Facile Siderophore Assembly Enables Bacterial Delivery of Nucleic Acid Therapeutics

Antibiotic resistance is an increasing threat to modern medicine that calls for the discovery of new antibiotics. RNA targeting is a promising approach for antibiotic development. In particular, antisense antibiotics, dubbed ASObiotics, are an exciting class of oligomers that show promise as powerful antibiotic agents. However, limited bacterial uptake has hampered their widespread use. Exploiting bacteria's own machinery in transporting cargo into the cell through siderophore-mediated delivery can address this obstacle. Here, we report the design of a tris-catechol-type siderophore that allows for the assembly on the backbone of antisense therapeutics during their solid-phase peptide synthesis. This approach fully negates the need for challenging siderophore synthesis and conjugation to the antisense therapeutic. The resulting ASObiotics display potent submicromolar activity against Escherichia coli. Through a series of competition and knockout experiments, we elucidated that ASObiotic delivery is accomplished through the Fiu receptor. On-target engagement was established through RT-qPCR, lacZ reporter assays, and Western blot. We further demonstrate the potential use of these siderophore-antisense conjugates as antibiotics against Bacillus subtilis and Acinetobacter baumannii.