Discovery and Hit-to-Lead Optimization of Benzothiazole Scaffold-Based DNA Gyrase Inhibitors with Potent Activity against Acinetobacter baumannii and Pseudomonas aeruginosa .

We have developed compounds with a promising activity against and , which are both on the WHO priority list of antibiotic-resistant bacteria. Starting from DNA gyrase inhibitor , we identified compound , featuring a 10-fold improved aqueous solubility, a 10-fold improved inhibition of topoisomerase IV from and , a 10-fold decreased inhibition of human topoisomerase IIα, and no cross-resistance to novobiocin. Cocrystal structures of in complex with GyrB24 and ()- in complex with GyrB23 and GyrB24 revealed their binding to the ATP-binding pocket of the GyrB subunit. In further optimization steps, solubility, plasma free fraction, and other ADME properties of were improved by fine-tuning of lipophilicity. In particular, analogs of with retained anti-Gram-negative activity and improved plasma free fraction were identified. The series was found to be nongenotoxic, nonmutagenic, devoid of mitochondrial toxicity, and possessed no ion channel liabilities.