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.
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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

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Figure 4

i.t. AAV9/AP4M1 treatment generated minimal IFN-γ responses to AAV9 capsid or AP4M1 peptides, minimal effects on serum toxicity panels, male or female body weight, or survival rates.

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i.t. AAV9/AP4M1 treatment generated minimal IFN-γ responses to AAV9 caps...
(A–G) Vehicle or low (1.25 × 1011 vg/mouse), mid (2.5 × 1011 vg/mouse), or high (5 × 1011 vg/mouse) doses of AAV9/AP4M1 vector were administered intrathecally to balanced numbers of male and female KO mice at P90, with WT and Het mice as normal controls. At 3 weeks after injection, (A and B) mouse splenocytes and serum were collected for ELISpot and (C–G) toxicity panel analyses. Each data point represents a measurement from an individual animal (n = 5–8), with lines representing the mean ± SEM. Data sets that passed tests for normality or homogeneity of variance were analyzed using 1-way ANOVA, with α set at 0.05, and Dunnett’s correction for relevant pairwise comparisons. Data sets that did not pass tests for normality or homogeneity of variance were analyzed using Kruskal-Wallis test, with α set at 0.05, and Dunn’s correction for relevant pairwise comparisons. No significant differences were observed. (H and I) Male (n = 7–26) and female (n = 5–24) mouse body weights were monitored up to 52 weeks of age. Two-way ANOVA with repeated measures was used for statistical analysis. (J) Mouse survival shown with Kaplan-Meier survival curves compared with log-rank (Mantel-Cox) test. No significant differences were observed. AAV9, adeno-associated virus 9; ALB, albumin; AP4M1, adaptor protein complex, subunit μ4; AST, aspartate transaminase; BUN, blood urea nitrogen; CK, creatine kinase; Het, heterozygotes; i.t., intrathecal; TBIL, total bilirubin; vg, vector genome.