663. Safety and Biodistribution Study of rAAV2tYF-CB-hRS1 in Nonhuman Primates

Abstract

Background: AGTC is developing a recombinant AAV vector expressing retinoschisin (RS1) for treatment of humans with X-linked retinoschisis (XLRS). Here we report results of a toxicology and biodistribution study of this vector administered by intravitreal injection in cynomolgus macaques.Methods: Three groups of male cynomolgus macaques (n=3 per group) received an intravitreal injection in one eye of vehicle or rAAV2tYF-CB-hRS1 at one of two dose levels (4 × 10^10 or 4 × 10^11 vg/eye). Half of the animals were sacrificed 14 days after vector administration and the remaining animals were sacrificed 91 or 115 days after vector administration. At each sacrifice time point blood and tissue samples were collected for evaluation of safety and biodistribution.Results: There were no test article-related effects on intraocular pressure, electroretinography, visual evoked potentials, and clinical pathology parameters. Ocular exams demonstrated a dose-related ocular inflammatory response that improved over time. In the vehicle control group, aqueous cells ranged from trace to 4+ at 1 week after injection and resolved by Week 2. Vitreous cells ranged from trace to 2+ at 2 to 3 weeks, resolved by Week 4 in four animals and in the other two animals were resolved or resolving at Week 12. None of the animals in this group had vitreous haze. Ocular inflammation was greater in the vector-treated animals and was more pronounced at the higher dose. Aqueous cells ranged from 1+ to 4+ at Week 1 in all animals, resolved by Week 2, recurred at Week 2 to 4 in two animals in the low dose and three animals in the high dose group, and then resolved over the next several weeks. Vitreous cells developed in 5 of 6 animals in the low dose and all animals in the high dose group, and persisted at 2+ or greater for more than 4 weeks in two animals in the low dose and three animals in the high dose group. Vitreous haze developed at Week 4 in one animal in the low dose and three animals in the high dose group and resolved over the next several weeks. Microscopic pathology results demonstrated mononuclear infiltrates at the optic disc and/or around blood vessels in the ganglion cell layer, iris, and ciliary body of the injected eye was observed in 2 of 6 animals in the lower dose group and 4 of 6 animals in the higher dose group. Immunohistochemistry studies showed RS1 labelling of the ganglion cell layer at the foveal slope. At terminal sacrifice there was limited vector biodistribution outside the injected eye.Conclusions: Intravitreal administration of rAAV2tYF-CB-hRS1 in normal cynomolgus macaques was associated with dose-related anterior and posterior segment inflammatory response that improved over time. Histological examination showed mononuclear cell infiltrates that were more prevalent at the higher dose level and RS1 expression in the retinal ganglion cell ring was demonstrated by immunohistochemistry. Results from this study support the use of rAAV2tYF-CB-hRS1 in clinical studies in patients with XLRS.