Synthesis and Preclinical Evaluation of TPA-Based Zinc Chelators as Metallo-β-lactamase Inhibitors

Abstract

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.

ZN148 Is a Modular Synthetic Metallo-β-Lactamase Inhibitor That Reverses Carbapenem Resistance in Gram-Negative Pathogens In Vivo

“…TPA is a known lipophilic zinc chelator with high affinity (10 11 M) towards Zn 2+ and has previously been shown to inhibit MBLs (23)(24)(25)(26). Synthesis of ZN148 is achieved through a high-on September 1, 2020 by guest http://aac.asm.org/ Downloaded from yield, 3-step synthesis from commercially available building blocks (Fig.…”

Synthesis and biological evaluation of new dipicolylamine zinc chelators as metallo-β-lactamase inhibitors

“…New small molecules have also emerged very recently on the basis of 2,6-dipicolinic acid which displayed a propensity to chelate zinc. [25][26] We have earlier studied TPA as a zinc chelator, 27 however, we now wanted to study dipicolylamine (DPA) as the chelating moiety. [28][29] As metal chelators are generally toxic, we need a chelator that is selective for zinc, and by selective we mean that they bind weaker to iron, manganese, sodium, potassium, calcium and other relevant biological cations than to zinc.…”

Binding of 2-(Triazolylthio)acetamides to Metallo-β-lactamase CcrA Determined with NMR

“…To be effective, such compounds should have a 1 nM to 1 pM zinc binding affinity ( K d ). 24 For CcrA, the affinities of both zinc sites have an upper limit of ≤10 μM, but there is evidence for a tight binding, and for an actual affinity much lower than 10 μM. 25 Although the zinc affinities of the 2TTA-type MBLIs have not yet been determined experimentally, these are presumed to interact with, and not deprive the zinc ions from the active site of CcrA.…”