Mps1-IN-5 is a potent and orally active Mps1 inhibitor with an IC 50 value of 29 nM. Mps1-IN-5 induces Apoptosis and cell cycle arrests at G2/M phase. Mps1-IN-5 shows antiproliferative activity and anti-tumor activity. Mps1-IN-5 inhibits phosphorylation of Mps1 and induces DNA damage.