Gene therapy trials show promise against Parkinson's disease

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.

All of the 24 patients who received gene therapy in the two separate trials received some benefit, and none had any significant side effects, according to a Los Angeles Times report on Wednesday.

However, experts and the researchers themselves cautioned patients against investing too much hope in the findings, because Parkinson's studies are notorious for showing placebo effects. More tests are needed to be sure, the researchers noted.

Parkinson's is characterized by severe tremors and rigidity in the limbs, and loss of muscle control. It results from the death of brain cells that produce the neurotransmitter dopamine, which plays a key role in transmitting commands from the brain's muscle-control centers.

In the latest two studies, both teams used the same gene therapy technology: inserting a desired gene into the common adeno-associated virus.

One team, led by Dr. Matthew J. During of the Weill Cornell Medical Center in New York, used a gene that is the blueprint for an enzyme called glutamic acid decarboxylase. That enzyme converts chemicals in the cell into a neurotransmitter called GABA, which is essential for controlling muscle movements.

Earlier studies have shown that Parkinson's disease is marked by a deficiency of GABA in a part of the brain called the subthalamic nucleus. Injecting GABA into the brain can ease disease symptoms, but the neurotransmitter is quickly cleared, limiting its benefits.

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

All the patients had an improvement of at least 25 percent on a conventional scoring system used to assess the severity of Parkinson's symptoms. Four of them improved at least 37 percent and five others 40 percent to 65 percent, and the benefits have persisted for a year, the team reported at a neuroscience meeting on Tuesday and last week.

Brain imaging showed an increase in metabolism on the side where patients received the gene therapy, and the amount of increase correlated with the degree of improvement in symptoms, During said.

In the second study, the researchers of the University of California, San Francisco used the gene for a growth factor called neurturin, which is closely related to another growth factor known as GDNF.

Studies have shown that injecting GDNF into the brain section known as the putamen can impede, and possibly reverse, the loss of dopaminesecreting cells.

Twelve Parkinson's patients were injected with one of two doses of the gene therapy agent. Patients receiving the lower dose had a 40 percent decrease in Parkinson's symptoms, and those receiving the higher dose had a 50 percent reduction, the researchers said.

Source: Xinhua