Oligonucleotide therapy mitigates disease in spinocerebellar ataxia type 3 mice

Objective Spinocerebellar ataxia type 3 (SCA3), also known as Machado–Joseph disease, is the most common dominantly inherited ataxia. Despite advances in understanding this CAG repeat/polyglutamine expansion disease, there are still no therapies to alter its progressive fatal course. Here, we investigate whether an antisense oligonucleotide (ASO) targeting the SCA3 disease gene, ATXN3 , can prevent molecular, neuropathological, electrophysiological, and behavioral features of the disease in a mouse model of SCA3. Methods The top ATXN3‐ targeting ASO from an in vivo screen was injected intracerebroventricularly into early symptomatic transgenic SCA3 mice that express the full human disease gene and recapitulate key disease features. Following a single ASO treatment at 8 weeks of age, mice were evaluated longitudinally for ATXN3 suppression and rescue of disease‐associated pathological changes. Mice receiving an additional repeat injection at 21 weeks were evaluated longitudinally up to 29 weeks for motor performance. Results The ATXN3 ‐targeting ASO achieved sustained reduction of polyglutamine‐expanded ATXN3 up to 8 weeks after treatment and prevented oligomeric and nuclear accumulation of ATXN3 up to at least 14 weeks after treatment. Longitudinal ASO therapy rescued motor impairment in SCA3 mice, and this rescue was associated with a recovery of defects in Purkinje neuron firing frequency and afterhyperpolarization. Interpretation This preclinical study established efficacy of ATXN3 ‐targeted ASOs as a disease‐modifying therapeutic strategy for SCA3. These results support further efforts to develop ASOs for human clinical trials in this polyglutamine disease as well as in other dominantly inherited disorders caused by toxic gain of function. Ann Neurol 2018;83:64–77