Class A beta-lactamases--enzyme-inhibitor interactions and resistance

Pharmacological Evaluation of Bioisosterically Replaced and Triazole- Tethered Derivatives for Anticancer Therapy

Cancer has been the cause of the highest number of deaths in the human population despite the development and advancement in treatment therapies. The toxicity, drug resistance, and side effects of the current medicaments and therapies have left the void for more research and development. One of the possibilities to fill this void is by incorporating Triazole moieties within existing anticancer pharmacophores to develop new hybrid drugs with less toxicity and more potency. The placement of nitrogen in the triazole ring has endowed its characterization of being integrated with anticancer pharmacophores via bioisosteric replacement, click chemistry and organocatalyzed approaches. This review paper emphasizes the discussions from articles published from the early 2000s to the current 2020s about the triazole-based derivatives used in anticancer therapy, elaborating more on their chemical structures, target receptors or enzymes, mechanism of action, structure-activity relationships, different triazole-derived hybrid drugs under clinical and nonclinical trials, and recent advancements toward developing more potent and less toxic anticancer agents.

Rational design and synthesis of novel phenyltriazole derivatives targeting MRSA cell wall biosynthesis

Antimicrobial resistance in methicillin-resistant Staphylococcus aureus (MRSA) is a major global health challenge. This study reports the design and synthesis of novel phenyltriazole derivatives as potential anti-MRSA agents. The new scaffold replaces the thiazole core with a 1,2,3-triazole ring, enhancing antimicrobial efficacy and physicochemical properties. A series of derivatives were synthesized and evaluated, with four compounds (20, 23, 29 and 30) showing significant activity against MRSA (MIC ≤ 4 μg mL-1). Compound 29 emerged as the most promising candidate, showing rapid bactericidal activity and superior performance over vancomycin in time-kill assays. It exhibited selective toxicity against bacterial cells, minimal cytotoxicity in human cell lines and low hemolytic activity. Mechanistic studies showed that compound 29 targets the bacterial cell wall by binding to penicillin-binding protein 2a (PBP2a), disrupting cell wall integrity. Additionally, it showed strong anti-biofilm activity and reduced MRSA biofilms by up to 40%. Preliminary pharmacokinetic profiles suggested a favorable profile, including a prolonged plasma half-life and good oral bioavailability. These results suggest that compound 29 is a promising lead for further development in the fight against MRSA.

The role of piperacillin/tazobactam in the treatment of Hidradenitis suppurativa

Background: Hidradenitis suppurativa (HS) is a chronic inflammatory skin disease. Most patients with moderate-to-severe disease require long-term antibiotic treatment, or biologic treatments to control their disease. Despite these interventions, relapses are common. This study evaluated the effectiveness of piperacillin/tazobactam treatment in patients with Hurley stage II and III HS who experienced disease flares and did not respond to conventional antibiotic and biologic treatment. Methods: Patients with HS hospitalized at the Department of Dermatology, Sheba Medical Center between August 2021 and January 2023 were retrospectively analyzed. Results: A cohort of ten such patients were treated with piperacillin/tazobactam for 6-21 days. Eight (80%) and two (20%) patients respectively demonstrated 2- and 1-grade improvements, from their baseline HS-Physician Global Assessment score. During the follow-up period, nine patients were monitored. HS Clinical Response (HiSCR) was achieved in six (66.7%) and five (55.6%) patients at the 3- and 6-month follow-up visits, respectively. Conclusions: In conclusion, Piperacillin/tazobactam emerges as a promising therapeutic option for disease flare-up in patients with Hurley stage II and III HS who do not respond to conventional treatment. Thus, piperacillin/tazobactam should be considered as crisis therapy for this patient subset.

NMR insights into β-Lactamase activity of UVI31+ Protein from Chlamydomonas reinhardtii

β-Lactamases (EC 3.5.2.6) confer resistance against β-lactam group-containing antibiotics in bacteria and higher eukaryotes, including humans. Pathogenic bacterial resistance against β-lactam antibiotics is a primary concern for potential therapeutic developments and drug targets. Here, we report putative β-lactamase activity, sulbactam binding (a β-lactam analogue) in the low μM affinity range, and site-specific interaction studies of a 14 kDa UV- and dark-inducible protein (abbreviated as UVI31+, a BolA homologue) from Chlamydomonas reinhartii. Intriguingly, the solution NMR structure of UVI31 + bears no resemblance to other known β-lactamases; however, the sulbactam binding is found at two sites rich in positively charged residues, mainly at the L2 loop regions and the N-terminus. Using NMR spectroscopy, ITC and MD simulations, we map the ligand binding sites in UVI31 + providing atomic-level insights into its β-lactamase activity. Current study is the first report on β-lactamase activity of UVI31+, a BolA analogue, from C. reinhartii. Furthermore, our mutation studies reveal that the active site serine-55 is crucial for β-lactamase activity.

Bipiperidinyl Derivatives of Cannabidiol Enhance Its Antiproliferative Effects in Melanoma Cells

Cannabis and its major cannabinoid cannabidiol (CBD) are reported to exhibit anticancer activity against skin tumors. However, the cytotoxic effects of other minor cannabinoids and synthetic CBD derivatives in melanoma are not fully elucidated. Herein, the antiproliferative activity of a panel of phytocannabinoids was screened against murine (B16F10) and human (A375) melanoma cells. CBD was the most cytotoxic natural cannabinoid with respective IC50 of 28.6 and 51.6 μM. Further assessment of the cytotoxicity of synthetic CBD derivatives in B16F10 cells identified two bipiperidinyl group-bearing derivatives (22 and 34) with enhanced cytotoxicity (IC50 = 3.1 and 8.5 μM, respectively). Furthermore, several cell death assays including flow cytometric (for apoptosis and ferroptosis) and lactate dehydrogenase (for pyroptosis) assays were used to characterize the antiproliferative activity of CBD and its bipiperidinyl derivatives. The augmented cytotoxicity of 22 and 34 in B16F10 cells was attributed to their capacity to promote apoptosis (as evidenced by increased apoptotic population). Taken together, this study supports the notion that CBD and its derivatives are promising lead compounds for cannabinoid-based interventions for melanoma management.

