Lifechanging stem cell treatment repairs irreversible corneal damage
A new stem cell therapy restores corneal clarity in 92% of patients, offering hope for those with severe eye injuries.
A recent trial showed a 92% success rate, bringing hope for future FDA approval and wider treatment availability. (CREDIT: CC BY-SA 4.0)
Your cornea, the eye’s outermost layer, is vital for clear vision. It relies on a steady supply of limbal epithelial stem cells to maintain its smooth surface. However, injuries such as chemical burns, infections, or trauma can deplete these cells, leading to limbal stem cell deficiency (LSCD).
This condition causes persistent pain, inflammation, scarring, and vision loss. Traditional corneal transplants, the standard treatment for vision rehabilitation, do not work in LSCD patients because the damaged eye lacks the necessary stem cells to support the new tissue.
Currently, treatment options for LSCD include grafting tissue from a healthy eye, which works well for patients with only one damaged eye.
The most effective approach involves transplanting cultivated limbal epithelial stem cells to restore the corneal surface. However, this process has limitations, including the need for complex cell expansion techniques and regulatory challenges in the United States.
The Promise of CALEC Therapy
A pioneering therapy called cultivated autologous limbal epithelial cell (CALEC) transplantation may provide a solution.
Developed by researchers at Mass Eye and Ear, this technique involves taking a small biopsy from a healthy eye, expanding the stem cells into a graft over two to three weeks, and then surgically implanting them into the damaged eye. Unlike earlier methods, CALEC uses only FDA-compliant materials without relying on animal or donor-derived feeder cells.
“Our first trial in four patients showed that CALEC was safe and the treatment was possible,” said Dr. Ula Jurkunas, associate director of the Cornea Service at Mass Eye and Ear and professor of Ophthalmology at Harvard Medical School. “Now we have this new data supporting that CALEC is more than 90% effective at restoring the cornea’s surface, which makes a meaningful difference in individuals with cornea damage that was considered untreatable.”
The recent phase I/II clinical trial, published in Nature Communications, tested CALEC on 14 patients over an 18-month period. Results showed that the cornea was fully restored in 50% of patients after three months, with the success rate increasing to 79% at 12 months and 77% at 18 months.
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Two participants showed partial improvement, bringing the overall success rate to 93% and 92% at those time points, respectively. Three patients required a second CALEC transplant, with one achieving complete success by the end of the study.
Safety and Future Prospects
Safety was a key focus of the study, and the findings were encouraging. No serious complications were reported in either the donor or recipient eyes. The most significant adverse event was a bacterial infection in one patient, which occurred months after the transplant due to prolonged contact lens use. Other minor side effects resolved quickly with standard care.
CALEC remains an experimental procedure and is not yet available in U.S. hospitals. The next step involves conducting larger trials at multiple medical centers to further validate its safety and effectiveness.
Researchers also aim to develop an allogeneic version of CALEC, which would use stem cells from cadaveric donor eyes. This approach could extend treatment to patients with damage in both eyes, overcoming a major limitation of the current method.
“Our future hope is to set up an allogeneic manufacturing process starting with limbal stem cells from a normal cadaveric donor eye,” said Dr. Jerome Ritz of Dana-Farber Cancer Institute. “This will hopefully expand the use of this approach and make it possible to treat patients who have damage to both eyes.”
Advancing Toward FDA Approval
The CALEC trial represents a significant milestone in regenerative medicine and is the first human study of stem cell therapy for the eye to receive funding from the National Eye Institute.
Mass Eye and Ear researchers collaborated with scientists from Dana-Farber Cancer Institute, Boston Children’s Hospital, and the JAEB Center for Health Research to develop the standardized manufacturing process.
The study received approval from the U.S. Food and Drug Administration (FDA) and the Mass General Brigham Institutional Review Board before beginning in 2018.
Mass General Brigham’s Gene and Cell Therapy Institute continues to support the transition of laboratory discoveries into clinical trials and, ultimately, real-world treatments. Researchers are optimistic that further studies will lead to FDA approval, making this life-changing therapy widely accessible.
“We feel this research warrants additional trials that can help lead towards FDA approval,” said Dr. Jurkunas. “While we are proud to have been able to bring a new treatment from the lab bench to clinical trials, our guiding objective was and always will be for patients around the country to have access to this effective treatment.”
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