Hemophilia B is a life-threatening blood disorder where patients produce insufficient amounts of a blood clotting protein called Factor IX, leading to internal bleeds and joint damage. For decades, the main treatment has been lifelong, regular infusions of Factor IX, which can have a negative impact on the patient’s quality of life.
In November 2022, the U.S. Food and Drug Administration (FDA) granted market approval to CSL’s gene therapy candidate Hemgenix, making it the first approved gene therapy to tackle hemophilia B.
In December, the European Medicines Agency (EMA) recommended the approval of the same treatment, and the European Commission has now followed up by granting a conditional marketing authorization for Hemgenix in EU member states, Iceland, Norway and Liechtenstein.
From regular infusions to a single dose
Also known as etranacogene dezaparvovec, Hemgenix involves delivering a variant of the gene encoding Factor IX called Factor IX-Padua into patients using a viral vector. Once the therapy is delivered, the patient’s own cells can produce Factor IX proteins that are more effective than regular Factor IX. Instead of requiring regular infusions, Hemgenix is designed to address the symptoms of hemophilia B with a single dose.
Hemgenix was approved based on results from a phase 3 trial called HOPE-B, where the therapy boosted Factor IX activity in patients and cut their annualized bleed rate by 64%. By 18 months after receiving Hemgenix, patients’ Factor IX consumption was also 97% less than before the therapy. The trial is ongoing and at the two-year time point, the therapy has continued to show a sustained effect.
"This approval marks an important step forward in the treatment of hemophilia B, which could be transformative for people who are debilitated by bleeds into their muscles, joints and internal organs, alleviating the burden of lifelong intravenous infusions of Factor IX products," stated Wolfgang Miesbach, head of coagulation disorders at the Comprehensive Care Center, University Hospital of Frankfurt, and an investigator in the HOPE-B trial.
"Data from the HOPE-B study demonstrate the potential of Hemgenix to remove the need for routine prophylaxis, by providing durable Factor IX activity, as well as improved bleeding outcomes and quality of life for people with hemophilia B."
Commercializing the therapy
Hemgenix was originally developed by the Dutch biotechnology company uniQure. Not long after HOPE-B showed promising first results in 2020, CSL licensed the global commercialization rights for the gene therapy for $450m upfront and up to $1.6bn in milestone payments. With the EU and US approvals under its belt, CSL is now anticipating a regulatory decision from the UK.
When Hemgenix was approved by the US FDA in 2022, CSL set the price at a colossal $3.5m, making it the world's most expensive treatment. It is also considerably more expensive than the second-most expensive drug: the spinal muscular atrophy gene therapy Zolgensma, which is priced at $2.1m. The pricing strategy for Hemgenix in Europe is yet to be disclosed.
Competition on the horizon
While Hemgenix is the first-approved gene therapy for hemophilia B, it may not be the only one for much longer. Another gene therapy candidate called fidanacogene elaparvovec, developed by Pfizer, showed promising topline phase 3 results for the treatment of hemophilia B in late 2022. The big pharma company plans to discuss the data with regulatory authorities this year.
For a long time, the UK firm Freeline Therapeutics had its own hemophilia gene therapy candidate in early clinical trials. However, the company decided to put the therapy on the backburner in late 2022, choosing instead to focus on Fabry disease.