AAI101, a Novel β-Lactamase Inhibitor: Microbiological and Enzymatic Profiling

Abstract

BackgroundAAI101 is a novel β-lactamase inhibitor (BLI), active against ESBLs and other β-lactamases. AAI101 combined with cefepime (FEP) is in Phase 2 clinical trials. The objective of this study was to determine differences between AAI101 and tazobactam in their inhibition of selected β-lactamases of clinical relevance.MethodsIsogenic E. coli strains expressing single clinically relevant β-lactamases were tested for susceptibility (broth microdilution MIC) to FEP, FEP/AAI101 and piperacillin-tazobactam (P/T). Periplasmic β-lactamase extracts from selected strains then were used to determine IC50s for AAI101 and for tazobactam. β-Lactamases with low IC50s for AAI101 were purified, and steady-state inactivation kinetics determined for AAI101 and for tazobactam.ResultsAAI101 restored activity of FEP against E. coli strains producing defined β-lactamases, and FEP/AAI101 was more potent than P/T (Table).Table. MIC values [mg/L] β-Lactamase FEP FEP/ AAI101 P/T E. coli DH10B (host)≤0.06≤0.064SHV-120.25>256SHV-58≤0.06256SHV-7 (I8F, R43S, G238S, E240K)8≤0.0632SHV-26 (A187T)0.25≤0.06>256SHV-30 (I8F, R43S, G238S)20.1232SHV-102 (G238A)160.12>256SHV-106 (I8F, G238S)4≤0.0616SHV-129 (G238S, E240K, R275L, N276D)16≤0.06128SHV-161 (R43S)0.5≤0.06>256TEM-10 (R164S, E240K)4≤0.064TEM-26 (E104K, R164S)0.5≤0.062TEM-30 (R244S)≤0.06≤0.06256CTX-M-1480.062CTX-M-15320.062KPC-240.12256KPC-34≤0.06256OXA-120.12256OXA-480.120.12256CMY-20.25≤0.064AAI101 had low IC50s (≤0.52 µM) towards periplasmic extracts of class A β-lactamases tested. Linear inhibition of SHV-1 (original spectrum β-lactamase, OSBL) by AAI101 was observed, whereas inhibition of SHV-1 by tazobactam plateaued at lower BLI concentrations. Similar inhibitory patterns were observed for KPC-2, accompanied by a marked increase in potency of AAI101 vs. tazobactam (Figure).Conclusion Addition of AAI101 enhances cefepime activity vs. a selected array of β-lactamases expressed in E. coli in an isogenic Background. The inhibitory kinetics of β-lactamases by AAI101 compared with those of tazobactam indicate different mechanisms of β-lactamase inhibition.Disclosures K. M. Papp-Wallace, Entasis: Grant Investigator, Research grant Allecra: Grant Investigator, Research grant Merck: Grant Investigator, Research grant; Roche: Grant Investigator, Research grant Allergan: Grant Investigator, Research grant M. R. Jacobs, Allecra: Grant Investigator, Research grant Roche: Grant Investigator, Research grant Shionogi: Grant Investigator, Research grant; R. A. Bonomo, Entasis: Grant Investigator, Research grant Allecra: Grant Investigator, Research grant Wockhardt: Grant Investigator, Research grant Merck: Grant Investigator, Research grant Roche: Grant Investigator, Research grant GSK: Grant Investigator, Research grant Allergan: Grant Investigator, Research grant Shionogi: Grant Investigator, Research grant