Activating frataxin expression by single-stranded siRNAs targeting the GAA repeat expansion

Area of Science:

• Neurogenetics
• Molecular Biology
• Drug Discovery

Background:

• Friedreich's ataxia (FRDA) is a neurodegenerative disease caused by decreased frataxin (FXN) protein levels.
• Genetic cause is an expanded GAA repeat in the FXN gene, leading to reduced FXN expression.
• Therapeutic strategies aim to increase FXN protein expression.

Purpose of the Study:

• To evaluate novel nucleic acid-based compounds for their efficacy in increasing FXN protein expression.
• To compare the potency of different chemical modifications of antisense oligonucleotides (ASOs) and explore single-stranded siRNAs (ss-siRNAs).

Main Methods:

• Testing two series of compounds, including ASOs with butane linkers and ss-siRNAs, in patient-derived cell lines.
• Assessing the ability of these compounds to activate FXN protein expression.
• Evaluating compound potency and correlating it with biophysical properties like T_m values.

Main Results:

• ASOs with butane linkers demonstrated low potency, potentially due to conformational flexibility and low T_m values.
• Single-stranded siRNAs (ss-siRNAs) exhibited nanomolar potencies, indicating high efficacy.
• ss-siRNAs effectively combine beneficial aspects of dsRNA and ASO approaches.

Conclusions:

• ss-siRNAs represent a potent and viable option for developing nucleic acid therapeutics for FRDA.
• This study expands the therapeutic development landscape for FRDA by introducing effective ss-siRNA candidates.
• Further development of ss-siRNAs could lead to novel treatments for this incurable neurodegenerative disorder.