Guo Liang, Guthrie Heather
Hoffmann-La Roche, Inc., Non-clinical Drug Safety, Nutley, NJ 07110-1199, USA.
J Pharmacol Toxicol Methods. 2005 Jul-Aug;52(1):123-35. doi: 10.1016/j.vascn.2005.04.002.
The human ether-a-go-go-related gene (hERG) potassium channel plays a major role in the electrical conductances involved in human heart repolarization. Drugs that decrease hERG K(+) currents are at risk to produce a prolongation of the cardiac action potential, resulting in an increase of the QT interval. Drug-induced QT prolongation or acquired long QT (aLQT) can lead to a fatal arrhythmia known as Torsade de Pointes (TdP). Electrophysiological methods are the best approach to evaluate potential drug candidates for hERG current inhibition. Here we identify limitations with the PatchXpress 7000A automated electrophysiology instrument and describe hERG protocol optimizations necessary for reliable preclinical assessment.
The PatchXpress 7000A automated electrophysiology system was used to evaluate a group of drugs with known hERG activity under voltage clamp conditions. We used a recombinant cell line expressing hERG, and assessed the inhibition of hERG K(+) currents at different drug concentrations. These data were used to determine hERG IC(50) values and compare assay parameters under different recording conditions.
We found that due to limitations with the PatchXpress 7000A instrument, repeated compound additions were critical for achieving steady state drug concentrations that generated data comparable to standard patch clamp methods, particularly when similar voltage pulse protocols were implemented. Some discrepancies were observed between the PatchXpress 7000A and standard patch clamp techniques including shifts in IC(50) values for very hydrophobic compounds. Most hERG IC(50) values were within 3-fold of standard patch clamp IC(50) values.
Automation of electrophysiology technologies has greatly improved the throughput of assessing lead drug candidates for hERG liability. To maintain hERG data quality comparable to standard patch clamp techniques, the PatchXpress 7000A instrument limitations should be recognized and protocols optimized accordingly to ensure accuracy.
人类醚 - 去极化相关基因（hERG）钾通道在参与人类心脏复极化的电导中起主要作用。降低hERG钾电流的药物有导致心脏动作电位延长的风险，从而导致QT间期延长。药物诱导的QT延长或获得性长QT（aLQT）可导致一种致命的心律失常，即尖端扭转型室速（TdP）。电生理方法是评估潜在hERG电流抑制候选药物的最佳方法。在此，我们确定了PatchXpress 7000A自动电生理仪器的局限性，并描述了可靠的临床前评估所需的hERG实验方案优化。
使用PatchXpress 7000A自动电生理系统在电压钳条件下评估一组已知hERG活性的药物。我们使用表达hERG的重组细胞系，并评估不同药物浓度下hERG钾电流的抑制情况。这些数据用于确定hERG半数抑制浓度（IC50）值，并比较不同记录条件下的实验参数。
我们发现，由于PatchXpress 7000A仪器的局限性，重复添加化合物对于达到稳态药物浓度至关重要，该浓度产生的数据与标准膜片钳方法相当，特别是当实施相似的电压脉冲方案时。在PatchXpress 7000A和标准膜片钳技术之间观察到一些差异，包括非常疏水化合物的IC50值的变化。大多数hERG IC50值在标准膜片钳IC50值的3倍以内。
电生理技术的自动化极大地提高了评估hERG相关先导药物候选物的通量。为了保持与标准膜片钳技术相当的hERG数据质量，应认识到PatchXpress 7000A仪器的局限性，并相应地优化实验方案以确保准确性。
