Preparation of prerequisite conditions for gene therapy of hereditary eye disorders

Genetic eye diseases are a group of rare diseases caused by mutations in more than 200 genes, which together affect a significant number of people (greater then 30/100,000). In 2017, the first drug that allows the introduction of an intact gene into the retina was registered (RPE65, Luxturna™), and clinical research is also ongoing for many other genes (ABCA4, MYO7A, RPGR). Involvement in the latter is currently the only option for most patients to access treatment that can prevent blindness. In Slovenia, we have a well-developed network for the diagnosis of genetic eye diseases, which was developed as part of the ARRS program by the research group of the eye clinic under the leadership of Prof. Marko Hawlina, under whose mentorship the proposed project leader, Dr. Ana Fakin, also received her doctorate, who continued her research work as part of a postdoctoral project at the UCL Institute of Ophthalmology. The main goal of the project was to establish a system that will enable Slovenian patients with hereditary eye diseases to have the best possible access to gene therapy. For this purpose, we have established a clinical-genetic database of patients, which contains anonymized genetic and clinical data of more than 1000 patients, necessary for entry into clinical studies. In new and undiagnosed patients, genetic analysis was performed using next-generation sequencing techniques. In patients in individual clinical subgroups, we accurately defined the degree of retinal and/or optic nerve involvement and analyzed the usefulness of various biomarkers. In the project of preparing patients for gene therapy, cooperation with researchers from the group of Prof. Damjan Glavač and the group of Prof. Borut Peterlin, with whom we carried out numerous research projects that enabled the diagnosis of patients with various genetic diseases and improved knowledge of these diseases. We also devoted ourselves to the development of new innovative methods for the quantitative assessment of visual function in patients with very poor vision. As part of the project, we established the Virtual Reality Laboratory, which is located in the National Center for Comprehensive Rehabilitation of the Blind and Visually Impaired at Eye Hospital Ljubljana and enables the advanced definition of complex visual perception with the help of biometrics. The results will have a significant impact on the planning of investigations, which are necessary to determine whether patients meet the inclusion criteria of clinical studies and to monitor the effect of treatment.

The established clinical-genetic database of patients with hereditary eye diseases enabled the implementation of numerous studies of genotype-phenotype correlations, which brought important new knowledge in the field of hereditary retinal diseases. By studying the concentration of vitamin A in the blood, we were the first to confirm the connection between a higher concentration of vitamin A and a milder clinical picture of patients with a specific pathogenic variant in the RHO gene, which will contribute to the development of supportive therapy in patients with variants in this gene. By participating in multicenter studies, we defined the phenotype associated with the ADGRV1 gene and, by reviewing previously published data, proposed a new categorization of disease stages associated with pathogenic variants in CNGA3 and CNGB3. By detailed analysis of the electroretinographic characteristics of patients with ABCA4-retinopathy, we determined new genotype-specific electrophysiological biomarkers. The virtual reality laboratory, which was established within the framework of this project, brings the possibility of many studies of complex visual function, which will bring new insight into the process of vision perception in healthy people and patients with various visual perception impairments. The first pilot studies include patients with one of the most common eye diseases, age-related macular degeneration, and patients with the most common hereditary eye disease, retinitis pigmentosa. By defining the visual function of these patients more precisely, we will gain a unique insight into their perception of the world and thereby improve the understanding of the problems they face in everyday life. We will also gain insight into their adaptation mechanisms that help them live with a visual impairment.

The established clinical-genetic database of patients with hereditary eye diseases enables the rapid identification of patients who could be candidates for clinical studies of gene therapy or other therapies for hereditary eye diseases, thereby improving Slovenian patients' access to treatment. With extended genetic diagnostics, we found that many pathogenic variants in the Slovenian population are new or more common than elsewhere, which improved the overview of genetic diversity in our geographical region. We have genetically confirmed the first Slovenian family with dominant gelsolin amyloidosis and the first family with dominant inflammatory retinopathy linked to the CAPN5 gene, which confirmed the existence of these extremely rare diseases in Slovenia and thus improved the possibility of their recognition and appropriate treatment. The virtual reality laboratory brings the possibility of using advanced technology for research into complex visual perception and is unique on a global level, which will contribute to the development of UKC Ljubljana as a leading research institution.