Synthesis of Hybrid Tripeptide Peptidomimetics Containing Dehydroamino Acid and Aminophosphonic Acid in the Chain and Evaluation of Their Activity toward Cathepsin C

Synthesis of a new group of hybrid phosphonodehydropeptides composed of glycyl-(Z)-dehydrophenylalanine and structurally variable aminophosphonates alongside with investigations of their activity towards cathepsin C are presented. Obtained results suggest that the introduction of (Z)-dehydrophenylalanine residue into the short phosphonopeptide chain does induce the ordered conformation. Investigated peptides appeared to act as weak or moderate inhibitors of cathepsin C.

Phosphonopeptides Revisited, in an Era of Increasing Antimicrobial Resistance

Given the increase in resistance to antibacterial agents, there is an urgent need for the development of new agents with novel modes of action. As an interim solution, it is also prudent to reinvestigate old or abandoned antibacterial compounds to assess their efficacy in the context of widespread resistance to conventional agents. In the 1970s, much work was performed on the development of peptide mimetics, exemplified by the phosphonopeptide, alafosfalin. We investigated the activity of alafosfalin, di-alanyl fosfalin and β-chloro-L-alanyl-β-chloro-L-alanine against 297 bacterial isolates, including carbapenemase-producing Enterobacterales (CPE) (n = 128), methicillin-resistant Staphylococcus aureus (MRSA) (n = 37) and glycopeptide-resistant enterococci (GRE) (n = 43). The interaction of alafosfalin with meropenem was also examined against 20 isolates of CPE. The MIC₅₀ and MIC₉₀ of alafosfalin for CPE were 1 mg/L and 4 mg/L, respectively and alafosfalin acted synergistically when combined with meropenem against 16 of 20 isolates of CPE. Di-alanyl fosfalin showed potent activity against glycopeptide-resistant isolates of Enterococcus faecalis (MIC₉₀; 0.5 mg/L) and Enterococcus faecium (MIC₉₀; 2 mg/L). Alafosfalin was only moderately active against MRSA (MIC₉₀; 8 mg/L), whereas β-chloro-L-alanyl-β-chloro-L-alanine was slightly more active (MIC₉₀; 4 mg/L). This study shows that phosphonopeptides, including alafosfalin, may have a therapeutic role to play in an era of increasing antibacterial resistance.