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 Two clinical trials testing retinal cells derived from human embryonic stem cells report positive preliminary results. A paper published recently in The Lancet says that the cells appear to be safe four months after being injected into the eyes of two blind patients, and also describes visual improvements in the patients.
This isn’t the first trial of human embryonic stem cell-based therapies, nor is it the first human data on these therapies. It is, however, the first – albeit early – data from the only ongoing clinical trial of such a treatment. One trial involves patients with 'dry' age-related macular degeneration (AMD), the leading cause of blindness in the developed world, whereas the other is focused a juvenile form of degenerative blindness called Stargardt’s macular dystrophy, neither of which are treatable.
The results reported are from the first patient from each of the two trials, both of which will eventually enroll a dozen patients. Final results are expected in 2013. The early-stage safety trials are sponsored by Advanced Cell Technology (ACT), a stem cell firm in Marlborough, Massachusetts.
The patients had one of their eyes implanted with cells called retinal pigment epithelial (RPE) cells, which were derived from human embryonic stem cells. The implanted RPE cells are meant to engraft in the retina and replace native RPE cells that have died off as a result of the disease. RPEs provide support to the light-sensing photoreceptors in the retina, and so the ultimate goal is for the new RPE cells to rescue dying photoreceptors and slow or even stop further vision loss. The team conducting the trials, led by Steven Schwartz at the University of California, Los Angeles, reports finding no safety problems with the cell implants in the two patients. They did not see signs of, for example, tumour or other abnormal growths, retinal detachments, or immune rejection of the cells.
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