Towards Antibiotic Synthesis in Continuous-Flow Processes

Continuous-flow chemistry has become a mainstream process and a notable trend among emerging technologies for drug synthesis. It is routinely used in academic and industrial laboratories to generate a wide variety of molecules and building blocks. The advantages it provides, in terms of safety, speed, cost efficiency and small-equipment footprint compared to analog batch processes, have been known for some time. What has become even more important in recent years is its compliance with the quality objectives that are required by drug-development protocols that integrate inline analysis and purification tools. There can be no doubt that worldwide government agencies have strongly encouraged the study and implementation of this innovative, sustainable and environmentally friendly technology. In this brief review, we list and evaluate the development and applications of continuous-flow processes for antibiotic synthesis. This work spans the period of 2012-2022 and highlights the main cases in which either active ingredients or their intermediates were produced under continuous flow. We hope that this manuscript will provide an overview of the field and a starting point for a deeper understanding of the impact of flow chemistry on the broad panorama of antibiotic synthesis.

Biochemical exploration of β-lactamase inhibitors

The alarming rise of microbial resistance to antibiotics has severely limited the efficacy of current treatment options. The prevalence of β-lactamase enzymes is a significant contributor to the emergence of antibiotic resistance. There are four classes of β-lactamases: A, B, C, and D. Class B is the metallo-β-lactamase, while the rest are serine β-lactamases. The clinical use of β-lactamase inhibitors began as an attempt to combat β-lactamase-mediated resistance. Although β-lactamase inhibitors alone are ineffective against bacteria, research has shown that combining inhibitors with antibiotics is a safe and effective treatment that not only prevents β-lactamase formation but also broadens the range of activity. These inhibitors may cause either temporary or permanent inhibition. The development of new β-lactamase inhibitors will be a primary focus of future research. This study discusses recent advances in our knowledge of the biochemistry behind β-lactam breakdown, with special emphasis on the mechanism of inhibitors for β-lactam complexes with β-lactamase. The study also focuses on the pharmacokinetic and pharmacodynamic properties of all inhibitors and then applies them in clinical settings. Our analysis and discussion of the challenges that exist in designing inhibitors might help pharmaceutical researchers address root issues and develop more effective inhibitors.

Synthesis of New Triazole-Based Thiosemicarbazone Derivatives as Anti-Alzheimer's Disease Candidates: Evidence-Based In Vitro Study

Triazole-based thiosemicarbazone derivatives (6a-u) were synthesized then characterized by spectroscopic techniques, such as 1HNMR and 13CNMR and HRMS (ESI). Newly synthesized derivatives were screened in vitro for inhibitory activity against acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) enzymes. All derivatives (except 6c and 6d, which were found to be completely inactive) demonstrated moderate to good inhibitory effects ranging from 0.10 ± 0.050 to 12.20 ± 0.30 µM (for AChE) and 0.20 ± 0.10 to 14.10 ± 0.40 µM (for BuChE). The analogue 6i (IC₅₀ = 0.10 ± 0.050 for AChE and IC₅₀ = 0.20 ± 0.050 µM for BuChE), which had di-substitutions (2-nitro, 3-hydroxy groups) at ring B and tri-substitutions (2-nitro, 4,5-dichloro groups) at ring C, and analogue 6b (IC₅₀ = 0.20 ± 0.10 µM for AChE and IC₅₀ = 0.30 ± 0.10 µM for BuChE), which had di-Cl at 4,5, -NO₂ groups at 2-position of phenyl ring B and hydroxy group at ortho-position of phenyl ring C, emerged as the most potent inhibitors of both targeted enzymes (AChE and BuChE) among the current series. A structure-activity relationship (SAR) was developed based on nature, position, number, electron donating/withdrawing effects of substitution/s on phenyl rings. Molecular docking studies were used to describe binding interactions of the most active inhibitors with active sites of AChE and BuChE.

The 1,2,3-triazole 'all-in-one' ring system in drug discovery: a good bioisostere, a good pharmacophore, a good linker, and a versatile synthetic tool

INTRODUCTION

The 1,2,3-triazole ring occupies an important space in medicinal chemistry due to its unique structural properties, synthetic versatility and pharmacological potential making it a critical scaffold. Since it is readily available through click chemistry for creating compound collections against various diseases, it has become an emerging area of interest for medicinal chemists.

AREAS COVERED

This review article addresses the unique properties of the1,2,3-triazole nucleus as an intriguing ring system in drug discovery while focusing on the most recent medicinal chemistry strategies exploited for the design and development of 1,2,3-triazole analogs as inhibitors of various biological targets.

EXPERT OPINION

Evidently, the 1,2,3-triazole ring with unique structural features has enormous potential in drug design against various diseases as a pharmacophore, a bioisoster or a structural platform. The most recent evidence indicates that it may be more emerging in drug molecules in near future along with an increasing understanding of its prominent roles in drug structures. The synthetic feasibility and versatility of triazole chemistry make it certainly ideal for creating compound libraries for more constructive structure-activity relationship studies. However, more comparative and target-specific studies are needed to gain a deeper understanding of the roles of the 1,2,3-triazole ring in molecular recognition.[Figure: see text].

