Safety and Biodistribution Evaluation of rAAV2tYF-CB-hRS1, a Recombinant Adeno-Associated Virus Vector Expressing Retinoschisin, in RS1-Deficient Mice.

Applied Genetic Technologies Corporation is developing a recombinant adeno-associated virus (rAAV) vector for treatment of X-linked retinoschisis (XLRS), an inherited retinal disease characterized by splitting (schisis) of the layers of the retina, which causes poor vision. We report here results of a study evaluating the safety and biodistribution of rAAV2tYF-CB-hRS1 in RS1-deficient mice. Three groups of male RS1-deficient mice received an intravitreal injection in one eye of either vehicle, or rAAV2tYF-CB-hRS1 at one of two dose levels (1 × 10(9) or 4 × 10(9) vg/eye) and were sacrificed 30 or 90 days later. The intravitreal injection procedure was well tolerated in all groups, with no test article-related changes in ophthalmic examinations. Two low-dose vector-treated animals had minimally to mildly higher white blood cell counts at day 90. There were no other intergroup differences in hematology or clinical chemistry analyses and no test article-related gross necropsy observations. Microscopic pathology results demonstrated minimal to slight mononuclear cell infiltrates in 80% of vector-injected eyes at day 30 and 20% of vector-injected eyes at day 90. Immunohistochemistry studies showed RS1 labeling of the retina in all vector-treated eyes. At the day 90 sacrifice, there was a decrease in the severity of splitting/disorganization of the inner nuclear layer of the retina in high-dose vector-treated eyes. Biodistribution studies demonstrated vector DNA in vector-injected eyes but not in any nonocular tissue. These results support the use of rAAV2tYF-CB-hRS1 in clinical studies in patients with XLRS.