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Weekly shot could transform bleeding prevention for kids with hemophilia

NCT ID NCT05611801

Disease control Sponsor: Pfizer Source: ClinicalTrials.gov ↗

What the study statuses mean

This study's is highlighted.

Recruitment status, easiest to join first

Recruiting now This study
This trial is taking on new participants right now.
Not yet recruiting
Registered, but not yet taking participants.
By invitation only
Not open to general applications. Only people the study team invites can take part.
Paused
Paused for now. It may or may not start again.
Ongoing
Running, but no longer taking on new participants.
Completed
The trial has finished. Results may not be published yet.
Stopped early
Stopped early, before it reached the end. That can be for many reasons, including safety.
Cancelled
Cancelled before anyone took part.

Expanded access (not trials)

Expanded access
Not a trial. This treatment can be requested outside a study, case by case, for people who qualify.
Expanded access (paused)
Not a trial. The treatment can normally be requested outside a study, but is unavailable right now.
Expanded access (ended)
Not a trial. The treatment could once be requested outside a study, but no longer can.
Approved
The treatment has been approved, so it is available normally rather than through this programme.

When the status isn't known

Details not published
The full record has not been published yet, so there is little to show here.
Status unknown
This status has not been confirmed recently, so it may be out of date.

First seen Jun 27, 2026 · Last updated Aug 11, 2026 · Updated 2 times

Summary

This study tests a new medicine called marstacimab in children aged 1 to 17 with severe hemophilia A or B. The medicine is given as a weekly shot under the skin to prevent bleeding episodes. Researchers will compare how well it works to the children's own past year of standard treatment. The goal is to see if marstacimab can reduce bleeds and improve daily life.

This is an AI summary of the original study and may miss details. Read our disclaimer.

Study facts

What this study's own registry entry says, in plain language.

Phase

Phase 3

Large-scale testing in a bigger group. Usually the last step before a treatment can be approved.

Participants

About 100 people

The number the study aims to enrol. It can still change while the study runs.

Started

Dec 2022

Expected to finish

Sep 2028

An estimate. End dates often move.

Lead sponsor

A company

The lead sponsor is a pharmaceutical, biotech, or medical-device company.

Who can take part

This study's own entry requirements. Only the study team can say for certain whether you qualify.

Ages

1 year to 17 years

Sex

Male participants only

Healthy volunteers

Not accepted

This study is not open to healthy volunteers. The entry requirements below say who it is open to.

Show the full entry requirements

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion Criteria: * Male participants of appropriate age and required minimum weight * Participants aged 12 to 17 years must be at least 25 kgs at time of consent. * Participants aged 6 to 11 years must be at least 19 kgs at time of consent. * Minimum weight requirement for participants aged 1 to 5 years is to be determined. * Participants with a diagnosis of severe hemophilia A or moderately severe to severe hemophilia B * Participants must have at least 1 year of diary and/or medical records available in which exogenous FVIII or FIX replacement or bypass agent infusions and hemophilic bleeding episodes were consistently documented over the 12 months prior to the time of consent. Participants who are enrolled into the Non-Inhibitor Cohort must also meet the following criteria: * No current detectable inhibitor and no documented history of inhibitors in the 5 years prior to consent * Must have at least 50 exposure days to FVIII/FIX replacement products * Must be at least 80% compliant with a stable and effective routine prophylaxis regimen with FVIII/FIX replacement products, for at least 12 months prior to consent Participants who are enrolled into the Inhibitor Cohort must also meet the following criteria: * Documentation of current high titer inhibitor (≥5 BU/mL); or current low titer inhibitor (\<5 BU/mL) refractory to FVIII or FIX replacement and with FVIII or FIX recovery \<60% of expected within previous 12 months prior to the time of consent * Participants who have documented inhibitors while on factor-replacement therapy but who do not meet the high quantitative inhibitor criteria described in the prior bullet at the time of screening (eg, participant with a previously documented high-titer inhibitor ≥5 BU/mL) and whose condition precludes re-challenge with FVIII or FIX replacement may be considered for eligibility on a case-by-case basis with discussion and agreement from the Pfizer medical monitor. * Hemophilia A participants with on-demand treatment regimen with ≥12 bleeding episodes or hemophilia B participants with on-demand treatment regimen with ≥8 bleeding episodes (spontaneous or traumatic) necessitating treatment with bypass factor in the 12 months prior to informed consent * Participants must be on an on-demand bypass treatment regimen during the 12 months prior to informed consent Exclusion Criteria: * Known coronary artery, thrombotic, or ischemic disease, or current evidence of congenital or acquired thrombophilic disease such as Anti-thrombin III deficiency, Factor V Leiden mutation, prothrombin 20210 mutation, protein C deficiency, protein S deficiency and antiphospholipid syndrome. * Known planned surgical procedure during the planned study period * Known hemostatic defect other than hemophilia A or B * Abnormal hematology, renal or hepatic function laboratory results at screening * Other acute or chronic medical or psychiatric condition that may increase the risk associated with study participation or investigational product administration or may interfere with the interpretation of study results and, in the judgment of the investigator * Individuals with known allergic reaction or hypersensitivity to hamster protein or other components of the study intervention * Current routine prophylaxis with bypassing agent, non-coagulation non-factor replacement therapy (eg, emicizumab), or any previous treatment with a gene therapy product for treatment of hemophilia * Participants with inhibitors who are being treated using a prophylaxis treatment regimen with a bypass agent, and, participants who have previously received non-factor-based hemophilia therapy (eg, fitusiran, concizumab, emicizumab) will be considered on a case-by-case basis, only after discussion and agreement between the investigator and the Pfizer medical monitor * Regular use of immunomodulatory medications (eg, IVIG, routine systemic corticosteroids, rituximab) * Use of systemic antifibrinolytics, medications that may increase the risk of bleeding, and certain non-steroidal anti-inflammatory drugs within 120 hours of first dose of study intervention and while on study * Ongoing or planned use of ITI, or prophylaxis with FVIII or FIX replacement at any time after initiation of treatment with study intervention * Participation in other studies involving investigational drug(s) or investigational vaccine(s) within 30 days (or as determined by local requirements) or 5 half-lives prior to study entry or during study participation * Previous exposure to marstacimab during participation in other marstacimab clinical studies * CD4 cell count ≤200/uL if HIV-positive * Abnormal ECG of clinical relevance that may affect participant safety or interpretation of study results * Investigator site staff members directly involved in the conduct of the study and their family members, site staff members otherwise supervised by the investigator, and sponsor and sponsor delegate employees directly involved in the conduct of the study and their family members

