Age-related macular degeneration (AMD) is one of the leading causes of blindness, affecting more than 10% of people over age 65 in developed countries. Drugs like Roche’s Lucentis, which plugs up leaky blood vessels in the eye that are characteristic of the “wet” form of the disease, can help, but there’s still a demand for treatments for “dry” AMD, which is more common and can progress to wet AMD.
A team of scientists led by the University of Southern California’s Roski Eye Institute built a retinal implant from embryonic stem cells, and they have early but encouraging evidence from a small clinical trial that it may improve visual functioning in people with advanced dry AMD. The implant is designed to mimic the retinal pigment epithelium (RPE), which breaks down as dry AMD progresses.
The team made the implant by attaching stem cells to a nonbiodegradable synthetic material that’s similar in structure and function to Bruch’s membrane, a layer of the eye adjacent to the RPE. During the study, they inserted the implant into the eyes of four people with vision loss from dry AMD and then observed them over a course of several months.
The stem cells integrated with the patients’ own retinas, and all four maintained the visual acuity they had before the procedure. One patient even showed a slight improvement. Images that the researchers took after the implants were inserted showed that the retinas of the study subjects had changed in shape—in fact, it looked as if the diminished RPE was growing back, according to the paper, which was published in the journal Science Translational Medicine.
About 1.7 million Americans suffer from AMD—a population that’s expected to grow to 3 million by 2020. Several approaches to addressing the disease are being studied, some of which have caught the attention of biotech investors.
Last year, Atlas Venture, Lightstone Ventures and OrbiMed poured $42.5 million into Gemini Therapeutics, for example, which is studying genetic variants that have been tied to an increased risk of AMD and building a drug pipeline around them. The French company Biophytis raised $12 million last year to advance trials of its drug Macuneos to treat dry AMD.
The appeal of using embryonic stem cells is that they can be coaxed to turn into many different tissues in the body. Using such cells to restore RPE in the eye has been tried before, but with limited success, the USC researchers noted in their study. In one trial, the cells didn’t seem to regenerate the normal RPE layer, while in another, the RPE cells didn’t distribute normally and the patient did not experience any improvement in vision. Nevertheless, the studies showed that stem cell therapies could be used safely in the eye, the USC researchers wrote.
None of the four patients in the USC study experienced side effects from the implant, the researchers reported. One patient was able to read more letters on an eye chart after the procedure, and two exhibited improvements in their ability to use the area of the retina that had been treated.
“Our study shows that this unique stem cell–based retinal implant thus far is well-tolerated, and preliminary results suggest it may help people with advanced dry age-related macular degeneration,” said coauthor Mark Humayun, M.D., Ph.D., director of the USC Institute for Biomedical Therapeutics and the lead inventor of the implant. The team is now planning further studies of the implant in people.