Imitation of β-lactam binding enables broad-spectrum metallo-β-lactamase inhibitors

Carbapenems are vital antibiotics, but their efficacy is increasingly compromised by metallo-beta-lactamases (MBLs). Here we report the discovery and optimization of potent broad-spectrum MBL inhibitors. A high-throughput screen for NDM-1 inhibitors identified indole-2-carboxylates (InCs) as potential beta-lactamase stable beta-lactam mimics. Subsequent structure-activity relationship studies revealed InCs as a new class of potent MBL inhibitor, active against all MBL classes of major clinical relevance. Crystallographic studies revealed a binding mode of the InCs to MBLs that, in some regards, mimics that predicted for intact carbapenems, including with respect to maintenance of the Zn(II)-bound hydroxyl, and in other regards mimics binding observed in MBL-carbapenem product complexes. InCs restore carbapenem activity against multiple drug-resistant Gram-negative bacteria and have a low frequency of resistance. InCs also have a good in vivo safety profile, and when combined with meropenem show a strong in vivo efficacy in peritonitis and thigh mouse infection models.Peer reviewe

In vitro efficacy of Imipenem-Relebactam and Cefepime-AAI101 against a global collection of ESBL-positive and carbapenemase-producing Enterobacteriaceae

Objectives: In vitro evaluation of the potential clinical efficacy of the novel β-lactam/β-lactamase-inhibitor combinations including imipenem-relebactam (IPM-REL) and cefepime-AAI101 (enmetazobactam) (FEP-AAI) against contemporary multidrug-resistant Enterobacteriaceae. Methods: Agar-based MIC screening against MDR-Enterobacteriaceae (n=264) was used to evaluate the in vitro efficacy of IPM-REL and FEP-AAI, to compare the results with established combinations, and to investigate alternative β-lactam partners for REL and AAI. The inhibition activities of REL, AAI and the comparators avibactam (AVI) and tazobactam, against isolated recombinant β-lactamases covering representatives from all four Ambler classes of β-lactamases were tested using a fluorescence-based assay. Results: Using recombinant proteins, all four inhibitors were highly active against the tested class A serine β-lactamases (SBLs); REL and AVI showed moderate activity against the Class C AmpC from P. aeruginosa and the Class D OXA-10/-48 SBLs, but outperformed tazobactam and AAI. All tested inhibitors lacked activity against Class B MBLs. In the presence of REL, IPM, but not AAI susceptibility increased against KPC-positive and OXA-48-positive isolates. Both aztreonam-AVI and ceftolozane-tazobactam were more efficacious than IPM-REL. In all the tested combinations, AAI was a more effective inhibitor of class A β-lactamases (ESBLs) than the established inhibitors. Conclusions: The results lead to the proposal of alternative combination therapies involving REL and AAI to potentiate the use of β-lactams against clinical Gram-negative isolates expressing a variety of β-lactamases. These results highlight the potential of novel combinations for combating strains not covered by existing therapies.</p

Wild rice growing at Camp A-Z in Chuckfee Bay, photo 1

The bicyclic boronate VNRX-5133 (taniborbactam) is a new type of β-lactamase inhibitor in clinical development. We report that VNRX-5133 inhibits serine-β-lactamases (SBLs) and some clinically important metallo-β-lactamases (MBLs), including NDM-1 and VIM-1/2. VNRX-5133 activity against IMP-1 and tested B2/B3 MBLs was lower/not observed. Crystallography reveals how VNRX-5133 binds to the class D SBL OXA-10 and MBL NDM-1. The crystallographic results highlight the ability of bicyclic boronates to inhibit SBLs and MBLs via binding of a tetrahedral (sp3) boron species. The structures imply conserved binding of the bicyclic core with SBLs/MBLs. With NDM-1, by crystallography, we observed an unanticipated VNRX-5133 binding mode involving cyclization of its acylamino oxygen onto the boron of the bicyclic core. Different side-chain binding modes for bicyclic boronates for SBLs and MBLs imply scope for side-chain optimization. The results further support the "high-energy-intermediate" analogue approach for broad-spectrum β-lactamase inhibitor development and highlight the ability of boron inhibitors to interchange between different hybridization states/binding modes