- Males who completed 6 months of routine Factor IX prophylaxis therapy during the lead
in study (C0371004) and have > = 50 documented exposure days to a FIX protein product
such as recombinant, plasma-derived or extended half-life FIX product
- Moderately severe to severe hemophilia B (Factor IX activity
- Suspension of prophylaxis therapy for hemophilia B after administration of the study
drug
- Laboratory values (hemoglobin, platelets and creatinine) within study specified limits
- Agree to contraception until components of the drug are eliminated from their body
- Capable of giving signed informed consent
- Anti-AAV Spark100 neutralizing antibodies (nAb) titer, above the established threshold
of 1:1
- History of inhibitor to Factor IX or inhibitor detected during screening.
- Clinical signs or symptoms of decreased response to Factor IX
- Hypersensitivity to Factor IX replacement product or intravenous immunoglobulin
administration
- History of chronic infection or other chronic disease
- Any concurrent clinically significant major disease or condition
- Laboratory values at screening visit that are abnormal or outside acceptable study
limits
- Significant and/or unstable liver disease, biliary disease, significant liver fibrosis
- Planned surgical procedure requiring Factor IX surgical prophylactic factor treatment
12 months from screening visit
- Use of restricted therapies (e.g., blood products, acetylsalicylic acid [aspirin] or
ibuprofen, other investigational therapy, and by-passing agents)
- Participation in a gene therapy research trial at any time or in an interventional
clinical study within 12 weeks of screening visit
- Active hepatitis B or C; hepatitis B surface antigen (HBsAg), hepatitis B virus (HBV)
deoxyribonucleic acid (DNA) positivity, or hepatitis C virus (HCV) ribonucleic acid
(RNA) positivity
- Serological evidence of human immunodeficiency virus HIV-1 or HIV-2 with Cluster of
Differentiation 4 positive (CD4+) cell count ?200 mm3 and/or viral load >20 copies/mL
- Study and sponsor staff and their families involved in the conduct of the study
- Unable to comply with study procedures
- Sensitivity to heparin or heparin induced thrombocytopenia
- Sensitivity to any of the study interventions, or components thereof, or drug or other
allergy