Guanine base modifications in antisense oligonucleotides mitigate acute central nervous system toxicity

Area of Science:

• Nucleic acid chemistry
• Neuroscience
• Drug development

Background:

• Antisense oligonucleotides (ASOs) show therapeutic potential for central nervous system (CNS) diseases.
• Neurotoxicity from intrathecal ASO administration limits clinical application.
• Understanding nucleobase modification effects on ASO toxicity is crucial.

Purpose of the Study:

• To investigate the impact of hypoxanthine substitution for nucleobases in ASOs on neurotoxicity and activity.
• To evaluate guanine modifications for mitigating CNS toxicity and maintaining efficacy.

Main Methods:

• In vitro and in vivo assays were used to assess toxicity and activity of modified ASOs.
• Hypoxanthine substitutions for adenine, guanine, and cytosine were tested.
• Guanine modifications, including 7-deazaguanine, were evaluated in mice via intracerebroventricular injection.

Main Results:

• Guanine to hypoxanthine substitution reduced neurotoxicity; adenine or cytosine substitution exacerbated it.
• All hypoxanthine substitutions decreased target RNA binding affinity and in vivo silencing efficacy.
• 7-deazaguanine modification effectively reduced CNS toxicity while preserving ASO silencing activity.

Conclusions:

• Nucleobase identity significantly influences ASO-induced neurotoxicity.
• Guanine modification, specifically 7-deazaguanine, presents a viable strategy to mitigate ASO neurotoxicity for CNS disease treatment.
• This approach maintains therapeutic efficacy, addressing a key limitation in ASO clinical use.