Imatinib drug, molecular model. Imatinib is a drug used to treat a variety of cancers, including several types of leukaemia. It is a BCR-ABL inhibitor that works by blocking a tyrosine kinase enzyme. It is used to treat chronic myelogenous leukaemia (CML) and forms of acute lymphoblastic leukaemia (ALL). It is also used for treatment of gastrointestinal stromal tumours (GISTs). It has been approved in the USA since 2001. The molecular formula is: C29.H31.N7.O. Atoms (spheres) are colour-coded: carbon (light grey), hydrogen (white), nitrogen (blue), and oxygen (red).