Take a new preventive injection for severe bleeding disorders

Take a new preventive injection for severe bleeding disorders | stella

What is this trial?

This is a follow-up study for people with severe hemophilia A or moderately severe to severe hemophilia B who have completed an earlier trial of marstacimab. The medication is given as a weekly injection under the skin to help prevent bleeding episodes. The study will track how safe and effective this treatment is over a longer period of time.

Hemophilia is a lifelong condition, and people need treatments they can use safely for years or even decades. This medication represents a new approach to preventing bleeds, but doctors need to understand how well it works and whether it remains safe when people use it long-term.

Do you qualify?

You likely qualify if…

you have severe hemophilia A (factor activity less than 1%) or moderately severe to severe hemophilia B (factor activity 2% or less), with or without inhibitors
you successfully completed one of the earlier Pfizer hemophilia studies without being forced to stop early
you are at least 1 year old (younger participants may join based on safety data from older participants)
you weigh at least the minimum body weight set by the earlier study you completed
you are willing to attend all study visits, take the medication as prescribed, and complete all blood tests and study procedures

You likely don't qualify if…

you have a history of blood clots, heart disease, or severe circulation problems (unless they were caused by a catheter)
you have kidney disease with severely reduced kidney function
you are planning to have surgery during the study period
you have unstable liver disease that your doctor thinks makes the study unsafe for you
you are taking immune-modifying medicines (such as IVIG or certain steroids) or planning immune tolerance induction therapy during the study

What participation looks like

You will continue to receive the same medication you started in the earlier trial, given as a weekly injection that you or a caregiver can administer at home using a prefilled pen. You will attend regular clinic visits for blood tests and check-ins with the study team to monitor how you're doing and whether you're having fewer bleeding episodes. The study will continue for as long as you benefit from the treatment and the medication remains safe, with your doctor adjusting your dose if needed based on how well it works for you.

AI-generated summary from trial data · Jul 2, 2026 · Not medical advice

Long-term safety study of a new bleeding disorder preventive treatment

What is this trial?

Do you qualify?

What participation looks like

Trial locations(75 sites)