Optimisation and validation of a medium-throughput electrophysiology-based hERG assay using IonWorks HT

Area of Science:

• Pharmacology
• Biophysics
• Drug Discovery

Background:

• Drug-induced QT interval prolongation is a major safety concern.
• The human ether-a-go-go-related gene (hERG) K+ channel is the primary target for this risk.
• Developing efficient assays for hERG inhibition is crucial for drug safety.

Purpose of the Study:

• To validate a medium-throughput electrophysiology method (IonWorks HT) for assessing hERG channel function.
• To compare the performance of IonWorks HT with conventional low-throughput electrophysiology and an indirect assay (Rb+ efflux).
• To determine the optimal conditions for IonWorks HT to ensure accurate potency measurements.

Main Methods:

• Compared electrophysiological and pharmacological properties of hERG using conventional and IonWorks HT methods.
• Evaluated the impact of cell concentration on IonWorks HT results.
• Compared IonWorks HT data with an indirect Rb+ efflux assay.

Main Results:

• Basic hERG electrophysiological properties were similar between conventional and IonWorks HT methods.
• Increasing cell concentration in IonWorks HT decreased reported compound potency.
• IonWorks HT potency values (pIC50) correlated well with conventional electrophysiology at low cell concentrations (r=0.90-0.94).
• The indirect Rb+ efflux assay reported compounds as approximately 6-fold less potent than IonWorks HT.

Conclusions:

• The IonWorks HT assay, using low cell concentrations, provides reliable potency data comparable to conventional electrophysiology.
• Optimizing cell concentration is key to mitigating potential artifacts like compound partitioning.
• IonWorks HT offers a direct assessment of hERG channel function suitable for influencing early chemical design.