Variability of manual patch clamp data on CaV1.2 and NaV1.5 channels generated using standardized protocols and following ICH S7B Q&A 2.1 best practices – Progress update of a HESI-coordinated multi-laboratory study

Abstract

Concomitant block of Ca_V1.2 and/or Na_V1.5 channels may mitigate Torsade de Pointes risk associated with hERG block. However, Ca_V1.2 channel block may cause bradycardia/hypotension; Na_V1.5 channel block may induce conduction slowing and sudden cardiac death in patients with structural heart diseases. Understanding drug effects on multiple cardiac ion channels can be of value for proarrhythmia risk assessment. Literature shows large degrees of lab-to-lab variability for drug potencies on cardiac ion channels. Ion channel data alignment with drug-induced ECG changes can thus be dataset-dependent. Lab-to-lab differences can arise from different experimental protocols and/or data quality. Thus, ICH S7B Q&A 2.1 was released to provide best practice recommendations for conducting cardiac ion channels assays to support proarrhythmia risk assessment. The goal of this HESI-coordinated, multi-laboratory research effort is to generate block potencies for 28 drugs in low, intermediate, and high proarrhythmia risk categories for hERG, Ca_V1.2, and peak and late Na_V1.5 currents with standardized protocols and best practices. This abstract focuses on the Ca_V1.2 and peak and late Na_V1.5 currents; hERG data are presented in a companion abstract (Alvarez-Baron et al.). Five laboratories conducted manual patch clamp experiments at near physiological temperatures on cell lines over-expressing Ca_V1.2 or Na_V1.5 channels. The research is ongoing, hence drug potencies are not presented. Instead, this abstract presents findings on data variability for each current, estimated using meta-analysis to account for drug-specific (i.e., potencies) and laboratory-specific effects. Systematic data variability was not observed from any laboratory for any current. After removing drug- and laboratory-specific effects, residual data variability was pooled across all drugs/laboratories to estimate overall assay variability. Variability measures for Ca_V1.2 and peak and late Na_V1.5 currents will be shared on the poster. This dataset can be compared with existing clinical data to understand nonclinical-clinical translation. Experiments on these three currents are ~75 % complete. Once complete, outcomes of this study will: 1) inform assay variability and support identification of safety margins for Ca_V1.2 and Na_V1.5 channels; and 2) produce a dataset to develop an in-silico myocyte model that can integrate multi-cardiac ion channel data for proarrhythmia risk prediction.