NICE approves new weekly treatment option for people with haemophilia B

The first subcutaneous (under the skin) injection for people with the severe form of blood disorder haemophilia B has been approved by NICE. 

NICE's final draft guidance published today recommends marstacimab (also called Hympavzi and made by Pfizer) for treating severe haemophilia B in people 12 years and over. 

The decision comes just weeks after the treatment received its UK licence1. 

Given as a once-weekly injection under the skin using a pre-filled syringe or pen, marstacimab is also the first haemophilia B treatment that works by targeting a protein in the blood clotting process. Marstacimab targets tissue factor pathway inhibitor (TFPI), a protein that prevents blood clotting. By blocking TFPI, marstacimab helps restore blood clotting. 

It will be an option for people with severe haemophilia B who weigh at least 35 kg and do not have antibodies for factor 9 replacement therapy. Factor 9 replacement therapy is given by infusion and is one of only 2 treatments currently available for people with haemophilia B to prevent bleeding episodes2.  

Helen Knight, director of medicines evaluation at NICE, said: “The independent evaluation committee heard from patients who said they would value a new treatment option for severe haemophilia B. They explained that factor 9 replacement therapy to prevent bleeding requires an infusion, sometimes as often as every 2 to 3 days.  

“Marstacimab's clinical and cost-effectiveness compared with current treatment, together with its once-weekly dosing by injection under the skin means it has the potential to significantly improve the quality of life of people with severe haemophilia B. 

“Today's decision, coming just weeks after the treatment received its UK licence, demonstrates our commitment to getting the best care to people fast, while ensuring value for the taxpayer.” 

Haemophilia is a rare, inherited and incurable condition that affects the blood's ability to clot. People with the condition do not have enough clotting factor in their blood (in haemophilia B this is called factor 9), or it isn't working properly. This means they cannot form strong clots and so they bleed for longer than usual. Bleeds can be the result of an injury and, when the condition is severe, bleeding into joints and muscles can happen without any injury. 

Around 255 people live with severe haemophilia B in England, of who an estimated 205 will be eligible for treatment with marstacimab.  

The medicine will be available from the end of June via interim funding through the Innovative Medicines Fund (IMF), until it becomes routinely available on the NHS.

NICE also looked at marstacimab for treating severe haemophilia A. For people with severe haemophilia A, factor 8, emicizumab and efanesoctocog alfa3 are options for preventing bleeding episodes. However, the evidence for marstacimab showed that it is not a cost-effective option in this group.  

Ends 

1 Marstacimab received its uk licence on 22 April 2025. It is licensed for routine prophylaxis of bleeding episodes in patients 12 years of age and older, weighing at least 35 kg, with: severe haemophilia A (congenital factor VIII deficiency, FVIII < 1%) without factor VIII inhibitors or severe haemophilia B (congenital factor IX deficiency, FIX <1%) without factor IX inhibitors. 

2 In June 2024 NICE recommended etranacogene dezaparvovec, the first single infusion gene therapy for adults with severe or moderately severe haemophilia B via a managed access agreement. 

3 In April 2025 NICE recommended once-weekly injection efanesoctocog alfa for people with severe haemophilia A.