Efficacy and Safety of CSL222 Gene Therapy in Adults with Haemophilia B with Pretreatment AAV5 NAb

• Research type

  Research Study

• Full title

  Phase 3b, Open-label, Multicenter, Single-dose Study Investigating Efficacy and Safety of CSL222 (Etranacogene Dezaparvovec) Gene Therapy Administered to Adult Subjects with Severe or Moderately Severe Hemophilia B with Detectable Pretreatment AAV5 Neutralizing Antibodies

• IRAS ID

  1012638

• Contact name

  Trial registration coordinator N/A

• Contact email

  clinicaltrials@cslbehring.com

• Sponsor organisation

  CSL Behring LLC

• Clinicaltrials.gov Identifier

  NCT06003387

• Research summary

  Haemophilia B is an inherited genetic bleeding disorder caused by a partial or complete deficiency of the Factor IX (FIX) protein. Patients with Haemophilia B require routine FIX prophylaxis treatment to prevent bleeding. The current standard treatment for haemophilia B is to treat active bleeding with FIX replacement products as needed or to prevent bleeding with prophylactic use of intravenous injections of commercially available recombinant or plasma-derived FIX products.

  The severity of haemophilia B symptoms can vary, and the severe forms become apparent early in life.
  This Phase 3b study will investigate the efficacy and safety of CSL222, an investigational gene therapy product. This is an open-label study therefore all participants will receive CSL222 treatment. All participants will receive a single intravenous infusion of CSL222.

  This study will consist of 6 periods:
  1. Pre-Screening Period
  2. Screening Period
  3. Lead-In Period
  4. Treatment Period
  5. Post-dose Follow up Period
  6. Long-term Follow up Period

  The duration of the study will last approximately 6 years, participants will be followed for 5 years (60 months) post-dose. Approximately 35 participants will take part in this study globally.

  This study is sponsored by CSL Behring LLC.

• REC name

  London - West London & GTAC Research Ethics Committee

• REC reference

  25/LO/0569

• Date of REC Opinion

  30 Oct 2025

• REC opinion

  Further Information Favourable Opinion