Dasatinib leukaemia drug binding to its target, the enzyme Bcr_Abl tyrosine kinase. This enzyme is produced by a genetic mutation, the swapping of parts of two chromosomes, leading to the formation of the oncogene cancer_causing gene Bcr_Abl, which produces a constantly_active version of normal Abl tyrosine kinase. This causes chronic myelogenous leukaemia CML, a cancer of white blood cells. The drug Sprycel Dasatinib works by binding to the active site of the Bcr_Abl enzyme, producing a change in shape that prevents the enzyme from functioning. This causes the death of cancerous cells expressing the enzyme. Sprycel is marketed by Bristol_Myers Squibb.