Superior Retinal Gene Transfer and Biodistribution Profile of Subretinal Versus Intravitreal Delivery of AAV8 in Nonhuman Primates

PURPOSE. To investigate shedding and biodistribution characteristics of recombinant adeno-associated virus serotype 8 (rAAV8) after single-dose subretinal or intravitreal injection in nonhuman primates (NHP, Macacafascicularis) as a surrogate for environmental hazard and patient safety. METHODS. In a study for regulatory submission, 22 NHP were divided into four cohorts receiving either single subretinal injections of vehicle or clinical grade rAAV8 (1 X 10(11) or 1 X 10(12) vector genomes [vg]) versus single intravitreal application of 1 x 10(12) vg. Viral shedding and biodistribution were monitored in biofluids for up to 91 days, followed by necropsy and tissue harvesting of all major organs, the visual pathway, and lymphatic tissue. Quantification of vector genomes was done by quantitative (q) PCR. RESULTS. Shedding occurred in a dose-dependent manner in all biofluids and persisted for a maximum of 7 days. Intravitreal delivery led to increased and persistent (up to 13 weeks) distribution of vector genomes in blood and draining lymphatic tissue, increased off-target deposition, and inefficient gene transfer to the retina. No vector targeting of the germ line was observed in any cohort. CONCLUSIONS. These data illustrate that subretinal application of rAAV8 leads to a more favorable biodistribution profile compared to intravitreal injections. Extraocular biodistribution is limited after subretinal delivery, while intravitreal injection leads to both greater and more persistent systemic exposure, evident in blood and lymphatic tissues. With the knowledge on the dynamics of shedding in a setting mimicking clinical application, guidelines can be developed to refine clinical trial protocols to reduce the risk for trial subjects and their environment.