Two studies give gene therapy for Parkinson's disease good reports

The first studies of human gene therapy for Parkinson's disease have shown that the technique is safe and can reduce symptoms for patients, two groups of researchers have reported.

Each of the 24 patients who received therapy in the two separate trials received some benefit and none had significant side effects, researchers reported at neuroscience meetings Tuesday and last week.

Gene therapy has a tarnished reputation because of problems encountered in trials against other diseases, said Katie Hood, deputy chief executive officer of the Michael J. Fox Foundation for Parkinson's Research.

The Food and Drug Administration temporarily halted gene-therapy trials in 1999 after an 18-year-old being treated for a mild genetic disorder died after a violent reaction to the procedure. Trials were halted again in 2005 after three French children being treated for inherited immunodeficiency disease developed leukemia and one of them died.

Experts and the researchers themselves cautioned patients against investing too much hope in the findings. Only when the techniques are tested in controlled trials will researchers be able to determine whether the benefits are real and long-lasting.

Parkinson's, which strikes as many as 100,000 Americans each year, is characterized by severe tremors and rigidity in the limbs and loss of muscle control. Although its cause is unknown, the disorder results from the death of brain cells that produce a neurotransmitter called dopamine, which plays a key role in transmitting commands from the brain's muscle-control centers.

The two teams used the same technology for performing gene therapy, inserting a desired gene into a common but harmless virus called adeno-

associated virus (AAV).

The genes they used were quite different, however.

One team, led by Dr. Matthew During of the Weill Cornell Medical Center in New York, used a gene that is the blueprint for an enzyme essential for the production of the neurotransmitter called GABA.

During's team injected one side of the brain of 12 patients with one of three different concentrations of the gene-therapy agent.

He told an Atlanta meeting of the Society for Neuroscience on Tuesday that all 12 patients had an improvement of at least 25 percent on a conventional scoring system used to assess the severity of Parkinson's symptoms, nine had an improvement of at least 37 percent and five had an improvement between 40 percent and 65 percent. The benefits have persisted for a year.

The second study, led by Dr. William Marks Jr. of the University of California, San Francisco, used the gene for a growth factor called neurturin, which studies have suggested could impede the loss of dopamine-secreting cells.

Marks and his colleagues injected each of 12 Parkinson's patients with one of two different doses of the gene-therapy agent. He reported last week at a Chicago meeting of the American Neurological Association that patients receiving the lower dose had a 40 percent decrease in Parkinson's symptoms, while those receiving the higher dose had a 50 percent reduction. The researchers have monitored the patients for nine months.