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Gene-Agnostic Therapy Sees 3-Year Gain in Severe Vision Loss
Richard Mark Kirkner
May 11, 2026
A synthetically engineered gene therapy designed to restore some retinal function in people with severe vision loss has been shown to bring sustained improvement in visual function out to 3 years, to a point where patients can make out objects on a table or walk down a hallway, according to new research presented at the Association for Research in Vision and Ophthalmology (ARVO) 2026 Annual Meeting.
The treatment, MCO-010, is a protein designed to infuse light-sensitive proteins, called multi-characteristic opsins, into otherwise dormant retina cells of patients with retinitis pigmentosa(RP). MCO-010 is delivered with a gene therapy vector into bipolar cells in the retina by an intravitreal injection that can be given in the office, whereas other gene therapies require placement below the retina in a procedure done in an operating room.
“This is one of the first optogenetic trials to achieve its primary endpoints,” Vinit Mahajan, MD, PhD, a vitreoretinal surgeon who directs the Molecular Surgery and Omics Laboratory at Stanford University , who presented 3-year results of the REMAIN phase 2b/3 trial of MCO-010.
MCO-010 is engineered to detect different color wavelengths of light, Mahajan added. “This single engineered opsin is doing the job of four natural opsins in the human eye,” he said.
Eyes treated in the study had “very, very low vision” in the range of hand motions or light perception, Mahajan said, with Snellen equivalents ranging from 20/1700 to 20/3000. “You cannot do standard gene therapy or cell therapy in these patients because there are no cells to rescue,” he said. “They’ve lost their photoreceptors; they’ve lost their retinal pigment epithelium cells.”
REMAIN 3-Year Results
REMAIN is an extension trial of the phase 2b RESTORE trial, in which patients had a statistically significant improvement in best-corrected visual acuity (BCVA) at 1 year of.337 LogMAR (P = .021 ) in the high-dose group and.382 LogMAR in the low-dose group (P = .029) compared with that in the sham group — the equivalent of three lines of improvement on the Snellen chart.
In REMAIN, the 3-year BCVA improvement was.264 LogMAR in the high-dose group and.453 LogMAR in the low-dose groups, Mahajan said. REMAIN enrolled 18 patients in the treatment group and nine in the sham group. BCVA in a “handful” of REMAIN patients improved by six lines, Mahajan said.
“The patients that actually had the best improvement actually began with better vision and better retinas,” Mahajan said. RESTORE found patients who had RP for 30 years or less responded more favorably to the treatment at week 52 than those who had the disease longer.
REMAIN also found improvement in BCVA correlated with retinal transduction and expression of multi-characteristic opsin, based on fluorescein autofluorescence imaging, and less retinal thinning as measured with optical coherence tomography.
Safety outcomes were similar between the one- and three-year results, Mahajan said. No serious adverse events emerged, and cases of mild ocular inflammation were treated successfully with topical corticosteroids, he said. After receiving the intravitreal injection, patients received three weeks of oral steroids to control inflammation.
Macular Degeneration: Cell Replacement vs Rescue
Cellular regeneration strategies for macular degeneration: past, present and future
- Valeria Chichagova,
- Dean Hallam,
- Joseph Collin,
- Darin Zerti,
- Birthe Dorgau,
- Majed Felemban,
- Majlinda Lako &
- David H. Steel
- Eyevolume 32, pages946–971 (2018)
- doi:10.1038/s41433-018-0061-z
- Download Citation
Received:29 November 2017Revised:05 January 2018Accepted:15 January 2018Published:05 March 2018
Abstract
Despite considerable effort and significant therapeutic advances, age-related macular degeneration (AMD) remains the commonest cause of blindness in the developed world. Progressive late-stage AMD with outer retinal degeneration currently has no proven treatment. There has been significant interest in the possibility that cellular treatments may slow or reverse visual loss in AMD. A number of modes of action have been suggested, including cell replacement and rescue, as well as immune modulation to delay the neurodegenerative process. Their appeal in this enigmatic disease relate to their generic, non-pathway-specific effects. The outer retina in particular has been at the forefront of developments in cellular regenerative therapies being surgically accessible, easily observable, as well as having a relatively simple architecture. Both the retinal pigment epithelium (RPE) and photoreceptors have been considered for replacement therapies as both sheets and cell suspensions. Studies using autologous RPE, and to a lesser extent, foetal retina, have shown proof of principle. A wide variety of cell sources have been proposed with pluripotent stem cell-derived cells currently holding the centre stage. Recent early-phase trials using these cells for RPE replacement have met safety endpoints and hinted at possible efficacy. Animal studies have confirmed the promise that photoreceptor replacement, even in a completely degenerated outer retina may restore some vision. Many challenges, however, remain, not least of which include avoiding immune rejection, ensuring long-term cellular survival and maximising effect. This review provides an overview of progress made, ongoing studies and challenges ahead.
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