Exploring a novel Class A β‐Lactamase Inhibitor against the Class C β‐Lactamase
            Pseudomonas
            ‐Derived Cephalosporinase (PDC)

ABSTRACT LK-157 is a novel tricyclic carbapenem with potent activity against class A and class C β-lactamases. When tested against the purified TEM-1 and SHV-1 enzymes, LK-157 exhibited 50% inhibitory concentrations (IC50s) in the ranges of the clavulanic acid and tazobactam IC50s (55 nM and 151 nM, respectively). Moreover, LK-157 significantly inhibited AmpC β-lactamase (IC50, 62 nM), as LK-157 was >2,000-fold more potent than clavulanic acid and approximately 28-fold more active than tazobactam. The in vitro activities of LK-157 in combination with amoxicillin, piperacillin, ceftazidime, cefotaxime, ceftriaxone, cefepime, cefpirome, and aztreonam against an array of Ambler class A (TEM-, SHV-, CTX-M-, KPC-, PER-, BRO-, and PC-type)- and class C-producing bacterial strains derived from clinical settings were evaluated in synergism experiments and compared with those of clavulanic acid, tazobactam, and sulbactam. In vitro MICs against ESBL-producing strains (except CTX-M-containing strains) were reduced 2- to >256-fold, and those against AmpC-producing strains were reduced even up to >32-fold. The lowest MICs (≤0.025 to 1.6 μg/ml) were observed for the combination of cefepime and cefpirome with a constant LK-157 concentration of 4 μg/ml, thus raising an interest for further development. LK-157 proved to be a potent β-lactamase inhibitor, combining activity against class A and class C β-lactamases, which is an absolute necessity for use in the clinical setting due to the worldwide increasing prevalence of bacterial strains resistant to β-lactam antibiotics.

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Microbiological characterization of VNRX-5236: a broad spectrum β-lactamase inhibitor for rescue of the orally bioavailable cephalosporin ceftibuten as a carbapenem-sparing agent against strains of Enterobacterales expressing extended spectrum β-lactamases and serine carbapenemases.

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.00552-21 ◽

2021 ◽

Author(s):

Cassandra L. Chatwin ◽

Jodie C. Hamrick ◽

Robert E. L. Trout ◽

Cullen L. Myers ◽

Susan M. Cusick ◽

...

Keyword(s):

Broad Spectrum ◽

Clinical Isolates ◽

Class A ◽

Extended Spectrum ◽

Oral Agents ◽

Class C ◽

Orally Bioavailable ◽

Lactamase Inhibitor

There is an urgent need for oral agents to combat resistant gram-negative pathogens. Here we describe the characterization of VNRX-5236, a broad-spectrum boronic acid β-lactamase inhibitor (BLI) and its orally bioavailable etzadroxil prodrug, VNRX-7145. VNRX-7145 is being developed in combination with ceftibuten, an oral cephalosporin, to combat strains of Enterobacterales expressing extended spectrum β-lactamases (ESBLs) and serine carbapenemases. VNRX-5236 is a reversible covalent inhibitor of serine β-lactamases, with inactivation efficiencies on the order of 104 M−1. sec−1, and prolonged active site residence times (t1/2, 5 to 46 min). The spectrum of inhibition includes Ambler class A ESBLs, class C cephalosporinases, and class A and D carbapenemases (KPC and OXA-48, respectively). Rescue of ceftibuten by VNRX-5236 (fixed at 4 μg/mL) in isogenic strains of E. coli expressing class A, C or D β-lactamases demonstrated an expanded spectrum of activity relative to oral comparators including investigational penems, sulopenem and tebipenem. VNRX-5236 rescued ceftibuten activity in clinical isolates of Enterobacterales expressing ESBLs (MIC90 = 0.25 μg/mL), KPCs (MIC90 = 1 μg/mL), class C cephalosporinases (MIC90 = 1 μg/mL) and OXA-48-type carbapenemases (MIC90 = 1 μg/mL). Frequency of resistance studies demonstrated a low propensity for recovery of resistant variants at 4× the MIC of the ceftibuten/VNRX-5236 combination. In vivo, whereas ceftibuten alone was ineffective (ED50, >128 mg/kg), ceftibuten/VNRX-7145 administered orally protected mice from lethal septicemia caused by K. pneumoniae producing KPC carbapenemase (ED50, 12.9 mg/kg). The data demonstrate potent, broad-spectrum rescue of ceftibuten activity by VNRX-5236 in clinical isolates of cephalosporin-resistant and carbapenem-resistant Enterobacterales.

