Gene Therapy for Canavan Disease
Canavan disease is an autosomal recessive disease which involves two mutated copies (one from each parent) of the gene that produces aspartoacyclase, an enzyme that plays a role in myelin production. The white matter in the brains of patients with Canavan disease eventually degenerates into spongy tissue riddled with microscopic fluid-filled spaces. Symptoms include mental retardation, loss of previously acquired motor skills, feeding difficulties, abnormal muscle tone (floppiness or stiffness), an abnormally large, poorly controlled head, paralysis, blindness, and/or hearing loss.
In the first first clinical gene-transfer study of its kind to receive funding from the National Institutes of Health, scientists are trying to deliver adeno-associated viral particles carrying the aspartoacyclase gene directly to the neurons in the brain. Thus far, among the 10 study participants, all of their brains have stopped atrophying, none have died, and at least one has lived past the average life expectancy of 10 years.
The latest study participant is Ariel Coover who is only 3 1/2 months old and is still asymptomatic. Her older sister, Amber, died from Canavan disease in 2000 and her parents found out via prenatal genetic testing that Ariel was also affected.
“We don’t know what to expect,” Dan Tagle, program director for neurogenetics at the National Institute of Neurological Disorders and Stroke said. “Is the vector system the right delivery system to use? Will the brain tolerate the virus? It’s still research in some ways, because we’re still trying to figure it out.”
The study is not designed to test effectiveness, he said. The treatment’s safety is the main question, and the surgery includes serious risks. But, for the Coovers, the potential benefit was too great to pass up.
“The biggest risk is she could die,” Walter Coover, Ariel’s father, said. “And she was going to die anyway.”
Philadelphia Inquirer, September 17, 2005
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POSTED IN: Genetics of Disease
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