VX-680 is an ATP site-targeting potent aurora kinase inhibitor (Aurara A/B/C Ki(app) = 0.6/18/4.6 nM) that affects FLT3, BCR-Abl, BCR-Abl (T315I), Lck, ITK, Src, and Fyn only at higher concentrations (Ki(app) = 30, 30, 42, 80, 220, 350, 520 nM, respectively) and exhibits little inhibitory potency toward 52 other kinases (Ki(app) >1 μM). VX-680 exhibits potent antiproliferation activity in a wide variety of cancer cultures (IC50 from 15 to 113 nM) as a result of cell cycle arrest and apoptosis induction, as well as causes tumor retardation (by 98% on day 13; 75 mg/kg b.i.d i.p.; HL-60 in mice) and regression (2 mg/kg/h 3 d/wk i.v. infusion; HCT116 in rats) in vivo. Crystallography data reveal a tight association of VX-680 with a hydrophobic pocket present only in a closed, inactive kinase conformation, which forms the basis of its selectivity profile, including its activity toward wild-type and the Imatinib-resistant (T315I) Abl.