MyPKFiT is a web-based application recently developed by Baxalta for the use in patients treated with Advate. MyPkFit has its basis in Bayesian forecasting, which allows estimation of individual PK parameters by a sparse sampling schedule, where only 2-3 samples are taken between 4 and 48 hours post infusion. With myPKFiT, it will, therefore, be possible to define an individual PK curve for each patient based on just a few sampling points and hence, taking the bleeding phenotype and the life style into account, potentially adjust the prophylactic treatment accordingly to optimize cost-effectiveness.

As detailed in brief summary patients will, after accurate information verbally and written according to ethics approval, report bleeding events during previous 6 months. Blood samples are taken, FVIII analyzed (Advate patients) and the individual PK curve determined using MyPKFit. The curve will be discussed together with the patient and levels related to bleed events determined. If needed dose adjustment is done based on the curve. After a further 6 month follow-up bleeds will again be evaluated as well as factor consumption. In this way a better personalized treatment based on PK and clinical phenotype will hopefully be achieved.

Inclusion Criteria:

• Children and adults with severe hemophilia A (FVIII:C <1 %), being treated with Advate for more than 50 exposure days (EDs

Exclusion Criteria:

• Current evidence of inhibitor as measured by the Nijmegen-modified Bethesda assay
• Use of another investigational FVIII product in the previous month