{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,23]],"date-time":"2026-10-23T19:44:28Z","timestamp":1792784668870,"version":"4.5.0"},"reference-count":35,"publisher":"American Chemical Society (ACS)","issue":"3","license":[{"start":{"date-parts":[[2020,7,13]],"date-time":"2020-07-13T00:00:00Z","timestamp":1594598400000},"content-version":"vor","delay-in-days":137,"URL":"https:\/\/pubs.acs.org\/page\/policy\/authorchoice_termsofuse.html"}],"funder":[{"name":"Ministerio de Economi\u00b4a y Competitividad and Fondo Europeo de Desarrollo Regional (FEDER)","award":["DPI2015-69125-R"],"award-info":[{"award-number":["DPI2015-69125-R"]}],"id":[{"id":"https:\/\/ror.org\/01txxn211","id-type":"ROR","asserted-by":"crossref"}]},{"name":"Ayuda a Primeros Proyectos de Investigaci\u00f3n  Universitat Polit\u00e8cnica de Val\u00e8ncia","award":["PAID-06-18"],"award-info":[{"award-number":["PAID-06-18"]}]},{"name":"Direcci\u00f3n General de Pol\u00edtica Cient\u00edfica de la Generalitat Valenciana","award":["PROMETEU2016\/088"],"award-info":[{"award-number":["PROMETEU2016\/088"]}],"id":[{"id":"https:\/\/ror.org\/0097mvx21","id-type":"ROR","asserted-by":"crossref"}]},{"name":"National Institutes of Health","award":["1R01HL128537-01A1"],"award-info":[{"award-number":["1R01HL128537-01A1"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"published-print":{"date-parts":[[2020,3,23]]},"abstract":"<jats:title>Abstract<\/jats:title>\n                  <jats:p>Preclinical assessment of drug-induced proarrhythmicity is typically evaluated by the potency of the drug to block the potassium human ether-a\u0300-go-go-related gene (hERG) channels, which is currently quantified by the IC50. However, channel block depends on the experimental conditions. Our aim is to improve the evaluation of the blocking potency of drugs by designing experimental stimulation protocols to measure the IC50 that will help to decide whether the IC50 is representative enough. We used the state-of-the-art mathematical models of the cardiac electrophysiological activity to design three stimulation protocols that enhance the differences in the probabilities to occupy a certain conformational state of the channel and, therefore, the potential differences in the blocking effects of a compound. We simulated an extensive set of 144 in silico IKr blockers with different kinetics and affinities to conformational states of the channel and we also experimentally validated our key predictions. Our results show that the IC50 protocol dependency relied on the tested compounds. Some of them showed no differences or small differences on the IC50 value, which suggests that the IC50 could be a good indicator of the blocking potency in these cases. However, others provided highly protocol dependent IC50 values, which could differ by even 2 orders of magnitude. Moreover, the protocols yielding the maximum IC50 and minimum IC50 depended on the drug, which complicates the definition of a \u201cstandard\u201d protocol to minimize the influence of the stimulation protocol on the IC50 measurement in safety pharmacology. As a conclusion, we propose the adoption of our three-protocol IC50 assay to estimate the potency to block hERG in vitro. If the IC50 values obtained for a compound are similar, then the IC50 could be used as an indicator of its blocking potency, otherwise kinetics and state-dependent binding properties should be accounted.<\/jats:p>","DOI":"10.1021\/acs.jcim.9b01085","type":"journal-article","created":{"date-parts":[[2020,2,27]],"date-time":"2020-02-27T13:01:01Z","timestamp":1582808461000},"page":"1779-1790","source":"Crossref","is-referenced-by-count":53,"title":["When Does the IC50 Accurately Assess the\nBlocking Potency of a Drug?"],"prefix":"10.1021","volume":"60","author":[{"given":"Julio","family":"Gomis-Tena","sequence":"first","affiliation":[{"name":"Universitat Polite\u0300cnica de Vale\u0300ncia , , Camino de Vera, s\/n , ,","place":["Valencia, Spain, 46022"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Brandon M.","family":"Brown","sequence":"additional","affiliation":[{"name":"University of California, Davis , , One Shields Avenue , , ,","place":["Davis, California, United States, 95616-8636"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9461-9848","authenticated-orcid":true,"given":"Jordi","family":"Cano","sequence":"additional","affiliation":[{"name":"Universitat Polite\u0300cnica de Vale\u0300ncia , , Camino de Vera, s\/n , ,","place":["Valencia, Spain, 46022"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Beatriz","family":"Trenor","sequence":"additional","affiliation":[{"name":"Universitat Polite\u0300cnica de Vale\u0300ncia , , Camino de Vera, s\/n , ,","place":["Valencia, Spain, 46022"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Pei-Chi","family":"Yang","sequence":"additional","affiliation":[{"name":"University of California, Davis , , One Shields Avenue , , ,","place":["Davis, California, United States, 