A Recent Overview of 1,2,3-Triazole-Containing Hybrids as Novel Antifungal Agents: Focusing on Synthesis, Mechanism of Action, and Structure-Activity Relationship (SAR)

A pharmacophore system has been found as 1,2,3-triazole, a five-membered heterocycle ring with nitrogen heteroatoms. These heterocyclic compounds can be produced using azide-alkyne cycloaddition processes catalyzed by ruthenium or copper. The bioactive compounds demonstrated antitubercular, antibacterial, anti-inflammatory, anticancer, antioxidant, antiviral, and antidiabetic properties. This heterocycle molecule, in particular, with one or more 1,2,3-triazole cores has been found to have the most powerful antifungal effects. The goal of this review is to highlight recent developments in the synthesis and structure-activity relationship (SAR) investigation of this prospective fungicidal chemical. Also there have been explained drugs and mechanism of action of a triazole compound with antifungal activity. This review will be useful in a variety of fields, including medicinal chemistry, organic chemistry, mycology, and pharmacology.

Impact of Mutation on the Structural Stability and the Conformational Landscape of Inhibitor-Resistant TEM β-Lactamase: A High-Performance Molecular Dynamics Simulation Study

Gain-of-function mutations and structural adjustment toward β-lactamase inhibitors in the TEM-type β-lactamases among the uropathogenic E. coli (UPEC) culminate in treatment complications and demands detailed investigation. In this study, uncharacterized amino acid substitutions, M69L/I84V/W165G/V184A/V262I/N276S, in inhibitor-resistant TEM (IRT) β-lactamase isolated from clinical UPEC were subjected to extensive molecular dynamics (EMD) simulations for 100 ns to estimate parameters such as root-mean-square deviation (RMSD), root-mean-square fluctuation (RMSF), the radius of gyration (R_g), contour plot (R_g/RMSD), secondary structure element (SSE), etc. Residue interaction networks, principal component analysis (PCA), and correlation heatmaps were generated to predict the relation between functionally important atomic motions to uncover the structural stability of the mutants. To avoid the false positive conclusion of the simulation study, we performed three identically parameterize replicas of 100 ns each. Alterations in hydrophobic interactions resulted in conformation changes exhibited as comparable residue interaction networks. Besides, PCA and porcupine plot analysis based on the ensemble of structure from molecular dynamics trajectories revealed the collective atomic motions of the IRT variants that impart structural flexibility to their active site loop. This study conducted on IRT mutants that delineate intricate protein motions contributes to their stability and folding, which is an absolute necessity for designing candidate molecules owing to the clinical threat of emerging resistance against potent β-lactam antibiotics.

Triazole, imidazole, and thiazole-based compounds as potential agents against coronavirus

The expansion of the novel coronavirus known as SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2), COVID-19 (coronavirus disease 2019), or 2019-nCoV (2019 novel coronavirus) is a global concern over its pandemic potential. The need for therapeutic alternatives to stop this new pandemic is urgent. Nowadays, no efficacious therapy is available, and vaccines and drugs are underdeveloped to cure or prevent SARS-CoV-2 infections in many countries. Some vaccines candidates have been approved; however, a number of people are still skeptical of this coronavirus vaccines. Probably because of issues related to the quantity of the vaccine and a possible long-term side effects which are still being studied. The previous pandemics of infections caused by coronavirus, such as SARS-CoV in 2003, the Middle East respiratory syndrome coronavirus (MERS-CoV) in 2012, HCoV-229E, and HCoV-OC43 were described in the 1960 s, -HCoV-NL63 isolated in 2004, and HCoV-HKU1identified in 2005 prompted researchers to characterize many compounds against these viruses. Most of them could be potentially active against the currently emerging novel coronavirus. Five membered nitrogen heterocycles with a triazole, imidazole, and thiazole moiety are often found in many bioactive molecules such as coronavirus inhibitors. This present work summarizes to review the biological and structural studies of these compound types as coronavirus inhibitors.

Dextran based amphiphilic self-assembled biopolymeric macromolecule synthesized via RAFT polymerization as indomethacin carrier

This work demonstrates a facile pathway to develop a biopolymer based amphiphilic macromolecule through reversible addition-fragmentation chain transfer (RAFT) polymerization, using dextran (a biopolymer) as starting material. Also, a new hydrophobic monomer [2-methyl-acrylic acid 1-benzyl-1H-[1,2,3] triazol-4-ylmethyl ester (MABTE)] has been synthesized using methacrylic acid via "click" approach. The resultant copolymer displays controlled radical polymerization characteristics: narrow polydispersity (Ð) and controlled molecular weight as obtained through advanced polymer chromatography (APC) analysis. In aqueous solution, the copolymer can proficiently be self-assembled to provide micellar structure, which has been evidenced from field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) analyses. The in-vitro cytotoxicity study illustrates the nontoxic nature of the copolymer up to 100 μg/mL polymer concentration. The copolymer has been found to be worthy as an efficient carrier for the sustained release of hydrophobic drug: Indomethacin (IND).

Infrared MALDI Mass Spectrometry with Laser-Induced Postionization for Imaging of Bacterial Colonies

