PEGylated Oligothioetheramide Prodrugs Activated by Host Serum Proteases

Due to the increasing prominence of antibiotic resistance, novel drug discovery and delivery approaches targeting bacteria are essential. In this work we evaluate a prodrug design to improve the cytotoxic profile of polycationic oligothioetheramides (oligoTEAs), which are promising antimicrobials. Herein we chemically modify the oligoTEA, PDT‐4G, with a polyethylene glycol (PEG) and show that 1, 2, and 5 kDa PEGs mitigate cytotoxicity. As PEGylation reduces antibacterial activity, we evaluate two peptide linkers which, unlike oligoTEAs, are susceptible to proteolytic cleavage in serum. To gain insight into the prodrug reactivation, two linkers were tested, the 5‐residue peptide sequence LMPTG, and the dipeptide sequence VC‐PABC. In the presence of 20 % serum, prodrugs made with the VC‐PABC linker successfully inhibited bacterial growth. Overall, we observed reactivation of oligoTEAs facilitated by serum protease cleavage of the peptide linkers. This work opens the door to the future design of antimicrobial prodrugs with tunable release profiles. High host toxicity presents a challenging barrier to clinical application of small‐molecule antibiotics. PEG conjugation incorporating a reactivation mechanism triggered by host proteases effectively reduces toxicity through controlled release of the antibiotic. While highlighting the utility of synthetic, proteolytically stable compounds like oligoTEAs, this approach is translatable to similar therapeutics.