Discovery of Triazolo-pyridazine/-pyrimidine Derivatives Bearing Aromatic (Heterocycle)-Coupled Azole Units as Class II c-Met Inhibitors

[Image: see text] Two series of novel triazolo-pyridazine/-pyrimidine derivatives were designed, synthesized, and evaluated for their inhibitory activity against c-Met kinase, as well as three c-Met overexpressed cancer cell lines (A549, MCF-7, and HeLa) and one normal human hepatocytes cell line LO2 in vitro. The pharmacological data indicated that most of the tested compounds showed moderate cytotoxicity, and the most promising compound 12e exhibited significant cytotoxicity against A549, MCF-7, and HeLa cell lines with IC(50) values of 1.06 ± 0.16, 1.23 ± 0.18, and 2.73 ± 0.33 μM, respectively. Moreover, the inhibitory activity of compound 12e against c-Met kinase (IC(50) = 0.090 μM) was equal to that of Foretinib (IC(50) = 0.019 μM). The result of the acridine orange (AO) single staining test demonstrated that compound 12e could remarkably induce apoptosis of A549 cells. The results of apoptosis and cycle distribution of cells showed that compound 12e could induce late apoptosis of A549 cells and stimulate A549 cells arresting in the G0/G1 phase. Structure–activity relationships (SARs), pharmacological results, and docking studies indicated that the introduction of 5-methylthiazole fragment to the five-atom moiety was beneficial for the activity. So far, the existing data indicated that compound 12e may become a potential class II c-Met inhibitor.