Ultraviolet matrix-assisted laser desorption ionization mass spectrometry imaging (UV-MALDI-MSI) is a powerful tool to visualize bacterial metabolites in microbial colonies and in biofilms. However, a challenge for the method is the efficient extraction of analytes from deeper within the bacterial colonies and from the cytoplasm of individual cells during the matrix coating step. Here, we used a pulsed infrared (IR) laser of 2.94 μm wavelength to disrupt and ablate bacterial cells without a prior coating with a MALDI matrix. Instead, tissue water or, in some experiments, in addition a small amount of glycerol was exploited for the deposition of the IR laser energy and for supporting the ionization of the analytes. Compared to water, glycerol exhibits a lower vapor pressure, which prolonged the available measurement time window within an MSI experiment. Mass spectra were acquired with a hybrid Synapt G2-S HDMS instrument at a pixel size of 120 μm. A frequency-quadrupled q-switched Nd:YAG laser with 266 nm wavelength served for laser-induced postionization (MALDI-2). In this way, the ion abundances of numerous small molecules such as nucleobases, 2-alkyl-quinolones, a prominent class of Pseudomonas aeruginosa signaling molecules involved in one of the three quorum-sensing pathways, and also the signals of various bacterial phospholipids were boosted, partially by orders of magnitude. We analyzed single and cocultured colonies of Gram-negative P. aeruginosa and of Gram-positive Bacillus subtilis and Staphylococcus aureus as exemplary bacterial systems. To enable a rapid (within 5 s) MSI-compatible steam inactivation in a custom-made autoclave filled with hot water steam, bacterial cultures were grown on porous polyamide membranes. Compared to a UV-MALDI-2-MS measurement of the same systems, mass spectra with a reduced low mass background were generally generated. This resulted in the unequivocal detection of numerous metabolites only with the IR laser. In a fundamental part of our study, and to optimize the IR-MALDI-2 approach for the highest analytical sensitivity, we characterized the expansion dynamics of the particle plume as generated by the IR laser. Here, we recorded the total ion count and the intensities of selected signals registered from P. aeruginosa samples as a function of the interlaser delay and buffer gas pressure in the ion source. The data revealed that the IR-MALDI-2 ion signals are primarily generated from slow particles having mean velocities of ∼10 m/s. Interestingly, two different pressure/delay time regimes of the optimized ionization efficiency for phospholipids and smaller metabolites, respectively, were revealed, a result pointing to yet-unknown convoluted reaction cascades. The described IR-MALDI-2 method could be a helpful new tool for a microbial mass spectrometry imaging of small molecules requiring little sample preparation.

Design and Characterisation of Inhibitory Peptides against Bleg1_2478, an Evolutionary Divergent B3 Metallo-β-lactamase

Previously, a hypothetical protein (HP) termed Bleg1_2437 (currently named Bleg1_2478) from Bacillus lehensis G1 was discovered to be an evolutionary divergent B3 subclass metallo-β-lactamase (MBL). Due to the scarcity of clinical inhibitors for B3 MBLs and the divergent nature of Bleg1_2478, this study aimed to design and characterise peptides as inhibitors against Bleg1_2478. Through in silico docking, RSWPWH and SSWWDR peptides with comparable binding energy to ampicillin were obtained. In vitro assay results showed RSWPWH and SSWWDR inhibited the activity of Bleg1_2478 by 50% at concentrations as low as 0.90 µM and 0.50 µM, respectively. At 10 µM of RSWPWH and 20 µM of SSWWDR, the activity of Bleg1_2478 was almost completely inhibited. Isothermal titration calorimetry (ITC) analyses showed slightly improved binding properties of the peptides compared to ampicillin. Docked peptide-protein complexes revealed that RSWPWH bound near the vicinity of the Bleg1_2478 active site while SSWWDR bound at the center of the active site itself. We postulate that the peptides caused the inhibition of Bleg1_2478 by reducing or blocking the accessibility of its active site from ampicillin, thus hampering its catalytic function.

Polypharmacological drug actions of recently FDA approved antibiotics

The current epidemic of antibiotic resistant bacterial infections has fueled the demand for novel antibiotics exhibiting both antibacterial efficacy and anti-drug resistance. This need has not been fully satisfied by the conventional "one target-one molecule" approach. Consequently, there has been rising interest in the development of multi-target antibiotics. Over the past two decades, 52% (14 out of 27) of the FDA approved antibiotics have demonstrated synergistic, multi-target mechanisms of action. Among these are three second-generation lipoglycopeptides, five new generation quinolones and six modernized β-lactams. This review focuses on the structure-activity relationship (SAR) analysis and the polypharmacological drug action of these antibiotics, to reveal how these multi-target antibiotics achieve the dual objectives of maximizing bactericidal or bacteriostatic efficacy and minimizing antibiotic resistance. The entrance of multi-target antibiotics into the FDA-approved regimens represents a milestone in the evolution of drug discovery as it has transcended from chemical library screening to rational drug design.

Fluorogenic Probes/Inhibitors of β-Lactamase and their Applications in Drug-Resistant Bacteria

β-Lactam antibiotics are generally perceived as one of the greatest inventions of the 20^th century, and these small molecular compounds have saved millions of lives. However, upon clinical application of antibiotics, the β-lactamase secreted by pathogenic bacteria can lead to the gradual development of drug resistance. β-Lactamase is a hydrolase that can efficiently hydrolyze and destroy β-lactam antibiotics. It develops and spreads rapidly in pathogens, and the drug-resistant bacteria pose a severe threat to human health and development. As a result, detecting and inhibiting the activities of β-lactamase are of great value for the rational use of antibiotics and the treatment of infectious diseases. At present, many specific detection methods and inhibitors of β-lactamase have been developed and applied in clinical practice. In this Minireview, we describe the resistance mechanism of bacteria producing β-lactamase and further summarize the fluorogenic probes, inhibitors of β-lactamase, and their applications in the treatment of infectious diseases. It may be valuable to design fluorogenic probes with improved selectivity, sensitivity, and effectiveness to further identify the inhibitors for β-lactamases and eventually overcome bacterial resistance.

The First Egyptian Report Showing the Co-Existence of bla NDM-25, bla OXA-23, bla OXA-181, and bla GES-1 Among Carbapenem-Resistant K. pneumoniae Clinical Isolates Genotyped by BOX-PCR

Background and Objective

The emergence of carbapenem-resistant K. pneumoniae (CRKP) continues to escalate and is alarming because of the emergence of pan drug-resistant strains. The objective of this study was to investigate the existence of 12 carbapenemase genes among CRKP clinical isolates.

Methods

Ninety-six Klebsiella spp. clinical isolates were collected. The isolates were identified phenotypically and genotypically. These isolates were screened for susceptibility to 24 different antibiotics. The modified Hodge test (MHT) and the Carba Nordmann/Poirel (NP) test were used to phenotypically screen carbapenem-resistant strains for carbapenemase production. Phenotypic characterization of carbapenemases was performed using the combined disk synergy test (CDST). Additionally, the presence of 12 carbapenemase genes in CRKP isolates was investigated. The DNA sequence of bla _NDM and bla _GES genes was determined. The BOX-PCR technique was used to determine the clonal relationship between CRKP isolates.

