Essentials of Laboratory Issues in the Patients with Emicizumab Therapy

The recent development of emicizumab (Hemlibra, previously referred to as ACE910; Hoffman-La Roche) extends treatment options for hemophilia A patients, with and without anti-factor VIII (FVIII) inhibitors, and provides an alternative to FVIII replacement therapy for patients with severe hemophilia A. The novel nature and mode of action of the molecule have implications for laboratory testing of coagulation parameters in patients receiving this treatment.Emicizumab is an engineered IgG4 bispecific antibody that binds both activated factor IX (FIXa) and its substrate factor X (FX).This interaction colocalizes components of the intrinsic tenase complex and improves the ability of FIXa to activate FX in the absence of activated FVIII (FVIIIa).Therefore, FVIII is a mimetic because it acts as a cofactor for FIXa activation of FX.In a recently published study, information regarding the influence of emicizumab on certain coagulation tests, measurement of FVIII in the presence of emicizumab, and measurement of emicizumab levels was reported.In the present review, the issues associated with laboratory testing in hemophilia A patients receiving emicizumab were summarized.