Infections caused by multidrug resistant (MDR) bacteria are a major public health threat. Carbapenems are among the most potent antimicrobial agents that are commercially available to treat MDR bacteria. Bacterial production of carbapenem-hydrolysing metallo-β-lactamases (MBLs) challenges their safety and efficacy, with subclass B1 MBLs hydrolysing almost all β-lactam antibiotics. MBL inhibitors would fulfil an urgent clinical need by prolonging the lifetime of these life-saving drugs. Here we report the synthesis and activity of a series of 2-mercaptomethyl-thiazolidines (MMTZs), designed to replicate MBL interactions with reaction intermediates or hydrolysis products. MMTZs are potent competitive inhibitors of B1 MBLs in vitro (e.g., Ki = 0.44 μM vs. NDM-1). Crystal structures of MMTZ complexes reveal similar binding patterns to the most clinically important B1 MBLs (NDM-1, VIM-2 and IMP-1), contrasting with previously studied thiol-based MBL inhibitors, such as bisthiazolidines (BTZs) or captopril stereoisomers, which exhibit lower, more variable potencies and multiple binding modes. MMTZ binding involves thiol coordination to the Zn(II) site and extensive hydrophobic interactions, burying the inhibitor more deeply within the active site than D/L-captopril. Unexpectedly, MMTZ binding features a thioether–π interaction with a conserved active-site aromatic residue, consistent with their equipotent inhibition and similar binding to multiple MBLs. MMTZs penetrate multiple Enterobacterales, inhibit NDM-1 in situ, and restore carbapenem potency against clinical isolates expressing B1 MBLs. Based on their inhibitory profile and lack of eukaryotic cell toxicity, MMTZs represent a promising scaffold for MBL inhibitor development. These results also suggest sulphur–π interactions can be exploited for general ligand design in medicinal chemistry.
Bibliographical noteFunding Information:
This work was supported by the National Institute of Allergy and Infectious Diseases of the National Institutes of Health (NIH) to R. A. B. under Award Numbers R01AI063517 and R01AI072219, to R. A. B., G. M., J. S. and A. J. V. under Award Number R01AI100560 and to B. S. under Award Numbers R01 AI130060 and AI117211. This study was also supported in part by funds and/or facilities provided by the Cleveland Department of Veterans Affairs, Award Number 1I01BX001974 to R. A. B. from the Biomedical Laboratory Research & Development Service of the VA Office of Research and Development, and the Geriatric Research Education and Clinical Center VISN 10. The content is solely the responsibility of the authors and does not necessarily represent the official views of the NIH or the Department of Veterans Affairs. GM thanks M. Maćıas and L. Suescun from Cryssmat-Lab/DETEMA for the single crystal X-ray diffraction structure determination and data deposition. VM is recipient of a fellowship from Comisión Académica de Posgrado (CAP-Udelar). We thank Diamond Light Source for beamtime (proposal MX17212), and the staff of beamlines I03 and I04 for assistance with crystal testing and data collection. Funding for R. S. was provided by the University of Bristol. This work was supported by grant PICT-2016-1657 from ANPCyT to A. J. V. C. B., D. M. M. and A. J. V. are staff members from CONICET. M. A. R. is recipient of a fellowship from CONICET.
© The Royal Society of Chemistry 2021.