Design, synthesis and biological evaluation of 5H-[1,2,4]triazino[5,6-b]indole derivatives bearing a pyridinocycloalkyl moiety as iron chelators.

The avidity of cancer cells for iron highlights the potential for iron chelators to be used in cancer therapy. Herein, we designed and synthesized a novel series of 5H-[1,2,4]triazino[5,6-b]indole derivatives bearing a pyridinocycloalkyl moiety using a ring-fusion strategy based on the structure of an iron chelator, VLX600. The antiproliferative activity evaluation against cancer cells and normal cells led to the identification of compound 3k, which displayed the strongest antiproliferative activity in vitro against A549, MCF-7, Hela and HepG-2 with IC50 values of 0.59, 0.86, 1.31 and 0.92 µM, respectively, and had lower cytotoxicity against HEK293 than VLX600. Further investigations revealed that unlike VLX600, compound 3k selectively bound to ferrous ions, but not to ferric ions, and addition of Fe2+ abolished the cytotoxicity of 3k. Flow cytometry assays demonstrated that 3k arrested the cell cycle at the G1 phase and induced significant apoptosis in A549 cells in dose and time-dependent manners, corresponding to JC-1 staining assay results. Western blot analysis of Bcl-2, Bax and cleaved caspase-3 proteins further provided evidences that induction of apoptosis by 3k in A549 cells might be at least via the mitochondria pathway. These above results highlight that 3k is a valuable lead compound that deserves further investigation as an iron chelator for the treatment of cancer.

Discovery of quinazoline derivatives as novel small-molecule inhibitors targeting the programmed cell death-1/programmed cell death-ligand 1 (PD-1/PD-L1) interaction.

Development of small molecule PD-1/PD-L1 inhibitors as a novel immunotherapy strategy exhibits great promise. Herein, a novel series of quinazoline derivatives were designed, synthesized and their inhibitory activity against the PD-1/PD-L1 interaction was evaluated through a homogenous time-resolved fluorescence (HTRF) assay. Among them, the compound 39 exhibited the most potent inhibitory activity with an IC50 value of 1.57 nM. Furthermore, the cellular level assays revealed that 39 could inhibit the PD-1/PD-L1 interaction and restore T-cell function, and showed low toxicity on the PBMCs. In addition, the structure-activity relationships (SARs) of the novel quinazoline derivatives were explored and the binding mode of 39 with dimeric PD-L1 was analyzed by molecular docking. This work demonstrates that incorporation of pyrimidine group between the 2 and 3-positions of the biphenyl structure is an effective strategy for designing novel and more potent small molecule PD-1/PD-L1 inhibitors, and 39 can be regarded as a promising lead compound for further investigation.