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New Gene Therapy Could Cure 90 Percent Of Haemophilia B Patients

For one patient, it has changed his life.


Jack Dunhill

Social Media Coordinator and Staff Writer

clockJul 21 2022, 16:24 UTC
Red blood cells
The clotting disorder has affected Mason since birth. Image Credit:

Experimental gene therapy has effectively cured one man of Haemophilia B, a blood disorder in which blood clots cannot form easily, British doctors report. The therapy, detailed in a paper in the New England Journal of Medicine, repairs the mutated gene and allows the body to create a vital clotting protein once more, with Elliott Mason, who has lived with the condition since birth, stating he now lives a normal life. 

People with Haemophilia B have a deficiency in clotting factor IX due to inherited mutations in the gene that creates the factor, resulting in blood that cannot clot. The disease can be extremely dangerous if affected people aren’t vigilant with any potential cuts, and Mason told the BBC that he was unable to play his favorite sports at school and said teachers “wrapped me up in bubble wrap.” 


Mason was enrolled in a 10-patient Phase 1–2 trial of an adenovirus-associated vector gene therapy led by Professor Pratima Chowdary of the Royal Free Hospital and University College London. Each person was given the therapy plus a course of immunosuppressants in an attempt to allow the virus to alter the mutated gene in the desired way. The treatment consisted of an IV drip for just an hour. 

After 26 weeks, each person was called for a follow-up to assess their current factor IX levels. 

Following the treatment, all participants saw an increase in factor IX levels in their blood, with 9 out of 10 sustaining improvements over a mean period of 27 months. One patient’s factor IX results returned to their previous low levels. Out of all of the participants, one experienced a thrombotic event after they had extremely high factor IX levels. 

For Mason, the treatment felt like a miracle cure.  


"I've not had any treatment since I had my therapy, it's all a miracle really, well it's science, but it feels quite miraculous to me," says Elliott, in a statement to the BBC. 

"My life is completely normal, there's nothing that I have to stop and think 'how might my haemophilia affect this?'." 

The therapy appears to be relatively safe, assuming the dose is tightly controlled, and effective in the long term. The researchers believe Haemophilia B will no longer be a problem in the next few years. However, many questions still remain, including whether the results will scale with larger sample sizes, and the likely high cost of the gene therapy – these therapies are notoriously expensive, with some fetching as high as $2.5 million (£2.1 million) per dose.  

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  • hemophilia,

  • blood clotting