Single-dose CSL222 gene therapy for adolescent males (12–17) with severe or moderately severe hemophilia B.

Is this trial a fit for you?

A plain-English reading of the study's rules. Only the study team can confirm whether you qualify.

What this trial studies

This is a phase 3, open-label, single-arm, single-dose, multicenter study administering CSL222 (AAV5-hFIXco-Padua) to adolescent males with severe or moderately severe hemophilia B. Eligible participants are males aged 12 to less than 18 with FIX activity ≤2% who have been on stable prophylactic FIX and have at least 75 prior exposure days, and they must complete a minimum 6-month lead-in period. After lead-in confirmation, participants receive a single infusion of CSL222 and are followed for safety, tolerability, and changes in FIX activity and bleeding outcomes. The study is conducted at U.S. centers and collects efficacy and safety data over planned follow-up visits after treatment.

Why it matters

Who can join: the full rules

Inclusion Criteria:

* Key Inclusion Criteria for the Lead-in Period: Assigned male sex at birth
* Aged ≥138 months (11 years and 6 months) to less than (\<) 206 months (17 years and 2 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.

Exclusion Criteria:

* Key Exclusion Criteria for the Lead-in Period: History of FIX inhibitors or positive FIX inhibitor test at Screening (based on central laboratory results).
* Screening laboratory values (based on central laboratory results):

  * Total bilirubin \> 2 × the upper limit of normal (ULN).
  * Alanine aminotransferase (ALT) \> 2 × the ULN.
  * Aspartate aminotransferase (AST) \> 2 × the ULN.
  * Alkaline phosphatase (ALP) \> 2 × the ULN.
  * Serum creatinine \> 2 × the ULN.
  * Hemoglobin \< 8 g/dL.
* Any condition other than hemophilia B resulting in an increased bleeding tendency.
* Thrombocytopenia, defined as a platelet count below 50 × 10\^9/L, at screening (based on central laboratory results).
* Any uncontrolled or untreated infection (human immunodeficiency virus, hepatitis C, etc) or any other significant concurrent, uncontrolled medical condition, as evaluated by the investigator, including, but not limited to renal, hepatic, cardiovascular, hematological, gastrointestinal, endocrine, pulmonary, neurological, cerebral, or psychiatric disease, alcoholism, drug dependency, or any other psychological disorder evaluated by the investigator to interfere with adherence to the Clinical Study Protocol procedures or with the degree of tolerance to CSL222.
* Additional Key Exclusion Criteria for the Treatment Period: Positive FIX inhibitor test at Visit L-Final (based on central laboratory results)
* AAV5 NAb titer \> 1:900 as assessed at Visit LX (last visit before Visit L-Final).
* Visit L-Final laboratory values (based on central laboratory results) of:

  * Total bilirubin \> 2 × the ULN
  * ALT \> 2 × the ULN.
  * AST \> 2 × the ULN.
  * ALP \> 2 × the ULN.
  * Serum creatinine \> 2 × the ULN.
  * Hemoglobin \< 8 g/dL.
* Thrombocytopenia, defined as a platelet count below 50 × 10\^9/L, at Visit L-Final (based on central laboratory results).

Where it's running

• Center for Inherited Blood Disorders
  Orange, California, United States Recruiting
• Rady Children's Hospital San Diego
  San Diego, California, United States Recruiting
• University of Florida
  Gainesville, Florida, United States Recruiting
• Arthur M. Blank Hospital - Children's Healthcare of Atlanta
  Atlanta, Georgia, United States Recruiting
• University of Michigan Medical Center
  Ann Arbor, Michigan, United States Recruiting
• St. Jude Children's Research Hospital
  Memphis, Tennessee, United States Recruiting

Study contacts

• Study coordinator: Trial Registration Coordinator
• Email: clinicaltrials@cslbehring.com
• Phone: 1-610-878-4697

Similar studies

Other studies for the same condition or treatment. Recruiting studies are listed first.

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• Comparing ANB-002 to standard treatment for hemophilia B

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• Gene therapy for treating hemophilia B

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How to take part

1. Review the eligibility criteria above with your treating physician.
2. Check the official listing on ClinicalTrials.gov for the latest contact details and recruitment status.
3. Contact the study coordinator or principal investigator to ask for pre-screening. Pre-screening is free and never obligates you to enroll.