LUF7244, an allosteric modulator/activator of K _v11.1 channels, counteracts dofetilide-induced torsades de pointes arrhythmia in the chronic atrioventricular block dog model

Background and Purpose: K _v11.1 (hERG) channel blockade is an adverse effect of many drugs and lead compounds, associated with lethal cardiac arrhythmias. LUF7244 is a negative allosteric modulator/activator of K _v11.1 channels that inhibits early afterdepolarizations in vitro. We tested LUF7244 for antiarrhythmic efficacy and potential proarrhythmia in a dog model. Experimental Approach: LUF7244 was tested in vitro for (a) increasing human I _Kv11.1 and canine I _Kr and (b) decreasing dofetilide-induced action potential lengthening and early afterdepolarizations in cardiomyocytes derived from human induced pluripotent stem cells and canine isolated ventricular cardiomyocytes. In vivo, LUF7244 was given intravenously to anaesthetized dogs in sinus rhythm or with chronic atrioventricular block. Key Results: LUF7244 (0.5–10 μM) concentration dependently increased I _Kv11.1 by inhibiting inactivation. In vitro, LUF7244 (10 μM) had no effects on I _KIR2.1, I _Nav1.5, I _Ca-L, and I _Ks, doubled I _Kr, shortened human and canine action potential duration by approximately 50%, and inhibited dofetilide-induced early afterdepolarizations. LUF7244 (2.5 mg·kg ⁻¹·15 min ⁻¹) in dogs with sinus rhythm was not proarrhythmic and shortened, non-significantly, repolarization parameters (QTc: −6.8%). In dogs with chronic atrioventricular block, LUF7244 prevented dofetilide-induced torsades de pointes arrhythmias in 5/7 animals without normalization of the QTc. Peak LUF7244 plasma levels were 1.75 ± 0.80 during sinus rhythm and 2.34 ± 1.57 μM after chronic atrioventricular block. Conclusions and Implications: LUF7244 counteracted dofetilide-induced early afterdepolarizations in vitro and torsades de pointes in vivo. Allosteric modulators/activators of K _v11.1 channels might neutralize adverse cardiac effects of existing drugs and newly developed compounds that display QTc lengthening.