Researchers in the United States are advancing a groundbreaking stem-cell retinal implant for people with advanced dry age-related macular degeneration (AMD), a condition that currently has no approved therapy to restore lost vision.
The implant, known as CPCB-RPE1 (California Project to Cure Blindness-Retinal Pigment Epithelium 1), is now being tested in a masked, multicentre Phase 2b clinical trial at USC Roski Eye Institute to determine whether it can replace lost retinal support cells, slow disease progression and improve functional vision in patients with geographic atrophy (GA).
Dry AMD progressively destroys the retinal pigment epithelium (RPE); without functional RPE, photoreceptors degenerate, leading to irreversible central vision loss.
The CPCB-RPE1 implant combines lab-grown human embryonic stem cell (hESC)-derived RPE cells with an ultrathin synthetic parylene scaffold designed to mimic Bruch’s membrane – the natural substrate on which healthy RPE cells reside. The parylene substrate supports nutrient diffusion and cell adherence, helping the engineered layer integrate with the host retina more reliably than loose cell injections used in earlier approaches.
From early trials to Phase 2b
A first-in-human Phase 1/2a study published in Science Translational Medicine reported that in a small group of patients, the implant was successfully delivered and remained stable beneath the retina. Optical coherence tomography (OCT) showed structural signs of RPE integration, and in one subject, visual acuity improved by 17 letters, while two subjects demonstrated enhanced fixation, a key measure of central visual function.
Importantly, no eyes in the early cohort showed progression of vision loss during follow-up, and imaging indicated possible interaction between the implant and existing photoreceptors – a hopeful sign that the engineered RPE layer might support retinal function.
Building on those initial safety and feasibility data, Regenerative Patch Technologies and collaborators have now launched a larger Phase 2b randomised, assessor-masked trial. This trial plans to enroll about 24 subjects aged roughly 55–90 with advanced dry AMD and GA involving the fovea. Two-thirds of participants receive the CPCB-RPE1 implant while the rest undergo a simulated (“sham”) procedure, allowing comparison under masked conditions.
Currently, most therapies for dry AMD focus on slowing disease progression – there’s no treatment that reliably reverses damage or restores vision in advanced GA. If the CPCB-RPE1 implant demonstrates clinically significant visual improvements, it could transform the therapeutic landscape by offering a regenerative option for a condition that affects millions worldwide.
The Phase 2b study will follow patients for at least one year, using visual acuity charts (ETDRS letters), OCT imaging, fixation stability and other functional measures to evaluate whether the implant replaces diseased RPE, stabilises over time, and leads to meaningful visual benefit.
