RnpA inhibitors as potential antimicrobials to fight antibiotic-resistance: Computational design, synthesis, and biological evaluation

Antibiotic resistance is still one of the major threats worldwide. As reported by the WHO, the resistance of bacteria to most of the antibiotics used in therapy is leading to a post-antibiotic era, in which minor infections can kill again. Among the reasons behind this phenomenon, as over-prescription and misuse of antibiotics, the lack of development of molecules able to interact with novel molecular targets covers a key role. In particular, Methicillin-resistant Staphylococcus aureus is responsible for the nosocomial infections worldwide. The S. aureus protein RnpA has been recently recognized as a potential target for antimicrobials. RnpA is involved in two crucial processes of the bacterium, indeed RnpA alone can degrade mRNA and, moreover, RnpA interact with rnpb, forming RNase P, which is responsible for tRNA maturation. The present work aims at developing a novel computational model, helpful to explore the SAR of RnpA inhibitors, thus understanding which are the crucial moieties of known molecules. Since the actual SAR of known RnpA inhibitors, such as RNPA2000 and JC2, has been scarcely explored, we set up and validated a computational model to evaluate scaffold modifications. We thus synthesize and characterize some promising molecules, which were further biologically evaluated both in vitro and in vivo. In particular, we firstly assessed the in vitro capability of these molecules to affect the two important processes in which RnpA is involved. Secondly, we evaluated the same ability in vivo, using specific cellular assays. Moreover, the antimicrobial activity was evaluated, by determining the Minimum inhibitory concentrations (MICs).