title: Mechanism of action and limited cross-resistance of new lipopeptide MX-2401.
abstract: 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 Ca²⁺-dependent lipopeptide antibiotics, the latter has a different mechanism of action. Specifically, MX-2401 inhibits peptidoglycan synthesis by binding to the substrate undecaprenylphosphate (C₅₅-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 C₅₅-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.
authors.affiliation: BioWest Therapeutics Inc., Suite 400, 1727 West Broadway, Vancouver, British Columbia V6J4W61, Canada.
authors.forename: E
authors.initials: E
authors.lastname: Rubinchik
authors.forename: T
authors.initials: T
authors.lastname: Schneider
authors.forename: M
authors.initials: M
authors.lastname: Elliott
authors.forename: W R P
authors.initials: WR
authors.lastname: Scott
authors.forename: J
authors.initials: J
authors.lastname: Pan
authors.forename: C
authors.initials: C
authors.lastname: Anklin
authors.forename: H
authors.initials: H
authors.lastname: Yang
authors.forename: D
authors.initials: D
authors.lastname: Dugourd
authors.forename: A
authors.initials: A
authors.lastname: Müller
authors.forename: K
authors.initials: K
authors.lastname: Gries
authors.forename: S K
authors.initials: SK
authors.lastname: Straus
authors.forename: H G
authors.initials: HG
authors.lastname: Sahl
authors.forename: R E W
authors.initials: RE
authors.lastname: Hancock
mesh_terms: D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000494:pharmacology*; D002462:Cell Membrane / Q000187:drug effects; D002463:Cell Membrane Permeability / Q000187:drug effects; D017576:Daptomycin / Q000737:chemistry / Q000494:pharmacology; D024881:Drug Resistance, Bacterial; D006801:Humans; D055666:Lipopeptides / Q000737:chemistry / Q000494:pharmacology*; D013210:Staphylococcus / Q000187:drug effects / Q000378:metabolism; D014538:Uridine Diphosphate N-Acetylmuramic Acid / Q000031:analogs & derivatives / Q000096:biosynthesis / Q000378:metabolism
chemical_list: D000900:Anti-Bacterial Agents; D055666:Lipopeptides; C556453:MX-2401; D014538:Uridine Diphosphate N-Acetylmuramic Acid; C069249:muramyl-NAc-(pentapeptide)pyrophosphoryl-undecaprenol; C002225:UDP-N-acetylmuramic acid pentapeptide; D017576:Daptomycin