Objective: To determine the efficacy of intravitreal administration of 9-cis-retinal in restoring visual function in Rpe65-mutant dogs.
Methods: Intravitreal injection of 9-cis-retinal was administered in 1 eye of 7 Rpe65-/- dogs at a range of ages. Electroretinogram analysis and testing of visual performance was used to evaluate outcomes after a single injection and in 2 dogs after a second injection in the same eye.
Results: In 5 of 7 injected dogs, 9-cis-retinal injection resulted in increased rod electroretinogram responses and improved functional vision. Three injected dogs exhibited increased 33-Hz flicker amplitudes characteristic of cone-mediated responses. Electroretinogram improvement was no longer evident by week 10 postinjection in 1 dog monitored over time. A second injection of 9-cis-retinal was performed in the same eye of 2 of the 7 dogs and also resulted in rescue of visual function.
Conclusion: Our findings establish that 9-cis-retinoid therapy can restore visual function in a canine model of human disease resulting from RPE65 mutations.
Clinical relevance: These positive proof-of-principle results provide support for the development of intravitreal devices for sustained delivery of 9-cis-retinal as a therapy for conditions resulting from failure of the visual cycle.