Pfizer’s Hympavzi (marstacimab) has been approved by the UK Medicines and Healthcare products Regulatory Agency (MHRA) to treat haemophilia A or B in adult and paediatric patients.
The drug has been authorised to prevent or reduce bleeding episodes in patients ages 12 years and older who weigh at least 35kg and have severe haemophilia A without factor VIII inhibitors or severe haemophilia B without factor IX inhibitors.
More than 11,800 people were living with haemophilia A or B in the UK in 2023/2024, including 2,700 with severe disease. The genetic blood disorders primarily affect males and are caused by a clotting factor deficiency.
Alongside episodes of excessive and prolonged bleeding, haemophilia patients can experience spontaneous bleeding in their joints and muscles without having had an injury, potentially leading to joint damage.
Pfizer’s Hympavzi, given as a once-weekly subcutaneous injection using a pre-filled pen, works by reducing the amount of TFPI, a naturally occurring protein that prevents blood from clotting too much. This promotes the formation of thrombin, an enzyme critical in blood clotting.
The MHRA’s decision on the drug was supported by results from the late-stage BASIS trial, in which the annualised bleeding rate for treated bleeds was 7.85 for routine factor-based prophylaxis during a six‑month observation period and 5.08 for Hympavzi prophylaxis during a 12‑month active treatment period.
Seema Patel, medical director specialty care, Pfizer UK, described the authorisation as “an important step towards providing eligible patients with a new treatment option”.
Hympavzi is now being evaluated by the National Institute for Health and Care Excellence and Scottish Medicines Consortium for use on the NHS.
“We will continue working with reimbursement agencies across the UK with the aim of making [Hympavzi] available on the NHS,” Patel said.
Haemophilia is a key therapeutic area for Pfizer and the company has a significant presence in the field. In July last year, its haemophilia B gene therapy was granted conditional marketing authorisation by the European Commission to treat adults with severe and moderately severe cases.
In the same month, the company shared positive top-line results from a late-stage study of its investigational haemophilia A gene therapy giroctocogene fitelparvovec, which is being developed as part of a collaboration agreement between Pfizer and Sangamo Therapeutics.
