Haemophilia gene therapy 'solution'

Factor VIII Computer model of part of Factor VIII, a protein that helps to clot blood after an injury

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Dogs with the bleeding disorder haemophilia A have been successfully treated by gene therapy, according to US scientists.

Two of three dogs given the experimental treatment remain free of severe symptoms more than two years on, they write in Nature Communications.

Haemophilia A is a bleeding disorder which affects one in 10,000 men.

Gene therapy may be suitable for human treatment for bleeding disorders in 10 years, says the Haemophilia Society.

Bleeding disorders

  • The two most common types of haemophilia are haemophilia A and haemophilia B, although haemophilia A accounts for most cases
  • Haemophilia A is a bleeding disorder caused by deficiency of clotting factor VIII
  • The vast majority of cases are inherited and in men
  • Symptoms include spontaneous bleeding into joints, especially the knees, ankles and elbows
  • There is no cure for haemophilia, but with treatment a person with the condition can usually have a good quality of life
  • In recent decades genetically engineered clotting factor medications have been developed for bleeding problems
  • These medications are given as an injection
  • Source: Patient.co.uk/NHS Choices

People with haemophilia A have an error in their genetic code, which means they cannot produce a protein called Factor VIII, which helps in blood-clotting.

Researchers in the US and France studied three dogs with a disorder similar to human haemophilia A.

They used a virus to carry the normal gene for factor VIII into platelets, the blood cells involved repairing damaged blood vessels.

More than two years after the gene therapy, two of the three dogs remained free of serious internal bleeding.

Lead researcher Dr David Wilcox of the Medical College of Wisconsin, Milwaukee, said the study could ultimately improve the quality of life of patients affected by haemophilia A.

Haemophilia patients usually suffer internal bleeding several times a year and have to have regular injections of synthetic clotting factor.

Start Quote

We see gene therapy as a potential long-term solution for people with bleeding disorders... we would see this on a 10-year horizon as most likely being relevant to haemophilia B and then haemophilia A”

End Quote Spokesperson Haemophilia Society

"The results indicate that performing gene replacement therapy on a patient's bone marrow cells can lead to production, storage and release of factor VIII from platelets directly at the site of an injured blood vessel to prevent uncontrolled bleeding for several years after treatment," he told BBC News.

"This could greatly improve the quality of life for the nearly one in 10,000 individuals affected by this disorder, ultimately helping the patients to save a great deal of money in medical costs."

The Haemophilia Society in the UK said it supported research into gene therapy.

In 2011, six patients with haemophilia B received gene therapy that allowed four of them to go without medication, raising hope for the future.

A spokesperson said: "We see gene therapy as a potential long-term solution for people with bleeding disorders; given the practicalities and the research already done, we would see this on a 10-year horizon as most likely being relevant to haemophilia B and then haemophilia A.

"Nevertheless, we are mindful that no therapy can be used until it has passed every hurdle including clinical testing, and we are very mindful of the dangers of raising false hopes amongst those affected by the various bleeding disorder conditions."

Other researchers have carried out gene therapy on dogs with haemophilia A using a different technique, which focuses on restoring clotting factor production in the liver.

The US researchers say this would not be applicable for all patients, such as those with liver damage.

They are applying for permission to carry out a clinical trial in the US within the next two years.

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