Patients who received a one-off gene therapy to treat haemophilia are still doing well up to 13 years later, finds a new study from researchers at University College London (UCL), the Royal Free Hospital and St Jude Children’s Research Hospital, Tennessee. 

The study, published in The New England Journal of Medicine, is the longest reported follow-up for any gene therapy for haemophilia B, a rare genetic disorder caused by insufficient levels of a protein in the blood, called factor IX (nine), that promotes clotting after injury. 

The study included 10 adults with severe haemophilia B who received the gene therapy drug (called scAAV2/8-LP1-hFIXco or Hemgenix) between March 2010 and November 2012. 

The new study confirms that, over a decade later, the patients maintained a steady level of factor IX in the blood, with a median reduction from 14 bleeding episodes to 1.5 bleeding episodes per year.  

This represents an almost tenfold reduction in their annualised bleeding rate (how much someone bleeds over the course of a year). 

Professor Amit Nathwani, Chief Investigator of the study from UCL Cancer Institute and the Royal Free Hospital, said: “It’s incredibly rewarding to see the sustained safety and efficacy, which truly validates the potential of gene therapy as a one-time treatment for this condition. Our findings answer critical questions about the long-term durability of gene therapy, offering profound hope and a significantly improved quality of life for patients.” 

Treatment for haemophilia B has traditionally been through expensive lifelong injections of the clotting factor, but gene therapy offers a potentially transformative means to address the disorder. 

Hemgenix was approved by the UK’s National Institute for Health and Care Excellence (NICE) in 2024, making it available as a treatment option for some adults with moderately severe or severe haemophilia B.

Diana Spencer, Senior Digital Content Editor, DDW