A Study to Learn About the Study Medicine (Called Marstacimab) in People With Hemophilia A or B

September 29, 2026 updated by: Pfizer

MARSTACIMAB REAL-WORLD EVALUATION OF EFFECTIVENESS IN HEMOPHILIA: A UNITED STATES MEDICAL RECORD AND PARTICIPANT REPORTED OUTCOME STUDY (MARVL-US)

The purpose of this non-interventional, observational, real-world study is to find out what are the real-world experiences of people living with hemophilia A or B[OK1.1] who start the study medicine (called marstacimab) in routine clinical practice. Hemophilia is a rare genetic condition where the blood does not clot normally, meaning people bleed longer than usual after an injury.

This study is seeking participants who are living with hemophilia A or B and:

  • Have a medical record documenting hemophilia A or hemophilia B. A hematologist must have confirmed the diagnosis before they join the study.
  • Are under current treatment with marstacimab or have a prescription to start the treatment with marstacimab
  • Are 6 years of age or older and the recipient of medical care in the United States All participants in this study will receive their usual treatment for hemophilia A or hemophilia B Participants will take part in this study for 1 year. During this time, they will complete up to six surveys. These surveys will be given between enrollment and about one year after marstacimab is started.

Some participants in the study may be asked to take part in interviews. During these interviews they will be asked about their experience with hemophilia or marstacimab.

The study will provide information about how well the marstacimab treatment works. It will also assess treatment burden, and treatment preferences. This information will help to determine its benefit compared to existing treatment options. It will also help doctors make treatment decisions and optimize hemophilia care.

Study Overview

Status

Status

Indicates the current recruitment status or the expanded access status.
Not yet recruiting

Conditions

Conditions

The disease, disorder, syndrome, illness, or injury that is being studied. On ClinicalTrials.gov, conditions may also include other health-related issues, such as lifespan, quality of life, and health risks.

Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.

Study Type

Study Type

Describes the nature of a clinical study. Study types include interventional studies (also called clinical trials), observational studies (including patient registries), and expanded access.
Observational

Enrollment (Estimated)

Enrollment

The number of participants in a clinical study. The "anticipated" enrollment is the target number of participants that the researchers need for the study.
100

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Contact

The name and contact information for the person who can answer enrollment questions for a clinical study. Each location where the study is being conducted may also have a specific contact, who may be better able to answer those questions.

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Eligibility Criteria

The key requirements that people who want to participate in a clinical study must meet or the characteristics they must have. Eligibility criteria consist of both inclusion criteria (which are required for a person to participate in the study) and exclusion criteria (which prevent a person from participating). Types of eligibility criteria include whether a study accepts healthy volunteers, has age or age group requirements, or is limited by sex.

Ages Eligible for Study

6 years and older (Child, Adult, Older Adult)

Accepts Healthy Volunteers

No

Genders Eligible for Study

All

Sampling Method

Probability Sample

Study Population

This observational study is designed as a virtual-site study to take place in the United States (US), and will collect real-world data from participants' documented routine interactions with the healthcare system, surveys, and interviews. Participants will be recruited from US-based healthcare sites that care for people living with hemophilia, or through digital outreach

Description

Medical record documentation of hematologist-confirmed diagnosis of hereditary factor VIII deficiency disease (Hemophilia A) or hereditary factor IX deficiency disease (Hemophilia B) prior to enrollment

  • Current treatment with marstacimab or documentation of a prescription to initiate marstacimab
  • Aged 6 or older at the time of consenting into the study
  • Receipt of medical care in the United States
  • Evidence of a personally signed and dated informed consent document indicating that the participant (or a legally authorized representative) has been informed of all pertinent aspects of the study ○ If the participant is between the ages of 7 and 17, evidence of a personally signed and dated informed assent indicating that the participant has been informed of and assents to the study

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Observational Models: COHORT
  • Time Perspectives: CROSS_SECTIONAL

Cohorts and Interventions

Group / Cohort

Group / Cohort

A group or subgroup of participants in an observational study that is assessed for biomedical or health outcomes.
Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.
Real World Data participants

This observational study is designed as a virtual-site study to take place in the United States (US), and will collect real-world data from participants' documented routine interactions with the healthcare system, surveys, and interviews. Participants will be recruited from US-based healthcare sites that care for people living with hemophilia, or through digital outreach
Drug: Marstacimab

As provided in real world practice

What is the study measuring?

