Blockers of the Kv1.5 Channel for the Treatment of Atrial Arrhythmias [1]

Atrial arrhythmias are a common problem in cardiological practice. Despite the availability of several antiarrhythmic drugs, there is a medical need for safer and more efficient antiarrhythmic treatment. Compounds that act atrial selectively without prolonging the QTc-time and without negative inotropy to terminate and / or prevent atrial arrhythmias would be of high interest. In this context, the voltage-gated potassium channel Kv1.5 is regarded as a promising target to achieve atrial selectivity, which in turn would be associated with fewer side effects than classical antiarrhythmics. This review summarizes patents and other publications on compounds which show this novel mode of action. The chemistry, selectivity and structure-activity data disclosed in the literature are discussed in light of recent work demonstrating the antiarrhythmic efficacy of Kv1.5 blockers in vivo. Several studies in pig, dog or goat models have confirmed their proposed atrial selective antiarrhythmic effect in vivo. Most of the more intensively characterized Kv1.5 blockers have turned out not to be selective but also block other ion channels. Based on the currently available data it seems that additional inhibition of Kv4.3 and KACh is beneficial for the desired antiarrhythmic effect or at least does not hamper the atrial selectivity of a Kv1.5 blocker. Significant block of IK1, HERG or sodium channels, however, clearly leads to loss of atrial selectivity and increases the risk of lethal ventricular proarrhythmia.