Mikhail Ann, Fischer Cristina, Patel Ameesha, Long Michelle A, Limberis James T, Martin Ruth L, Cox Bryan F, Gintant Gary A, Su Zhi
Department of Integrative Pharmacology, Abbott, Abbott Park, Illinois 60064, USA.
J Cardiovasc Pharmacol. 2007 May;49(5):269-74. doi: 10.1097/FJC.0b013e318036dd05.
Delayed cardiac repolarization and fatal proarrhythmia have been linked to block of the repolarizing current, Ikr or hERG (human ether-a-go-go related gene) current. Thus, determining the potency of hERG block is critical in evaluating cardiac safety during preclinical development. Hydroxypropyl beta-cyclodextrins (HbetaC) are cyclic oligosaccharides used to enhance drug solubility. To evaluate the utility of HbetaC to enhance drug solubility in hERG screening assays, we studied the effect of HbetaC on hERG current and the sensitivity of the hERG assay to 3 structurally different hERG blocking drugs using whole-cell voltage clamp technique and HEK-293 cells expressing the hERG channel. HbetaC inhibited hERG activation and tail current and accelerated current deactivation in a concentration-dependent manner. HbetaC (6%) reduced the apparent potency of block by terfenadine (IC50 12000 nM vs 45 nM), cisapride (IC50 281 nM vs 28 nM), and E-4031 (163 nM vs 26 nM). Reduced potency of block was consistent with loss of activity as a result of complexation with HbetaC by terfenadine and cisapride (demonstrated in solubility studies) and interactions with HbetaC by E-4031 (demonstrated in absorbance studies). These results demonstrate that HbetaC is an unsuitable agent for enhancing compound solubility in the in vitro hERG current assay and may mask drug effects, allowing potentially dangerous drugs to advance into clinical development.
心脏复极化延迟和致命性心律失常与复极电流（Ikr或hERG（人ether-a-go-go相关基因）电流）的阻断有关。因此，在临床前开发过程中，确定hERG阻断的效力对于评估心脏安全性至关重要。羟丙基-β-环糊精（HbetaC）是用于提高药物溶解度的环状寡糖。为了评估HbetaC在hERG筛选试验中提高药物溶解度的效用，我们使用全细胞电压钳技术和表达hERG通道的HEK-293细胞，研究了HbetaC对hERG电流的影响以及hERG试验对3种结构不同的hERG阻断药物的敏感性。HbetaC以浓度依赖性方式抑制hERG激活和尾电流，并加速电流失活。HbetaC（6%）降低了特非那定（IC50为12000 nM对45 nM）、西沙必利（IC50为281 nM对28 nM）和E-4031（163 nM对26 nM）的表观阻断效力。阻断效力降低与特非那定和西沙必利（在溶解度研究中证实）与HbetaC络合以及E-4031（在吸光度研究中证实）与HbetaC相互作用导致的活性丧失一致。这些结果表明，HbetaC不是在体外hERG电流试验中提高化合物溶解度的合适试剂，可能会掩盖药物效应，使潜在危险药物进入临床开发阶段。
