A new era of treatment for patients with haemophilia A?

Treatment and prevention of bleeding episodes in patients with severe haemophilia A require frequent intravenous injection of factor VIII. Inhibitory antibodies against factor VIII occur in approximately 30 % of these patients during the first exposure days and immune tolerance induction to eradicate the inhibitor is challenging. Prevention of bleeds in patients with haemophilia A and inhibitors is less effective and there is ongoing research for alternative treatment options. A promising approach in 2016 is the development of emicizumab (ACE910), a bi-specific IgG antibody to factor IXa and factor X, that mimics the cofactor function of factor VIII. Due to the different structure of this antibody it cannot be neutralized by factor VIII inhibitors and has the possibility to achieve haemostasis in patients with severe haemophilia A with and without inhibitors. First studies in healthy volunteers and in patients showed a shortened activated partial thromboplastin time and increased peak height of thrombin generation in a dose-dependent manner. The half-life of the drug was 4 to 5 weeks. There were no clinical signs of thrombosis and no laboratory abnormalities indicating hypercoagulability. In a first study with 18 patients with severe haemophilia A with and without inhibitors a remarkable reduction in the annualised bleeding rate occurred. Safety of the drug has to be proven in ongoing research. Mimicking the cofactor activity of factor VIII by a bispecific antibody for the treatment of severe haemophilia A is so far safe and seems to be effective and is one highlight in haemostasis 2016.