Evolution of siRNA Therapeutics: From Mechanistic Foundations to Clinical Expansion.

Since the discovery of RNA interference (RNAi), small interfering RNA (siRNA) has emerged as a transformative therapeutic modality, shifting the paradigm from permanent genomic modification to the flexible interception of genetic information. Despite the delivery gap caused by biological barriers, innovations in chemical stabilization and delivery platforms have propelled siRNA from niche applications to the mainstream management of chronic conditions. This review provides a comprehensive analysis of the distinct mechanistic advantages of siRNA over antisense oligonucleotides, with particular emphasis on its catalytic turnover via the RISC and high target specificity. We further evaluate the critical transition from first-generation lipid nanoparticles to ligand-conjugated systems, specifically trivalent N-acetylgalactosamine (GalNAc). Through an examination of the clinical success of Inclisiran and the recent approval of Plozasiran, we discuss how these advances have improved patient compliance and extended dosing intervals. Furthermore, this article explores the emerging frontier of extra-hepatic delivery and the expansion toward metabolic and oncological targets. Ultimately, this review highlights the potential of siRNA to become a programmable standard of care for a broad spectrum of previously intractable diseases.