Muscular Dystrophy Symptoms Reversed In Mice By 'Antisense' Drugs

Researchers have successfully reversed symptoms of the most common form of adult muscular dystrophy in mice, pointing toward a possible treatment for humans.

In a paper published in the journal Nature, scientists from the University of Rochester Medical Center and two drug companies -- Isis Pharmaceuticals and Genzyme -- describe how they attacked the disease by targeting "toxic" genetic messengers.

"For 20 years, we studied myotonic dystrophy, hoping that someday we would learn enough to spot its Achilles heel," University of Rochester neurologist and senior author Charles Thornton said in a statement Wednesday. "This work comes close to doing that."

Myotonic muscular dystrophy affects about 35,000 people in the U.S. Patients suffering from the disease find their muscles wasting away, leaving them weak. They also often cannot relax their muscles due to prolonged muscle contractions, meaning it can be hard for them to release their grip on a handle or move their jaw.

The disease is caused by a genetic mutation that causes abnormal messenger RNA -- the genetic courier that's transcribed from DNA -- to accumulate in the nuclei of cells. That buildup causes an intracellular traffic jam that interferes with multiple proteins, including MBNL1, which is involved in regulating the electrical control of muscles.

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To combat the toxic messenger RNA, the researchers used a class of drugs called "antisense compounds." These compounds bind to abnormal RNA and wave down RNase H, an enzyme that chops up RNA.

Mice that were given the antisense compounds twice a week for four weeks had reduced symptoms for up to one year, according to the paper. The researchers say it's still unclear whether the drug will work in humans, but they are cautiously optimistic.

What's especially gratifying is that antisense drugs also seem to work better in the nucleus, so it seems as though the mechanism of myotonic muscular dystrophy may be the key to defeating it, according to Thornton.

"I know it is unscientific for me to think so, but I can't help but see a little glimmer of 'medical justice' in this approach," Thornton said.

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Muscular Dystrophy Symptoms Reversed In Mice By 'Antisense' Drugs