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REGN7508 versus aspirin to prevent blood clots after single-knee replacement

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)

Phase 3 Interventional Regeneron Pharmaceuticals · NCT07213778

This tests whether REGN7508 or aspirin better prevents blood clots in adults having elective single-knee replacement surgery.

Quick facts

PhasePhase 3
Study typeInterventional
Enrollment2000 (estimated)
Ages18 Years and up
SexAll
SponsorRegeneron Pharmaceuticals Industry-sponsored
Locations16 sites (Rancho Mirage, California and 15 other locations)
Trial IDNCT07213778 on ClinicalTrials.gov

What this trial studies

This Phase 3 interventional trial compares REGN7508, acetylsalicylic acid (aspirin), and placebo for prevention of venous thromboembolism after elective unilateral total knee arthroplasty in adults. Participants judged medically fit will receive one of the study drugs and be followed for VTE events, safety, drug blood levels, and formation of anti-drug antibodies. Key exclusions include recent major bleeding, prior thromboembolic disease or thrombophilia, platelet dysfunction, and receipt of preoperative enoxaparin. The trial is sponsored by Regeneron Pharmaceuticals and is being conducted at several U.S. clinical sites.

Who should consider this trial

Good fit: Adults scheduled for a primary elective unilateral total knee arthroplasty who are in good health by protocol laboratory tests and who meet the inclusion/exclusion criteria are ideal candidates.

Not a fit: Patients with recent significant bleeding, known thromboembolic disease or thrombophilia, platelet disorders, or those receiving preoperative enoxaparin are unlikely to benefit and are excluded.

Why it matters

Potential benefit: If successful, REGN7508 could offer an alternative to aspirin that reduces post-operative blood clots with a different safety or dosing profile.

How similar studies have performed: Aspirin and other anticoagulants are established for VTE prevention after TKA, while monoclonal antibody approaches like REGN7508 are newer and have limited large-scale Phase 3 experience to date.

Eligibility criteria

Show full inclusion / exclusion 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

Where this trial is running

Rancho Mirage, California and 15 other locations

Study contacts

How to participate

  1. Review the eligibility criteria above with your treating physician.
  2. Visit the official trial page on ClinicalTrials.gov for the most current contact information and recruitment status.
  3. Contact the listed study coordinator or principal investigator to request pre-screening. Pre-screening is free and never obligates you to enroll.
View on ClinicalTrials.gov → Find more trials like this →
Conditions Symptomatic Venous ThromboembolismTotal Knee ArthroplastyElective Unilateral TKADeep Vein ThrombosisPulmonary Embolism
Last reviewed 2026-06-13 by the Find a Trial editorial team. Information on this page is for educational purposes and is not medical advice. Always consult qualified healthcare professionals about clinical trial participation.