Introduction: The Quest for Durability in Hemophilia B
For decades, the standard of care for severe or moderately severe hemophilia B has been prophylactic replacement therapy. While effective at reducing bleeds, this approach imposes a significant treatment burden, requiring lifelong, frequent intravenous infusions of factor IX (FIX) concentrates. The advent of gene therapy, specifically etranacogene dezaparvovec (an AAV5-vector-based therapy expressing the hyper-functional Padua variant of FIX), promised a ‘one-and-done’ solution. However, the critical question for clinicians and patients has always been the duration of this effect. The final five-year results of the HOPE-B study provide the most definitive answer to date regarding the long-term stability and clinical utility of this therapeutic modality.
