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REGN7508 Versus Acetylsalicylic Acid (ASA) for Venous Thromboprophylaxis After Total Knee Arthroplasty in Adult Participants
A Phase 3, Multicenter, Double-Blinded, Randomized Study to Evaluate REGN7508, a Factor XI Monoclonal Antibody, Versus Acetylsalicylic Acid for Prophylaxis of Symptomatic Venous Thromboembolism After Elective Total Knee Arthroplasty (ROXI-ASPEN)
Who can join
Ages 18 and older · All sexes
Full eligibility criteria
Key Inclusion Criteria: 1. Is undergoing a primary elective unilateral TKA 2. Is in good health based on laboratory safety testing as described in the protocol Key Exclusion Criteria: 1. Any condition that, as assessed by the investigator, may confound the results of the study or pose an additional risk to the participant by study participation 2. History of bleeding in the 6 months prior to randomization 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 (eg, hemophilia A or B, von Willebrand's Factor deficiency) 3. History of thromboembolic disease or thrombophilia 4. History of platelet dysfunction 5. Has received or plans to receive preoperative enoxaparin on the day prior to TKA surgery Note: Other protocol-defined Inclusion/ Exclusion criteria apply
About the study
This study is researching an experimental drug called REGN7508 (called "study drug") and how it compares against another treatment called Acetylsalicylic Acid (ASA). The study is focused on adults undergoing elective, unilateral (one side) total knee replacement 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 total knee replacement surgery compared to acetylsalicylic acid.
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 study drug less effective or could lead to side effects)
What is being tested
- REGN7508 (drug)
- Acetylsalicylic Acid (ASA) (drug)
- Placebo (drug)
Sponsor: Regeneron Pharmaceuticals · Participants: 2,000 · Started: Nov 24, 2025
Contact the study team
- Clinical Trials Administrator · Phone: 844-734-6643
Official record on ClinicalTrials.gov — NCT07213778
Locations in the U.S.
Conditions
From ClinicalTrials.gov, data retrieved Sep 30, 2026. Each study sets its own eligibility; the study team decides who can join.