AAV-based delivery of RNAi targeting ataxin-2 improves survival and pathology in TDP-43 mice

Amyotrophic lateral sclerosis (ALS) involves motor neuron death due to mislocalized TDP-43. Pathologic TDP-43 associates with stress granules (SGs), and lowering the SG-associated protein ataxin-2 (ATXN2) using Atxn2-targeting antisense oligonucleotides prolongs survival in TAR4/4 sporadic ALS mice but failed in clinical trials likely due to poor target engagement. Here we show that an AAV with potent motor neuron transduction delivering Atxn2-targeting miRNAs reduces Atxn2 throughout the central nervous system at doses 40x lower than published work. In TAR4/4 mice, miAtxn2 increased survival (50%) and strength, and reduced motor neuron death, inflammation, and phosphorylated TDP-43. TAR4/4 transcriptomic dysregulation recapitulated ALS gene signatures that were rescued by miAtxn2, identifying potential therapeutic mechanisms and biomarkers. In slow progressing hemizygous mice, miAtxn2 slowed disease progression, and in ALS patient-derived lower motor neurons, our AAV vector transduced >95% of cells and potently reduced ATXN2 at MOI 4 logs lower than previously reported. These data support AAV-RNAi targeting ATXN2 as a translatable therapy for sporadic ALS.