CSL recently announced the publication of five years’ worth of data from their HOPE-B clinical trial program, which has been investigating the company’s hemophilia B gene therapy Hemgenix® (etranacogene dezaparvovec). NBDF is sharing this research update to help the bleeding disorders community stay informed about emerging gene therapy data and evolving treatment options for hemophilia B.
Hemgenix is an adeno-associated virus (AAV) vector-based hemophilia gene therapy product that received approval by the U.S. Food and Drug Administration in November 2022. It is indicated for the treatment of adults with hemophilia B who currently use factor IX (FIX) prophylaxis therapy, or have current or historical life-threatening hemorrhage, or have repeated, serious spontaneous bleeding episodes. Gene therapy is a developing area of treatment for some individuals with bleeding disorders, and long-term data such as this helps the community understand potential treatment options.
The HOPE-B program included 54 Hemgenix-treated participants with severe or moderately severe hemophilia B with or without pre-existing AAV5 neutralizing antibodies. Enrolled patients were administered the therapy at treatment centers in the US and Europe. The five-year results, which were published December 7th in The New England Journal of Medicine, showed overall mean FIX activity levels holding at 36.1%. The adjusted annualized bleeding rate (ABR) for all bleeding events was 4.16 during the pre-gene therapy lead-in period and 1.52 after a single infusion of Hemgenix. This post-treatment period spanned from months seven to 60 (the five-year mark) and represented a 63% decrease in ABR. In addition, 51 of 54 participants (94%) were able to forgo prophylactic therapy. CSL also cited a “favorable” safety profile.
"The five-year HOPE-B results mark a pivotal milestone for gene therapy, providing clear, long-term data of the ability of HEMGENIX to potentially transform care for adults with hemophilia B," said Steven Pipe, MD, professor of pediatrics and pathology, Hemophilia and Coagulation Disorders Program and the Special Coagulation Laboratory, University of Michigan. "For those who have relied on frequent prophylactic infusions, achieving lasting bleed control from a single treatment offers the potential for greater day-to-day freedom and a life less burdened by the demands of ongoing therapy," added Pipe.
The data was also presented at the 67th American Society of Hematology Annual Meeting and Exposition, held December 6-9 in Orlando, FL.
NBDF will continue to follow new research and clinical findings in hemophilia and other bleeding disorders and share updates to support informed decision-making within the community.
Source: CSL news release dated December 7, 2025
