NovoSeven: mode of action and use in acquired haemophilia.

Recombinant activated factor VII (rFVIIa, 'NovoSeven') is indicated for the treatment of spontaneous and surgical bleeding in patients with haemophilia A or B with antibodies to factors VIII or IX (FVIII or FIX) worldwide, and in patients with acquired haemophilia in Europe. In vitro cell models have demonstrated that rFVIIa can bind to activated platelets and generate small amounts of Fxa, independent of the presence of tissue factor. The amount of platelet-surface Fxa formed increases with rising concentrations of FVIIa and, at levels of rFVII a that are effective in patients, sufficient platelet surface Fxa is generated partially to restore platelet surface thrombin generation. Acquired haemophilia is a rare but potentially life-threatening condition, caused by the autoimmune reduction of clotting factor levels as a result of the spontaneous development of auto-antibodies directed against the deficient factor. Bleeding into the skin or muscles is common in acquired haemophilia and the associated mortality rate is approximately 20%. rFVIIa has reported efficacy in the treatment of major bleeding episodes in patients with acquired haemophilia, which may be explained by its distinct mechanism of action that induces haemostasis at the site of injury, independent of the presence of FVIII or FIX. Also, the localisation of the action of rFVIIa at the site of injury may explain why it is well tolerated in these patients.