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A gene therapy developed by an interdisciplinary research team to treat a form of color blindness has proven to be safe and effective in principle.
The healthy version of the CNGA3 gene is inserted directly into the patient’s retina.
A gene therapy developed by scientists and doctors from Tübingen and Munich to treat a form of color blindness has been shown to be safe and effective in principle in a phase I / II clinical study at the Tübingen University Hospital. The first gene therapy for an inherited eye disease in Germany will be further developed until it is ready for use.
In about a third of achromatopsia patients, the defect is in the CNGA3 gene. A team from the Ophthalmology Research Institute of the Tübingen University Hospital and the Department of Pharmacy and Ophthalmology from the Ludwig Maximilians University in Munich developed a gene therapy treatment for this genetic defect. In gene therapy, the healthy version of the CNGA3 gene is introduced directly into the patient’s retina through a harmless virus. After a few weeks, the cells of the retina can use the healthy version of the CNGA3 gene and form the corresponding intact protein, which is supposed to restore the function of the defective cones. The genetic shuttles used, adeno-associated viruses, were developed at the Ludwig Maximilians University in Munich by Professor Stylianos Michalakis and Professor Martin Biel.
Even better treatment success expected in the future
The first clinical study on this therapy in humans has been completed at the Tübingen University Clinic. It is published in the specialized magazine. JAMA Ophthalmology of the American Medical Association published. In the study, the worst eye of nine patients with achromatopsia from 24 to 59 years old was treated surgically at the university eye clinic in Tübingen by injecting the genetic therapeutic agent under the retina. “Subsequently, the subjects had no drug-related health problems and their retinas showed no permanent changes,” reports Professor Dominik Fischer, head of the clinical trial. The main concern of this first clinical study was to ensure that the treatment could be classified as safe. In terms of effectiveness, too, there is a clearly positive effect. The visual function of the patients has improved somewhat, both in terms of visual acuity and in contrast and color vision.
“The study that has now been conducted is an important first step and a milestone towards curative therapy for achromatopsia, and we look forward to even better treatment successes in the future,” says Professor Bernd Wissinger of the Ophthalmology Research Institute of Tübingen, who, together with Professor Martin Biel from the Pharmacy Department of the Ludwig-Maximilians-Universität München, leads the general RD-CURE project for the development of gene therapy for inherited diseases of the retina.
Carry out gene therapy to obtain the best possible effect in childhood.
For safety reasons, all nine treated patients were in adulthood and therefore had a retina that was already more or less severely damaged. “Furthermore, the parts of the brain that process vision become less and less plastic in adulthood,” emphasizes Professor Marius Ueffing, director of the Ophthalmology Research Institute. “Since the brain of those affected by achromatopsia has never learned to process color vision, this plasticity is a necessary prerequisite for turning newly acquired color vision from the retina into a true visual impression.” Since the study has shown that the therapy is safe, it may be advisable in the future to treat those affected so early that high brain plasticity and a retina that has not yet been damaged may increase the success of the treatment.
According to the scientists, the new gene therapy should be carried out analogously to the recently approved gene therapy drug Luxturna in childhood to have the best possible effect. “Since the genetic vectors used have proven to be safe, a follow-up study in pediatric CNGA3 patients is possible and useful,” explains Professor Stylianos Michalakis from the Department of Ophthalmology at the Ludwig Maximilians University in Munich.
Source:
Fischer, M.D., Michalakis, S., et al .: Safety and vision outcomes of cone photoreceptors targeting subretinal gene therapy in achromatopsia: a non-randomized controlled trial. JAMA Ophthalmology, https://dx.doi.org/10.1001/jamaophthalmol.2020.1032
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