Study to Assess the Safety, Pharmacokinetics, and Pharmacodynamics of DS-1040b in Subjects With Acute Ischemic Stroke

Inclusion Criteria: * Has a clinical diagnosis of acute ischemic stroke (including lacunar stroke/infarct) supported by computed topography or magnetic resonance imaging to rule out alternative cause for presenting symptoms * Has onset of stroke symptoms within 4.5 to 12 hours before initiation of study drug administration - for subjects with a stroke upon waking, time of symptom onset is the last time the subject was known to be well * Has a NIHSS score of ≥ 2 (for Cohorts 1-5) and ≥ 5 (for Cohort 6) * Has Low dose heparin or low molecular weight heparin at a preventive dose are allowed from 24 hours after treatment start completion and after confirmation of no intracranial bleeding on the 24-hours repeat brain imaging. * Is a Cohort 6 participant who is treated or anticipated to be treated with intra-arterial therapy (IAT) for ischemic stroke at the time of randomization (for enrollment in the IAT subgroup) * Has given written informed consent to participate in the study prior to participating in any study-related procedures - depending on country-specific practice, written informed consent may be acceptable from legally authorized representative * Has given a separate written informed consent for collecting a blood sample for genotyping Exclusion Criteria: * Is a Cohort 1-5 participant who has been treated or is going to be treated with tissue plasminogen activator (tPA) and/or endovascular thrombectomy during current stroke * Is a Cohort 6 participant treated or antici…