PF-3837 is an Mps1 kinase inhibitor with a K i value of 0.33 nM and an IC 50 value of 5.5 nM. PF-3837 interferes with the cell cycle checkpoint by inhibiting Mps1 catalytic activity, reducing genomic stability, thereby inducing cancer cell apoptosis ( Apoptosis ). PF-3837 can be used in research on breast cancer.