Tozasertib is a potent inhibitor of all aurora kinases, including the A, B and C isotypes (Ki = 0.6 nM, 18 nM and 4.6 nM, respectively).  It also inhibits ABL kinase (Ki = 30 nM), an imatinib-resistant ABL mutant (T315I) kinase (Ki = 42 nM), and Flt-3 (Ki = 30 nM).  Tozasertib binds to an inactive aurora conformation.  Cheetham, G.M., et al.  "Structural basis for potent inhibition of the aurora kinases and a T315I multi-drug resistant mutant form of Abl kinase by VX-680."  Cancer Lett. 251:  323-329 (2007).

1. Okabe S, Tauchi T, Ohyashiki K.Efficacy of MK-0457 and in combination with vorinostat against Philadelphia chromosome positive acute lymphoblastic leukemia cells.Ann Hematol. 2010 Nov;89(11):1081-7. Epub 2010 Jun 20.
2. Li Y, Zhang ZF, Chen J, Huang D, Ding Y, Tan MH, Qian CN, Resau JH, Kim H, Teh BT.VX680/MK-0457, a potent and selective Aurora kinase inhibitor, targets both tumor and endothelial cells in clear cell renal cell carcinoma.Am J Transl Res. 2010 May 20;2(3):296-308.
3.Harrington EA, Bebbington D, Moore J, et al. VX-680, a potent and selective smallmolecule inhibitor of the Aurora kinases, suppresses tumor growth in vivo. Nat Med. 2004; 10:262-7.