FPI-1523 sodium, a derivative of avibactam, is a potent β-lactamase inhibitor with Kd values of 4 nM and 34 nM for CTX-M-15 and OXA-48, respectively. It inhibited PBP2 with an IC50 of 3.2 μM and has a high level of antibacterial and considerable antimicrobial activity.

FPI-1523 sodium effectively inhibits both E. coli K12 and its PBP2, displaying minimum inhibitory concentrations (MIC) and half-maximal inhibitory concentrations (IC50) of 4 μg/mL and 0.4 μg/mL, respectively. Additionally, it demonstrates potent inhibition against E. coli BW25113 pGDP-2 transformants, irrespective of the presence of an empty vector or the expression of various β-lactamases, achieving low MIC values (1-2 μM).[1]