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Vaborbactam: Spectrum of Beta-Lactamase Inhibition and Impact of Resistance Mechanisms on Activity in Enterobacteriaceae

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.01443-17 ◽

2017 ◽

Vol 61 (11) ◽

Cited By ~ 120

Author(s):

Olga Lomovskaya ◽

Dongxu Sun ◽

Debora Rubio-Aparicio ◽

Kirk Nelson ◽

Ruslan Tsivkovski ◽

...

Keyword(s):

Efflux Pump ◽

Beta Lactamase ◽

Beta Lactam ◽

Content Type ◽

Beta Lactamases ◽

Class A ◽

Class C ◽

The Impact ◽

Isogenic Strains ◽

Lactamase Inhibitor

ABSTRACT Vaborbactam (formerly RPX7009) is a new beta-lactamase inhibitor based on a cyclic boronic acid pharmacophore. The spectrum of beta-lactamase inhibition by vaborbactam and the impact of bacterial efflux and permeability on its activity were determined using a panel of strains with beta-lactamases cloned from various classes and a panel of Klebsiella pneumoniae carbapenemase 3 (KPC-3)-producing isogenic strains with various combinations of efflux and porin mutations. Vaborbactam is a potent inhibitor of class A carbapenemases, such as KPC, as well as an inhibitor of other class A (CTX-M, SHV, TEM) and class C (P99, MIR, FOX) beta-lactamases. Vaborbactam does not inhibit class D or class B carbapenemases. When combined with meropenem, vaborbactam had the highest potency compared to the potencies of vaborbactam in combination with other antibiotics against strains producing the KPC beta-lactamase. Consistent with broad-spectrum beta-lactamase inhibition, vaborbactam reduced the meropenem MICs for engineered isogenic strains of K. pneumoniae with increased meropenem MICs due to a combination of extended-spectrum beta-lactamase production, class C beta-lactamase production, and reduced permeability due to porin mutations. Vaborbactam crosses the outer membrane of K. pneumoniae using both OmpK35 and OmpK36, but OmpK36 is the preferred porin. Efflux by the multidrug resistance efflux pump AcrAB-TolC had a minimal impact on vaborbactam activity. Investigation of the vaborbactam concentration necessary for restoration of meropenem potency showed that vaborbactam at 8 μg/ml results in meropenem MICs of ≤2 μg/ml in the most resistant engineered strains containing multiple mutations. Vaborbactam is a highly active beta-lactamase inhibitor that restores the activity of meropenem and other beta-lactam antibiotics in beta-lactamase-producing bacteria, particularly KPC-producing carbapenem-resistant Enterobacteriaceae.

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In VitroandIn VivoProperties of BAL30376, a β-Lactam and Dual β-Lactamase Inhibitor Combination with Enhanced Activity against Gram-Negative Bacilli That Express Multiple β-Lactamases

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.01370-10 ◽

2011 ◽

Vol 55 (4) ◽

pp. 1510-1519 ◽

Cited By ~ 31

Author(s):

Malcolm G. P. Page ◽

Clothilde Dantier ◽

Eric Desarbre ◽

Bérangère Gaucher ◽

Klaus Gebhardt ◽

...

