ERBB2 and breast cancer: Different from the other two CDK4/6 inhibitors, abemaciclib has also been approved by FDA as monotherapy for the treatment of adult patients with HR+/HER2- ABC/MBC with disease progression following endocrine therapy and prior chemotherapy (https://www.fda.gov/drugs/resources-information-approved-drugs/fda-approves-abemaciclib-hr-positive-her2-negative-breast-cancer).