1,2,4-Triazole-3-thione analogues with an arylakyl group at position 4 as metallo-β-lactamase inhibitors

Probing N-substituted 4-(5-mercapto-4-ethyl-4H-1,2,4-triazol-3-yl)-N-phenylpiperdine-1-carboxamides as potent 15-LOX inhibitors supported with ADME, DFT calculations and molecular docking studies

In our continuous efforts to find out leads against the enzyme 15-lipoxygenase (15-LOX), the current study deals with the synthesis of a series of new N-alkyl/aralkyl/aryl derivatives of 2-(4-ethyl-5-(1-phenylcarbamoyl)piperidine-4H-1,2,4-triazol-3-ylthio)methylacetamide (7a-n) with anti-LOX activities. The synthesis was started by reacting phenylisocyanate with isonipecotate that sequentially converted into N-substituted ester (1), hydrazide (2), semicarbazide (3) and N-ethylated 5-(1-phenylcarbamoyl)piperidine-1,2,4-triazole (4). The final compounds, 7a-n, were obtained by reacting 4 with various N-alkyl/aralkyl/aryl electrophiles. Both the intermediates and target compounds were characterized by FTIR, 1H, 13C NMR spectroscopy, EI-MS and HR-EI-MS spectrometry and screened against soybean 15-LOX by chemiluminescence method. The eight compounds 7e, 7j, 7h, 7a, 7g, 7b, 7n, 7c showed potent inhibitory activities against 15-LOX with values ranging from IC50 0.36 ± 0.15 μM (7e) to IC50 6.75 ± 0.17 μM (7c) compared with the reference quercetin (IC50 4.86 ± 0.14 μM) and baicalein (IC50 2.24 ± 0.13 μM). Two analogues (7l, 7f) had significantly outstanding inhibitory potential with IC50 values 12.15 ± 0.23 μM and 15.54 ± 0.26 μM, whereas, the derivatives 7i, and 7d displayed IC50 values of 21.56 ± 0.27 μM, 23.59 ± 0.24 μM and the compounds 7k, 7m were found inactive. All analogues exhibited blood mononuclear cells (MNCs) viability >75 % at 0.25 mM concentration as determined by MTT method. Calculated pharmacokinetic properties projected good lipophilicity, bioavailability and drug-likeness properties and did not violate Lipinski's/Veber rule. Molecular docking studies revealed lower binding free energies of all the derivatives than the reference compounds. The binding free energies were -9.8 kcal/mol, -9.70 k/mol and -9.20 kcal/mol for 7j, 7h and 7e, respectively, compared with the standard quercetin (-8.47 kcal/mol) and baicalein (-8.98 kcal/mol). The docked ligands formed hydrogen bonds with the amino acid residues Gln598 (7e), Arg260, Val 126 (7h), Gln762, Gln574, Thr443, Arg580 (7j) while other hydrophobic interactions observed therein further stabilized the complexes. The results of density functional theory (DFT) revealed that analogues with more stabilized lower unoccupied molecular orbital (LUMO) had significant enzyme inhibitory activity. The data collectively supports these molecules as leads against 15-LOX and demand further investigations as anti-inflammatory agents.

Current Strategy for Targeting Metallo-β-Lactamase with Metal-Ion-Binding Inhibitors

Currently, antimicrobial resistance (AMR) is a serious health problem in the world, mainly because of the rapid spread of multidrug-resistant (MDR) bacteria. These include bacteria that produce β-lactamases, which confer resistance to β-lactams, the antibiotics with the most prescriptions in the world. Carbapenems are particularly noteworthy because they are considered the ultimate therapeutic option for MDR bacteria. However, this group of antibiotics can also be hydrolyzed by β-lactamases, including metallo-β-lactamases (MBLs), which have one or two zinc ions (Zn2+) on the active site and are resistant to common inhibitors of serine β-lactamases, such as clavulanic acid, sulbactam, tazobactam, and avibactam. Therefore, the design of inhibitors against MBLs has been directed toward various compounds, with groups such as nitrogen, thiols, and metal-binding carboxylates, or compounds such as bicyclic boronates that mimic hydrolysis intermediates. Other compounds, such as dipicolinic acid and aspergillomarasmin A, have also been shown to inhibit MBLs by chelating Zn2+. In fact, recent inhibitors are based on Zn2+ chelation, which is an important factor in the mechanism of action of most MBL inhibitors. Therefore, in this review, we analyzed the current strategies for the design and mechanism of action of metal-ion-binding inhibitors that combat MDR bacteria.

