B5 - Neurologic Diseases (excluding Ophthalmic and Auditory Diseases)
32: Promoter Influences Acute Liver Toxicity and Long-Term Hepatic Genotoxicity in rAAV SMA Gene Therapy in Mice
Type: Oral Abstract Session
Presentation Details
Session Title: Neurologic Diseases I
The use of recombinant adeno-associated viruses (rAAVs) for human gene therapy has been a significant breakthrough, demonstrating therapeutic efficacy in an increasing number of clinical trials. However, liver toxicity is one of the major safety concerns. Onasemnogene abeparvovec (Zolgensma®) is an approved rAAV gene therapy for infants with spinal muscular atrophy (SMA). Currently, over 3,000 patients have been treated with Zolgensma. The high systemic dose at 1.1 x 1014 vector genomes/kg is required for efficacy but is associated with safety concerns as warned by a black box warning for severe liver injury and acute liver failure which is likely caused by strong ubiquitous expression of SMN1. We previously developed a second-generation SMA gene therapy expressing a codon-optimized hSMN1 transgene driven by a promoter derived from the native hSMN1 gene. This vector restored SMN expression close to physiological levels in the central nervous system and other major tissues of a severe SMA mouse model. In a head-to-head comparison between the 2nd-generation SMA gene therapy (SMA GTx) and a benchmark vector with a design identical to Zolgensma, the 2nd-gen. SMA GTx showed improved efficacy including a longer life span; increased motor, cardiac, and respiratory functions; and minimal peripheral tissue manifestations. Here, we investigated those two vectors for acute liver toxicity in SMA mice and long-term hepatic genotoxicity in C57BL/6 mice. We first assessed transaminitis by measuring ALT and AST levels in SMA mice on Day 30 after treatment with the benchmark or 2nd-gen vector. SMA GTx vector at a dose of 3.3E+14 vg/kg by facial vein injection at P0. We detected significant elevations of ALT and AST in the benchmark vector-treated mice (150.4 U/L and 290.8 U/L respectively) but not in the 2nd-gen. vector-treated mice (35.2 U/L and 93.3 U/L, respectively, p <0.01 for both comparisons) which were statistically indistinguishable from healthy carrier littermates (p >0.96 for both comparisons). We next compared liver toxicities of the two vectors after intracerebroventricular (ICV) administration to C57BL/6 mice at P0 with a dose of 1.0E+14 vg/kg. In a 20-month study duration, we found ~44% (8/18) of mice died in the benchmark group, and 6% (1/17) of mice died in the 2nd-generation vector group. Among the surviving mice, all the animals (10/10) from the benchmark group developed hepatocellular carcinoma (HCC). In contrast, only one mouse (1/16) in the 2nd-gen vector group detected liver tumors. In addition, significant elevations of ALT and AST were found in the benchmark vector-treated mice (620.2 ± 410.7 U/L and 1518.2 ± 1097.0 U/L respectively) but not in 2nd-generation vector-treated mice (20.6 ± 3.0 U/L and 49.4 ± 6.1 U/L, respectively, p <0.05 for both comparisons). We further analyzed the expressions of Dlk1, Rian, Mir543, Mirg, Mir300, Mir134, Mir1188, Mir382, and Mir487b which are associated with AAV genome integration-related hepatic genotoxicity. Our RT-ddPCR data revealed significant increases in the expression of these 9 genes in the liver tumors as compared to that of the tumor-adjacent tissues and livers from untreated C57BL/6 mice. Importantly, ICV delivery of 2nd gen. vector to SMA mice at P1 achieved significantly better therapeutic efficacy as compared to the benchmark vector. In sum, endogenous hSMN1 promoter-mediated SMA expression holds a promise to not only enhance therapeutic efficacy but also mitigate acute and long-term liver toxicity in AAV gene therapy. * G.G., and J.X are co-corresponding authors
Plain Language Summary
N/A
Xiupeng Chen, Qing Xie, Hao Liu, Veena Kumanan, Hong Ma, Phillip WL Tai, Guangping Gao*, Jun Xie*
Horae Gene Therapy Center, UMass Chan Medical School, Worcester, MA"
Find This Session