Combination Antithrombotic Treatment for Prevention of Recurrent Ischemic Stroke in IntraCranial Atherosclerotic diseaSe (CATIS- ICAS)

Inclusion Criteria: 1. Age \> 40 years 2. Ischemic stroke or high-risk TIA (motor and/ or speech involvement) 3. Randomization within 30 days of index stroke 4. Stroke potentially attributable to ICAS 30-99% (or flow gap on time-offlight MRA) of a major intracranial artery (internal carotid artery, middle cerebral artery, anterior cerebral artery, posterior cerebral artery, intracranial vertebral artery, or basilar artery) by MRA or CTA or catheter angiography. 5. Modified Rankin Scale Score \< 4 at randomization 6. Ability to obtain informed consent prior to randomization. Exclusion Criteria: 1. Cardioembolic stroke 2. Indication for long-term dual antiplatelet or anticoagulant therapy (e.g. venous thromboembolism, coronary stent, mechanical prosthetic valve) 3. Intracranial arterial stenosis secondary to causes other than atherosclerosis e.g. dissection, moya moya disease 4. Substantial extracranial carotid artery disease ipsilateral to the qualifying stroke with plans for carotid revascularization 5. Intended intracranial stenting for the qualifying stroke 6. Symptomatic hemorrhagic transformation of the index stroke, or neuroradiological class 2 (PH2 type) or symptomatic class 3 on Heidelberg scale prior to randomization 7. Previous non-traumatic intracerebral hemorrhage, non-aneurysmal subarachnoid hemorrhage (treated aneurysmal subarachnoid hemorrhage will be allowed) 8. Subdural hematoma within 12 months prior to randomization or traumatic brain hemorrhage within 1 month prior to randomization 9. Advanced kidney disease at randomization (eGFR \<15 ml per minute) 10. Platelet count less than 100,000/mm3 at enrolment or other bleeding diatheses 11. Uncontrolled hypertension with BP consistently above 180 mmHg for systolic and 110mmHg for diastolic while on treatment 12. Known hypersensitivity or contraindication to ASA, clopidogrel or rivaroxaban 13. Concomitant use of strong inhibitors of both cytochrome P450 isoenzyme 3A4 (CYP3A4) or P- glycoprotein (P-gp) 14. Females of childbearing potential who are not surgically sterile, pregnant, or breast-feeding 15. Previous randomization to this study 16. Participating in a study with an investigational drug or medical device that would interfere with the study at the time of randomization (participants that are no longer in an active arm of a study but are being followed may be randomized) 17. Terminal medical illness with life expectancy less than 1 year