An updated patent review of metallo-β-lactamase inhibitors (2020-2023)

INTRODUCTION

Metallo-β-lactamases (MBLs) are enzymes produced by bacteria that confer resistance to most β-lactam antibiotics, including carbapenems, which have the broadest spectrum of activity. This resistance mechanism poses a significant threat to public health as it drastically reduces treatment options for severe bacterial infections. Developing effective inhibitors against MBLs is crucial to restore susceptibility to β-lactam antibiotics.

AREAS COVERED

This review aims to provide an updated analysis of patents describing novel MBL inhibitors and their potential therapeutic applications that were filed between January 2020 and May 2023.

EXPERT OPINION

Significant advancements were made in the development of selective MBL inhibitors with zinc-binding and zinc-chelating mechanisms of action. Dual inhibitors, targeting simultaneously both serine-β-lactamases (SBLs) and MBLs, represent an interesting alternative approach that is increasingly pertinent for the treatment of infections involving multiple β-lactamases from different Ambler classes. Most examples of MBL-specific inhibitors were focused on the treatment of MBL-mediated infections in Enterobacterales, where IMP-1 was a more difficult target compared with VIM-1 or NDM-1, and much less on Pseudomonas aeruginosa or Acinetobacter baumannii, which are more challenging to address.

Small-molecule inhibitors of bacterial-producing metallo-β-lactamases: insights into their resistance mechanisms and biochemical analyses of their activities

Antibiotic resistance (AR) remains one of the major threats to the global healthcare system, which is associated with alarming morbidity and mortality rates. The defence mechanisms of Enterobacteriaceae to antibiotics occur through several pathways including the production of metallo-β-lactamases (MBLs). The carbapenemases, notably, New Delhi MBL (NDM), imipenemase (IMP), and Verona integron-encoded MBL (VIM), represent the critical MBLs implicated in AR pathogenesis and are responsible for the worst AR-related clinical conditions, but there are no approved inhibitors to date, which needs to be urgently addressed. Presently, the available antibiotics including the most active β-lactam-types are subjected to deactivation and degradation by the notorious superbug-produced enzymes. Progressively, scientists have devoted their efforts to curbing this global menace, and consequently a systematic overview on this topic can aid the timely development of effective therapeutics. In this review, diagnostic strategies for MBL strains and biochemical analyses of potent small-molecule inhibitors from experimental reports (2020-date) are overviewed. Notably, N1 and N2 from natural sources, S3-S7, S9 and S10 and S13-S16 from synthetic routes displayed the most potent broad-spectrum inhibition with ideal safety profiles. Their mechanisms of action include metal sequestration from and multi-dimensional binding to the MBL active pockets. Presently, some β-lactamase (BL)/MBL inhibitors have reached the clinical trial stage. This synopsis represents a model for future translational studies towards the discovery of effective therapeutics to overcome the challenges of AR.

Optimization of 1,2,4-Triazole-3-thiones toward Broad-Spectrum Metallo-β-lactamase Inhibitors Showing Potent Synergistic Activity on VIM- and NDM-1-Producing Clinical Isolates

Metallo-β-lactamases (MBLs) contribute to the resistance of Gram-negative bacteria to carbapenems, last-resort antibiotics at hospital, and MBL inhibitors are urgently needed to preserve these important antibacterial drugs. Here, we describe a series of 1,2,4-triazole-3-thione-based inhibitors displaying an α-amino acid substituent, which amine was mono- or disubstituted by (hetero)aryl groups. Compounds disubstituted by certain nitrogen-containing heterocycles showed submicromolar activities against VIM-type enzymes and strong NDM-1 inhibition (K_i = 10-30 nM). Equilibrium dialysis, native mass spectrometry, isothermal calorimetry (ITC), and X-ray crystallography showed that the compounds inhibited both VIM-2 and NDM-1 at least partially by stripping the catalytic zinc ions. These inhibitors also displayed a very potent synergistic activity with meropenem (16- to 1000-fold minimum inhibitory concentration (MIC) reduction) against VIM-type- and NDM-1-producing ultraresistant clinical isolates, including Enterobacterales and Pseudomonas aeruginosa. Furthermore, selected compounds exhibited no or moderate toxicity toward HeLa cells, favorable absorption, distribution, metabolism, excretion (ADME) properties, and no or modest inhibition of several mammalian metalloenzymes.