Adeno-associated virus (AAV) vectors are considered the current gold standard tool for retinal gene transfer. AAV-based vectors have been extensively evaluated in preclinical and clinical studies and have proven to be safe and efficient for long-term expression of transgenes in the retina of animal models as well as in humans.

The most advanced gene therapy approach is a recombinant adeno-associated virus (rAAV) vector for gene supplementation treatment of RPE65-linked Leber congenital amaurosis (LCA2), which received marketing authorization in late 2017.

Most inherited retinal dystrophies (IRD) are due to mutations in genes that are specifically expressed in the photoreceptors or the retinal pigment epithelium (RPE). In order to efficiently targeting these cells the outer retina subretinal delivery of the vectors is needed, which involves surgical detachment of the neuroretina from the RPE. However, subretinal injections have an increased risk for collateral damage of the already compromised retina of IRD patients. In addition, subretinal injections result only in a localized transduction of cells within the area of the retinal detachment. The cells outside the bleb are not exposed to therapeutic levels of rAAV-vectors, resulting in untreated parts of the retina. Unfortunately the current rAAV-vectors are not likely to diffuse well into deeper layers of retinal tissues.

Therefore, there is an unmet need for the development of novel AAV vectors, which allow an improved transduction of retinal cells enabling pan-retinal gene expression through less invasive application routes such as intravitreal (IVT) injection. Novel AAV vectors with the ability to penetrate the retina from the vitreous would allow a much safer treatment of a larger retinal area with only a single IVT injection.

The main objective of our project is to further develop promising novel engineered AAV vectors for clinical application. The work program includes the in vitro and in vivo characterization of the novel AAVs. In vivo experiments in wild-type mice and retinal degeneration mouse models with vectors expressing eGFP controlled by cell type-specific promoters will establish the transduction efficiency of the novel AAVs in murine rods and cones. Subsequently, analogous experiments in larger models are performed to confirm the ability of the vectors to transduce rods and cones after IVT application across species. After completion of these experiments the optimal vector variant(s) in IVT gene supplementation approaches are currently tested in established mouse models of achromatopsia and retinitis pigmentosa.