was tested at 1 and 10 μmol/L. IC 50 values were predicted using a modified 4-parameter logistic model. Inhibitor hits were binned into three groups based on their potency: high (IC 50 <1 μmol/L), intermediate (1 μmol/L< IC 50 <10 μmol/L), and low (IC 50 >10 μmol/L) with hit rates of 1.64%, 9.17% and 16.63%, respectively. Six physiochemical properties of each compound were acquired and calculated using ACD software to evaluate the correlation between hERG inhibition and the properties: hERG inhibition was positively correlative to the physiochemical properties ALogP, molecular weight and RTB, and negatively correlative to TPSA. Conclusion: Based on a large diverse compound collection, this study provides experimental evidence to understand the promiscuity of hERG inhibition. This study further demonstrates that hERG liability compounds tend to be more hydrophobic, high-molecular, flexible and polarizable.Keywords: hERG; high-throughput screening; MLSMR library; automated electrophysiology; cardiotoxicity Acta Pharmacologica Sinica (2016) 37: 111−123; doi: 10.1038/aps.2015 Original Article IntroductionThe acquired long QT syndrome is both a threat to public health and a major stumbling block for drug development [1] . It is most often caused through unintended blockade of the cardiac repolarizing potassium channel, I Kr , encoded by the Human Ether-a-go-go related gene (hERG) [2] . Blockade of hERG channel was found to be associated with an increased duration of ventricular repolarization and prolongation of QT interval (long QT syndrome, or LQTS). hERG potassium channel displays promiscuous interactions with diverse chemical scaffolds [3] . Structurally and functionally unrelated drugs have been shown to block hERG channel, and some of these agents, including terfenadine, astemizole, droperidol and cisapride, etc, have been withdrawn from the market due to their potential to predispose individuals to sudden cardiac death. Due to the important implications in both drug discovery [4] and clinical practice, evaluation of hERG liability has been required for any new chemical entities by regulatory agencies according to the ICH S7B guideline since 2005 [5] .Manual patch clamp method is considered as gold standard for ion channel functional evaluation [6] . However the method is very labor-intensive with low throughput, and thus its application in drug discovery is limited. Ion flux assays with surrogate ions of Rubidium (Rb + ) or Thallium (Tl + ) have ...

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Rb+ Flux through hERG Channels Affects the Potency of Channel Blocking Drugs: Correlation with Data Obtained Using a High-Throughput Rb+ Efflux Assay

Cited by 57 publications

References 23 publications

Profiling Diverse Compounds by Flux- and Electrophysiology-Based Primary Screens for Inhibition of Human Ether-à-go-go Related Gene Potassium Channels

Profiling Diverse Compounds by Flux- and Electrophysiology-Based Primary Screens for Inhibition of Human Ether-à-go-go Related Gene Potassium Channels

Utility of hERG Assays as Surrogate Markers of Delayed Cardiac Repolarization and QT Safety

Investigation of miscellaneous hERG inhibition in large diverse compound collection using automated patch-clamp assay

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