Two patients with advanced wet age-related macular degeneration (AMD) in a Phase I clinical trial demonstrated improved visual acuity sustained for one year after a sheet of retinal pigment epithelial (RPE) cells derived from embryonic stem cells was transplanted under their retinas. Each patient had one eye treated. Vision improvement for one patient was 29 letters or about 6 lines on an eye chart. The other had a gain of 21 letters or about 4 lines.
Known as the London Project, the human study is taking place at Moorfields Eye Hospital in the UK. The study will enroll a total of 10 patients. Results of the study were published online in the journal Nature Biotechnology.
In the retina, RPE cells provide support — namely waste management and delivery of nutrition — to photoreceptors, the retinal cells that make vision possible. The RPE cells exist as a layer in which photoreceptors are nestled. In AMD, RPE cells degenerate first. The loss of RPE eventually leads to loss of photoreceptors and vision.
Researchers believe that transplanting healthy RPE cells into an affected retina may reactivate photoreceptors that are in a dormant, nonfunctional state.
In the London Project clinical trial, the RPE cells are placed on a synthetic membrane — also known as a patch — so they can be handled easily and transplanted safely underneath the fovea as they naturally occur. The fovea is a tiny pit in the central retina that provides the sharpest vision. Researchers also developed a delivery tool to minimize damage to the patch as it is transplanted.
“While this trial is still at a very early stage, the vision improvements thus far are encouraging,” says Stephen Rose, PhD, chief scientific officer at the Foundation Fighting Blindness. “We look forward to additional reports from the investigators as more patients are treated.”
Though the clinical trial is for patients with advanced wet AMD, the researchers plan to evaluate the treatment in those with early dry AMD.