Conjugation Approaches for Peptide-Mediated Delivery of Oligonucleotides Therapeutics

Nitin A Patil

doi:10.1071/ch21131

Abstract

Oligonucleotide-based agents are versatile biomolecules that modulate gene expression. The last decade has seen the emergence of oligonucleotide-based tools for biochemical investigations. Importantly, several oligonucleotide-based drugs and vaccines are currently used for various therapeutic applications ranging from anti-inflammatory and anti-viral agents to those used in cardiovascular, ophthalmic, and neuro-muscular disorders. Despite a broad range of applications, achieving efficient oligonucleotide delivery remains a major limitation. A possible solution is to conjugate cell-penetrating peptides with oligonucleotides. This review provides an overview of chemical strategies used to synthesise peptide–oligonucleotide conjugates. The merits and liabilities of these strategies are discussed in the context of synthetic efficiency, and bio-reversible and -irreversible linkages.

Highlights

Oligonucleotides are typically short oligomers (12–24 monomers) of natural or chemically modified nucleotide analogues that bind and modulate the function of their cognate mRNA or DNA sequence to produce a desired pharmacological effect.[1]
While chemical efficiency is an important aspect of peptide– oligonucleotide conjugation, the site of release and stability to enzymatic degradation must be considered when determining an appropriate linkage strategy
Whereas the amide linkage approach provides significant enzymatic stability, it often results in low yields and is limited to small peptides (,15 amino acids)

Summary

Introduction

Oligonucleotides are typically short oligomers (12–24 monomers) of natural or chemically modified nucleotide analogues that bind and modulate the function of their cognate mRNA or DNA sequence to produce a desired pharmacological effect.[1]. Formation of an amide bond when using a protected peptide presents several challenges.[41] An alternative approach involves the conjugation of unprotected peptides to oligonucleotides using native chemical ligation (NCL).[42,43,44,45,46,47,48,49] NCL utilises a chemoselective S–N acyl transfer to form an amide linkage.[50] Initially, an unprotected peptide with an activated C-terminal thioester forms a trans-thioester with the N-terminal thiol of the ligating oligonucleotide.[41] The free N-terminal amine attacks the carbonyl group of the trans-thioester intermediate to form an amide bond Given this elegant strategy is selective for the N-terminal thiol and employs an unprotected peptide in aqueous buffers, it provides significant advantages over protected peptide conjugation.

H N O HS

H S 2c -O-MOE-oligonucleotides

Conclusion and Outlook