Molecular Basis of Class A β-Lactamase Inhibition by Relebactam

• Published in: Antimicrobial agents and chemotherapy Vol. 63; no. 10
• Main Authors: Tooke, Catherine L., Hinchliffe, Philip, Lang, Pauline A., Mulholland, Adrian J., Brem, Jürgen, Schofield, Christopher J., Spencer, James
• Format: Journal Article
• Language: English
• Published: United States American Society for Microbiology 01.10.2019
• Subjects: Azabicyclo Compounds; Azabicyclo Compounds - chemistry; Azabicyclo Compounds - metabolism; Azabicyclo Compounds - pharmacology; Aztreonam - chemistry; Aztreonam - metabolism; Aztreonam - pharmacology; beta-Lactam Resistance; beta-Lactam Resistance - genetics; beta-Lactamase Inhibitors; beta-Lactamase Inhibitors - chemistry; beta-Lactamase Inhibitors - metabolism; beta-Lactamase Inhibitors - pharmacology; beta-Lactamases; beta-Lactamases - chemistry; beta-Lactamases - genetics; beta-Lactamases - metabolism; Binding Sites; Ceftazidime - chemistry; Ceftazidime - metabolism; Ceftazidime - pharmacology; Chromosomes, Bacterial - chemistry; Chromosomes, Bacterial - enzymology; Clinical Trials, Phase III as Topic; Cloning, Molecular; Drug Combinations; Escherichia coli - genetics; Escherichia coli - metabolism; Gene Expression; Genetic Vectors - chemistry; Genetic Vectors - metabolism; Humans; Imipenem - chemistry; Imipenem - metabolism; Imipenem - pharmacology; Isoenzymes - antagonists & inhibitors; Isoenzymes - chemistry; Isoenzymes - genetics; Isoenzymes - metabolism; Klebsiella pneumoniae; Klebsiella pneumoniae - drug effects; Klebsiella pneumoniae - enzymology; Klebsiella pneumoniae - genetics; Mechanisms of Resistance; Microbial Sensitivity Tests; Models, Molecular; Plasmids - chemistry; Plasmids - metabolism; Protein Binding; Protein Interaction Domains and Motifs; Recombinant Proteins - chemistry; Recombinant Proteins - genetics; Recombinant Proteins - metabolism; Stenotrophomonas maltophilia; Stenotrophomonas maltophilia - drug effects; Stenotrophomonas maltophilia - enzymology; Stenotrophomonas maltophilia - genetics; relebactam; antibiotic resistance; avibactam; diazabicyclooctane; serine β-lactamase inhibitors
• ISSN: 0066-4804; 1098-6596; 1098-6596
• DOI: 10.1128/AAC.00564-19

β-Lactamase production is the major β-lactam resistance mechanism in Gram-negative bacteria. β-Lactamase inhibitors (BLIs) efficacious against serine β-lactamase (SBL) producers, especially strains carrying the widely disseminated class A enzymes, are required. Relebactam, a diazabicyclooctane (DBO) BLI, is in phase 3 clinical trials in combination with imipenem for the treatment of infections by multidrug-resistant Enterobacteriaceae . β-Lactamase production is the major β-lactam resistance mechanism in Gram-negative bacteria. β-Lactamase inhibitors (BLIs) efficacious against serine β-lactamase (SBL) producers, especially strains carrying the widely disseminated class A enzymes, are required. Relebactam, a diazabicyclooctane (DBO) BLI, is in phase 3 clinical trials in combination with imipenem for the treatment of infections by multidrug-resistant Enterobacteriaceae . We show that relebactam inhibits five clinically important class A SBLs (despite their differing spectra of activity), representing both chromosomal and plasmid-borne enzymes, i.e., the extended-spectrum β-lactamases L2 (inhibition constant 3 μM) and CTX-M-15 (21 μM) and the carbapenemases KPC-2, -3, and -4 (1 to 5 μM). Against purified class A SBLs, relebactam is an inferior inhibitor compared with the clinically approved DBO avibactam (9- to 120-fold differences in half maximal inhibitory concentration [IC 50 ]). MIC assays indicate relebactam potentiates β-lactam (imipenem) activity against KPC-producing Klebsiella pneumoniae , with similar potency to avibactam (with ceftazidime). Relebactam is less effective than avibactam in combination with aztreonam against Stenotrophomonas maltophilia K279a. X-ray crystal structures of relebactam bound to CTX-M-15, L2, KPC-2, KPC-3, and KPC-4 reveal its C2-linked piperidine ring can sterically clash with Asn104 (CTX-M-15) or His/Trp105 (L2 and KPCs), rationalizing its poorer inhibition activity than that of avibactam, which has a smaller C2 carboxyamide group. Mass spectrometry and crystallographic data show slow, pH-dependent relebactam desulfation by KPC-2, -3, and -4. This comprehensive comparison of relebactam binding across five clinically important class A SBLs will inform the design of future DBOs, with the aim of improving clinical efficacy of BLI–β-lactam combinations.