updated 7/1/2005 5:41:05 PM ET 2005-07-01T21:41:05

A drug withdrawn from clinical trials because of safety concerns was helping regrow nerve fibers in the brain of a man with Parkinson’s disease, scientists report.

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The finding probably will renew debate over the drug, GDNF. It had offered encouragement to people with Parkinson’s who reported improvement when using it in trials. But the drug was withdrawn by the manufacturer, Amgen, this year.

Some of those patients in the trial sued Amgen to get continued supplies of the drug. They were turned down by a federal judge in New York in June. A second suit is pending.

Seth Love, Steven S. Gill and colleagues at Frenchay Hospital in Bristol, England, report in Monday’s issue of the journal Nature Medicine that an autopsy of the brain of one of the patients who received the drug in an early trial shows that nerve fibers that are lost in the disease were growing back.

The patient, a 62-year-old man, died of a heart attack.

Love said in a telephone interview that patients in the trial showed improvement and the autopsy findings indicate how that improvement was achieved.

In Parkinson’s, brain cells that produce the chemical dopamine, crucial for brain cell communication, are destroyed. The result is symptoms such as trembling in hands, arms, legs, jaw, and face; rigidity, or stiffness of the limbs and body; slowness of movement; and impaired balance and coordination.

GDNF, which stands for glial cell line-derived neurotrophic factor, is a natural growth agent needed by brain cells to produce dopamine.

The autopsy shows “for the first time” that infusion of GDNF into a portion of the brain called the putamen causes a regrowth of nerve fibers, Love reported.

Robin Elliott of the Parkinson’s Disease Foundation, said the report was “obviously very significant and exciting.”

Michael Hutchinson, a neurologist at New York University who conducted one of the clinical trials of the drug, said he believes GDNF was useful for Parkinson’s and was surprised when the manufacturer decided to withdraw it.

Andrea Rothschild, an Amgen spokeswoman for Thousand Oaks, Calif.-based Amgen, said the company was not surprised by the finding and had seen similar indications on PET scans.

“It’s not clear that you can attribute that neural growth to any kind of clinical outcome,” she said.

Amgen cited safety concerns when it withdraw the drug. Rothschild said there were two issues: Some patients developed antibodies to GDNF, and a parallel study involving monkeys showed some with brain damage.

Hutchinson suggested the brain damage might have been a result of sudden withdrawal of the drug rather than the drug itself.

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