The Food and Drug Administration approved clinical trial will ultimately treat six patients with CHM to help determine the safety and efficacy of this novel treatment. A promising treatment for CHM had been elusive until the advent of gene therapy. The transfer of new genes into the dysfunctional cells has the potential to restore the health and function of these cells.
The team was led by Byron L. Lam, M.D., the Robert Z. and Nancy J. Greene Chair in Ophthalmology, who has a broad background in neuro-ophthalmology and hereditary retinal degenerations. Lam is Bascom Palmer’s Medical Director of Neuro-Ophthalmology and Scientific Co-Director of the Adrienne Arsht Hope for Vision Retinal Degeneration Laboratory.
CHM is a progressive degenerative disorder of the retina and the choroid layers that line the inside of the back portion of the eye. It is caused by a genetic defect of the X-chromosome that results in a faulty protein in the retina. Symptoms of CHM begin with a gradual loss of night and peripheral vision. Over time, CHM leads to complete loss of central sight. CHM affects one in 50,000 people, and the vast majority of affected people are young men.
The clinical trial’s approach involved using a large number of harmless viruses (known as AAV2-REP1) modified to carry copies of the normal gene into the eye to correct the genetic defect in CHM. The gene therapy was delivered to the space under the retina through an injection technique approved by the FDA for research purposes for this clinical trial. The injection provides controlled delivery of the gene therapy. The modified viruses infect retinal cells and carry copies of the normal gene into the cells, where the normal gene continues to work to maintain the function and integrity of the cells. The goal of the treatment is to maintain or even improve visual function in CHM patients.
“We are extremely excited and optimistic about the success of this gene therapy trial,” said Lam. “We are continuing to treat more patients with CHM, and we hope the knowledge gained will help patients with other retinal diseases.”
Retinal surgeons Janet L. Davis, M.D., and Ninel Gregori, M.D., performed the highly specialized surgery, which involved injecting a full dose of the vector under a very thin retina. The technique is challenging and was done successfully without damaging the retina.
The first clinical trial using the AAV2-REP1 approach to treat CHM was conducted at the University of Oxford under the direction of Dr. Robert MacLaren, a professor of ophthalmology. MacLaren and the Bascom Palmer team have collaborated on this project for the past year.
The AAV2-REP1 gene therapy viral vector was provided by NightstaRx, a private biopharmaceutical company focused on the development of gene therapy for CHM.
“Gene therapy has huge potential as a treatment for many patients who are suffering from genetic causes of blindness,” said David Fellows, CEO of NightstaRx. “We have seen some very promising results from our CHM program and have recently expanded our pipeline to include other inherited retinal dystrophy disorders as we continue to strive to restore or maintain sight in patients suffering from these devastating blinding diseases.”
University of Miami