Discovery and Optimization of a Trichloroacetamidine Scaffold as a Novel Antibacterial against Multidrug-Resistant <i>Staphylococcus aureus</i>

The global spread of multidrug-resistant bacterial strains poses a major threat to public health and underscores the urgent need for new antibacterial chemotypes. We report here the discovery and optimization of a novel scaffold, N-(benzothiazol-2-yl)trichloroacetamidine, with potent activity against multidrug-resistant Staphylococcus aureus. Focused phenotypic screening of 304 N-(azol-2-yl)imidamide derivatives identified N-(benzothiazol-2-yl)trichloroacetamidine as a hit. Subsequent optimization through the synthesis of 55 analogues across five series, combined with SAR studies, yielded four lead compounds, displaying strong Gram-positive selectivity and high potency against clinically isolated S. aureus strains. Toxicity evaluation in human cells confirmed a favorable safety profile, while resistance assays indicated low likelihood of bacterial intrinsic resistance. Pharmacokinetic studies in mice demonstrated that lead compound 18 possesses desirable in vivo properties, including a 3 h half-life, good systemic exposure, and no observable toxicity. Collectively, these findings establish N-(benzothiazol-2-yl)trichloroacetamidines as a promising new class of antibacterial agents for combating multidrug-resistant S. aureus infections.