Keyword(s):

Clavulanic Acid ◽

Stenotrophomonas Maltophilia ◽

Multidrug Resistant ◽

Triple Combination ◽

Class A ◽

Link Type ◽

Class D ◽

Class C ◽

Inhibitor Combination ◽

Lactamase Inhibitor

ABSTRACTBAL30376 is a triple combination comprising a siderophore monobactam,BAL19764; a novel bridged monobactam,BAL29880, which specifically inhibits class C β-lactamases; and clavulanic acid, which inhibits many class A and some class D β-lactamases. The MIC90was ≤4 μg/ml (expressed as the concentration ofBAL19764) for most species of theEnterobacteriaceaefamily, including strains that produced metallo-β-lactamases and were resistant to all of the other β-lactams tested. The MIC90forStenotrophomonas maltophiliawas 2 μg/ml, for multidrug-resistant (MDR)Pseudomonas aeruginosait was 8 μg/ml, and for MDRAcinetobacterandBurkholderiaspp. it was 16 μg/ml. The presence of the class C β-lactamase inhibitorBAL29880contributed significantly to the activity ofBAL30376against strains ofCitrobacter freundii,Enterobacterspecies,Serratia marcescens, andP. aeruginosa. The presence of clavulanic acid contributed significantly to the activity against many strains ofEscherichia coliandKlebsiella pneumoniaethat produced class A extended-spectrum β-lactamases. The activity ofBAL30376against strains with metallo-β-lactamases was largely attributable to the intrinsic stability of the monobactamBAL19764toward these enzymes. Considering its three components,BAL30376was unexpectedly refractory toward the development of stable resistance.

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In Vitro and In Vivo Activities of AM-112, a Novel Oxapenem

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.47.5.1652-1657.2003 ◽

2003 ◽

Vol 47 (5) ◽

pp. 1652-1657 ◽

Cited By ~ 16

Author(s):

Conor E. Jamieson ◽

Peter A. Lambert ◽

Iain N. Simpson

Keyword(s):

Clavulanic Acid ◽

Enterobacter Cloacae ◽

Penicillin Binding Proteins ◽

Class A ◽

Sepsis Model ◽

Class D ◽

Class C ◽

Lactamase Inhibitor

ABSTRACT AM-112 [(1′R,5R,6R)-3-(4-amino-1,1-dimethyl-butyl)-6-(1′-hydroxyethyl)oxapenem-3-carboxylate] is a novel oxapenem compound which possesses potent β-lactamase-inhibitory properties. Fifty-percent inhibitory concentrations (IC50s) of AM-112 for class A enzymes were between 0.16 and 2.24 μM for three enzymes, compared to IC50s of 0.008 to 0.12 μM for clavulanic acid. Against class C and class D enzymes, however, the activity of AM-112 was between 1,000- and 100,000-fold greater than that of clavulanic acid. AM-112 had affinity for the penicillin-binding proteins (PBPs) of Escherichia coli DC0, with PBP2 being inhibited by the lowest concentration of AM-112 tested, 0.1 μg/ml. Ceftazidime was combined with AM-112 at 1:1 and 2:1 ratios in MIC determination studies against a panel of β-lactamase-producing organisms. These studies demonstrated that AM-112 was effective at protecting ceftazidime against extended-spectrum β-lactamase-producing strains and derepressed class C enzyme producers, reducing ceftazidime MICs by 16- and 2,048-fold. Similar results were obtained when AM-112 was combined with ceftriaxone, cefoperazone, or cefepime in a 1:2 ratio. Protection of ceftazidime with AM-112 was maintained against Enterobacter cloacae P99 and Klebsiella pneumoniae SHV-5 in a murine intraperitoneal sepsis model. The 50% effective dose of ceftazidime against E. cloacae P99 and K. pneumoniae SHV-5 was reduced from >100 and 160 mg/kg of body weight to 2 and 33.6 mg/kg, respectively, when it was combined with AM-112 at a 1:1 ratio. AM-112 demonstrates potential as a new β-lactamase inhibitor.

