Gene therapy trials halted

Gene therapy trials halted – Health

WASHINGTON, D.C. — The U.S. Food and Drug Administration (FDA) has put a temporary hold on 27 gene therapy experiments in this country. The action was taken after two children in France who had been treated with gene therapy developed a life-threatening illness.

Gene therapy is relatively new means of helping people who have disorders caused by defective genes. The patient is injected with a healthy form of the gene, which takes hold in the patient’s cells and replaces the defective gene.

The two French boys who became sick had been cured several years ago of a genetic disorder call ed severe combined immunodeficiency (SCID). People with SCID lack the ability to fight infectious diseases caused by viruses and bacteria. Most babies born with SCID die within their first year. SCID is also known as “bubble boy syndrome,” named after David Vetter, a Houston, Texas, boy with SCID who survived for 12 years inside a protective, germ-free plastic bubble. Bubble boy syndrome is the only disease that has yet been cured with gene therapy.

When SCID is treated with gene therapy, a healthy gene is put inside a type of virus called a retrovirus, which is then injected into the body. The retrovirus invades the body’s cells and inserts the healthy gene into them. The 27 gene therapy experiments suspended by the FDA all involved the use of retroviruses to treat a variety of other genetic illnesses. The FDA allowed dozens of other gene therapy experiments to continue because the genes in those experiments are delivered by cold viruses, not retroviruses.

Some critics of gene therapy experiments have charged that human trials have gone ahead too quickly. The critics have expressed concern that retroviruses inserted into human cells could switch on genes that cause cancer.

The two French boys who became sick after their SCID was cured with gene therapy developed a condition similar to leukemia. Leukemia is a type of cancer in which the body produces an abnormal number of faulty white blood cells. Both boys have been treated for the condition and are in stable condition.

“Gene therapy is one of the promising therapies of the future,” Phil Noguchi, the FDA’s chief of gene therapy research, told the Chicago Tribune. “We want to make sure that people understand that we are here to make sure that gene therapies are developed and that it’s done safely. But we also understand that there are risks and there are benefits in every trial.”

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