RNAi-mediated silencing of SOD1 profoundly extends survival and functional outcomes in ALS mice

Alexandra Weiss; James W Gilbert; Iris Valeria Rivera Flores; Jillian Belgrad; Chantal Ferguson; Elif O Dogan; Nicholas Wightman; Kit Mocarski; Dimas Echeverria; Ashley L Harkins; Ashley Summers; Brianna Bramato; Nicholas McHugh; Raymond Furgal; Nozomi Yamada; David Cooper; Kathryn Monopoli; Bruno M D C Godinho; Matthew R Hassler; Ken Yamada; Paul Greer; Nils Henninger; Robert H Brown Jr; Anastasia Khvorova

doi:10.1016/j.ymthe.2025.05.010

RNAi-mediated silencing of SOD1 profoundly extends survival and functional outcomes in ALS mice

Mol Ther. 2025 May 9:S1525-0016(25)00380-6. doi: 10.1016/j.ymthe.2025.05.010. Online ahead of print.

Authors

Alexandra Weiss¹, James W Gilbert², Iris Valeria Rivera Flores², Jillian Belgrad², Chantal Ferguson², Elif O Dogan¹, Nicholas Wightman¹, Kit Mocarski³, Dimas Echeverria², Ashley L Harkins⁴, Ashley Summers², Brianna Bramato², Nicholas McHugh², Raymond Furgal², Nozomi Yamada², David Cooper², Kathryn Monopoli², Bruno M D C Godinho², Matthew R Hassler², Ken Yamada², Paul Greer⁵, Nils Henninger⁶, Robert H Brown Jr⁷, Anastasia Khvorova⁸

Affiliations

¹ Department of Neurology, UMass Chan Medical School, Worcester, MA 01605, USA.
² RNA Therapeutics Institute, UMass Chan Medical School, Worcester, MA 01605, USA.
³ Department of Neurology, UMass Chan Medical School, Worcester, MA 01605, USA; Program in Molecular Medicine, UMass Chan Medical School, Worcester, MA 01605, USA.
⁴ Department of Neurology, UMass Chan Medical School, Worcester, MA 01605, USA; Department of Genetic & Cellular Medicine, UMass Chan Medical School, Worcester, MA 01605, USA.
⁵ Program in Molecular Medicine, UMass Chan Medical School, Worcester, MA 01605, USA.
⁶ Department of Neurology, UMass Chan Medical School, Worcester, MA 01605, USA; Department of Psychiatry, UMass Chan Medical School, Worcester, MA 01605, USA.
⁷ Department of Neurology, UMass Chan Medical School, Worcester, MA 01605, USA. Electronic address: robert.brown@umassmed.edu.
⁸ RNA Therapeutics Institute, UMass Chan Medical School, Worcester, MA 01605, USA; Program in Molecular Medicine, UMass Chan Medical School, Worcester, MA 01605, USA. Electronic address: anastasia.khvorova@umassmed.edu.

PMID: 40349108
DOI: 10.1016/j.ymthe.2025.05.010

Abstract

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative condition, with 20% of familial and 2%-3% of sporadic cases linked to mutations in the cytosolic superoxide dismutase (SOD1) gene. Mutant SOD1 protein is toxic to motor neurons, making SOD1 gene suppression a promising approach, supported by preclinical data and the 2023 Federal Drug Administration (FDA) approval of the GapmeR ASO targeting SOD1, tofersen. Despite the approval of an ASO and the optimism it brings to the field, the pharmacodynamics and pharmacokinetics of therapeutic SOD1 modulation can be improved. Here, we developed a chemically stabilized divalent siRNA scaffold (di-siRNA) that effectively suppresses SOD1 expression in vitro and in vivo. With optimized chemical modification, it achieves remarkable CNS tissue permeation and SOD1 silencing in vivo. Administered intraventricularly, di-siRNA^SOD1 extended survival in SOD1-G93A ALS mice, increasing survival beyond that previously seen in these mice by ASO modalities, slowed disease progression according to the standard ALS preclinical endpoints, and attenuated ALS neuropathology. These properties offer an improved therapeutic strategy for SOD1-mediated ALS and may extend to other dominantly inherited neurological disorders.

Keywords: ASO; RNAi; amyotrophic lateral sclerosis; siRNA; translational.