Gene Therapy Breakthrough for Hemophilia B

   An article in the New York Times from December 10, 2011 says that British researchers treated 6 patients with Hemophilia B by giving them a corrected form of the defective gene that causes the disease. Hemophilia B is the first widespread disease that seems to be treatable through gene therapy. Gene therapy up until now, has not been very successful with most rare diseases. In the past, it has caused cancer in some patients, or even death.

     Gene therapy is the replacing of a defective gene in any genetic disease by using the intact version of the gene. The problem that researchers have faced is getting the gene into human cells. When using a virus to get the genes into the humans, the immune system usually kills the viruses before the gene can take effect. Finally, after many improvements developing this gene therapy, success has come with Hemophilia B. The way they were successful in getting the viruses into the patients was by using a virus that goes into the liver. Because Hemophilia B comes from a defect in the gene for Factor IX, researchers had to find a way to correct Factor IX. Hemophilia B is virtually only in men because Factor IX lies on the X chromosome, which they only have one copy of.  This treatment enables the body to produce correct copies of Factor IX.

     Patients using this new form of gene therapy have been able to produce good Factor IX for almost two years on their own. This means treatments that were costing up to $300,000 a year will now only cost $30,000 an injection. One problem they have to take care of is that they must always change the form of virus they use so that the patient will not have developed antibodies for it. Researchers are trying to find low levels of a virus that will not trigger an immune system to attack it. They feel that they are very close to finding this and will have an effective genetic treatment for Hemophilia B in a few years.