A groundbreaking stem cell therapy for severe cornea damage has successfully concluded its extended clinical trial, with promising results published in Nature Communications on March 4, 2025. The innovative procedure, known as cultivated autologous limbal epithelial cells (CALEC), was developed by the team at Mass Eye and Ear, a part of the Mass General Brigham healthcare system.
The CALEC treatment involves a unique process where stem cells are removed from a healthy eye and expanded into a cellular tissue graft. This cultivation process takes approximately two to three weeks, after which the graft is surgically transplanted into the eye suffering from cornea damage.
Dr. Ula Jurkunas, the lead investigator of the trial, expressed satisfaction with the results, stating that the treatment was not only safe but also over 90% effective in restoring the cornea’s surface. This is particularly significant for individuals with cornea damage previously deemed untreatable.
The trial demonstrated that the CALEC treatment successfully restored the cornea in half of the patients within three months. This success rate increased to 79% and 77% at the 12- and 18-month reviews respectively. The overall success rate of CALEC stood at 93% and 92% at the 12 and 18-month mark, including partial successes.
While CALEC remains experimental and is not yet available at Mass Eye and Ear or any other U.S. hospital, the results of this trial indicate that additional studies are warranted before the treatment can be submitted for federal approval.
The cornea, being the eye’s clear outer layer, depends on healthy stem cells in its outer border, the limbus, for maintaining a smooth surface. Any cornea injury can deplete these limbal epithelial cells, which do not regenerate. The consequent limbal stem cell deficiency causes persistent damage to the eye’s surface, leading to constant pain and visual difficulties.
The need for an effective treatment for this condition led to the development of the CALEC procedure, the first stem cell therapy in the eye in the U.S. funded by the National Eye Institute (NEI), a division of the National Institutes of Health (NIH).
Despite the promising results, the CALEC therapy has limitations. It is currently only applicable to patients with a single affected eye, as the procedure requires healthy cells from the unaffected eye. Future plans include the development of an allogeneic manufacturing process using limbal stem cells from a cadaveric donor eye, which would allow treatment for patients with both eyes affected.
The successful completion of this trial demonstrates the potential of cell therapy in treating incurable conditions. It paves the way for larger studies with longer follow-ups and a randomized-control design, and hopefully, FDA approval. The ultimate objective, as expressed by Dr. Jurkunas, is to make this effective treatment accessible to patients across the country.
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