The purpose of this study is to try to find the best dose of the new drug BAY 2433334 to give to participants and to look at how well BAY 2433334 works in patients with irregular heartbeat (atrial fibrillation) that can lead to blood clots, stroke and other heart-related complications. In addition researchers want to compare the safety of the study drug to apixaban, a non-vitamin K oral anticoagulant (NOAC) in patients with atrial fibrillation. This study is also done to learn how the drug in this study moves into, through and out of the body. BAY 2433334, works by blocking a step of the blood clotting process in our body and thins the blood and is a so called oral FXIa inhibitor.

Apixaban, works by reducing the production of blood clotting factors in our body and thins the blood and is a so called non-vitamin K oral anticoagulant (NOAC). Thinning the blood can prevent you from blood clots which can cause a stroke.

Inclusion Criteria:

• Participant must be 45 years of age or older at the time of signing the informed consent.

• Participant with AF documented by ECG evidence with

  • CHA2DS2-VASc score ≥ 2 if male or CHA2DS2-VASc score ≥ 3 if female

  • Indication for treatment with an oral anticoagulant in

    • any participant currently not treated with an oral anticoagulant (e.g. treatment naïve) or alternatively,
    • participant on a NOAC in case of at least one bleeding risk feature (history of a prior bleed within the last 12 months requiring medical attention and / or moderate renal dysfunction with eGFR 30-50 ml/min and / or current clinically indicated antiplatelet therapy with Acetylsalicylic acid(ASA) ≤ 100 mg)

• Written informed consent

Exclusion Criteria:

• Mechanical heart valve prosthesis
• Any degree of rheumatic mitral stenosis or moderate-to-severe, non-rheumatic mitral stenosis
• Atrial fibrillation due to a reversible cause, participants in sinus rhythm after successful ablation, or plan for cardioversion or ablation during study conduct
• Requirement for chronic anticoagulation (for a different indication than AF) or antiplatelet therapy (up to 100 mg ASA is allowed). Anticipated need for chronic therapy with Nonsteroidal anti-inflammatory drugs (NSAIDs)
• Treated with a Vitamin K antagonist in the 30 days prior to screening

Availability of this study's data will later be determined according to Bayer's commitment to the EFPIA/PhRMA "Principles for responsible clinical trial data sharing". This pertains to scope, timepoint and process of data access.

As such, Bayer commits to sharing upon request from qualified researchers patient-level clinical trial data, study-level clinical trial data, and protocols from clinical trials in patients for medicines and indications approved in the US and EU as necessary for conducting legitimate research. This applies to data on new medicines and indications that have been approved by the EU and US regulatory agencies on or after January 01, 2014.

Interested researchers can use www.clinicalstudydatarequest.com to request access to anonymized patient-level data and supporting documents from clinical studies to conduct research. Information on the Bayer criteria for listing studies and other relevant information is provided in the Study sponsors section of the portal.