Qu Yusheng, Gao Baoxi, Fang Mei, Vargas Hugo M
Safety and Exploratory Pharmacology, Toxicological Sciences, Amgen Inc., Thousand Oaks, CA 91320, USA.
J Pharmacol Toxicol Methods. 2013 Jul-Aug;68(1):74-81. doi: 10.1016/j.vascn.2013.03.001. Epub 2013 Mar 19.
Cardiac safety is of paramount importance in contemporary drug development. Efficient and sensitive evaluation of cardiac safety in the research and development of new molecular agents begins with preclinical in-vitro models. A new model that is currently under evaluation is the human embryonic stem-cell derived cardiac myocytes (hESC-CM) (Peng, Lacerda, Kirsch, Brown, & Bruening-Wright, 2010).
hESC-CM were exposed in-vitro to 15 test compounds, and action potentials (AP) recorded with perforated patch-clamp technique to assess changes in AP duration (APD90) and upstroke velocity (Vmax). The test compounds included: 10 hERG channel, 4 Na⁺ channel, and 1 IKs channel inhibitors. For comparison purposes, the test compounds were evaluated in the isolated rabbit heart assay (IRH) to determine changes in conduction (QRS) and repolarization (QTc). Potency at hERG, NaV1.5 and IKs channel was also determined.
For 7 of 10 hERG channel inhibitors, the potency values across the three functional assays were similar (≤5-fold). Three compounds (dofetilide, sertindole, and terfenadine) showed >10-fold discrepancy between hERG potency and inhibitory concentrations in the hESC-CM and IRH assays. Of the four Na⁺ channel inhibitors, only mexiletine exhibited similar potency values across the three assays (~3-fold); the others exhibited marked variation (>10-fold) in inhibitory potency. No effect on repolarization was observed in hESC-CM treated with a potent IKs blocker, but QTc prolongation was evident in the IRH.
The functional data indicate that hESC-CM are sensitive for detecting repolarization delay induced by hERG channel blockade, and AP prolongation correlated with potency in the hERG channel and IRH assays. However, hESC-CM were less sensitive for detecting depolarizing delay by Na⁺ channel blockers, and unable to detect delayed repolarization caused by IKs blockade.
心脏安全性在当代药物研发中至关重要。在新分子药物的研发过程中，对心脏安全性进行高效且灵敏的评估始于临床前体外模型。目前正在评估的一种新模型是人类胚胎干细胞衍生的心肌细胞（hESC-CM）（彭、拉塞达、基尔希、布朗和布鲁宁-赖特，2010年）。
将hESC-CM在体外暴露于15种受试化合物，采用穿孔膜片钳技术记录动作电位（AP），以评估动作电位时程（APD90）和除极速度（Vmax）的变化。受试化合物包括：10种hERG通道抑制剂、4种Na⁺通道抑制剂和1种IKs通道抑制剂。为作比较，在离体兔心试验（IRH）中对受试化合物进行评估，以确定传导（QRS）和复极（QTc）的变化。还测定了受试化合物对hERG、NaV1.5和IKs通道的效力。
10种hERG通道抑制剂中的7种，在三种功能试验中的效力值相似（≤5倍）。三种化合物（多非利特、舍吲哚和特非那定）在hERG效力与hESC-CM和IRH试验中的抑制浓度之间显示出>10倍的差异。在四种Na⁺通道抑制剂中，只有美西律在三种试验中的效力值相似（约3倍）；其他抑制剂的抑制效力表现出显著差异（>10倍）。用强效IKs阻滞剂处理的hESC-CM未观察到复极变化，但在IRH中QTc延长明显。
功能数据表明，hESC-CM对检测由hERG通道阻滞引起的复极延迟敏感，且动作电位延长与hERG通道和IRH试验中的效力相关。然而，hESC-CM对检测Na⁺通道阻滞剂引起的去极化延迟不太敏感，并且无法检测由IKs阻滞引起的延迟复极。
