Phase 2 Study of Oral K201 for Prevention of AF Recurrence

Inclusion Criteria: * Symptomatic AF (sustained \>3 days and \<6 months) and clinically indicated for cardioversion; * Adequate anticoagulant therapy for cardioversion in accordance with standard practice as recommended by ACC/AHA/ESC guidelines or with local clinical practice; * Hemodynamically stable (90 mmHg \< systolic blood pressure \< 190 mmHg)at screening and on Day 1; Exclusion Criteria: * Known prolonged QT syndrome or QTc interval of \>0.500 sec at screening; familial long QT syndrome; previous Torsade de Pointes; ventricular fibrillation; or sustained ventricular tachycardia (VT); * QRS \>0.130 sec; * Previous episodes of second- or third-degree atrioventricular block; * Unsuccessful DC cardioversion attempt within 3 months; prior ablation for AF; * Persistent bradycardia with ventricular rate below 50 beats/min, sick-sinus syndrome or pacemaker (including CRT, AICD); * Myocardial infarction (MI), cardiac surgery, angioplasty, unstable angina or acute coronary syndrome within 30 days prior to entry into the study; * NYHA Class III or Class IV heart failure (HF) at screening or admission, or hospitalized for HF in previous 6 months; * Known concurrent temporary secondary causes of AF; * Received a Class I or Class III antiarrhythmic agent (including sotalol) within 5 half-lives of randomization or amiodarone or dronedarone within 4 weeks; * Received treatment with other drugs known to prolong the QT interval within 5 half-lives.