At the time of designation, medicines containing factor VIII were authorised in the EU for the treatment of haemophilia A, to replace the missing protein. However, factor VIII medicines did not work in some patients with haemophilia A because the immune system (the body's natural defences) can produce 'inhibitors' (antibodies) against factor VIII which stop the factor VIII medicine from working. In these cases, other treatments needed to be used, such as factor VIIa (the activated form of factor VII, another protein involved in blood clotting), either alone or as part of a combination treatment.

The sponsor has provided sufficient information to show that the medicine might be of significant benefit for patients with haemophilia A because laboratory studies indicate that it can restore normal levels of factor VIII circulating in the blood and reduce blood loss after a single dose of the medicine. As a result, patients may not need or may need less frequent treatment with factor VIII medicines.

This assumption will need to be confirmed at the time of marketing authorisation, in order to maintain the orphan status.