Research ArticleAmyotrophic Lateral Sclerosis

Safe and effective superoxide dismutase 1 silencing using artificial microRNA in macaques

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Science Translational Medicine  31 Oct 2018:
Vol. 10, Issue 465, eaau6414
DOI: 10.1126/scitranslmed.aau6414

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A silent attack on ALS

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disorder for which there are currently no available therapies. Gain-of-function mutations in the gene encoding superoxide dismutase 1 (SOD1) are responsible for 20% of familial ALS cases. Silencing SOD1 using artificial microRNA has been shown to have therapeutic effects in mouse models of ALS. Here, Borel et al. tested the efficacy and safety of intrathecal delivery of SOD1-targeting artificial microRNAs in nonhuman primates. The therapy efficiently reduced SOD1 protein expression without side effects in macaques. The results suggest that this approach is safe and effective, paving the way for further development of this potential therapy.

Abstract

Amyotrophic lateral sclerosis (ALS) is a fatal neurological disease caused by degeneration of motor neurons leading to rapidly progressive paralysis. About 10% of cases are caused by gain-of-function mutations that are transmitted as dominant traits. A potential therapy for these cases is to suppress the expression of the mutant gene. Here, we investigated silencing of SOD1, a gene commonly mutated in familial ALS, using an adeno-associated virus (AAV) encoding an artificial microRNA (miRNA) that targeted SOD1. In a superoxide dismutase 1 (SOD1)–mediated mouse model of ALS, we have previously demonstrated that SOD1 silencing delayed disease onset, increased survival time, and reduced muscle loss and motor and respiratory impairments. Here, we describe the preclinical characterization of this approach in cynomolgus macaques (Macaca fascicularis) using an AAV serotype for delivery that has been shown to be safe in clinical trials. We optimized AAV delivery to the spinal cord by preimplantation of a catheter and placement of the subject with head down at 30° during intrathecal infusion. We compared different promoters for the expression of artificial miRNAs directed against mutant SOD1. Results demonstrated efficient delivery and effective silencing of the SOD1 gene in motor neurons. These results support the notion that gene therapy with an artificial miRNA targeting SOD1 is safe and merits further development for the treatment of mutant SOD1-linked ALS.

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