Optimization of 1,2,4-Triazole-3-thiones toward Broad-Spectrum Metallo-β-lactamase Inhibitors Showing Potent Synergistic Activity on VIM- and NDM-1-Producing Clinical Isolates

Metallo-β-lactamases
(MBLs) contribute to the resistance
of Gram-negative bacteria to carbapenems, last-resort antibiotics
at hospital, and MBL inhibitors are urgently needed to preserve these
important antibacterial drugs. Here, we describe a series of 1,2,4-triazole-3-thione-based
inhibitors displaying an α-amino acid substituent, which amine
was mono- or disubstituted by (hetero)aryl groups. Compounds disubstituted
by certain nitrogen-containing heterocycles showed submicromolar activities
against VIM-type enzymes and strong NDM-1 inhibition (Ki = 10–30 nM). Equilibrium dialysis, native mass
spectrometry, isothermal calorimetry (ITC), and X-ray crystallography
showed that the compounds inhibited both VIM-2 and NDM-1 at least
partially by stripping the catalytic zinc ions. These inhibitors also
displayed a very potent synergistic activity with meropenem (16- to
1000-fold minimum inhibitory concentration (MIC) reduction) against
VIM-type- and NDM-1-producing ultraresistant clinical isolates, including Enterobacterales and Pseudomonas aeruginosa. Furthermore, selected compounds exhibited no or moderate toxicity
toward HeLa cells, favorable absorption, distribution, metabolism,
excretion (ADME) properties, and no or modest inhibition of several
mammalian metalloenzymes.