Gene Therapy, experimental medical treatment that manipulates a gene or genes within cells in order to produce proteins that change the function of those cells. Gene therapy originated in efforts to treat and cure some of the more than 9,000 known genetic disorders, most of which lack an effective therapy. In the United States 1 infant in every 28 is born with a disorder caused by a defect in 1 or more of the estimated 31,000 genes found in the human body. Thousands of children and adolescents die from these diseases each year, and tens of thousands suffer lifelong disability. Although gene therapy is not an approved medical therapy to treat disease, over 400 clinical trials, experiments testing the safety and efficacy of this method on humans, have been conducted in the United States. Scientists expect that within the first decades of the 21st century, gene therapy will offer unprecedented opportunities to treat, cure, and ultimately prevent a vast range of diseases.
The original goal of gene therapy was to substitute a healthy gene for a defective one, or to repair a faulty gene, thereby eliminating symptoms of disease. But researchers have moved beyond inherited genetic disorders to treat other kinds of diseases. Today, nearly 75 percent of all clinical trials involving gene therapy are aimed at treatments for cancer and acquired immunodeficiency syndrome (AIDS). Cancer begins in genes and may be caused by an inherited defect or a mutation (permanent alteration to a gene) that causes a cell to malfunction. AIDS is caused by a virus that disrupts the genetic material of immune cells. Other new gene therapy projects are targeted at conditions such as heart disease, diabetes mellitus, arthritis, and Alzheimer's disease, all of which involve genetic susceptibility to illness. Gene therapists hope to reduce or eliminate this susceptibility. Eventually, gene therapy might help older people to regain strength in withered muscles and density in thinned bones, and to increase pumping power in their aging hearts. Some researchers predict that in the distant future the technology could be used to eliminate genetic defects from families or even to produce “designer babies” with more muscle strength, higher intelligence, sweeter dispositions, or whatever traits parents desire.
Although gene therapy offers seemingly limitless possibilities, researchers have been thwarted by many technical problems. There has only been one successful clinical trial using gene therapy—in April 2000 French researchers reported the successful use of gene therapy to treat two female infants with severe combined immunodeficiency disease (SCID), a deadly inherited disease that impairs the immune system. But even this success was marred when each child later developed a rare leukemia-like illness, thought to be a result of gene therapy. Most clinical trials of gene therapy have not resulted in enough improvement in the patient’s underlying condition to consider it an unqualified success and to justify treating large numbers of people. The extraordinary potential of gene therapy has also raised alarms among critics who warn that the technology could go too far. They note, for example, that gene therapy could offer wealthy families opportunities for genetic enhancement unavailable to the poor. More troubling still for some critics is gene therapy's potential to narrow the human gene pool, producing unknown, and possibly harmful, consequences.
