Gene Therapy for Hemophilia Moves Ahead
June 6, 2001 -- Imagine fearing for your life every time you get a small cut. That is the reality that people with the severe bleeding disease hemophilia A face every day. Now new genetic research described in this week's issue of The New England Journal of Medicine offers hope that a unique technique combining electricity and gene therapy will correct the genetic flaw characteristic of the disease.
Hemophilia A, a genetic disorder, causes severe bleeding only in men with the disease. Women can carry the gene for the disease and pass it on to their male babies, but it doesn't make them sick. The severe bleeding is a result of a genetic abnormality: One of the substances in the blood that is responsible for clotting, called factor VIII, is missing or not working properly. When blood does not clot properly, it is very difficult to control or stop bleeding.
An estimated 15,000 U.S. men have hemophilia A. Of these, about 60% have severe disease, "where their baseline factor VIII activity levels are less than 1% of normal. They have frequent, spontaneous bleeding -- as frequently as once a week [or more]," study author David A. Roth, MD, tells WebMD. "They typically bleed into their joints. ... Chronic bleeding into the joints over time leads to joint destruction, so they are frequently crippled."
Currently, people with hemophilia A need to inject themselves with factor VIII to treat the bleeding. And it's not a cheap regimen. "Typical severe hemophilia patients who take factor VIII a couple of times a month ... can spend upwards of $100,000 to $300,000 a year" on medication, says Roth, who is director of hemophilia clinical research at the Beth Israel Deaconess Medical Center and an assistant professor of medicine at Harvard Medical School, both in Boston.
Since hemophilia A is a genetic condition, Roth and his colleagues have been exploring a way to correct the abnormality using gene therapy. The aim of gene therapy is to inject a proper, functioning gene into the cells of people carrying genetic abnormalities, such as those with hemophilia A. Typically the good gene is transported into cells with a virus because viruses have an uncanny ability to infect cells easily. In gene therapy, however, the virus is disabled so it can't cause illness. Despite this, there are some safety problems with this approach, so Roth and his colleagues decided to take an entirely new tack.
"We use electricity, a brief electrical pulse, to transfer a piece of DNA that has the factor VIII gene in it into cells that are [taken] from the patient," he says. "We do this in the laboratory, and it's called electroporation."
Specifically, the investigators take a skin sample from people with hemophilia A, and obtain some cells from the sample. Using electroporation, they insert the gene that produces factor VIII into these cells. They then make these altered cells multiply and insert them back into the patients' bodies.