Five British patients with advanced Parkinson's disease have shown "remarkable" improvement after injections of a protein directly into the brain.
The experiment, which began more than 18 months ago and is reported today in Nature Medicine, was a simple, phase-one clinical trial to determine not whether the technique was promising but whether it was safe.
A team led by Clive Svendsen, of the University of Wisconsin-Madison, pumped a growth factor, known as GDNF, through a catheter into a precise region of the brain of each of the selected patients at the Frenchay hospital in Bristol.
According to the tests, patients showed a 39% improvement in motor skills after an injection and an improvement of more than 60% in accomplishing routine activities.
"Nobody has ever put a growth factor directly into the brain before. Our main concern was the safety issue, and it is important to keep in mind the limited scope of the trial. But the clinical results were impressive," Dr Svendsen said.
Parkinson's disease affects the nerve cells that produce the chemical dopamine, important in the control of movement. The first signs of the disease include slower movement, stiffer muscles and tremor. Many patients find it difficult to focus attention. The boxer Muhammad Ali and the actor Michael J Fox, are famous victims, but there are hundreds of thousands of sufferers in the UK and more than a million in the US.
GDNF stands for glial cell line-derived, neurotrophic factor. Tests in rats and monkeys had already shown that the factor could help improve the dopamine-producing cells in those mammals' brains.
Every day, for 18 months, the US-British scientists pushed 40-millionths of a gram of the protein into a part of the brain called the putamen. The protein was absorbed by the cells nearest the catheter tip and, they believe, drawn deeper into the brain where the dopamine-producing nerve cells reside.
The treatment either made the dopamine cells work better or encouraged the "sprouting" of new ones. Either way, the five patients ended up with more dopamine - and more control over their own limbs and lives. They also showed less tremor from L-dopa, the drug most often used to treat the disease.
A cure remains a long way off, but the Frenchay results raise hopes. "This is the first paper to show that a growth factor directly administered to the brain has any physiological effect on humans. It might be an ideal molecule. The key thing we now know is that it is safe," Dr Svendsen said.
