Dipicolinic Acid Derivatives as Inhibitors of New Delhi Metallo-β-lactamase‑1

The efficacy of β-lactam antibiotics is threatened by the emergence and global spread of metallo-β-lactamase (MBL) mediated resistance, specifically New Delhi metallo-β-lactamase-1 (NDM-1). By utilization of fragment-based drug discovery (FBDD), a new class of inhibitors for NDM-1 and two related β-lactamases, IMP-1 and VIM-2, was identified. On the basis of 2,6-dipicolinic acid (DPA), several libraries were synthesized for structure–activity relationship (SAR) analysis. Inhibitor 36 (IC50 = 80 nM) was identified to be highly selective for MBLs when compared to other Zn­(II) metalloenzymes. While DPA displayed a propensity to chelate metal ions from NDM-1, 36 formed a stable NDM-1:Zn­(II):inhibitor ternary complex, as demonstrated by 1H NMR, electron paramagnetic resonance (EPR) spectroscopy, equilibrium dialysis, intrinsic tryptophan fluorescence emission, and UV–vis spectroscopy. When coadministered with 36 (at concentrations nontoxic to mammalian cells), the minimum inhibitory concentrations (MICs) of imipenem against clinical isolates of Eschericia coli and Klebsiella pneumoniae harboring NDM-1 were reduced to susceptible levels.