Discovery of Atirmociclib (PF-07220060): A Potent and Selective CDK4 Inhibitor

Inhibitors of cyclin-dependent kinases 4 and 6 have been shown to be clinically effective for the treatment of hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2-) advanced, or metastatic breast cancer. These agents, however, often show neutropenia, likely due to the role of CDK6 in hematopoiesis. Herein described is the discovery of a series of aminopyrimidine-based selective CDK4 inhibitors. Central to our strategy were efficiency-based optimization (LipE and LipMetE), structure-based drug design, and molecular dynamics simulation. The culmination of these efforts resulted in the discovery of PF-07220060 (atirmociclib), which possessed high potency and levels of selectivity for CDK4 over CDK6 that translated to minimal impact on neutrophils while driving efficacy in a mouse ZR75-1 xenograft model.