Efficacy and Safety of CSL222 (Etranacogene Dezaparvovec) Gene Therapy in Adults With Hemophilia B With Pretreatment Adeno-associated Virus Serotype 5 (AAV5) Neutralizing Antibodies (Nabs)
Trial Parameters
Brief Summary
The purpose of this study is to assess the risk of bleeding due to failure of expected pharmacological action of CSL222 in adults with severe or moderately severe hemophilia B with detectable pretreatment AAV5 Nabs.
Eligibility Criteria
Inclusion Criteria: * Considered legally an adult, as defined by country regulations. * Has 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 is on continuous routine FIX prophylaxis. * Has 2 consecutive detectable AAV5 NAb titer results between Screening and Visit L-Final using a validated AAV5 NAb assay (based on central laboratory results). * Has greater than (\>) 150 previous exposure days to FIX replacement therapy. * Has been on stable FIX prophylaxis for at least 2 months before Screening. * Has demonstrated capability to independently, accurately, and in a timely manner complete the eDiary during the Lead-in Period, as judged by the investigator. * Acceptance to adhere to contraception guidelines. * Able to provide informed consent after receipt of verbal and written information about the study. * Investigator believes that the participant (or the participant's leg