A new gene-therapy technique to treat Parkinson’s patients could improve motor function by as much as 65 percent without side effects, according to results from a Phase 1 clinical trial.
Researchers at New York Presbyterian Hospital/Weill Cornell Medical Center used a benign form of a virus, altering it so that it could transmit only one gene to host cells. The gene used in the study—glutamic acid decarboxylase (GAD)—produces GABA, a neurotransmitter that inhibits excessive neuronal firing. GABA levels are reduced in Parkinson’s patients, which causes problems with motor function.
The gene-bearing virus was injected into one side of the brain in the subthalamic nucleus, an important regulatory center. Participants in the study, which included 11 men and one woman with Parkinson’s, were divided into groups of four and given low-, medium- or high-dose injections of the GAD gene.
Within three months of the surgery, participants reported a significant lessening of symptoms. The motor functions that improved were controlled by the side of the brain that received the injection, suggesting that the gene therapy worked.
The study, published in the June 23 issue of The Lancet, was led by neurologists Michael Kaplitt at Cornell and Matthew During at Ohio State University Medical Center, formerly at Cornell.
Despite the results and the lack of any side effects from the gene therapy, the long-term effects are unknown, A. Jon Stoessl of the University of British Columbia wrote in an accompanying commentary.
Stoessl also raised concerns about the risk of introducing a virus to neighboring structures in the brain. During and his colleagues plan to address this and other issues during the next stage of their studies, which will include a larger study focusing on whether the gene therapy is effective.