Hemlibra® works by replacing the function of factor VIII, rather than replacing the missing clotting factor VIII directly. It can be used to either prevent or reduce the frequency of bleeding episodes in people with hemophilia A. This treatment product can be given by injection under the skin. Patients who use Hemlibra® for prophylaxis and use clotting factor concentrates to treat breakthrough bleeds can still develop an . Traditional laboratory inhibitor testing methods do not work when testing for inhibitors in patients on Hemlibra®; as such, a specialized testing method called the chromogenic Bethesda assay is needed., Treatment overview The standard way to treat both hemophilia A and B is to replace the missing blood clotting factor so that the blood can clot properly. One way to do this is by infusing (injecting into a vein) commercially prepared clotting factor concentrates. For hemophilia A, another treatment method is a non-factor product that stands in for, or replaces the function of, the missing , Typically, factor mimetic or rebalancing therapies are given by injection on a set schedule. Many of the newer non-factor products are good options for people who develop a clotting factor antibody, called an inhibitor, that makes factor replacement therapy more challenging..