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Comparison of REGN7508 versus apixaban and enoxaparin to prevent blood clots in adults after knee replacement surgery

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What is this trial about?

A plain-language summary of the goals, design and what participants do

This study focuses on preventing venous thromboembolism (blood clots in veins) in patients undergoing total knee arthroplasty (knee replacement surgery). The research compares three different medications: a new drug called REGN7508 against two established treatments - apixaban and enoxaparin. REGN7508 is a new type of medicine that works by targeting specific blood clotting factors.

The purpose of the study is to determine how effective REGN7508 is at preventing blood clots after knee replacement surgery when compared to the standard treatments. The medication will be given either through an intravenous injection into a vein or as an injection under the skin. Some patients will receive apixaban tablets to take by mouth, while others will receive enoxaparin as an injection under the skin.

During the study, doctors will monitor patients for signs of blood clots and bleeding. They will also check how well the body tolerates the new medication and whether the body develops any response to it. The study will look for different types of blood clots, including deep venous thrombosis (blood clots in deep veins) and pulmonary embolism (blood clots in the lungs).

The research process

The trial runs in 4 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Initial treatment administration

    Following total knee arthroplasty (knee replacement surgery), you will receive one of three different medications to prevent blood clots:

    Option 1: REGN7508 given through an intravenous (IV) injection

    Option 2: Enoxaparin (Clexane) given as an injection under the skin

    Option 3: Apixaban (Eliquis) taken as tablets by mouth

  2. Step 2

    Monitoring period

    Your health will be monitored for signs of blood clots, including:

    - Blood clots in leg veins (Deep Vein Thrombosis or DVT)

    - Blood clots in lungs (Pulmonary Embolism or PE)

    Medical staff will check for any bleeding events during treatment

    Blood samples will be collected to measure medication levels in your body

  3. Step 3

    Safety assessments

    Regular monitoring of:

    - Any side effects that occur during treatment

    - Development of antibodies against the medication (for patients receiving REGN7508)

    - Overall health status

  4. Step 4

    Study duration

    The study will continue from June 2025 through May 2027

    Individual participation duration will be specified by your healthcare provider

Who can join the trial?

7 criteria

  • You must be scheduled for a primary elective unilateral total knee arthroplasty (a planned first-time knee replacement surgery on one knee)
  • You must be between 18 and 64 years old
  • Both men and women can participate in the study
  • Your body weight must be less than 130 kilograms at the screening visit
  • You must be in good overall health, which will be confirmed through laboratory tests
  • You must not belong to any vulnerable population groups (such as people unable to give informed consent)
  • You must meet other specific health requirements as defined in the study protocol

Who cannot join the trial?

14 criteria

  • Active or significant bleeding in the last 3 months
  • History of blood clotting disorders (conditions that affect how blood forms clots)
  • Severe kidney problems (poor kidney function that requires medical treatment)
  • Severe liver problems (poor liver function that requires medical treatment)
  • History of stroke in the past 6 months
  • Uncontrolled high blood pressure (blood pressure that remains high despite treatment)
  • Active cancer requiring treatment
  • Planned surgery during the study period (other than the scheduled knee surgery)
  • Use of blood-thinning medications that cannot be stopped
  • Known allergic reactions to blood thinning medications
  • Pregnancy or breastfeeding
  • Body weight less than 40 kg (88 pounds)
  • Participation in another clinical trial in the past 30 days
  • Any condition that the doctor believes would make participation unsafe
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Investigated drugs

  • REGN7508

    is an experimental antibody medication given by intravenous (IV) injection. It works by targeting a blood clotting factor called Factor XI to help prevent blood clots from forming after knee replacement surgery.

  • Apixaban

    is a blood-thinning medication taken as a pill. It helps prevent blood clots by blocking one of the proteins involved in blood clotting. It is commonly used to reduce the risk of blood clots after surgery.

  • Enoxaparin

    is a blood-thinning medication given by injection under the skin. It belongs to a group of medications called low molecular weight heparins and works by preventing blood clots from forming or getting larger. It is frequently used to prevent blood clots in patients who have had surgery.

What is already known about the treatment

  • REGN7508

    An investigational monoclonal antibody administered intravenously that targets Factor XI in the blood clotting cascade. This novel medication is currently being studied in Phase 3 clinical trials for the prevention of venous thromboembolism (blood clots) in patients undergoing total knee replacement surgery. It represents a new approach to blood clot prevention by targeting a specific clotting factor, potentially offering an alternative to traditional anticoagulants.

  • Apixaban

    An oral anticoagulant medication that works by directly inhibiting Factor Xa in the blood clotting process. This established medication is commonly used to prevent blood clots and is taken as a tablet, offering a convenient dosing option for patients requiring blood clot prevention. It belongs to the class of direct oral anticoagulants (DOAs) and has been proven effective in preventing venous thromboembolism after knee replacement surgery.

  • Enoxaparin

    A low molecular weight heparin that is administered by subcutaneous injection to prevent blood clots. This well-established anticoagulant works by enhancing the effect of antithrombin III, which helps inhibit blood clotting factors. It has been a standard treatment for preventing blood clots in patients undergoing orthopedic surgery and is typically given once or twice daily during the period of highest risk.

Investigated diseases

  • Venous Thromboembolism (VTE)

    A condition where blood clots form in the veins, most commonly in the legs or pelvis. The clots can break off and travel through the bloodstream, potentially blocking blood vessels in other parts of the body. VTE encompasses both deep vein thrombosis and pulmonary embolism.

  • Deep Vein Thrombosis (DVT)

    A blood clot that develops in a deep vein, usually in the leg or pelvis. The affected area may become swollen, painful, and warm to the touch. DVT can cause long-term problems with blood flow in the affected limb.

  • Pulmonary Embolism (PE)

    A condition that occurs when a blood clot travels to the lungs and blocks a pulmonary artery or one of its branches. It typically develops as a complication of deep vein thrombosis. The condition can cause difficulty breathing, chest pain, and rapid heartbeat.

  • Thromboembolic Disease

    A broad term for conditions characterized by the formation of blood clots that can travel through blood vessels. It includes both arterial and venous blood clot formation. The condition can affect various parts of the body and may develop gradually or suddenly.

Trial detailsLast updated 7 Oct 2026
Age18+ yearsPhasePhase IIITrial ID2025-520478-20-00Protocol codeR7508-DVT-24116Estimated enrolment2 000 patientsSponsorRegeneron Pharmaceuticals Inc.

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