Therapeutic potential of circular antisense oligonucleotides in gene silencing and RNA condensate degradation

Antisense oligonucleotides (ASOs) have emerged as a powerful therapeutic modality for targeting disease-associated RNA. However, most clinical ASOs rely on chemical modifications to improve stability and pharmacokinetics. Here, we present a chemically unmodified circular ASO (C-ASO) platform that exhibits enhanced exonuclease resistance, prolonged gene silencing, and the ability to dissociate RNA condensates. C-ASOs are synthesized via enzymatic ligation and demonstrated superior serum stability over linear ASO (L-ASO). Notably, C-ASOs achieved durable, sequence-specific knock-down comparable to that of phosphorothioate- (PS-) and 2′-O-methoxyethyl- (2′-MOE) modified ASOs, without requiring any chemical modification. In vitro and cellular studies further showed that C-ASO efficiently degraded both synthetic and disease-relevant RNA condensates through RNase H-mediated cleavage. This approach could lead C-ASO as a potential, modification-free antisense platform that overcomes the key drawbacks of linear ASO, especially in diseases driven by pathogenic RNA condensates.