A Two Part Randomized Cross-Over Trial to Evaluate the Pharmacokinetics, Efficacy, and Safety Profile of Plasma Protein-Free Recombinant FVIII Formulated With Sucrose (BAY81-8973) in Previously Treated Subjects With Severe Hemophilia A Under Prophylaxis Therapy

The study will assess the pharmacokinetics (part A) safety, tolerability, and efficacy of prophylaxis treatment (2 to 3 times a week) (part B) with BAY81-8973 over a one year period (split into two six month treatment periods). The study will compare 2 different methods (assays) for measuring the amount of study drug, the chromogenic substrate assay per European Pharmacopeia (CS/EP) with the classical assay (Chromogenic Substrate Adjusted, CS/ADJ). During one six month period patients will receive the study drug where the dose has been measured using the" (CS/EP) and during the other six months period the dose will be measured based on the Chromogenic Substrate Adjusted assay CS/ADJ)