Protein Eye Implant Found Safe as Potential Treatment for Retinal Diseases
A capsule filled with cells that produce a protein called ciliary neurotrophic factor (CNTF) can be implanted safely in the eye. This method is seen as a potential treatment for some blinding retinal diseases, such as retinitis pigmentosa (RP). This is the major finding of a study published in the March 7, 2006 issue of the Proceedings of the National Academy of Sciences. This is the first time that cells whose genes have been altered to produce CNTF have been implanted in human eyes.
The clinical trial was conducted at the National Institutes of Health (NIH) by Paul A. Sieving, M.D., Ph.D., director of the National Eye Institute (NEI) and colleagues at the National Institute on Deafness and Other Communication Disorders (NIDCD), Neurotech USA, and the EMMES Corporation.
The CNTF capsules were surgically implanted into one eye of each of 10 participants who had vision loss from RP. Vision loss is caused by the death of retinal rods and cones, the light-sensitive cells inside the back of the eye.
When the implants were removed after six months, the cells were still producing the CNTF protein at levels known to be therapeutic in our animal models of retinal degeneration. In addition, although the trial was not designed to assess changes in vision, the study reports that three of seven patients achieved and maintained improved visual acuity of two to three lines on a standard eye chart.
This improvement in visual acuity may be due to an improvement in metabolic activity in damaged cone photoreceptors that allows them to resume their light-processing function. Previous animal studies have shown CNTF to be effective at slowing down retinal degeneration. In this clinical trial, CNTF was found to be safe for the human retina, even when the retinal cells are severely damaged.
"This approach of implanting capsules filled with genetically-altered cells to rescue degenerated cells may be applicable to other non-genetic eye diseases, as well as other conditions such as those affecting the central nervous system," Dr. Sieving concluded.
Citation:
Sieving PA, Caruso RC, Tao W, Coleman HR, Thompson DJ, Fullmer KR, Bush, RA. Ciliary Neurotrophic Factor (CNTF) for Human Retinal Degeneration: Phase I Trial of CNTF Delivered by Encapsulated Cell Intraocular Implants. Proceedings of the National Academy of Sciences 103: 3896-3901, 2006.
Proceedings of the National Academy of Sciences:
http://www.pnas.org/cgi/content/full/103/10/3896
