A Cephalosporin Prochelator Inhibits New Delhi Metallo-β-lactamase 1 without Removing Zinc

Antibacterial drug resistance is a rapidly growing clinical threat, partially due to expression of beta-lactamase enzymes, which confer resistance to bacteria by hydrolyzing and inactivating beta-lactam antibiotics. The increasing prevalence of metallo-beta-lactamases poses a unique challenge, as currently available beta-lactamase inhibitors target the active site of serine beta-lactamases but are ineffective against the zinc-containing active sites of metallo-beta-lactamases. There is an urgent need for metallo-beta-lactamase inhibitors and antibiotics that circumvent resistance mediated by metallo-beta-lactamases in order to extend the utility of existing beta-lactam antibiotics for treating infection. Here we investigated the antibacterial chelator-releasing prodrug PcephPT (2-((((6R,7R)-2-carboxy-8-oxo-7-(2-phenylacetamido)-5-thia-1-azabicyclo [4.2.0]-oct-2-en-3-yl)methyl)thio) pyridine 1-oxide) as an inhibitor of New Delhi metallo-beta-lactamase 1 (NDM-1). PcephPT is an experimental compound that we have previously shown inhibits growth of beta-lactamase-expressing E. coli using a mechanism that is dependent on both copper availability and beta-lactamase expression. Here, we found that PcephPT, in addition to being a copper-dependent antibacterial compound, inhibits hydrolysis activity of purified NDM-1with an IC50 of 7.6 mu M without removing zinc from the active site and restores activity of the carbapenem antibiotic meropenem against NDM-1-producing E. coli. This work demonstrates that targeting a metal-binding pharmacophore to beta-lactamase-producing bacteria is a promising strategy for inhibition of both bacterial growth and metallo-beta-lactamases.