FPI-1523, a derivative of Avibactam, is a potent inhibitor of β-lactamase enzymes with Kd values of 4 nM and 34 nM for CTX-M-15 and OXA-48, respectively. It also inhibits PBP2 with an IC50 of 3.2 μM and demonstrates significant antimicrobial activity.

FPI-1523 demonstrates antimicrobial activity by inhibiting both E. coli K12 and its penicillin-binding protein 2 (PBP2), exhibiting a minimum inhibitory concentration (MIC) of 4 μg/mL and an inhibitory concentration 50% (IC 50) of 0.4 μg/mL, respectively[1]. Moreover, it effectively suppresses E. coli BW25113 pGDP-2 transformants, regardless of whether they carry an empty vector or express various β-lactamases, with notably low MIC values ranging from 1-2 μM[1].