An experimental new gene-therapy technique has proved it can safely deliver a healthy gene and shows promise as a treatment for hemophilia, researchers report.
Hemophilia patients do not have enough of a blood clotting protein because of a defect in a gene. The goal of gene therapy is to get the body to produce the protein by putting normal genes back into the patient.
Until now, viruses have been used to ferry genes into the body. But this carries some risk. The new method avoids these hazards by putting the gene into cells taken from the patient.
Researchers at Boston's Beth Israel Deaconess Medical Center tested the gene-transfer technology and reported their findings in Thursday's New England Journal of Medicine. The technique was developed by the Cambridge, Mass.-based Transkaryotic Therapies Inc., which funded the study.
``I think it is extremely exciting for those who live with hemophilia,'' said Mark Skinner, who has the disorder and is president of the National Hemophilia Foundation. ``As the field of gene therapy develops, it will offer a vastly improved treatment and hopefully ultimately a cure for those with a bleeding disorder.''
Researchers tested the method on six men with severe hemophilia A, the most common type of the inherited disorder that afflicts about 15,000 men in the United States. They removed a small piece of skin from the patient's arm and used a brief electric pulse to put the blood clotting factor VIII gene into the cells. The genetically modified cells were screened and later injected into fatty tissue in the patient's belly.
Dr. David A. Roth, who led the study, said the method proved to be safe and there were no side effects. While designed to look at safety issues, the study also showed promising signs that the treatment can work, Roth said.
Four of the six patients had modest increases of blood clotting protein. They also had less bleeding or used less supplemental protein to control bleeding. Two of the patients had no episodes of spontaneous bleeding in their joints for 10 months; such bleeding was a frequent occurrence for them before treatment.
``In gene therapy, if you could just get their levels up a little, you can make a major difference,'' Roth said. ``You can really improve their quality of life and how they do.''
The researchers said the non-viral technique has potential advantages over gene therapy that uses viruses. They said it minimizes the risk of immune reactions, infections and genetic mutations that may be associated with the use of viruses. Doing the transfer outside the body also allows researchers to screen the genetically modified cells before putting them into patients, Roth said.
``We may well ultimately find out that multiple gene therapies are needed because different ones are right for different populations. There may not be one single answer for everybody,'' Skinner said. ``So seeing research advance in the non-viral area as well as using (viruses), I think, is extremely encouraging.''