This study is researching an experimental drug called REGN7508 (called "study drug"). The study is focused on adults undergoing elective, unilateral (one side) total knee replacement (TKR) surgery.

The aim of the study is to see how effective the study drug is at preventing venous thromboembolism (VTE) and other related diseases after unilateral total knee replacement surgery.

The study is looking at several other research questions, including:

• What side effects may happen from taking the study drug
• How much study drug is in the blood at different times
• Whether the body makes antibodies against the study drug (which could make the drug less effective or could lead to side effects)

Key Inclusion Criteria:

1. Undergoing a primary elective unilateral TKA
2. Has a body weight ≤130 kg at screening visit
3. Is judged by the investigator to be in good health based on medical history, physical examination, vital sign measurements, and electrocardiograms (ECG's) performed at screening and/or prior to administration of initial dose of study drug as described in the protocol
4. Is in good health based on laboratory safety testing obtained during the screening period as described in the protocol

Key Exclusion Criteria:

1. History of bleeding in the past 6 months prior to dosing requiring hospitalization or transfusion; history of intracranial or intraocular bleeding, excessive operative or post-operative bleeding, and traumatic spinal or epidural anesthesia; history of bleeding diathesis
2. History of thromboembolic disease or thrombophilia
3. History of major surgery, including brain, spinal, or ocular, within approximately the past 6 months
4. History of major trauma within approximately the past 6 months prior to dosing
5. Hospitalized (>24 hours) for any reason within 30 days of the screening visit
6. Has an estimated glomerular filtration rate (GFR) of <45 mL/min/1.73m^2 at the screening visit using one of the following formulas: the Modification of Diet in Renal Disease (MDRD) equation, the Chronic Kidney Disease Epidemiology Collaboration equation, or equivalent equation

Note: Other protocol-defined Inclusion/ Exclusion Criteria apply

All Individual Patient Data (IPD) that underlie publicly available results will be considered for sharing.

When Regeneron has:

• received marketing authorization from major health authorities (e.g., FDA, European Medicines Agency (EMA), Pharmaceuticals and Medical Devices Agency (PMDA), etc.) for the product and indication, or has globally discontinued development of the product for all indications on or after April 2020 and has no plans for future development
• made results publicly available (e.g., scientific publication, scientific conference, clinical trial registry),
• the legal authority to share the data, and
• ensured the ability to protect participant privacy.

Qualified researchers can submit a proposal for access to individual patient or aggregate level data from a Regeneron-sponsored clinical trial through Vivli. Regeneron's Independent Research Request Evaluation Criteria can be found at: https://www.regeneron.com/sites/default/files/Regeneron-External-Data-Sharing-Policy-and-Independent-Research-Request-Evaluation-Criteria.pdf