Cephalosporin prodrug inhibitors overcome metallo‐b‐lactamase driven antibiotic resistance

The increasing prevalence of metallo-s-lactamase (MBL) expressing bacteria presents a worrying trend in antibiotic resistance. MBLs rely on active site zinc ions for their hydrolytic activity and the pursuit of MBL-inhibitors has therefore involved the investigation of zinc chelators. To ensure that such chelators specifically target MBLs, we prepared a series of cephalosporin prodrugs of two potent zinc-binders: dipicolinic acid (DPA) and 8-thioquinoline (8-TQ). While both DPA and 8-TQ bind free zinc very tightly (Kd values in the low nM range), the corresponding cephalosporin conjugates do not. The cephalosporin conjugates are efficiently hydrolyzed by MBLs to release DPA or 8-TQ, as confirmed using both NMR and LC-MS studies. Notably, the cephalosporin prodrugs of DPA and 8-TQ show potent inhibitory activity against NDM, VIM, and IMP classes of MBLs and display potent synergy with meropenem against MBL-expressing clinical isolates of K. pneumoniae and E. coli.