Genentech, a member of the global pharmaceutical giant Roche Group, announced that that the U.S. FDA has awarded breakthrough therapy designation (BTD) to its ACE910 for the prophylactic treatment of people who are 12 years or older with hemophilia A with factor VIII inhibitors.  Hemophilia A is a rare hereditary bleeding disorder caused by mutation in the gene encoding coagulation factor VIII on chromosome X.  Depending on the nature of the mutation, the severity of symptoms varies.  Less than 1% of patients have the severe form and they are susceptible to uncontrolled or difficult to control bleeding which can lead to permanent disability.  Currently, hemophilia A patients may undergo infusions of replacement clotting factor to reduce the risk of dangerous bleeding, and some of them can develop inhibitors that make replacement ineffective.  ACE910 is an investigational bispecific monoclonal antibody capable of binding factor IXa and X simultaneously.  It functions as the cofactor of factor VIII and is designed to promote blood coagulation in hemophilia A patients, even when they have developed inhibitors to factor VIII.  The BTD was granted based on promising results of a Phase I study of ACE910 in patients with severe hemophilia A.