Haemophilia B gene therapy reduces risk of bleeding

A new method of gene therapy has shown initial success in treating patients with the bleeding disorder haemophilia B.

The Phase I/II multi-centre clinical trial of the new therapy involved ten male patients, who were treated with a single injection of the therapy, known as FLT180a. Two years on, nine patients no longer required their initial treatment regime. The clinical trial was conducted by researchers from University College London, the Royal Free Hospital, and the biotechnology company Freeline Therapeutics.

Professor Amit Nathwani, the co-founder of Freeline Therapeutics who co-authored the study published in the New England Journal of Medicine, described the results as adding to 'the growing body of evidence that gene therapy has the potential to free patients from the challenges of having to adhere to lifelong therapy, or could provide treatment where none exists today'.

Haemophilia B is a rare, inherited bleeding disorder characterised by low levels of the Factor IX (FIX) protein, a coagulation factor involved in blood clotting. Those with haemophilia B are at increased risk of heavy bleeding, as well as bruising and severe joint pain.

Current treatment for haemophilia B involves regular injections of recombinant FIX protein to make up for this deficiency. Two years following FLT180a treatment, though, all patients except for one demonstrated sustained FIX levels without these regular treatments.

'Removing the need for haemophilia patients to regularly inject themselves with the missing protein is an important step in improving their quality of life' said Professor Pratima Chowdary, lead author of the study. She added that 'the long-term follow-up study will monitor the patients for durability of expression and surveillance for late effects'.

FLT180a treatment involves delivering a functional copy of the FIX gene directly into a patient's tissues, using a non-enveloped virus as a vector for the gene. This enables the synthesis of functional FIX proteins, leading to long-term responses.

Overall, the patients experienced minimal adverse effects, with the only exception being the patient treated with the highest FLT180a dose, who experienced very high FIX levels as well as an abnormal blood clot. Additionally, patients were required to take immunosuppressants to prevent rejection of the therapy.

Professor John McVey, from the University of Surrey, who was not involved in the study, told New Scientist that, while FIX levels are likely to drop in the long term, these results remain encouraging, adding 'There's a big difference between one injection that cures you for a particular length of time compared to replacement therapy – which is what we use now'.

This optimism is reflected by Professor Chowdary who told the BBC that she predicts that curing haemophilia 'will be a reality for the majority of the adults in the next one to three years.'