Design, synthesis, and structure-activity relationships of novel 6,7-disubstituted-4-phenoxyquinoline derivatives as potential antitumor agents.

Two series of quinoline derivatives bearing the pyridine/pyrimidine scaffold were synthesized, and evaluated for their c-Met kinase inhibitory activity and antiproliferative activity against 5 cancer cell lines (HT-29, H460, MKN-45, A549, and U87MG) were evaluated in vitro. Most compounds showed moderate to excellent potency, and compared to foretinib, the most promising analog 18b (c-Met half-maximal inhibitory concentration [IC₅₀] = 1.39 nM) showed a 7.3-fold increase in activity against HT-29 cell line in vitro. Structure-activity relationship studies indicated that regulation of the electron density on the pyridine/pyrimidine ring to a proper degree was a key factor in improving the antitumor activity.