Voltage-gated potassium ERG channels (Kv11.1), encoded by the ether-a-go-go related gene, mediate the inwardly rectifying potassium (K+) current that repolarizes myocardial cells, gut smooth muscle cells, and interstitial cells of Cajal. E-4031 is a methanesulfonanilide class III antiarrhythmic agent that prolongs cardiac action potential duration by blocking ERG K+ channels (IC50 = 29 nM). E-4031 inhibits the ERG1, ERG2, and ERG3 isoforms with KD values of 99, 116, and 193 nM, respectively. However, at higher μM concentrations E-4031 can demonstrate pro-arrhythmic activity, inducing early after depolarizations (prolonged repolarization) in cell models and torsade de pointes in animal models. E-4031 has been used to pharmacologically rescue misprocessed ERG in long QT syndrome type 2, an autosomal dominant cardiac disease associated with prolongation of the QT interval and torsade de pointes.
