Publicação
Ddevelopment of next-generation polymyxins targeting problematic gram-negative biofilm infections
| Resumo: | Antimicrobial resistance is a major global health threat, with which the antibiotic discovery pipeline is not keeping up. Polymyxins (PM) B and E have resurrected as last-resort drugs (given their toxicity) against Gram-negative bacterial infections, but PM resistance has already been reported, resulting in the lack of effective therapies. Taking advantage of these valuable scaffolds, we set out to design new PM analogs with high antimicrobial activity and low toxicity. ,-Dialkylglycines (DAG) are unnatural amino acids with unique characteristics (bioactivity, metabolic resistance, hydrophobicity, stability), making them innovative building blocks in PM analog design. We report the synthesis of 6 new PM analogs and their antimicrobial and antibiofilm activity, including in combination with common antibiotics. The Ugi multicomponent reaction was applied to the synthesis of 2 DAGs, diisobutyl glycine (Dibg) and dibenzyl glycine (Dbng), which were assembled in situ at positions 6 and/or 7 of native PMB/E (Figure1) through a microwave assisted solid-phase peptide synthesis. The anti-bacterial and anti-biofilm activities were assessed against 24-hold cultures of Pseudomonas aeruginosa ATCC 27853 and assessed by broth microdilution and by counting the culturable biofilm cells, respectively. The synergy between PM and two common antibiotics - ciprofloxacin (CIP) and tobramycin (TOB) - was evaluated through checkerboard assays and anti-biofilm activity of the PM-antibiotic combinations by CFU counting. The cytotoxicity was evaluated in lung epithelial cells (A459) by the MTS viability assay. Analogs PMBa and PMEa (Dibg @ position 7) were the most promising, with PMBa exhibiting MIC/MBC=4 mg/L and no toxicity (A549 lung epithelial cells). Preliminary HPLC analysis indicates ~66% purity, meaning pure analog concentrations ~2 mg/L, close to that of PMB (1 mg/L). Furthermore, the PMBa analog at 512 mg/L (~340 mg/L pure analog) decreased biofilm ~3.7 log(CFU/mL), which is promising considering that PMB achieved a similar reduction, ~3.9 log(CFU/mL), for the concentration range 128-512 mg/L. In turn, analogs PMBb and PMEb (Dbng @ position 6) and PMBc (Dbng @ position 6 + Dibg @ position7) achieved synergic/additive outcomes (FICI between 0.3125 and 0.75) combined with TOB/CIP, despite biofilm eradication assays showing indifferent outcomes. We developed 6 PM analogs, 5 exhibiting anti-pseudomonal activity, including in combination scenarios, revealing DAGs suitability for PM analog design. |
|---|---|
| Autores principais: | Graínha, Tânia Raquel Rodrigues |
| Outros Autores: | Martins, Elsa; Costa, Susana P.; Jorge, Paula; Lopes, Susana Patrícia |
| Ano: | 2024 |
| País: | Portugal |
| Tipo de documento: | póster em conferência |
| Tipo de acesso: | acesso restrito |
| Instituição associada: | Universidade do Minho |
| Idioma: | inglês |
| Origem: | RepositóriUM - Universidade do Minho |
| Resumo: | Antimicrobial resistance is a major global health threat, with which the antibiotic discovery pipeline is not keeping up. Polymyxins (PM) B and E have resurrected as last-resort drugs (given their toxicity) against Gram-negative bacterial infections, but PM resistance has already been reported, resulting in the lack of effective therapies. Taking advantage of these valuable scaffolds, we set out to design new PM analogs with high antimicrobial activity and low toxicity. ,-Dialkylglycines (DAG) are unnatural amino acids with unique characteristics (bioactivity, metabolic resistance, hydrophobicity, stability), making them innovative building blocks in PM analog design. We report the synthesis of 6 new PM analogs and their antimicrobial and antibiofilm activity, including in combination with common antibiotics. The Ugi multicomponent reaction was applied to the synthesis of 2 DAGs, diisobutyl glycine (Dibg) and dibenzyl glycine (Dbng), which were assembled in situ at positions 6 and/or 7 of native PMB/E (Figure1) through a microwave assisted solid-phase peptide synthesis. The anti-bacterial and anti-biofilm activities were assessed against 24-hold cultures of Pseudomonas aeruginosa ATCC 27853 and assessed by broth microdilution and by counting the culturable biofilm cells, respectively. The synergy between PM and two common antibiotics - ciprofloxacin (CIP) and tobramycin (TOB) - was evaluated through checkerboard assays and anti-biofilm activity of the PM-antibiotic combinations by CFU counting. The cytotoxicity was evaluated in lung epithelial cells (A459) by the MTS viability assay. Analogs PMBa and PMEa (Dibg @ position 7) were the most promising, with PMBa exhibiting MIC/MBC=4 mg/L and no toxicity (A549 lung epithelial cells). Preliminary HPLC analysis indicates ~66% purity, meaning pure analog concentrations ~2 mg/L, close to that of PMB (1 mg/L). Furthermore, the PMBa analog at 512 mg/L (~340 mg/L pure analog) decreased biofilm ~3.7 log(CFU/mL), which is promising considering that PMB achieved a similar reduction, ~3.9 log(CFU/mL), for the concentration range 128-512 mg/L. In turn, analogs PMBb and PMEb (Dbng @ position 6) and PMBc (Dbng @ position 6 + Dibg @ position7) achieved synergic/additive outcomes (FICI between 0.3125 and 0.75) combined with TOB/CIP, despite biofilm eradication assays showing indifferent outcomes. We developed 6 PM analogs, 5 exhibiting anti-pseudomonal activity, including in combination scenarios, revealing DAGs suitability for PM analog design. |
|---|