Mechanism of action and limited cross-resistance of new lipopeptide MX-2401

E. Rubinchik, T. Schneider, M. Elliott, W. R.P. Scott, J. Pan, C. Anklin, H. Yang, D. Dugourd, A. Müller, K. Gries, S. K. Straus, H. G. Sahl, R. E.W. Hancock

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MX-2401 is a semisynthetic calcium-dependent lipopeptide antibiotic (analogue of amphomycin) in preclinical development for the treatment of serious Gram-positive infections. In vitro and in vivo, MX-2401 demonstrates broad-spectrum bactericidal activity against Gram-positive organisms, including antibiotic-resistant strains. The objective of this study was to investigate the mechanism of action of MX-2401 and compare it with that of the lipopeptide daptomycin. The results indicated that although both daptomycin and MX-2401 are in the structural class of Ca 2+-dependent lipopeptide antibiotics, the latter has a different mechanism of action. Specifically, MX-2401 inhibits peptidoglycan synthesis by binding to the substrate undecaprenylphosphate (C 55-P), the universal carbohydrate carrier involved in several biosynthetic pathways. This interaction resulted in inhibition, in a dose-dependent manner, of the biosynthesis of the cell wall precursors lipids I and II and the wall teichoic acid precursor lipid III, while daptomycin had no significant effect on these processes. MX-2401 induced very slow membrane depolarization that was observed only at high concentrations. Unlike daptomycin, membrane depolarization by MX-2401 did not correlate with its bactericidal activity and did not affect general membrane permeability. In contrast to daptomycin, MX-2401 had no effect on lipid flip-flop, calcein release, or membrane fusion with 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC)/1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-(1′-rac-glycerol) (sodium salt) (POPG) liposomes. MX-2401 adopts a more defined structure than daptomycin, presumably to facilitate interaction with C 55-P. Mutants resistant to MX-2401 demonstrated low cross-resistance to other antibiotics. Overall, these results provided strong evidence that the mode of action of MX-2401 is unique and different from that of any of the approved antibiotics, including daptomycin.

Original languageEnglish
Pages (from-to)2743-2754
Number of pages12
JournalAntimicrobial Agents and Chemotherapy
Issue number6
Publication statusPublished - 1 Jun 2011
Externally publishedYes

ASJC Scopus subject areas

  • Pharmacology
  • Pharmacology (medical)
  • Infectious Diseases

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