Emicizumab in acquired hemophilia A: pros and cons of a new approach to the prevention and treatment of bleeding

Emicizumab, a monoclonal bispecific antibody that mimics the function of activated factor VIII (FVIII), is currently licensed for prophylactic use in patients with congenital hemophilia A with and without inhibitors. Acquired hemophilia A (AHA) is a very rare bleeding disorder caused by the development of autoantibodies that inhibit FVIII activity in plasma; males and females are equally affected. Therapeutic options for patients with AHA currently include eradication of the inhibitor with immunosuppressive treatments and management of acute bleeding with bypassing agents or recombinant porcine FVIII. More recently, several reports described the off-label use of emicizumab in patients with AHA and a phase III study is ongoing in Japan. The aims of this review are to describe the 73 reported cases, and to highlight the advantages and disadvantages of this novel approach to the prevention and treatment of bleeding in AHA.