Ocular Safety of AAV2.7m8-ChrimsonR-tdTomato (GS030-DP) following intravitreous injection and exposure to 595 nm LED light in blind rd1 mice

Abstract

Purpose : GS030-DP, AAV2.7m8 encoding ChrimsonR, an algal light-sensitive opsin, fused to tdTomato, converts retinal ganglion cells into photoactivatable cells and is intended to restore vision in retinitis pigmentosa patients. The objective of this study was to characterize the ocular toxicity of GS030-DP in a relevant animal model following transgene product expression and exposure to the 595 nm LED light required for opsin activation.

Methods : Groups of rd1 (C3H/HeNCrL) mice (5 to 7 weeks old) received either vehicle or GS030-DP [7.84 x 10⁹ vector genomes (vg)/eye] by intravitreous injection (1μL/eye) to both eyes. After 5 weeks post injection, subgroups (6/sex) within each treatment group were anesthetized and exposed to either room light or pulsed (0.81 Hz) 595 nm LED light at 1.4x10¹⁶ or 1.7x10¹⁷ photons/cm2/s (using a purpose-built illumination device). Animals were monitored for 2 weeks following light exposure after which they were euthanized. Eyes were examined microscopically for the presence of ChrimsonR-tdTomato and morphological changes.

Results : Minimal to marked ChrimsonR-tdTomato immunolabeling was demonstrated in retinas of all GS030-DP animals, and was generally characterized by multifocal staining of cell processes in the inner plexiform and nerve fiber layers and perikarya in the ganglion cell layer. Minimal to moderate ChrimsonR staining was also observed in axons of optic nerves. No GS030-DP-related findings were observed upon slit-lamp biomicroscopic or indirect ophthalmoscopic examination and no LED light-related retinal findings were noted at either light intensity. Following the light exposure period, cataract and corneal findings (edema, vascularization, ulcer) were noted in vehicle control and GS030-DP treated groups exposed to room or LED lighting conditions, and were considered secondary to the light exposure procedure (anesthesia, mydriatic, lubricant). Microscopic evaluation did not identify GS030-DP-related findings in the eyes or optic nerves, and no LED light related findings were identified in the retina.

Conclusions : Intravitreous GS030-DP at 7.84 x 10⁹ vg/eye was well-tolerated in rd1 mice and its expression combined with 595 nm LED light exposure was not associated with toxicity in retina or optic nerve.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.