As standard care, all patients will receive standard dose intravenous alteplase (0.9 mg per kilogram, the first 10% administered as an initial bolus and the remainder over a 1-hour period, with a maximum dose of 90 mg) and mechanical thrombectomy delivered at the site of intracranial vessel occlusion. Patients randomized to fingolimod will also receive oral fingolimod (Gilenya, Novartis) at a dosage of 0.5 mg once daily, for three consecutive days, with the first dose being given at the time in which patients are enrolled which is about one hour prior to mechanical thrombectomy.