Breast cancer is one of the most common cancer in the world. Abemaciclib (ABE), ribociclib (RIB), and palbociclib (PAL) are CDK4/6 inhibitors that work by targeting overactive CDK4/6 in cancer cells and stopping their cell cycle, thereby slowing proliferation. Advances in the treatment of HR+/HER2- breast cancer phenotype have been made with the introduction of abemaciclib, ribociclib, and palbociclib, inhibitors of cyclin D dependent kinases 4 and 6 (CDK4/6). This service provides a novel, fast, cheap, and green CE method for the simultaneous determination of these three CDK4/6 inhibitors in less than 4 min.