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Cell therapy that repairs cornea damage with patient’s own stem cells achieves positive phase I trial results


Cultivated autologous limbal epithelial cells (CALEC) procedure shown to be safe and feasible with early positive results of restored cornea surfaces or vision gains in four patients with severe chemical burns.

(Image Credit: AdobeStock/Giovanni Cancemi)

(Image Credit: AdobeStock/Giovanni Cancemi)

A team led by researchers from Mass Eye and Ear highlighted the results of a phase I trial of a revolutionary stem cell treatment called cultivated autologous limbal epithelial cell transplantation (CALEC), which was found to be safe and well-tolerated over the short term in four patients with significant chemical burns in 1 eye.

According to the study1 published August 18 in Science Advances, the patients who were followed for 12 months experienced restored cornea surfaces — two were able to undergo a corneal transplant and two reported significant improvements in vision without additional treatment.

While the phase I study was designed to determine preliminary safety and feasibility before advancing to a second phase of the trial, the researchers consider the early findings promising.

Ula Jurkunas, MD, associate director of the Cornea Service at Mass Eye and Ear and an associate professor of ophthalmology at Harvard Medical School, noted in a news release from the Massachusetts Eye and Ear Infirmary news release that early results suggest that CALEC might offer hope to patients who had been left with untreatable vision loss and pain associated with major cornea injuries.

“Cornea specialists have been hindered by a lack of treatment options with a high safety profile to help our patients with chemical burns and injuries that render them unable to get an artificial cornea transplant,” she said in the news release. “We are hopeful with further study, CALEC can one day fill this crucially needed treatment gap.”

According to the study, in CALEC, stem cells from a patient’s healthy eye are removed via a small biopsy and then expanded and grown on a graft via an innovative manufacturing process at the Connell and O'Reilly Families Cell Manipulation Core Facility at Dana-Farber Cancer Institute. After 2 to 3 weeks, the CALEC graft is sent back to Mass Eye and Ear and transplanted into the eye with corneal damage.

Ula Jurkunas, MD, performs the first CALEC transplant in the United States as part of a clinical trial at Mass Eye and Ear in April 2018. (Image courtesy of Mass Eye and Ear)

Ula Jurkunas, MD, performs the first CALEC transplant in the United States as part of a clinical trial at Mass Eye and Ear in April 2018. (Image courtesy of Mass Eye and Ear)

Moreover, the news release noted the CALEC project is a collaboration between Jurkunas and colleagues in the Cornea Service at Mass Eye and Ear, researchers at Dana-Farber Cancer Institute, led by Jerome Ritz, MD, Boston Children’s Hospital, led by Myriam Armant, PhD, and the JAEB Center for Health Research. The clinical trial represents 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).

Expanding one’s own stem cells to address limitations in existing treatments

The researchers explained in the news release that patients who experience chemical burns and other eye injuries could develop limbal stem cell deficiency, an irreversible loss of cells on the tissue surrounding the cornea. As a result, these patients experience permanent vision loss, pain and discomfort in the affected eye. Without limbal cells and a healthy eye surface, these patients are unable to undergo artificial cornea transplants, the current standard of vision rehabilitation.

The study noted that current treatment strategies have limitations and associated risks the CALEC procedure aims to address through its unique approach of using a small amount of a patient’s own stem cells that can then be grown and expanded to create a sheet of cells that serves as a surface for normal tissue to grow back.1

According to the researchers, despite several studies describing an autologous stem cell approach over the past 25 years and similar methods being utilized in Europe, no U.S. research team had successfully developed a manufacturing process and quality control tests that met FDA requirements or showed any clinical benefit.

“It was challenging to develop a process for creating limbal stem cell grafts that would meet the FDA’s strict regulatory requirements for tissue engineering,” Ritz, executive director of the Connell and O’Reilly Families Cell Manipulation Core Facility at Dana-Farber and professor of medicine at Harvard Medical School, said in the news release. “Having developed and implemented this process, it was very gratifying to see encouraging clinical outcomes in the first cohort of patients enrolled on this clinical trial.”

The researchers also noted that studies like this show the promise of cell therapy for treating incurable conditions. Mass General Brigham’s Gene and Cell Therapy Institute is helping to translate scientific discoveries made by researchers into first-in-human clinical trials and, ultimately, life-changing treatments for patients. The institute’s multidisciplinary approach sets it apart from others in the space, helping researchers to rapidly advance new therapies and pushing the technological and clinical boundaries of this new frontier, according to the release.

Case studies hold early promise as clinical trial advances

As a part of the phase I study, 5 patients with chemical burns to 1 eye were enrolled and biopsied. Four received CALEC; a series of quality control tests determined the cells in the 5th patient were unable to adequately expand. The CALEC patients were tracked for 1 year.

The first patient treated, a 46-year-old male, experienced a resolution of his eye surface defect, which primed him to undergo an artificial cornea transplant for vision rehabilitation. The second, a 31-year-old male, experienced a complete resolution of symptoms with vision improving from 20/40 to 20/30. The third, a 36-year-old male, had his corneal defect resolved and his vision improved from hand motion – only being able to see broad movements like waving – to 20/30 vision. The fourth, a 52-year-old male, initially did not have a successful biopsy that resulted in a viable stem cell graft. After re-attempting CALEC three years later, he underwent a successful transplant and his vision improved from hand motion to being able to count fingers. He then received an artificial cornea.

According to the news release, the researchers are finalizing the next phase of the clinical trial in 15 CALEC patients they are tracking for 18 months to better determine the procedure’s overall efficacy. Their hope is that CALEC can one day become a treatment option for patients who previously had to endure long-term deficits when existing treatment options were not an option given the severity of their injuries.

This study was funded by NEI/NIH grants. Pre-trial work at Boston Children’s Hospital was also funded by PACT, an initiative of the of the NIH’s National Heart, Lung, and Blood Institute.1

In addition to Jurkunas, Ritz, and Armant, additional investigators include Jia Yin, MD, PhD,MPHReza Dana, MD, Lynette Johns, OD, Sanming Li, PhD, Ahmad Kheirkhah, MD, Kishore Katikireddy, PhD, Alex Gauthier, PhD, Stephan Ong Tone, MD, PhD and Stacey Ellender, PhD of Mass Eye and Ear, Hélène Negre, PharmD, PhD, Kit L. Shaw, PhD, Diego E. Hernandez Rodriguez, PhD, Heather Daley, BS, of Dana-Farber Cancer Institute, and Allison Ayala, MS, Maureen Maguire, PhD and Lassana Samarakoon, MPH, of Jaeb Center for Health Research.

The news release also noted the CALEC procedure is patent pending. Jurkunas and Dana also disclose equity in Ocucell, a company interested in developing cell-based therapies for the eye, according to the release.

  1. Ula Jurkunas et al. Cultivated autologous limbal epithelial cell (CALEC) transplantation: Development of manufacturing process and clinical evaluation of feasibility and safety.Sci. Adv.9,eadg6470(2023).DOI:10.1126/sciadv.adg6470
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