Gene therapy holds promise for treatment of inherited retinal dystrophies, a group of rare genetic disorders characterized by severe loss of vision. Here, we report up to 3-year pre-specified interim safety and efficacy results of an open-label first-in-human dose-escalation phase 1/2 gene therapy clinical trial in 12 patients with retinal dystrophy caused by biallelic mutations in the retinaldehyde-binding protein 1 (RLBP1) gene of the visual cycle. The primary endpoints were systemic and ocular safety and recovery of dark adaptation. Secondary endpoints included microperimetry, visual field sensitivity, dominant eye test and patient-reported outcomes. Subretinal delivery of an adeno-associated viral vector (AAV8-RLBP1) was well tolerated with dose-dependent intraocular inflammation which responded to corticosteroid treatment, and focal atrophy of the retinal pigment epithelium as the dose limiting toxicity. Dark adaptation kinetics, the primary efficacy endpoint, improved significantly in all dose-cohorts. Treatment with AAV8-RLBP1 resulted in the resolution of disease-related retinal deposits, suggestive of successful restoration of the visual cycle. In conclusion, to date, AAV8-RLBP1 has shown preliminary safety and efficacy in patients with RLBP1-associated retinal dystrophy. Trial number: NCT03374657.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

With cell therapies advancing towards the patients’ bedside, there is an increased need for robust and up-scalable protocols to generate clinical grade stem cell-derived products.The protocol we present in the study provides a xeno-free, chemically defined, scalable and robust retinal pigment epithelial cell monolayer differentiation without the need for manual isolation that uses either human embryonic stem cells or human induced pluripotent stem cells as a starting material.

PurposeSubretinal suspension transplants of human embryonic stem cell-derived retinal pigment epithelial cells (hESC-RPE) have the capacity to form functional monolayers in naive eyes. We explore hESC-RPE integration when transplanted in suspension to a large-eyed model of geographic atrophy (GA).MethodsDerivation of hESC-RPE was performed in a xeno-free and defined manner. Subretinal bleb injection of PBS or sodium iodate (NaIO3) was used to induce a GA-like phenotype. Suspensions of hESC-RPE were transplanted to the subretinal space of naive or PBS-/NaIO3-treated rabbits using a transvitreal pars plana technique. Integration of hESC-RPE was monitored by multimodal real-time imaging and by immunohistochemistry.ResultsSubretinal blebs of PBS or NaIO3 caused different degrees of outer neuroretinal degeneration, RPE hyperautofluorescence, focal RPE loss, and choroidal atrophy; that is, hallmark characteristics of GA. In nonpretreated naive eyes, hESC-RPE integrated as subretinal monolayers with preserved overlying photoreceptors, yet not in areas with outer neuroretinal degeneration and native RPE loss. When transplanted to eyes with PBS-/NaIO3-induced degeneration, hESC-RPE failed to integrate.ConclusionsIn a large-eyed preclinical model, subretinal suspension transplants of hESC-RPE did not integrate in areas with GA-like degeneration.

PURPOSE. To analyze the morphologic effects of subretinal blebs in rabbits using real-time imaging by spectral-domain optical coherence tomography (SD-OCT), infrared-confocal scanning laser ophthalmoscopy (IR-cSLO), and blue-light fundus autofluorescence (BAF).METHODS. Subretinal blebs of PBS or balanced salt solution (BSS) were induced in albino or pigmented rabbits using a transvitreal pars plana technique. Spectral-domain optical coherence tomography, IR-cSLO, and BAF were done at multiple intervals for up to 12 weeks after subretinal bleb injection. The morphologic effects were compared with histologic analysis on hematoxylin-eosin-stained sections of the neurosensory retina and on flat-mounts of phalloidin-labeled RPE.RESULTS. Scans of SD-OCT of the normal rabbit posterior segment revealed 11 bands including six layers of the photoreceptors. Subretinal blebs of PBS or BSS caused acute swelling of the neurosensory retina followed by gradual atrophy. Outer retinal thickness was significantly reduced with pronounced degeneration of all the photoreceptor OCT layers. En face IR-cSLO showed a hyperreflective area corresponding to the progressive photoreceptor degeneration, whereas BAF revealed both hyper- and hypofluorescent changes in the RPE layer. The in vivo results were confirmed by histology and on subretinal flatmounts demonstrating extensive photoreceptor loss and disruption of the RPE mosaic.CONCLUSIONS. Subretinal blebs induce pronounced photoreceptor degeneration and RPE changes in the rabbit as demonstrated by in vivo imaging using SD-OCT, IR-cSLO, and BAF.