British researchers have successfully treated six patients suffering from hemophilia B (blood-clotting disease) by injecting them with the correct form of a defective gene.
Researchers at St. Jude Children's Research Hospital in Memphis, prepared a good version of
the human gene for the clotting agent known as Factor IX. Research team led by Dr. Amit C. Nathwani of University College London recruited and treated the patients by infusing the delivery virus into their veins, while researchers at the Children's Hospital of Philadelphia monitored their immune reactions. The corrected version was delivered via the
virus to the patient's liver cells. They are the only cells in the body capable of producing certain clotting factors missing or deficient in people with hemophilia.
It was seen that a single injection enabled 4 out of the 6 patients to produce small amounts of clotting factor (Factor IX) on their own which was enough stop the usual treatment, injections of Factor IX concentrate prepared from donated
blood. The other 2 patients required to continue with the protein injections, but less frequently. In fact the patients continued to produce their own Factor IX for up to 22 months. The treatment was more efficient as the research team had treated the patients with steroids to
suppress immune system attacks on the virus.
With a view to ascertain the highest dose that does not set off an immune system attack, 20 more patients will be treated to assess the best dose of the virus. Scientists hope that if everything goes well, this genetic treatment for hemophilia B could be available for widespread use in a couple of years.
The current treatment costs a patient about $300,000 per year, with a possible lifetime cost of $20 million. But the new gene therapy injection costs just $30,000.
The study is reported in 'The New England Journal of Medicine'.