Bridging Peptides with RNA

Native chemical ligation (NCL) is a remarkable technique widely utilized by peptide chemists to construct large, and increasingly complex peptides and miniature proteins, such as insulin, by fusing two medium-sized peptides. Developed at Scripps Research (USA) just 30 years ago, it is still the leading method for biomolecular conjugation, owing to its simplicity, robustness, and biocompatibility during chemical synthesis. Another key feature of NCL is its use of the amino acid cysteine to carry out the ligation, leading to the incorporation of a cysteine at the site of ligation—the spot where the two ends of each peptide meet. This feature allows chemists to decorate large macromolecules by installing unique carbohydrates, lipids, nucleic acids, and other molecular appendages, or perform chemical modifications to transform the cysteine residue.  

 The utility of NCL in crafting therapeutically relevant molecules was recently exemplified by our CIPPS Chief Investigator Professor Lara Malins and research fellow Dr Dan Engelhardt from ANU along with their collaborators at AstraZeneca, Dr Laurent Knerr and Dr Peter Nordberg, who used the technique to develop clinically significant antisense oligonucleotide (ASO) therapies. ASO therapies are gene therapies that use short (and synthetic) RNA or DNA molecules to selectively bind complementary nucleic acid sequences, thereby altering the associated biological functions of the targeted nucleic acids. They are being explored as RNA-based therapeutics to treat cancer and genetic disorders. However, current ASO therapies face challenges that prevent these drugs from maximising beneficial outcomes. For example, the drug might be weakly absorbed into the blood, poorly distributed throughout the body, or rapidly degraded and excreted. By harnessing the flexibility of the NCL methodology, our centre researchers have demonstrated that connecting ASOs with a peptide, lipid, or carbohydrate appendage can help improve their poor pharmacokinetic properties (i.e. absorption, distribution, metabolism), thus overcoming the barriers of traditional ASO therapies.  

 The work presented by CI Lara Malins and Dr Dan Engelhardt highlights the centre’s goal of fostering meaningful collaborations between academia and the pharmaceutical industry, with the aim of transforming ideas into real-world innovations enabling the development of effective tools for medicine and next-generation therapeutic agents. 

 Citation: Engelhardt, D., Nordberg, P., Knerr, L., & Malins, L. R. (2024). Accessing Therapeutically-Relevant Multifunctional Antisense Oligonucleotide Conjugates Using Native Chemical Ligation. Angew Chem Int Ed Engl, 63(49), e202409440. https://doi.org/10.1002/anie.202409440  

 Doi: 10.1002/anie.202409440  

 CIPPS contributors: Lara Malins, Dan Engelhardt, Laurent Knerr (AstraZeneca), Peter Nordberg (AstraZeneca).