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Conditions

The condition(s) this trial relates to.

hemophilia A hemophilia B Hemorrhage severe hemophilia A

As listed by the trial registrant

The condition terms exactly as the trial's registrant entered them.

Hemophilia A Hemophilia B

How to take part

Only the study team decides who joins. These are the ways to reach them.

  1. The places running it

    60 sites in 21 countries. The list below names each one and where it is.

  2. The official record

    ClinicalTrials.gov lists the study team's own contact details, including names and phone numbers. We don't republish those.

    Open the record ↗

  3. A doctor treating you

    A doctor who knows your case can contact a study site on your behalf, and can tell you whether this study is worth pursuing at all.

Contacts and locations

Locations

  • Aarhus Universitetshospital, Skejby

    RECRUITING

    Aarhus N, 8200, Denmark

  • Aarhus University

    RECRUITING

    Aarhus N, DK-8200, Denmark

  • Adana Acibadem Hastanesi Pediatrik Hematoloji Bilim Dali

    RECRUITING

    Adana, 01130, Turkey (Türkiye)

  • Arbesu Hematología

    RECRUITING

    Mendoza, M5501, Argentina

  • Arké SMO S.A de C.V

    RECRUITING

    Veracruz, 91900, Mexico

  • Azienda Ospedaliero Universitaria di Parma

    RECRUITING

    Parma, 43126, Italy

  • Azienda Ospedaliero-Universitaria Città della Salute e della Scienza di Torino

    RECRUITING

    Torino, 10126, Italy

  • Beijing Children's hospital, Capital Medical University

    RECRUITING

    Beijing, Beijing Municipality, 100045, China

  • Birmingham Children's Hospital

    RECRUITING

    Birmingham, B4 6NH, United Kingdom

  • Centro Estadual de Hemoterapia e Hematologia Marcos Daniel Santos - HEMOES

    ACTIVE_NOT_RECRUITING

    Maruípe, Vitória, 29047-105, Brazil

  • Charité Campus Virchow-Klinikum

    RECRUITING

    Berlin, 13353, Germany

  • Charlotte Maxeke Johannesburg Academic Hospital

    ACTIVE_NOT_RECRUITING

    Johannesburg, Gauteng, 2193, South Africa

  • Detska fakultna nemocnica Kosice

    RECRUITING

    Košice, 040 11, Slovakia

  • Detska nemocnice FN Brno

    RECRUITING

    Brno, Brno-město, 613 00, Czechia

  • Ege Universitesi Tip Fakultesi Hastanes

    RECRUITING

    Izmir, 35100, Turkey (Türkiye)

  • Ege University

    RECRUITING

    Izmir, 35010, Turkey (Türkiye)

  • Erciyes University Faculty of Medicine Pediatric

    RECRUITING

    Kayseri, 38039, Turkey (Türkiye)

  • Erciyes University Health Application and Research Center Directorate

    RECRUITING

    Melikgazi, Kayseri, 38039, Turkey (Türkiye)

  • Evelina London Children's Hospital

    RECRUITING

    London, SE1 7EH, United Kingdom

  • Fakultni nemocnice Brno

    RECRUITING

    Brno, 625 00, Czechia

  • Freeman Hospital

    RECRUITING

    Newcastle upon Tyne, NE7 7DN, United Kingdom

  • Gazi Universitesi Tip Fakultesi Hastanesi Cocuk Hematologi Bolumu

    RECRUITING

    Ankara, 06560, Turkey (Türkiye)

  • Gazi University Health Research and Application Center Gazi Hospital

    RECRUITING

    Ankara, 06560, Turkey (Türkiye)

