PF-7006 is an Mps1 kinase inhibitor with a K i value of 0.27 nM and an IC 50 value of 2.5 nM. PF-7006 interferes with cell cycle checkpoints by inhibiting the catalytic activity of Mps1 , reducing histone H3 levels, and shortening the duration of mitosis, leading to apoptosis in cancer cells. Combined use of PF-7006 with Palbociclib increases cancer cell tolerance to PF-7006. PF-7006 can be used for breast cancer research.