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Hemophilia APhase 3NCT05145127

Open-Label Extension Study of Marstacimab in Hemophilia Participants With or Without Inhibitors

A Phase 3 study testing PF-06741086 in people with Hemophilia A and Hemophilia B, run by Pfizer at 78 sites in 24 countries.

Recruiting

Looking for participants now. Contact the study team or a site below to ask about taking part.

Sites and contacts
Official record
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Trial summary

Study B7841007 is an open-label extension study to assess the long-term safety, tolerability, and efficacy of prophylaxis treatment with marstacimab in participants who did not require "Early Termination" from the Phase 3 Study B7841005 and from the Phase 3 Study B7841008. Read more about this study

Who is it for?
Ages 1 year to 74 years, men only
Conditions the study is for
Hemophilia A, Hemophilia B
What is being tested?
PF-06741086
Type of treatment
Injection or infusion
Could I receive a placebo?
No, everyone receives an active treatment
How many people
245 participants
Where
78 sitesin 24 countries
Study dates
17 Nov 2021to 31 Jul 2030
Phase
Phase 3
Are there results?
Not yet: the study is under way

Key requirements

Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.

  • Ages 1 year to 74 years
  • Men only
  • No healthy volunteers
  • Child, Adult, Older adult

Who may be able to join

  • All participants will have a minimum body weight as defined by parent studies
  • Participants who are willing and able to comply with all scheduled visits, treatment plan, laboratory tests, and other study procedures.
  • Participants have successfully completed participation in parent studies, defined as did not require "Early Termination"

Who cannot join

  • Previous or current treatment for or history of coronary artery disease, venous or arterial thrombosis (CTCAE Grade >3), or ischemic disease (except catheter-associated thrombosis)
  • Abnormal renal function as defined by eGFR <30 mL.min/1.73 m(2)
  • Known planned surgical procedure during the planned study period
  • Unstable hepatic function as determined by the Investigator clinical assessment and review of the participant's most recent laboratory results, which would make the participant inappropriate for the study
  • For participants known to be HIV+, worsening disease status as determined by the Investigator clinical assessment and review of participant's most recent laboratory results, to include recent locally available CD4 count (if available), which would make the participant inappropriate for the study
  • Regular, concomitant therapy with immunomodulatory drugs (eg, IVIG, and routine systemic corticosteroids, rituximab)
Show all 9Show fewer
  • Ongoing or planned use of immune tolerance induction or prophylaxis with FVIII or FIX replacement during the study
  • Participation in other study involving investigational drug(s) or investigational vaccine(s) within 30 days or 5 half-lives prior to or during study participation, with the exception of participation in parent studies
  • Investigator site staff or Pfizer employees directly involved in the conduct of the study, site staff otherwise supervised by the Investigator, and their respective family members

Trial locations and contacts

78 sites in 24 countries. Contact the study team or a site near you to ask about taking part.

Pfizer CT.gov Call Center contact

1-800-718-1021

ClinicalTrials.gov_Inquiries@pfizer.com

78 sites in 24 countries

Turkey (Türkiye)13 sites, 13 recruiting

  • Acibadem Adana Hospital

    Adana, 01130

    Recruiting

  • Hacettepe University Faculty of Medicine

    Ankara, 06100

    Recruiting

  • Hacettepe University Medical Faculty Hospital

    Ankara, 06230

    Recruiting

  • Gazi University Medical Faculty

    Ankara, 06500

    Recruiting

  • Gazi University Health Research and Application Center Gazi Hospital

    Ankara, 06560

    Recruiting

  • Gaziantep University Şahinbey Research and Practice Hospital

    Gaziantep, 27310

    Recruiting

  • Istanbul University Oncology Institute

    Istanbul, 34093

    Recruiting

  • Istanbul Universitesi Klinik Arastirmalar Mukemmeliyet Uygulama ve Arastirma Merkezi

    Istanbul, 34452

    Recruiting

  • Ege University Faculty of Medicine

    Izmir, 35040

    Recruiting

  • Ege University Faculty of Medicine

    Izmir, 35100

    Recruiting

  • Erciyes University Faculty of Medicine

    Kayseri, 38039

    Recruiting

  • Ondokuz Mayıs University Healthcare Practice and Research Center

    Samsun, 55200

    Recruiting

  • Ondokuz Mayıs University Medical Faculty Local Laboratory

    Samsun, 55280

    Recruiting

Other trials in Turkey (Türkiye)

