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Molecular basis of Class A β-lactamase inhibition by relebactam

DOI: 10.1128/AAC.00564-19 DOI Help

Authors: Catherine L. Tooke (University of Bristol) , Philip Hinchliffe (University of Bristol) , Pauline A. Lang (University of Oxford) , Adrian J. Mulholland (University of Bristol) , Jurgen Brem (University of Oxford) , Christopher J. Schofield (University of Oxford) , James Spencer (University of Bristol)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Antimicrobial Agents And Chemotherapy

State: Published (Approved)
Published: August 2019
Diamond Proposal Number(s): 17212

Open Access Open Access

Abstract: 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 treatment of infections by multi-drug 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 - 5 μM). Against purified class A SBLs, relebactam is an inferior inhibitor compared to the clinically approved DBO avibactam, (9 to 120-fold differences in IC50). Minimum inhibitory concentration 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 compared to 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.

Journal Keywords: serine β-lactamase inhibitors; relebactam; avibactam; diazabicyclooctane; antibiotic resistance

Subject Areas: Biology and Bio-materials, Medicine

Instruments: I03-Macromolecular Crystallography , I04-Macromolecular Crystallography , I24-Microfocus Macromolecular Crystallography