A Phase 3, Randomized, Multicenter, Double-blind Study to Assess Stroke and Systemic Embolism Prevention with REGN7508, a Monoclonal Antibody Against Factor XI, Versus Apixaban in Participants with Atrial Fibrillation (ROXI-EVEREST)
Atrial fibrillation is a heart condition that causes an irregular pulse and raises the risk of blood clots and strokes. Doctors usually prescribe blood-thinning tablets like apixaban to protect against clots, but these medicines can sometimes lead to unwanted bleeding. This trial is testing an experimental medicine called REGN7508. It works differently from older blood thinners by targeting a specific clotting protein in the blood. Scientists hope this helps prevent dangerous clots without increasing the chance of serious bleeding. In this study, adults with atrial fibrillation will receive either REGN7508 or standard apixaban. Because it is a 'double-blind' trial, dummy treatments (placebos) are also used so neither the patient nor the doctor knows who gets which active medicine. Regular clinic visits will monitor participants' heart health, blood clotting, and overall wellbeing throughout the study.
At a glance
What is this study about?
Atrial fibrillation is a common heart condition where the heart beats irregularly. When this happens, blood can pool in the heart chambers, making it easier for harmful blood clots to form. If a clot travels to the brain, it can cause a stroke. To prevent this, doctors routinely prescribe blood-thinning medicines.
While current blood thinners like apixaban are effective, they come with a known drawback: they slow down the body's natural ability to stop bleeding. This means even minor cuts or internal bruises can become more serious. Researchers are searching for newer treatments that can safely stop dangerous clots in the heart while still allowing normal, healthy clotting when you get a cut or injury.
This Phase 3 study compares a new medicine, REGN7508, directly against apixaban. REGN7508 targets a specific part of the clotting system called Factor XI. By comparing both treatments across a large group of patients, doctors hope to find out if the new medicine provides the same strong protection against strokes while causing fewer bleeding side effects.
Key takeaways
- The study tests whether a new medicine, REGN7508, prevents strokes in atrial fibrillation as well as standard apixaban.
- Researchers hope the new medicine lowers the risk of serious bleeding complications.
- Every participant receives an active blood-thinning treatment; no one receives only a placebo.
- You will attend regular clinic visits for close health and heart checks.
- Joining is voluntary, and you can withdraw from the study at any time without affecting your usual care.
Who may be eligible?
This trial is open to adults aged 18 and older who have been diagnosed with atrial fibrillation and need medicine to lower their risk of blood clots and stroke. Both men and women may be eligible to take part.
Not everyone with atrial fibrillation will be suitable. For example, people with an active, serious bleeding problem or certain underlying medical conditions that make blood thinners unsafe may not be able to join.
A trial doctor will review your full medical history, carry out health checks, and explain whether this trial is safe and appropriate for your specific circumstances.
Could this study suit you?
Answer these quick questions to see if you may be eligible. This is a guide only — the research team makes the final call.
- I am aged 18 or older.
- I have been diagnosed with atrial fibrillation (irregular heartbeat).
- My doctor has recommended that I take blood-thinning medication to prevent strokes.
- I am able to attend regular hospital or clinic appointments for monitoring.
- I do not have an active, high-risk bleeding condition.
What does participation involve?
If you take part, you will be placed into one of two treatment groups by chance (like flipping a coin). One group receives the new medicine (REGN7508) along with dummy tablets. The other group receives standard apixaban tablets along with dummy injections. This 'double-dummy' design ensures that neither you nor your doctor knows which medicine is active, keeping the results fair and unbiased.
You will need to attend regular clinic appointments for health checks. These visits typically involve blood tests, heart traces (ECGs), blood pressure checks, and conversations about how you are feeling. You will also be asked to report any unusual bruising or bleeding straight away. The trial team will support you throughout the study period, which will last for several months to a few years depending on when you join.
Potential risks and benefits
Locations (15)
- —UnverifiedPortugal
- —UnverifiedGermany
- —UnverifiedItaly
- —UnverifiedCzechia
- —UnverifiedAustria
- —UnverifiedSpain
- —UnverifiedBelgium
- —UnverifiedNetherlands
- —UnverifiedPoland
- —UnverifiedSweden
- —UnverifiedGreece
- —UnverifiedLatvia
Common questions
What is atrial fibrillation?
Atrial fibrillation is a condition that causes an irregular and often fast heartbeat. It can increase your risk of blood clots and strokes.
What is a double-blind trial?
It means neither you nor your study doctor knows whether you are receiving the new medicine or the standard one. This helps ensure the trial results are completely unbiased.
Could I receive an inactive dummy medicine on its own?
No. Everyone in this study receives an active blood-thinning medicine—either the new medicine REGN7508 or standard apixaban. Dummy treatments are only used alongside the active drug so both groups look the same.
What should I do if I notice bleeding or bruising?
You should report any unusual bleeding, dark stools, or severe bruising to the study team immediately so they can check on you and provide advice.
Do I have to pay to take part?
No. The trial medicine and all study-related tests are provided free of charge, and help with travel expenses is often available.
How to find out more
Always speak to your GP or specialist before deciding to take part in a study.
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