β-lactams are the most frequently used class of antibiotics for the treatment of Gram-negative infections, but the acquisition of metallo-β-lactamases (MBLs) results in the emergence of antibiotic-resistant pathogens. King et al. used a cell-based screen for inhibitors of the MBL NDM1 and found that an extract from Aspergillus versicolor restored the antibiotic activity of meropenem against a genetically engineered NDM1-containing Escherichia coli strain. They identified the fungal peptide aspergillomarasmine A (AMA), which is an inhibitor of metalloproteinases, as the active compound. In vitro assays showed that AMA is a selective inhibitor of the MBLs NDM1 and VIM2 and that it restored meropenem activity against clinically relevant isolates. NDM1-positive Klebsiella pneumoniae were resistant to treatment with meropenem alone, whereas the addition of AMA prevented lethal infection in vivo. Thus, a combination of AMA and β-lactams has therapeutic potential for the treatment of carbapenem-resistant pathogens.