CSL's HEMGENIX Shows Durable Benefit, A New Future For Gene Therapy in Hemophilia B
By Erin Harris, Editor-In-Chief, Cell & Gene
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The five-year follow-up data from CSL’s HEMGENIX have marked a defining moment in the evolution of gene therapy for hemophilia B. The Phase 3 HOPE-B results, which have been published in The New England Journal of Medicine, reaffirm HEMGENIX’s durable safety and efficacy profile showing sustained factor IX activity, significant bleed protection, and freedom from routine prophylaxis through five years post-infusion. As the first and only approved gene therapy for hemophilia B, these data underscore the therapy’s long-term impact not only for patients but also for the broader field of genetic medicines.
I caught up with Deborah Long, M.D., SVP, Medical Affairs, and Diego Sacristan, SVP, Head of U.S. at CSL to discuss what these results mean for patients, how real-world adoption is progressing across global markets, and how CSL’s approach to access and value-based care is shaping the future for next-generation gene therapies.
HEMGENIX is the first and only approved gene therapy for hemophilia B. From your perspective, what makes these five-year Phase 3 data a true watershed moment for patients?
Deborah Long: The five-year HOPE-B data published in the New England Journal of Medicine reaffirm that HEMGENIX delivers long-term, elevated and sustained factor IX activity, greater bleed protection compared to prophylaxis, and freedom from routine factor IX prophylaxis, all while maintaining a favorable safety profile. For patients, these results mean the possibilities of experiencing fewer bleeds compared to prophylaxis and living free from the routine burden of continuous infusions. For the gene therapy field, this is a clear demonstration of durable efficacy and favorable safety over five years.
With more than 75 individuals treated across eight countries, what have you learned about real-world adoption both in terms of clinical outcomes and how payers and treatment centers are engaging with this therapy?
Diego Sacristan: It has taken some time, but adoption of HEMGENIX is growing. Since HEMGENIX received regulatory approval, including FDA approval in the U.S. and market authorizations in other countries, more than 75 individuals across eight countries have received HEMGENIX as of November 2025, reflecting global momentum. In the U.S., more than 50 patients have been treated, more than 65 administration sites have been trained, and major payers now cover more than 80% of U.S. commercial lives.
Payers are engaging through broad coverage across commercial insurance, Medicaid, and Medicare. Aligning with our commitment to value-based care, CSL has also seen success by offering value-based arrangements to payers under which a substantial portion of cost is refunded to the payer if a patient returns to prophylactic factor IX within the first four years.
Treatment centers report positive experiences with successful patient treatments, and we are continuing to educate physicians, patients, and centers about gene therapy. We also support the treatment process via HEMGENIX ConnectSM, which includes personalized support, help with insurance, and a $0 copay assistance program for eligible patients. Over the long term, HEMGENIX continues to save the health system money, given that lifetime costs for moderate to severe hemophilia B can exceed $20 million per adult in the U.S.
Durability is a key question for any gene therapy. Looking specifically at this five-year dataset, what signals are you seeing around sustained factor levels, bleeding rates, and quality of life?
Deborah Long: We are seeing durable factor levels, sustained bleed protection, and patients remaining free from prophylaxis. Mean factor IX activity has remained strong at greater than 36% during years one through five post-infusion. Meanwhile, a single dose of HEMGENIX continues to provide bleed protection relative to baseline, with 94% of patients remaining free of continuous prophylaxis at five years. Five-year data also highlight a sustained meaningful reduction of greater than 93% in joint bleeds, a major driver of pain and disability that can lead to reduced mobility and lower quality of life.
Achieving reimbursement in 10 international markets and training over 65 U.S. centers is no small feat. What practical barriers had to be overcome to get to this point? Where do you still see work to do to ensure broader, equitable access?
Diego Sacristan: As the first gene therapy for hemophilia B, we are evolving the treatment paradigm, which means we need to continue to educate physicians, patients, and treatment centers about gene therapy and HEMGENIX and support the treatment process. Governmental investment in specialized treatment center expertise and infrastructure is also needed. Additionally, identifying innovative access pathways requires effort and flexibility. While this will take time, we are committed to advancing this important treatment option for the hemophilia B community.
CSL is working with local authorities to propose reimbursement agreements based on each country’s needs. In the U.S., we offer value-based agreements (VBAs) where we refund a substantial portion of the cost if a patient resumes prophylactic factor IX within four years. In the U.S., most payers have clear policies for HEMGENIX, providing coverage through commercial payers, Medicare, and Medicaid and we expect broad access to this treatment. Patients can enroll in the HEMGENIX ConnectSM program for dedicated support in insurance inquiries and financial assistance eligibility. The copay assistance program may reduce out-of-pocket costs to $0 for commercially insured individuals.
Based on the HEMGENIX experience so far, what lessons would you highlight for the next wave of gene therapies in rare diseases?
Deborah Long: CSL’s experience with HEMGENIX shows that gene therapies in rare diseases must pair durable, clinically relevant evidence with a comprehensive access strategy. We are committed to showcasing the robust durability and safety data for HEMGENIX and are sharing long-term evidence through these final, five-year HOPE-B results, the ongoing, longer-term follow-up of these patients via the IX-TEND 222-3003 study, and a post marketing registry.
To translate durability into equitable access, we are partnering with the health care ecosystem to evolve the care pathway through early and sustained education for physicians, patients, and treatment centers, site training, and hands-on logistical support. We are also partnering with payers to establish broad coverage and value-based arrangements aligned with value-based care, reinforced by ICER’s recognition of HEMGENIX as a high-value therapy. Lastly, we support patients end-to-end through HEMGENIX ConnectSM for education, insurance, and financial assistance.