Results

All carbapenem-resistant isolates were related to K. pneumoniae. Susceptibility testing showed that 19.79% (19/96) of the collected isolates were carbapenem-resistant. Of the CRKP isolates, 68.42% (13/19) tested positive for the MHT and Carba NP test. CDST showed that 42.11% (8/19), 63.16% (12/19), 47.37% (9/19), and 73.68% (14/19) of the CRKP isolates tested positive for the inhibitory effect of clavulanic acid, sulbactam, phenylboronic acid, and tazobactam, respectively, while 84.21% (16/19) and 68.42% (13/16) tested positive for the inhibitory effect of EDTA and mercaptopropionic acid, respectively. It was found that 10.53% (2/19) of the isolates tested positive for the inhibitory effect of sodium chloride. Molecular investigation of carbapenemases showed that 26.32% (5/19), 73.68% (14/19), 21.05% (4/19), 10.53% (2/19), and 5.26% (1/19) of the isolates tested positive for bla _NDM, bla _OXA-48, bla _OXA-181, bla _OXA-51, and bla _OXA-23, respectively. None of the isolates tested positive for bla _OXA-40 and bla _OXA-58. Two allelic variants of bla _NDM (bla _NDM-1 and bla _NDM-25) were detected. BOX-PCR revealed high clonal relatedness between CRKP isolates.

Conclusion

MHT was more sensitive than Carba NP test for evaluating carbapenemase production and class D carbapenemase genes were the most prevalent of the 12 carbapenemase genes that were evaluated.

Application of triazoles as bioisosteres and linkers in the development of microtubule targeting agents

The triazole ring system has emerged as an exciting prospect in the optimization studies of promising lead molecules in the quest for new drugs for clinical usage. Several marketed drugs possess these versatile moieties that are used in a wide range of medical indications. This stems from the unique intrinsic properties of triazoles, which impart stability to the basic pharmacophoric unit with an added advantage of being a bioisostere of different chemical functionalities. In the last decade, the use of triazoles as bioisosteres and linkers in the development of microtubule targeting agents has been extensively investigated. The present review highlights the advances in this promising area of drug discovery and development.

Ceftolozane-Tazobactam Population Pharmacokinetics and Dose Selection for Further Clinical Evaluation in Pediatric Patients with Complicated Urinary Tract or Complicated Intra-abdominal Infections

Ceftolozane-tazobactam, a combination of the novel antipseudomonal cephalosporin ceftolozane and the well-established extended-spectrum β-lactamase inhibitor tazobactam, is approved for treating complicated urinary tract infections (cUTI) and complicated intra-abdominal infections (cIAI) in adults. To determine doses likely to be safe and efficacious in phase 2 pediatric trials for the same indications, single-dose ceftolozane-tazobactam plasma pharmacokinetic data from a recently completed phase 1 trial in pediatric patients (birth to <18 years old) with proven/suspected Gram-negative bacterial infections, along with pharmacokinetic data from 12 adult studies, were integrated into a population pharmacokinetic (popPK) analysis. Two-compartment linear models with first-order elimination described the concentration-time profiles of ceftolozane and tazobactam in pediatric patients well. Renal function and body weight were identified to be significant predictors of ceftolozane-tazobactam pharmacokinetics. Renal function, as measured by the estimated glomerular filtration rate (eGFR), significantly affected the clearance of both ceftolozane and tazobactam. Body weight significantly affected clearance and the distribution volume, also of both ceftolozane and tazobactam. Patients with infections had a 32.3% lower tazobactam clearance than healthy volunteers. Using the final popPK models, simulations of various dosing regimens were conducted to assess each regimen's plasma exposure and the probability of pharmacokinetic/pharmacodynamic target attainment. Based on these simulations, the following doses are recommended for further clinical evaluation in phase 2 pediatric trials for cUTI and cIAI (in patients with an eGFR of ≥50 ml/min/1.73 m2 only): for children ≥12 years old, 1.5 g ceftolozane-tazobactam (1 g ceftolozane with 0.5 g tazobactam), and for neonates/very young infants, infants, and children <12 years old, 20/10 mg/kg of body weight ceftolozane-tazobactam, both via a 1-h intravenous infusion every 8 h.

New Electrophiles and Strategies for Mechanism-Based and Targeted Covalent Inhibitor Design

Covalent inhibitors are experiencing a growing resurgence in drug design and are an increasingly useful tool in molecular biology. The ability to attach inhibitors to their targets by a covalent linkage offers pharmacodynamic and pharmacokinetic advantages, but this can also be a liability if undesired off-target reactions are not mitigated. The discovery of new electrophilic groups that react selectively with specific amino acid residues is therefore highly desirable in the design of targeted covalent inhibitors (TCIs). Additionally, the ability to control the reactivity through exploitation of the target enzyme's machinery, as in mechanism-based inhibitors (MBIs), greatly benefits from the discovery of new strategies. This Perspective showcases recent advances in electrophile development and their application in TCIs and MBIs, exhibiting high selectivity for their targets.

N-(Sulfamoylbenzoyl)-L-proline Derivatives as Potential Non-β-lactam ESBL Inhibitors: Structure-Based Lead Identification, Medicinal Chemistry and Synergistic Antibacterial Activities

Background:

There is an urgent need to develop novel inhibitors against clinically widespread extended-spectrum β-lactamases (ESBLs) to meet the challenges of the ever-evolving threat of antibiotic resistances. Most existing ESBL inhibitors sharing a common chemical feature of β-lactam ring in their molecule, this structural characteristic makes them intrinsically susceptible to enzymatic breakdown by the resistance mechanisms employed by the bacteria.

