Five-year analysis of efficacy and safety of a bidirectional AAV gene therapy in Tay-Sachs sheep
Toloo Taghian, Jillian Gallagher, Stephanie Bertrand, William C. Baker, Kalajan Lopez Mercado, Hector R. Benatti, Erin Hall, Yvette Lopez, Abigail McElroy, John T. McCarthy, Sanjana Pulaparthi, Deborah Fernau, Samuel Mather, Sophia Esteves, Elise Diffie, Amanda Gross, Hannah G. Lahey, Xuntian Jiang, Elizabeth Parsley, Rachael Gately, Rachel Prestigiacomo, Siauna Johnson, Amanda Taylor, Lindsey Bierfeldt, Susan Tuominen, Jennifer Koehler, Guangping Gao, Jun Xie, Qin Su, Robert King, Matthew J. Gounis, Vania Anagnostakou, Ajit Puri, Ana Rita Batista, Miguel Sena-Esteves, Douglas R. Martin, Heather Gray-Edwards
Toloo Taghian, Jillian Gallagher, Stephanie Bertrand, William C. Baker, Kalajan Lopez Mercado, Hector R. Benatti, Erin Hall, Yvette Lopez, Abigail McElroy, John T. McCarthy, Sanjana Pulaparthi, Deborah Fernau, Samuel Mather, Sophia Esteves, Elise Diffie, Amanda Gross, Hannah G. Lahey, Xuntian Jiang, Elizabeth Parsley, Rachael Gately, Rachel Prestigiacomo, Siauna Johnson, Amanda Taylor, Lindsey Bierfeldt, Susan Tuominen, Jennifer Koehler, Guangping Gao, Jun Xie, Qin Su, Robert King, Matthew J. Gounis, Vania Anagnostakou, Ajit Puri, Ana Rita Batista, Miguel Sena-Esteves, Douglas R. Martin, Heather Gray-Edwards
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Five-year analysis of efficacy and safety of a bidirectional AAV gene therapy in Tay-Sachs sheep

Abstract

Tay-Sachs disease (TSD) and Sandhoff disease are fatal neurodegenerative diseases without an effective therapy that are caused by mutations in the HEXA and HEXB genes, respectively. Together they encode the heterodimeric isozyme of hexosaminidase, hexosaminidase A (HexA), that degrades GM2 ganglioside. This report describes a 5-year-long study using a bidirectional adeno-associated virus 9 (AAV9) vector (AAV9-Bic_HexA/HexB) encoding both HEXA and HEXB in the TSD sheep model. Bidirectional AAV9 was delivered i.v. or through various cerebrospinal fluid (CSF) delivery routes: intracerebroventricular (ICV), cisterna magna (CM), and lumbar intrathecal space (LIT). The longest survival and best distribution were achieved by multipoint CSF delivery (combined CM, ICV, and LIT) with treated animals that survived up to 5 years of age (untreated animals with TSD die after ~9 months). Extension in survival was accompanied by lasting improvement in neurological examination and maze testing. Improvement in biomarkers of efficacy, including MRI, magnetic resonance spectroscopy, diffusion tensor imaging, and CSF levels of GM2 ganglioside and HexA activity, was evident. Postmortem assessments showed broad HexA distribution, GM2 ganglioside clearance, and vector genome distribution, especially in deep brain structures. Therapeutic efficacy documented in this study supports translation of bidirectional vector and multipoint CSF delivery to a clinical trial in patients with TSD and Sandhoff disease.

Authors

Toloo Taghian, Jillian Gallagher, Stephanie Bertrand, William C. Baker, Kalajan Lopez Mercado, Hector R. Benatti, Erin Hall, Yvette Lopez, Abigail McElroy, John T. McCarthy, Sanjana Pulaparthi, Deborah Fernau, Samuel Mather, Sophia Esteves, Elise Diffie, Amanda Gross, Hannah G. Lahey, Xuntian Jiang, Elizabeth Parsley, Rachael Gately, Rachel Prestigiacomo, Siauna Johnson, Amanda Taylor, Lindsey Bierfeldt, Susan Tuominen, Jennifer Koehler, Guangping Gao, Jun Xie, Qin Su, Robert King, Matthew J. Gounis, Vania Anagnostakou, Ajit Puri, Ana Rita Batista, Miguel Sena-Esteves, Douglas R. Martin, Heather Gray-Edwards

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Figure 1

Hexosaminidase structure, AAV design, and improved survival and neurological scores by AAV treatment.

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Hexosaminidase structure, AAV design, and improved survival and neurolog...
(A) Hexosaminidase enzyme has 3 isozymes: HexA, HexB, and HexS. The HexA enzyme hydrolyzes GM2 ganglioside in humans and consists of α and β subunits, encoded by HEXA and HEXB genes, respectively. Deficiency in HEXA and HEXB genes results in TSD and Sandhoff disease, respectively. Hex α- and β-subunit protein x-ray diffraction structure was from the RCSB protein data bank (2GK1 PDB DOI: https//doi.org/10.22.10/pdb2GK1/pdb). (B) Schematics of bicistronic AAV9 vector expressing both HEXA and HEXB in a single AAV. (C) Kaplan-Meier plot of the survival rate of untreated sheep (n = 15) and bicistronic AAV9-treated TSD sheep (TSD+AAV_IV, n = 5; TSD+AAV_CSF_ICV-CM-LIT, n = 5; TSD+AAV_CSF_CM-LIT, n = 3). Survival of the TSD+AAV_IV and TSD+AAV_CSF_ICV-CM-LIT cohorts was significantly different than that of the TSD group (P < 0.001), while survival of TSD+AAV_CSF_CM-LIT cohort was not different than the TSD group (P = 0.059). The log-rank test was used for statistical analysis between cohorts. (D) The neurological score of sheep was described by scoring from 1 (normal) to 5 (worse). The TSD+AAV_CSF_ICV-CM-LIT cohort had significantly decreased scores compared with untreated TSD sheep (*P < 0.05). Scores were analyzed by Mann-Whitney tests, and effect was determined by a Hodges-Lehmann test. The neurological scores were collected at the time of euthanasia, corresponding to the survival curve in C. (E) Total neurological score of sheep over time. Statistical analyses were not completed for these data because some time points only had 1 recording per group (TSD, n = 3; TSD+AAV_IV, n = 5; TSD+AAV_CSF_ICV-CM-LIT, n = 3 up to year 4, and n = 1 at 5 years; TSD+AAV_CSF_CM-LIT, n = 1). (F) Schematic of the maze used to test sheep cognition. (G) Bar chart showing latency to complete the maze for all sheep at 6 months or at 3–4 years of age (6 months: TSD n = 5, WT n = 3, TSD+AAV_IV n = 3, TSD+AAV_CSF-CM-LIT n = 2, TSD+AAV_CSF_ICV-CM-LIT n = 2; 3–4 years: TSD+AAV_ CSF_ICV-CM-LIT n = 3, WT n = 4).