This study tests the drug, Plasmin (Human), in patients with a stroke due to a clot in the middle cerebral artery (MCA). Plasmin is an enzyme that causes clot lysis by cleaving a clot component, fibrin. In this study, Plasmin (Human) is administered locally through a catheter to the clot within 9 hours of the stroke onset. Three doses of Plasmin (Human) (20 mg, 40 mg, and 80 mg) are being tested in 3 different groups of patients. Patients are monitored by imaging of the affected artery and functional testing.

This is a Phase 1/2a, open-label, multi-center, sequential dose escalation, safety study of Plasmin (Human) in acute ischemic stroke caused by middle cerebral artery occlusion documented by arteriography. Plasmin (Human) will be administered through a catheter into the thrombus within 9 hours of stroke onset. Approximately sixty-one (61) patients will be enrolled and will receive Plasmin (Human). The objectives of this study are to determine the safety of escalating doses of Plasmin (Human) and to determine the proportion of patients with treatment success, defined as partial or full recanalization.

Inclusion Criteria:

1. 18 to 85 years of age
2. Male or female
3. New focal, potentially disabling neurologic deficit clinically localized to the MCA distribution
4. Intra-arterial therapy with Plasmin completed within 9 hours of stroke onset
5. A National Institutes of Health Stroke Scale score ≥ 4 and ≤ 25

Exclusion Criteria:

1. Intracranial procedures or intracranial or systemic bleeding within the last year
2. Intracranial neoplasm (except meningioma), septic embolism, or unsecured aneurysm
3. Active bleeding
4. History of stroke in previous 6 weeks
5. Uncontrolled hypertension
6. Renal disease or renal dialysis
7. Treatment with any plasminogen activator within the last 48 hrs.
8. Therapy with a Glycoprotein IIb/IIIa inhibitor in 5 days prior to study enrollment or at any time during study