4'-O-methoxyethyl-2'-deoxy-uridine and cytidine ribonucleotides improve duplex stability, nuclease resistance, and elicit efficient knockdown of Bcl-2 expression.

In this study, we report the synthesis of 4'-O-methoxyethyl deoxyuridine and 4'-O-methoxyethyl deoxycytidine phosphoramidites and their incorporation into oligonucleotides. The 3'-exonuclease experiment indicated a significant increase in stability with the incorporation of 4'-O-MOE dU alone (T = 178 min) and in combination with phosphorothioate modification (T = 13 h) in dT-mer. Western blot studies demonstrated that 4'-O-MOE-dU and 4'-O-MOE-dC modifications were well-tolerated when placed at both overhang regions and multiple positions within the passenger strand of anti-Bcl2 siRNAs.

4'--Cholesterol/Pyridyl-2'--Methyl Uridine-Functionalized siRNA Enhances Stability and Carrier-Free Gene Silencing.

Chemical modifications and targeted delivery through the conjugation of small molecules have transformed the potential of siRNA-based therapeutics. These advancements address key challenges, such as poor cellular uptake, low bioavailability, and limited metabolic stability, making siRNA delivery more efficient and clinically viable. Cholesterol-conjugated siRNA enables cellular uptake through lipoprotein pathways without transfection agents.

4'--Acetamidomethyl-2'--methoxyethyl Nucleic Acid Modifications Improve Thermal Stability, Nuclease Resistance, Potency, and hAgo2 Binding of Small Interfering RNAs.

In this study, we designed the 4'--acetamidomethyl-2'--methoxyethyl (4'--ACM-2'--MOE) uridine and thymidine modifications, aiming to test them into small interfering RNAs. Thermal melting studies revealed that incorporating a single 4'--ACM-2'--MOE modification in the DNA duplex reduced thermal stability. In contrast, an increase in thermal stability was observed when the modification was introduced in DNA:RNA hybrid and in siRNAs.

Advances in siRNA therapeutics and synergistic effect on siRNA activity using emerging dual ribose modifications.

Nucleic acid-based therapeutics that control gene expression have been steadily progressing towards achieving their full clinical potential throughout the last few decades. Rapid progress has been achieved in RNAi-based therapy by optimizing high specificity and gene silencing efficiency using chemically modified siRNAs. Since 2018, four siRNA drugs - patisiran, givosiran, lumasiran, and inclisiran, were approved by the US FDA, providing a testament to the promise of RNAi therapeutics.

Folate Receptor-Mediated siRNA Delivery: Recent Developments and Future Directions for RNAi Therapeutics.

RNA interference (RNAi), a gene regulatory process mediated by small interfering RNAs (siRNAs), has made remarkable progress as a potential therapeutic agent against various diseases. However, RNAi is associated with fundamental challenges such as poor systemic delivery and susceptibility to the nucleases. Targeting ligand-bound delivery vehicles has improved the accumulation of drug at the target site, which has resulted in high transfection efficiency and enhanced gene silencing.