The New England Journal of Medicine (NEJM) recently published long-term follow up data on patients who have previously received the hemophilia B gene therapy fidanacogene elaparvovec. The therapy was approved by the U.S. Food and Drug Administration in the spring of 2024 (under the brand name BEQVEZ™) for the treatment of adults with moderate to severe hemophilia B.
Fidanacogene elaparvovec, which is manufactured by Pfizer, is designed with bioengineered adeno-associated virus (AAVs) vectors to introduce a working copy of the factor IX (FIX) gene. The therapy is administered as a one-time intravenous infusion to stimulate the long-term production of clotting FIX and prevent bleeding.
In total, 14 hemophilia B patients were included in the long-term follow-up study, all of whom were administered BEQVEZ at the same dose level (5×1011 AAV vector genome per kilogram of body weight). The investigators looked at both safety and efficacy.
All participants completed at least three years of follow-up (median, 5.5; range 3 to 6) and participation was ongoing among eight at the data cutoff. None of the participants reported treatment-related adverse events after one year. Nine serious adverse events were reported in four participants during the follow-up/before the data cut off, none of which were thrombotic, or treatment related. In addition, no FIX inhibitors were detected.
During the follow-up, mean factor IX activity was in the mild hemophilia range, as mean annualized bleeding rates were reduced from 11.1 events per year pre-gene therapy to 0.4 bleeding events per year post-therapy. Further, 10 participants reported zero treated bleeding episodes.
“Our findings mark the longest-ever follow-up for patients with hemophilia B who received gene therapy with FIX-Padua,” said Benjamin J. Samelson-Jones, MD, PhD, a lead study author and attending physician in the Division of Hematology at CHOP, said in a press release. “These results offer hope that gene therapy for hemophilia B has the potential to transform the standard of care, offering a future with greater independence and improved quality of life for hemophilia patients.”
The article, “Fidanacogene Elaparvovec for Hemophilia B — A Multiyear Follow-up Study,” was published online, April 16th in the online in the NEJM. The research that informed this paper was funded by Pfizer.
Source: docwirenews, May 13, 2025
