Intracorneal sequential dosing of AAV-ArsB clears corneal opacity associated with mucopolysaccharidosis VI in a feline model

Abstract

Purpose : Mucopolysaccharidosis VI (MPS VI) is a rare, autosomal recessive lysosomal storage disease caused by mutations in the ArsB gene encoding arylsulfatase B. Corneal blindness in MPS VI remains an important factor compromising quality of life and there is no effective treatment. The purpose of this study is to examine the efficacy, toxicity, and immune response to a single and sequential (opposite eye) intracorneal injection of AAV8-ArsB.

Methods : A MPS VI feline, homozygous for a null ArsB mutation and a second, asymptomatic heterozygote, were acquired at 75 days of age. AAV8 vectors packaged with optimized human ArsB cDNA were validated and characterized in vitro (UNC Gene Therapy Center) and injected unilaterally intracorneally (1e9 viral genomes (vg) / 50 uL volume) at 152 days, while the other eye was injected with PBS. Eight weeks following the initial injection, the opposite cornea was injected with AAV8-ArsB (1e9 vg/50 uL). Ophthalmic examinations (slit lamp biomicroscopy, tonometry, pachymetry, ophthalmoscopy, OCT) were performed prior to and following each injection. Corneal confocal microscopy was performed (endothelial cell counts) at 242 days, followed by euthanasia and histological and molecular tissue analyses.

Results : The homozygote MPS VI feline had diffuse mild corneal opacity and peripheral corneal vascularization that progressed until dosing, while the heterozygote had clear corneas. Following both initial and sequential dosing with AAV8-ARSB, the majority of corneal opacity in the homozygote cleared in AAV8-ArsB corneas within 3 weeks of dosing either cornea and remained clear and without signs of inflammation or immune response through the end of the study (90 days after initial injection). No signs of inflammation or toxicity was noted in either eye in the heterozygote following AAV-ArsB dosing.

Conclusions : Results after intracorneal AAV8-ArsB injections in MPS VI felines demonstrate that corneal intrastromal AAV gene therapy is safe and effective to reverse corneal opacity. Importantly, sequential dosing of the opposite eye with intrastromal AAV8-ArsB was clinically effective to clear corneal opacity with no clinical evidence of an inhibitory capsid antibody response or other adverse effects. These results generate optimism for the efficacy and safety for single dose treatments of corneal abnormalities associated with lysosomal storage disorders.

This is a 2021 ARVO Annual Meeting abstract.