The purpose of the study is to evaluate whether FX06 is capable of limiting infarct size following balloon catheterization for acute myocardial infarction.

Inclusion Criteria:

• Patients who have given informed consent
• Patients after primary percutaneous coronary intervention (PCI) for acute ST-elevation myocardial infarction (STEMI)
• Men or women with no child bearing potential
• Onset of symptoms to balloon time < 6 hours
• ST-elevation of at least 2 mm in at least 3 leads on 12-lead electrocardiogram (ECG)
• Primary PCI indicated per standard of care
• First myocardial infarction (MI)
• Single index lesion with complete occlusion [thrombolysis in myocardial infarction (TIMI) flow 0/I] of one target vessel.

Exclusion Criteria:

• History of MI (from patient history, or from ECG)
• Chest pain or other angina symptoms in the 24 hours before the first recognized symptoms of the acute myocardial infarction (AMI)
• Need for coronary artery bypass graft (CABG)
• Administration of any thrombolytic agent since onset of AMI symptoms
• Serious procedural complications (e.g., procedural unintended occlusion of coronary artery branch, cardiac tamponade, emergency bypass operation, LM dissection, etc.)
• Presence of cardiogenic shock: hemodynamically unstable and/or need for positive inotropic agents
• Contraindication to cardiovascular magnetic resonance (CMR): claustrophobia, pacemakers, defibrillators and other electronic devices, and metallic cerebral clips; frequent extrasystoles (> 12/Min) or atrial fibrillation (AF).
• Known renal dysfunction defined as serum creatinine > 250 µmol/l
• Previous CABG
• History of congestive heart failure (CHF)
• Body mass index (BMI) > 35
• Patients who cannot communicate reliably with the investigator
• Patients who are unlikely to cooperate with the requirements of the study
• Patients who are unwilling and/or unable to give informed consent
• Patients at increased risk of death from a pre-existing concurrent illness
• Patients participating in another clinical study
• Patients who have used any other investigational drugs within 1 month of first dosing
• Patients who have participated already in this study
• Patients who are employees at the investigational site; relatives or spouse of the investigator.