China7 sites, 7 recruiting

  • Beijing Children's Hospital, Capital Medical University

    Beijing, 100045

    Recruiting

  • Nanfang Hospital, Southern Medical University

    Guangzhou, Guangdong, 510515

    Recruiting

  • The Affiliated Hospital of Guizhou Medical University

    Guiyang, Guizhou, 550004

    Recruiting

  • Jiangxi Provincial People's Hospital

    Nanchang, Jiangxi, 330006

    Recruiting

  • Jiangxi Provincial People's Hospital

    Nanchang, Jiangxi, 330038

    Recruiting

  • Institute of hematology&blood disease hospital

    Tianjin, Tianjin Municipality

    Recruiting

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

    Wuhan, Hubei, 430030

    Recruiting

Other trials in China

Japan7 sites, 5 recruiting

  • Nagano Children's Hospital

    Azumino, Nagano, 399-8288

    Recruiting

  • Hiroshima University Hospital

    Hiroshima, 734-8551

    Active, not recruiting

  • Nara Medical University Hospital

    Kashihara, Nara, 634-0813

    Recruiting

  • Saitama Medical University Hospital

    Lruma-gun, Saitama, 350-0495

    Recruiting

  • Nagoya University Hospital - Transfusion Medicine

    Nagoya, Aichi-ken, 466-8560

    Active, not recruiting

  • Saga University Hospital

    Saga, 849-8501

    Recruiting

  • Saitama Children's Medical Center

    Saitama-shi, Saitama, 330-8777

    Recruiting

Other trials in Japan

United States4 sites, 3 recruiting

  • University of Iowa

    Iowa City, Iowa, 52242

    Active, not recruiting

  • Northwell Health HTC

    New Hyde Park, New York, 11040

    Recruiting

  • The Feinstein Institutes for Medical Research

    Philadelphia, Pennsylvania, 19195

    Recruiting

  • Washington Institute for Coagulation d/b/a WACBD

    Seattle, Washington, 98101

    Recruiting

Other trials in United States

Hong Kong4 sites, 4 recruiting

  • The University of Hong Kong (HKU)-Queen Mary Hospital (QMH)

    Hong Kong, 999077

    Recruiting

  • Prince of Wales Hospital

    Hong Kong

    Recruiting

  • Queen Mary Hospital

    Hong Kong

    Recruiting

  • The Chinese University of Hong Kong

    Ma Liu Shui

    Recruiting

Other trials in Hong Kong

India4 sites, 4 recruiting

  • Nil Ratan Sircar Medical College and Hospital

    Kolkata, West Bengal, 700014

    Recruiting

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

    Mumbai, Maharashtra, 400022

    Recruiting

  • Sahyadri Super Speciality Hospital

    Pune, Maharashtra, 411004

    Recruiting

  • Nirmal Hospital Pvt Ltd.

    Surat, Gjuarat, 395002

    Recruiting

Other trials in India

Italy4 sites, 4 recruiting

  • IRCCS Istituto Giannina Gaslini

    Genoa, Liguria, 16147

    Recruiting

  • Fondazione IRCCS Cà Granda Ospedale Maggiore Policlinico

    Milan, 20122

    Recruiting

  • AOU Policlinico Umberto I

    Roma, RM, 00161

    Recruiting

  • Istituto Clinico Humanitas

    Rozzano, Milano, 20089

    Recruiting

Other trials in Italy

Serbia4 sites, 3 recruiting

  • Clinical Center of Serbia

    Belgrade, 11000

    Not yet recruiting

  • Institute for Mother and Child healthcare "Dr Vukan Cupic"

