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

To join this study, you must have already taken part in one of the earlier marstacimab studies (B7841005 or B7841008) and completed it without having to stop early. You also need to be able to attend all the scheduled appointments and follow the study rules. Your body weight must meet a certain minimum, which would have been checked in the earlier studies.

There are several reasons why someone might not be able to join. For example, if you have a history of certain heart or blood clot problems, or kidney issues. You also can't join if you have unstable liver problems or if you have HIV and your condition is getting worse. If you're planning to have surgery during the study or are taking certain other medications (like strong medicines that affect your immune system or other haemophilia treatments like FVIII or FIX), you unfortunately won't be able to take part. Also, if you're involved in another study testing a new medicine or vaccine, you can't join this one.

This study is open to males aged between 1 and 74 years old. The researchers want to make sure everyone in the study is as safe as possible, which is why these checks are in place.

If you take part in this study, you'll continue to receive your marstacimab medicine as an injection, using either a special pen or a syringe. You'll have regular visits to the clinic so the study team can check on your health, assess how well the medicine is working, and look for any side effects. You'll also have blood tests and other assessments during these visits. The study involves long-term follow-up to see how you respond to the treatment over time. The team will guide you on how to give yourself the injections and what to expect during your appointments. The total duration of your participation will depend on how long the study continues, as it's an extension study.