Safety and Efficacy Evaluation of Intracoronary Infusion of Allogeneic Human Cardiac Stem Cells in Patients With AMI

Inclusion Criteria: * Adult patients ≥ 18 years of age and ≤ 80 years. * Patients presenting a ST-segment-elevation myocardial infarction (STEMI) according to the universally accepted definition found in the STEMI management guide of the European Society of Cardiology * Killip ≤ 2 on admission * Successful primary coronary revascularization by Percutaneous Coronary Intervention- PCI - (Thrombolysis In Myocardial Infarction \[TIMI\] = 3) within 12h after the onset of infarct symptoms * Bare-metal or drug-eluting stents (DES) of second generation (including new second generation stents, e.g. biolimus, novolimus and bioreabsorbable stents) at coronary revascularization by PCI * Ejection Fraction (EF) ≤45% by magnetic resonance imaging (MRI). This MRI will be done between day 3 and day 5 after infarction and will be used as inclusion MRI * Infarct size in left ventricle (LV) tested in the screening MRI ≥25% The presence of microvascular obstruction at inclusion MRI is permitted * The affected coronary artery is adequate for cells infusion at the administration time. The administration procedure is technically feasible on day 4-7 after coronary revascularization by PCI * The patient is stable and in adequate clinical condition to undergo the procedure. Exclusion Criteria: * Participation in another clinical trial in the last 30 days * Previous allogeneic transplant (blood transfusions are allowed) or treated with cell or gene therapy * Previous Q-wave infarction * Significant valve disease, relapsing pericarditis, history of cardiac tamponade, cardiomyopathies * Severe stenotic lesions (\>90%) in a coronary vessel with size \>2.75 mm not treated by PCI at least 24 hours before the baseline MRI study * Previous EF≤45%, NYHA \> 2 (New York Heart Association Functional Classification) or hospital admission for heart failure before STEMI * Sustained VT that does not revert with treatment or requires \>6 hours to be controlled in the 48 hours prior to the product administration procedure * Complete atrioventricular blockade, or acute left bundle branch block in the 48 hours prior to the product administration procedure * History of cardioembolic disease * Platelets \<100,000 and/or Hb\<8.5g/dL * Acute or chronic renal failure with creatinine ≥2.5 mg/dl or creatinine clearance ≤30 mL/min * Infection with systemic involvement * Cancer disease, except that eradicated at least 5 years before inclusion, and without receiving radiotherapy on chest. It is permitted coetaneous non-melanoma neoplasms completely eliminated (at any time) and that do not require subsequent chemotherapy or radiotherapy on chest. * Child-Pugh's C stage chronic liver disease * Baseline respiratory failure requiring oxygen at home * Uncontrolled hypertension at screening despite treatment (systolic blood pressure \[BP\] ≥180 and/or diastolic BP ≥110) * Very poorly controlled diabetes (Hb1Ac ≥8.5 g/dL) or with serious target organ lesion (peripheral vascular disease requiring revascularization or non revascularize) * History of autoimmune disease * Primary or acquired immune deficiency or immunosuppressant treatment (including treatments with immunosuppressants in the previous three months, or foreseeable need for those treatments during the course of the study). * Women who are pregnant or breastfeeding or women of childbearing potential who do not agree to use contraceptives during the study period * Life expectancy of less than 2 years for any reason. * Allergy to aminoglycoside antibiotics or HSA hypersensitivity * Contraindications preventing the use of Magnetic Resonance Imaging: Pacemaker, Implantable cardioverter-defibrillator (ICD), known reaction to gadolinium, claustrophobia, cochlear implants