    Belgrade, 11000

    Recruiting

  • Clinical Center Nis

    Niš, 18000

    Active, not recruiting

  • Clinical Center Nis

    Niš, 18000

    Recruiting

Other trials in Serbia

Spain4 sites, 4 recruiting

  • Hospital Universitario A Coruna

    A Coruña, 15006

    Recruiting

  • Hospital Universitario Vall d´Hebron

    Barcelona, 08035

    Recruiting

  • Hospital Universitario La Paz

    Madrid, 28046

    Recruiting

  • Hospital Universitario Miguel Servet

    Zaragoza, 50009

    Recruiting

Other trials in Spain

United Kingdom4 sites, 4 recruiting

  • Birmingham Children's Hospital

    Birmingham, B4 6NH

    Not yet recruiting

  • Guy's & St Thomas' NHS Foundation Trust

    London, London, CITY of, SE1 9RT

    Recruiting

  • Guy's & St Thomas' NHS Foundation Trust, St Thomas' Hospital

    London, SE1 7EH

    Recruiting

  • Royal Victoria Infirmary

    Newcastle upon Tyne, England, NE1 4LP

    Recruiting

Other trials in United Kingdom

Canada3 sites, 3 recruiting

  • Stollery Children's Hospital

    Edmonton, Alberta, T6G 2B7

    Recruiting

  • Hamilton Health Sciences - McMaster University Medical Centre

    Hamilton, Ontario, L8N 3Z5

    Recruiting

  • Hamilton Health Sciences - McMaster University Medical Centre

    Hamilton, Ontario, L8N3Z5

    Recruiting

Other trials in Canada

South Africa3 sites

  • Worthwhile Clinical Trials

    Benoni, Gauteng, 1500

    Active, not recruiting

  • Charlotte Maxeke Johannesburg Academic Hospital

    Johannesburg, Gauteng, 2193

    Active, not recruiting

  • WITS Health Consortium

    Johannesburg, Gauteng, 2193

    Active, not recruiting

Other trials in South Africa

South Korea3 sites, 3 recruiting

  • Kyungpook National University Hospital

    Daegu, Taegu-kwangyǒkshi, 41944

    Recruiting

  • Kyung Hee University Hospital at Gangdong

    Seoul, Seoul-teukbyeolsi [seoul], 05278

    Recruiting

  • Severance Hospital, Yonsei University Health System

    Seoul, Seoul-teukbyeolsi[seoul], 03722

    Recruiting

Other trials in South Korea

Taiwan3 sites, 3 recruiting

  • ChangHua Christian Hospital

    Changhua, Changhua County, 500

    Recruiting

  • Taichung Veterans General Hospital

    Taichung, 407219

    Recruiting

  • National Taiwan University Hospital

    Taipei, 100

    Not yet recruiting

Other trials in Taiwan

Slovakia2 sites, 2 recruiting

  • Detska fakultna nemocnica Kosice

    Košice, 040 11

    Recruiting

  • Univerzitna nemocnica Martin

    Martin, 036 59

    Recruiting

Other trials in Slovakia

Argentina1 site, 1 recruiting

  • Arbesu Hematología

    Mendoza, M5501

    Recruiting

Other trials in Argentina

Australia1 site, 1 recruiting

  • Royal Children's Hospital

    Melbourne, Victoria, 3052

    Recruiting

Other trials in Australia

Brazil1 site, 1 recruiting

  • HEMOES

    Vitória, Espírito Santo, 29047-105

    Recruiting

Other trials in Brazil

Croatia1 site, 1 recruiting

  • Klinicki bolnicki centar Zagreb

    Zagreb, 10000

    Recruiting

Other trials in Croatia

Denmark1 site, 1 recruiting

  • Aarhus Universitetshospital, Skejby

    Aarhus, Central Jutland, 8200

    Recruiting

Other trials in Denmark

France1 site, 1 recruiting

  • Hôpital Universitaire Necker Enfants Malades

    Paris, 75015

    Recruiting

Other trials in France

Israel1 site, 1 recruiting

  • Sheba Medical Center

    Ramat Gan, Central District, 5262100

    Recruiting

Other trials in Israel

Mexico1 site, 1 recruiting

  • Centro Multidisciplinario para el Desarrollo Especializado de la Investigacion Clinica en Yucatán S.

    Mérida, Yucatán, 97130

    Recruiting

Other trials in Mexico

Oman1 site, 1 recruiting

  • Sultan Qaboos University Hospital

    Muscat, 123

    Recruiting

Other trials in Oman

About this study

Official title: AN OPEN-LABEL EXTENSION STUDY TO EVALUATE THE LONG-TERM SAFETY, TOLERABILITY, AND EFFICACY OF MARSTACIMAB PROPHYLAXIS IN SEVERE (COAGULATION FACTOR ACTIVITY <1%) HEMOPHILIA A PARTICIPANTS WITH OR WITHOUT INHIBITORS OR MODERATELY SEVERE TO SEVERE HEMOPHILIA B PARTICIPANTS (COAGULATION FACTOR ACTIVITY ≤2%) WITH OR WITHOUT INHIBITORS

Study B7841007 is an open-label extension study to assess the long-term safety, tolerability, and efficacy of prophylaxis treatment with marstacimab in participants who did not require "Early Termination" from the Phase 3 Study B7841005 and from the Phase 3 Study B7841008.

