This clinical trial is focused on studying Atrial Fibrillation, a common heart condition that causes an irregular and often rapid heart rate. The study is comparing two treatments: Milvexian, an oral medication that works by inhibiting a specific protein involved in blood clotting, and Apixaban, a well-known medication used to prevent blood clots. The purpose of the study is to determine if Milvexian is as effective as Apixaban in preventing strokes and other related complications in people with Atrial Fibrillation.

Participants in the study will be randomly assigned to one of two treatment groups: one group will receive Milvexian and a matching placebo that looks like Apixaban, while the other group will receive Apixaban and a matching placebo that looks like Milvexian. This means that all participants take both an active medication and a placebo, allowing the study to be conducted in a double-blind manner, so that neither the participants nor the researchers know which active treatment is being administered.

The study will last for up to 48 weeks. During this period, participants will take their assigned medication orally. Some participants may also receive a solution for infusion, known as Ondexxya, to help manage any potential side effects.

The main goal is to monitor the time it takes for participants to experience a stroke or a non-CNS systemic embolism, which is a type of blood clot that occurs outside the brain and spinal cord. Secondary goals include observing the occurrence of major bleeding and other cardiovascular events. The study aims to provide valuable information on the safety and effectiveness of Milvexian compared to Apixaban, potentially offering a new treatment option for individuals with Atrial Fibrillation.