Repurposed dihydroorotate dehydrogenase inhibitors with efficacy against drug-resistant Acinetobacter baumannii .

New antimicrobials are needed for the treatment of extensively drug-resistant . The de novo pyrimidine biosynthetic enzyme dihydroorotate dehydrogenase (DHODH) is a validated drug target for malaria and human autoimmune diseases. We provide genetic evidence that DHODH (DHODH) is essential for bacterial survival in rodent infection models. We chemically validate the target by repurposing a unique library of ~450 triazolopyrimidine/imidazopyrimidine analogs developed for our malaria DHODH program to identify 21 compounds with submicromolar activity on DHODH. The most potent (DSM186, DHODH IC 28 nM) had a minimal inhibitory concentration of ≤1 µg/ml against geographically diverse strains, including meropenem-resistant isolates. A structurally related analog (DSM161) with a long in vivo half-life conferred significant protection in the neutropenic mouse thigh infection model. Encouragingly, the development of resistance to these compounds was not identified in vitro or in vivo. Lastly, the X-ray structure of DHODH bound to DSM186 was solved to 1.4 Å resolution. These data support the potential of DHODH as a drug target for the development of antimicrobials for the treatment of and potentially other high-risk bacterial infections.