Clinical Phase 2 Trial of AP31969 Versus Placebo for Rhythm Control of Atrial Fibrillation

Inclusion Criteria: * Willing and able to provide written informed consent. * Age 18 or older. * ECG documented diagnosis of paroxysmal or persistent AF. * AF history at screening indicating an expected AF burden of 1-90%, i.e., at least 1 self-terminating AF episode within 4 months prior to the screening visit. * AF burden of ≥ 1% and ≤ 90% assessed with an ECG patch device during the screening period prior to the randomisation visit. * Investigator and participant agreement to avoid non-trial related rhythm control intervention for the duration of the trial, including: * Antiarrhythmic drug class I and/or III (including amiodarone) * Electrical or pharmacological cardioversion * AF ablation procedure * Willing to have a loop recorder implanted. Exclusion Criteria: * Prior AF ablation procedure other than pulmonary vein isolation (PVI) only. * Any of the following events within 4 weeks prior to the screening visit: Myocardial infarction, Unstable angina pectoris, Stroke or transient, ischaemic attack, Percutaneous coronary intervention (PCI), Coronary artery bypass graft (CABG), Peripheral revascularisation procedure. * Cardiac pacing device e.g. pacemaker and cardiac resynchronization therapy device with atrial or ventricular pacing for \> 5% of the time or existing implantable loop recorder. * Heart failure, New York Heart Association class III (3) or IV (4). * Left ventricular ejection fraction \< 40% based on imaging (e.g. echocardiography) performed within 6 months prior to or during the screening visit. * Clinically significant valvular heart disease, including severe aortic stenosis, severe mitral regurgitation and/or severe mitral stenosis, in the opinion of the investigator. * QTc (Fridericia, QTcF) interval \> 450 ms for males and \> 470 ms for females at screening. * eGFR \<60 mL/min /1.73 m² based on creatine and CKD-EPI formula * Use of antiarrhythmic drug class I and/or III within 7 days or, for amiodarone, within 3 months prior to the screening visit.