  • Gazi University Medical Faculty

    RECRUITING

    Ankara, 06500, Turkey (Türkiye)

  • Hamilton Health Sciences - McMaster University/McMaster Children's Hospital

    RECRUITING

    Hamilton, Ontario, L8N 3Z5, Canada

  • Hospital Universitario La Paz

    RECRUITING

    Madrid, Madrid, Comunidad de, 28046, Spain

  • Hospital Universitario Miguel Servet

    RECRUITING

    Zaragoza, 50009, Spain

  • Hyogo prefectural Kobe Children's Hospital

    RECRUITING

    Kobe, Hyōgo, 650-0047, Japan

  • Hôpital Universitaire Necker Enfants Malades

    RECRUITING

    Paris, 75015, France

  • IRCCS Istituto Giannina Gaslini

    RECRUITING

    Genoa, Liguria, 16147, Italy

  • Institute of hematology&blood disease hospital

    RECRUITING

    Tianjin, Tianjin Municipality, China

  • Intermountain - Primary Children's Hospital

    RECRUITING

    Salt Lake City, Utah, 84113, United States

  • Istanbul Universitesi Istanbul Tıp Fakultesi Hastanesi

    RECRUITING

    Istanbul, İ̇stanbul, 34093, Turkey (Türkiye)

  • Istituto Clinico Humanitas - Humanitas Mirasole SPA

    RECRUITING

    Rozzano, Milan, 20089, Italy

  • Jiangxi Provincial People's Hospital

    RECRUITING

    Nanchang, Jiangxi, 330006, China

  • K. J. Somaiya Hospital and Research Centre, Somaiya Ayurvihar Complex

    RECRUITING

    Mumbai, Maharashtra, 400022, India

  • King Fahad Specialist Hospital

    TERMINATED

    Dammam, 32253, Saudi Arabia

  • Kyung Hee University Hospital at Gangdong

    RECRUITING

    Seoul, Seoul-teukbyeolsi [seoul], 05278, South Korea

  • Kyungpook National University Hospital

    RECRUITING

    Daegu, Taegu-kwangyǒkshi, 41944, South Korea

  • Medizinische Universität Wien

    RECRUITING

    Vienna, State of Vienna, 1090, Austria

  • Motol University Hospital

    RECRUITING

    Prague, 150 06, Czechia

  • Murdoch Children's Research Institute

    RECRUITING

    Parkville, 3052, Australia

  • Nagano Children's Hospital

    RECRUITING

    Azumino, Nagano, 399-8288, Japan

  • Nara Medical University Hospital

    RECRUITING

    Kashihara, Nara, 634-8522, Japan

  • National Taiwan University Hospital

    RECRUITING

    Taipei, 100, Taiwan

  • Nil Ratan Sircar Medical College and Hospital

    RECRUITING

    Kolkata, West Bengal, 700014, India

  • Nirmal Hospital Pvt Ltd.

    RECRUITING

    Surat, Gujarat, 395002, India

  • Ondokuz Mayıs Universitesi

    RECRUITING

    Samsun, 55200, Turkey (Türkiye)

  • Ospedale Pediatrico Bambino Gesù IRCCS

    RECRUITING

    Rome, ROMA, 00165, Italy

  • Rigshospitalet

    RECRUITING

    Copenhagen, Capital Region, 2100, Denmark

  • Royal Manchester Children's Hospital

    RECRUITING

    Manchester, M13 9WL, United Kingdom

  • Royal Victoria Infirmary

    RECRUITING

    Newcastle upon Tyne, England, NE1 4LP, United Kingdom

  • Saga University Hospital

    RECRUITING

    Saga, 849-8501, Japan

  • Saitama Prefectural Children's Medical Center

    RECRUITING

    Saitama-shi, Saitama, 330-8777, Japan

  • Severance Hospital, Yonsei University Health System

    RECRUITING

    Seoul, Seoul-teukbyeolsi [seoul], 03722, South Korea

  • Sheba Medical Center

    RECRUITING

    Ramat Gan, Central District, 5262100, Israel

  • Southern Medical University Nanfang Hospital

    RECRUITING

    Guangzhou, Guangdong, 510515, China

  • Stollery Children's Hospital

    RECRUITING

    Edmonton, Alberta, T6G 2B7, Canada

  • Taichung Veterans General Hospital

    RECRUITING

    Taichung, 407219, Taiwan

  • The Affiliated Hospital of Guizhou Medical University

    RECRUITING

    Guiyang, Guizhou, 550004, China

  • Tongji Hospital of Tongji Medical College of HUST/Pediatric Hematology Department Pharmacy

    RECRUITING

    Wuhan, Hubei, 430030, China

  • Tongji Hospital of Tongji Medical College of Huazhong University of Science and Technology

    RECRUITING

    Wuhan, Hubei, 430030, China

  • Univerzitna nemocnica Martin

    RECRUITING

    Martin, 036 59, Slovakia

  • Worthwhile Clinical Trials

    ACTIVE_NOT_RECRUITING

    Benoni, Gauteng, 1500, South Africa

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