If a participant experiences more than one clinically significant bleed in a 4 month period during phase 3 (pharmacokinetic tailored dosing) a dose escalation will occur. The participant will have their prophylaxis dose increased to sustain a trough factor VIII level above 3 IU/dL i.e. the prophylactic dose will be doubled. If the participant has more than one clinically significant bleed in a subsequent 4 month period they will be withdrawn from the study and return to routine care.