A number of inhibitors of Src are now in clinical trials in patients with a range of different tumors. Dasatinib, an oral adenosine triphosphate (ATP)-competitive Src inhibitor, is now approved for clinical use in patients with chronic myeloid leukemia or acute lymphoblastic leukemia. However, dasatinib has wider 'off target' inhibitory activity than saracatinib including potent activity against Abl, ephrin receptor kinases, platelet-derived growth factor receptor and c-KIT (type of receptor tyrosine kinase and a type of tumor marker. Also called CD117 and stem cell factor receptor.) In contrast, saracatinib has a >10-fold preference for Src over Abl kinases and has very little activity against other tyrosine and serine/threonine kinases. Saracatinib has been already characterized in multiple clinical trials in terms of safety and pharmacokinetics.