Initial approval of dasatinib was based on data from the START (SRC/ABL Tyrosine kinase inhibition Activity: Research Trials of dasatinib) program, a series of multicenter, open-label phase 2 clinical trials in imatinib-resistant or -intolerant patients with CML or Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph+ ALL). Here, ABL1 is linked to acute lymphoblastic leukemia.