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Efficacy and Safety of BAY 3670549 in Adults with Atrial Fibrillation: A Randomized, Double‑Blind, Placebo‑Controlled Phase 2 Study

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What is this trial about?

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

The condition being studied is atrial fibrillation, a heart rhythm problem where the upper chambers beat irregularly and often rapidly. The investigation compares an experimental medicine called BAY 3670549 with a placebo. The test medicine is supplied as a powder that is mixed with liquid before it is given to participants.

The purpose of the study is to determine whether the experimental drug can restore a normal heart rhythm, known as sinus rhythm. In the trial, adult participants are randomly assigned to receive either the study drug or the placebo. The assigned treatment is delivered by a short intravenous infusion, and participants are observed for at least three hours to see if their heart rhythm changes from the irregular pattern to a steady one without needing additional procedures. Safety checks are performed throughout the visit, and a blood sample is taken at the end of the infusion to measure how much of the medicine is present in the body.

The research process

The trial runs in 7 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Randomization

    After you join the study, you are assigned by a computer to receive either the test medication BAY 3670549 or a matching placebo. the assignment is done without you or the study staff knowing which one you receive.

  2. Step 2

    Baseline assessments

    Before the infusion starts, clinical staff measure your vital signs, perform an electrocardiogram (ecg) to record your heart rhythm, and collect blood samples for laboratory tests. these measurements provide a reference point for later comparisons.

  3. Step 3

    Infusion administration

    You receive a single intravenous infusion. if you are in the test group, the infusion contains BAY 3670549 at a dose of 00 mg, prepared as a powder for solution for infusion. if you are in the placebo group, the infusion contains an inert solution with no active drug. the infusion is given once, over the period specified in the study protocol.

  4. Step 4

    Monitoring for rhythm conversion

    While the infusion is running and for at least three hours after it starts, you are continuously monitored with an ecg. the goal is to observe whether your heart rhythm changes from atrial fibrillation to sinus rhythm and stays in sinus rhythm for at least one minute. this observation is made before any rescue therapy or other standard cardioversion treatment is used.

  5. Step 5

    Blood sampling for drug level

    At the end of the infusion, a blood sample is taken to measure the plasma concentration of BAY 3670549. this helps determine how much of the medication is present in your bloodstream.

  6. Step 6

    Observation for adverse events

    Throughout the infusion and the monitoring period, clinical staff watch for any treatment‑emergent adverse events (teaes), which are any new or worsening medical problems that occur after the study medication is given. any such events are recorded and evaluated.

  7. Step 7

    Study completion

    After the three‑hour monitoring window and any required follow‑up assessments, your participation in this phase of the study ends. the collected data are used to assess the efficacy and safety of BAY 3670549 compared with placebo.

Who can join the trial?

9 criteria

  • You must be between 18 and 85 years old when you sign the consent form.
  • You need to be hemodynamically stable (your blood pressure and circulation are stable) and not need an emergency electric shock to fix your heart rhythm.
  • You must have a current episode of atrial fibrillation (AF) that has lasted at least 3 hours but no more than 30 days at the time you are assigned to a treatment group.
  • Your doctor must decide that you have a reason to undergo electrical cardioversion (a controlled electric shock to restore a normal heart rhythm) based on standard medical guidelines.
  • Before randomization you must have started and reached the proper level of anticoagulation therapy (medication that helps prevent blood clots) and have completed any imaging needed to check for left atrial thrombi (blood clots in the upper left chamber of the heart) as recommended for your situation.
  • Your body mass index (BMI) must be between 18 and 39.9 kilograms per square meter, which is a measure of weight relative to height.
  • If you are of child‑bearing potential, you or your partner must use contraception methods that follow local rules for participants in clinical studies.
  • You must sign the informed consent form and agree to follow all the requirements listed in it.
  • You must be willing and able to use a continuous electrocardiogram (ECG) recording device at home, return it as instructed, and take part in scheduled telephone follow‑up calls.

Who cannot join the trial?

12 criteria

  • Having current atrial flutter (a rapid heart rhythm different from atrial fibrillation) or a mix of atrial fibrillation and atrial flutter.
  • Using anti‑arrhythmic medicines of class I or III (drugs that try to keep the heart rhythm normal) within five half‑lives before the study drug, such as oral amiodarone taken in the past three months.
  • Having very high blood pressure (systolic ≥ 180 mmHg) or very low blood pressure (systolic < 90 mmHg) measured at randomization.
  • Having atrial fibrillation caused by an acute, reversible stress (for example recent heart surgery, infection, pneumonia) or having undergone an ablation procedure within the past month.
  • Having a medical reason that makes electrical cardioversion (a shock to restore normal rhythm) unsafe on the day the study drug is given.
  • Having a severely enlarged left atrium (left atrial diameter greater than 5 cm) measured within the last six months, or lacking a recent measurement after a major heart event.
  • Being unable to convert the current atrial fibrillation episode to normal rhythm with medication or electrical shock.
  • Having severe valve disease of the heart, such as very leaky mitral valve or very narrowed aortic valve.
  • Having moderate to severe heart failure (NYHA class III or higher) or being actively treated for an acute worsening of heart failure on the treatment day.
  • Having any major cardiovascular event in the past three months, including stroke, heart attack (myocardial infarction), unstable chest pain (unstable angina), heart surgery, transcatheter valve replacement, coronary stent placement (PCI), or bypass surgery (CABG).
  • Having severe kidney problems, defined as an estimated glomerular filtration rate (eGFR) less than 30 mL/min/1.73 m², or needing dialysis.
  • Having severe liver disease, classified as Child‑Pugh class C.
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Investigated drugs

BAY 3670549 is an experimental medication being studied to see if it can help patients with atrial fibrillation return to a normal heart rhythm (sinus rhythm). In the trial, the drug is given through an IV infusion, where a powder is mixed with liquid and delivered directly into the bloodstream. Researchers are looking at how well it works, how safe it is, how the body processes it, and how well patients tolerate it.

What is already known about the treatment

BAY 3670549 - This drug is supplied as a powder that is mixed with liquid and given through an IV infusion. It is currently an investigational medicine being tested in a Phase 2 study and has not been approved for general use. The trial is looking at its ability to help people with atrial fibrillation return to a normal heart rhythm. It works by influencing the electrical signals that control the heartbeat, and it is being studied as a new anti‑arrhythmic agent.

Investigated diseases

Atrial fibrillation - Atrial fibrillation is an irregular and often rapid heart rhythm that originates in the upper chambers of the heart. It may start as brief, occasional episodes that stop on their own, known as paroxysmal AF. Over time, these episodes can become longer and may continue without stopping, which is called persistent or permanent AF. The irregular rhythm can cause feelings of fluttering in the chest, shortness of breath, or reduced ability to exercise. As the condition progresses, the heart’s ability to pump blood efficiently may change, leading to further symptoms.
Trial detailsLast updated 7 Oct 2026
Age18+ yearsPhasePhase IITrial ID2025-523807-31-00Protocol code22961Estimated enrolment132 patientsSponsorBayer AG

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