Abstract
ABSTRACTPeptide antibiotics are an abundant and synthetically tractable source of molecular diversity, but they are often cationic and can be cytotoxic, nephrotoxic and/or ototoxic, which has limited their clinical development. Here we report structure-guided optimization of an amphipathic peptide, arenicin-3, originally isolated from the marine lugworm Arenicola marina. The peptide induces bacterial membrane permeability and ATP release, with serial passaging resulting in a mutation in mlaC, a phospholipid transport gene. Structure-based design led to AA139, an antibiotic with broad-spectrum in vitro activity against multidrug-resistant and extensively drug-resistant bacteria, including ESBL, carbapenem- and colistin-resistant clinical isolates. The antibiotic induces a 3–4 log reduction in bacterial burden in mouse models of peritonitis, pneumonia and urinary tract infection. Cytotoxicity and haemolysis of the progenitor peptide is ameliorated with AA139, and the ‘no observable adverse effect level’ (NOAEL) dose in mice is ~10-fold greater than the dose generally required for efficacy in the infection models.
Highlights
Peptide antibiotics are an abundant and synthetically tractable source of molecular diversity, but they are often cationic and can be cytotoxic, nephrotoxic and/or ototoxic, which has limited their clinical development
We show that structure-based design can be applied to antimicrobial peptides to minimize basicity while retaining membrane translocation properties, successfully generating a broad-spectrum antibiotic with efficacy in murine models of Gram-negative bacterial infection, accompanied by ameliorated toxicity and hemolysis compared to the progenitor
The pattern of nuclear Overhauser effect interactions, variation from random coil values of the secondary chemical shift of carbon and hydrogen atoms (Fig. 1c), and the chemical shift indices (Supplementary Table 1) suggested the peptide adopted a slightly twisted β-hairpin configuration, with 4 hydrogen bonds evenly spaced further stabilizing the β-sheet pinned by the disulfide bonds (Fig. 1, Supplementary Table 2)
Summary
Peptide antibiotics are an abundant and synthetically tractable source of molecular diversity, but they are often cationic and can be cytotoxic, nephrotoxic and/or ototoxic, which has limited their clinical development. Directly targeting and disrupting the bacterial membrane can potentially circumvent many of these resistance mechanisms, today only one class of such membrane-targeting antibiotics has been approved for treatment of drug-resistant Gram-negative infections: the structurally related lipopeptides colistin (polymyxin E) and polymyxin B These have a very narrow therapeutic index, with nephrotoxicity and other adverse off-target effects seen in humans even at the minimum doses needed to achieve efficacy[3,4]. Arenicin-3 is a more recently identified member of the arenicin family that contains two disulfide bonds forming a 21-residue amphipathic β-hairpin[17] It exhibits potent and rapid antimicrobial activity in vitro against various MDR and extensively drug-resistant (XDR) pathogenic Gram-negative bacteria (minimum inhibitory concentration [MIC] of 1 μg mL−1 against Escherichia coli), but it is cytotoxic and induces hemolysis of human erythrocytes. We show that structure-based design can be applied to antimicrobial peptides to minimize basicity while retaining membrane translocation properties, successfully generating a broad-spectrum antibiotic with efficacy in murine models of Gram-negative bacterial infection, accompanied by ameliorated toxicity and hemolysis compared to the progenitor
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