The purpose of this study is to evaluate desmoteplase (which is a manufactured protein derived from the saliva of the vampire bat) in dissolving clots that are blocking the flow of blood through one (or more) of the blood vessels supplying the brain, thereby reopening the blocked blood vessel and allowing blood to flow again in individuals suffering from ischemic stroke.

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.