CSL Behring recently announced three-year post treatment data from clinical trial participants who received a one-time infusion of Hemgenix® (etranacogene dezaparvovec), an adeno-associated virus (AAV) vector-based hemophilia gene therapy. Hemgenix was approved by the U.S. Food and Drug Administration a little more than a year ago 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.

The results were presented via an oral presentation delivered at the 65th American Society of Hematology (ASH) Annual Meeting and Exposition, which was held December 8-12, in San Diego, CA. According to the CSL press release that accompanied the ASH presentation, three-year data showed overall sustained levels of FIX amongst participants in the phase 3 HOPE-B clinical study.

HOPE-B included 54 Hemgenix-treated participants with severe or moderately severe hemophilia B with or without pre-existing AAV5 neutralizing antibodies – of those 52 completed the three-year follow-up. The data demonstrated that the mean annualized bleeding rate (ABR) for all bleeds was reduced by 64% during months 7-36 of the study (mean ABR 1.52 vs. 4.17 during the lead-in period). In addition, 94% (51 out of 54) of patients were able to forgo continuous prophylactic therapy.

In terms of safety, the company reported that there were no serious adverse events related to treatment with Hemgenix and the therapy was generally well-tolerated with most (76%) treatment-emergent adverse events (TEAEs) considered mild. Further, 95% of TEAEs occurred before six months post-treatment.

"The long-term follow-up data from the HOPE-B study reinforces that a one-time treatment with HEMGENIX can produce elevated and sustained factor IX levels and reduce the rate of annual bleeds for years in people living with hemophilia B," said Dr. Steven Pipe, Professor of Pediatrics and Pathology at the University of Michigan and principal investigator of the HOPE-B pivotal trial. "Most importantly, the data show that nearly all the Phase III trial participants three years post-treatment with HEMGENIX have remained free from the need for regular prophylactic infusions, which is groundbreaking for the hemophilia B community."

Source: CSL press release dated December 11, 2023