Susoctocog alfa

Factor VIII circulates in the plasma as a hemostatically active protein complex that consists of factor VIII and a large carrier protein von Willebrand factor via a non-covalent binding interaction. This protein complex remains inactive until the coagulation cascade is activated which in turn activates factor VIII to be released from factor VIII/von Willebrand factor complex. Activated factor VIII acts as a cofactor for factor IX-mediated conversion of factor X to activated factor X. Activated factor X is critical in converting prothrombin into thrombin and sequentially, thrombin converts fibrinogen to fibrin for the formation of a blood clot.

Acquired haemophilia is a rare bleeding disorder where patients with normal Factor VIII genes spontaneously develop inhibitory autoantibodies directed against Factor VIII. These autoantibodies are IgG1 and IgG4 autoantibodies that bind to the A2, A3 and C2 domains of the FVIII molecules to inactivate them. The autoantibodies neutralize circulating human factor VIII and create a functional deficiency of this procoagulant protein. Susoctocog alfa serves to temporarily restore the inhibited endogenous Factor VIII for effective hemostasis. Circulating inhibitory autoantibodies have minimal or no cross-reactivity against susoctocog alfa.