Studies support gene therapy for patients with rare blindness syndrome | St. Louis Public Radio

Studies support gene therapy for patients with rare blindness syndrome

May 2, 2008

This article first appeared in the St. Louis Beacon: Studies presented at a recent meeting of the Association for Research in Vision and Ophthalmology and published online April 27 in the New England Journal of Medicine are supporting further research into gene therapy to treat a rare genetic eye disorder.

The disorder, called Leber's congenital amaurosis (LCA), attacks the retina and can lead to severe vision loss and blindness. LCA is a rare genetic condition affecting 1 in 50,000 to 1 in 100,000 of babies born each year. Eyesight begins to fail in early childhood, progressing to total blindness by the time the patient reaches his or her late 20s or 30s.

One study involving three patients treated with the gene therapy revealed signs of visual improvement, with no evidence of adverse effects from the gene therapy, in all three patients. In the other study, physicians treated three young adults, and one of these patients experienced significant improvement in visual function. The other two did not have a demonstrable improvement, which may have been due to more advanced disease.

While these results are considered very preliminary and it is important to note the small sample size of these studies, the data are encouraging and in support of continued research into gene therapy for historically untreatable genetic diseases.

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What exactly is gene therapy?

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When a patient has a dysfunctional gene that can or will lead to disease, there are three options:

  1. Do nothing.
  2. Treat the disease if or when it occurs.
  3. Try to correct the genetic abnormality.

Gene therapy is a procedure designed to correct the abnormality. The procedure is intricate in that genes directly presented to a cell usually do not function. Instead, a carrier, or vector, is crafted to deliver the gene to its target destination. Modified viruses are often used as vectors because they employ effective delivery systems by infecting cells. Clinicians modify these viruses to ensure that they will not cause disease in the recipients.

Gene therapy can be injected or given intravenously directly into a specific tissue in the body, or, a sample of the patient's cells can be removed and exposed to a vector in a laboratory. The cells containing the vector are then subsequently returned to the patient.

Scientists are working on improved ways to deliver genes and target them to particular areas.

Dr. Katherine High, a past president of the American Society of Gene Therapy and an author of one of the studies cited here, sees a lot of promise in gene therapy though clinical trials have been conducted for more than 15 years with few therapeutic results. But she adds that her group's study, "provide[s] objective evidence of improvement in the ability to perceive light, and thus lay[s] the groundwork for future studies in this and other retinal disorders."

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Genetic testing: The way of the future?

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Genetic researchers and clinicians support genetic testing for certain conditions when identification can lead to effective treatments. They also reason that the knowledge patients gain leads them to improve or maintain good health. On the other hand, some genetic conditions are untreatable and knowledge of the condition may not provide any positive options. In addition, known genetic conditions may even directly -- or indirectly -- cause issues with insurance coverage or even employment opportunities.

That's becoming a front-burner issue in Washington. The Wall Street Journal noted recently that the House may soon pass a bill that will bar employers and insurers from discriminating based on genetic makeup. President Bush is expected to sign the legislation.

Experts believe that genetic testing and gene therapy will become much more commonplace in the near future. Clinical and ethical guidelines are ripe to change. For now, the research and the promise – continues.

How it works

For more information about how gene therapy works:

The National Cancer Institute fact sheet, "Gene Therapy for Cancer: Questions and Answers"

A short description and diagram of gene therapy from the FDA:

For more on the studies, visit www.physiciansbriefing.com

Dr. Cindy Haines is managing editor of Healthday-Physician's Briefing and president of Haines Medical Communications, Inc., a full service medical communications and consulting firm. As a board-certified family physician, Haines is well-versed in all areas of health care, with particular interest in fitness, nutrition, and psychological health.

Her weekly column on health care issues will appear here each Friday, and you can listen to Dr. Haines' House Call on KTRS.

Read the studies

To obtain the abstract or full text of the studies:

Abstract -- Maguire

Full Text -- Maguire

Abstract -- Bainbridge

Full Text -- Bainbridge

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