Cardiac sodium channel antagonism – Translation of preclinical in vitro assays to clinical QRS prolongation

Introduction

Cardiac sodium channel antagonists have historically been used to treat cardiac arrhythmias by preventing the re-entry of the electrical impulse that could occur following myocardial damage. However, clinical studies have highlighted a significant increase in mortality associated with such treatment. Cardiac sodium channel antagonist activity is now seen as an off-target pharmacology that should be mitigated during the drug development process. The aim of this study was to examine the correlation between in vitro/ex vivo assays that are routinely used to measure Na_V1.5 activity and determine the translatability of the individual assays to QRS prolongation in the clinic.

Methods

A set of clinical compounds with known Na_V1.5 activity was profiled in several in vitro/ex vivo assays (binding, membrane potential, patch clamp and the Langendorff isolated heart). Clinical data comprising compound exposure levels and changes in QRS interval were obtained from the literature. Sensitivity/specificity analysis was performed with respect to the clinical outcome.

Results

The in vitro assays showed utility in predicting QRS prolongation in the clinic. Optimal thresholds were defined for each assay (binding: IC₂₀; membrane potential: IC10; patch clamp: IC₂₀) and sensitivity (69–88%) and specificity (53–84%) values were shown to be similar between assay formats.
Discussion

The data provide clear statistical insight into the translatability of Na_V1.5 antagonism data generated in vitro to potential clinical outcomes. These results improve our ability to understand the liability posed by such activity in novel development compounds at an early stage.