Antisense Oligonucleotides (ASOs) are single-stranded DNA or RNA sequences, consisting of 15-25 nucleotides, that can be paired with a target gene to achieve gene regulation by specifically blocking the transcription or translation process of the target gene. The ASO field is an emerging area of drug development that provides treatment plans for targeting disease sources at the RNA level. With the advantages of high specificity, high efficiency, and low toxicity, antisense oligonucleotide drugs are widely used in genetic function research, drug target verification, and tumor therapy.

Chemical Modification of ASOs
When unmodified ASOs are used to target RNA, they are highly susceptible to nuclease degradation due to the presence of phosphodiester bonds. Therefore, chemical modification of ASOs can improve enzyme stability, reduce immune response and off-target toxicity, facilitate drug delivery to specific organs and cells, and enhance their expression said cells. Chemical modifications of antisense oligonucleotides are mainly divided into three main categories: backbone modifications, ribose modifications at the 2’ position, and binding of ligands to ASOs.

ASO Mechanisms of Action
The chemical properties of antisense oligonucleotides, the location of binding RNA, and the function of target RNA all affect the regulation of RNA by ASOs. Currently, the regulatory mechanisms of ASOs on RNA are divided into two main categories: RNA degradation mechanisms and occupancy mechanisms.

RNA Degradation Mechanism: In most cases, ASOs can promote RNA shearing by RNaseH1 or Argonaute2 (Ago2). RNaseH1 is an endogenous nuclease present in most cells that promotes the cleavage of RNA in RNA-DNA double-stranded hybrids.
Occupancy Mechanism: In most mammals, the translation of pre-mRNA into protein requires steps such as adding a cap at the 5 position, adding a tail at the 3 position, and intron splicing, etc. ASOs can act at each step of this process to regulate RNA, which in turn affects protein expression. In some antisense mechanisms, ASOs can obstruct or enhance the translation of proteins by binding to different positions of RNA.

ASO Delivery Method
Oligonucleotide drugs are generally injected subcutaneously or intravenously, but only a small fraction of them can eventually reach the tissue cytoplasm or nucleus. Degradation of extracellular RNase, phagocytosis by endothelial tissue, filtration by the kidney, and receptor-mediated endocytosis all affect the delivery efficiency of ASOs.
Chemical modification of ASOs, GaINAc coupling, CPPs (cell-penetrating peptides) coupling, and cholesterol coupling are conventional strategies that improve enzyme stability, reduce immune response and off-target toxicity, and facilitate drug delivery to specific organs and cells.

Synbio Technologies assists ASO Drug Research & Development
At Synbio Technologies, we are committed to providing our customers with the highest quality ASO chemical synthesis platform available. We have a superb synthesis and purification processes that meets ISO9001 & ISO13485 quality management requirements, ensuring that all of our products meet the highest standards. We offer a variety of ASO modification types, as well as customized oligonucleotide conjugates, to aid nucleic acid drug research and development. Our experienced team is always available to provide expert advice and guidance, ensuring that you get the most out of our products and services. Contact us today to learn more about how we can help you achieve your goals.

References

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3. Erdos MR, Cabral WA, Tavarez UL, et al. A targeted antisense therapeutic approach for Hutchinson-Gilford progeria syndrome. Nat Med. 2021 Mar; 27(3):536-545.
4. Tanowitz M, Hettrick L, Revenko A, et al. Asialoglycoprotein Receptor 1 Mediates Productive Uptake of N-acetylgalactosamine-conjugated and Unconjugated Phosphorothioate Antisense Oligonucleotides into Liver Hepatocytes. Nucleic Acids Res. 2017 Dec 1; 45(21):12388-12400.
5. Bennett CF. Therapeutic Antisense Oligonucleotides Are Coming of Age. Annu Rev Med. 2019 Jan 27; 70: 307-321.