Gomis-Tena Julio, Brown Brandon M, Cano Jordi, Trenor Beatriz, Yang Pei-Chi, Saiz Javier, Clancy Colleen E, Romero Lucia
Centro de Investigación e Innovación en Bioingeniería (Ci2B), Universitat Politècnica de València, Camino de Vera, s/n, 46022 Valencia, Spain.
Department of Pharmacology, University of California, Davis, One Shields Avenue, Davis, California 95616-8636, United States.
J Chem Inf Model. 2020 Mar 23;60(3):1779-1790. doi: 10.1021/acs.jcim.9b01085. Epub 2020 Mar 10.
Preclinical assessment of drug-induced proarrhythmicity is typically evaluated by the potency of the drug to block the potassium human ether-à-go-go-related gene (hERG) channels, which is currently quantified by the IC. 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 IC that will help to decide whether the IC 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 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 IC protocol dependency relied on the tested compounds. Some of them showed no differences or small differences on the IC value, which suggests that the IC could be a good indicator of the blocking potency in these cases. However, others provided highly protocol dependent IC values, which could differ by even 2 orders of magnitude. Moreover, the protocols yielding the maximum IC and minimum IC depended on the drug, which complicates the definition of a "standard" protocol to minimize the influence of the stimulation protocol on the IC measurement in safety pharmacology. As a conclusion, we propose the adoption of our three-protocol IC assay to estimate the potency to block hERG in vitro. If the IC values obtained for a compound are similar, then the IC could be used as an indicator of its blocking potency, otherwise kinetics and state-dependent binding properties should be accounted.
药物诱导的致心律失常性的临床前评估通常通过药物阻断人类醚 - 去极化相关基因（hERG）通道的能力来评估，目前通过IC50进行量化。然而，通道阻断取决于实验条件。我们的目标是通过设计实验刺激方案来测量IC50，以改进对药物阻断能力的评估，这将有助于确定IC50是否具有足够的代表性。我们使用了心脏电生理活动的先进数学模型来设计三种刺激方案，这些方案增强了通道占据特定构象状态的概率差异，从而增强了化合物阻断效果的潜在差异。我们模拟了144种具有不同动力学和对通道构象状态亲和力的计算机模拟阻滞剂，并通过实验验证了我们的关键预测。我们的结果表明，IC50对方案的依赖性取决于所测试的化合物。其中一些在IC50值上没有差异或差异很小，这表明在这些情况下IC50可能是阻断能力的良好指标。然而，其他化合物提供的IC50值高度依赖于方案，甚至可能相差2个数量级。此外，产生最大IC50和最小IC50的方案取决于药物，这使得定义一个“标准”方案以最小化刺激方案对安全药理学中IC50测量的影响变得复杂。总之，我们建议采用我们的三方案IC50测定法来估计体外阻断hERG的能力。如果一种化合物获得的IC50值相似，那么IC50可以用作其阻断能力的指标，否则应考虑动力学和状态依赖性结合特性。