Study B7841005: approximately 145 adolescent and adult participants 12 to <75 years of age with severe hemophilia A or moderately severe to severe hemophilia B (defined as FVIII activity <1% or FIX activity ≤2%, respectively) with or without inhibitors are expected to be enrolled in Study B7841005 during which they will receive prophylaxis (defined as treatment by SC injection of marstacimab).

Read more

Study B7841008: this is an ongoing Phase 3, open-label study in pediatric participants <18 years of age with severe hemophilia A (FVIII Coagulation Factor Activity <1%) or moderately severe to severe hemophilia B (FIX Coagulation Factor Activity ≤2%). A sequential approach will be used in enrolling at least 100 pediatric participants, at least 20 of which will be aged ≥12 to <18 years and at least 80 participants will be aged ≥1 to <12 years. At the start of study B7841008, the dosing and data available in adolescent and adult participants in Study B7841005 supported the initiation of B7841008 study in participants aged ≥12 to <18 years. Subsequently, additional safety and efficacy data from adolescent participants in Study B7841005 became available for benefit/risk assessment in support of dosing participants aged ≥6 to <12 years. Based on the positive benefit/risk assessment conducted by both internal Pfizer review and eDMC review, dosing of the ≥6 to <12 years age group was initiated in June 2023 in B7841008 Study. Data from participants ≥6 years from B7841008 Study and Study B7841005 will support the dosing of participants aged ≥1 to <6 years.

All participants will be provided the prefilled pen (PFP) for administration of marstacimab in the study. Use of the prefilled syringe (PFS) will be permitted at the investigator's discretion for those participants who have difficulty with administration of the PFP. Additionally, participants will be provided the PFS for use in this study in countries where the PFS is anticipated to be the only presentation available commercially. An optional, open-label, single arm, substudy using the PFP was completed in the first 23 participants rolled over from Study B7841005 who agreed to participate in the substudy.

Being tested
PF-06741086
Keywords
Factor VIII Inhibitor, Factor IX Inhibitor, PF-06741086, Marstacimab, Anti-TFPI
Medical subject headings
Hemophilia A, Hemophilia B

What participants receive

What participants receive. In a randomised study each person is assigned to one group by chance.

  • PF-06741086Drug

    Also called marstacimab

    For participants aged ≥12 years 300 milligrams(mg) subcutaneous (sc) loading dose followed by 150 mg sq once weekly (qw). 300 mg sc qw is prescribed for participants who meet dose escalation criteria.

    For participants aged ≥6 to <12 years is marstacimab 150 mg SC for initial loading dose followed by 75 mg SC QW. 150 mg sc qw is prescribed for participants who meet dose escalation criteria.

Study groups in NCT05145127
Study groupRoleWhat they receive
PF-06741086ExperimentalFor participants aged ≥12 years 300 milligrams(mg) subcutaneous (sc) loading dose followed by 150 mg sq once weekly (qw). 300 mg sc qw is prescribed for participants who meet dose escalation criteria. For participants aged ≥6 to <12 years is marstacimab 150 mg SC for initial loading dose followed by 75 mg SC QW. 150 mg sc qw is prescribed for participants who meet dose escalation criteria.
Receives: Drug: PF-06741086

What is being measured

The primary outcome is the main question the study is designed to answer.

  1. Number of subject reporting Adverse Events

    Measured: Baseline up to 7 years

  2. Number of subjects reporting Serious Adverse Events

    Measured: Baseline up to 7 years

  3. Incidence and severity of thrombotic events

    Measured: Baseline up to 7 years

  4. Incidence and severity of thrombotic microangiopathy

    Measured: Baseline up to 7 years

  5. Number of subjects reporting Disseminated intravascular coagulalopathy/consumption coagulopathy

    Measured: Baseline up to 7 years

  6. Incidence of clinically significant persistent NAb against marstacimab

    Measured: Baseline up to 7 years

  7. Incidence and severity of injection site reaction

    Measured: Baseline up to 7 years

  8. Clinically significant changes in vital signs from baseline

    Measured: Baseline up to 7 years

  9. Incidence of clinically significant laboratory value abnormalities

    Measured: Baseline up to 7 years

  10. Incidence of severe hypersensitivity and anaphylactic reactions

    Measured: Baseline up to 7 years

Secondary outcomes (13)

  1. Annualized rate of bleeding episodes

    Derived for each subject for each treatment period by using the following formula: ABR = number of bleeds requiring treatments/ (days on treatment period / 365.25)

