1. The participant or legally authorized representative has provided informed consent or deferred consent eligibility confirmed before the initiation of any trial procedures.
Age:
2. greater than and equal to (\>=) 18 years of age, inclusive, at the time of signing the Informed Consent Form (ICF) or confirmation of deferred consent eligibility.
Clinical Characteristics:
3. Clinical diagnosis of AIS.
4. Onset of stroke symptoms within 24 hours of randomization. Wake-up strokes may be included if Last Known Well is within 24 hours of randomization; time of onset will be considered the time of Last Known Well.
5. National Institutes of Health Stroke Scale score of 5 to 25, indicating moderate to severe stroke. Participants with an NIHSS score of 5 are eligible only if at least 1 predefined disabling neurological deficit is present, as defined by one or more of the following
NIHSS criteria:
* Complete hemianopia (NIHSS visual score \>=2).
* Aphasia impairing meaningful communication (NIHSS language score \>=2).
* Motor deficit with inability to sustain effort against gravity (NIHSS left or right motor arm or leg score \>=2).
6. Estimated Modified Rankin Scale score less than (\<) 2 prior to AIS presentation, signifying no significant disability.
7. Persistent neurological signs and symptoms consistent with unilateral supratentorial circulation stroke.
9. Evidence of salvageable brain tissue on CT or MR imaging.
You may not be if
Medical History:
1. Weight \>130 kilograms (kg) or \<40 kg.
2. History of severe traumatic brain injury in the past 90 days.
3. History of intracranial hemorrhage.
4. History of intracranial neoplasm except for small meningioma.
5. History of prior stroke in the past 90 days.
6. History of intracranial or intraspinal surgery within the past 90 days.
7. Major surgery or severe trauma in the past 14 days.
8. History of cerebral amyloid angiopathy.
9. Recent history of active systemic malignancy within the last 5 years, except for locally excised basal cell or squamous cell skin carcinoma with clear margins.
10. Diagnosis of serious, advanced, or terminal illness with anticipated life expectancy of less than 1 year.
11. Participation in other interventional clinical trials within the previous 90 days.
12. Known life-threatening hypersensitivity reaction to TAK-755 or its components.
13. Any prior administration of TAK-755.
14. Administration of caplacizumab in the past 30 days.
15. Administration of von Willebrand factor-containing products in the past 14 days.
16. Baseline conditions (prior to the index AIS event) that prevent an understanding of the nature, scope, and possible consequences of the trial, in the judgment of the investigator.
Current Stroke Management:
17. Any prior administration (intravenous or intra-arterial) of alteplase or tenecteplase for the index AIS event, as well as any prior administration of prourokinase or reteplase for the index AIS event in countries where approved.
18. Eligible for administration of intravenous thrombolysis (alteplase or tenecteplase, as well as prourokinase or reteplase in countries where approved) for the index AIS event, based on the site's standard clinical guidelines and direct availability.
19. Intent to proceed with endovascular thrombectomy (EVT) for the index AIS event based on eligibility and direct availability.
20. Seizure at time of index AIS event onset, only if it precludes accurate assessment of baseline NIHSS.
21. Persistent blood pressure elevation (systolic \>=185 millimeters of mercury \[mmHg\] or diastolic \>=110 mm Hg) prior to randomization.
22. Blood glucose \<50 milligrams per deciliter (mg/dL) or \>400 mg/dL.
Current Medical Conditions:
23. Active, uncontrolled bleeding.
24. Bleeding diathesis or any other conditions that would pose significant bleeding risk.
25. Inability to undergo MRI or CT.
26. Chronic causative intracranial occlusion.
27. Causative total occlusion of the extracranial ICA.
28. Evidence of septic emboli or bacterial endocarditis.
29. Another clinically significant concomitant disease that may pose additional risks for the participant in the opinion of the investigator.
30. Pregnancy, lactation, or unable to comply with birth control methods or abstinence as specified in the protocol in the opinion of the investigator.
Imaging:
31. Poor quality imaging that precludes interpretation according to trial protocol.
32. Evidence of significant intracranial mass effect or midline shift.
33. Evidence of acute occlusion in \>1 vascular territory (right/left MCA, right/left ACA, right/left PCA); multiple occlusions within the same vascular territory are allowed.
34. Evidence of acute or chronic intracranial hemorrhage (presence of chronic cerebral microbleeds on magnetic resonance imaging \[MRI\]) T2\*-weighted type sequence (such as gradient recalled echo \[GRE\] or susceptibility weighted imaging \[SWI\]) is not exclusionary if total \<10 and not consistent with diagnosis of cerebral amyloid angiopathy).
35. Evidence of extensive early ischemic change estimated to be greater than one-third of the middle cerebral artery territory or evidence of well-demarcated hypoattenuation on computed tomography (CT), if performed, consistent with established infarction and judged by the investigator to correspond to the clinical symptoms of the index AIS.
36. Evidence of intracranial tumor (except incidental, small meningioma), cerebral aneurysm, or arteriovenous malformation.
