Razbijanje sten: razvoj inhibitorjev D,D- in L,D-transpeptidaz

Antimicrobial resistance is one of the ten greatest global public health challenges, as the number of bacterial infections that can no longer be treated with available chemotherapies is increasing. According to the World Health Organization, if no action is taken, resistant bacteria could cause 10 million deaths annually by 2050. Therefore, the discovery and development of new antibacterial agents is essential. Small companies and, in particular, the academic sector have an important role to play in this effort, as many large pharmaceutical companies have ceased the development of new antibacterial agents.

Infections with resistant Gram-negative (G−) bacteria are particularly difficult to treat due to the impermeability of their outer membrane, which limits antibiotic access. The project therefore focuses on destabilizing the outer membrane and thereby potentiating the activity of standard antibiotics. To this end, two parallel approaches targeting bacterial cell wall biosynthesis will be employed.

In the first approach, new inhibitors of D,D-transpeptidases, also known as penicillin-binding proteins, which are involved in the final steps of peptidoglycan biosynthesis, will be designed and synthesized. Based on experience with monocyclic beta-lactams, new monobactams with a “super side chain” will be developed, substituted with side chains of antibiotics such as meropenem and ceftobiprole. The aim is to achieve high inhibitory potency against D,D-transpeptidases, including those from resistant bacteria, as well as strong antibacterial activity.

In the second approach, specific inhibitors of the L,D-transpeptidases LdtA-C from Escherichia coli will be developed. These enzymes are involved in the attachment of the lipoprotein Lpp to peptidoglycan, thereby providing a covalent connection between the outer membrane and the cell wall. Since they contain a catalytic cysteine, the development of inhibitors will be based on experience with enzymes containing a catalytic cysteine and on fragment-based drug discovery. Following screening of fragment libraries, their binding modes will be determined by X-ray crystallography or NMR. Subsequently, improved compounds will be developed, synthesized, and evaluated using structure-based design.

The new D,D-transpeptidase inhibitors will represent lead compounds with antibacterial activity, while the L,D-transpeptidase inhibitors will act as potentiators by increasing the permeability of the outer membrane of G− bacteria and thereby facilitating the entry of standard antibiotics into bacterial cells. The project thus represents the first attempt to develop and evaluate LdtA-C inhibitors as potentiators.