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Researchers at University College London in England have been working on a study involving people with haemophilia, to test a gene therapy injection that could significantly reduce the risk of bleeding they face. Their findings are published in The New England Journal of Medicine.
Scientists have chosen to work on a candidate gene therapy virus, dubbed FLT180a, to treat severe and moderately severe cases of hemophilia B. This rare and hereditary disease is a genetic bleeding disorder, which particularly affects men. These have low levels of factor IX (FIX) protein, which causes blood clots to form, which help prevent or stop bleeding. The gene responsible for making the FIX protein is located on the X chromosome, so the most severe forms mainly affect men.
Production of FIX by the liver
Ten patients with hemophilia B were included in the clinical study of FLT180a which lasted a total of 26 weeks. This work revealed that a single treatment with FLT180a resulted in sustained production of FIX protein by the liver in nine out of ten patients, across four different dose levels, eliminating the need for regular replacement therapy.
In parallel, patients had to take immunosuppressive drugs for several weeks or months, to prevent their immune system from rejecting the therapy.
Reported side effects
For these patients, the usual treatment is a regular injection, usually weekly, of this FIX protein to prevent excessive bleeding. The interest of this gene therapy is to avoid weekly bites, for a treatment that would last several weeks. In nine of the ten patients, the level of FIX had increased.
And after 26 weeks, “five patients had normal levels of FIX protein, three had fairly high levels, and one patient treated at the highest dose had an abnormally high level. All patients experienced some form of adverse events, with an abnormal blood clot in the one who received the highest dose of FLT180a and who had the highest levels of FIX protein report the scientists.
Monitoring for 15 years
All volunteers are also enrolled in the long-term study, which will monitor their health for the next fifteen years following this gene therapy treatment.
According to the lead author, Prof. Pratima Chowdary, “Eliminating the need for hemophilia patients to regularly inject the missing protein is an important step in improving their quality of life. The long-term follow-up study will monitor patients for durability of expression and monitoring for late effects.”.
If confirmed by other studies, this discovery could change the daily lives of patients with hemophilia B.