14th December 2017

Gene therapy for haemophilia A: "Mind-blowing results"

British doctors have used a new form of gene therapy to treat haemophilia A, a genetic defect that leads to excess bleeding.

A cure for haemophilia A (the most common type of the illness) may be in sight, after a groundbreaking gene therapy trial led by Barts Health NHS Trust in collaboration with Queen Mary University of London. Researchers found that a single treatment of the new drug resulted in participants with haemophilia A showing normal levels of a previously missing protein, effectively curing them.

85% of patients in the trial achieved normal or near-normal levels of factor VIII – an essential blood clotting protein – even many months after treatment. Described as "transformational" by Barts, the results have particular significance as the first successful gene therapy for haemophilia A.

Haemophilia A usually occurs in males, affecting roughly 1 in 5,000. A genetically inherited condition, it puts those affected at risk of bleeding even from the slightest injury, as well as causing spontaneous internal bleeding, which can be life-threatening. Recurring bleeding into joints can also lead to progressive joint damage and arthritis. Until now, the only available treatment has been multiple weekly injections of factor VIII to control and prevent bleeding.

The new therapy involves a genetically engineered virus, containing the molecular instructions for factor VIII. It is delivered to the liver, which then starts producing the blood-clotting protein.

"This is huge," said Professor John Pasi, who led the trials. "It's ground-breaking, because the option to think about normalising levels in patients with severe haemophilia is absolutely mind-blowing. To offer people the potential of a normal life, when they've had to inject themselves with factor VIII every other day to prevent bleeding, is transformational."

“The gene therapy has changed my life," said Jake Omer, 29, who is married with two children and lives in Billericay. "I now have hope for my future. It is incredible to now hope that I can play with my kids, kick a ball around and climb trees well into my kids' teenage years and beyond. Arthritis in my ankles meant I used to worry how far I would be able to walk once I turned 40. At 23, I struggled to run 100m to catch a bus; now at 29 I'm walking two miles every day which I just couldn't have done before having the gene therapy treatment."

This trial was quite small, with only 13 volunteers from across England. However, the researchers now plan to hold larger tests in groups of people from around the world, including the USA, Europe, Africa and South America.

The research appears in The New England Journal of Medicine.

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