A dual inhibitor of Mps1/TTK and Clk2 (IC50s 5 and 3 nM respectively) selective for Mps1/TTK and Clk2 over a panel of 255 kinases at 3 M inhibit DYRK3 DYRK1A PHKG DYRK1B and Clk1 (IC50s 99 104 136 157 and 300 nM respectively) selectively inhibits the growth of Cal-51 TNBC cell over BT-474 luminal breast cancer cells (IC50s 60 and 6970 nM respectively) reduces tumor volume in a Cal-51 mouse xenograft model at 20 mg/kg