Vortosiran in Atrial Fibrillation

Inclusion Criteria: 1. Adult male and female participants, age \>/=45 years. 2. Documented diagnosis of non-valvular AF within 12 months of signing the informed consent (paroxysmal, persistent, or permanent) confirmed by ECG evidence (12-lead or other physician-confirmed electronic recording) and currently receiving continuous treatment with a DOAC for stroke prevention for at least the past 3 months. 3. Capable of giving signed informed consent. Written informed consent must be obtained before any trial procedure is initiated. 4. Postmenopausal women are eligible without additional contraceptive measures. Postmenopausal status is defined as: * Age \>/=55 years with \>/=12 months of spontaneous amenorrhea, or * Age \<55 years with \>/=12 months of spontaneous amenorrhea and follicle-stimulating hormone in the postmenopausal range, or surgical menopause (bilateral oophorectomy, with or without hysterectomy) documented in the medical history. 5. Women of childbearing potential must agree to use highly effective contraception for the duration of trial treatment and for the specified post-treatment period. Exclusion Criteria: 1. AF due to a reversible cause (e.g., cardiac surgery, pulmonary embolism, untreated hyperthyroidism, alcohol use), participants in sinus rhythm after successful ablation or planned for cardioversion or ablation during trial conduct. 2. Patients with an intracranial or intraocular bleed within the 3 months prior to screening or any history of spontaneous intracerebral haemorrhage at any time in the absence of antithrombotic treatment. 3. Any stroke within 14 days before randomisation or a transient ischemic attack within 3 days before randomisation. 4. Mechanical heart valve or valve disease that is expected to require mechanical valve replacement intervention (surgical or trans vascular) during the course of the trial. 5. Patients with a medical condition other than non-valvular AF for which chronic anticoagulation is indicated. 6. Known presence of an atrial myxoma or left ventricular thrombus. 7. History of or planned left atrial appendage closure or left atrial appendage removal. 8. Uncontrolled hypertension (systolic blood pressure \>/= 160 mmHg or diastolic blood pressure \>/=100 mmHg) at randomization. 9. Active bleeding, known bleeding disorder, or known anaemia that requires treatment or capillary Hgb \<100 g/L. 10. Any history of non-traumatic intracranial haemorrhage when not under treatment with an anticoagulant. 11. Known significant liver disease (e.g., acute hepatitis, chronic active hepatitis, cirrhosis) or hepatic insufficiency classified as Child-Pugh B or C, or alanine aminotransferase (ALT)/aspartate aminotransferase (AST) \>2.5 x the upper limit of normal, measured between screening and randomisation. 12. Estimated glomerular filtration rate (eGFR) \< 30 mL/min/1.73 m2 from the local lab, determined between screening and randomization. 13. Major surgery during the last 30 days or planned major surgery or intervention with potential for uncontrolled bleeding within the trial period (e.g., carotid endarterectomy, coronary artery bypass grafting). 14. Women who are pregnant, currently breastfeeding, or planning pregnancy during the trial or within the defined post-treatment period are not eligible. 15. Known allergy, intolerance, or hypersensitivity to any of the trial interventions. 16. Any contraindication for the use of an anticoagulant or listed in the local labelling for apixaban. 17. Anticipated need for chronic therapy with nonsteroidal anti-inflammatory drugs (NSAIDs): Patients with chronic NSAID use, defined as systemic NSAID therapy on \>/=3 days per week for at least 4 consecutive weeks prior to screening, are excluded. 18. Treated with a vitamin K antagonist within 3 months prior to screening. 19. Patients with a diagnosis of hepatitis B virus (HBV), hepatitis C virus (HCV) or human immunodeficiency virus (HIV) at screening. 20. Known current alcohol and / or illicit drug abuse that may interfere with the participant's safety and / or compliance at the discretion of the Investigator. 21. Male participants who are not willing to use condoms when sexually active with a woman of childbearing potential who is not using highly effective contraception. 22. Previous (within 30 days or 5 half-lives of the investigational drug, whichever is longer) or concomitant participation in another clinical trial with investigational medicinal product(s) or device(s). Registries and observational studies are allowed. 23. Any other condition or therapy that would make the participant unsuitable for the trial.