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April 18, 2002


Retinal Cell Implantation Shows Promise and Improvement in Advanced Parkinson's Disease Patients – A One Year Follow-Up

An innovative procedure, in which retinal cells are implanted in the brains of patients with advanced Parkinson's disease (PD), is showing promise, according to a group of Emory University researchers. In a one-year follow-up report to be given at the American Academy of Neurology 54th Annual Meeting in Denver, Colo., on April 17, Ray Watts, M.D., professor of neurology, Emory University School of Medicine, says patients involved in this study have improved 30 to 50 percent following treatment. Dr. Watts will lead the discussion on the safety and efficacy of this pilot study at the meeting.

In this phase one trial, Dr. Watts and colleagues implanted retinal pigment epithelial (RPE) cells, cells found in the back of the eye, into the brains of six patients with advanced PD. These cells produce L-dopa, a chemical that the brain uses to make dopamine. Dopamine is a neurotransmitter produced by neurons in the brain that is found in steadily decreasing amounts as the disease progresses. The implanted retinal cells serve as a new source of dopamine production in these patients.

"This is the first human intracerebral retinal cell implantation study in the world and we are encouraged by the results so far," Dr. Watts reports. "We've been following these six participants for over a year, and we've found they've improved, on average, 30 to 50 percent in various measures of motor function." Improvement is being seen in their tremor, stiffness, slow movement and balance, the most common motor functions affected by Parkinson's disease. Half of the participants are also showing improvement of dyskinesia, which are involuntary movements that are a result of medications.

The epithelial cells used in the trial were taken from one human eye donor. Hundreds of millions of cells were grown in cell culture from the donor cells, and they were attached to tiny gelatin beads (or microcarriers) prior to implantation. Surgeons then implanted 325,000 cells in each participant during MRI-guided stereotaxic surgery. The cells were implanted in five different areas of the striatum, the part of the brain that controls movement. The cells then live on the gelatin beads in the striatum, continually making L-dopa. The novel cell product is called Spheramine®, developed by Titan Pharmaceuticals, Inc. and uses Titan's cell-coated microcarrier (CCM™) technology.

Epithelial cells reproduce on the surface in which they grow, similar to a layer of skin. Once the cells have covered the surface, they stop growing, so overproduction of these cells does not occur. Overgrowth of embryonic stem cells implanted in the brains of some parkinsonian rodents has raised concern about the future of that approach. Until this overgrowth has been controlled, this would not be investigated in humans with PD.

Participants in the Emory study only had cells implanted on one side of the brain, focusing on the side that was most affected by the disease. This implantation procedure is still investigational and has not been approved by the Food and Drug Administration (FDA) for general use.

Researchers say because it is performed stereotaxically with a needle, there is less risk of infection or bleeding. Participants did not have to take immune suppressant drugs, because the brain is relatively immune protected and these cells appear to have low tendency to produce an immune response when implanted with this technique.

The research for this Phase I, open-label trial was supported by a grant from Titan Pharmaceuticals, Inc. and the National Institute of Neurological Disorders and Stroke (NINDS), a division of the National Institutes of Health (NIH).

"This new cell implantation therapy appears to be safe and well tolerated in participants 12 to 15 months following implantation," says Dr. Watts. "We will continue to follow these six participants for months to come. We hope to begin a Phase II controlled trial soon implanting RPE cells on both sides of the brain, instead of just one side."

Parkinson's disease is a progressive disorder of the central nervous system affecting over one million people in the United States.

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