LAUSR

Emicizumab reduces bleeding events in patients with severe hemophilia A (HA). The coagulation potential of emicizumab at a clinical dose appears to correspond to about 15 IU/dL of factor VIII activity (FVIII:C), the equivalent of converting from a severe to mild phenotype. However, the clinical and laboratory characteristics of HA patients receiving emicizumab (Emi-PwHA) compared with patients with mild HA (PwMHA) remain to be determined. We reviewed clinical data from Emi-PwHA (n = 63) and PwMHA (n = 15) and evaluated comprehensive coagulation function using Ca2+-triggered rotational thromboelastometry (ROTEM) and ellagic acid/tissue factor-triggered clot waveform analysis (modified CWA). The median FVIII:C in PwMHA was 13.0 (IQR 8.5–17.0) IU/dL. Bleeding patterns in both groups were similar and classified into three categories: (1) spontaneous bleeding, post-traumatic, (2) bleeding within 1–2 days, and (3) delayed bleeding after 1–2 weeks. The coagulation potential in Emi-PwHA with and without breakthrough bleeds was comparable. Furthermore, coagulation function in Emi-PwHA was equivalent to PwMHA, although time between treatment and hospitalization for breakthrough bleeds in PwMHA appeared to be longer than those in Emi-PwHA. The coagulation potential and bleeding patterns appeared to be similar in Emi-PwHA and PwMHA, indicating that emicizumab-driven coagulation potential reflected mild HA.