Objective:

The aim of this study was to screen and discover novel lead compounds by using Lproline as initial scaffold to create a “non-sulfur, non-β-lactam” new chemotypes for potential ESBL inhibitors.

Methods:

Structure-based molecular docking and virtual screening were employed in the novel inhibitor generation process for lead compound screening and SAR analysis. Evaluation of the ESBL inhibitory activity of the lead compounds was performed in combination with three of the most susceptible antibiotics: ceftazidime, meropenem and ampicillin, against thirteen ESBL enzymes including four new CTX-M harboring strains and four KPC-2 producing species.

Results:

L-proline derived (S)-1-(2-sulfamoylbenzoyl)pyrrolidine-2-carboxylic acid (compound 6) as a “non-sulfur, non-β-lactam” and the most potential ESBL inhibitor was identified. Compound 6 possesses ideal anti-resistance activities by reducing MICs of ceftazidime, meropenem and ampicillin by 16-133, 32-133 and 67-267 fold respectiveily. The inhibitory mechanism of 6 with CTX-M, KPC-2 and penicillinase were proposed and probed with molecular docking analysis.

Conclusion:

Given that the simple proline derivative but promising synergistic antibacterial properties of compound 6 augers well for further investigations into its in vivo efficacy.

Copper fluorapatite assisted synthesis of new 1,2,3-triazoles bearing a benzothiazolyl moiety and their antibacterial and anticancer activities

New 1,2,3-triazoles with a benzothiazolyl scaffold have been synthesized for the first time using copper fluorapatite as a catalyst and their antibacterial and anticancer activities are reported.

Mapping Conformational Dynamics to Individual Steps in the TEM-1 β-Lactamase Catalytic Mechanism

Conformational dynamics are increasingly recognized as being essential for enzyme function. However, there is virtually no direct experimental evidence to support the notion that individual dynamic modes are required for specific catalytic processes, apart from the initial step of substrate binding. In this work, we use a unique approach based on millisecond hydrogen-deuterium exchange mass spectrometry to identify dynamic modes linked to individual catalytic processes in the antibiotic resistance enzyme TEM-1 β-lactamase. Using a "good" substrate (ampicillin), a poorly hydrolyzed substrate (cephalexin) and a covalent inhibitor (clavulanate), we are able to isolate dynamic modes that are specifically linked to substrate binding, productive lactam ring hydrolysis and deacylation. These discoveries are ultimately translated into specific targets for allosteric TEM-1 inhibitor development.

In Silico Fragment-Based Design Identifies Subfamily B1 Metallo-β-lactamase Inhibitors

Zinc ion-dependent β-lactamases (MBLs) catalyze the hydrolysis of almost all β-lactam antibiotics and resist the action of clinically available β-lactamase inhibitors. We report how application of in silico fragment-based molecular design employing thiol-mediated metal anchorage leads to potent MBL inhibitors. The new inhibitors manifest potent inhibition of clinically important B1 subfamily MBLs, including the widespread NDM-1, IMP-1, and VIM-2 enzymes; with lower potency, some of them also inhibit clinically relevant Class A and D serine-β-lactamases. The inhibitors show selectivity for bacterial MBL enzymes compared to that for human MBL fold nucleases. Cocrystallization of one inhibitor, which shows potentiation of Meropenem activity against MBL-expressing Enterobacteriaceae, with VIM-2 reveals an unexpected binding mode, involving interactions with residues from conserved active site bordering loops.

Study of the Cytotoxic and Bactericidal Effects of Sila-substituted Thioalkyne and Mercapto-thione Compounds based on 1,2,3-Triazole Scaffold

A series of sila-organosulphur compounds containing 1,2,3-triazole cores were screened for their cytotoxic activity on human breast cancer cell line MCF-7. Most of the tested compounds exhibited moderate-to-good activity against the cancer cells. Especially, the compound 4-((2-(trimethylsilyl)ethynylthio)methyl)-1-benzyl-1H-1,2,3-triazole (3a) from series of sila-substituted thioalkyne 1,2,3-triazoles (STATs) and the compounds 3-(1-benzyl-1H-1,2,3-triazol-4-yl)-1-mercapto-1,1-bis(trimethylsilyl)propane-2-thione (4a) and 1-mercapto-1,1-bis(trimethylsilyl)-3-(1-phenethyl-1H-1,2,3-triazol-4-yl)propane-2-thione (4e) from series of sila-substituted mercapto-thione 1,2,3-triazoles (SMTTs) exhibited promising cytotoxicity against MCF-7 with IC₅₀ values of 35.17, 32.63 and 30.3 μg/mL, respectively. In addition, the possible mechanisms for inhibition of cell growth and induction of apoptotic cell death were explored by DAPI staining, cell cycle analysis and qRT-PCR. The synthetic compounds were evaluated for their in vitro antibacterial activities, and as a result, the most prominent effects were observed for 3e and 4e. Especially, 3e was found to be quite active against all the tested strains with the MIC values ranging from 15 to 62 μg/mL, except P. aeruginosa. The results of the time-kill assay suggested that the compound of 3e completely inhibited the growth of both gram-negative bacteria, A. baumannii, and gram-positive bacteria, S. aureus. In addition, SEM analysis confirmed morphostructural damage of the bacteria. Our findings could be applicable for developing dual-targeting anticancer/antibacterial therapeutics.

