Tyrosine kinases are protein enzymes that have many functions within cells, including cell signaling, growth, and division. Sometimes these enzymes can be overactive, which helps cancer cells survive and multiply. A tyrosine kinase inhibitor (TKI) is a medication given to certain acute myeloid leukemia (AML) patients to block the actions of overactive tyrosine kinases, with the ultimate goal of stopping or slowing cancer cell growth.