Carbapenem-resistant Gram-negative pathogens are a critical public health threat and there is an urgent need for new treatments. Carbapenemases (β-lactamases able to inactivate carbapenems) have been identified in both serine β-lactamase (SBL) and metallo-β-lactamase (MBL) families. The recent introduction of SBL carbapenemase inhibitors has provided alternative therapeutic options. Unfortunately, there are no approved inhibitors of MBL-mediated carbapenem-resistance and treatment options for infections caused by MBL-producing Gram-negatives are limited. Here, we present ZN148, a zinc-chelating MBL-inhibitor capable of restoring the bactericidal effect of meropenem and in vitro clinical susceptibility to carbapenems in >98% of a large international collection of MBL-producing clinical Enterobacterales strains (n = 234). Moreover, ZN148 was able to potentiate the effect of meropenem against NDM-1-producing Klebsiella pneumoniae in a murine neutropenic peritonitis model. ZN148 showed no inhibition of the human zinc-containing enzyme glyoxylase II at 500 μM, and no acute toxicity was observed in an in vivo mouse model with cumulative dosages up to 128 mg/kg. Biochemical analysis showed a time-dependent inhibition of MBLs by ZN148 and removal of zinc ions from the active site. Addition of exogenous zinc after ZN148 exposure only restored MBL activity by ∼30%, suggesting an irreversible mechanism of inhibition. Mass-spectrometry and molecular modeling indicated potential oxidation of the active site Cys221 residue. Overall, these results demonstrate the therapeutic potential of a ZN148-carbapenem combination against MBL-producing Gram-negative pathogens and that ZN148 is a highly promising MBL inhibitor that is capable of operating in a functional space not presently filled by any clinically approved compound.

The rise of antimicrobial resistance (AMR) worldwide and the increasing spread of multi-drug-resistant organisms expressing metallo-β-lactamases (MBL) require the development of efficient and clinically available MBL inhibitors. At present, no such inhibitor is available, and research is urgently needed to advance this field. We report herein the development, synthesis, and biological evaluation of chemical compounds based on the selective zinc chelator tris-picolylamine (TPA) that can restore the bactericidal activity of Meropenem (MEM) against Pseudomonas aeruginosa and Klebsiella pneumoniae expressing carbapenemases Verona integron-encoded metallo-β-lactamase (VIM-2) and New Delhi metallo-β-lactamase 1 (NDM-1), respectively. These adjuvants were prepared via standard chemical methods and evaluated in biological assays for potentiation of MEM against bacteria and toxicity (IC) against HepG2 human liver carcinoma cells. One of the best compounds, 15, lowered the minimum inhibitory concentration (MIC) of MEM by a factor of 32-256 at 50 μM within all tested MBL-expressing clinical isolates and showed no activity toward serine carbapenemase expressing isolates. Biochemical assays with purified VIM-2 and NDM-1 and 15 resulted in inhibition kinetics with k/ K of 12.5 min mM and 0.500 min mM, respectively. The resistance frequency of 15 at 50 μM was in the range of 10 to 10. 15 showed good tolerance in HepG2 cells with an IC well above 100 μM, and an in vivo study in mice showed no acute toxic effects even at a dose of 128 mg/kg.

Three new protocols for the nucleophilic halogenations of diazoesters, diazophosphonates, and diazopiperidinylamides as complementary methods to our previously reported electrophilic halogenations are presented for the first time. On the basis of hypervalent α-aryliodonio diazo triflate salts 1A, 2A, and 3A, the corresponding halodiazo compounds are generated via nucleophilic halogenations with tetrabutylammonium halides or potassium halides. The products from subsequent catalytic intermolecular cyclopropanations of the halodiazoesters and halodiazophosphonates and thermal intramolecular C-H insertion of the brominated diazopiperidinylamide are obtained in moderate to good yields after two steps. DFT calculations are presented for the diazoesters to give insight into the mechanism and transition states of the nucleophilic substitutions with the neutral nucleophiles dimethyl sulfide and triethylamine and the bromination with Br(-).

(Halodiazomethyl)phosphonates 2A-C have been generated by a one-pot procedure via a clean, efficient, and rapid deprotonation/electrophilic halogenation sequence from diethyl diazomethylphosphonate 1 (EDP). Subsequent intermolecular Rh(II)-catalyzed cyclopropanation afforded the corresponding halocyclopropylphosphonates 3-10 in moderate to high yields and high diastereomeric ratios. Catalyst loadings down to 0.1 mol % as well as clean and selective product formation were achieved.

New MBL inhibitor renders resistant Gram negative bacteria susceptible to carbapenems.