Intraarterial Alteplase Versus Placebo After Mechanical Thrombectomy

INCLUSION CRITERIA: 1. Patients with symptomatic large vessel occlusion (LVO) in the anterior, middle or posterior cerebral artery treated with MT resulting in an mTICI score 2b/3 at end of the procedure.. Patients with an mTICI score 2b/3 on the diagnostic cerebral angiography before the onset of MT are also eligible for the study. 2. Estimated delay to onset of rescue intraarterial rt-PA administration \<24 hours from symptom onset, defined as the point in time the patient was last seen well 3. No significant pre-stroke functional disability (modified Rankin scale 0-1), or mRS \>1 that according to the investigator is not related to neurological disease (i.e. amputation, blindness) 4. Age ≥18 5. ASPECTS \>6 on non-contrast CT (NCCT) scan or MRI if symptoms lasting \<4.5 hours or ASPECTS \>6 on CT-Perfusion (CTP) or DWI-MRI if symptoms \>4.5 \<24 hours. 6. Informed consent obtained from patient or acceptable patient surrogate EXCLUSION CRITERIA: 1. NIHSS score on admission \>25 2. Contraindication to IV t-PA as per local national guidelines (except time to therapy) 3. Use of carotid artery stents during the endovascular procedure requiring dual antiplatelet therapy during the first 24h 4. Female who is pregnant or lactating or has a positive pregnancy test at time of admission 5. Current participation in another investigation drug or device treatment study (except observational study i.e.: RACECAT or clinical trials not testing new medical devices or new drugs i.e.IMAGECAT) 6. Known hereditary or acquired hemorrhagic diathesis, coagulation factor deficiency 7. Known coagulopathy, INR \> 1.7 or use of novel anticoagulants \< 48h from symptom onset 8. Platelets \< 50,000 9. Renal Failure as defined by a serum creatinine \> 3.0 mg/dl (or 265.2 μmol/l) or glomerular Filtration Rate \[GFR\] \< 30 10. Subject who requires hemodialysis or peritoneal dialysis, or who have a contraindication to an angiogram for whatever reason 11. Any hemorrhage on CT/MRI 12. Clinical presentation suggests a subarachnoid hemorrhage, even if initial CT or MRI scan is normal 13. Suspicion of aortic dissection 14. Subject currently uses or has a recent history of illicit drug(s) or abuses alcohol 15. History of life threatening allergy (more than rash) to contrast medium 16. SBP \>185 mmHg or DBP \>110 mmHg refractory to treatment 17. Serious, advanced, terminal illness with anticipated life expectancy \< 6 months 18. Pre-existing neurological or psychiatric disease that would confound evaluation 19. Presumed vasculitis or septic embolization 20. Unlikely to be available for 90-day follow-up (e.g. no fixed home address, visitor from overseas)