Time course of the ratio of FVIII:C to FVIII:b after the last dose of emicizumab. This ratio was calculated from FVIII activity measured with the 1-stage clotting assay (which is very sensitive to trace amounts of emicizumab; FVIII:C) and the chromogenic assay using bovine reagents (which is insensitive to emicizumab; FVIII:b). n = 12; x-axis, days after the last dose of emicizumab.