Study Evaluating Prophylaxis Treatment & Characterizing Efficacy, Safety, & PK Of B-Domain Deleted Recombinant FVIII

Inclusion Criteria:

• Male subjects, aged less than 6 years, with moderately severe to severe hemophilia A.
• A negative FVIII inhibitor titer at screening, and a medical history negative for a past FVIII inhibitor.
• At least 20 exposure days to any FVIII replacement product.
• Adequate hepatic and renal function
• CD4 count > 400 cells/uL, and if receiving antiviral therapy must be on a stable regimen

Additional criteria for subjects participating in the PK assessment:

• Male subjects as described immediately above except they must have a FVIII Activity of less than or equal to 1% confirmed by the central laboratory screening test
• Age < 6 years at time of PK assessment.
• The subject's size is sufficient to permit PK-related phlebotomy.
• The subject is able to comply with the procedures conducted during the PK assessment, including a mandatory 72-hour washout period preceding the PK assessment.

Exclusion Criteria:

• A history of FVIII inhibitor.
• Presence of a bleeding disorder in addition to hemophilia A.
• Treatment with any investigational drug or device within 30 days before the time of signing the informed consent form.
• Major or orthopedic surgery planned to occur during the course of the study.
• Regular (e.g., daily, every other day) use of antifibrinolytic agents or medications known to influence platelet function such as aspirin or certain nonsteroidal anti-inflammatory drugs (NSAIDs), or regular, concomitant therapy with immunomodulating drugs (e.g., intravenous immunoglobulin [IVIG], routine systemic corticosteroids).
• Known hypersensitivity to hamster protein.