Palo Alto, CA — Researchers took a major step forward in their mission to treat blindness from Retinal Degeneration (RD), an important cause of blindness worldwide. Four blind patients received a single injection of a light-sensing protein and showed improvement in vision, shape discrimination, and mobility.
A recent Molecular Therapy publication, “A synthetic opsin restores vision in patients with severe RD,” demonstrated how a lab-engineered opsin protein overcame the loss of naturally occurring opsins to become a powerful therapeutic for RD.
Opsins are light sensing proteins found within photoreceptor cells in the retina. Humans have three opsins to detect different colors of light and one opsin to detect dim light. When the retina degenerates, the opsins are lost and patients no longer see light.
Led by Samar Mohanty Ph.D., Chief Scientific Officer at Nanoscope, researchers engineered a single, synthetic opsin protein that did the job of four human opsins, detecting different colors of light and dim light. The opsin was packaged into a gene therapy vector and patients received a single injection in an out-patient clinic.
Remarkably, some of the remaining cells in the retina expressed the new opsin protein and became light-sensitive. Patients that were legally blind showed improvement in functional vision.
RD is extremely hard to treat with traditional gene therapy because there are so many genes involved in the disease. On top of that, photoreceptors and retina pigment epithelium cells needed for gene therapy deteriorate in late stages of the disease. The synthetic opsin overcomes these challenges and promises to be a successful therapeutic path for RD patients.
Co-author Vinit Mahajan M.D., Ph.D., Stanford professor and vice chair of ophthalmology research, said, “The four patients had very advanced vision loss and they would normally have been excluded from gene therapy trials. I am thrilled that patients with severe retinal degeneration may have a therapeutic option in the near future.”
A phase-3 trial in a number of patients with RD was recently completed and undergoing review by the FDA.
Mahajan explained, “Optogenetics, the use of light to modulate neuronal activity, was developed in the 1970s, but its use in ophthalmology to try to restore vision by photo-sensitizing remaining retinal cells in patients with RD is fairly new.”