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

Assessment of the Risk of Inhibitor Formation in Subjects With Severe Hemophilia A When Switched From a Replacement Therapy With a rFVIII Produced by a Chinese Hamster Ovary (CHO) Cell Line to a rFVIII Produced by a Baby Hamster Kidney (BHK) Cell Line (Kogenate® FS).

Most transient inhibitor formation, if any, will develop within the first 4 weeks. The study is to further monitor whether participants with severe Hemophilia A will develop inhibitors or antibodies at the later stage when switched from their current recombinant therapy produced from Chinese Hamster Ovary (CHO) cell line to Kogenate-FS raised in a Baby Hamster Kidney cell line.

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