199. Initial Safety Evaluation of rAAV-hCNGB3 Vectors in Nonhuman Primates
Authors: Guo-jie Ye, Ewa Budzynski, Peter Sonnentag, Leslie E. McPherson, T. Michael Nork, James VerHoeve, Paul Miller, Jeffrey D. Chulay
Journal: Molecular Therapy (2015)

Studies in CNGB3-mutant dogs have shown that subretinal injection of AAV5-PR2.1-hCNGB3 can rescue the ACHM ERG phenotype (Komaromy, 2010). However, at high doses many of the animals developed chorioretinitis (Komaromy, unpublished data) and this toxicity is consistent with an immune response to a foreign protein (hCNGB3 has only 76% identity with canine CNGB3), but could also be a result of overexpression of hCNGB3. AGTC is developing a rAAV-hCNGB3 vector for treatment of humans with achromatopsia caused by CNGB3 mutations. Here we report an initial evaluation of the safety of rAAV-hCNGB3 vectors in nonhuman primates (macaque CNGB3 has 95% identity with hCNGB3), this study may contribute to our understanding of potential immune responses to the xenogeneic CNGB3 and help to guide the development of rAAV-CNGB3 gene therapy for human patients. Eight cynomolgus macaques were assigned to four groups and received bilateral subretinal injections of AAV2tYF-hCNGB3, or AAV5-hCNGB3, as indicated in Table 1. Ophthalmic examinations, digital fundus photography, scotopic and photopic electroretinography (ERG) and visual evoked potentials (VEP), and histology were used to evaluate ocular tolerability of test article.Table 1NHP Study DesignGroupTest ArticleNo. of AnimalsDose Level (vg/eye)Dose Concentration (vg/mL)1 (Low)rAAV5-PR2.1-CNGB324.0E+102.88 E+112 (Low)rAAV2tYF-PR2.1-hCNGB324.0E+102.88 E+113 (High)rAAV5-PR2.1-hCNGB324.0E+112.88 E+124 (High)rAAV2tYF-PR2.1-hCNGB324.0E+112.88 E+12 Open table in a new tab Test article-related ophthalmic findings include mild (Trace to 1+) to moderate (2+) but occasionally moderately severe (3+) to severe (4+) anterior and posterior segment inflammatory response that resolved without sequelae. No test article-related ERG or cortical visual evoked potential (VEP) effects were observed. Microscopic findings associated with injection of the test articles included minimal retinal degeneration, hypertrophy of retinal pigment epithelium, and/or mononuclear cell infiltrates of the choroid and/or retina. Mononuclear cell infiltrates generally correlated with the subretinal foci noted ophthalmoscopically. The inflammatory response tended to be less in eyes given rAAV5-hCNGB3 versus rAAV2tYF-hCNGB3 and in eyes given 4 × 10^10 versus 4 × 10^11 vg/eye. Both AAV2tYF-hCNGB3 and AAV5-hCNGB3 were well tolerated after subretinal injection in in NHPs at a dose level of 4 × 10^10 or 4 × 10^11 vg/eye. Test article related findings included dose-dependent ocular inflammation that resolved by Study Week 12. No test article-related ERG or cortical visual evoked potential (VEP) effects were observed. In contrast to the severe inflammation noted in dogs receiving high dose of AAV5-hCNGB3 that usually resulted in involuntary early termination of the animals, the milder test article-related findings in macaques receiving AAV-hCNGB3 vectors that expresses a highly homologous xenogeneic human protein is helpful for guiding future development of rAAV-CNGB3 gene therapy for human patients.