A series of 36 linear and cyclic beta- and gamma-peptides consisting of as few as two, and as many as 15 residues, was offered as substrates to 15 commercially available proteases of bacterial, fungal, and eukaryotic origin, including a beta-lactamase and amidases, as well as most vigorous, nonspecific proteases, such as the 20S proteasome from human erythrocytes. For comparison, an alpha-eicosapeptide and standard substrates of the proteolytic enzymes were included in the investigation. Under conditions of complete cleavage of the alpha-peptide within 15 min the beta- and gamma-peptides were stable for at least 48 h. Inhibition studies with seven beta- and gamma-peptides and alpha-chymotrypsin show that the residual enzyme activity toward succinyl-Ala-Ala-Pro-Phe-p-nitroanilide is unchanged within experimental error after incubation for 15 min with the peptide analogues. Thus, beta- and gamma-peptides with proteinogenic side chains, that is, consisting of the singly or doubly homologated natural alpha-amino acids (one or two CH(2) groups inserted in the backbone of each residue), are completely stable to common proteases, without inhibiting their normal activity (as demonstrated for alpha-chymotrypsin). This proteolytic stability of peptides built of homologated amino acids is a prerequisite for their potential use as drugs.
β-lactams are the most prescribed class of antibiotics
due
to their potent, broad-spectrum antimicrobial activities. However,
alarming rates of antimicrobial resistance now threaten the clinical
relevance of these drugs, especially for the carbapenem-resistant Enterobacterales expressing metallo-β-lactamases
(MBLs). Antimicrobial agents that specifically target these enzymes
to restore the efficacy of last resort β-lactam drugs, that
is, carbapenems, are therefore desperately needed. Herein, we present
a cyclic zinc chelator covalently attached to a β-lactam scaffold
(cephalosporin), that is, BP1. Observations from in vitro assays (with
seven MBL expressing bacteria from different geographies) have indicated
that BP1 restored the efficacy of meropenem to ≤ 0.5 mg/L,
with sterilizing activity occurring from 8 h postinoculation. Furthermore,
BP1 was nontoxic against human hepatocarcinoma cells (IC50 > 1000 mg/L) and exhibited a potency of (K
iapp) 24.8 and 97.4 μM against Verona integron-encoded
MBL (VIM-2) and New Delhi metallo β-lactamase (NDM-1), respectively.
There was no inhibition observed from BP1 with the human zinc-containing
enzyme glyoxylase II up to 500 μM. Preliminary molecular docking
of BP1 with NDM-1 and VIM-2 sheds light on BP1’s mode of action.
In Klebsiella pneumoniae NDM infected
mice, BP1 coadministered with meropenem was efficacious in reducing
the bacterial load by >3 log10 units’ postinfection.
The findings herein propose a favorable therapeutic combination strategy
that restores the activity of the carbapenem antibiotic class and
complements the few MBL inhibitors under development, with the ultimate
goal of curbing antimicrobial resistance.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.