A Study to Evaluate the Effects of ONO-2506 Intravenous Infusion in Patients With Acute Ischemic Stroke

Inclusion Criteria: * Patient must have a clinical diagnosis of acute cortical ischemic stroke. * Patient must be randomized into the study within six hours after the initial onset of stroke symptoms. * Patient must have a measurable focal neurological deficit for a minimum duration of 60 minutes. * Patient must have a CT or MRI examination compatible with the clinical diagnosis of acute ischemic stroke. * Patient must have had a pre-stroke mRS scale score of 0 or 1. * Other inclusion criteria as specified in the study protocol. Exclusion Criteria: * Patient must not have a body weight of more than 125 kg. * Patient must not have a CT and/or MRI with evidence of a non-ischemic mechanism, subarachnoid hemorrhage, or primary intracerebral and/or intraventricular hemorrhage. * Patient must not have all three of the following findings: 1. reduced level of consciousness (has score of greater than or equal to two on NIHSS Question 1a) 2. forced eye deviation or total gaze paresis (has score of 2 on NIHSS Question 2) and 3. dense hemiplegia (no movement) of upper and lower extremities (i.e., has score of 4 on NIHSS Question 5 regarding motor arm and has score of 4 on NIHSS Question 6 regarding motor leg). * Patient must not have neurological signs and symptoms that are rapidly improving. * Patient must not have a severe coexisting or terminal systemic disease. * Patient must not be pregnant or lactating. * Patient must not have impaired hepatic function; bilirubin greater than 2 mg/dL and or ascites. * Patient must not have impaired renal function; serum creatinine greater than 2 mg/dL. * Patient must not have congestive heart failure. * Patient must not have a baseline ECG showing a PR interval greater than 200 milliseconds, or a corrected QT interval of greater than 480 milliseconds, or a history of ventricular arrhythmias, or a Mobitz Type 1 or greater AV block. * Patient must not have other exclusion criteria as specified in the study protocol.