Patients aged between 18 and 85 with anterior circulation AIS who are eligible for alteplase and mechanical thrombectomy commenced within 6 hours of stroke onset will be enrolled if they present with an infarct core volume between 15-100 mL with at least 20% mismatch (as evaluated by CTP) and intracranial occlusion in proximal cerebral arteries. Exclusion criteria are (1) standard contraindications to alteplase or mechanical thrombectomy; (2) evidence of other diseases of the CNS; (3) pre-existing neurologic disability (a score greater than 2 on the mRS); (4) swallowing difficulties that would prevent administration of oral fingolimod; (5) patients with any history of bradyarrhythmia, atrioventricular block or current use of beta-blockers or verapamil; (6) concomitant use of antineoplastic, immunosuppressive or immune modulating therapies; (7) macular edema.