XMD8-87 is a potent and selective inhibitor of Ack1 (Activated CDC42 kinase 1, TNK2), a kinase that regulates cellular attachment and migration and whose over-expression correlates with a more invasive phenotype of cancer cells and predisposition of primary tumor cells to metastasis. XMD8-87 had a Kd of 15 nM against ACK1 and was also found to inhibit murine Ba/F3 tumor cells having leukemia-associated TNK2 mutations. It inhibited TNK2 D163E cells with an IC50 value of 38 nM and TNK2 R806Q cells with an IC50 value of 113 nM.