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Study of Fitusiran for Preventing Bleeding in Boys Aged 1 to 12 with Hemophilia A or B

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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 hemophilia, a condition where blood does not clot properly, leading to excessive bleeding. The study involves children aged 1 to less than 12 years who have severe forms of hemophilia A or hemophilia B. The treatment being tested is called fitusiran, which is given as a solution for injection under the skin. Fitusiran is also known by its code name, SAR439774. The purpose of the study is to confirm the appropriate dose levels of fitusiran for these young patients.

During the study, participants will receive regular doses of fitusiran. The study will monitor how the treatment affects the levels of a protein called antithrombin in the blood, which plays a role in blood clotting. Researchers will also keep track of any side effects that participants might experience and measure the amount of fitusiran in the blood over time. The study aims to ensure that the treatment is safe and effective for children with severe hemophilia.

This trial is open-label, meaning that both the researchers and participants know which treatment is being administered. The study is multinational, involving participants from different countries. The goal is to gather enough information to determine the best dosing strategy for fitusiran in young children with hemophilia, ultimately aiming to improve their quality of life by reducing bleeding episodes.

The research process

The trial runs in 6 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Enrollment

    The study involves male children aged 1 to less than 12 years with severe hemophilia A or B. Participants must meet specific medical criteria, including having inhibitory antibodies to certain clotting factors.

    The participant's weight must be between 8 and less than 45 kg. Adequate venous access is required for blood draws.

  2. Step 2

    Initial assessment

    An initial assessment is conducted to confirm eligibility. This includes checking the participant's medical history and current health status.

  3. Step 3

    Treatment administration

    The medication used in the trial is fitusiran, also known as SAR439774. It is administered as a solution for injection under the skin (subcutaneous).

    The objective is to confirm the appropriate dose levels of fitusiran for the participants.

  4. Step 4

    Monitoring

    Participants are monitored for plasma antithrombin activity levels, which is a primary endpoint of the study.

    Secondary endpoints include monitoring for any adverse events and measuring fitusiran plasma concentrations.

  5. Step 5

    Follow-up

    Regular follow-up visits are scheduled to assess the participant's response to the treatment and to ensure their safety throughout the study.

  6. Step 6

    Completion

    The estimated end date for the trial is December 31, 2025. Upon completion, the data collected will be analyzed to determine the effectiveness and safety of fitusiran in the pediatric population.

Who can join the trial?

8 criteria

  • The participant must be a male child aged between 1 and less than 12 years old at the time of joining the study.
  • The participant must have severe hemophilia A or B. This means that the level of certain proteins in the blood, called Factor VIII (FVIII) or Factor IX (FIX), is very low (less than 1% for FVIII or less than or equal to 2% for FIX).
  • The participant must have inhibitory antibodies to FVIII or FIX. These are substances in the blood that can interfere with treatment. The participant must meet one of the following conditions:
    • An inhibitor titer (a measure of these antibodies) of 0.6 BU/mL or higher at the time of screening.
    • An inhibitor titer of less than 0.6 BU/mL at screening, but with medical records showing two past results of 0.6 BU/mL or higher.
    • An inhibitor titer of less than 0.6 BU/mL at screening, but with medical records showing one past result of 0.6 BU/mL or higher and a history of a strong immune response or severe allergic reaction.
    • The participant must have adequate peripheral venous access. This means that it should be possible to draw blood from the veins as needed for the study.
    • The participant must weigh between 8 kg and less than 45 kg at the time of joining the study.
    • The participant and their parent or legal guardian must be willing and able to follow the study requirements. The parent or guardian must provide signed written consent, and the participant must give written or spoken agreement to take part, according to local and national rules.

Who cannot join the trial?

3 criteria

  • Participants cannot be female. Only male participants are allowed.
  • Participants must be between the ages of 1 and less than 12 years old.
  • Participants must have severe **hemophilia A** or **B**. **Hemophilia** is a condition where the blood doesn't clot properly, leading to excessive bleeding.
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Investigated drugs

Fitusiran is a medication being studied for its potential to help children with hemophilia A or B. Hemophilia is a condition where blood doesn't clot properly, leading to excessive bleeding. Fitusiran is designed to help manage this condition by reducing the frequency of bleeding episodes. In this trial, the medication is given to children aged 1 to less than 12 years to determine the appropriate dose levels that can effectively prevent bleeding in these young patients.

What is already known about the treatment

Fitusiran – Fitusiran is administered as an injection under the skin, typically in a clinical setting. It is currently being studied in clinical trials, particularly for its use in treating hemophilia A and B in children. The main therapeutic indication for fitusiran is to reduce bleeding episodes in individuals with hemophilia. At the molecular level, fitusiran works by targeting and reducing the production of a protein called antithrombin, which helps to increase the generation of thrombin, a key enzyme in the blood clotting process. It is classified as an RNA interference therapeutic, which is a type of medication that uses small RNA molecules to interfere with the expression of specific genes.

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 severity of the condition can vary, with some individuals experiencing frequent and severe bleeding episodes, while others may have milder symptoms. Hemophilia is typically classified into two main types: Hemophilia A, which involves a deficiency of clotting factor VIII, and Hemophilia B, which involves a deficiency of clotting factor IX. The condition is usually inherited and primarily affects males, although females can be carriers and occasionally have symptoms.
Trial detailsLast updated 2 Oct 2026
Age0-17PhasePhase IVTrial ID2024-512501-76-00Protocol codeEFC15467Estimated enrolment32 patientsSponsorGenzyme Corp.

sourced from the EU Clinical Trials Register and site verification

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