The main objective of the study is to assess the pharmacokinetics of FACTOR X after a single dose of 25IU/kg.

The secondary objectives of the study are to assess efficacy and safety of FACTOR X in the treatment of bleeding episodes over at least 6 months.

Inclusion Criteria:

• Written informed consent given, or for subjects aged 12-17 years, have given written assent and whose parent/guardian has given written informed consent
• At least 12 years of age at dtae of written informed consent
• Have hereditary severe or moderate FX deficiency
• Currently treated with Fresh Frozen Plasma FFP, Prothrombin Complex Concentrate PCC or factor IX/X concentrate
• Must have a minimum of one spontaneous or menorrhagic bleed in the last 12 months which required treatment of FFP, PCC or factor IX/X concentrate. Newly diagnosed subjects who present at the hospital with a bleed may be included
• Must have had at least 7 days, and ideally 10-14 days, since an infusion of either FFP, PCC or factor IX/X concentrate at Baseline Visit
• Females of child bearing potential must have a negative result on a HCG based pregnancy test. If they are or become sexually active, they must practise contraception by using a method of proven reliability for the duration of the study

Exclusion Criteria:

• Have a history of inhibitor development to FX or a positive result at the Screening Visit
• Bleeding at the appointment for the PK assessment
• Subjects who have thrombocytopenia
• Have clinically significant liver disease
• Known to have other coagulopathy or thrombophilia
• Have known or suspected hypersensitivity to the investigational medicinal product or its excipients
• Have abused chemicals or drugs within the past 12 months
• Have a history of unreliability or non-cooperation
• Participating or have taken part in another trial within the last 30 days, with the exception of BPL FX surgery study - Protocol Ten03. In such cases, subjects should have completed their End of Study Visit either before or on the day of Screening Visit for this study
• Female subjects who are pregnant or lactating
• Subjects planning greater than 4 weeks absence from the locality of the Investigational site, between the screening visit and the repeat PK assessment