HEMLIBRA is a drug used to prevent or reduce frequency of bleeding episodes in children and adult patients with hemophilia A. It is to be used in patients who have developed an immune response known as a FVIII inhibitor or antibody. Hemophilia A is an inherited blood-clotting disorder that affects primarily males. It is caused by missing or abnormal clotting protein (Factor VIII) making it more difficult to stop bleeding. Source 9x.