A Phase 2, Randomized, Multicenter, Open-Label, Blinded-Endpoint Study to Evaluate the Safety of Regn7508 and Regn9933, Monoclonal Antibodies Against Fxi, Versus Apixaban in Participants With Atrial Fibrillation (Roxi-Atlas)

Studying Safety of Heart Treatment

T
Tanyanan Tanawuttiwat

Primary Investigator

Enrolling By Invitation
18 years - 100 years
All
Phase 2
12 participants needed
1 Location

Brief description of study

This study is researching experimental drugs called REGN7508 and REGN9933. The study is focused on participants who have atrial fibrillation, which means that the heart beats too fast and unevenly. REGN7508 and REGN9933 are designed to help stop blood clots forming in patients with atrial fibrillation.

THIS STUDY IS ENROLLING BY INVITATION ONLY 

Detailed description of study

The aim of the study is to see how well REGN7508 and REGN9933 work in patients that get medicine for their atrial fibrillation. The bleeding effects of REGN7508 and REGN9933 will be compared to another medicine (apixaban), which is available on the market to treat and prevent formation of blood clots.

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

  • What side effects may happen from taking REGN7508 or REGN9933
  • How well do the study drugs reduce the risk of having a stroke
  • How much of REGN7508 or REGN9933 is in the blood at different times
  • Whether the body makes antibodies against REGN7508 or REGN9933 (which could make the drugs less effective or could lead to side effects)

Eligibility of study

You may be eligible for this study if you meet the following criteria:

  • Conditions: Atrial Fibrillation (AF)
  • Age: 18 years - 100 years
  • Gender: All

Key Inclusion Criteria:

  1. Has AF or flutter (paroxysmal or persistent), not felt to be secondary to a reversible cause, and an indication for indefinite anticoagulation treatment as described in the protocol
  2. Meets one of the following:
    1. CHA2DS2-VA [C: Congestive heart failure; H: Hypertension; A2: Age ≥75 years (double points); D: Diabetes mellitus; S2: Stroke or TIA or Thromboembolism (double points); V: Vascular disease; A: Age 65-74 years] score ≥2 and Oral Anticoagulant (OAC) naïve or
    2. CHA2DS2-VA score ≥3 or
    3. CHA2DS2-VA score of 2 and at least 1 enrichment criteria as described in the protocol
  3. Must have a Prothrombin Time/International Normalization Ratio (PT/INR) <2.5 at the time of randomization if taking warfarin or another Vitamin K Antagonist (VKA)

Key Exclusion Criteria:

  1. Has a mechanical heart valve prosthesis (Note: transcatheter aortic valve replacement is not an exclusion)
  2. Has known moderate-to-severe mitral stenosis
  3. Has had successful ablation therapy or Left Atrial Appendage (LAA) occlusion/exclusion, or planned ablation or LAA occlusion/exclusion as described in the protocol
  4. Had an ischemic stroke within 2 days prior to randomization
  5. Has Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) estimated Glomerular Filtration Rate (eGFR) <15 mL/min/1.73m^2 within 14 days prior to randomization or on dialysis or expected to be started as described in the protocol
  6. Has a history of central nervous system bleeding within 30 days prior to randomization

Note: Other protocol-defined Inclusion/ Exclusion criteria apply

This study investigates the safety of investigational antibodies for people with atrial fibrillation, a condition where the heart beats too fast and unevenly. Atrial fibrillation can lead to blood clots, which may cause strokes. The study compares the effects of investigational medications with a commonly used medicine for preventing blood clots.

Participants in the study will receive either the investigational medications or the standard treatment. The study will monitor side effects, how well the medications reduce stroke risk, and how the body reacts over time. Researchers will also check if the body creates antibodies against the investigational medications, which could affect their effectiveness.

  • Who can participate: Participants must have atrial fibrillation and a need for ongoing blood clot prevention. They should have a specific health score indicating risk factors like age or other conditions. People with certain heart valve issues or recent strokes cannot join.
  • Study details: Participants will take either investigational medications or standard treatment and will have their health monitored. The study will involve monitoring for side effects and measuring how the body responds to the medications over time.
Updated on 23 Mar 2026. Study ID: KIC-REGENERON-ROXI-ATLAS, 29113
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Interested in the study?

This study is accepting only persons who receive care at a certain clinic or doctor or who are part of an invited group. Questions about this study can be directed to the study team listed in the description or contact your doctor to see if you are eligible.

Accepting Referrals by Invitation Only