Cyclic Boronates Inhibit All Classes of β-Lactamases

β-Lactamase-mediated resistance is a growing threat to the continued use of β-lactam antibiotics. The use of the β-lactam-based serine-β-lactamase (SBL) inhibitors clavulanic acid, sulbactam, and tazobactam and, more recently, the non-β-lactam inhibitor avibactam has extended the utility of β-lactams against bacterial infections demonstrating resistance via these enzymes. These molecules are, however, ineffective against the metallo-β-lactamases (MBLs), which catalyze their hydrolysis. To date, there are no clinically available metallo-β-lactamase inhibitors. Coproduction of MBLs and SBLs in resistant infections is thus of major clinical concern. The development of “dual-action” inhibitors, targeting both SBLs and MBLs, is of interest, but this is considered difficult to achieve due to the structural and mechanistic differences between the two enzyme classes. We recently reported evidence that cyclic boronates can inhibit both serine- and metallo-β-lactamases. Here we report that cyclic boronates are able to inhibit all four classes of β-lactamase, including the class A extended spectrum β-lactamase CTX-M-15, the class C enzyme AmpC from Pseudomonas aeruginosa, and class D OXA enzymes with carbapenem-hydrolyzing capabilities. We demonstrate that cyclic boronates can potentiate the use of β-lactams against Gram-negative clinical isolates expressing a variety of β-lactamases. Comparison of a crystal structure of a CTX-M-15:cyclic boronate complex with structures of cyclic boronates complexed with other β-lactamases reveals remarkable conservation of the small-molecule binding mode, supporting our proposal that these molecules work by mimicking the common tetrahedral anionic intermediate present in both serine- and metallo-β-lactamase catalysis.

Synthesis, anti-inflammatory, bactericidal activities and docking studies of novel 1,2,3-triazoles derived from ibuprofen using click chemistry

BACKGROUND

Nonsteroidal anti-inflammatory drugs are of vast therapeutic benefit in the treatment of different types of inflammatory conditions. 1,2,3-Triazoles and their derivatives have a wide range of applications as anti-bacterial, anti-fungal, anti-tubercular, cytostatic, anti-HIV, anti-allergic, anti-neoplastic and anti-inflammatory (AI) agents. Considering the individual biological and medicinal importance of ibuprofen and 1,2,3-triazoles, we wanted to explore novel chemical entities based on ibuprofen and triazole moieties towards their biological significance.

RESULTS

Click chemistry has utilized as an ideal strategy to prepare novel ibuprofen-based 1,4-disubstituted 1,2,3-triazole containing molecules. These compounds were screened for their in vivo AI activity, among all the synthesized analogues 13o was shown potent effect than the reference AI drug ibuprofen at the same concentration (10 mg/kg body weight). Compounds 13l, 13g, 13c, 13k, 13i, 13n, 13m and 13j were shown significant AI activity. These triazole analogues were also screened for their bactericidal profile. Compounds 13c, 13i, 13l and 13o exhibited considerable bactericidal activity against gram positive and gram negative strains. In addition to this, molecular docking studies were also carried out into cyclooxygenase-2 active site to predict the affinity and orientation of these novel compounds (13a-q).

CONCLUSIONS

In summary, we have designed and synthesized 1,2,3-triazole analogues of ibuprofen in good yields using Click chemistry approach. AI and bactericidal activities of these compounds were evaluated and shown remarkable results.

Genetic Mechanisms of Antimicrobial Resistance of Acinetobacter baumannii

OBJECTIVE

To summarize published data identifying known genetic mechanisms of antibiotic resistance in Acinetobacter baumannii and the correlating phenotypic expression of antibiotic resistance.

DATA SOURCES

MEDLINE databases (1966-July 15, 2010) were searched to identify original reports of genetic mechanisms of antibiotic resistance in A. baumannii.

DATA SYNTHESIS

Numerous genetic mechanisms of resistance to multiple classes of antibiotics are known to exist in A. baumannii, a gram-negative bacterium increasingly implicated in nosocomial infections. Mechanisms may be constitutive or acquired via plasmids, integrons, and transposons. Methods of resistance include enzymatic modification of antibiotic molecules, modification of antibiotic target sites, expression of efflux pumps, and downregulation of cell membrane porin channel expression. Resistance to β-lactams appears to be primarily caused by β-lactamase production, including extended spectrum β-lactamases (b/aTEM, blaSHV, b/aTX-M,b/aKPC), metallo-β-lactamases (blaMP, blaVIM, bla, SIM), and most commonly, oxacillinases (blaOXA). Antibiotic target site alterations confer resistance to fluoroquinolones (gyrA, parC) and aminoglycosides (arm, rmt), and to a much lesser extent, β-lactams. Efflux pumps (tet, ade, abe) contribute to resistance against β-lactams, tetracyclines, fluoroquinolones, and aminoglycosides. Finally, porin channel deletion (carO, oprD) appears to contribute to β-lactam resistance and may contribute to rarely seen polymyxin resistance. Of note, efflux pumps and porin deletions as solitary mechanisms may not render clinical resistance to A. baumannii.

CONCLUSIONS

A. baumannii possesses copious genetic resistance mechanisms. Knowledge of local genotypes and expressed phenotypes for A. baumannii may aid clinicians more than phenotypic susceptibilities reported in large epidemiologic studies.

Syntheses and studies of new forms of N-sulfonyloxy β-lactams as potential antibacterial agents and β-lactamase inhibitors

The synthesis of a small library of N-sulfonyloxy-2-azetidinones is reported and the preliminary results of the investigation of the biological activity of these molecules are discussed. These new multi-electrophilic β-lactams ('electrophilic bombs') display unexpected selectivity in their antibacterial activity and β-lactamase inhibitory activity.

