Development of Dihydrothiazepines as Antimicrobial Agents

Antimicrobial resistance is a critical global health issue exacerbated by the rise of multidrug-resistant organisms that highly complicate the treatment of the associated infections. Additionally, substantial economic and scientific challenges hinder the development of new antimicrobial agents. Cylindrical proteases, such as the ClpXP complex, essential for bacterial survival and response to stress, are attractive, yet not fully explored, drug targets. This degradation complex consists of a serine protease subunit, known as ClpP, and an unfoldase chaperone, ClpX, which exhibits ATPase activity. The chaperone component recognizes, unfolds, and transfers target proteins to ClpP for degradation. This protease complex offers promising avenues for developing new anti-virulence or traditional antimicrobial therapies. Here, we detail three projects that explore the use of a novel class of ClpX inhibitors, the dihydrothiazepines, designed to target pathogenic bacteria. First, we present a new library of dihydrothiazepine derivatives that demonstrated significant antichlamydial activity in infected HEp-2 cells. Our most promising derivatives exhibited strong selectivity against pathogenic bacteria with low cytotoxicity, confirming their potential in treating Chlamydia trachomatis infections. Further, we investigated the antimicrobial potential of the dihydrothiazepines against drug-resistant Gram-positive bacteria, particularly MRSA. Our in vitro findings indicate that dihydrothiazepines diminish biofilm formation, and reduce intracellular bacterial burden, while also exhibiting favorable biocompatibility. Finally, we introduce a dual-therapy system that combines a peptide amphiphile (PA) with a dihydrothiazepine designed to broaden the antimicrobial spectrum and circumvent the poor water solubility associated with this class of small molecules. Two strategies were assessed: the Combination strategy, in which peptide amphiphile (PA) nanostructures enhanced membrane permeability allowing the penetration of the small molecule, and the Encapsulation strategy, wherein PA also functioned as a nanocarrier for the hydrophobic dihydrothiazepine. Both strategies showed additive effects, improving therapeutic efficacy and broadening the antimicrobial capabilities of the dihydrothiazepine derivatives. Overall, our results indicate the dihydrothiazepines as a promising drug class for future research to develop new antimicrobial therapies.