This is an investigator-initiated, industry-funded, multi-centre, international study that will be carried out prospectively at hemophilia treatment centres across Canada, the Czech Republic and Australia with SickKids as the coordinating site. The study will use a central laboratory not directly affiliated with any of the participating sites. Enrollment target is 50 participants, both adult and pediatric with severe hemophilia A receiving Advate, who will each complete a 2-point and 6-point pharmacokinetic (PK) sampling. The main aim is to compare the results of a 2 sample PK using clinically practical time points and myPKFiT™ (a web-based, population PK Bayesian tool) to a 6 sample population PK to determine whether the results obtained are in good agreement.

Inclusion Criteria:

• Confirmed diagnosis of Hemophilia A;
• Severe disease (FVIII <2%);
• Receiving ADVATE for prevention of bleeding (prophylaxis) or receiving ADVATE on demand and a candidate for prophylaxis;
• Body weight ≤120 kg; and ≥12kg;

Exclusion Criteria:

• FVIII inhibitor positive (level of ≥0.6 Bethesda Units [BU] per mL using the Nijmegen modification of the Bethesda assay). Inhibitor status to be documented as negative prior to study enrollment according to the two most recent, consecutive inhibitor assays on record. If patients have < 50 exposure days, an assay will be completed centrally within a reasonable timeframe (approximately 8 weeks suggested) to make sure that they are negative.
• Body weight >120 kg or <12kg;
• Human immunodeficiency virus (HIV) positivity with cluster of differentiation 4 (CD4) count < 200 / microliter;
• Significant hepatic dysfunction, alanine aminotransferase (ALT) or aspartate aminotransferase (AST) >5 times upper limit of normal
• History of recent events that might affect FVIII half-life (e.g., infection, surgery or an invasive procedure) within 2 weeks of blood sampling.

Patients with severe Hemophilia A