Abstract Details

Read the abstract and find the presentation below

Full text and presentation details

E - Disease Models and Clinical Applications -> Neurologic Diseases

263: Endogenous Human SMN1 Promoter-Driven Gene Replacement Improves the Efficacy and Safety of AAV9-Mediated Gene Therapy for Spinal Muscular Atrophy (SMA) in Mice

Type: Poster Session

Poster Board Number: M-144
Presentation Details
Session Title: Neurologic Diseases I
Location: Hall D
Start Time: 5/16/2022 17:30
End Time: 5/16/2022 18:30

Zolgensma®, an FDA-approved scAAV9 ubiquitously expressing a human SMN1 cDNA transgene under cytomegalovirus enhancer/chicken β-actin promoter (CMVen/CB-hSMN1), is a significant breakthrough for treating SMA. Nonetheless, a high dose of the vector is required, leading to liver damage and hematologic complications in most patients. Severe toxicities were also found in nonhuman primates and piglets with AAV9-like vectors expressing hSMN1. Here, we hypothesize that restoration of physiological levels of hSMN1 expression in the appropriate cell types with the lowest effective dose of vector may be essential for the next generation SMA gene therapy. By optimizing the coding sequence of hSMN1 (co-hSMN1) under CMVen/CB promoter, we increased hSMN1 protein expression by ~8 fold over the published Zolgensma® construct in Neuro2a cells. However, when we treated postnatal day 1 SMNdelta7 mice with this potent vector rAAV9-CMVen/CB-co-hSMN1 at 3.3 x10e14 GCs/kg by facial vein administration, all treated animals (n = 6) died earlier than the untreated SMA mice. H&E staining of liver sections at day 8 revealed severe liver damage in both SMA mice and their healthy littermates treated with this vector, suggesting that the early lethality was likely to be associated with hepatic overexpression of hSMN1. In an attempt to achieve physiologically regulated hSMN1 expression, we created a second generation (2nd gen) scAAV9 vector expressing co-hSMN1 from an endogenous hSMN1 promoter (i.e., scAAV9-SMN1p-co-hSMN1) and injected neonatal SMA mice with either 3.3x10e14 GCs/kg (High dose, n = 9) or 1.1 x10e14 GCs/kg (Low dose, n = 12). We also dosed another group of SMA mice with 3.3x10e14 GCs/kg (high dose only, n = 13) of scAAV9-CMVen/CB-hSMN1 harboring the same expression cassette as used in Zolgensma® as the benchmark vector. This side-by-side comparison study revealed that our novel 2nd gen vector has therapeutic potential overcoming the current SMA treatment limitations, which is supported by the following key findings. 1) All the mice injected with the high dose 2nd gen vector survived until the full 90-day study period compared with 60 days median survival from benchmark vector-treated mice. 2) The high dose 2nd gen vector-treated female mice gained more body weight than the benchmark vector group starting from Day 25, while the low dose group showed similar body weights as the high dose benchmark vector. The average body weights of the treated male mice were equal in all three groups. 3) The high dose 2nd gen vector-treated mice have a faster righting response than benchmark vector-treated mice (Day 3-7 vs Day 7-13). In addition, the low dose group, also had an earlier righting response (Day 3-9) than the high dose benchmark vector group. 4) Rotarod tests of surviving mice at Days 30 and 80 showed comparable performances in all three groups. 5) At Day 60, 67% of mice treated with the benchmark vector developed ear necrosis, while none of the high dose 2nd gen vector-treated mice had ear necrosis at Day 90. In the low dose group, 33% of mice showed ear necrosis at Day 90. 6) The structures of neuromuscular junctions in the 2nd gen vector-treated mice were restored to that of wild-type mice, better than those of benchmark-treated SMA mice. 7) Less liver hSMN1 expression was detected from 2nd gen vector-treated healthy mice than the benchmark vector at Day 3 and Day 8, suggesting its potential to reduce hSMN1 expression associated liver toxicity. In summary, our novel hSMN1 AAV gene therapy vector consisting of the endogenous SMN1 promoter and codon-optimized hSMN1 has improved potency and safety profile as compared to the Zolgensma® vector, holding promise for clinical applications.

Qing Xie1, Hong Ma1, Xiupeng Chen1, Yunxiang Zhu2, Yijie Ma2, Leila Jalinous2, Qin Su1, Phillip Tai1, Guangping Gao1, Jun Xie1

1UMASSMED, Worcester, MA,2CANbridge Pharmaceuticals, Boston, MA
 Q. Xie: None.

This site uses cookies to offer you a better user experience and to analyze site traffic. By continuing to use this website, you accept our use of cookies.