Stroke and Systemic Embolism Prevention in Adult Participants With Atrial Fibrillation for Whom Oral Anticoagulation is Unsuitable

What this study involves

The registry says this study is recruiting. Individual locations may have different availability.

Study type

Interventional

Phase

Phase 3

Age range

18 years - Not specified

Sex eligible

All sexes

Healthy volunteers

Not accepted

Participants

2628 Estimated

These are starting points, not an eligibility decision. The research team must review the full requirements.

About the research

This study is researching 2 different experimental drugs called REGN7508 and REGN9933 (called "study drugs"). The study is focused on people who have atrial fibrillation, which means that the heart beats too fast and unevenly. When this happens, blood cannot move smoothly through the heart; it can slow down or pool in one spot, which can lead to the formation of blood clots.

REGN7508 and REGN9933 are designed to help stop blood clots forming in patients with atrial fibrillation. The aim of the study is to see how effective and safe REGN7508 and REGN9933, individually, are in preventing ischemic stroke or systemic embolism in people with atrial fibrillation who cannot or may choose to not take blood thinners.

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

• What side effects may happen from taking REGN7508 or REGN9933
• How well does REGN7508 or REGN9933 lower the risk of having an ischemic stroke and/or systemic embolism compared to the placebo
• How well does REGN7508 or REGN9933 lower the risk of having a major health problem affecting heart and blood circulation compared to placebo
• How well does REGN7508 or REGN9933 lower the risk of death compared to placebo
• How much REGN7508 or REGN9933 is in the blood at different times
• Whether the body makes antibodies against REGN7508 or REGN9933 (which could make the study drugs less effective or could lead to side effects)

Who may be able to participate?

The list below is the sponsor’s full registry wording. It can include conditions, prior treatment, test results and other requirements. A match in search does not mean you qualify.

Key Inclusion Criteria:

1. Has AF or flutter (paroxysmal or persistent), not considered to be secondary to a reversible cause
2. At moderate to high risk for stroke defined as:

1. CHA2DS2-VA \[C: Congestive heart failure; H: Hypertension; A2: Age ≥75 years (double points); D: Diabetes mellitus; S2: Stroke or TIA or Systemic embolism (double points); V: Vascular disease; A: Age 65-74 years\] score ≥4 OR
2. CHA2DS2-VA score of 3 AND at least 1 enrichment criteria as described in the protocol
3. Shared decision making between the participant and provider determining that the bleeding risk of Oral Anticoagulant (OAC) therapy outweighs the benefits, making the participant unsuitable for OAC therapy as described in the protocol

Key Exclusion Criteria:

1. Has a mechanical heart valve prosthesis (Note: transcatheter aortic valve replacement is not an exclusion)
2. Had an ischemic stroke within 2 days prior to randomization
3. Has persistent, uncontrolled hypertension (per investigator's discretion)
4. Has a history of Central Nervous System (CNS) bleeding within 30 days prior to randomization
5. Has a life expectancy less than 12 months
6. Has participated in a prior Factor XI (FXI) inhibitor study

Note: Other protocol-defined Inclusion/ Exclusion criteria apply

Treatment, groups and participation

The registry may describe treatments and study duration without a complete visit calendar. Ask the study team for the exact schedule, procedures, risks, costs and alternatives. Keep your usual care plan unless your treating clinician tells you otherwise.

Assignment

Random assignment

Masking

Quadruple masked

What researchers are measuring

Outcome measures describe what is being studied. They are not proof that a treatment works.

Primary measures

Secondary measures

Research locations (45)

The overall study status and a local site’s status can differ. Confirm that location’s availability before traveling.

45 locations

Study team and timeline

Lead sponsor

Regeneron Pharmaceuticals

Study start

Apr 3, 2026 Actual

Primary completion

Mar 28, 2029 Estimated

Study completion

Jun 26, 2029 Estimated

First posted

Feb 24, 2026 Actual

Last updated

Nov 10, 2026 Actual

Official study contacts