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Study on Marstacimab for Children with Severe Hemophilia A or B, With or Without Inhibitors

Verified siteInvestigationalNo placebo
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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 effectiveness and safety of a treatment called Marstacimab for children and teenagers with a condition known as Hemophilia. Hemophilia is a rare bleeding disorder where the blood doesn't clot properly, leading to excessive bleeding. The study includes participants with two types of hemophilia: Hemophilia A, which involves a deficiency in a protein called factor VIII, and Hemophilia B, which involves a deficiency in factor IX. The trial is open to participants under 18 years of age, with severe forms of these conditions, whether or not they have developed inhibitors, which are antibodies that can interfere with treatment.

The purpose of the study is to compare the new treatment, Marstacimab, with the standard treatment that participants have been receiving over the past year. Marstacimab is administered as a solution for injection using a pre-filled pen, which is a device that allows the medication to be injected under the skin. The study will last for about 48 weeks, during which participants will receive regular doses of Marstacimab. The trial aims to see if Marstacimab can reduce the number of bleeding episodes and improve the overall health of the joints, which are often affected by bleeding in people with hemophilia.

Throughout the study, the safety of Marstacimab will be closely monitored, including any side effects or reactions at the injection site. The trial will also assess the impact of the treatment on the participants' quality of life, using questionnaires designed for different age groups. This research is important for understanding how well Marstacimab works in young people with hemophilia and whether it can become a new option for managing this condition.

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

    Initial visit

    Upon joining the study, an initial visit is scheduled. During this visit, eligibility is confirmed based on age, weight, and medical history related to hemophilia.

    A detailed review of past treatment records and bleeding episodes is conducted to ensure all criteria are met.

  2. Step 2

    Baseline assessment

    A baseline assessment is performed to evaluate current health status. This includes physical examinations and laboratory tests.

    The assessment helps establish a starting point for measuring the effects of the study medication.

  3. Step 3

    Medication administration

    The study involves the administration of marstacimab, a solution for injection provided in a pre-filled syringe.

    The medication is administered subcutaneously (under the skin) at a frequency determined by the study protocol.

  4. Step 4

    Regular follow-up visits

    Regular follow-up visits are scheduled to monitor health and response to the medication.

    These visits include physical examinations, laboratory tests, and discussions about any side effects or concerns.

  5. Step 5

    End of study evaluation

    At the end of the study period, a final evaluation is conducted to assess the overall impact of the medication.

    This includes a comprehensive review of health changes, bleeding episodes, and any side effects experienced during the study.

Who can join the trial?

19 criteria

  • Participants must be male.
  • Participants must be between 1 to 18 years old.
  • Participants must have a minimum body weight:
    • For ages 12 to <18 years: at least 25 kg (about 55 pounds).
    • For ages 6 to <12 years: at least 19 kg (about 42 pounds).
    • For ages 1 to <6 years: minimum weight will be determined based on previous data.
    • Participants must have a diagnosis of severe hemophilia A or moderately severe to severe hemophilia B. This means their blood clotting factor levels are very low.
    • Participants must have at least 1 year of medical records showing their treatment and bleeding episodes.
    • For the Non-Inhibitor Cohort:
      • No detectable inhibitors against clotting factors.
      • No history of high-level inhibitors in the past 5 years.
      • No low-level inhibitors that do not respond to treatment in the past 5 years.
      • If they had immune tolerance therapy (ITI), it must have been completed successfully at least 5 years ago.
      • At least 50 documented treatment days with clotting factor products.
      • Must be on a stable routine treatment to prevent bleeding, with at least 80% compliance over the past year.
      • For the Inhibitor Cohort:
        • Current high-level inhibitors or low-level inhibitors that do not respond to treatment.
        • Participants with a history of inhibitors may be considered on a case-by-case basis.
        • For hemophilia A: at least 12 bleeding episodes in the past year requiring treatment.
        • For hemophilia B: at least 8 bleeding episodes in the past year requiring treatment.
        • Must be on an on-demand treatment regimen, with documented bleeding episodes over the past year.
        • Participants on routine treatment to prevent bleeding must have at least 80% compliance over the past year.

Who cannot join the trial?

13 criteria

  • Participants must not have any other serious medical conditions that could interfere with the study.
  • Participants must not have a history of allergic reactions to the study medication or similar medications.
  • Participants must not be taking any other medications that could interfere with the study medication.
  • Participants must not have any bleeding disorders other than hemophilia.
  • Participants must not have any active infections that require treatment.
  • Participants must not have any liver disease or liver function problems.
  • Participants must not have any kidney disease or kidney function problems.
  • Participants must not have any heart disease or heart function problems.
  • Participants must not have any history of drug or alcohol abuse.
  • Participants must not have any mental health conditions that could interfere with the study.
  • Participants must not have participated in another clinical trial within the last 30 days.
  • Participants must not have received any blood products within the last 30 days.
  • Participants must not have any planned surgeries during the study period.
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Investigated drugs

Marstacimab is a medication being studied for its potential to help people with severe hemophilia A or moderately severe to severe hemophilia B. Hemophilia is a condition where the blood does not clot properly, leading to excessive bleeding. Marstacimab is designed to be used as a regular treatment to prevent bleeding episodes. It works by helping the blood to clot more effectively, which can reduce the frequency and severity of bleeding events. This study is looking at how well marstacimab works and how safe it is for children under 18 years old who have hemophilia, with or without inhibitors, which are substances that can interfere with treatment.

What is already known about the treatment

Marstacimab – Marstacimab is administered as an injection and is currently being studied for its effectiveness and safety in children under 18 years old with severe hemophilia A or moderately severe to severe hemophilia B. This medication is in the clinical trial phase, and its main therapeutic use is to prevent bleeding episodes in these patients. Marstacimab works by targeting specific proteins in the blood that are involved in clotting, helping to maintain normal clotting function. It is classified as a therapeutic agent for blood disorders, specifically for managing 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 one of the clotting factors, typically factor VIII (Hemophilia A) or factor IX (Hemophilia B). This deficiency leads to prolonged bleeding after injuries, surgeries, or even spontaneously without any apparent cause. Over time, repeated bleeding episodes, especially into joints and muscles, can lead to joint damage and pain. The severity of hemophilia varies, with severe cases experiencing frequent bleeding episodes and milder cases having fewer issues. The condition is usually inherited and primarily affects males, though females can be carriers and occasionally have symptoms.
Trial detailsLast updated 7 Oct 2026
Age0-17PhasePhase IIITrial ID2022-500495-65-00Protocol codeB7841008Estimated enrolment100 patientsSponsorPfizer Inc.

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