Although bispecific mAbs, such as the anti-blood-coagulation factor IX and anti-blood-coagulation factor X bispecific mAb emicizumab (Hemlibra®) [57] developed and launched for hemophilia A in 2018 in Japan by Chugai, have been clinically approved, multispecific mAbs (more than trispecific) have not yet been approved. The gene discussed is F9; the disease is hemophilia A.