For the first time, the present invention provides antibodies that enhance the generation of activated blood coagulation factor VIII. The antibodies enhance the cleavage of blood coagulation factor VIII at the Arg of position 372 and suppress the cleavage at the Arg of position 336 by recognizing and binding to the A2 domain of blood coagulation Factor VIII. Such antibodies are expected to be useful in preventing or treating diseases that develop or progress due to decrease or loss of the blood coagulation factor VIII activity, for example, hemophilia A, acquired hemophilia, and von Willebrands disease.
