Biochemical Characterization of QPX7728, a New Ultrabroad-Spectrum Beta-Lactamase Inhibitor of Serine and Metallo-Beta-Lactamases

Abstract

QPX7728 is a new ultrabroad-spectrum inhibitor of serine and metallo-beta-lactamases (MBLs) from a class of cyclic boronates that gave rise to vaborbactam. The spectrum and mechanism of beta-lactamase inhibition by QPX7728 were assessed using purified enzymes from all molecular classes. QPX7728 inhibits class A extended-spectrum beta-lactamases (ESBLs) (50% inhibitory concentration [IC50] range, 1 to 3 nM) and carbapenemases such as KPC (IC50, 2.9 ± 0.4 nM) as well as class C P99 (IC50 of 22 ± 8 nM) with a potency that is comparable to or higher than recently FDA-approved beta-lactamase inhibitors (BLIs) avibactam, relebactam, and vaborbactam. Unlike those other BLIs, QPX7728 is also a potent inhibitor of class D carbapenemases such as OXA-48 from Enterobacteriaceae and OXA enzymes from Acinetobacter baumannii (OXA-23/24/58, IC50 range, 1 to 2 nM) as well as MBLs such as NDM-1 (IC50, 55 ± 25 nM), VIM-1 (IC50, 14 ± 4 nM), and IMP-1 (IC50, 610 ± 70 nM). Inhibition of serine enzymes by QPX7728 is associated with progressive inactivation with a high-efficiency k2/K ranging from 6.3 × 104 (for P99) to 9.9 × 105 M−1 s−1 (for OXA-23). This inhibition is reversible with variable stability of the QPX7728-beta-lactamase complexes with target residence time ranging from minutes to several hours: 5 to 20 min for OXA carbapenemases from A. baumannii, ∼50 min for OXA-48, and 2 to 3 h for KPC and CTX-M-15. QPX7728 inhibited all tested serine enzymes at a 1:1 molar ratio. Metallo-beta-lactamases NDM, VIM, and IMP were inhibited by a competitive mechanism with fast-on–fast-off kinetics, with Kis of 7.5 ± 2.1 nM, 32 ± 14 nM, and 240 ± 30 nM for VIM-1, NDM-1, and IMP-1, respectively. QPX7728’s ultrabroad spectrum of BLI inhibition combined with its high potency enables combinations with multiple different beta-lactam antibiotics.

Spectrum of Beta-Lactamase Inhibition by the Cyclic Boronate QPX7728, an Ultrabroad-Spectrum Beta-Lactamase Inhibitor of Serine and Metallo-Beta-Lactamases: Enhancement of Activity of Multiple Antibiotics against Isogenic Strains Expressing Single Beta-Lactamases

“…Based on potentiation experiments, QPX7728 was a potent inhibitor of GIM-1 and of CcrA, the MBL from Bacteroides fragilis. QPX7728 also demonstrated inhibitory activity against some but not all MBLs from the IMP sub-class; it was more active in antibiotic potentiation activity against IMP-1/4/13/15/19 than the strain producing IMP-26, in a good agreement with previous biochemical experiments (IC 50 of 0.61 µM vs 4 µM, for IMP-1 and IMP-26, respectively) (11). No activity against on October 10, 2020 by guest http://aac.asm.org/ Downloaded from SPM-1 (which shares 35.5% identity with IMP-1) was detected based on microbiological experiments (no direct biochemical studies have yet performed).…”

“…An extensive medicinal chemistry program guided by our early lead compounds and structurebased design culminated in the discovery of QPX7728 (10). In biochemical studies using purified betalactamases (11), we demonstrated that QPX7728 is a potent inhibitor of several prevalent serine and metallo-beta-lactamases (12)(13)(14) with IC 50 values generally in the low nM range. These biochemical results (11) show that QPX7728 has the broadest spectrum of BLI inhibition among marketed BLIs and those in various stages of clinical development (15,16).…”

“…In biochemical studies using purified betalactamases (11), we demonstrated that QPX7728 is a potent inhibitor of several prevalent serine and metallo-beta-lactamases (12)(13)(14) with IC 50 values generally in the low nM range. These biochemical results (11) show that QPX7728 has the broadest spectrum of BLI inhibition among marketed BLIs and those in various stages of clinical development (15,16). This paper provides further details on the spectrum of beta-lactamase inhibition by QPX7728 in combination with multiple different beta-lactam antibiotics against the panels of isogenic strains expressing single beta-lactamases.…”

Impact of Intrinsic Resistance Mechanisms on Potency of QPX7728, a New Ultrabroad-Spectrum Beta-Lactamase Inhibitor of Serine and Metallo-Beta-Lactamases in Enterobacteriaceae , Pseudomonas aeruginosa, and Acinetobacter baumannii

“…on September 8, 2020 by guest http://aac.asm.org/ Downloaded from QPX7728 (Figure 1) is new cyclic boronic acid beta-lactamase inhibitor (BLI) (1) with inhibition of key serine and metallo beta-lactamases at a nano molar range in biochemical assays with purified enzymes (2). QPX7728 inhibits class A ESBLs and carbapenemases such as KPC as well as class C P99 with a potency that is comparable or higher than recently FDA approved BLIs avibactam, relebactam and vaborbactam.…”

Specific NDM-1 Inhibitor of Isoliquiritin Enhances the Activity of Meropenem against NDM-1-positive Enterobacteriaceae in vitro

“…NDM-1 is one of the most important contributors to β-lactamase resistance by Gram-negative bacteria and has led to the loss of efficacy of many clinically available β-lactam antibiotics [26]. Screening an inhibitor from ready-made drugs or leading compounds that specifically target antibiotic resistance enzymes is one of the fastest and most effective strategies against antibiotic resistance [27][28][29][30]. Taniborbactam and QPX7728 have been reported as the novel broad-Spectrum β-lactamase inhibitors for fighting β-lactamase-producing bacteria [27][28][29][30].…”