Gene Transfer for Human Illness Gets OK
A federal scientific panel Wednesday took a potentially major new step in gene therapy as it for the first time approved a plan to treat an illness by inserting new genes in patients.
The experimental gene therapy will be used to treat a rare and almost always fatal childhood immune deficiency disorder.
If the research is successful, the “potential for gene therapy could lead to a range of treatments for many presently incurable diseases,” said Dr. W. French Anderson of the National Heart, Lung and Blood Institute and one of the researchers on the project.
“Its basic importance is that it is the first step to something that could be a major treatment procedure over the next 10-20 years,” Anderson added. He characterized Wednesday’s approval as, “really the first step. If this is successful, it will lead to a second step and a third step.” The treatment proposal was approved by the Institutional Biosafety Committee of the National Institutes of Health. It must now be further approved by six other panels, and then must be approved by the Food and Drug Administration.
“It’s a long way from being done,” said Dr. R. Michael Blaese, a National Cancer Institute scientist who is also one of the researchers on the project.
However, Blaese predicted that “ultimately in the next century there will be an infinite number of possibilities for using genes to treat disease. In the next decade or so, you will probably see them used in the treatment of cancer, hemophilia and other diseases.”
The new therapy will treat the disease adenosine deaminase deficiency. Adenosine deaminase is an enzyme that performs an essential function in the immune system. Without the enzyme, the body’s ability to fight infection is crippled.
Currently, the only successful treatment for the disease is a bone marrow transplant from a sibling who is an identical match. However, the researchers hope to treat the disease by replacing the gene that makes the crucial enzyme.
The researchers have learned how to replace the gene in lymphocytes that are grown in tissue cultures in the lab. They thus propose to take a small amount of the patient’s enzyme-deficient blood, then isolate the lymphocytes, or white cells, from the blood. The lymphocytes are then to be grown in a tissue culture, where they increase 1,000 fold.
Next, the researchers will add normal genes to the white cells. Then the healthy white cells with the new genes will be put back into the patient.
It is presumed that the corrected white cells will then flourish, begin producing the essential enzyme, and thus restore a functioning immune system.
The therapy would not be a permanent cure, Blaese said, since the enzyme would be produced only as long as the genetically manipulated cells live.
“We don’t know how long these cells last,” he said. “Some lymphocytes, however, can live for years.”
Adenosine deaminase deficiency is “very, very rare,” Blaese said. “There are only 20 to 30 patients in the whole world.”
Last May, genetically engineered cells were injected into a human patient for the first time. The federally approved experiment was designed not to use the genes as a therapy, however, but as marker genes to track the movement in the body of cancer fighting white blood cells. Blaese was also involved in that experiment.
