RK-20448 is an ATP-competitive inhibitor of Lck, Src, KDR/VEGF2R and Tie-2 with IC50 values of 0.24, 1.19, 10.74 and 5.85 µM, respectively. RK-20448 also inhibits BLK, Csk, Fyn and Lyn with IC50 values of 0.37, 4.27, 2.03 and 0.43 µM, respectively. RK-20448 is the cis isomer of A-419259 .