Antibodies that functionally substitute for blood coagulation viii factor

Specifically bind to both F.IX / F.IXa and FX, cofactors action of F.VIIIa, i.e., produce various bispecific antibody to replace the function of promoting the FX activation by F.IXa did. From these antibodies, where the shorter to clotting time compared to the time of no antibody addition the antibodies that exhibit more than 50 seconds (A44 / B26), and sharing the L chain of the antibody in the L chain of A44, common although activity is attenuated as compared to the antibody (A44HL-B26HL) before reduction, it revealed that it is possible to common at A44L. Further, the inventors succeeded in producing a highly active multispecific antibodies that substitute for the action of the blood coagulation factor VIII by appropriately shuffling CDR.