Phase 3, Open-label, Single-dose, Multicenter Study Investigating Efficacy, Safety, and Tolerability of CSL222 (Etranacogene Dezaparvovec) Administered to Adolescent Male Subjects (≥ 12 to < 18 Years of Age) With Severe or Moderately Severe Hemophilia B
This is a phase 3, prospective, open-label, single-arm, single-dose, multicenter study investigating the efficacy, safety, and tolerability of CSL222 (AAV5-hFIXco-Padua) in adolescent male participants with severe or moderately severe hemophilia B.
• Assigned male sex at birth
• Aged \>=138 months to less than (\<) 206 months at the time of informed consent / assent.
• Congenital hemophilia B with known severe or moderately severe FIX deficiency (less than or equal to \[\<=\] 2% of normal circulating FIX) for which the participant has been on continuous FIX prophylaxis.
• On stable continuous FIX prophylaxis for at least 2 months before Screening.
• Minimum of 75 previous exposure days of treatment with FIX protein before Screening.
⁃ Additional Key Inclusion Criteria for the Treatment Period:
• Completed the Lead-in Period: minimum of 6 months (26 weeks) of lead-in data collected and eligibility has been confirmed.
• Aged \>= 12 to \< 18 years at the time of CSL222 treatment.