At a glance
- What the study gets you
- Access to the study treatment being tested
- Type of study
- Interventional (receives a drug or procedure)
- Time in hospital
- In-person visits at study sites — visit count not specified by the sponsor
- Drug or intervention
- PF-06741086 (drug)
- How long the study runs
- Study runs about 104 months (dates as stated)
- About the drug or intervention
- PF-06741086 — drug: For participants aged ≥12 years 300 milligrams(mg) subcutaneous (sc) loading dose followed by 150 mg sq once weekly (qw).
- Patient visit burden
- Not specified by the sponsor
In plain English
This is an extension study of a medicine called marstacimab for people with haemophilia A or haemophilia B, with or without inhibitors. It is open to people who have already finished an earlier (parent) study of the same medicine. An open-label study means everyone receives the study medicine, with no dummy (placebo) treatment. It is run by Pfizer.
Who can take part
- You must be at least a minimum body weight, as set by the earlier (parent) studies
- You are willing and able to attend all planned visits and follow the study plan, including blood tests and other checks
- You finished taking part in one of the earlier (parent) studies without stopping early
Who may not be able to
- Current or past coronary artery disease (heart disease), blood clots in veins or arteries that were Grade 3 or worse in severity, or reduced blood supply to parts of the body (except clots linked to a catheter)
- Poor kidney function (a measure called estimated glomerular filtration rate, or eGFR, below 30)
- Surgery already planned during the study period
- Unstable liver function, judged by the study doctor from your symptoms and latest blood test results
- If you have HIV, worsening illness that the study doctor thinks makes the study unsuitable for you
- Regular treatment with drugs that change the immune system, such as immunoglobulin given by drip (IVIG), routine steroid tablets or injections, or rituximab
- Ongoing or planned immune tolerance induction, or regular preventive treatment with factor VIII or factor IX replacements during the study
- Taking part in another study of an experimental drug or vaccine within 30 days or 5 half-lives before or during this study (the parent studies do not count)
- Being study staff at the site, a Pfizer employee working on the study, or a family member of either
What taking part involves
- • Not stated — ask the trial team
Time commitment: Not stated — ask the trial team about how many visits there are, how long the study lasts, and what taking part involves.
Plain-English summary (AI-generated) from registry data. Not eligibility advice — only the trial team can confirm whether you can take part. Use the eligibility checker to see how your health profile matches this trial.
- Type of study
- Testing a treatment
- Ages
- 1 Year to 74 Years
- Who
- Male
- Number of participants
- 245
- Started
- 2021-11-17
- Last checked
- 2026-06
Plain English Summary
What is this study?
- • Testing a new treatment for hemophilia a
- • Phase3 - 245 participants
- • 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
Who can take part?
- • Ages 1 Year to 74 Years
- • Diagnosed with hemophilia a
- • Male only
Where?
- • Newcastle upon Tyne - Royal Victoria Infirmary
- • London - Guy's & St Thomas' NHS Foundation Trust
- • London - Guy's & St Thomas' NHS Foundation Trust, St Thomas' Hospital
This is a simplified summary. Always discuss with your doctor before making any decisions.
About This Trial
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). 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.
How this trial compares with your answers
Answer 2 more questions to improve match
What we know so far
Still need:
- • Tell us your age for better matching
- • Tell us your sex for better matching
Preliminary match based on your answers. Full eligibility requires on-site assessment including medical history, physical exam, and lab tests. This does not guarantee enrolment.
Eligibility at a Glance
Key info
- Age: 1 Year - 74 Years
- Who can join: Male only
Biomarkers mentioned
Treatment history
Treatments you must have had:
- ✓ "Early Termination"
What the study is looking for
- ✓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...
- ✓Participants have successfully completed participation in parent studies, defined as did not require "Early Termination"
Who cannot take part
- ✗Previous or current treatment for or history of coronary artery disease, venous or arterial thrombosis (CTCAE Grade...
- ✗Abnormal kidney function as defined by eGFR \<30 mL.min/1.73 m(2)
- ✗Known planned surgical procedure during the planned study period
- ✗Regular, concomitant therapy with immunomodulatory drugs (eg, IVIG, and routine systemic corticosteroids, rituximab)
- ✗Ongoing or planned use of immune tolerance induction or prophylaxis with FVIII or FIX replacement during the study
See the full criteria
Where Is This Study? (3 UK sites)
Royal Victoria Infirmary
Newcastle upon Tyne NE1 4LP, United Kingdom
Guy's & St Thomas' NHS Foundation Trust
London SE1 9RT, United Kingdom
Guy's & St Thomas' NHS Foundation Trust, St Thomas' Hospital
London SE1 7EH, United Kingdom
How to Get in Touch
Pfizer CT.gov Call Center
Sponsor contactCONTACT