Following initial physical examination, vital signs, establishment of a separate and dedicated IV access, baseline blood sampling, and confirmation of all study eligibility requirements, patients will be randomized and begin receiving study drug as an adjunct to standard therapy. Patients will begin study drug infusion as soon as possible, but < 6 hours following onset of AMI symptoms (i.e., symptoms of myocardial ischemia). Examples of ischemic symptoms include chest, arm, and/or jaw pain, shortness of breath, nausea, diaphoresis, or other symptoms that the investigator considers to be of ischemic origin. A negative result from a urine pregnancy test must be obtained for females of childbearing potential prior to the start of study drug infusion.