Japan Tobacco developed JTV-519 (known also as K201) as an antiarrhythmic agent. This drug was in Phase II trials for the potential treatment of Atrial Fibrillation, but study was terminated. In experimental myofibrillar overcontraction models, JTV-519 demonstrated greater cardioprotectant effects than propranolol, also, this drug investigated against heart failure, but then these researches have been discontinued. In addition, K201 was in phase II clinical trial for investigation its topical implementation for Atopic Dermatitis. The mechanism of its action is both complex and controversial, known that it is a non-specific blocker of sodium, potassium and calcium channels (multiple-channel blocker). It is believed to stabilize the closed state of the RyR2 (cardiac ryanodine receptor) by increasing its affinity for the FKBP12.6 (12.6 kDa FK506 binding protein), in addition was suggested, that suppression of spontaneous Ca2 release and the activity of RyR2 contributes, at least in part, to the anti-arrhythmic properties of K201.