Development of a translatable gene augmentation therapy for CNGB1-retinitis pigmentosa

In this study, we investigate a gene augmentation therapy candidate for the treatment of retinitis pigmentosa (RP) due to cyclic nucleotide-gated channel beta 1 (CNGB1) mutations. We use an adeno-associated virus serotype 5 with transgene un-der control of a novel short human rhodopsin promoter. The promoter/capsid combination drives efficient expression of a reporter gene (AAV5-RHO-eGFP) exclusively in rod photore-ceptors in primate, dog, and mouse following subretinal deliv-ery. The therapeutic vector (AAV5-RHO-CNGB1) delivered to the subretinal space of CNGB1 mutant dogs restores rod-medi-ated retinal function (electroretinographic responses and vision) for at least 12 months post treatment. Immunohisto-chemistry shows human CNGB1 is expressed in rod photore-ceptors in the treated regions as well as restoration of expres-sion and trafficking of the endogenous alpha subunit of the rod CNG channel required for normal channel formation. The treatment reverses abnormal accumulation of the second messenger, cyclic guanosine monophosphate, which occurs in rod photoreceptors of CNGB1 mutant dogs, confirming forma-tion of a functional CNG channel. In vivo imaging shows long-term preservation of retinal structure. In conclusion, this study establishes the long-term efficacy of subretinal delivery of AAV5-RHO-CNGB1 to rescue the disease phenotype in a canine model of CNGB1-RP, confirming its suitability for future clinical development.