Background: There is an urgent need to develop novel inhibitors against clinically
widespread extended-spectrum β-lactamases (ESBLs) to meet the challenges of the ever-evolving
threat of antibiotic resistances. Most existing ESBL inhibitors sharing a common chemical feature
of β-lactam ring in their molecule, this structural characteristic makes them intrinsically susceptible
to enzymatic breakdown by the resistance mechanisms employed by the bacteria.
Objective: The aim of this study was to screen and discover novel lead compounds by using Lproline
as initial scaffold to create a “non-sulfur, non-β-lactam” new chemotypes for potential
Methods: Structure-based molecular docking and virtual screening were employed in the novel
inhibitor generation process for lead compound screening and SAR analysis. Evaluation of the
ESBL inhibitory activity of the lead compounds was performed in combination with three of the
most susceptible antibiotics: ceftazidime, meropenem and ampicillin, against thirteen ESBL enzymes
including four new CTX-M harboring strains and four KPC-2 producing species.
Results: L-proline derived (S)-1-(2-sulfamoylbenzoyl)pyrrolidine-2-carboxylic acid (compound
6) as a “non-sulfur, non-β-lactam” and the most potential ESBL inhibitor was identified. Compound
6 possesses ideal anti-resistance activities by reducing MICs of ceftazidime, meropenem
and ampicillin by 16-133, 32-133 and 67-267 fold respectiveily. The inhibitory mechanism of 6
with CTX-M, KPC-2 and penicillinase were proposed and probed with molecular docking analysis.
Conclusion: Given that the simple proline derivative but promising synergistic antibacterial
properties of compound 6 augers well for further investigations into its in vivo efficacy.