Zatebradine (UL-FS-49 (free base)) is a potent inhibitor of hyperpolarization-activated cyclic nucleotide-gated (HCN) channels with an IC50 values 1.96 µM. Zatebradine blocks the slow inward current through human HCN1, HCN2, HCN3 and HCN4 channels, with IC50 values of 1.83 µM, 2.21 µM, 1.90 µM and 1.88 µM, respectively[1].
The use-dependent blockade by Zatebradine of the cardiac pacemaker current from rabbit sino-atrial node cells has an apparent Kd of 480 nM[2].
Zatebradine (0-20 mg/kg; intraperitoneal injection; for 30 minutes; male C57/Bl6-mice) reduces the heart rate dose-dependently from 600 to 200 bpm with ED50 value of 1.8 mg/kg and induces increasing arrhythmia[1].
References:
[1]. Stieber J, et al. Bradycardic and proarrhythmic properties of sinus node inhibitors. Mol Pharmacol. 2006 Apr;69(4):1328-37. Epub 2005 Dec 30.
[2]. Van Bogaert PP, et al. Use-dependent blockade of cardiac pacemaker current (If) by cilobradine and zatebradine. Eur J Pharmacol. 2003 Oct 8;478(2-3):161-71.