Identification and Characterization of a Compound That Protects Cardiac Tissue from Human Ether-à-go-go-related Gene (hERG)-related Drug-induced Arrhythmias

F Potet ,Sabina Kupershmidt,David Afshartous,Alfred L George,Corey R Hopkins,Jeffrey R Balser,Veniamin Y Sidorov,Beiyan Zou,Emily Days,Craig W Lindsley,Svetlana Z Stepanovic,Raghav Venkataraman,Darren W Engers,Min Li,C David Weaver ,Lundy Lewis ,Amanda Lorinc ,Courtney Campbell ,Sébastien Chaigne ,Franz Baudenbacher

doi:10.1074/jbc.m112.380162

F Potet , Sabina Kupershmidt + Show 18 more

Open Access

https://doi.org/10.1074/jbc.m112.380162

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Abstract

The human Ether-à-go-go-related gene (hERG)-encoded K(+) current, I(Kr) is essential for cardiac repolarization but is also a source of cardiotoxicity because unintended hERG inhibition by diverse pharmaceuticals can cause arrhythmias and sudden cardiac death. We hypothesized that a small molecule that diminishes I(Kr) block by a known hERG antagonist would constitute a first step toward preventing hERG-related arrhythmias and facilitating drug discovery. Using a high-throughput assay, we screened a library of compounds for agents that increase the IC(70) of dofetilide, a well characterized hERG blocker. One compound, VU0405601, with the desired activity was further characterized. In isolated, Langendorff-perfused rabbit hearts, optical mapping revealed that dofetilide-induced arrhythmias were reduced after pretreatment with VU0405601. Patch clamp analysis in stable hERG-HEK cells showed effects on current amplitude, inactivation, and deactivation. VU0405601 increased the IC(50) of dofetilide from 38.7 to 76.3 nM. VU0405601 mitigates the effects of hERG blockers from the extracellular aspect primarily by reducing inactivation, whereas most clinically relevant hERG inhibitors act at an inner pore site. Structure-activity relationships surrounding VU0405601 identified a 3-pyridiyl and a naphthyridine ring system as key structural components important for preventing hERG inhibition by multiple inhibitors. These findings indicate that small molecules can be designed to reduce the sensitivity of hERG to inhibitors.

Highlights

Inhibition of the cardiac human Ether-à-go-go-related gene (hERG) channel by essential pharmaceuticals is unpredictable and leads to fatal arrhythmias
In all experiments where we examine the test drug (VU0405601 or PD-118057) in the presence of a given hERG inhibitor, the test drug was applied to the bath first, and the pulse protocols were applied until the full effects were observed; only did we apply dofetilide and continue the pulse protocols
VU0405601 Protects Cardiac Tissue from Dofetilide-induced Ventricular Tachycardia—Determining the relative clinical risk of hERG-related arrhythmias requires the use of a complex cardiac model

Summary

Background

Inhibition of the cardiac hERG channel by essential pharmaceuticals is unpredictable and leads to fatal arrhythmias. We hypothesized that a small molecule that diminishes IKr block by a known hERG antagonist would constitute a first step toward preventing hERG-related arrhythmias and facilitating drug discovery. Structure-activity relationships surrounding VU0405601 identified a 3-pyridiyl and a naphthyridine ring system as key structural components important for preventing hERG inhibition by multiple inhibitors These findings indicate that small molecules can be designed to reduce the sensitivity of hERG to inhibitors. Novel Approaches to Antiarrhythmic Therapy cule that diminishes IKr block by a known hERG antagonist would constitute a first step toward preventing hERG-related arrhythmias and facilitate drug discovery. We identified one lead compound, VU0405601, via high-throughput screening, utilizing a fluorescence-based thallium (Tlϩ) influx assay [16] for agents that increased the IC70 of dofetilide, a class III antiarrhythmic [17]

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DISCUSSION