1. Males 18 years or older with established severe Haemophilia A (endogenous FVIII level ≤1 IU/dL) as evidenced by their medical history.
2. Treated/exposed to FVIII concentrates or cryoprecipitate for a minimum of 150 exposure days (EDs)
3. Greater than or equal to 12 bleeding episodes for patients on on-demand FVIII replacement therapy over the previous 12 months. Does not apply to patients on prophylaxis
4. No history of inhibitor, and results from a modified Nijmegen Bethesda assay of less than 0.6 Bethesda Units (BU) 2 consecutive occasions at least one week apart within the past 12 months
5. Sexually active patients must be willing to use an acceptable method of contraception.

1. Detectable pre-existing immunity to the AAV5 capsid as measured by adeno-associated virus 5 (AAV5) transduction inhibition (TI) or AAV5 total antibodies
2. Any evidence of immunosuppressive disorder or active chronic infection including hepatis B, hepatitis C, HIV
3. Significant liver dysfunction as defined by abnormal elevation ofliver function tests, or for patients who have undergone liver imaging or biopsy and found to have evidence of grade 3 or higher fibrosis
4. Evidence of any bleeding disorder not related to haemophilia A
5. 12. Treatment with any investigational product within 30 days prior to the end of the screening period, or any previous exposure to any gene transfer therapy
6. Any disease or condition that per the physician’s discretion would prevent the patient from fully complying with the requirements of the study including possible corticosteroid treatment outlined in the protocol. The physician may exclude patients unwilling or unable to agree on not using alcohol for the 16-week period following the viral infusion