The main objective of the study is to compare the pharmacokinetics of Optivate® with the subject's current FVIII concentrate when given as a bolus dose of 50IU/kg. The secondary objective is to compare the first and second pharmacokinetic assessments on Optivate® (and recovery if a subject changes batch) to evaluate Optivate® in terms of clinical tolerance and safety.

Inclusion Criteria:

• Previously treated subjects with severe Haemophilia A (<2% basal FVIII activity) without inhibitor to Factor VIII, at least 12 years of age, currently receiving FVIII concentrate and with more than 20 exposure days.

Exclusion Criteria:

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