MHRA (UK) approves Hympavzi (marstacimab) to treat haemophilia A or B in adult and paediatric patients – Pfizer

Hympavzi (marstacimab) from Pfizer 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.