95616-8636"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Javier","family":"Saiz","sequence":"additional","affiliation":[{"name":"Universitat Polite\u0300cnica de Vale\u0300ncia , , Camino de Vera, s\/n , ,","place":["Valencia, Spain, 46022"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Colleen E.","family":"Clancy","sequence":"additional","affiliation":[{"name":"University of California, Davis , , One Shields Avenue , , ,","place":["Davis, California, United States, 95616-8636"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4605-8630","authenticated-orcid":true,"given":"Lucia","family":"Romero","sequence":"additional","affiliation":[{"name":"Universitat Polite\u0300cnica de Vale\u0300ncia , , Camino de Vera, s\/n , ,","place":["Valencia, Spain, 46022"]}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"316","published-online":{"date-parts":[[2020,2,27]]},"reference":[{"key":"2026101606212257400_cit1","doi-asserted-by":"publisher","first-page":"199","DOI":"10.1016\/j.pharmthera.2008.04.010","article-title":"Preclinical\nTorsades-de-Pointes Screens: Advantages and Limitations of Surrogate\nand Direct Approaches in Evaluating Proarrhythmic Risk","volume":"119","author":"Gintant","year":"2008","journal-title":"Pharmacol. Ther."},{"key":"2026101606212257400_cit2","first-page":"61133","article-title":"International\nConference on Harmonisation; Guidance on S7B Nonclinical Evaluation\nof the Potential for Delayed Ventricular Repolarization (QT Interval\nProlongation) by Human Pharmaceuticals","volume":"70","author":"Food and Drug Administration.","year":"2005","journal-title":"Fed.\nRegist."},{"key":"2026101606212257400_cit3","doi-asserted-by":"publisher","first-page":"65","DOI":"10.1016\/s1056-8719(03)00041-8","article-title":"Troubleshooting\nProblems with in Vitro Screening of Drugs for QT Interval Prolongation\nUsing HERG K+ Channels Expressed in Mammalian Cell Lines and Xenopus\nOocytes","volume":"48","author":"Witchel","year":"2002","journal-title":"J. Pharmacol. Toxicol. Methods"},{"key":"2026101606212257400_cit4","doi-asserted-by":"publisher","first-page":"93","DOI":"10.1016\/j.vascn.2004.06.003","article-title":"Variability\nin the Measurement of HERG Potassium Channel Inhibition: Effects of\nTemperature and Stimulus Pattern","volume":"50","author":"Kirsch","year":"2004","journal-title":"J. Pharmacol.\nToxicol. Methods"},{"key":"2026101606212257400_cit5","doi-asserted-by":"publisher","first-page":"146","DOI":"10.1016\/j.vascn.2005.04.008","article-title":"Estimation\nof Potency of HERG Channel Blockers: Impact of Voltage Protocol and\nTemperature","volume":"52","author":"Yao","year":"2005","journal-title":"J. Pharmacol. Toxicol. Methods"},{"key":"2026101606212257400_cit6","doi-asserted-by":"publisher","first-page":"1368","DOI":"10.1038\/sj.bjp.0707356","article-title":"State Dependent\nDissociation of HERG\nChannel Inhibitors","volume":"151","author":"Stork","year":"2009","journal-title":"Br. J. 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Pharmacol."},{"key":"2026101606212257400_cit29","doi-asserted-by":"publisher","first-page":"233","DOI":"10.1016\/j.vascn.2016.05.005","article-title":"A Temperature-Dependent\nin Silico Model of the Human\nEther-a\u0300-Go-Go-Related (HERG) Gene Channel","volume":"81","author":"Li","year":"2016","journal-title":"J. Pharmacol. Toxicol. Methods"},{"key":"2026101606212257400_cit30","doi-asserted-by":"publisher","first-page":"292","DOI":"10.1016\/j.ahj.2013.11.004","article-title":"Rechanneling\nthe Cardiac Proarrhythmia Safety Paradigm: A Meeting Report from the\nCardiac Safety Research Consortium","volume":"167","author":"Sager","year":"2014","journal-title":"Am. Heart\nJ."},{"key":"2026101606212257400_cit31","doi-asserted-by":"publisher","first-page":"1","DOI":"10.1124\/mol.115.103127","article-title":"Temperature Effects\non Kinetics of Kv11.1 Drug Block Have Important Consequences for in\nSilico Proarrhythmic Risk Prediction","volume":"90","author":"Windley","year":"2016","journal-title":"Mol. Pharmacol."},{"key":"2026101606212257400_cit32","doi-asserted-by":"publisher","DOI":"10.1161\/circep.116.004628","article-title":"Improving\nthe In Silico Assessment of Proarrhythmia Risk by Combining HERG (Human\nEther-a\u0300-Go-Go-Related Gene) Channel-Drug Binding Kinetics and\nMultichannel Pharmacology","volume":"10","author":"Li","year":"2017","journal-title":"Circ.: Arrhythmia\nElectrophysiol."},{"key":"2026101606212257400_cit33","doi-asserted-by":"publisher","first-page":"616","DOI":"10.3389\/fphys.2017.00616","article-title":"Optimization of an\nIn Silico Cardiac Cell Model for Proarrhythmia\nRisk Assessment","volume":"8","author":"Dutta","year":"2017","journal-title":"Front. Physiol."},{"key":"2026101606212257400_cit34","doi-asserted-by":"publisher","first-page":"99","DOI":"10.1016\/j.vascn.2017.02.017","article-title":"Measuring Kinetics and Potency of\nHERG Block for CiPA","volume":"87","author":"Windley","year":"2017","journal-title":"J. Pharmacol. 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