Preparation for a Gene Therapy Trial for LCA5-Associated Retinal Degenerations: Treatment Potential in Patients and Dose-ranging Studies in Non-human Primates

Abstract

Purpose : Mutations in LCA5, which encodes lebercilin, account for one of the most severe forms of early-onset blindness, Leber congenital amaurosis (LCA5-LCA). Currently, there are no treatments for this disease. In our previous studies, early delivery of a AAV8-hLCA5 by subretinal injection in knockout mice partially reversed the severe retinal degeneration. In this study we explore the treatment potential of a group of patients with LCA5-LCA and assessed the safety of subretinal delivery of AAV8-hLCA5 in non-human primates (NHPs) in a dose-ranging study.

Methods : Six patients (ages 6-31 years) with LCA5-LCA underwent ophthalmic exams, full-field stimulus testing, and multimodal imaging with fundus autofluorescence and spectral-domain optical coherence tomography over 3- 5 years. In anticipation of Good Laboratory Practices (GLP) studies, we assessed the safety of subretinal injections of two doses (3E10vg and 1E11vg) of AAV8-hLCA5in NHPs. A control animal was injected with excipient. Retinal imaging matching the protocols used in patients was performed prior to euthanasia (d43 post-injection); retina tissue was evaluated for histopathology and LCA5 immunofluorescence.

Results : Visual acuity in the patients ranged from light perception to 20/200 and there was at least ~4 log units of dark-adapted sensitivity loss. Vision declined slightly during the observation period in some patients. Despite the severe retinal dysfunction, patients showed detectable photoreceptors in the pericentral and midperipheral retina. Subretinal delivery of AAV8-hLCA5 at 3E10 or 1E11vg/eye in NHPs was well-tolerated. There were mild injection-related changes in retinal architecture. There were minimal inflammatory cells in the vitreous and mild thinning of the outer nuclear layer in the eye injected with the higher dose (1E11 vg). AAV8-hLCA5 transduces photoreceptors and RPE cells in the exposed area in the NHP retina.

Conclusions : Detectable but severely dysfunctional photoreceptors in the central and midperipheral retina of patients with LCA5-LCA suggest these regions may be targets for gene augmentation. Subretinal delivery of AAV8-hLCA5 was safe at 1E10vg and there was mild inflammation at 1E11vg. The results of this study provide guidance for the doses to be used in a GLP NHP study and ultimately a human clinical trial.

This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.