NCI: A drug used to treat certain types of chronic myelogenous leukemia (CML). It is used in some newly diagnosed patients. It is also used in patients who have not gotten better after treatment with other anticancer drugs or who are not able to take imatinib mesylate. It is also being studied in the treatment of other types of cancer. Nilotinib blocks a protein called BCR-ABL, which may help keep cancer cells from growing. It is a type of tyrosine kinase inhibitor. Also called Tasigna.