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Eye Cell Transplants Safe in Parkinson’s Patients

Thursday December 15, 2005

Michael Smith

December 12, 2005(MedPage Today) - MedPage Today Action Points

Advise patients who ask that this is a pilot, open-label study, based on promising pre-clinical data, on the effect of transplanting human retinal pigment epithelial cells on Parkinson’s symptoms.

As a pilot study, the main objective is to measure safety and tolerability, which appears to be good.

Note, however, that the efficacy results are sufficiently promising that the investigators are beginning a randomized, placebo-controlled, double-blind study. Implants of human retinal pigment epithelial cells as a therapy for Parkinson’s disease have improved symptoms in six relatively young patients and appear to be well-tolerated and safe, according to researchers here.

The implants appear to be improving movement both clinically and statistically, Natividad Stover, M.D., of the University of Alabama here and colleagues reported in an open-label pilot study in the Dec. 13 issue of Archives of Neurology.

Based on pre-clinical studies, which showed that the retinal cells produced levodopa and improved symptoms in animal models of the disease, Dr. Stover and colleagues recruited six patients, with a median age of 52.2 years, from the university’s movement disorders clinic.

The patients had been suffering from Parkinson’s for a mean duration of 10.2 years. Their mean baseline score on the Unified Parkinson’s Disease Rating Scale (UPDRS) total was 118 without medication. On the scale, 0 represents no disability, while 199 is the worst possible score.

Human retinal pigment epithelial cells, Dr. Stover and colleagues noted, have several advantages for this potential therapy. They are easily extracted from post-mortem eyes, grown easily in culture, and can be stored frozen for long periods.

Moreover, when they’re attached to a gelatin microcarrier, they can be transplanted into the brain, where -- even in the absence of immunosuppressive therapy -- they can live for an extended period of time, Dr. Stover and colleagues noted.

Using magnetic resonance imaging-guided stereotactic surgery, the researchers implanted approximately 325,000 retinal pigment epithelial cells in five spots in the postcommissural putamen, on the side of the brain opposite to each patient’s most affected side. No immunosuppression was used.

The safety follow-up included clinical examinations, elicited adverse events, vital signs, brain magnetic resonance imaging, neuropsychological evaluations, and standard laboratory studies.

A postoperative brain MRI in all patients confirmed the accurate placement of the implants, and follow-up MRIs at three, six, 12, and 24 months showed no abnormal signs of inflammation or rejection, Dr. Stover and colleagues reported.

One patient had a small brain hemorrhage near one of the implants, without serious consequences. Another patient developed depression and suicidal ideation 14 months after the implant; medical treatment resolved the issue.

Treatment-related adverse events included transient dyskinesias and visual hallucinations, which were resolved by adjusting anti-Parkinson’s medication, the investigators report.

The patients also saw their symptoms improve, the researchers found:

Over the first 12 months, the UPDRS motor score, measured when patients were off their medications, improved 48% on average, which was statistically significant at the p=0.006 level. The improvement was sustained over the full two years of the study, at a slightly lower level.

The UPDRS total score also showed significant improvement, of about 35% on average (also significant at the p=0.006 level.)

"Improvement was also observed in activities of daily living, quality of life, and motor fluctuations," the authors noted.

On the basis of these results, the researchers have begun a randomized, double-blind, placebo-controlled study, the authors said.

The authors pointed out that the results were obtained in relatively young patients and it is possible that the results may not be as good in older patients. In addition, as there was no control group, it is possible that placebo effects may play a role in this open-label study.