Gene therapy also better than prophylaxis with factor IX in hemophilia B after 24 months of follow-up

Gene therapy with etranacogene dezaparvovec is an effective and safe treatment for patients with moderate or severe hemophilia B. This is the conclusion of internist-vascular physician Michiel Coppens (Amsterdam UMC) and fellow researchers based on the results of a post-hoc analysis of the HOPE -B study after 24 months follow-up.¹

In this international phase III study, 54 adult men with moderate or severe haemophilia B from 33 hospitals in the European Union, the UK and the US were treated intravenously with etranacogene dezaparvovec (2 x 10¹³ genome copies per kg body weight). Treatment was preceded by a pre-infusion phase of at least 6 months during which patients were routinely administered prophylaxis with factor IX (FIX). The primary outcome measure was annual bleeding frequency.

Post hoc analysis

Previously, treatment with etranacogene dezaparvovec was shown to result in a 64% lower annual bleeding rate after 18 months of follow-up (4.19 vs. 1.51; rate ratio). [95%-BI]: 0.36 [0,20-0,64]) and had a favorable safety profile compared to FIX prophylaxis in the pre-infusion phase. To assess the longer-term efficacy and safety of etranacogene dezaparvovec, researchers conducted a post hoc analysis after a median follow-up of 26.5 months.

This showed that the annual bleeding frequency decreased from 4.18 to 1.51 (‘rate ratio’) thanks to gene therapy. [95%-BI]: 0.36 [0,20-0,64]), which agrees with the results of the previous analysis. Furthermore, no new safety signals were observed. There were also no treatment-related serious adverse events or deaths.

Most expensive

Etranacogene dezaparvovec is marketed in Europe by CSL Behring under the brand name Hemgenix. In 2022, this drug caused a bit of a stir when it became the most expensive drug ever at the time, with a US price of $3.5 million per treatment. The price in the Netherlands is determined during a lock procedure and is therefore secret.

References

1. Pipe SW, Leebeek FWG, Recht M, et al. Gene therapy with etranacogene dezaparvovec for hemophilia B. N Engl J Med 2023;388:706-18.
2. Coppens M, Pipe SW, Miesbach W, et al; HOPE-B Investigators. Etranacogene dezaparvovec gene therapy for haemophilia B (HOPE-B): 24-month post-hoc efficacy and safety data from a single-arm, multicentre, phase 3 trial. Lancet Haematol 2024;11:e265-75.