After exploring the VEGFR-2 inhibitory potency of the library, compound 188f was the most potent inhibitor of VEGFR-2, with an IC50 value of 0.0063 μM; see Scheme 24C. Also, compound 188f demonstrated good cytotoxicity against breast (MCF-7) and colorectal (HCT-116) human cancer cell lines (with IC50 in the range of 7.5 to 8.5 μM), using doxorubicin as the positive control. Here, KDR is linked to cancer.