Model for effect of bypassing agents with emicizumab. (A) Emicizumab mimics the function of coagulation FVIIIa in hemostasis. With repeated doses of activated prothrombin complex concentrates, (B) intrinsic, extrinsic, and common pathway procoagulant proteins can accumulate, resulting in exaggerated thrombin generation and fibrin formation. Recombinant FVIIa, because of its short half-life, is unlikely to accumulate and (C) drives increased thrombin generation only through the extrinsic pathway.