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Study on Fitusiran for Preventing Bleeding in Males Aged 12 and Older with Severe Hemophilia A or B, with or without Inhibitors

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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 effects of a medication called fitusiran in individuals with severe hemophilia A or B. Hemophilia is a genetic disorder that affects the blood's ability to clot, leading to excessive bleeding. The study aims to understand how well fitusiran can prevent bleeding episodes in male participants aged 12 years and older, whether or not they have developed inhibitory antibodies to factor VIII or IX, which are proteins involved in blood clotting.

Participants in the study will receive fitusiran, which is administered as an injection under the skin. The study will observe the frequency of bleeding episodes while participants are on fitusiran treatment. The trial will also compare the bleeding rates during the fitusiran treatment period with those during the standard care period, which may involve other treatments. The study will last for a period of up to 36 months, during which participants will be monitored for any changes in their bleeding patterns and overall health.

In addition to fitusiran, the study will involve other treatments such as coagulation factor VIII, antithrombin III, coagulation factor IX, eptacog alfa (activated), and factor VIII inhibitor bypassing fraction. These treatments are typically used to help manage bleeding in people with hemophilia. The study will help determine the effectiveness and safety of fitusiran in reducing bleeding episodes compared to these other treatments. Participants will be closely monitored for any side effects or adverse events throughout the study.

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 informed about the trial's purpose, procedures, and your role. You will be asked to provide written consent to participate.

    You will undergo a screening process to confirm your eligibility, which includes verifying your diagnosis of severe hemophilia A or B.

  2. Step 2

    Initial assessment

    An initial assessment will be conducted to gather baseline information about your health and medical history.

    This may include blood tests and other evaluations to ensure you meet the study criteria.

  3. Step 3

    Treatment period

    You will receive the study medication, fitusiran, which is administered as an injection under the skin. The frequency and dosage will be explained to you by the study team.

    The primary goal is to assess the frequency of bleeding episodes while you are on this medication.

  4. Step 4

    Monitoring and follow-up

    Regular follow-up visits will be scheduled to monitor your health and the effects of the medication. These visits may include physical exams, blood tests, and questionnaires.

    You will be asked to report any bleeding episodes and other health changes during the study.

  5. Step 5

    End of study participation

    At the end of your participation, a final assessment will be conducted to evaluate your overall health and the outcomes of the treatment.

    You will receive information about any further steps or treatments if necessary.

Who can join the trial?

4 criteria

  • Must have a diagnosis of severe congenital hemophilia A or B. This means that the level of clotting factor VIII (FVIII) is less than 1% or the level of clotting factor IX (FIX) is 2% or less, as shown by a lab test or medical records.
  • If not currently on regular preventive treatment (using clotting factor concentrates or bypassing agents only when needed): Must have had at least 4 bleeding episodes in the last 6 months that required treatment with bypassing agents (for those with inhibitors) or clotting factor concentrates (for those without inhibitors).
  • Must be willing and able to follow the study requirements and provide written consent. If under the legal age of consent, must have assent and consent from a guardian, according to local laws.
  • Must be male.

Who cannot join the trial?

3 criteria

  • Patients who do not have **hemophilia** cannot participate. Hemophilia is a condition where blood does not clot properly, leading to excessive bleeding.
  • Only **male** patients can participate. Female patients are not eligible.
  • Patients who are considered part of a **vulnerable population** cannot participate. This term generally refers to groups who may be at a higher risk of harm or exploitation in a clinical trial.
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Investigated drugs

Fitusiran is a medication being studied for its ability to reduce bleeding episodes in people with severe hemophilia A or B. Hemophilia is a condition where the blood does not clot properly, leading to excessive bleeding. Fitusiran works by helping the body to better control bleeding. It is given as a regular treatment to prevent bleeding episodes, rather than treating them after they occur. This study is looking at how well fitusiran can prevent bleeding in people with hemophilia, even if they have developed antibodies that make other treatments less effective.

What is already known about the treatment

Fitusiran – Fitusiran is administered as an injection under the skin, typically once a month. It is currently being studied in clinical trials for its effectiveness and safety in treating severe hemophilia A or B in males aged 12 and older, with or without inhibitors to factor VIII or IX. The main purpose of fitusiran is to reduce the frequency of bleeding episodes in these patients. At the molecular level, fitusiran works by reducing the levels of a protein called antithrombin, which helps to increase the ability of the blood to clot. It is classified as a therapeutic agent for blood disorders, specifically targeting hemophilia.

Investigated diseases

Hemophilia – Hemophilia is a genetic disorder that affects the blood's ability to clot properly. It is caused by a deficiency in specific clotting factors, which are proteins in the blood that help control bleeding. People with hemophilia may experience prolonged bleeding after injuries, surgeries, or even spontaneously without any apparent cause. The condition can lead to frequent bleeding episodes, particularly in joints and muscles, which can cause pain and swelling. Over time, repeated bleeding into joints can lead to joint damage and reduced mobility. Hemophilia is typically inherited and primarily affects males, though females can be carriers of the gene.
Trial detailsLast updated 2 Oct 2026
Age18+ yearsPhasePhase IIITrial ID2022-500221-33-01Protocol codeEFC17574 (ATLAS-NEO)Estimated enrolment75 patientsSponsorSanofi-Aventis Recherche & Developpement

sourced from the EU Clinical Trials Register and site verification

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