Eligibility Criteria

Inclusion Criteria

- Eligible for study treatment within 3-9 hours after onset of stroke symptoms.
- Score of 4-24 on the NIHSS with clinical signs of hemispheric infarction (i.e. hemiparesis) suggestive of ischemic stroke.
Inclusion Criteria from diagnostic imaging screening:
- Distinct penumbra (at least 20%), measured by MRI (PWI/DWI) or perfusion CT, related to middle cerebral artery (MCA), anterior cerebral artery (ACA), or posterior cerebral artery (PCA) territory in a hemispheric distribution.

Exclusion Criteria

- History or clinical presentation of intracranial hemorrhage (ICH), subarachnoid hemorrhage, arteriovenous malformation, aneurysm, or cerebral neoplasm.
- Rapidly improving neurological symptoms.
- Pre-stroke MRS score of > 1 (including previous disability).
- Suspected acute vertebral or basilar artery occlusion.
- Current use of anticoagulants and a prolonged prothrombin time.
- Uncontrolled hypertension.
- Baseline hematocrit of < 0.25.
- Baseline platelet count < 100,000/mm3.