APC24-7, a covalent combination of boronic acid and chelator moieties, restores β-lactam efficiency against metallo-β-lactamase-producers.

β-Lactam/β-lactamase inhibitor combinations have significantly improved treatment outcomes for infections caused by serine β-lactamase (SBL)-producing pathogens. However, the continued emergence and spread of metallo-β-lactamases (MBLs), for which no clinically approved inhibitors currently exist, poses a serious threat to the long-term effectiveness of β-lactam-based therapies. To bridge this therapeutic gap, the boronic acid transition state analog, taniborbactam (Venatorx Pharmaceuticals), was developed, targeting SBLs and widespread MBLs such as NDM-1 and VIM-2. However, taniborbactam-escape variants have been detected among various MBL enzymes, including members of the NDM and IMP families. Here, we explored whether covalently combining two complementary inhibitor structures, a boronic acid transition state analog and a dipicolyl ethylenediamine-based metal chelator, can restore β-lactam susceptibility in MBL-producing bacterial strains, including taniborbactam-escape variants. APC24-7 successfully sensitized clinical isolates of SBL- and MBL-producing Klebsiella pneumoniae and Escherichia coli to meropenem. While APC24-7 demonstrated similarities in resensitization behavior to taniborbactam against a wide range of isogenic E. coli expressing single SBLs, APC24-7 reversed NDM-9- or IMP-26-mediated meropenem resistance more efficiently. To investigate the potential role of the chelator motif in the MBL inhibition of APC24-7, susceptibility tests were conducted with an excess of exogenous Zn²+. APC24-7-mediated resensitization remained unaffected in the presence of Zn²+ for strains producing NDM-1 and VIM-2. However, its ability to reverse NDM-9- and IMP-26-mediated meropenem resistance was attenuated upon Zn²+ supplementation. These findings demonstrate that combining functionally complementary chemical structures, such as chelators and boronic acids, can aid in expanding the resensitization ability of existing β-lactamase inhibitors.IMPORTANCEThe ability of bacteria such as Klebsiella pneumoniae and Escherichia coli to circumvent antimicrobial chemotherapy has become a global public health crisis. The high prevalence of β-lactamase enzymes capable of rendering our most prescribed antibiotics, the β-lactams (BLs) inactive, has left us with few available treatment options against infections caused by these bacteria. The use of small molecules that inhibit especially serine β-lactamases has substantially prolonged the lifetime of BL antibiotics. Yet, most clinically available inhibitors either do not possess or have limited ability to reverse resistance conferred by metallo-β-lactamase (MBL) enzymes. Combining chelator and transition state analog technology, our hybrid compound restores the effectiveness of BL antibiotics in cases of resistance conferred by both serine β-lactamases (SBLs) and MBLs. Our approach of covalently combining a chelator with an existing SBL inhibitor scaffold offers a promising solution for managing life-threatening infections and prolonging the use of clinically available BLs.