Stability modification of therapeutic aptamers: from biostability bottlenecks to nuclease-resistant construct design

Nucleic acid aptamers are synthetic, single-stranded oligonucleotides that bind targets with high affinity and specificity, enabling precise and programmable functional modulation. However, low biostability remains a key druggability bottleneck of therapeutic aptamers. In vivo enzymatic lability constitutes a primary pharmacokinetic barrier, impeding systemic exposure, tissue distribution, and sustained target occupancy, all critical determinants of in vivo efficacy. Consequently, rational chemical stabilization via enzyme-resistant modifications has emerged as a cornerstone strategy in aptamer drug development. In this review, we systematically categorize current stabilization approaches across two complementary design dimensions: local-level modifications (including terminal modification, sugar modification, backbone modification, and base modification) and global structural-level engineering (including Spiegelmers, cyclization modification, and multivalent assembly). Furthermore, we discuss persistent translational challenges to illuminate a coherent framework for designing aptamers with high biostability that achieve enhanced nuclease resistance while concurrently exhibiting favorable pharmacokinetics, high target binding affinity and specificity.