4-Oxo-1,4-dihydroquinoline-3-carboxamide Derivatives as New Axl Kinase Inhibitors.

Axl is a new potential target for anticancer drug discovery. A series of 4-oxo-1,4-dihydroquinoline-3-carboxamides were designed and synthesized as highly potent Axl kinase inhibitors. One of the most promising compounds, 9im, tightly bound with Axl protein and potently inhibited its kinase function with a Kd value of 2.7 nM and an IC50 value of 4.0 nM, respectively, while was obviously less potent against most of the 403 wild-type kinases evaluated at a relatively high concentration. The compound dose-dependently inhibited the TGF-β1-induced epithelial-mesenchymal transition (EMT) and suppressed the migration and invasion of MDA-MB-231 breast cancer cells. In addition, 9im also demonstrated reasonable pharmacokinetics properties in rats and exhibited in vivo therapeutic effect on hepatic metastasis in a xenograft model of highly metastatic 4T1 murine breast cancer cells. Compound 9im may serve as a lead compound for new anticancer drug discovery and a valuable research probe for further biological investigation on Axl.