The non-receptor tyrosine kinases c-Src and Abl have important roles in cell signaling and cancer. Bosutinib is best known as a potent dual inhibitor of c-Src and Abl (IC50 = 1.2 and 1.0 nM, respectively). Consistent with this action, bosutinib can be effective in regulating tumor growth and differentiation. Bosutinib is best known as a potent dual inhibitor of c-Src and Abl (IC50 = 1.2 and 1.0 nM, respectively). Consistent with this action, bosutinib can be effective in regulating tumor growth and differentiation. Bosutinib also inhibits, at nanomolar concentrations, other members of the Src family (e.g., Yes, Fgr, Lck, Fyn), as well as members of the TEC family, and certain other kinases. These actions extend the usefulness of this compound to cancers beyond those involving Src and Abl.