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Avibactam and Class C β-Lactamases: Mechanism of Inhibition, Conservation of the Binding Pocket, and Implications for Resistance

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.03057-14 ◽

2014 ◽

Vol 58 (10) ◽

pp. 5704-5713 ◽

Cited By ~ 103

Author(s):

S. D. Lahiri ◽

M. R. Johnstone ◽

P. L. Ross ◽

R. E. McLaughlin ◽

N. B. Olivier ◽

...

Keyword(s):

Structural Information ◽

Binding Pocket ◽

Multidrug Resistant ◽

Ceftaroline Fosamil ◽

Content Type ◽

Functional Studies ◽

Class A ◽

Wide Range ◽

Class C ◽

Lactamase Inhibitor

ABSTRACTAvibactam is a novel non-β-lactam β-lactamase inhibitor that inhibits a wide range of β-lactamases. These include class A, class C, and some class D enzymes, which erode the activity of β-lactam drugs in multidrug-resistant pathogens likePseudomonas aeruginosaandEnterobacteriaceaespp. Avibactam is currently in clinical development in combination with the β-lactam antibiotics ceftazidime, ceftaroline fosamil, and aztreonam. Avibactam has the potential to be the first β-lactamase inhibitor that might provide activity against class C-mediated resistance, which represents a growing concern in both hospital- and community-acquired infections. Avibactam has an unusual mechanism of action: it is a covalent inhibitor that acts via ring opening, but in contrast to other currently used β-lactamase inhibitors, this reaction is reversible. Here, we present a high-resolution structure of avibactam bound to a class C β-lactamase, AmpC, fromP. aeruginosathat provided insight into the mechanism of both acylation and recyclization in this enzyme class and highlighted the differences observed between class A and class C inhibition. Furthermore, variants resistant to avibactam that identified the residues important for inhibition were isolated. Finally, the structural information was used to predict effective inhibition by sequence analysis and functional studies of class C β-lactamases from a large and diverse set of contemporary clinical isolates (P. aeruginosaand severalEnterobacteriaceaespp.) obtained from recent infections to understand any preexisting variability in the binding pocket that might affect inhibition by avibactam.

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Activity of NXL104 in Combination with β-Lactams against Genetically Characterized Escherichia coli and Klebsiella pneumoniae Isolates Producing Class A Extended-Spectrum β-Lactamases and Class C β-Lactamases

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.01722-10 ◽

2011 ◽

Vol 55 (5) ◽

pp. 2434-2437 ◽

Cited By ~ 65

Author(s):

P. R. S. Lagacé-Wiens ◽

F. Tailor ◽

P. Simner ◽

M. DeCorby ◽

J. A. Karlowsky ◽

...

Keyword(s):

Escherichia Coli ◽

Klebsiella Pneumoniae ◽

The Novel ◽

Content Type ◽

E Coli ◽

Class A ◽

Extended Spectrum ◽

Class C ◽

Lactamase Inhibitor

ABSTRACTThe novel non-β-lactam β-lactamase inhibitor NXL104, in combination with cefepime, ceftazidime, ceftriaxone, amdinocillin, and meropenem, was tested against 190 extended-spectrum β-lactamase (ESBL)-producingEscherichia coliandKlebsiella pneumoniaeisolates, 94 AmpC-hyperproducingE. coliisolates, and 8 AmpC/ESBL-coexpressingE. coliisolates. NXL104 restored 100% susceptibility to the partner cephalosporins for all isolates tested. Amdinocillin and meropenem MICs were modestly improved (2 to 32 times lower) by NXL104. These results suggest that NXL104 may be useful in combination with β-lactams for the treatment of infections caused by ESBL- and AmpC-producingEnterobacteriaceae.

