Discovery and Development of Emicizumab ( HEMLIBRA ® ): A Humanized Bispecific Antibody to Coagulation Factors IXa and X with a Factor VIII Cofactor Activity

In order to meet the unsatisfied needs in the treatment for hemophilia A, which is a congenital disorder caused by deficiency or malfunction of coagulation factor (F) VIII, a researcher in Chugai Pharmaceutical (Japan) was inspired by a novel and unique idea of replacement therapy: the usage of an asymmetric anti-FIXa/FX bispecific immunoglobulin G (IgG) antibody to restore the missing FVIII function. With huge works over 17 years after that, emicizumab (HEMLIBRA®) was launched and has been contributing to improving the quality of life of the patients and their caregivers. In this chapter, the authors described the bumpy road where they have walked toward success as well as the properties and abilities of emicizumab scientifically.