REGN9933 + aspirin

**REGN9933 + aspirin** is an investigational combination of a monoclonal antibody (REGN9933) and aspirin intended to prevent and treat conditions related to blood clots, with a focus on balancing efficacy and bleeding risk. REGN9933 is a human monoclonal antibody that targets and inhibits Factor XI, a protein involved in the intrinsic pathway of coagulation, aiming to reduce thrombotic events while minimizing bleeding compared to traditional anticoagulants. Aspirin acts as an antiplatelet agent by irreversibly inhibiting cyclooxygenase-1 (COX-1), thereby reducing platelet aggregation. REGN9933 is being developed primarily for the prevention of venous thromboembolism, including after elective orthopedic surgery and in other high-risk settings. The combination is being studied to assess its impact on gastrointestinal and overall bleeding risk relative to other anticoagulant regimens.