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Study on REGN9933 for Preventing Blood Clots in Adults After Knee Replacement Surgery

Fast replyRegistered drugNo placebo
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What is this trial about?

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

This clinical trial is focused on studying the prevention of blood clots, known as venous thromboembolism, which can occur after knee replacement surgery. The study is testing a new treatment called REGN9933, a type of medication known as a monoclonal antibody, which is designed to help prevent these blood clots. The trial will compare the effectiveness of REGN9933 with another medication called enoxaparin sodium, which is commonly used to prevent blood clots. Additionally, a medication named apixaban is also being used in the study.

The purpose of the study is to evaluate how well REGN9933 works in preventing blood clots after knee surgery. Participants in the study will receive either REGN9933, enoxaparin sodium, or a placebo. The study will last for about 12 days, during which the occurrence of blood clots and any side effects will be monitored. The study will also look at the levels of REGN9933 in the blood and any changes in blood clotting times.

Throughout the study, participants will be closely monitored for any major bleeding or other side effects. The study aims to provide valuable information on the safety and effectiveness of REGN9933 in preventing blood clots after knee replacement surgery, potentially offering a new option for patients undergoing this procedure.

The research process

The trial runs in 5 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Joining the study

    Upon joining the study, you will be randomly assigned to receive either the investigational medication REGN9933 or a standard treatment called enoxaparin. This is to compare the effectiveness of the new medication against the standard treatment.

  2. Step 2

    Medication administration

    If you are assigned to the REGN9933 group, you will receive this medication through an injection into a vein. The dosage and frequency will be determined by the study team.

    If you are assigned to the enoxaparin group, you will receive this medication as an injection under the skin. The dosage is 40 mg, administered once daily.

  3. Step 3

    Monitoring and follow-up

    Throughout the study, your health will be closely monitored. This includes regular check-ups and tests to assess your response to the medication and to ensure your safety.

    You will be monitored for any signs of blood clots or bleeding, as well as any other side effects that may occur.

  4. Step 4

    End of treatment

    The primary treatment period lasts for approximately 12 days. During this time, the main focus is on preventing blood clots after your knee surgery.

    After the initial treatment period, there will be additional follow-up visits to monitor your health and gather further information about the medication's effects.

  5. Step 5

    Final follow-up

    The study will continue to monitor your health for up to approximately 75 days from the start of the treatment. This includes checking for any long-term effects of the medication.

    You will be asked to attend follow-up visits and undergo tests to ensure your well-being and to collect data for the study.

Who can join the trial?

5 criteria

  • Must be having a planned surgery for a **single knee replacement**.
  • Must weigh **130 kg or less** at the screening visit.
  • Must be considered in **good health** by the study doctor based on medical history, physical exam, vital signs, and heart tests (called **Electrocardiograms or ECGs**) done at the screening or before the first dose of the study drug.
  • Must be in **good health** based on lab tests done during the screening period.
  • Other specific criteria defined in the study protocol may apply.

Who cannot join the trial?

3 criteria

  • Patients with a history of **thromboembolic disease** cannot participate. This means if you have had blood clots in your veins or arteries, you are not eligible.
  • Patients who are not within the specified age range for the study cannot participate. The study is open to certain age groups only.
  • Patients who are part of a vulnerable population are not eligible. This includes groups that may need special protection or care.
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Investigated drugs

  • REGN9933

    is a new type of medication being studied to see if it can help prevent blood clots in the veins, known as venous thromboembolism, after knee surgery. It works by targeting a specific protein in the blood that is involved in clotting, which may help reduce the risk of these clots forming.

  • Enoxaparin

    is a medication that is commonly used to prevent blood clots. It is often given to patients after surgeries, like knee replacements, to help stop clots from forming in the veins. It works by thinning the blood, making it less likely for clots to develop.

What is already known about the treatment

REGN9933 – REGN9933 is administered as an injection and is currently being studied in clinical trials for its effectiveness in preventing blood clots, specifically after knee replacement surgery. It is a monoclonal antibody that targets Factor XI, a protein involved in blood clotting, to reduce the risk of venous thromboembolism, which is a condition where blood clots form in the veins. This medication is still under investigation, and its use is not yet widely established in medical practice. It belongs to the pharmacological class of anticoagulants, which are drugs that help prevent blood clots.

Investigated diseases

Venous Thromboembolism – Venous thromboembolism (VTE) is a condition where blood clots form in the veins. It typically begins with deep vein thrombosis (DVT), where clots develop in deep veins, often in the legs. If a part of the clot breaks off, it can travel to the lungs, causing a pulmonary embolism (PE). This progression can lead to symptoms such as swelling, pain, and redness in the affected limb, and shortness of breath or chest pain if PE occurs. The condition can develop after surgery, prolonged immobility, or due to certain medical conditions that affect blood clotting. VTE can recur and may require ongoing monitoring to prevent further clot formation.
Trial detailsLast updated 2 Oct 2026
Age18+ yearsPhasePhase IITrial ID2022-501470-18-00Protocol codeR9933-DVT-2230Estimated enrolment432 patientsSponsorRegeneron Pharmaceuticals Inc.

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