A monoclonal antibody which inhibits the blood clotting factor VII-activating protease and its proenzyme and a blood clotting factor VII-activating protease, stabilized by the addition of said monoclonal antibody, and its proenzyme are described. A suitable monoclonal antibody is produced by hybridoma cell line DSM ACC 2533. The application of the inhibitory, monoclonal antibody in the stabilization of blood clotting preparations and in preparations for reducing the coagulability of the blood is disclosed.
