Design, Synthesis, and Biological Evaluation of 1,3,4-Thiadiazole Derivatives as Novel Potent Peptide Deformylase Inhibitors for Combating Drug-Resistant Gram-Positive and -Negative Bacteria

The prevalence of drug-resistant bacteria is a major challenge throughout the world, especially with respect to Gram-negative bacteria, such as drug-resistant Acinetobacter baumannii, which are regarded as the greatest bacterial threat to human health by the World Health Organization (WHO). In this work, 1,3,4-thiadiazole was introduced into the main skeleton of the classical peptidomimetic peptide deformylase (PDF) inhibitor in pursuit of highly efficient and broad-spectrum bacteriostatic drugs. Upon detailed structure–activity relationship study, PDF inhibitors that possess satisfactory activity against both Gram-positive and Gram-negative bacteria as well as a lower potential for methemoglobin toxicity were screened out. The mechanism of the empowered antibacterial activity against Gram-negative bacteria was also investigated. Finally, for the first time, remarkable protective efficacy against drug-resistant A. baumannii in a mouse model was achieved by a PDF inhibitor (compound 43). These findings can pave a way to new approaches to the development of novel broad-spectrum PDF inhibitors.