Gene Therapy for Hemophilia B Patients Aged 12-18 Years Old

Inclusion Criteria:

1. Subjects and statutory guardian must be able to understand the purpose and risks ofthe study and provide signed and dated informed consent;

2. Be male and 12≤ age <18 years of age, body wight ≥ 50kg;

3. Have hemophilia B with ≤2 IU/dL (≤2 %) endogenous FIX activity levels as documentedby a certified clinical laboratory at the time of screening. If the screening resultis >2% due to insufficient washout from FIX protein product, then the severity ofhemophilia B may be confirmed by documented historical evidence from a certifiedclinical laboratory demonstrating ≤2% FIX coagulant activity (FIX:C) ;

4. Had had ≥75 prior exposure days (EDs) to any recombinant and/or plasma-derived FIXprotein products based on historical data from the subject's record/history;

5. With ≤ 1:4 neutralizing antibodies and ≤1:200 binding antibodies against BBM-H901capsid;

6. Subjects with bleeding episode and/ or FIX agents infusion events within 12 weeksprior to screening;

7. Have no prior history of hypersensitivity or anaphylaxis associated with any FIX orIV immunoglobulin administration;

8. Have no measurable FIX inhibitor as assessed by laboratory; or documented no priorhistory of FIX inhibitor (family history of inhibitors will not exclude the subject)and no clinical signs or symptoms of decreased response to FIX administration;

9. Have acceptable laboratory values:

10. Hemoglobin ≥11 g/dL ;

11. Platelets ≥100,000 cells/μL;

12. AST, ALT ≤1.5x upper limit of normal at the testing laboratory;

13. Bilirubin ≤1.5x ULN ;

14. glomerular filtration rate eGFR ≥ 60ml/min.

15. For those subjects with sexual maturity, subject and statutory guardian must knowthat subjects must agree to use reliable barrier contraception until 52 weeks;

16. with good compliance to the schedule of visit and fill in the subject diary.

Exclusion Criteria:

1. Hepatitis B surface antigen antibody (HBSAg-Ab) or HBV-DNA positive; hepatitis Cantibody or HCV-RNA positive;

2. Currently on antiviral therapy for hepatitis B or C;

3. With coagulation disorders other than hemophilia B;

4. Had immunosuppressive therapy other than steroid and other suggested IST agentswithin 30 days prior to screening;

5. Had vaccine 30 days prior to screening or have scheduled vaccination plan during thestudy (up to 52 weeks);

6. Have significant underlying liver disease, as defined by a preexisting diagnosis ofportal hypertension, splenomegaly, encephalopathy, etc; other liver conditionsunsuitable to gene therapy judged by investigator;

7. Have surgery plan within 52 weeks after gene therapy;

8. Have history of chronic infection or high rish of infection that the Investigatorconsiders to constitute an unacceptable risk;

9. Had participated in a previous gene therapy research trial within the last 52 weeksor in a clinical study with an investigational drug within the last 12 weeks;

10. Had any herb that may affect the liver function within 4 weeks prior to screening;

11. Have history of fatal bleeding episode, eg intracranial hemorrhage, etc;

12. Any concurrent clinically significant major disease or any other condition that, inthe opinion of the Investigator, makes the subject unsuitable for participation inthe study;