Novel Pyridine Bioisostere of Cabozantinib as a Potent -Met Kinase Inhibitor: Synthesis and Anti-Tumor Activity against Hepatocellular Carcinoma.

Two novel bioisosteres of cabozantinib, and , were designed and synthesized. The benzene ring in the center of the cabozantinib structure was replaced by trimethylpyridine () and pyridine (), respectively. Surprisingly, the two compounds showed extremely contrasting mesenchymal-epithelial transition factor (-Met) inhibitory activities at 1 μM concentration (4% inhibition of vs. 94% inhibition of ). The IC value of compound was 4.9 nM, similar to that of cabozantinib (5.4 nM). A ligand-based docking study suggested that includes the preferred conformation for the binding to -Met in the conformational ensemble, but does not. The anti-proliferative activity of compound against hepatocellular carcinoma (Hep3B and Huh7) and non-small-cell lung cancer (A549 and H1299) cell lines was better than that of cabozantinib, whereas did not show a significant anti-proliferative activity. Moreover, the tumor selectivity of compound toward hepatocellular carcinoma cell lines was higher than that of cabozantinib. In the xenograft tumor model, compound inhibited Hep3B tumor growth to a much greater extent than cabozantinib. The present study suggests that compound may be a good therapeutic candidate against hepatocellular carcinoma.