Surgeons at Harvard Medical School have found that a technique used to replace the surface of an eye damaged by chemical burns is safe and feasible, having successfully been performed on four patients so far.
The technique, called cultivated autologous limbal epithelial cell transplantation (CALEC), could in the future be applied to other types of corneal damage, including neurotrophic keratitis.
The procedure is being studied in an ongoing Phase 1/2 clinical trial (NCT02592330) that will now recruit more patients and continue through 2021, based on the initial findings. More information on contacts and locations can be found here.
CALEC uses stem cells harvested from the healthy eye of patients themselves, sidestepping the risk of transplant rejection that is associated with conventional corneal transplants, which use cells derived from another person.
“Using the patient’s own stem cells is a big step for regenerative medicine,” Ula Jurkunas, MD, the principal investigator of the study, said in a Harvard Medical School press release. “With this clinical trial, we hope to pave the way for better care for patients with corneal blindness, who have long needed better solutions for their condition.”
CALEC was developed by researchers at Harvard Medical School, Massachusetts Eye and Ear, Boston Children’s Hospital, and Dana-Farber Cancer Institute.
The technique is intended to treat patients who have damage to their cornea — or the outer surface of the eye — and uses limbal stem cells harvested from the patient’s healthy eye. This type of cells maintain the barrier between the cornea and the conjunctiva, or the white areas on the sides of the eye.
In patients with chemical burns, limbal stem cells from the affected eye are often damaged and unable to produce new cells. This deficiency can also be caused by infection, contact lens complications, and other conditions, including neurotrophic keratitis.
CALEC begins with collecting a small sample of limbal stem cells from a patient’s healthy eye. Those cells are grown on a membrane for a two- to three-week period to generate corneal cells in lab conditions.
Once the cells cover the membrane surface, surgeons remove the scar tissue present in the damaged eye and transplant the membrane of corneal cells onto the patient.
“The manufacturing process is carried out in a ‘clean room’ environment under strict quality-controlled conditions to maintain product sterility,” said Jerome Ritz, MD, a professor of medicine at Dana-Farber. “The entire process takes approximately three weeks before the limbal stem cell graft is ready to be sent to the operating room at Mass Eye and Ear where Dr. Jurkunas performs the transplant.”
The procedure was first performed successfully in April 2018 as part of the ongoing clinical trial and has been since performed in three additional patients, making them the first such procedures in the United States.
The primary goals of the study are safety, indicated by the presence of infection, corneal perforation, graft detachment, and any other adverse events, and feasibility, indicated by obtaining sufficient cell growth and avoiding contamination of the graft.
Researchers did find that not enough cells were produced in the manufacturing phase for one of the five enrolled patients, and another patient required a second stem cell sample after insufficient growth of the first attempt.
Additionally, the study will evaluate efficacy as a secondary goal, indicated by improvement in the integrity of the corneal surface, a decrease in new blood vessel formation (corneal neovascularization), and other symptoms.
The four patients with successful CALEC transplants have reported no pain following the procedure. These patients will be monitored long term to track their progress.
“These early cases show great promise for a safe treatment option for people who have lost vision from chemical burns and corneal infections,” said Joan Miller, MD, a professor of ophthalmology at Harvard Medical School and chair of ophthalmology at Massachusetts Eye and Ear.
The general goal of CALEC is to restore the corneal surface to allow for more conventional corneal transplants that require support from limbal stem cells. Researchers also hope that the CALEC transplant itself may help restore vision.
“Our team has put a tremendous amount of effort into developing the procedures for growing the grafts,” Jurkunas said. “So many conditions have to be just right so that the cells grow and the patient is safe. If we continue to be successful we will be able to give these patients with this condition a healthy surface of the eye—and possibly even restore vision to some.”
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