Etranacogene dezaparvovec in people with hemophilia B with preexisting adeno-associated virus 5 neutralizing antibodies: 4-year subgroup results from the HOPE-B trial

Background: Health Outcomes with Padua Gene; Evaluation in Hemophilia B (HOPE-B) is the first phase 3 trial of adeno-associated virus (AAV) serotype 5 vector-based gene therapy for hemophilia B to have enrolled participants with neutralizing antibodies (NAbs) to the viral vector. Objectives: Evaluate the efficacy and safety of etranacogene dezaparvovec in a post hoc subgroup of participants with preexisting AAV5 NAbs 4 years posttherapy. Methods: After a ≥6-month lead-in period on continuous prophylaxis, people with moderately severe/severe hemophilia B (factor [F]IX ≤ 2%) received a single infusion of etranacogene dezaparvovec. AAV5 NAb status prior to infusion was determined. FIX activity, annualized bleeding rates (ABRs), and safety were evaluated in participants with preexisting AAV5 NAbs. Results: < .0001). The most frequent treatment-related adverse events were infusion-related reactions (23.8%) and transient alanine aminotransferase elevations (14.3%). No late hepatotoxicity was observed. Conclusion: Etranacogene dezaparvovec demonstrated long-term efficacy and safety in individuals with preexisting AAV5 NAb titers ≤ 678, expanding eligibility for gene therapy to a broader hemophilia B population.