Primary Outcome Measures

Primary Outcome Measures

In a clinical study's protocol, the planned outcome measure that is the most important for evaluating the effect of an intervention/treatment. Most clinical studies have one primary outcome measure, but some have more than one.
Outcome Measure
Time Frame
Patient reported responses to Marstacimab Patient Preference Survey (MPPS)
Time Frame: Six months after initiating marstacimab
Six months after initiating marstacimab

Secondary Outcome Measures

Secondary Outcome Measures

In a clinical study's protocol, a planned outcome measure that is not as important as the primary outcome measure for evaluating the effect of an intervention but is still of interest. Most clinical studies have more than one secondary outcome measure.
Outcome Measure
Time Frame
Patient reported responses to Hemophilia Treatment Experience Measure (Hemo-TEM)
Time Frame: Month 6 and month 12
Month 6 and month 12
Annualized bleed rates (ABRs)
Time Frame: Baseline through 12 months
Baseline through 12 months
ABRs of all bleeding events
Time Frame: Baseline through 36 months of martstacimab treatment
Baseline through 36 months of martstacimab treatment
Reponses to the hemophilia prophylaxis experience survey, second version (HPES-II)
Time Frame: Baseline to month 3
Baseline to month 3

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Sponsor

The organization or person who initiates the study and who has authority and control over the study.
Pfizer

Investigators

Investigators

A researcher involved in a clinical study. Related terms include site principal investigator, site sub-investigator, study chair, study director, and study principal investigator.
  • Study Director: Pfizer CT.gov Call Center, Pfizer

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

Helpful Links

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Estimated)

Study Start

The actual date on which the first participant was enrolled in a clinical study. The "anticipated" study start date is the date that the researchers think will be the study start date.
October 5, 2026

Primary Completion (Estimated)

Primary Completion

The date on which the last participant in a clinical study was examined or received an intervention to collect final data for the primary outcome measure. Whether the clinical study ended according to the protocol or was terminated does not affect this date. For clinical studies with more than one primary outcome measure with different completion dates, this term refers to the date on which data collection is completed for all the primary outcome measures. The "anticipated" primary completion date is the date that the researchers think will be the primary completion date for the study.
August 30, 2028

Study Completion (Estimated)

Study Completion

The date on which the last participant in a clinical study was examined or received an intervention/treatment to collect final data for the primary outcome measures, secondary outcome measures, and adverse events (that is, the last participant's last visit). The "anticipated" study completion date is the date that the researchers think will be the study completion date.
August 30, 2028

Study Registration Dates

First Submitted

First Submitted

The date on which the study sponsor or investigator first submitted a study record to ClinicalTrials.gov. There is typically a delay of a few days between the first submitted date and the record's availability on ClinicalTrials.gov (the first posted date).
September 29, 2026

First Submitted That Met QC Criteria

First Submitted That Met QC Criteria

The date on which the study sponsor or investigator first submits a study record that is consistent with National Library of Medicine (NLM) quality control (QC) review criteria. The sponsor or investigator may need to revise and submit a study record one or more times before NLM's QC review criteria are met. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
September 29, 2026

First Posted (Actual)

First Posted

The date on which the study record was first available on ClinicalTrials.gov after National Library of Medicine (NLM) quality control (QC) review has concluded. There is typically a delay of a few days between the date the study sponsor or investigator submitted the study record and the first posted date.
October 5, 2026

Study Record Updates

Last Update Posted (Actual)

Last Update Posted

The most recent date on which changes to a study record were made available on ClinicalTrials.gov. There may be a delay between when the changes were submitted to ClinicalTrials.gov by the study's sponsor or investigator (the last update submitted date) and the last update posted date.
October 5, 2026

Last Update Submitted That Met QC Criteria

Last Update Submitted That Met QC Criteria

The most recent date on which the study sponsor or investigator submitted changes to a study record that are consistent with National Library of Medicine (NLM) quality control (QC) review criteria. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
September 29, 2026

Last Verified

Last Verified

The most recent date on which the study sponsor or investigator confirmed the information about a clinical study on ClinicalTrials.gov as accurate and current. If a study with a recruitment status of recruiting; not yet recruiting; or active, not recruiting has not been confirmed within the past 2 years, the study's recruitment status is shown as unknown.
September 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

Other Study ID Numbers

Identifiers or ID numbers other than the NCT number that are assigned to a clinical study by the study's sponsor, funders, or others. These numbers may include unique identifiers from other trial registries and National Institutes of Health grant numbers.
  • B7841028

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

IPD Plan Description

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.

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

Yes

product manufactured in and exported from the U.S.

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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