Ceftolozane/tazobactam: a novel cephalosporin/β-lactamase inhibitor combination with activity against multidrug-resistant gram-negative bacilli

Ceftolozane is a novel cephalosporin currently being developed with the β-lactamase inhibitor tazobactam for the treatment of complicated urinary tract infections (cUTIs), complicated intra-abdominal infections (cIAIs), and ventilator-associated bacterial pneumonia (VABP). The chemical structure of ceftolozane is similar to that of ceftazidime, with the exception of a modified side-chain at the 3-position of the cephem nucleus, which confers potent antipseudomonal activity. As a β-lactam, its mechanism of action is the inhibition of penicillin-binding proteins (PBPs). Ceftolozane displays increased activity against Gram-negative bacilli, including those that harbor classical β-lactamases (e.g., TEM-1 and SHV-1), but, similar to other oxyimino-cephalosporins such as ceftazidime and ceftriaxone, it is compromised by extended-spectrum β-lactamases (ESBLs) and carbapenemases. The addition of tazobactam extends the activity of ceftolozane to include most ESBL producers as well as some anaerobic species. Ceftolozane is distinguished from other cephalosporins by its potent activity versus Pseudomonas aeruginosa, including various drug-resistant phenotypes such as carbapenem, piperacillin/tazobactam, and ceftazidime-resistant isolates, as well as those strains that are multidrug-resistant (MDR). Its antipseudomonal activity is attributed to its ability to evade the multitude of resistance mechanisms employed by P. aeruginosa, including efflux pumps, reduced uptake through porins and modification of PBPs. Ceftolozane demonstrates linear pharmacokinetics unaffected by the coadministration of tazobactam; specifically, it follows a two-compartmental model with linear elimination. Following single doses, ranging from 250 to 2,000 mg, over a 1-h intravenous infusion, ceftolozane displays a mean plasma half-life of 2.3 h (range 1.9-2.6 h), a steady-state volume of distribution that ranges from 13.1 to 17.6 L, and a mean clearance of 102.4 mL/min. It demonstrates low plasma protein binding (20 %), is primarily eliminated via urinary excretion (≥92 %), and may require dose adjustments in patients with a creatinine clearance <50 mL/min. Time-kill experiments and animal infection models have demonstrated that the pharmacokinetic-pharmacodynamic index that is best correlated with ceftolozane's in vivo efficacy is the percentage of time in which free plasma drug concentrations exceed the minimum inhibitory concentration of a given pathogen (%fT >MIC), as expected of β-lactams. Two phase II clinical trials have been conducted to evaluate ceftolozane ± tazobactam in the settings of cUTIs and cIAIs. One trial compared ceftolozane 1,000 mg every 8 h (q8h) versus ceftazidime 1,000 mg q8h in the treatment of cUTI, including pyelonephritis, and demonstrated similar microbiologic and clinical outcomes, as well as a similar incidence of adverse effects after 7-10 days of treatment, respectively. A second trial has been conducted comparing ceftolozane/tazobactam 1,000/500 mg and metronidazole 500 mg q8h versus meropenem 1,000 mg q8h in the treatment of cIAI. A number of phase I and phase II studies have reported ceftolozane to possess a good safety and tolerability profile, one that is consistent with that of other cephalosporins. In conclusion, ceftolozane is a new cephalosporin with activity versus MDR organisms including P. aeruginosa. Tazobactam allows the broadening of the spectrum of ceftolozane versus β-lactamase-producing Gram-negative bacilli including ESBLs. Potential roles for ceftolozane/tazobactam include empiric therapy where infection by a resistant Gram-negative organism (e.g., ESBL) is suspected, or as part of combination therapy (e.g., with metronidazole) where a polymicrobial infection is suspected. In addition, ceftolozane/tazobactam may represent alternative therapy to the third-generation cephalosporins after treatment failure or for documented infections due to Gram-negative bacilli producing ESBLs. Finally, the increased activity of ceftolozane/tazobactam versus P. aeruginosa, including MDR strains, may lead to the treatment of suspected and documented P. aeruginosa infections with this agent. Currently, ceftolozane/tazobactam is being evaluated in three phase III trials for the treatment of cUTI, cIAI, and VABP.

A boronic-acid-based probe for fluorescence polarization assays with penicillin binding proteins and β-lactamases

Penicillin binding proteins (PBPs) and β-lactamases are involved in interactions with β-lactam antibiotics connected with both antibacterial activity and mediation of bacterial β-lactam resistance. Current methods for identifying inhibitors of PBPs and β-lactamases can be inefficient and are often not suitable for studying weakly and/or reversibly binding compounds. Therefore, improved ligand binding assays for PBPs and β-lactamases are needed. We report the development of a fluorescence polarization (FP) assay for PBPs and "serine" β-lactamases using a boronic-acid-based, reversibly binding "tracer." The tracer was designed based on a crystal structure of a covalent complex between a boronic acid and PBP1b from Streptococcus pneumoniae. The tracer bound to three different PBPs with modest affinity (K(d)=4-12 μM) and more tightly to the TEM1 serine β-lactamase (K(d)=109 nM). β-Lactams and other boronic acids were able to displace the tracer in competition assays. These results indicate that fluorescent boronic acids are suited to serve as reversibly binding tracers in FP-based assays with PBPs and β-lactamases and potentially with other related enzymes.

Natural evolution of TEM-1 β-lactamase: experimental reconstruction and clinical relevance

TEM-1 β-lactamase is one of the most well-known antibiotic resistance determinants around. It confers resistance to penicillins and early cephalosporins and has shown an astonishing functional plasticity in response to the introduction of novel drugs derived from these antibiotics. Since its discovery in the 1960s, over 170 variants of TEM-1 - with different amino acid sequences and often resistance phenotypes - have been isolated in hospitals and clinics worldwide. Next to this well-documented 'natural' evolution, the in vitro evolution of TEM-1 has been the focus of attention of many experimental studies. In this review, we compare the natural and laboratory evolution of TEM-1 in order to address the question to what extent the evolution of antibiotic resistance can be repeated, and hence might have been predicted, under laboratory conditions. We also use the comparison to gain an insight into the adaptive relevance of hitherto uncharacterized substitutions present in clinical isolates and to predict substitutions not yet observed in nature. Based on new structural insights, we review what is known about substitutions in TEM-1 that contribute to the extension of its resistance phenotype. Finally, we address the clinical relevance of TEM alleles during the past decade, which has been dominated by the emergence of another β-lactamase, CTX-M.