Stem cell therapy for corneal injuries shows remarkable results in clinical studies

Stem cell therapy for corneal injuries shows remarkable results in clinical studies

An expanded clinical trial testing a groundbreaking, experimental stem cell treatment for blinding corneal lesions found that the treatment was feasible and safe, and there was a high rate of complete or partial success, in 14 patients treated and followed for 18 months. The results of this new Phase 1/2 study were published on March 4, 2025Nature communication.

The treatment, called cultured autologous limbal epithelial cells (CALEC), was developed at Mass Eye and Ohr, a member of the General Brigham Healthcare System. The innovative procedure involves removing stem cells from a healthy eye with a biopsy, expanding them into a cellular tissue graft using a novel manufacturing process that takes two to three weeks, and then surgically placing the graft into the eye with a damaged cornea.

Our initial study in four patients showed that CALEC was safe and the treatment was possible. Now we have this new data supporting that Calec is more than 90% effective at restoring the surface of the cornea, making a meaningful difference in people with corneal damage that was considered untreatable. “

Ula Jurkunas, MD,principal investigator, investigator,Associate Director of the Cornea Service at Mass Eye and Ear and Professor of Ophthalmology at Harvard Medical School

Researcher showed that CALEC completely restored the cornea in 50% of participants at their 3-month visit and that the rate of complete success increased to 79% and 77% at their 12- and 18-month visits, respectively.

With two participants meeting the definition of partial success at 12 and 18 months, the overall success of CALEC at 12 and 18 months was 92% and 92%. Three participants received a second CALEC transplant, one of whom achieved complete success during the end-of-study visit. Additional analysis of CALEC's effect on vision showed variable improvements in visual acuity in all 14 CALEC patients.

CALEC demonstrated a high safety profile, with no serious events occurring in donor or recipient eyes. One adverse event, a bacterial infection, occurred in one participant eight months after transplantation due to chronic contact lens use. Other adverse events were minor and resolved quickly following procedures.

CALEC remains an experimental procedure and is not currently offered at Mass Eye and Ear or any U.S. hospital, and additional studies will be needed before the treatment is submitted for federal approval.

The CALEC trial is the first human study of a stem cell therapy to be funded by the National Eye Institute (NEI), a part of the National Institutes of Health (NIH) and was the first stem cell therapy in the eye in the US Other research collaborators include Jia Yin, MD, PhD and Reza Dana, MD at Mass Eye and Ear, Jerome Ritz, MD, of Dana-Farber Cancer Institute's Connell and O'Reilly Family Cell Manipulation Core Facility, where the production of the stem cell transplant takes place; and Myriam Armant, PhD, of Boston Children’s Hospital; and the Jaeb Center for Health Research.

The cornea is the clear, outermost layer of the eye. It is the outer border, the limbus, a large volume of healthy stem cells called limbal epithelial cells that maintain the smooth surface of the eye. If a person suffers a corneal injury, such as: B. a chemical burn, infection or other trauma, it can deplete the limbal epithelial cells, which can never regenerate. The resulting limbal stem cell deficiency leaves the eye with a permanently damaged surface on which it cannot undergo corneal transplantation, the current standard for vision care. People with these injuries often experience persistent pain and visual difficulties.

This need led Jurkunas, as a junior scientist, and Dana, director of the corneal service at Mass Eye and Ear, to investigate a new approach to regenerating limbal epithelial cells. Nearly two decades later, after preclinical studies and collaborations with researchers at Dana-Farber and Boston Children's, it was possible to consistently produce Calc grafts that met stringent quality criteria required for human transplantation. The clinical trial was approved by the U.S. Food and Drug Administration (FDA) and the Mass General Brigham Institutional Review Board (IRB) and the first patient was treated at Mass Eye and Ohr in 2018. The successful completion of the trial was achieved through close coordination between Jurkunas' surgical team and the cell manufacturing facility at Dana-Farber.

Studies like these show the promise of cell therapy to treat incurable diseases. Mass General Brigham's Gene and Cell Therapy Institute helps translate researchers' scientific discoveries into clinical trials first and ultimately life-changing treatments for patients.

As an autologous therapy, a limitation of this approach is that the patient only has one involved eye, so a biopsy can be performed to obtain starting material from the unaffected normal eye.

“Our future hope is to establish an allogeneic manufacturing process starting with limbal stem cells from a normal cadaver donor eye,” said Dr. Ritz “This will hopefully expand the use of this approach and allow it to treat patients with damage to both eyes.”

Meanwhile, future CALEC trials should include larger numbers of patients in multiple centers with longer follow-ups and a randomized control design.

“We believe this research warrants additional trials that may help guide FDA approval,” Jurkunas said. “While we are proud to bring a new treatment from the bench into clinical trials, our guiding goal has been and will be to ensure that patients across the country have access to this effective treatment.”

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