Novel photoswitchable agents targeting LecB in Pseudomonas aeruginosa

The global threat of multi-drug resistance (MDR) development among bacteria represents a significant challenge for modern medicine. The continued consumption of antibiotics, together with the genetic variations and exposure to nosocomial infections led to the selection and diffusion of multidrug-resistant bacteria. In recent years, several innovative antimicrobial strategies have emerged, especially focusing on novel targets and approaches involved in biofilm formation mechanisms, since it is proved that bacteria residing in biofilms can exhibit higher levels of resistance than bacteria that are freely present in the environment. Among the emerging strategies to fight MDR, photopharmacology has gained significant attention due to its remarkable ability to precisely modulate the biological activity of compounds. By using light to control biological processes with high spatiotemporal accuracy, this approach represents a promising method. Different microbial species are reported as major responsible for the development and spread of resistance mechanisms. Among these, Pseudomonas aeruginosa (PA) is one of the prominent species, representing a significant health concern, particularly among hospitalized and immunocompromised patients, with the potential to exacerbate their clinical condition or lead to the development of severe diseases. Different potential antibiofilm targets of PA have been identified during last years. The virulence factor LecB, a carbohydrate-binding protein, represent the one of interest in this work, due to its literature-demonstrated role in biofilm formation. The present work describes the design, synthesis and characterization of two novel LecB photoswitchable modulators, GTA and GTB. Following a drug discovery and development workflow, the two hit compounds have been also assessed for their preliminary biological profile. Both molecules have been evaluated for their ability to interact with the LecB protein using the ITC (Isothermal Titration Calorimetry) biophysical assay. While GTA exhibited solubility issues in the interaction assays that require further optimization of the ITC procedure, GTB demonstrated a notable affinity for the target, accompanied by a discernible distinction in interaction between the two isoforms, cis and trans, of the compound. At last, LecB has been co-crystallized with GTB, and the resulting crystals have been subjected to analysis at synchrotron in both its isoforms confirming ITC results and paving the way to expand the library of LecB modulators candidates using a rational approach.