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Structural Insight into Potent Broad-Spectrum Inhibition with Reversible Recyclization Mechanism: Avibactam in Complex with CTX-M-15 and Pseudomonas aeruginosa AmpC β-Lactamases

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.02247-12 ◽

2013 ◽

Vol 57 (6) ◽

pp. 2496-2505 ◽

Cited By ~ 128

Author(s):

Sushmita D. Lahiri ◽

Stefano Mangani ◽

Thomas Durand-Reville ◽

Manuela Benvenuti ◽

Filomena De Luca ◽

...

Keyword(s):

Pseudomonas Aeruginosa ◽

Broad Spectrum ◽

Reversible Inhibitor ◽

Binding Modes ◽

Content Type ◽

Class A ◽

Class C ◽

Insight Into ◽

Lactamase Inhibitor

ABSTRACTAlthough β-lactams have been the most effective class of antibacterial agents used in clinical practice for the past half century, their effectiveness on Gram-negative bacteria has been eroded due to the emergence and spread of β-lactamase enzymes that are not affected by currently marketed β-lactam/β-lactamase inhibitor combinations. Avibactam is a novel, covalent, non-β-lactam β-lactamase inhibitor presently in clinical development in combination with either ceftaroline or ceftazidime.In vitrostudies show that avibactam may restore the broad-spectrum activity of cephalosporins against class A, class C, and some class D β-lactamases. Here we describe the structures of two clinically important β-lactamase enzymes bound to avibactam, the class A CTX-M-15 extended-spectrum β-lactamase and the class CPseudomonas aeruginosaAmpC β-lactamase, which together provide insight into the binding modes for the respective enzyme classes. The structures reveal similar binding modes in both enzymes and thus provide a rationale for the broad-spectrum inhibitory activity of avibactam. Identification of the key residues surrounding the binding pocket allows for a better understanding of the potency of this scaffold. Finally, avibactam has recently been shown to be a reversible inhibitor, and the structures provide insights into the mechanism of avibactam recyclization. Analysis of the ultra-high-resolution CTX-M-15 structure suggests how the deacylation mechanism favors recyclization over hydrolysis.

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Faculty Opinions recommendation of Discovery of a Cyclic Boronic Acid β-Lactamase Inhibitor (RPX7009) with Utility vs Class A Serine Carbapenemases.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.725391898.793505176 ◽

2015 ◽

Author(s):

John Lowe

Keyword(s):

Boronic Acid ◽

Class A ◽

Lactamase Inhibitor

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Some kinematics of halo coronal mass ejections

Open Astronomy ◽

10.1515/astro-2020-0010 ◽

2020 ◽

Vol 29 (1) ◽

pp. 81-88

Author(s):

Virendra Kumar Verma ◽

Nishant Mittal ◽

Ramesh Chandra

Keyword(s):

Coronal Mass Ejections ◽

Solar Flares ◽

Coronal Holes ◽

Geomagnetic Disturbances ◽

Class A ◽

Heliospheric Physics ◽

Class B ◽

The Mean ◽

Class C

AbstractWe present an investigation of halo coronal mass ejections (HCMEs) kinematics and other facts about the HCMEs. The study of HCMEs is very important because HCMEs are regarded as the main causes of heliospheric and geomagnetic disturbances. In this study, we have investigated 313 HCMEs observed during 1996-2012 by LASCO, coronal holes, and solar flares. We find that HCMEs are of two types: accelerated HCMEs and decelerated HCMEs. The mean space speed of HCMEs is 1283 km/s while the mean speed of decelerated HCMEs and accelerated HCMEs is 1349 km/s and 1174 km/s, respectively. The investigation shows that 1 (0.3%) HCME was associated with class A SXR, 14 (4.7%) HCMEs were associated with class B SXR-flares, 87 (29.4%) HCMEs were associated with class C SXR-flares, 125 (42.2%) HCMEs were associated with class M SXR-flares and 69 (23.3%) HCMEs were associated with class X SXR-flares. The speed of HCMEs increases with the importance of solar SXR-flares. The various results obtained in the present analysis are discussed in the light of the existing scenario of heliospheric physics.

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