Discovery of a new mexiletine-derived agonist of the hERG K+channel

The human Ether-a-go-go Related Gene (hERG) potassium channel plays a central role in the rapid component (IKr) of cardiac action potential repolarization phase. A large number of structurally different compounds block hERG and cause a high risk of arrhythmias. Among the drugs that block hERG channel, a few compounds have been identified as hERG channel activators. Such compounds may be useful, at least in theory, for the treatment of long term QT syndrome. Here we describe a new activator of hERG channel, named MC450. This compound is a symmetric urea, derived from (R)-mexiletine. Using patch-clamp recordings, we found that MC450 increased the activation current of hERG channel, with an EC50of 41 ± 4 μM. Moreover MC450 caused a depolarizing shift in the voltage dependence of inactivation from − 64.1 ± 1.2 mV (control), to − 35.9 ± 1.4 mV, whereas it had no effect on the voltage dependence of activation. Furthermore, MC450 slowed current inactivation and the effect of MC450 was attenuated by the inactivation-impaired double mutant G628C/S631C.