Design, synthesis and biological evaluation of acridone analogues as novel STING receptor agonists.

STING (Stimulator of Interferon Genes) has become a focal point in immunology research and a target in drug discovery. The discovery of a potent human-STING agonist is expected to revolutionize current anti-virus or cancer immunotherapy. Inspired by the structure and function of murine STING-specific agonists (DMXAA and CMA), we rationally designed and synthesized four series of novel compounds for the enhancement of human sensitivity. In the cell-based assay, we identified six compounds from all the synthetic small molecules: 2g, 9g, and 12b are STING agonists that are efficacious across species, and all have the skeleton of acridone; 1b, 1c, and 12c just function in the murine STING pathway. Notably, 12b exhibits the best activity among the six agonists, and its inductions of both human and murine STING-dependent signalling are similar to that of 2'3'-cGAMP, which is a well-known STING inducer. While a protein assay indicated that 2 g, 9 g, and 12b could activate the pathway by directly binding human STING, 12b also displayed the strongest binding affinity. Additionally, our studies show that 12b can induce faster, more powerful, and more durable responses of assorted cytokines in a native system than 2'3'-cGAMP. Consequently, our team is the first to successfully modify murine STING agonists to obtain human sensitivity, and these results suggest that 12b is a potent direct-human-STING agonist. Additionally, the acridone analogues demonstrate tremendous potential in the treatment of tumours or viral infections.

Design, Synthesis and Biological Evaluation of 1-Phenyl-2-(phenylamino) Ethanone Derivatives as Novel MCR-1 Inhibitors.

Polymyxins are considered to be the last-line antibiotics that are used to treat infections caused by multidrug-resistant (MDR) gram-negative bacteria; however, the plasmid-mediated transferable colistin resistance gene (mcr-1) has rendered polymyxins ineffective. Therefore, the protein encoded by mcr-1, MCR-1, could be a target for structure-based design of inhibitors to tackle polymyxins resistance. Here, we identified racemic compound 3 as a potential MCR-1 inhibitor by virtual screening, and 26 compound 3 derivatives were synthesized and evaluated in vitro. In the cell-based assay, compound 6g, 6h, 6i, 6n, 6p, 6q, and 6r displayed more potent activity than compound 3. Notably, 25 µΜ of compound 6p or 6q combined with 2 µg·mL-1 colistin could completely inhibit the growth of BL21(DE3) expressing mcr-1, which exhibited the most potent activity. In the enzymatic assay, we elucidate that 6p and 6q could target the MCR-1 to inhibit the activity of the protein. Additionally, a molecular docking study showed that 6p and 6q could interact with Glu246 and Thr285 via hydrogen bonds and occupy well the cavity of the MCR-1 protein. These results may provide a potential avenue to overcome colistin resistance, and provide some valuable information for further investigation on MCR-1 inhibitors.