Marstacimab is recommended, within its marketing authorisation, as an option for preventing bleeding episodes caused by severe (factor IX [9] activity less than 1%) haemophilia B (congenital factor 9 deficiency) in people 12 years and over who:
weigh at least 35 kg and
do not have factor 9 inhibitors (anti-factor antibodies).
Marstacimab is only recommended if the company provides it according to the commercial arrangement.
Marstacimab is not recommended, within its marketing authorisation, for preventing bleeding episodes caused by severe (factor VIII [8] activity less than 1%) haemophilia A (congenital factor 8 deficiency) in people 12 years and over who weigh at least 35 kg and do not have factor 8 inhibitors.
This recommendation is not intended to affect treatment with marstacimab that was started in the NHS before this guidance was published. People having treatment outside this may continue without change to the funding arrangements in place for them before this guidance was published, until they and their NHS healthcare professional consider it appropriate to stop. For children or young people, this decision should be made jointly by the healthcare professional, the child or young person, and their parents or carers.
Treatment for preventing bleeding episodes (prophylaxis) is usually factor 8 replacement therapy or emicizumab in severe haemophilia A, and factor 9 replacement therapy in severe haemophilia B.
In severe haemophilia A and B, evidence from a clinical trial shows marstacimab reduces the number of bleeding episodes a person has compared with factor 8 or 9 prophylaxis. In severe haemophilia A, there is no trial directly comparing marstacimab with emicizumab. An indirect comparison suggests marstacimab reduces bleeding episodes by a similar number as emicizumab. But the evidence for this is uncertain.
In severe haemophilia B, the cost-effectiveness evidence for marstacimab showed it is a cost-effective option compared with factor 9. So, marstacimab is recommended for preventing bleeding episodes caused by severe haemophilia B.
In severe haemophilia A, the cost-effectiveness evidence for marstacimab showed it is not a cost-effective option compared with factor 8 and emicizumab. So, marstacimab is not recommended for preventing bleeding episodes caused by severe haemophilia A.