The study aims to determine the hemostatic effect of different Factor IX (FIX) concentrates when added to the plasma of patients on emicizumab prophylaxis and compare it to the hemostatic effect obtained with the addition of bypassing agents (activated prothrombin complex aPCC, and recombinant VIIa rVIIA, recombinant porcine FVIII).~The investigators will study the hemostatic effect using Thrombin Generation assay (CAT) in the presence of different concentrations of FIX concentrates. The investigators will compare the hemostatic effect of added FIX to the effect of added bypassing agents (activated prothrombin complex aPCC, and recombinant VIIa rVIIA, recombinant porcine FVIII)~Plasma will be collected from patients with hemophilia A and inhibitors treated with Emicizumab, a group of plasma samples will be spiked with different concentrations of Factor IX. Thrombin generation profiles will be obtained using CAT.~Another group of plasma samples will be spiked with different concentrations of by passing agents (activated prothrombin complex aPCC, and recombinant VIIa rVIIA, recombinant porcine FVIII). Thrombin generation profiles will be obtained using CAT.
This trial will enroll patients with severe hemophilia A. Experiments will be run in vitro by spiking patients' blood with different molecules (currently used and theoretically proposed as adjunctive therapy to emicizumab), therefore no more than minimal direct risk to patients is expected. This is a pilot preclinical study.