REGN7508 vs Apixaban for Atrial Fibrillation

Key Inclusion Criteria: 1. Has AF or flutter (paroxysmal or persistent), not considered to be secondary to a reversible cause, and an indication for indefinite anticoagulation treatment as described in the protocol 2. Meets one of the following: 1. CHA2DS2-VA \[C: Congestive heart failure; H: Hypertension; A2: Age ≥75 years (double points); D: Diabetes mellitus; S2: Stroke or TIA or Systemic embolism (double points); V: Vascular disease; A: Age 65-74 years\] score ≥2 and Oral Anticoagulant (OAC) naïve OR 2. CHA2DS2-VA score ≥3 OR 3. CHA2DS2-VA score of 2 AND at least 1 enrichment criteria as described in the protocol 3. Must have an International Normalized Ratio (INR) \<2.5 at the time of randomization if taking warfarin or another Vitamin K Antagonist (VKA) Key Exclusion Criteria: 1. Has a mechanical heart valve prosthesis (Note: transcatheter aortic valve replacement is not an exclusion) 2. Has known moderate-to-severe mitral stenosis 3. Has had a successful ablation therapy without documented recurrent AF or a participant after Left Atrial Appendage (LAA) occlusion/exclusion or plan for ablation or LAA occlusion/exclusion within the next 6 months starting from randomization 4. Had an ischemic stroke within 2 days prior to randomization 5. Has persistent, uncontrolled hypertension (per investigator's discretion) 6. Has estimated Glomerular Filtration Rate (eGFR) \<15 mL/min/1.73m2 within 30 days prior to randomization or is on dialysis or expected to be started on dialysis within the next 6 months starting from randomization Note: Other protocol-defined Inclusion/ Exclusion criteria apply