SFN: Parkinson's Disease Gene Transfer Called Safe

October 18, 2006

ATLANTA -- An investigational gene therapy for Parkinson's disease is safe and shows preliminary signs of being effective, researchers reported here.

ATLANTA, Oct. 18 -- An investigational gene therapy for Parkinson's disease appears to be "amazingly safe" after a year of follow-up, a researcher said here.

Preliminary efficacy results from a small phase I study show an overall 25% improvement in symptom scores, reported Matthew During, M.D., Ph.D., of Ohio State University, and colleagues, at the Society for Neuroscience meeting.

"We don't want to over-interpret, but we are very encouraged," Dr. During said after he presented his data.

He cautioned that the small size of the study -- just a dozen patients -- was not powerful enough to draw firm conclusions about the efficacy of the gene therapy.

The open-label, dose-escalating phase I study was intended to probe the safety of the procedure. So far, clinicians have infused an adeno-associated virus, transfected with the gene for glutamic acid decarboxylase, into the subthalamic nucleus of 12 patients with moderate to severe Parkinson's.

The theory, Dr. During said, is that the transfected gene would turn down the excessive activity of the subthalamic nucleus by increasing the region's ability to convert glutamate into GABA, the primary inhibitory neurotransmitter.

Because of fears over the safety of gene therapy, the researchers were required to treat only one hemisphere in each patient's brain, Dr. During said. Patients underwent stereotactic surgery and received one of three doses -- 3.5, 10.5, and 35 billion of the viral particles.

"Every single patient was discharged within 48 hours without fever," Dr. During said, and over the follow-up, "there was not a single adverse event related to the surgery or the gene transfer."

None of the patients had an immune reaction to the virus, as measured by antibody titers, Dr. During said, and MRI showed no brain injuries as a result of the surgery.

While the safety issue was the main endpoint of the study, the researchers also tracked changes in symptoms, as measured by the Unified Parkinson's Disease Rating Scale (UPDRS), and changes in glucose metabolism, as measured by PET.

From baseline, Dr. During said, the whole patient group had a 25% improvement in UPDRS scores, which was significant at P