Assessment of the Risk of Inhibitor Formation in Previously Treated Patients With Severe Hemophilia A

Inclusion Criteria: * Subjects with severe hemophilia A (\< 2% FVIII:C) * Subjects with no history of FVIII inhibitor antibody formation * Subjects with no measurable inhibitor activity * Subjects with at least 200 EDs with FVIII concentrate in total, including 20 EDs in the previous 6 months * Subjects whose current treatment with any CHO rFVIII product * Subjects with no elective surgery and/or continuous infusion FVIII administration is foreseen during the study * Subjects with normal prothrombin time (PT), partial thromboplastin time (PTT) compatible with FVIII deficiency Exclusion Criteria: * Subjects with any other bleeding disease beside hemophilia A (i,e., von Willebrand's disease) * Subjects who have known intolerance or allergic reactions to constituents of rFVIII-FS or known hypersensitivity to mouse or hamster proteins * Any individual with a past history of severe reaction(s) to FVIII concentrates * Subjects on treatment with immunomodulatory agents within the last 3 months prior to study entry * Subjects who were receiving or had received other experimental drugs within 3 months prior to study entry * Subjects who require any medication for FVIII infusions