Treatment of a novel CLN2 patient-derived in vitro ocular model with RGX-381 gene therapy prevents or reverses lysosomal waste accumulation

Abstract

Purpose : Late infantile neuronal ceroid lipofuscinosis type 2 (CLN2) is an autosomal recessive disorder caused by mutations in the CLN2 gene encoding lysosomal tripeptidyl peptidase 1 (TPP1), resulting in accumulation of lysosomal storage material and progressive neurological and retinal degeneration. While enzyme replacement therapy (ERT) slows loss of ambulation and prolongs life expectancy in children with CLN2 disease, it does not address retinal degeneration that rapidly progresses to blindness. This study explores the ability of gene therapy with RGX-381 (AAV9.hCLN2) to prevent or reverse retinal degeneration in a CLN2 patient-derived in vitro ocular model.

Methods : Retinal pigment epithelium (RPE), retinal organoids (RO), and retina-on-a-chip (RoC) were established using CLN2 patient-derived induced pluripotent stem cells as in vitro ocular model of CLN2. The phenotype of the untreated model was characterized and compared with spectral domain OCT macular cube scans collected in children with ERT-treated classic CLN2. In addition, the model was incubated with RGX-381 and treatment effect was assessed.

Results : In vitro analysis demonstrated that TPP1 was expressed by RPE and photoreceptors (PR) in controls but was absent in CLN2-derived cells. Lysosomal waste accumulation, represented by subunit C of mitochondrial ATP Synthase (SCMAS), was pronounced in CLN2 PR regions and absent in CLN2 RPE over the time studied, corresponding with progressive PR loss and RPE preservation during early and mid-stage disease on OCT. Treatment of ROs and RoCs with RGX-381 restored TPP1 expression in a dose dependent manner, resulting in delay, prevention or reversal of SCMAS accumulation in CLN2 ROs and RoCs.

Conclusions : These results demonstrate recapitulation of the CLN2 ocular disease phenotype in a novel in vitro model, as well as the potential for prevention or reversal of lysosomal storage material accumulation with administration of RGX-381 gene therapy. Based on these results, a first-in-human study of subretinal RGX-381 for the treatment of ocular manifestations of CLN2 disease is planned.

This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.