Study Adds to Dispute Over Drug by Amgen

An Amgen Inc. drug at the center of a dispute over its use by Parkinson’s disease patients spurred growth of brain cells in one sufferer, suggesting that it might benefit others, according to research released Friday.

The report, written by a team of British doctors and published in the journal Nature Medicine, marked the first time that the drug GDNF had been shown to stimulate cell growth in humans.

The cells found in the study produce the brain chemical dopamine, which is in short supply in Parkinson’s patients. GDNF is thought to protect dopamine-producing cells.

The patient in the study was a 62-year-old man who had Parkinson’s disease for five years before taking the Amgen drug in a clinical trial. He showed a 75% improvement in his ability to perform daily tasks while on GDNF for nearly four years. His brain was examined after he died of a heart attack.

Amgen discontinued clinical trials of GDNF last year after some monkeys on high doses of the drug had brain damage. Amgen said it could not justify subjecting patients to additional risk because there was no evidence that GDNF was effective. The Thousand Oaks-based company also said one clinical trial showed that GDNF was no better than a placebo.

But some clinical trial participants said they experienced dramatic improvements in their ability to perform day-to-day tasks -- such as walking and writing -- on GDNF. Two groups of patients, one in New York and one in Kentucky, have sued Amgen seeking to force the company to resume providing the drug.

Experts said the latest study was very encouraging and that research on GDNF should continue. But they were divided on whether the medicine should be made available to former clinical trial participants.

William Langston, scientific director of the Parkinson’s Institute, said safety questions surrounding GDNF must be resolved. Scientists also need to understand why the one Amgen clinical trial was unsuccessful, he said.

Greg Gerhardt, a University of Kentucky scientist, said the latest study offered another reason that patients should be allowed to continue using GDNF. No available treatment for Parkinson’s promotes regeneration of brain cells, he said.

Gerhardt, who was involved in clinical studies of GDNF, said he believed that Amgen’s clinical studies were flawed and that the drug was “safe, viable and useful.”

Amgen spokeswoman Andrea Rothschild said the study “adds to our understanding of GDNF in humans.”

But Rothschild said the findings were not a surprise. Brain scans of clinical trial participants showed similar brain activity, she said, but patients’ ability to perform day-to-day tasks did not improve.

Rothschild said Amgen was continuing to study GDNF but had no plans to resume the clinical study.