Phase I Interaction Study of Istaroxime and Digoxin in Subjects With Stable Heart Failure

Inclusion Criteria: Main screening inclusion criteria : * Signed informed consent; * Male or female patients ≥18 years; * Female patients of childbearing potential must not be pregnant; * Chronic stable cardiac function impairment (no change in heart failure medication over the last 3 months and without any dosage adjustment in the last 4 weeks); * Systolic blood pressure (SBP) of ≥ 90 mmHg and ≤ 140 mmHg; * LVEF ≤ 35% by any method (to be performed at screening if not measured within the last 12 months); * Chronic treatment (i.e. once daily dosing without interruption) with oral digoxin started at least 3 months prior to study entry and without any concomitant administration of other positive inotropic drugs; Exclusion Criteria: Main screening exclusion criteria : * Need for current or intermittent intravenous positive inotrope administration within the preceding 6 months, or hemodynamic support devices; * Acute coronary syndrome within the past 3 months; * Coronary artery bypass graft or percutaneous coronary intervention within the past 3 months; * Stroke within the past 6 months; * Atrial fibrillation or uncontrolled heart rate (HR) (\> 100 beats per minute \[bpm\]); * Significant arrhythmia or second or third degree atrio-ventricular block; * Valvular disease as the primary cause of HF; * Significant ECG abnormalities as assessed by appropriately qualified physician or investigator including QTcF \>450; * Positive testing for Human Immunodeficiency Virus (HIV), Hepatitis B and/or Hepatitis C; Main randomization exclusion criteria: * HR \> 100 bpm or \< 50 bpm; * Serum potassium \> 5.3 mmol/L or \< 3.8 mmol/L and magnesium \> 1.1 mmol/L or \< 0.6 mmol/L, * TN I \> ULN.