Bisthiazolidines (BTZs) as Cross-class Inhibitors of Metallo-beta-Lactamases (MBLs)

HINCHLIFFE, P.; GONZALEZ, M.; MOJICA, M.F.; SAIZ, C.; CASTILLO, V.; GONZALEZ, J. ; KOSMOPOULOU, M.; TOOKE, C.; LLARRULL, L. I.; MAHLER, G.; BONOMO, R.A.; SPENCER, J.; VILA, A.J.

San Diego

Congreso; ICAAC/ICC 2015; 2015

American Society for Microbiology

Background:MBLs hydrolyze all beta-lactams excepting monobactams and are disseminating in Enterobacteriaceae and Gram-negative non-fermentors. MBLs escape currently available clinical inhibitors while their structural heterogenity and mechanistic variability complicates efforts to identify universally effective MBL inhibitors. We have used structural, biochemical and microbiological methods to evaluate D- and L- BTZs- bicyclic compounds with many structural features of beta-lactams and an additional free thiol- as inhibitors of all MBL subclasses.Methods: BTZ inhibition of MBLs of all three subclasses was followed by monitoring imipenem hydrolysis. Structures of MBL:BTZ complexes were determined by X-ray diffraction. Antibacterial activity was assessed by modified time-kill assays.Results: BTZs are μM inhibitors of MBLs of all three subclasses (range 0.26 - 32 μM). Inhibition of subclass B1 and B3 enzymes varied little with inhibitor stereochemistry or presence of a gem-dimethyl group. The B2 MBL Sfh-I showed strong preference for L-BTZ inhibitors. The mode of inhibitor binding varied with enzyme and inhibitor stereochemistry: binding to B1 (BcII, IMP-1, NDM-1) and B3 (L1) enzymes invariably featured the free thiol bridging the two zinc ions but, while L-BTZs bound similarly to both subclasses, D-BTZs bounddifferently to B1 (IMP-1) and B3 (L1) MBLs. BTZs potentiated beta-lactam activity against producer strains of IMP-1, NDM-1, Sfh-1 and GOB-18 in time-kill assays by > 102 reduction in CFUs.Conclusions: BTZs are μM inhibitors of all MBL classes that can penetrate the bacterial periplasm. Crossclass activity arises from adoption of different binding modes to different MBLs, the strength of the zinc:thiol interaction, and replication of aspects of beta-lactam binding such as carboxylate recognition by conserved residues. D-BTZ interactions with B1 MBLs most closely resembled the expected mode of beta-lactam binding, but L-BTZs possessed the best activity across the full range of enzymes. These data will direct future work aimed at improving BTZ potency.