Antimicrobial peptides (AMPs) are a potential alternative to classical antibiotics that are yet to achieve a therapeutic breakthrough for treatment of systemic infections. The antibacterial potency of pleurocidin, an AMP from Winter Flounder, is linked to its ability to cross bacterial plasma membranes and seek intracellular targets while also causing membrane damage. Here we describe modification strategies that generate pleurocidin analogues with substantially improved, broad spectrum, antibacterial properties, which are effective in murine models of bacterial lung infection. Increasing peptide–lipid intermolecular hydrogen bonding capabilities enhances conformational flexibility, associated with membrane translocation, but also membrane damage and potency, most notably against Gram-positive bacteria. This negates their ability to metabolically adapt to the AMP threat. An analogue comprising d-amino acids was well tolerated at an intravenous dose of 15 mg/kg and similarly effective as vancomycin in reducing EMRSA-15 lung CFU. This highlights the therapeutic potential of systemically delivered, bactericidal AMPs.
Bibliographical noteFunding Information:
NMR experiments described in this paper were carried out using the facilities of the Centre for Biomolecular Spectroscopy, King’s College London, and at the MRC Biomedical NMR Centre at the Francis Crick Institute. The King’s instruments were acquired with a Multi-user Equipment Grant from the Wellcome Trust and an Infrastructure Grant from the British Heart Foundation. The MRC Biomedical NMR Centre is supported by the Francis Crick Institute, which receives its core funding from Cancer Research UK (FC001029), the UK Medical Research Council (FC001029), and the Wellcome Trust (FC001029). We thank Dr Tom Frenkiel and Dr Alain Oregioni for their assistance with HR-MAS NMR experiments performed at the Francis Crick Institute. This work used the ARCHER UK National Supercomputing Service (http://www.archer. ac.uk). C.D.L. acknowledges the stimulating research environment provided by the EPSRC Centre for Doctoral Training in Cross-Disciplinary Approaches to NonEquilibrium Systems (CANES, EP/L015854/1). PMF was supported by a Health Schools Studentship funded by the EPSRC (EP/M50788X/1). AJM and GM received funding from the MRC Proximity to Discovery: Industry Engagement Fund (MC_PC_16074) and the King’s Health Partners R&D Challenge rapid fund. AJM and CL received funding from a NC3Rs Skills & Knowledge Transfer grant (NC/T001240/1). CH and MC were supported by funding from PHE Pipeline fund and latterly by PHE Grant in Aid project 109505. This work utilised NIAID’s suite of pre-clinical services for maximum tolerated dose (MTD) assessment (Contract no. HHSN272201700020I/75N93019F00131) conducted by Pharmacology Discovery Services Taiwan.
Commissioned by the Wellcome Trust, a pipeline portfolio review of alternatives to antibiotics recommends “strong support for funding while monitoring for breakthrough insights regarding systemic therapy” for a tier of approaches that include AMPs2. The review presents the prevailing wisdom that AMPs are unsuited for systemic administration as they are poorly tolerated in animal models and susceptible to degradation. This substantially limits the scope of infection settings that are tractable to AMPs and hence their future development. There is an urgent need therefore to identify AMPs that are sufficiently potent against antibiotic resistant bacteria and well tolerated in vivo such that they are effective when delivered intravenously.
© 2020, The Author(s).