hERG-IN-3 is an orally active hERG inhibitor with an IC50 of 44.5 nM. It has a Ki value of 14 nM for the beta2-adrenergic receptor. hERG-IN-3 exhibits skeletal muscle Nav1.4 sodium channel blocking activity with an IC50 of 4.4 µM, which is three times higher than that for hNav1.5. In animal models, hERG-IN-3 demonstrates potent antimyotonic activity and can be utilized in the study of congenital myotonia.