The cornea acts as a window that lets light into the interior of the eye.

Corneal epithelial cells cover the cornea and regenerate daily. The new corneal epithelial cells are made from corneal epithelial stem cells, which exist on the boundary between the black and white layers of the eye.

Limbal stem cell deficiency occurs when damaged corneal epithelial stem cells cannot degenerate. This disease causes the cornea to become clouded, resulting in significantly impaired visual acuity.

By transplanting iPS cell-derived corneal epithelial cell sheets, which are under development by RAYMEI, on the surface of the cornea, corneal epithelial stem cells will regenerate, recovering the visual acuity of the patient.

These iPS cell-derived corneal epithelial cell sheets have been transplanted into four patients as part of clinical research launched in 2019 by Professor Kohji Nishida of the Graduate School of Medicine, Osaka University. As announced in April 2022, post-transplantation results one year later confirmed none of the four patients have developed severe complications. As for efficacy, the visual acuity of three of the four patients has improved significantly.

RAYMAY aims to launch a clinical trial in 2023 and receive government approval for the general use of this therapy by 2025.