Third dose group not recruited due to slow enrollment.

Males and females aged 18-80 years who present with ACS (unstable angina and non ST-elevation MI) defined as one or more episodes of angina lasting at least 5 minutes in the last 24 hours before admission and greater than 0.05 mV of presumed new ST-segment depression in at least 2 contiguous ECG leads OR, angina and per confirmatory angiogram, has been scheduled for percutaneous coronary angioplasty. The primary objective of this study is to evaluate the safety of Serp-1 injection when administered in 3 daily doses to patients undergoing conventional therapy for Acute Coronary Syndrome (ACS) requiring early intervention.

A total of 72 subjects will be enrolled, separated into 3 dose groups and centrally randomized in a 3:1 ratio of Serp-1 injection to placebo control.Subjects will receive Serp-1 by intravenous (IV) bolus injection daily for 3 days, at dose levels of 5.0, 15, and 50 ug/kg/dose or placebo (0.9% normal saline) added to any prescribed therapy for ACS. Serp-1 will be administered as a single IV bolus injection. The initial IV bolus dose is administered immediately preceding the PCI procedure with subsequent doses administered 24 and 48 hours later.Subjects will be evaluated for adverse events, serum inflammatory markers and restenosis rates at 6 months post-dose.

Inclusion Criteria:

• Established diagnosis of unstable angina or NSTEMI with one or more episodes of angina in the 24 hours before hospital admission
• Scheduled for PCI

Exclusion Criteria:

• CABG within 6 months
• Acute ST elevation, eligible for thrombolysis on initial examination
• Coronary lesions with total thrombotic occlusions
• Current immunosuppressant therapy