| Summary: | <p>The aim of this thesis was to evaluate the efficacy and safety of retinal gene therapy in a pre-clinical model of CDHR1-associated retinal degeneration – a hitherto untreatable, blinding disorder.</p>
<p>Deep phenotyping of the Cdhr1-/- murine model demonstrated severe early deficits in cone and rod photoreceptor function followed by progressive photoreceptor cell death – recapitulating CDHR1 cone-rod dystrophy. Two AAV8 vectors expressing the full-length human CDHR1 coding sequence were designed, manufactured, validated and titrated in vivo.</p>
<p>Sub-retinal injection of AAV8.GRK1.CDHR1.pA (1.5 x 108 vg) in Cdhr1-/- mice at 3-4 weeks of age resulted in functional rescue of cone and rod photoreceptors with improved response amplitudes and decreased implicit times to 12-months post-injection; a slowing of photoreceptor cell death with regeneration of full-length photoreceptor outer segments confirmed on ultrastructural analysis to 21-months post-injection; and a behavioural rescue effect on photopic and scotopic optomotor testing, sustained to 21-months post-injection. AAV8.GRK1.CDHR1.pA at 1.5 x 108 vg appeared safe in C57BL/6J mice by the same outcome measures to 22-months post-injection.</p>
<p>Genetic prevalence estimates presented herein suggest more than 200,000 affected individuals worldwide. We characterised 146 individuals with biallelic variants in CDHR1, describing the retinal phenotype, natural history, genotype-phenotype associations, with 25 novel pathological sequence variants.</p>
<p>This is the first therapy shown to improve retinal structure and function in a pre-clinical model of CDHR1-associated retinal degeneration. A patent to protect the vectors described herein has been filed on behalf of the University of Oxford, with commercial agreements obtained in preparation for an onward phase 1 clinical trial.</p>
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