Intrathecal AAV9/AP4M1 gene therapy for hereditary spastic paraplegia 50 shows safety and efficacy in preclinical studies
Xin Chen, … , Darius Ebrahimi-Fakhari, Steven J. Gray
Xin Chen, … , Darius Ebrahimi-Fakhari, Steven J. Gray
Published March 23, 2023
Citation Information: J Clin Invest. 2023;133(10):e164575. https://doi.org/10.1172/JCI164575.
View: Text | PDF
Research Article Neuroscience

Intrathecal AAV9/AP4M1 gene therapy for hereditary spastic paraplegia 50 shows safety and efficacy in preclinical studies

Abstract

Spastic paraplegia 50 (SPG50) is an ultrarare childhood-onset neurological disorder caused by biallelic loss-of-function variants in the AP4M1 gene. SPG50 is characterized by progressive spastic paraplegia, global developmental delay, and subsequent intellectual disability, secondary microcephaly, and epilepsy. We preformed preclinical studies evaluating an adeno-associated virus (AAV)/AP4M1 gene therapy for SPG50 and describe in vitro studies that demonstrate transduction of patient-derived fibroblasts with AAV2/AP4M1, resulting in phenotypic rescue. To evaluate efficacy in vivo, Ap4m1-KO mice were intrathecally (i.t.) injected with 5 × 1011, 2.5 × 1011, or 1.25 × 1011 vector genome (vg) doses of AAV9/AP4M1 at P7–P10 or P90. Age- and dose-dependent effects were observed, with early intervention and higher doses achieving the best therapeutic benefits. In parallel, three toxicology studies in WT mice, rats, and nonhuman primates (NHPs) demonstrated that AAV9/AP4M1 had an acceptable safety profile up to a target human dose of 1 × 1015 vg. Of note, similar degrees of minimal-to-mild dorsal root ganglia (DRG) toxicity were observed in both rats and NHPs, supporting the use of rats to monitor DRG toxicity in future i.t. AAV studies. These preclinical results identify an acceptably safe and efficacious dose of i.t.-administered AAV9/AP4M1, supporting an investigational gene transfer clinical trial to treat SPG50.

Authors

Xin Chen, Thomas Dong, Yuhui Hu, Raffaella De Pace, Rafael Mattera, Kathrin Eberhardt, Marvin Ziegler, Terry Pirovolakis, Mustafa Sahin, Juan S. Bonifacino, Darius Ebrahimi-Fakhari, Steven J. Gray

×

Figure 2

AAV2/AP4M1 vector restored ATG9A trafficking and AP4E1 levels in primary fibroblasts from patients with SPG50.

Options: View larger image (or click on image) Download as PowerPoint
AAV2/AP4M1 vector restored ATG9A trafficking and AP4E1 levels in primary...
(A) Fibroblasts from 2 sibling patients with a donor splice site pathogenic mutation in intron 14 of the AP4M1 gene (c.1137+1G→T) or normal control fibroblasts were treated without or with AAV2/AP4M1 vector at the indicated MOI for 72 hours. Fibroblasts were then fixed for immunofluorescence analysis of ATG9A, AP4E1, and TGN46, as described in Methods. Nuclei were stained with DAPI (in blue, merge). Single channels are shown in inverted grayscale. Note that expression of AP4M1 by the viral vector caused dispersal of the ATG9A signal and increased AP4E1 staining at the TGN (i.e., phenotypic rescue; indicated by arrows). Scale bar: 20 μm. (B) The percentage of rescued cells was counted and is represented as the mean ± SEM from 2 independent experiments (see Supplemental Table 2 for details). Statistical analysis was done using 2-way ANOVA with repeated measures. AAV2, adeno-associated virus 2; AP4E1, adaptor protein complex, subunit ɛ; AP4M1, adaptor protein complex, subunit μ4; ATG9A, autophagy-related protein 9A; SPG50, spastic paraplegia 50; TGN, trans-Golgi network.