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Updated: Oct 8, 2025
Evaluation of Exon Inclusion Induced by Splice Switching Antisense Oligonucleotides in SMA Patient Fibroblasts
Published on: May 11, 2018
Suppression of mutant C9orf72 expression by a potent mixed backbone antisense oligonucleotide
Hélène Tran1, Michael P Moazami2, Huiya Yang1
1Department of Neurology, University of Massachusetts Medical School, Worcester, MA, USA.
Abstract:
Expansions of a G4C2 repeat in the C9ORF72 gene are the most common genetic cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD), two devastating adult-onset neurodegenerative disorders. Using C9-ALS/FTD patient-derived cells and C9ORF72 BAC transgenic mice, we generated and optimized antisense oligonucleotides (ASOs) that selectively blunt expression of G4C2 repeat-containing transcripts and effectively suppress tissue levels of poly(GP) dipeptides. ASOs with reduced phosphorothioate content showed improved tolerability without sacrificing efficacy. In a single patient harboring mutant C9ORF72 with the G4C2 repeat expansion, repeated dosing by intrathecal delivery of the optimal ASO was well tolerated, leading to significant reductions in levels of cerebrospinal fluid poly(GP). This report provides insight into the effect of nucleic acid chemistry on toxicity and, to our knowledge, for the first time demonstrates the feasibility of clinical suppression of the C9ORF72 gene. Additional clinical trials will be required to demonstrate safety and efficacy of this therapy in patients with C9ORF72 gene mutations.
Insights
Antisense oligonucleotides (ASOs) effectively reduced toxic C9ORF72 gene G4C2 repeat transcripts and poly(GP) in cells, mice, and one patient. This offers a potential new therapy for amyotrophic lateral sclerosis and frontotemporal dementia.
Area of Science:
- Neuroscience
- Genetics
- Biochemistry
Background:
- Expansions in the C9ORF72 gene's G4C2 repeat are the primary genetic cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD).
- These neurodegenerative disorders significantly impact adult-onset neurological function.
Purpose of the Study:
- To develop and optimize antisense oligonucleotides (ASOs) targeting G4C2 repeat expansions in the C9ORF72 gene.
- To evaluate the efficacy and tolerability of ASOs in reducing toxic repeat transcripts and dipeptide proteins.
Main Methods:
- Utilized patient-derived cells and C9ORF72 BAC transgenic mice for ASO development and testing.
- Optimized ASO chemistry, specifically reducing phosphorothioate content, to enhance tolerability.
- Administered ASOs via intrathecal delivery in a single patient with a C9ORF72 mutation.
Main Results:
- ASOs selectively reduced G4C2 repeat-containing transcripts and suppressed poly(GP) dipeptide levels in preclinical models.
- ASOs with reduced phosphorothioate content demonstrated improved tolerability without compromising efficacy.
- Intrathecal ASO administration in a patient led to significant reductions in cerebrospinal fluid poly(GP) levels and was well tolerated.
Conclusions:
- This study demonstrates the feasibility of using ASOs to clinically suppress the C9ORF72 gene.
- Optimized ASO chemistry can improve tolerability while maintaining therapeutic efficacy.
- Further clinical trials are necessary to confirm the safety and effectiveness of this ASO therapy for C9ORF72-associated ALS and FTD.
