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Gene therapy research targets muscular dystrophy


(CNN) -- Imagine a virus that makes you well.

Scientists at the University of Pittsburgh in Pennsylvania are zeroing in on the muscle-wasting disease of Duchenne Muscular Dystrophy using a genetically altered virus called an adeno-associated virus. Researchers hope the tiny package will eventually carry a healing punch.

"I'm very excited about this," said Dr. Xiao Xiao, an assistant professor of molecular genetics and biochemistry and lead researcher of the Pittsburgh team. "But there's still a long way to go."


Still, results using mice seem promising, said Xiao, explaining that investigators redesigned the virus to deliver a payload of dystrophin protein, an essential protein for muscle function that is missing in patients with Duchenne, the most common form of muscular dystrophy.

Injected into the calf muscles of mice lacking natural dystrophin protein, the gene-carrying virus stimulated the manufacture of the protein in 90 percent of treated tissue. Dystrophin continued to be made for at least a year -- the duration of the experiments.

"This gives us great hope that we can use this gene therapy strategy in a larger animal model of DMD and eventually treat patients within several years," he said.

Results of the preliminary study are being published in this week's Proceedings of the National Academy of Sciences.

Scientists are doing toxicity studies now, Xiao said. Still, the virus appears to be very safe. It causes no disease, and even contains stealth capability that allows it to enter the body without alerting the immune system.

"Apparently, that has some promise in being able to deliver the necessary missing DNA to the cells," said Dr. Leon Charash, a neurologist at Cornell Medical School who is chairman of the national medical advisory committee for the Muscular Dystrophy Association. "Which then can hopefully produce the normal protein and turn the disease around, arrest progress, and very possibly, (produce) a cure."

Much research remains to be done before clinical trials begin in humans, but many agree that the Xiao group's findings show promise.

"This is remarkable news for children who need such good news," said Pat Furlong, president of the Middletown, Ohio-based Parent Project for Muscular Dystrophy Research. "Miracles don't occur instantly. There is a process for research. But even being able to promote small miracles like lifting a fork, rolling over in bed or hugging someone you love -- as parents of children with this disease, we're very happy for Xiao's work."

Duchenne Muscular Dystrophy is linked to the X-chromosome and affects about one in 3,500 boys across the globe. It causes progressive muscle weakening and eventual death -- usually by age 20. Lacking dystrophin, the muscles do not work properly. They first enlarge, and then begin to deteriorate until only fat and scar tissue remain.

By delivering dystrophin protein into mouse muscle tissue using the adeno-associated virus, Xiao's team was able to preserve muscle function. Research remains to be done on how to deliver this protein throughout the body to permeate all muscle groups.

"Currently, there is no effective treatment," said Xiao. "Our treatment provides a new avenue for treating this disease, but this has to be tested in human trials to see whether it's effective. Results from animal trials cannot directly translate to humans."

Clinical trials with humans are several years away, Xiao said.

Gene therapy holds promise against cancer
August 4, 2000
FDA suspends trials at gene therapy lab
January 22, 2000
Muscular Dystrophy information and links
Study: New muscle tissue might be grown from bone marrow
March 5, 1998
Discovery brings hope for muscular dystrophy sufferers
November 27, 1996

University of Pittsburgh Health System
Muscular Dystrophy Association
Parent Project for Muscular Dystrophy Research
Proceedings of the National Academy of Sciences

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