Mechanism of Action
Lipid II Binding
Plectasin binds the pyrophosphate and sugar moieties of Lipid II, the essential lipid-linked bacterial cell wall building block, with 1:1 stoichiometry and high affinity. This blocks the transglycosylase and transpeptidase steps of peptidoglycan assembly. Unlike vancomycin which binds the terminal D-Ala-D-Ala dipeptide of Lipid II, plectasin contacts different portions of the molecule, explaining retained activity against some vancomycin-resistant VanA strains that modify D-Ala-D-Lac.
Selective Gram-Positive Activity
Plectasin is active exclusively against Gram-positive bacteria. The outer membrane of Gram-negative bacteria prevents plectasin access to the periplasmic Lipid II. This selectivity covers clinically important pathogens including S. pneumoniae, S. aureus (including MRSA), and Enterococcus species. The Gram-positive selective mechanism avoids disruption of Gram-negative gut flora.
Research Summary
Anti-Pneumococcal Activity
PreclinicalPlectasin shows potent activity against penicillin-resistant and multidrug-resistant Streptococcus pneumoniae strains with MIC values of 0.5-4 ug/mL. In mouse pneumonia models, plectasin outperforms vancomycin and penicillin in bacterial clearance at equivalent doses. The unique Lipid II binding mode suggests no cross-resistance with existing beta-lactam or glycopeptide antibiotics.
NZ2114 and Analog Development
PreclinicalNZ2114, an optimized plectasin analog with improved stability and potency, is active against MRSA in mouse thigh infection models at doses comparable to clinical antibiotics. Novozymes and Novo Nordisk collaborated on plectasin development. Despite promising preclinical data, no plectasin analog has advanced to clinical trials, partly due to manufacturing cost and stability challenges for systemic use.
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Research Protocols
| Goal | Dose | Frequency | Route |
|---|---|---|---|
| Anti-pneumococcal (in vitro) | 0.5-4 ug/mL MIC | Single exposure | Direct application |
| Mouse pneumonia model | 10-40 mg/kg | Twice daily | SC / IP (research) |
No human protocols. Preclinical data supports clinical development but no IND filed.
Interactions
Safety Profile
Plectasin shows low hemolytic activity and minimal cytotoxicity to mammalian cells in preclinical studies. Kidney and liver safety profiles are acceptable in acute animal studies. As a fungal-origin peptide, immunogenicity profile for chronic use is unknown. No human clinical data.
References
- [1]Mygind PH, et al. (2005). Plectasin is a peptide antibiotic with therapeutic potential from a saprophytic fungus. Nature, 437(7061), 975-980.
- [2]Schneider T, et al. (2010). Plectasin, a fungal defensin, targets the bacterial cell wall precursor Lipid II. Science, 328(5982), 1168-1172.