Aberrant signaling by activated forms of ALK can be inhibited by tyrosine kinase inhibitors (TKIs). ALK, like other tyrosine kinase receptors, is activated through a series of phosphorylation and conformational changes that move the receptor from the inactive form to the fully activated form. Type II TKIs bind to the inactive form of the receptor at a site adjacent to the ATP-binding cleft, while type I TKIs bind to the active form (reviewed in Roskoski, 2013). Type I inhibitors crizotinib, brigatinib, alectinib, ceritinib and lorlatinib are all approved for treatment of ALK-dependent cancer. Development of resistance to TKIs is not uncommon, however, either through acquisition of secondary mutations or through activation of bypass pathways that remove the dependence on ALK signalign (reviewed in Lovly and Pao, 2012; Lin et al, 2017; Della Corte et al, 2018).