    Measured: Baseline up to 7 years

  2. Total coagulation factor product consumption

    Measured: Baseline up to 7 years

  3. Incidence of joint bleeds

    Measured: Baseline up to 7 years

  4. Incidence of spontaneous bleeds

    Measured: Baseline up to 7 years

  5. Incidence of target joint bleeds

    Measured: Baseline up to 7 years

  6. Incidence of total bleeds (treated and untreated)

    Measured: Baseline up to 7 year

  7. Change in joints measured by the HJHS

    Change in joints as measured by the HJHS for participants ≥4 years of age

    Measured: Baseline up to 7 years

  8. Change in number of target joints per subject from baseline

    Measured: Baseline up to 7 years

  9. Changes in Health Utilities Measure questionnaire data

    Measured: Baseline up to 7 years

  10. Changes in Haem-A-QoL questionnaire data for participants ≥17 years of age

    Measured: Baseline up to 7 years

  11. Changes in Haemo-QoL questionnaire data

    Haemo-QoL CII (Ages 8 to <12 years), Haemo-QoL (Ages 12 to <17),

    Measured: Baseline up to 7 years

  12. Total bypass product consumption

    Measured: Baseline up to 7 years

  13. Changes in EQ-5D questionnaire data

    EQ-5D-Y Proxy (Ages ≥ 4 to ≤ 6 years), EQ-5D-Y Self (Ages ≥ 7 to ≤ 11 years), EQ-5D-5L (Ages ≥12)

    Measured: Baseline up to 7 years

Timeline

From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.

  1. First posted6 Dec 2021
  2. Study start17 Nov 2021
  3. Primary completion31 Jul 2030 (estimated)
  4. Study completion31 Jul 2030 (estimated)

Resources

More details

For doctors and researchers: how the study is designed, who runs it, and its registry IDs.

Study design
Study type
Interventional
Phase
Phase 3
Primary purpose
Treatment
Allocation
Not applicable
Intervention model
Single group
Masking
None (open label)
Enrolment
245 participants (estimated)
IDs, dates and publications
ClinicalTrials.gov ID
NCT05145127
Sponsor's protocol ID
B7841007
Other IDs
PHASE 3 ANTI-TFPI OLE, 2022-500470-33-00
Status last verified
Oct 2026
First submitted
11 Nov 2021
Last updated
26 Oct 2026
Results posted
No
Data monitoring committee
Yes
FDA-regulated drug
Yes
FDA-regulated device
No
Individual data sharing
Yes: Pfizer will provide access to individual de-identified participant data and related study documents (e.g. protocol, Statistical Analysis Plan (SAP), Clinical Study Report (CSR)) upon request from qualified researchers, and subject to certain criteria, conditions, and exceptions. Further details on Pfizer's data sharing criteria and process for requesting access can be found at: https://www.pfizer.com/science/clinical\_trials/trial\_data\_and\_results/data\_requests.

Questions about this trial

What is this clinical trial studying?

A Phase 3 study testing PF-06741086 in people with Hemophilia A and Hemophilia B, run by Pfizer at 78 sites in 24 countries.

The full registered description is in the About this study section and the official record.

Who may be eligible to take part?

The sponsor lists 3 inclusion and 9 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.

Is this clinical trial currently recruiting?

The record says: looking for participants now, as of the sponsor's last update on 26 Oct 2026. Status can change between updates, so confirm with the study contact before making plans.

Where is the study taking place?

The record lists 78 sites in Turkey (Türkiye), China, Japan, United States, Hong Kong and 19 more countries. Whether a site is taking part right now should be confirmed with that site. See every site.

What are the possible benefits and risks?

They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.

What does this phase mean?

Phase 3 studies compare the treatment with the current standard treatment or a placebo in a large group, to confirm how well it works and watch for side effects.

Not every study follows the same path, and some studies (observational studies, device studies) have no phase.

Are results available for this study?

This study is still under way. Results are not available in the source record yet.

How can a doctor refer a patient or contact the research team?

Contact Pfizer CT.gov Call Center (1-800-718-1021, ClinicalTrials.gov_Inquiries@pfizer.com), or a site near the patient. AzTrials does not enrol participants or take referrals.

What does the primary outcome measure?

Number of subject reporting Adverse Events (time frame: Baseline up to 7 years). The study lists 10 primary outcomes in all. It is what the study was designed to measure, not a finding.

Where can I read the original study information?

On the ClinicalTrials.gov record for NCT05145127.

Does a listing mean the treatment is approved or proven to work?

No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.

How often is this information updated?

AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 26 Oct 2026.

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