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

Not yet recruiting

Conditions

Intervention / Treatment

Study Type

Observational

Enrollment (Estimated)

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

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

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
Intervention / Treatment
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

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

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

Pfizer

Investigators

  • 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)

October 5, 2026

Primary Completion (Estimated)

August 30, 2028

Study Completion (Estimated)

August 30, 2028

Study Registration Dates

First Submitted

September 29, 2026

First Submitted That Met QC Criteria

September 29, 2026

First Posted (Actual)

October 5, 2026

Study Record Updates

Last Update Posted (Actual)

October 5, 2026

Last Update Submitted That Met QC Criteria

September 29, 2026

Last Verified

September 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID 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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