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

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 <i>SOD1</i>, a gene commonly mutated in familial ALS, using an adeno-associated virus (AAV) encoding an artificial microRNA (miRNA) that targeted <i>SOD1</i> In a superoxide dismutase 1 (SOD1)-mediated mouse model of ALS, we have previously demonstrated that <i>SOD1</i> 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 (<i>Macaca fascicularis</i>) 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 <i>SOD1</i> Results demonstrated efficient delivery and effective silencing of the <i>SOD1</i> gene in motor neurons. These results support the notion that gene therapy with an artificial miRNA targeting <i>SOD1</i> is safe and merits further development for the treatment of mutant <i>SOD1</i>-linked ALS.