The trials involved administering glial cell-derived neurotrophic factor (GDNF) into the patient’s brain — via a port in the side of the person’s head — every four weeks for nine months. GDNF is a small protein that promotes the survival of many types of neurons.
Forty-one patients were given either GDNF or a placebo in hopes of regenerating dying brain cells or reversing the Parkinson’s.
Because both groups showed improvement, researchers weren't able to credit the GDNF. However, positron emission tomography, or PET, scans showed "the drug then engages with its target, dopamine nerve endings, and appears to help damaged cells regenerate or have a biological response," principal researcher Alan Whone said.
"The spatial and relative magnitude of the improvement in the brain scans is beyond anything seen previously in trials," said Whone, a Parkinson's specialist at Britain's Bristol University who co-led the trial.
"This represents some of the most compelling evidence yet that we may have a means to possibly reawaken and restore the dopamine brain cells that are gradually destroyed in Parkinson's," he said.
Parkinson’s is a neurodegenerative disease that causes tremors, muscle stiffness, and movement and balance problems. There is no cure.
Researchers were also encouraged by the use of the port implant, which they said could be implemented to treat other diseases.
"This trial has shown that we can safely and repeatedly infuse drugs directly into patients' brains over months or years," said Dr. Steven Gill, lead neurosurgeon for the trials. "This is a significant breakthrough in our ability to treat neurological conditions, such as Parkinson's, because most drugs that might work cannot cross from the blood stream into the brain due to a natural protective barrier."
Researchers said the port implant could also be used to administer chemotherapy to people with brain tumors, or to test new drugs for Alzheimer's and stroke patients.
The study was published Tuesday in the Journal of Parkinson's Disease.