This is a randomized, prospective, multicenter study to examine whether or not the current recommended factor dosing strategy - i.e., dosing by actual body weight - in overweight and obese patients with Hemophilia A may deliver excessive clotting factor to achieve the desired result of bleeding prevention and cessation. This study also examines ways to prevent delivering excessive factor by using a patient's ideal body weight as a new dosing strategy compared to the current dosing strategy. The hypothesis being tested is that factor dosing based on ideal body weight will result in protective factor levels.

This is a randomized, prospective, multicenter, open-label, crossover study to examine whether or not the current recommended factor dosing strategy, i.e., dosing by actual body weight in overweight and obese patients, may deliver more clotting factor than necessary to cause bleeding to stop in participants with Hemophilia A who use Factor VIII (FVIII). This study also examines ways to prevent delivering too much factor by using a participant's ideal body weight as a new dosing strategy compared to the current dosing strategy. The hypothesis being tested is that factor dosing based on ideal body weight will result in hemostatic factor levels.

The study will be conducted at the Washington Center for Bleeding Disorders (WCBD) at Bloodworks Northwest, Oregon Health & Science University (OHSU), Seattle Children's Hospital (SCH), and Providence Sacred Heart Children's Hospital (SH). Cumulatively across the four sites, up to 20 participants will be enrolled. Randomization will be performed centrally at WCBD.

Participants will provide their own factor. Prior to the first study-related dose, participants will stop taking any FVIII products for either 48 hours if currently using a short-acting FVIII product or 72 hours for a long acting FVIII product. Factor levels will be measured immediately before and at multiple points after two different factor doses. Subjects will be randomized to start their dosage based either on actual body weight or ideal body weight first and then crossover to receive dosage based on the other category.

Inclusion Criteria:

• Hemophilia A
• Able and willing to comply with pharmacokinetic testing schedule
• Either overweight or obese BMI using CDC definitions by age

Exclusion Criteria:

• Inhibitor of > 0.6 BU twice in the past, or documented abnormal recovery of less than 66% (of expected) in the past
• Known other bleeding disorder
• Known other prolongation in aPTT (lupus anticoagulant, FXII deficiency)
• Female